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Downey G. Skill building in freediving as an example of embodied culture. Philos Trans R Soc Lond B Biol Sci 2024; 379:20230150. [PMID: 39155712 DOI: 10.1098/rstb.2023.0150] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2023] [Revised: 03/26/2024] [Accepted: 04/02/2024] [Indexed: 08/20/2024] Open
Abstract
Skilled activity is a complex mix of automatized action, changed attention patterns, cognitive strategies and physiological adaptations developed within a community of practice. Drawing on physiological and ethnographic research on freediving, this article argues that skill acquisition demonstrates the variety of mechanisms that link biological and cultural processes to produce culturally shaped forms of embodiment. In particular, apneists alter phenotypic expression through patterned practices that canalize development, exaggerating the dive response, developing resistance to elevated carbon dioxide levels (hypercapnia) and accommodating hydrostatic pressure at depth. The community of divers provides technical advice and helps to orient individuals' motivations. Some biological processes are phenomenologically accessible, but others are sub-aware and must be accessed indirectly through behaviour or altered interactions with the environment. The close analysis of embodied skills like freediving illustrates how phenotypic plasticity is inflected by culturally patterned behaviours. Divers do developmental work on bodily traits like the dive response to achieve more dramatic performance, even if they cannot directly control all elements of the neurological and physiological responses. The example of expert freediving illustrates the imbrication of biology and culture in embodiment. This article is part of the theme issue 'Minds in movement: embodied cognition in the age of artificial intelligence'.
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Affiliation(s)
- Greg Downey
- School of Social Science, Macquarie University , Sydney, New South Wales, Australia
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Declercq L, Bouten J, Van Dyck M, Boone J, Derave W, Heyse B, Bourgois JG. A dive into the physiological responses to maximal apneas, O 2 and CO 2 tables in apnea novices. Eur J Appl Physiol 2024:10.1007/s00421-024-05563-7. [PMID: 39044031 DOI: 10.1007/s00421-024-05563-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2024] [Accepted: 07/09/2024] [Indexed: 07/25/2024]
Abstract
PURPOSE Apnea duration is dependent on three factors: oxygen storage, oxygen consumption, hypoxia and hypercapnia tolerance. While current literature focuses on maximal apneas to improve apnea duration, apnea trained individuals use timed-repeated submaximal apneas, called "O2 and CO2 tables". These tables claim to accommodate the body to cope with hypoxia and hypercapnia, respectively. The aim of this study was twofold. First, to investigate the determinants of maximal apnea duration in apnea novices. Second, to compare physiologic responses to maximal apneas, O2 and CO2 tables. METHODS After medical screening, lung function test and hemoglobin mass measurement, twenty-eight apnea novices performed three apnea protocols in random order: maximal apneas, O2 table and CO2 table. During apnea, peripheral oxygen saturation (SpO2), heart rate (HR), muscle (mTOI) and cerebral (cTOI) tissue oxygenation index were measured continuously. End-tidal carbon dioxide (EtCO2) was measured before and after apneas. RESULTS Larger lung volumes, higher resting cTOI and lower resting EtCO2 levels correlated with longer apnea durations. Maximal apneas induced greater decreases in SpO2 (- 16%) and cTOI (- 13%) than O2 (- 8%; - 8%) and CO2 tables (- 6%; - 6%), whereas changes in EtCO2, HR and mTOI did not differ between protocols. CONCLUSION These results suggest that, in apnea novices, O2 and CO2 tables did not induce a more profound hypoxia and hypercapnia, but a similar reduction in oxygen consumption than maximal apneas. Therefore, apnea novices should mainly focus on maximal apneas to improve hypoxia and hypercapnia tolerance. The use of specific lung training protocols can help to increase oxygen storage capacity.
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Affiliation(s)
- Louise Declercq
- Department of Movement and Sports Sciences, Ghent University, Watersportlaan 2, 9000, Ghent, Belgium
| | - Janne Bouten
- Department of Movement and Sports Sciences, Ghent University, Watersportlaan 2, 9000, Ghent, Belgium
- Laboratory of Sport, Expertise and Performance (EA 7370), French Institute of Sport (INSEP), Paris, France
| | - Matthew Van Dyck
- Department of Movement and Sports Sciences, Ghent University, Watersportlaan 2, 9000, Ghent, Belgium
| | - Jan Boone
- Department of Movement and Sports Sciences, Ghent University, Watersportlaan 2, 9000, Ghent, Belgium
| | - Wim Derave
- Department of Movement and Sports Sciences, Ghent University, Watersportlaan 2, 9000, Ghent, Belgium
| | - Bjorn Heyse
- Department of Anesthesiology, Ghent University Hospital, Corneel Heymanslaan 10, 9000, Ghent, Belgium
| | - Jan G Bourgois
- Department of Movement and Sports Sciences, Ghent University, Watersportlaan 2, 9000, Ghent, Belgium.
- Centre of Sports Medicine, Ghent University Hospital, Corneel Heymanslaan 10, 9000, Ghent, Belgium.
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Nobuhiro N, Heng P, Naoyuki H. The interaction of breath holding and muscle mechanoreflex on cardiovascular responses in breath-hold divers and non-breath-hold divers. Eur J Appl Physiol 2024; 124:2183-2192. [PMID: 38441687 PMCID: PMC11199284 DOI: 10.1007/s00421-024-05431-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2023] [Accepted: 01/30/2024] [Indexed: 06/27/2024]
Abstract
Cardiovascular responses to diving are characterized by two opposing responses: tachycardia resulting from exercise and bradycardia resulting from the apnea. The convergence of bradycardia and tachycardia may determine the cardiovascular responses to diving. The purpose of this study was to investigate the interaction of breath holding and muscle mechanoreflex on cardiovascular responses in breath-hold divers (BHDs) and non-BHDs. We compared the cardiovascular responses to combined apnea and the mechanoreflex in BHDs and non-BHDs. All participants undertook three trials-apnea, passive leg cycling (PLC), and combined trials-for 30 s after rest. Cardiovascular variables were measured continuously. Nine BHD (male:female, 4:5; [means ± SD] age, 35 ± 6 years; height, 168.6 ± 4.6 cm; body mass, 58.4 ± 5.9 kg) and eight non-BHD (male:female, 4:4; [means ± SD] age, 35 ± 7 years; height, 163.9 ± 9.1 cm; body mass, 55.6 ± 7.2 kg) participants were included. Compared to the resting baseline, heart rate (HR) and cardiac output (CO) significantly decreased during the combined trial in the BHD group, while they significantly increased during the combined trials in the non-BHD group (P < 0.05). Changes in the HR and CO were significantly lower in the BHD group than in the non-BHD group in the combined trial (P < 0.05). These results suggest that bradycardia with apnea in BHDs is prioritized over tachycardia with the mechanoreflex, whereas that in non-BHDs is not. This finding implies that diving training changes the interaction between apnea and the mechanoreflex in cardiovascular control.
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Affiliation(s)
- Nakamura Nobuhiro
- Faculty of Sport Sciences, Waseda University, 2-579-15 Mikajima, Tokorozawa, Saitama, 359-1192, Japan
| | - Peng Heng
- Graduate School of Sport Sciences, Waseda University, Tokorozawa, Saitama, Japan
| | - Hayashi Naoyuki
- Faculty of Sport Sciences, Waseda University, 2-579-15 Mikajima, Tokorozawa, Saitama, 359-1192, Japan.
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O'Croinin BR, Young DA, Maier LE, van Diepen S, Day TA, Steinback CD. Influence of hypercapnia and hypercapnic hypoxia on the heart rate response to apnea. Physiol Rep 2024; 12:e16054. [PMID: 38872580 PMCID: PMC11176737 DOI: 10.14814/phy2.16054] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2024] [Revised: 04/30/2024] [Accepted: 04/30/2024] [Indexed: 06/15/2024] Open
Abstract
We aimed to determine the relative contribution of hypercapnia and hypoxia to the bradycardic response to apneas. We hypothesized that apneas with hypercapnia would cause greater bradycardia than normoxia, similar to the response seen with hypoxia, and that apneas with hypercapnic hypoxia would induce greater bradycardia than hypoxia or hypercapnia alone. Twenty-six healthy participants (12 females; 23 ± 2 years; BMI 24 ± 3 kg/m2) underwent three gas challenges: hypercapnia (+5 torr end tidal partial pressure of CO2 [PETCO2]), hypoxia (50 torr end tidal partial pressure of O2 [PETO2]), and hypercapnic hypoxia (combined hypercapnia and hypoxia), with each condition interspersed with normocapnic normoxia. Heart rate and rhythm, blood pressure, PETCO2, PETO2, and oxygen saturation were measured continuously. Hypercapnic hypoxic apneas induced larger bradycardia (-19 ± 16 bpm) than normocapnic normoxic apneas (-11 ± 15 bpm; p = 0.002), but had a comparable response to hypoxic (-19 ± 15 bpm; p = 0.999) and hypercapnic apneas (-14 ± 14 bpm; p = 0.059). Hypercapnic apneas were not different from normocapnic normoxic apneas (p = 0.134). After removal of the normocapnic normoxic heart rate response, the change in heart rate during hypercapnic hypoxia (-11 ± 16 bpm) was similar to the summed change during hypercapnia+hypoxia (-9 ± 10 bpm; p = 0.485). Only hypoxia contributed to this bradycardic response. Under apneic conditions, the cardiac response is driven by hypoxia.
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Affiliation(s)
- Benjamin R O'Croinin
- Neurovascular Health Lab, Faculty of Kinesiology, Sport, and Recreation, University of Alberta, Edmonton, Alberta, Canada
| | - Desmond A Young
- Neurovascular Health Lab, Faculty of Kinesiology, Sport, and Recreation, University of Alberta, Edmonton, Alberta, Canada
| | - Lauren E Maier
- Neurovascular Health Lab, Faculty of Kinesiology, Sport, and Recreation, University of Alberta, Edmonton, Alberta, Canada
| | - Sean van Diepen
- Department of Critical Care Medicine, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
- Division of Cardiology, Department of Medicine, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Trevor A Day
- Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Alberta, Canada
| | - Craig D Steinback
- Neurovascular Health Lab, Faculty of Kinesiology, Sport, and Recreation, University of Alberta, Edmonton, Alberta, Canada
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Drviš I, Vrdoljak D, Dujić G, Dujić Ž, Foretić N. Construction and Validation of Newly Adapted Sport-Specific Anaerobic Diving Tests. Sports (Basel) 2024; 12:110. [PMID: 38668578 PMCID: PMC11053401 DOI: 10.3390/sports12040110] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2024] [Revised: 04/05/2024] [Accepted: 04/15/2024] [Indexed: 04/29/2024] Open
Abstract
Breath-hold diving is explained as an activity that requires enduring muscle asphyxia and acidosis, high anaerobic capacity, and the tactic of the dive. Therefore, this study aimed to construct and validate tests that will mimic anaerobic processes in the specific media of freedivers. The sample of participants included 34 Croatian freedivers (average age: 26.85 ± 4.0 years, competitive age: 3.82 ± 1.92 years, their body height: 180.14 ± 8.93 cm, and their body mass: 76.82 ± 12.41 kg). The sample of variables consists of anthropometric indices, competitive efficiency (maximal length of a dive (DYN)), and specific anaerobic capacities (100 m and 2 min tests). Newly developed tests included the swimming anaerobic sprint test (SAST) and diving anaerobic sprint test (DAST). DAST and SAST variables included the total time of the test (DAST/SAST) and the fastest interval (DASTmax/SASTmax). The results showed good reliability of the tests with high Cronbach alpha coefficients (DAST: 0.98, DASTmax: 0.97, SAST: 0.99, SASTmax: 0.91). Furthermore, pragmatic validity shows a high correlation among all variables and DAST (DYN: -0.70, 100 m: 0.66, 2 min: -0.68). High relation is also found between 100 m (0.96), 2 min (-0.94), and a moderate result for DYN (-0.43) and the SAST test. A factor analysis extracted one significant factor. The factor analysis involved DAST, SAST, DYN, 100 m, and 2 min tests regarding factor 1. After the examination of all variables, the total time of the DAST test showed the best predictive values for the performance of divers. However, both tests could be used for diagnostics and the evaluation of specific condition abilities in freediving.
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Affiliation(s)
- Ivan Drviš
- Faculty of Kinesiology, University of Zagreb, 10000 Zagreb, Croatia;
| | - Dario Vrdoljak
- Faculty of Kinesiology, University of Split, 21000 Split, Croatia;
| | - Goran Dujić
- Clinical Department of Diagnostic and Interventional Radiology, University Hospital of Split, 21000 Split, Croatia;
| | - Željko Dujić
- Department of Integrative Physiology, School of Medicine, University of Split, 21000 Split, Croatia;
| | - Nikola Foretić
- Faculty of Kinesiology, University of Split, 21000 Split, Croatia;
- High Performance Sport Center, Croatian Olympic Committee, 10000 Zagreb, Croatia
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Vezzoli A, Mrakic-Sposta S, Brizzolari A, Balestra C, Camporesi EM, Bosco G. Oxy-Inflammation in Humans during Underwater Activities. Int J Mol Sci 2024; 25:3060. [PMID: 38474303 DOI: 10.3390/ijms25053060] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2024] [Revised: 02/22/2024] [Accepted: 03/01/2024] [Indexed: 03/14/2024] Open
Abstract
Underwater activities are characterized by an imbalance between reactive oxygen/nitrogen species (RONS) and antioxidant mechanisms, which can be associated with an inflammatory response, depending on O2 availability. This review explores the oxidative stress mechanisms and related inflammation status (Oxy-Inflammation) in underwater activities such as breath-hold (BH) diving, Self-Contained Underwater Breathing Apparatus (SCUBA) and Closed-Circuit Rebreather (CCR) diving, and saturation diving. Divers are exposed to hypoxic and hyperoxic conditions, amplified by environmental conditions, hyperbaric pressure, cold water, different types of breathing gases, and air/non-air mixtures. The "diving response", including physiological adaptation, cardiovascular stress, increased arterial blood pressure, peripheral vasoconstriction, altered blood gas values, and risk of bubble formation during decompression, are reported.
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Affiliation(s)
- Alessandra Vezzoli
- Institute of Clinical Physiology-National Research Council (CNR-IFC), 20142 Milano, Italy
- Department of Biomedical Sciences, University of Padova, 35131 Padova, Italy
| | - Simona Mrakic-Sposta
- Institute of Clinical Physiology-National Research Council (CNR-IFC), 20142 Milano, Italy
| | - Andrea Brizzolari
- Department of Biomedical Sciences, University of Padova, 35131 Padova, Italy
| | - Costantino Balestra
- Environmental, Occupational, Aging (Integrative) Physiology Laboratory, Haute Ecole Bruxelles-Brabant (HE2B), 1160 Brussels, Belgium
- Physical Activity Teaching Unit, Motor Sciences Department, Université Libre de Bruxelles (ULB), 1050 Brussels, Belgium
- DAN Europe Research Division (Roseto-Brussels), 1160 Brussels, Belgium
| | | | - Gerardo Bosco
- Department of Biomedical Sciences, University of Padova, 35131 Padova, Italy
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Andrade DC, Arce‐Álvarez A, Salazar‐Ardiles C, Toledo C, Guerrero‐Henriquez J, Alvarez C, Vasquez‐Muñoz M, Izquierdo M, Millet GP. Hypoxic peripheral chemoreflex stimulation-dependent cardiorespiratory coupling is decreased in swimmer athletes. Physiol Rep 2024; 12:e15890. [PMID: 38195247 PMCID: PMC10776339 DOI: 10.14814/phy2.15890] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2023] [Revised: 11/07/2023] [Accepted: 11/21/2023] [Indexed: 01/11/2024] Open
Abstract
Swimmer athletes showed a decreased ventilatory response and reduced sympathetic activation during peripheral hypoxic chemoreflex stimulation. Based on these observations, we hypothesized that swimmers develop a diminished cardiorespiratory coupling due to their decreased hypoxic peripheral response. To resolve this hypothesis, we conducted a study using coherence time-varying analysis to assess the cardiorespiratory coupling in swimmer athletes. We recruited 12 trained swimmers and 12 control subjects for our research. We employed wavelet time-varying spectral coherence analysis to examine the relationship between the respiratory frequency (Rf ) and the heart rate (HR) time series during normoxia and acute chemoreflex activation induced by five consecutive inhalations of 100% N2 . Comparing swimmers to control subjects, we observed a significant reduction in the hypoxic ventilatory responses to N2 in swimmers (0.012 ± 0.001 vs. 0.015 ± 0.001 ΔVE /ΔVO2 , and 0.365 ± 0.266 vs. 1.430 ± 0.961 ΔVE /ΔVCO2 /ΔSpO2 , both p < 0.001, swimmers vs. control, respectively). Furthermore, the coherence at the LF cutoff during hypoxia was significantly lower in swimmers compared to control subjects (20.118 ± 3.502 vs. 24.935 ± 3.832 area under curve [AUC], p < 0.012, respectively). Our findings strongly indicate that due to their diminished chemoreflex control, swimmers exhibited a substantial decrease in cardiorespiratory coupling during hypoxic stimulation.
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Affiliation(s)
- David C. Andrade
- Exercise Applied Physiology Laboratory, Centro de Investigación en Fisiología y Medicina de Altura (FIMEDALT), Departamento Biomedico, Facultad de Ciencias de la SaludUniversidad de AntofagastaAntofagastaChile
| | - Alexis Arce‐Álvarez
- Escuela de Kinesiología, Facultad de Odontología y Ciencias de la RehabilitaciónUniversidad San SebastiánSantiagoChile
| | - Camila Salazar‐Ardiles
- Exercise Applied Physiology Laboratory, Centro de Investigación en Fisiología y Medicina de Altura (FIMEDALT), Departamento Biomedico, Facultad de Ciencias de la SaludUniversidad de AntofagastaAntofagastaChile
- NavarrabiomedHospital Universitario de Navarra (UHN), Universidad Pública de Navarra (UPNA), IdiSNAPamplonaNavarraSpain
| | - Camilo Toledo
- Laboratory of Cardiorespiratory and Sleep Physiology. Institute of Physiology. Faculty of MedicineUniversidad Austral de ChileValdiviaChile
| | - Juan Guerrero‐Henriquez
- Centro de Investigación en Fisiología y Medicina de Altura (FIMEDALT), Departamento de Ciencias de la Rehabilitación y el Movimiento Humano, Facultad de Ciencias de la SaludUniversidad de AntofagastaAntofagastaChile
| | - Cristian Alvarez
- Exercise and Rehabilitation Sciences Institute, School of Physical Therapy, Faculty of Rehabilitation SciencesUniversidad Andres BelloSantiagoChile
| | - Manuel Vasquez‐Muñoz
- Dirección de Docencia de Especialidades Médicas, Dirección de Postgrado, Facultad de Medicina y Ciencias de la SaludUniversidad MayorSantiagoChile
| | - Mikel Izquierdo
- NavarrabiomedHospital Universitario de Navarra (UHN), Universidad Pública de Navarra (UPNA), IdiSNAPamplonaNavarraSpain
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Vrdoljak D, Foretić N, Drviš I, Ivančev V, Perić M, Dujić Ž. Do freedivers and spearfishermen differ in local muscle oxygen saturation and anaerobic power? J Sports Med Phys Fitness 2024; 64:21-29. [PMID: 37902796 DOI: 10.23736/s0022-4707.23.15185-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2023]
Abstract
BACKGROUND Freediving is defined as an activity where athletes repetitively dive and are exposed to long efforts with limited oxygen consumption. Therefore, anaerobic features are expected to be an important facet of diving performance. This study aimed to investigate differences in anaerobic capacity and local muscle oxygenation in spearfisherman and freedivers. METHODS The sample of participants included 17 male athletes (nine freedivers, and eight spearfishermen), with an average age of 37.0±8.8 years, training experience of 10.6±9.5 years, body mass of 82.5±9.5 kg and height of 184.2±5.7 cm. Anthropometric characteristics included: body mass, body height, seated height, and body fat percentage. Wingate anaerobic test was conducted, during which local muscle oxygenation was measured with a NIRS device (Moxy monitor). Wingate power outputs were measured (peak power [W/kg] and average power [W/kg]), together with muscle oxygenation variables (baseline oxygen saturation [%], desaturation slope [%/s], minimum oxygen saturation [%], half time recovery [s], and maximum oxygen saturation [%]). RESULTS The differences were not obtained between freedivers and spearfisherman in power outputs (peak power (9.24±2.08 spearfisherman; 10.68±1.04 freedivers; P=0.14); average power (6.85±0.95 spearfisherman; 7.44±0.60 freedivers; P=0.15) and muscle oxygenation parameters. However, analysis of effect size showed a moderate effect in training experience (0.71), PP (0.89), AP (0.75), Desat slope mVLR (0.66), half time recovery mVLR (0.90). CONCLUSIONS The non-existence of differences between freedivers and spearfishermen indicates similar training adaptations to the anaerobic demands. However, the results show relatively low anaerobic capacities of our divers that could serve as an incentive for the further development of these mechanisms.
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Affiliation(s)
- Dario Vrdoljak
- Faculty of Kinesiology, University of Split, Split, Croatia -
| | - Nikola Foretić
- Faculty of Kinesiology, University of Split, Split, Croatia
- High Performance Sport Center, Croatian Olympic Committee, Zagreb, Croatia
| | - Ivan Drviš
- Faculty of Kinesiology, University of Zagreb, Zagreb, Croatia
| | | | - Mia Perić
- Faculty of Kinesiology, University of Split, Split, Croatia
| | - Željko Dujić
- School of Medicine, University of Split, Split, Croatia
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Bourdas DI, Geladas ND. Physiological responses during static apnoea efforts in elite and novice breath-hold divers before and after two weeks of dry apnoea training. Respir Physiol Neurobiol 2024; 319:104168. [PMID: 37797907 DOI: 10.1016/j.resp.2023.104168] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2023] [Revised: 09/30/2023] [Accepted: 10/01/2023] [Indexed: 10/07/2023]
Abstract
This study examined the effect of breath-hold (BH) training on apnoeic performance in novice BH divers (NBH:n = 10) and compared them with data from elite BH divers (EBH:n = 11). Both groups performed 5-maximal BHs (PRE). The NBH group repeated this protocol after two weeks of BH training (POST). The NBH group during BH efforts significantly increased red blood cell concentration (4.56 ± 0.16Mio/μl) by 5.06%, hemoglobin oxygen saturation steady state duration (110.32 ± 29.84 s) by 15.48%, and breath-hold time (BHT:144.19 ± 47.35 s) by 33.77%, primarily due to a 59.70% increase in struggle phase (71.85 ± 30.89 s), in POST. EBH group exhibited longer BHT (283.95 ± 36.93 s) and struggle-phase (150.10 ± 34.69 s) than NBH (POST). Elite divers recorded a higher peak MAP (153.18 ± 12.28 mmHg) compared to novices (PRE:123.70 ± 15.65 mmHg, POST:128.30 ± 19.16 mmHg), suggesting that a higher peak MAP is associated with a better BHT. The concurrent abrupt increase of diaphragmatic activity and MAP, seen only in the EBH group, suggests a potential interaction. Additionally, apnoea training increases red blood cells concentration in repeated apnoea efforts and increases BH stamina.
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Affiliation(s)
- Dimitrios I Bourdas
- Section of Sport Medicine & Biology of Exercise, School of Physical Education and Sports Science, National and Kapodistrian University of Athens, Ethnikis Antistasis 41, 17237 Daphni, Greece.
| | - Nickos D Geladas
- Section of Sport Medicine & Biology of Exercise, School of Physical Education and Sports Science, National and Kapodistrian University of Athens, Ethnikis Antistasis 41, 17237 Daphni, Greece
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Abstract
Pulmonary physiology is significantly altered during underwater exposure, as immersion of the body and increased ambient pressure elicit profound effects on both the cardiovascular and respiratory systems. Thoracic blood pooling, increased breathing gas pressures, and variations in gas volumes alongside ambient pressure changes put the heart and lungs under stress. Normal physiologic function and fitness of the cardiovascular and respiratory systems are prerequisites to safely cope with the challenges of the underwater environment when freediving, or diving with underwater breathing apparatus. Few physicians are trained to understand the physiology and medicine of diving and how to recognize or manage diving injuries. This article provides an overview of the physiologic challenges to the respiratory system during diving, with or without breathing apparatus, and outlines possible health risks and hazards unique to the underwater environment. The underlying pathologic mechanisms of dive-related injuries are reviewed, with an emphasis on pulmonary physiology and pathophysiology.
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Affiliation(s)
- Kay Tetzlaff
- Department of Sports Medicine, University Hospital of Tuebingen, Tuebingen, Germany
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Östenson B, Ostenfeld E, Edlund J, Heiberg E, Arheden H, Steding-Ehrenborg K. Endurance-trained subjects and sedentary controls increase ventricular contractility and efficiency during exercise: Feasibility of hemodynamics assessed by non-invasive pressure-volume loops. PLoS One 2023; 18:e0285592. [PMID: 37163493 PMCID: PMC10171617 DOI: 10.1371/journal.pone.0285592] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Accepted: 04/27/2023] [Indexed: 05/12/2023] Open
Abstract
INTRODUCTION Pressure-volume (PV) loops can be used to assess both load-dependent and load-independent measures of cardiac hemodynamics. However, analysis of PV loops during exercise is challenging as it requires invasive measures. Using a novel method, it has been shown that left ventricular (LV) PV loops at rest can be obtained non-invasively from cardiac magnetic resonance imaging (CMR) and brachial pressures. Therefore, the aim of this study was to assess if LV PV loops can be obtained non-invasively from CMR during exercise to assess cardiac hemodynamics. METHODS Thirteen endurance trained (ET; median 48 years [IQR 34-60]) and ten age and sex matched sedentary controls (SC; 43 years [27-57]) were included. CMR images were acquired at rest and during moderate intensity supine exercise defined as 60% of expected maximal heart rate. Brachial pressures were obtained in conjunction with image acquisition. RESULTS Contractility measured as maximal ventricular elastance (Emax) increased in both groups during exercise (ET: 1.0 mmHg/ml [0.9-1.1] to 1.1 mmHg/ml [0.9-1.2], p<0.01; SC: 1.1 mmHg/ml [0.9-1.2] to 1.2 mmHg/ml [1.0-1.3], p<0.01). Ventricular efficiency (VE) increased in ET from 70% [66-73] at rest to 78% [75-80] (p<0.01) during exercise and in SC from 68% [63-72] to 75% [73-78] (p<0.01). Arterial elastance (EA) decreased in both groups (ET: 0.8 mmHg/ml [0.7-0.9] to 0.7 mmHg/ml [0.7-0.9], p<0.05; SC: 1.0 mmHg/ml [0.9-1.2] to 0.9 mmHg/ml [0.8-1.0], p<0.05). Ventricular-arterial coupling (EA/Emax) also decreased in both groups (ET: 0.9 [0.8-1.0] to 0.7 [0.6-0.8], p<0.01; SC: 1.0 [0.9-1.1] to 0.7 [0.7-0.8], p<0.01). CONCLUSIONS This study demonstrates for the first time that LV PV loops can be generated non-invasively during exercise using CMR. ET and SC increase ventricular efficiency and contractility and decrease afterload and ventricular-arterial coupling during moderate supine exercise. These results confirm known physiology. Therefore, this novel method is applicable to be used during exercise in different cardiac disease states, which has not been possible non-invasively before.
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Affiliation(s)
- Björn Östenson
- Clinical Physiology, Department of Clinical Sciences Lund, Lund University, Skåne University Hospital, Lund, Sweden
| | - Ellen Ostenfeld
- Clinical Physiology, Department of Clinical Sciences Lund, Lund University, Skåne University Hospital, Lund, Sweden
| | - Jonathan Edlund
- Clinical Physiology, Department of Clinical Sciences Lund, Lund University, Skåne University Hospital, Lund, Sweden
| | - Einar Heiberg
- Clinical Physiology, Department of Clinical Sciences Lund, Lund University, Skåne University Hospital, Lund, Sweden
- Wallenberg Centre for Molecular Medicine, Lund University, Lund, Sweden
| | - Håkan Arheden
- Clinical Physiology, Department of Clinical Sciences Lund, Lund University, Skåne University Hospital, Lund, Sweden
| | - Katarina Steding-Ehrenborg
- Clinical Physiology, Department of Clinical Sciences Lund, Lund University, Skåne University Hospital, Lund, Sweden
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12
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Burley MJ, Blackwell J, Bond B, Williams C, Stephens FB. The effect of various breath-hold techniques on the cardiorespiratory response to facial immersion in humans. Exp Physiol 2023; 108:50-62. [PMID: 36448400 PMCID: PMC10103768 DOI: 10.1113/ep090531] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2022] [Accepted: 11/07/2022] [Indexed: 12/03/2022]
Abstract
NEW FINDINGS What is the central question of this study? What is the effect of three repeated breath-hold techniques routinely used by freedivers, thought to manipulate arterial partial pressures of O2 and CO2 , on the cardiorespiratory and haematological response to breath-holding during facial immersion? What is the main finding and its importance? All three techniques increased breath-hold by a similar duration, probably owing to the similar marked increase in end-tidal O2 and decrease in end-tidal CO2 observed in all three trials before facial immersion. These were the only cardiorespiratory changes that were consistently manipulated before the maximal breath-hold. This would suggest that pronounced bradycardia and vasoconstriction of selective vascular beds are probably not obligatory for prolonging breath-hold duration. ABSTRACT Repeated maximal breath-holds have been demonstrated to induce bradycardia, increase haematocrit and haemoglobin and prolong subsequent breath-hold duration by 20%. Freedivers use non-maximal breath-hold techniques (BHTs) to improve breath-hold duration. The aim of this study was to investigate the cardiorespiratory and haematological responses to various BHTs. Ten healthy men (34.5 ± 1.9 years) attended five randomized experimental trials and performed a 40 min period of quiet rest or one of three BHTs followed by a maximal breath-hold challenge during facial immersion in water at 30 or 10°C. Cardiovascular and respiratory parameters were measured continuously using finger plethysmography and breath-by-breath gas analysis, respectively, and venous blood samples were collected throughout. Facial immersion in cold water caused marked bradycardia (74.1 vs. 50.2 beats/min after 40 s) but did not increase breath-hold duration compared with warm water control conditions. Facial immersion breath-hold duration was 30.8-43.3% greater than the control duration when preceded by BHTs that involved repeated breath-holds of constant duration (P = 0.021), increasing duration (P < 0.001) or increasing frequency (P < 0.001), with no difference observed between BHTs. The increased duration of apnoea across all three BHT protocols was associated with a 6.8% increase in end-tidal O2 and a 13.1% decrease in end-tidal CO2 immediately before facial immersion. There were no differences in blood pressure, cardiac output, heart rate, haematocrit or haemoglobin between each BHT and control conditions (P > 0.05). In conclusion, the duration of apnoea can be extended by manipulating blood gases through repeated prior breath-holds, but changes in cardiac output and red blood cell mass do not appear essential.
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Affiliation(s)
- Matthew J. Burley
- Department of Sport and Health SciencesCollege of Life and Environmental SciencesUniversity of ExeterExeterUK
| | - Jamie Blackwell
- Department of Sport and Health SciencesCollege of Life and Environmental SciencesUniversity of ExeterExeterUK
| | - Bert Bond
- Department of Sport and Health SciencesCollege of Life and Environmental SciencesUniversity of ExeterExeterUK
| | - Craig Williams
- Department of Sport and Health SciencesCollege of Life and Environmental SciencesUniversity of ExeterExeterUK
| | - Francis B. Stephens
- Department of Sport and Health SciencesCollege of Life and Environmental SciencesUniversity of ExeterExeterUK
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13
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Cialoni D, Brizzolari A, Sponsiello N, Lancellotti V, Bosco G, Marroni A, Barassi A. Serum Amino Acid Profile Changes After Repetitive Breath-Hold Dives: A Preliminary Study. SPORTS MEDICINE - OPEN 2022; 8:80. [PMID: 35723766 PMCID: PMC9209628 DOI: 10.1186/s40798-022-00474-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Accepted: 06/06/2022] [Indexed: 12/04/2022]
Abstract
Background The aim of this work was to investigate the serum amino acid (AA) changes after a breath-hold diving (BH-diving) training session under several aspects including energy need, fatigue tolerance, nitric oxide (NO) production, antioxidant synthesis and hypoxia adaptation. Twelve trained BH-divers were investigated during an open sea training session and sampled for blood 30 min before the training session, 30 min and 4 h after the training session. Serum samples were assayed for AA changes related to energy request (alanine, histidine, isoleucine, leucine, lysine, methionine, proline threonine, valine), fatigue tolerance (ornithine, phenylalanine, tyrosine), nitric oxide production (citrulline), antioxidant synthesis (cystine, glutamate, glycine) and hypoxia adaptation (serine, taurine). Main results Concerning the AA used as an energy support during physical effort, we found statistically significant decreases for all the investigated AA at T1 and a gradual return to the basal value at T2 even if alanine, proline and theonine still showed a slight significant reduction at this time. Also, the changes related to the AA involved in tolerance to physical effort showed a statistically significant decrease only at T1 respect to pre-diving value and a returned to normal value at T2. Citrulline, involved in NO production, showed a clear significant reduction both at T1 and T2. Concerning AA involved in endogenous antioxidant synthesis, the behaviour of the three AA investigated is different: we found a statistically significant increase in cystine both at T1 and T2, while glycine showed a statistically significant reduction (T1 and T2). Glutamate did not show any statistical difference. Finally, we found a statistically significant decrease in the AA investigated in other hypoxia conditions serine and taurine (T1 and T2). Conclusions Our data seem to indicate that the energetic metabolic request is in large part supported by AA used as substrate for fuel metabolism and that also fatigue tolerance, NO production and antioxidant synthesis are supported by AA. Finally, there are interesting data related to the hypoxia stimulus that indirectly may confirm that the muscle apparatus works under strong exposure conditions notwithstanding the very short/low intensity of exercise, due to the intermittent hypoxia caused by repetitive diving.
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14
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Kelly T, Brown C, Bryant-Ekstrand M, Lord R, Dawkins T, Drane A, Futral JE, Barak O, Dragun T, Stembridge M, Spajić B, Drviš I, Duke JW, Ainslie PN, Foster GE, Dujic Z, Lovering AT. Blunted hypoxic pulmonary vasoconstriction in apnoea divers. Exp Physiol 2022; 107:1225-1240. [PMID: 35993480 DOI: 10.1113/ep090326] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2022] [Accepted: 08/11/2022] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is new and noteworthy? What is the central question of this study? Does the hyperbaric, hypercapnic, acidotic, hypoxic stress of apnoea diving lead to greater pulmonary vasoreactivity and increased right-heart work in apnoea divers? What is the main finding and its importance? Compared to sex- and age-matched controls, Divers had a significantly lower change in total pulmonary resistance in response to short duration isocapnic hypoxia. With oral sildenafil (50 mg), there were no differences in total pulmonary resistance between groups, suggesting Divers can maintain normal pulmonary artery tone in hypoxic conditions. Blunted hypoxic pulmonary vasoconstriction may be beneficial during apnoea diving. ABSTRACT Competitive apnoea divers repetitively dive to depths beyond 50 m. During the final portions of ascent, Divers experience significant hypoxaemia. Additionally, hyperbaria during diving increases thoracic blood volume while simultaneously reducing lung volume, increasing pulmonary artery pressure. We hypothesized that Divers would have exaggerated hypoxic pulmonary vasoconstriction leading to increased right-heart work due to their repetitive hypoxaemia and hyperbaria, and that the administration of sildenafil would have a greater effect in reducing pulmonary resistance in Divers. We recruited 16 Divers and 16 age and sex matched non-diving controls (Controls). Using a double-blinded, placebo-controlled, cross-over design, participants were evaluated for normal cardiac and lung function, then their cardiopulmonary responses to 20-30 minutes of isocapnic hypoxia (end-tidal PO2 = 50 mm Hg) were measured one hour following ingestion of 50 mg sildenafil or placebo. Cardiac structure and cardiopulmonary function were similar at baseline. With placebo, Divers had a significantly smaller increase in total pulmonary resistance than controls after 20-30 minutes isocapnic hypoxia (Δ -3.85 ± 72.85 vs 73.74 ± 91.06 dynes/sec/cm-5 , p = .0222). With sildenafil, Divers and Controls had similarly blunted increases in total pulmonary resistance after 20-30 minutes of hypoxia. Divers also had a significantly lower systemic vascular resistance following sildenafil in normoxia. These data indicate that repetitive apnoea diving leads to a blunted hypoxic pulmonary vasoconstriction. We suggest this is a beneficial adaption allowing for increased cardiac output with reduced right heart work and thus reducing cardiac oxygen utilization under hypoxemic conditions. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Tyler Kelly
- Department of Human Physiology, University of Oregon, Eugene, Oregon, USA
| | - Courtney Brown
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, BC, Canada
| | | | - Rachel Lord
- School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, Wales, UK
| | - Tony Dawkins
- School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, Wales, UK
| | - Aimee Drane
- School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, Wales, UK
| | - Joel E Futral
- Department of Human Physiology, University of Oregon, Eugene, Oregon, USA
| | - Otto Barak
- Department of Physiology, University of Novi Sad, Novi Sad, Serbia
| | - Tanja Dragun
- Department of Integrative Physiology, University of Split School of Medicine, Split, Croatia
| | - Michael Stembridge
- School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, Wales, UK
| | - Boris Spajić
- Faculty of Kinesiology, University of Zagreb, Zagreb, Croatia
| | - Ivan Drviš
- Faculty of Kinesiology, University of Zagreb, Zagreb, Croatia
| | - Joseph W Duke
- Department of Biological Sciences, Northern Arizona University, Flagstaff, Arizona, USA
| | - Philip N Ainslie
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, BC, Canada
| | - Glen E Foster
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, BC, Canada
| | - Zeljko Dujic
- Department of Integrative Physiology, University of Split School of Medicine, Split, Croatia
| | - Andrew T Lovering
- Department of Human Physiology, University of Oregon, Eugene, Oregon, USA
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15
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Arce-Álvarez A, Salazar-Ardiles C, Cornejo C, Paez V, Vásquez-Muñoz M, Stillner-Vilches K, Jara CR, Ramirez-Campillo R, Izquierdo M, Andrade DC. Chemoreflex Control as the Cornerstone in Immersion Water Sports: Possible Role on Breath-Hold. Front Physiol 2022; 13:894921. [PMID: 35733994 PMCID: PMC9207453 DOI: 10.3389/fphys.2022.894921] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2022] [Accepted: 05/10/2022] [Indexed: 11/30/2022] Open
Abstract
Immersion water sports involve long-term apneas; therefore, athletes must physiologically adapt to maintain muscle oxygenation, despite not performing pulmonary ventilation. Breath-holding (i.e., apnea) is common in water sports, and it involves a decrease and increases PaO2 and PaCO2, respectively, as the primary signals that trigger the end of apnea. The principal physiological O2 sensors are the carotid bodies, which are able to detect arterial gases and metabolic alterations before reaching the brain, which aids in adjusting the cardiorespiratory system. Moreover, the principal H+/CO2 sensor is the retrotrapezoid nucleus, which is located at the brainstem level; this mechanism contributes to detecting respiratory and metabolic acidosis. Although these sensors have been characterized in pathophysiological states, current evidence shows a possible role for these mechanisms as physiological sensors during voluntary apnea. Divers and swimmer athletes have been found to displayed longer apnea times than land sports athletes, as well as decreased peripheral O2 and central CO2 chemoreflex control. However, although chemosensitivity at rest could be decreased, we recently found marked sympathoexcitation during maximum voluntary apnea in young swimmers, which could activate the spleen (which is a reservoir organ for oxygenated blood). Therefore, it is possible that the chemoreflex, autonomic function, and storage/delivery oxygen organ(s) are linked to apnea in immersion water sports. In this review, we summarized the available evidence related to chemoreflex control in immersion water sports. Subsequently, we propose a possible physiological mechanistic model that could contribute to providing new avenues for understanding the respiratory physiology of water sports.
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Affiliation(s)
- Alexis Arce-Álvarez
- Exercise Applied Physiology Laboratory, Centro de Investigación en Fisiología y Medicina de Altura, Departamento Biomedico, Facultad de Ciencias de La Salud, Universidad de Antofagasta, Antofagasta, Chile
- Escuela de Kinesiología, Facultad de Salud, Universidad Católica Silva Henríquez, Santiago, Chile
- Navarrabiomed, Hospital Universitario de Navarra (CHN), Universidad Pública de Navarra (UPNA), IdiSNA, Pamplona, Spain
| | - Camila Salazar-Ardiles
- Exercise Applied Physiology Laboratory, Centro de Investigación en Fisiología y Medicina de Altura, Departamento Biomedico, Facultad de Ciencias de La Salud, Universidad de Antofagasta, Antofagasta, Chile
| | - Carlos Cornejo
- Exercise Applied Physiology Laboratory, Centro de Investigación en Fisiología y Medicina de Altura, Departamento Biomedico, Facultad de Ciencias de La Salud, Universidad de Antofagasta, Antofagasta, Chile
| | - Valeria Paez
- Exercise Applied Physiology Laboratory, Centro de Investigación en Fisiología y Medicina de Altura, Departamento Biomedico, Facultad de Ciencias de La Salud, Universidad de Antofagasta, Antofagasta, Chile
| | - Manuel Vásquez-Muñoz
- Navarrabiomed, Hospital Universitario de Navarra (CHN), Universidad Pública de Navarra (UPNA), IdiSNA, Pamplona, Spain
- Clínica Santa María, Santiago, Chile
| | | | - Catherine R. Jara
- Exercise Applied Physiology Laboratory, Centro de Investigación en Fisiología y Medicina de Altura, Departamento Biomedico, Facultad de Ciencias de La Salud, Universidad de Antofagasta, Antofagasta, Chile
| | - Rodrigo Ramirez-Campillo
- Exercise and Rehabilitation Sciences Laboratory, School of Physical Therapy, Faculty of Rehabilitation Sciences, Universidad Andres Bello, Santiago, Chile
| | - Mikel Izquierdo
- Navarrabiomed, Hospital Universitario de Navarra (CHN), Universidad Pública de Navarra (UPNA), IdiSNA, Pamplona, Spain
| | - David C. Andrade
- Exercise Applied Physiology Laboratory, Centro de Investigación en Fisiología y Medicina de Altura, Departamento Biomedico, Facultad de Ciencias de La Salud, Universidad de Antofagasta, Antofagasta, Chile
- *Correspondence: David C. Andrade, ,
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16
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Bailey DM, Bain AR, Hoiland RL, Barak OF, Drvis I, Hirtz C, Lehmann S, Marchi N, Janigro D, MacLeod DB, Ainslie PN, Dujic Z. Hypoxemia increases blood-brain barrier permeability during extreme apnea in humans. J Cereb Blood Flow Metab 2022; 42:1120-1135. [PMID: 35061562 PMCID: PMC9121528 DOI: 10.1177/0271678x221075967] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Voluntary asphyxia imposed by static apnea challenges blood-brain barrier (BBB) integrity in humans through transient extremes of hypertension, hypoxemia and hypercapnia. In the present study, ten ultra-elite breath-hold divers performed two maximal dry apneas preceded by normoxic normoventilation (NX: severe hypoxemia and hypercapnia) and hyperoxic hyperventilation (HX: absence of hypoxemia with exacerbating hypercapnia) with measurements obtained before and immediately after apnea. Transcerebral exchange of NVU proteins (ELISA, Single Molecule Array) were calculated as the product of global cerebral blood flow (gCBF, duplex ultrasound) and radial arterial to internal jugular venous concentration gradients. Apnea duration increased from 5 m 6 s in NX to 15 m 59 s in HX (P = <0.001) resulting in marked elevations in gCBF and venous S100B, glial fibrillary acidic protein, ubiquitin carboxy-terminal hydrolase-L1 and total tau (all P < 0.05 vs. baseline). This culminated in net cerebral output reflecting mildly increased BBB permeability and increased neuronal-gliovascular reactivity that was more pronounced in NX due to more severe systemic and intracranial hypertension (P < 0.05 vs. HX). These findings identify the hemodynamic stress to which the apneic brain is exposed, highlighting the critical contribution of hypoxemia and not just hypercapnia to BBB disruption.
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Affiliation(s)
- Damian M Bailey
- Neurovascular Research Laboratory, Faculty of Life Sciences and Education, 6654University of South Wales, University of South Wales, Glamorgan, UK
| | - Anthony R Bain
- Faculty of Human Kinetics, University of Windsor, Windsor, ON, Canada
| | - Ryan L Hoiland
- Department of Anaesthesiology, Pharmacology and Therapeutics, Vancouver General Hospital, University of British Columbia, Vancouver, BC, Canada.,Department of Cellular and Physiological Sciences, Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada
| | - Otto F Barak
- School of Medicine, University of Split, Split, Croatia.,Faculty of Medicine, University of Novi Sad, Serbia
| | - Ivan Drvis
- School of Kinesiology, University of Zagreb, Zagreb, Croatia
| | - Christophe Hirtz
- LBPC-PPC, University of Montpellier, Institute of Regenerative Medicine-Biotherapy IRMB, Centre Hospitalier Universitaire de Montpellier, INSERM, Montpellier, France
| | - Sylvain Lehmann
- LBPC-PPC, University of Montpellier, Institute of Regenerative Medicine-Biotherapy IRMB, Centre Hospitalier Universitaire de Montpellier, INSERM, Montpellier, France
| | - Nicola Marchi
- Institute of Functional Genomics, University of Montpellier, Montpellier, France
| | - Damir Janigro
- Department of Physiology, Case Western Reserve University, Cleveland, OH, USA.,FloTBI, Cleveland, OH, USA
| | - David B MacLeod
- Department of Anesthesiology, Duke University Medical Center, Durham, NC, USA
| | - Philip N Ainslie
- Neurovascular Research Laboratory, Faculty of Life Sciences and Education, 6654University of South Wales, University of South Wales, Glamorgan, UK.,Center for Heart Lung and Vascular Health, University of British Columbia, Kelowna, British Columbia, Canada
| | - Zeljko Dujic
- School of Medicine, University of Split, Split, Croatia
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17
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Kulas B, Klassen S, Moir ME, Shoemaker JK. Interactive effects of apneic and baroreflex stress on neural coding strategies in human muscle sympathetic nerve activity. J Neurophysiol 2022; 127:1086-1097. [PMID: 35294276 DOI: 10.1152/jn.00395.2021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The sympathetic nervous system exhibits patterns of action potential (AP) discharge in human muscle sympathetic nerve activity that suggest coding strategies express reflex specificity. This study explored the interactive effects of baroreceptor unloading using lower body negative pressure (LBNP) and volitional end-expiratory apnea (APN) on sympathetic postganglionic neuronal discharge patterns inferred from the firing patterns of differently sized sympathetic AP clusters. Seven individuals were studied using multi-unit microneurography (fibular) and a continuous wavelet approach to quantify AP discharge probability, recruitment, and latency during APN performed under ambient conditions, -10 and -40 mmHg LBNP. Compared to the ambient condition, LBNP increased AP discharge rate at -10 and -40 mmHg and recruited larger previously-silent sympathetic neurons at -40 mmHg. Compared to spontaneous breathing, APN increased AP discharge when performed during the ambient condition (∆351±132 AP/min), -10 mmHg (∆423±184 AP/min), and -40 mmHg (∆355±278 AP/min; main effect APN: P<0.01; LBNP-by-APN interaction: P=0.55). APN recruited larger previously-silent AP clusters during the ambient condition (∆4±3; P<0.02) and -10 mmHg (∆4±3; P<0.01), but not -40 mmHg (∆0±2; P=0.53; LBNP-by-APN: P<0.01). LBNP did not affect AP latency. However, APN reduced AP latency similarly during all conditions (ambient pressure: ∆-0.04±0.04s, -10 mmHg: ∆-0.03±0.03s, -40 mmHg: ∆-0.03±0.04s; main effect APN: P<0.01; LBNP-by-APN: P=0.48). These data indicate that apneic and baroreflex mechanisms appear to additively modify the axonal discharge rate of previously active sympathetic postganglionic neurons and interact to affect recruitment of previously-silent sympathetic neurons. Reductions in AP latency due to apneic stress were not impacted by baroreflex unloading.
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Affiliation(s)
- Bartek Kulas
- Neurovascular Research Laboratory, School of Kinesiology, University of Western Ontario, London, Ontario, Canada
| | - Stephen Klassen
- Neurovascular Research Laboratory, School of Kinesiology, University of Western Ontario, London, Ontario, Canada.,Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, Minnesota, United States
| | - M Erin Moir
- Neurovascular Research Laboratory, School of Kinesiology, University of Western Ontario, London, Ontario, Canada
| | - J Kevin Shoemaker
- Neurovascular Research Laboratory, School of Kinesiology, University of Western Ontario, London, Ontario, Canada.,Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada
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18
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Solich-Talanda M, Żebrowska A, Mikołajczyk R, Kostorz-Nosal S, Ziora D, Jastrzębski D, Siermontowski P. Effect of Apnea-Induced Hypoxia on Cardiovascular Adaptation and Circulating Biomarkers of Oxidative Stress in Elite Breath-Hold Divers. Front Physiol 2021; 12:726434. [PMID: 34566688 PMCID: PMC8458773 DOI: 10.3389/fphys.2021.726434] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2021] [Accepted: 08/09/2021] [Indexed: 11/13/2022] Open
Abstract
Given the previous evidence that breath-hold diving is a cause of physiological stress, this study aimed to determine whether a combination static and dynamic apnea would affect total oxidant status, nitric oxide, heat shock proteins and cardiovascular parameters in elite freedivers. Thirteen finalists of the World and European championships in swimming pool breath-hold diving participated in the study. Whole-body plethysmography and electrocardiography was performed to determine the cardiorespiratory variables at baseline and during the simulation static apnea. An assessment of the heart rate, blood oxygen saturation and biochemical variables was performed before and in response to a combination of a static followed by a dynamic apnea. Static and dynamic breath-holding had a significant effect on oxidative stress, as evidenced by an increase in the total oxidant status/capacity (p < 0.001). The post apnea concentrations of heat shock proteins 27 (HSP27) were significantly elevated (p < 0.03, but total antioxidant status (TAS), HSP90, HSP70, and nitric oxide (NO) changes were not significant. levels under the influence of the static and dynamic breath-hold protocol. A significant positive correlation between HSPs and TAS (r = 0.63; p < 0.05) as well as NO levels was associated with beneficial cardiovascular adaptation. An increase in serum HSP27 levels mediated in nitric oxide levels could explain its important role in improving cardiovascular functions in elite freedivers. Further studies are necessary to explain the exact mechanisms of breath holds training of cardiovascular adaptation responsible for maintaining adequate oxygen supply in elite divers.
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Affiliation(s)
- Magdalena Solich-Talanda
- Department of Physiological and Medical Sciences, Academy of Physical Education, Katowice, Poland
| | | | - Rafał Mikołajczyk
- Department of Physiological and Medical Sciences, Academy of Physical Education, Katowice, Poland
| | - Sabina Kostorz-Nosal
- Department of Lung Diseases and Tuberculosis, Faculty of Medical Sciences in Zabrze, Medical University of Silesia, Zabrze, Poland
| | - Dariusz Ziora
- Department of Lung Diseases and Tuberculosis, Faculty of Medical Sciences in Zabrze, Medical University of Silesia, Zabrze, Poland
| | - Dariusz Jastrzębski
- Department of Lung Diseases and Tuberculosis, Faculty of Medical Sciences in Zabrze, Medical University of Silesia, Zabrze, Poland
| | - Piotr Siermontowski
- Department of Underwater Works Technology, Polish Naval Academy, Gdynia, Poland
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19
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Annen J, Panda R, Martial C, Piarulli A, Nery G, Sanz LRD, Valdivia-Valdivia JM, Ledoux D, Gosseries O, Laureys S. Mapping the functional brain state of a world champion freediver in static dry apnea. Brain Struct Funct 2021; 226:2675-2688. [PMID: 34420066 DOI: 10.1007/s00429-021-02361-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Accepted: 08/04/2021] [Indexed: 11/27/2022]
Abstract
Voluntary apnea showcases extreme human adaptability in trained individuals like professional free divers. We evaluated the psychological and physiological adaptation and the functional cerebral changes using electroencephalography (EEG) and functional Magnetic Resonance Imaging (fMRI) to 6.5 min of dry static apnea performed by a world champion free diver. Compared to resting state at baseline, breath holding was characterized by increased EEG power and functional connectivity in the alpha band, along with decreased delta band connectivity. fMRI connectivity was increased within the default mode network (DMN) and visual areas but decreased in pre- and postcentral cortices. While these changes occurred in regions overlapping with cerebral signatures of several meditation practices, they also display some unique features that suggest an altered somatosensory integration. As suggested by self-reports, these findings could reflect the ability of elite free divers to create a state of sensory dissociation when performing prolonged apnea.
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Affiliation(s)
- Jitka Annen
- Coma Science Group, GIGA Consciousness, University of Liège, Liège, Belgium.
- Centre du Cerveau, University Hospital of Liège, Liège, Belgium.
| | - Rajanikant Panda
- Coma Science Group, GIGA Consciousness, University of Liège, Liège, Belgium
- Centre du Cerveau, University Hospital of Liège, Liège, Belgium
| | - Charlotte Martial
- Coma Science Group, GIGA Consciousness, University of Liège, Liège, Belgium
- Centre du Cerveau, University Hospital of Liège, Liège, Belgium
| | - Andrea Piarulli
- Coma Science Group, GIGA Consciousness, University of Liège, Liège, Belgium
- Department of Surgical, Medical, Molecular and Critical Area Pathology, University of Pisa, Pisa, Italy
| | | | - Leandro R D Sanz
- Coma Science Group, GIGA Consciousness, University of Liège, Liège, Belgium
- Centre du Cerveau, University Hospital of Liège, Liège, Belgium
| | - Juan M Valdivia-Valdivia
- Department of Neurosurgery. St, Joseph's Hospital, Tampa, FL, USA
- International Association for Development of Apnea (AIDA International), Medical and Science Committee, Zurich, Switzerland
| | - Didier Ledoux
- Anesthesia and Intensive Care, GIGA Consciousness, ULiège, Liège, Belgium
- Intensive Care Department, University Hospital of Liège, Liège, Belgium
| | - Olivia Gosseries
- Coma Science Group, GIGA Consciousness, University of Liège, Liège, Belgium
- Centre du Cerveau, University Hospital of Liège, Liège, Belgium
| | - Steven Laureys
- Coma Science Group, GIGA Consciousness, University of Liège, Liège, Belgium
- Centre du Cerveau, University Hospital of Liège, Liège, Belgium
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20
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Serum Cardiac and Skeletal Muscle Marker Changes in Repetitive Breath-hold Diving. SPORTS MEDICINE-OPEN 2021; 7:58. [PMID: 34417928 PMCID: PMC8380208 DOI: 10.1186/s40798-021-00349-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Accepted: 07/28/2021] [Indexed: 11/10/2022]
Abstract
Background Breath-hold diving (BH-diving) is associated to extreme environmental conditions, prolonged physical activity, and complex adaptation mechanisms to supply enough O2 to vital organs. Consequently, one of the biggest effects could be an increased exercise-induced muscle fatigue, in both skeletal and cardiac muscles that can induce an increase of muscles injury markers including creatine kinase (CK), aspartate transferase (AST), and alanine transferase (ALT) when concerning the skeletal muscle, cardiac creatine kinase isoenzyme (CK-MBm) and cardiac troponin I (cTnI) when concerning the cardiac muscle, and lactate dehydrogenase (LDH) as index of muscle stress. The aim of this study is to investigate serum cardiac and skeletal muscle markers before and after a BH-diving training session. Results We found statistically significant increases of CK (T0: 136.1% p < 0.0001; T1: 138.5%, p < 0.0001), CK-MBm (T0: 145.1%, p < 0.0001; T1: 153.2%, p < 0.0001) LDH (T0: 110.4%, p < 0.0003; T1: 110.1%, p < 0.0013) in both T0 and T1 blood samples, as compared to basal value. AST showed a statistically significant increase only at T0 (106.8%, p < 0.0007) while ALT did not exhibit statistically significant changes. We did not find any changes in cTnI levels between pre-dive and post-dive samples. Conclusions Our data seem to indicate that during a BH-diving training session, skeletal and cardiac muscles react to physical effort releasing stress-related substances. Although the peculiar nature of BH-diving makes it difficult to understand if our results are related only to exercise induced muscle adaptation or whether acute hypoxia or a response to environmental changes (pressure) play a role to explain the observed changes, further studies are needed to better understand if these biomarker changes are linked to physical exercise or to acute hypoxia, or if both conditions play a role. Supplementary Information The online version contains supplementary material available at 10.1186/s40798-021-00349-z.
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21
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Bouten J, De Bock S, Bourgois G, de Jager S, Dumortier J, Boone J, Bourgois JG. Heart Rate and Muscle Oxygenation Kinetics During Dynamic Constant Load Intermittent Breath-Holds. Front Physiol 2021; 12:712629. [PMID: 34366898 PMCID: PMC8339880 DOI: 10.3389/fphys.2021.712629] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2021] [Accepted: 06/17/2021] [Indexed: 11/18/2022] Open
Abstract
Introduction: Acute apnea evokes bradycardia and peripheral vasoconstriction in order to conserve oxygen, which is more pronounced with face immersion. This response is contrary to the tachycardia and increased blood flow to muscle tissue related to the higher oxygen consumption during exercise. The aim of this study was to investigate cardiovascular and metabolic responses of dynamic dry apnea (DRA) and face immersed apnea (FIA). Methods: Ten female volunteers (17.1 ± 0.6 years old) naive to breath-hold-related sports, performed a series of seven dynamic 30 s breath-holds while cycling at 25% of their peak power output. This was performed in two separate conditions in a randomized order: FIA (15°C) and DRA. Heart rate and muscle tissue oxygenation through near-infrared spectroscopy were continuously measured to determine oxygenated (m[O2Hb]) and deoxygenated hemoglobin concentration (m[HHb]) and tissue oxygenation index (mTOI). Capillary blood lactate was measured 1 min after the first, third, fifth, and seventh breath-hold. Results: Average duration of the seven breath-holds did not differ between conditions (25.3 s ± 1.4 s, p = 0.231). The apnea-induced bradycardia was stronger with FIA (from 134 ± 4 to 85 ± 3 bpm) than DRA (from 134 ± 4 to 100 ± 5 bpm, p < 0.001). mTOI decreased significantly from 69.9 ± 0.9% to 63.0 ± 1.3% (p < 0.001) which is reflected in a steady decrease in m[O2Hb] (p < 0.001) and concomitant increase in m[HHb] (p = 0.001). However, this was similar in both conditions (0.121 < p < 0.542). Lactate was lower after the first apnea with FIA compared to DRA (p = 0.038), while no differences were observed in the other breath-holds. Conclusion: Our data show strong decreases in heart rate and muscle tissue oxygenation during dynamic apneas. A stronger bradycardia was observed in FIA, while muscle oxygenation was not different, suggesting that FIA did not influence muscle oxygenation. An order of mechanisms was observed in which, after an initial tachycardia, heart rate starts to decrease after muscle tissue deoxygenation occurs, suggesting a role of peripheral vasoconstriction in the apnea-induced bradycardia. The apnea-induced increase in lactate was lower in FIA during the first apnea, probably caused by the stronger bradycardia.
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Affiliation(s)
- Janne Bouten
- Department of Movement and Sports Sciences, Ghent University, Ghent, Belgium
| | - Sander De Bock
- Department of Movement and Sports Sciences, Ghent University, Ghent, Belgium
| | - Gil Bourgois
- Department of Movement and Sports Sciences, Ghent University, Ghent, Belgium
| | - Sarah de Jager
- Department of Movement and Sports Sciences, Ghent University, Ghent, Belgium
| | - Jasmien Dumortier
- Department of Movement and Sports Sciences, Ghent University, Ghent, Belgium
| | - Jan Boone
- Department of Movement and Sports Sciences, Ghent University, Ghent, Belgium.,Centre of Sports Medicine, Ghent University Hospital, Ghent, Belgium
| | - Jan G Bourgois
- Department of Movement and Sports Sciences, Ghent University, Ghent, Belgium.,Centre of Sports Medicine, Ghent University Hospital, Ghent, Belgium
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22
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Tetzlaff K, Lemaitre F, Burgstahler C, Luetkens JA, Eichhorn L. Going to Extremes of Lung Physiology-Deep Breath-Hold Diving. Front Physiol 2021; 12:710429. [PMID: 34305657 PMCID: PMC8299524 DOI: 10.3389/fphys.2021.710429] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2021] [Accepted: 06/16/2021] [Indexed: 01/03/2023] Open
Abstract
Breath-hold diving involves environmental challenges, such as water immersion, hydrostatic pressure, and asphyxia, that put the respiratory system under stress. While training and inherent individual factors may increase tolerance to these challenges, the limits of human respiratory physiology will be reached quickly during deep breath-hold dives. Nonetheless, world records in deep breath-hold diving of more than 214 m of seawater have considerably exceeded predictions from human physiology. Investigations of elite breath-hold divers and their achievements revised our understanding of possible physiological adaptations in humans and revealed techniques such as glossopharyngeal breathing as being essential to achieve extremes in breath-hold diving performance. These techniques allow elite athletes to increase total lung capacity and minimize residual volume, thereby reducing thoracic squeeze. However, the inability of human lungs to collapse early during descent enables respiratory gas exchange to continue at greater depths, forcing nitrogen (N2) out of the alveolar space to dissolve in body tissues. This will increase risk of N2 narcosis and decompression stress. Clinical cases of stroke-like syndromes after single deep breath-hold dives point to possible mechanisms of decompression stress, caused by N2 entering the vasculature upon ascent from these deep dives. Mechanisms of neurological injury and inert gas narcosis during deep breath-hold dives are still incompletely understood. This review addresses possible hypotheses and elucidates factors that may contribute to pathophysiology of deep freediving accidents. Awareness of the unique challenges to pulmonary physiology at depth is paramount to assess medical risks of deep breath-hold diving.
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Affiliation(s)
- Kay Tetzlaff
- Department of Sports Medicine, University Hospital of Tübingen, Tübingen, Germany
| | - Frederic Lemaitre
- Faculte des Sciences du Sport et de l'Education Physique, Universite de Rouen, Rouen, France
| | - Christof Burgstahler
- Department of Sports Medicine, University Hospital of Tübingen, Tübingen, Germany
| | | | - Lars Eichhorn
- Department of Anesthesiology and Intensive Care Medicine, University Hospital Bonn, Bonn, Germany
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23
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Peng H, Kawamura T, Akiyama H, Chang L, Iwata R, Muraoka I. Effects of sex differences on breath-hold diving performance. Respir Physiol Neurobiol 2021; 293:103721. [PMID: 34153544 DOI: 10.1016/j.resp.2021.103721] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2020] [Revised: 05/16/2021] [Accepted: 06/17/2021] [Indexed: 10/21/2022]
Abstract
PURPOSE The present study aimed to measure diving response, CO2 sensitivity and forced vital capacity in male and female breath-hold divers (BHDs), and to determine their effect on breath-hold diving performance. METHODS This study included 8 non-divers (NDs, 4 males and 4 females) and 15 BHDs (7 males and 8 females). For NDs, diving response was measured during breath-holding with facial immersion, whereas for BHDs CO2 sensitivity was also measured. RESULTS Compared to NDs, BHDs showed a prominent diving response. In BHDs, no statistically significant sex differences were observed in diving response and CO2 sensitivity. Furthermore, a positive correlation was found between performance and the % forced vital capacity in BHDs. CONCLUSION It was suggested that % forced vital capacity contributed more significantly to performance than diving response and CO2 sensitivity. Furthermore, the higher performance of male divers compared to female divers may be due to the % forced vital capacity rather than the diving response and CO2 sensitivity.
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Affiliation(s)
- Heng Peng
- Graduate School of Sport Sciences, Waseda University, 2-579-15 Mikajima, Tokorozawa-city, Saitama, 359-1192, Japan.
| | - Takuji Kawamura
- Waseda Institute for Sport Sciences, 2-579-15 Mikajima, Tokorozawa-city, Saitama, 359-1192, Japan
| | - Hiroshi Akiyama
- National Institutes of Biomedical Innovation, Health and Nutrition, 1-23-1 Toyama, Shinjuku-ku, Tokyo, 162-8636, Japan
| | - Lili Chang
- Graduate School of Sport Sciences, Waseda University, 2-579-15 Mikajima, Tokorozawa-city, Saitama, 359-1192, Japan
| | - Risa Iwata
- Japan Institute of Sport Sciences, 3-15-1 Nishigaoka, Kita-ku, Tokyo, 115-0056, Japan
| | - Isao Muraoka
- Faculty of Sport Sciences, Waseda University, 2-579-15 Mikajima, Tokorozawa-city, Saitama, 359-1192, Japan
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24
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D'Souza AW, Badrov MB, Wood KN, Lalande S, Suskin N, Shoemaker JK. The impact of 6 months of exercise-based cardiac rehabilitation on sympathetic neural recruitment during apneic stress. Am J Physiol Regul Integr Comp Physiol 2021; 321:R174-R185. [PMID: 34133229 DOI: 10.1152/ajpregu.00080.2021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The current study evaluated the hypothesis that 6 mo of exercise-based cardiac rehabilitation (CR) would improve sympathetic neural recruitment in patients with ischemic heart disease (IHD). Microneurography was used to evaluate action potential (AP) discharge patterns within bursts of muscle sympathetic nerve activity (MSNA), in 11 patients with IHD (1 female; 61 ± 9 yr) pre (pre-CR) and post (post-CR) 6 mo of aerobic and resistance training-based CR. Measures were made at baseline and during maximal voluntary end-inspiratory (EI-APN) and end-expiratory apneas (EE-APN). Data were analyzed during 1 min of baseline and the second half of apneas. At baseline, overall sympathetic activity was less post-CR (all P < 0.01). During EI-APN, AP recruitment was not observed pre-CR (all P > 0.05), but increases in both within-burst AP firing frequency (Δpre-CR: 2 ± 3 AP spikes/burst vs. Δpost-CR: 4 ± 3 AP spikes/burst; P = 0.02) and AP cluster recruitment (Δpre-CR: -1 ± 2 vs. Δpost-CR: 2 ± 2; P < 0.01) were observed in post-CR tests. In contrast, during EE-APN, AP firing frequency was not different post-CR compared with pre-CR tests (Δpre-CR: 269 ± 202 spikes/min vs. Δpost-CR: 232 ± 225 spikes/min; P = 0.54), and CR did not modify the recruitment of new AP clusters (Δpre-CR: -1 ± 3 vs. Δpost-CR: 0 ± 1; P = 0.39), or within-burst firing frequency (Δpre-CR: 3 ± 3 AP spikes/burst vs. Δpost-CR: 2 ± 2 AP spikes/burst; P = 0.21). These data indicate that CR improves some of the sympathetic nervous system dysregulation associated with cardiovascular disease, primarily via a reduction in resting sympathetic activation. However, the benefits of CR on sympathetic neural recruitment may depend upon the magnitude of initial impairment.
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Affiliation(s)
- Andrew W D'Souza
- Neurovascular Research Laboratory, School of Kinesiology, Western University, London, Ontario, Canada
| | - Mark B Badrov
- Neurovascular Research Laboratory, School of Kinesiology, Western University, London, Ontario, Canada.,Division of Cardiology, Department of Medicine, University Health Network and Sinai Health System, University of Toronto, Toronto, Ontario, Canada
| | - Katelyn N Wood
- Neurovascular Research Laboratory, School of Kinesiology, Western University, London, Ontario, Canada.,Schlegel-University of Waterloo Research Institute for Aging, Waterloo, Ontario, Canada.,Department of Kinesiology, University of Waterloo, Waterloo, Ontario, Canada
| | - Sophie Lalande
- Neurovascular Research Laboratory, School of Kinesiology, Western University, London, Ontario, Canada.,Department of Kinesiology and Health Education, The University of Texas at Austin, Austin, Texas
| | - Neville Suskin
- Cardiac Rehabilitation and Secondary Prevention Program of St. Joseph's Health Care London, London, Ontario, Canada.,Department of Medicine (Cardiology) and Program of Experimental Medicine, Western University, London, Ontario, Canada
| | - J Kevin Shoemaker
- Neurovascular Research Laboratory, School of Kinesiology, Western University, London, Ontario, Canada.,Department of Physiology and Pharmacology, Western University, London, Ontario, Canada
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25
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Stewart M, Bain AR. Assessment of respiratory effort with EMG extracted from ECG recordings during prolonged breath holds: Insights into obstructive apnea and extreme physiology. Physiol Rep 2021; 9:e14873. [PMID: 34042313 PMCID: PMC8157791 DOI: 10.14814/phy2.14873] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Revised: 04/19/2021] [Accepted: 04/21/2021] [Indexed: 11/24/2022] Open
Abstract
Breath holding divers display extraordinary voluntary control over involuntary reactions during apneic episodes. After an initial easy phase to the breath hold, this voluntary control is applied against the increasing involuntary effort to inspire. We quantified an electromyographic (EMG) signal associated with respiratory movements derived from broad bandpass ECG recordings taken from experienced breath holding divers during prolonged dry breath holds. We sought to define their relationship to involuntary respiratory movements and compare these signals with what is known to occur in obstructive sleep apnea (OSA) and epileptic seizures. ECG and inductance plethysmography records from 14 competitive apneists (1 female) were analyzed. ECG records were analyzed for intervals and the EMG signal was extracted from a re‐filtered version of the original broad bandpass signal and ultimately enveloped with a Hilbert transform. EMG burst magnitude, quantified as an area measure, increased over the course of the struggle phase, correlated with inductance plethysmography measures, and corresponded to significant variance in heart rate variability. We conclude that an EMG signal extracted from the ECG can complement plethysmography during breath holds and may help quantify involuntary effort, as reported previously for obstructive sleep apnea. Further, given the resemblance between cardiac and respiratory features of the breath hold struggle phase to obstructive apnea that can occur during sleep or in association with epileptic seizure activity, the struggle phase may be a useful simulation of obstructive apnea for controlled experimentation that can help clarify aspects of acute and chronic apnea‐associated physiology.
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Affiliation(s)
- Mark Stewart
- Department of Physiology & Pharmacology, SUNY Downstate Health Sciences University, Brooklyn, NY, USA
| | - Anthony R Bain
- Department of Kinesiology, Faculty of Human Kinetics, University of Windsor, Windsor, ON, Canada
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26
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Patrician A, Dujić Ž, Spajić B, Drviš I, Ainslie PN. Breath-Hold Diving - The Physiology of Diving Deep and Returning. Front Physiol 2021; 12:639377. [PMID: 34093221 PMCID: PMC8176094 DOI: 10.3389/fphys.2021.639377] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2020] [Accepted: 04/07/2021] [Indexed: 11/13/2022] Open
Abstract
Breath-hold diving involves highly integrative physiology and extreme responses to both exercise and asphyxia during progressive elevations in hydrostatic pressure. With astonishing depth records exceeding 100 m, and up to 214 m on a single breath, the human capacity for deep breath-hold diving continues to refute expectations. The physiological challenges and responses occurring during a deep dive highlight the coordinated interplay of oxygen conservation, exercise economy, and hyperbaric management. In this review, the physiology of deep diving is portrayed as it occurs across the phases of a dive: the first 20 m; passive descent; maximal depth; ascent; last 10 m, and surfacing. The acute risks of diving (i.e., pulmonary barotrauma, nitrogen narcosis, and decompression sickness) and the potential long-term medical consequences to breath-hold diving are summarized, and an emphasis on future areas of research of this unique field of physiological adaptation are provided.
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Affiliation(s)
- Alexander Patrician
- Center for Heart, Lung & Vascular Health, University of British Columbia Okanagan, Kelowna, BC, Canada
| | - Željko Dujić
- Department of Integrative Physiology, University of Split School of Medicine, Split, Croatia
| | - Boris Spajić
- Faculty of Kinesiology, University of Zagreb, Zagreb, Croatia
| | - Ivan Drviš
- Faculty of Kinesiology, University of Zagreb, Zagreb, Croatia
| | - Philip N Ainslie
- Center for Heart, Lung & Vascular Health, University of British Columbia Okanagan, Kelowna, BC, Canada
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27
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Physiology, pathophysiology and (mal)adaptations to chronic apnoeic training: a state-of-the-art review. Eur J Appl Physiol 2021; 121:1543-1566. [PMID: 33791844 PMCID: PMC8144079 DOI: 10.1007/s00421-021-04664-x] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Accepted: 03/04/2021] [Indexed: 02/08/2023]
Abstract
Breath-hold diving is an activity that humans have engaged in since antiquity to forage for resources, provide sustenance and to support military campaigns. In modern times, breath-hold diving continues to gain popularity and recognition as both a competitive and recreational sport. The continued progression of world records is somewhat remarkable, particularly given the extreme hypoxaemic and hypercapnic conditions, and hydrostatic pressures these athletes endure. However, there is abundant literature to suggest a large inter-individual variation in the apnoeic capabilities that is thus far not fully understood. In this review, we explore developments in apnoea physiology and delineate the traits and mechanisms that potentially underpin this variation. In addition, we sought to highlight the physiological (mal)adaptations associated with consistent breath-hold training. Breath-hold divers (BHDs) are evidenced to exhibit a more pronounced diving-response than non-divers, while elite BHDs (EBHDs) also display beneficial adaptations in both blood and skeletal muscle. Importantly, these physiological characteristics are documented to be primarily influenced by training-induced stimuli. BHDs are exposed to unique physiological and environmental stressors, and as such possess an ability to withstand acute cerebrovascular and neuronal strains. Whether these characteristics are also a result of training-induced adaptations or genetic predisposition is less certain. Although the long-term effects of regular breath-hold diving activity are yet to be holistically established, preliminary evidence has posed considerations for cognitive, neurological, renal and bone health in BHDs. These areas should be explored further in longitudinal studies to more confidently ascertain the long-term health implications of extreme breath-holding activity.
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28
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Patrician A, Spajić B, Gasho C, Caldwell HG, Dawkins T, Stembridge M, Lovering AT, Coombs GB, Howe CA, Barak O, Drviš I, Dujić Ž, Ainslie PN. Temporal changes in pulmonary gas exchange efficiency when breath-hold diving below residual volume. Exp Physiol 2021; 106:1120-1133. [PMID: 33559974 DOI: 10.1113/ep089176] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2020] [Accepted: 02/04/2021] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the central question of this study? How does deep breath-hold diving impact cardiopulmonary function, both acutely and over the subsequent 2.5 hours post-dive? What is the main finding and its importance? Breath-hold diving, to depths below residual volume, is associated with acute impairments in pulmonary gas exchange, which typically resolve within 2.5 hours. These data provide new insight into the behaviour of the lungs and pulmonary vasculature following deep diving. ABSTRACT Breath-hold diving involves highly integrative and extreme physiological responses to both exercise and asphyxia during progressive elevations in hydrostatic pressure. Over two diving training camps (Study 1 and 2), 25 breath-hold divers (recreational to world-champion) performed 66 dives to 57 ± 20 m (range: 18-117 m). Using the deepest dive from each diver, temporal changes in cardiopulmonary function were assessed using non-invasive pulmonary gas exchange (indexed via the O2 deficit), ultrasound B-line scores, lung compliance and pulmonary haemodynamics at baseline and following the dive. Hydrostatically induced lung compression was quantified in Study 2, using spirometry and lung volume measurement, enabling each dive to be categorized by its residual volume (RV)-equivalent depth. From both studies, pulmonary gas exchange inefficiency - defined as an increase in O2 deficit - was related to the depth of the dive (r2 = 0.345; P < 0.001), with dives associated with lung squeeze symptoms exhibiting the greatest deficits. In Study 1, although B-lines doubled from baseline (P = 0.027), cardiac output and pulmonary artery systolic pressure were unchanged post-dive. In Study 2, dives with lung compression to ≤RV had higher O2 deficits at 9 min, compared to dives that did not exceed RV (24 ± 25 vs. 5 ± 8 mmHg; P = 0.021). The physiological significance of a small increase in estimated lung compliance post-dive (via decreased and increased/unaltered airway resistance and reactance, respectively) remains equivocal. Following deep dives, the current study highlights an integrated link between hydrostatically induced lung compression and transient impairments in pulmonary gas exchange efficiency.
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Affiliation(s)
- Alexander Patrician
- Center for Heart, Lung & Vascular Health, University of British Columbia - Okanagan, Kelowna, BC, Canada
| | - Boris Spajić
- Faculty of Kinesiology, University of Zagreb, Zagreb, Croatia
| | - Christopher Gasho
- Center for Heart, Lung & Vascular Health, University of British Columbia - Okanagan, Kelowna, BC, Canada
| | - Hannah G Caldwell
- Center for Heart, Lung & Vascular Health, University of British Columbia - Okanagan, Kelowna, BC, Canada
| | - Tony Dawkins
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, UK
| | - Michael Stembridge
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, UK
| | - Andrew T Lovering
- Department of Human Physiology, University of Oregon, Eugene, OR, USA
| | - Geoff B Coombs
- Center for Heart, Lung & Vascular Health, University of British Columbia - Okanagan, Kelowna, BC, Canada
| | - Connor A Howe
- Center for Heart, Lung & Vascular Health, University of British Columbia - Okanagan, Kelowna, BC, Canada
| | - Otto Barak
- Faculty of Medicine, University of Novi Sad, Novi Sad, Serbia
| | - Ivan Drviš
- Faculty of Kinesiology, University of Zagreb, Zagreb, Croatia
| | - Željko Dujić
- University of Split School of Medicine, Split, Croatia
| | - Philip N Ainslie
- Center for Heart, Lung & Vascular Health, University of British Columbia - Okanagan, Kelowna, BC, Canada
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29
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Arce-Álvarez A, Veliz C, Vazquez-Muñoz M, von Igel M, Alvares C, Ramirez-Campillo R, Izquierdo M, Millet GP, Del Rio R, Andrade DC. Hypoxic Respiratory Chemoreflex Control in Young Trained Swimmers. Front Physiol 2021; 12:632603. [PMID: 33716781 PMCID: PMC7953139 DOI: 10.3389/fphys.2021.632603] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Accepted: 02/08/2021] [Indexed: 11/27/2022] Open
Abstract
During an apnea, changes in PaO2 activate peripheral chemoreceptors to increase respiratory drive. Athletes with continuous apnea, such as breath-hold divers, have shown a decrease in hypoxic ventilatory response (HVR), which could explain the long apnea times; however, this has not been studied in swimmers. We hypothesize that the long periods of voluntary apnea in swimmers is related to a decreased HVR. Therefore, we sought to determine the HVR and cardiovascular adjustments during a maximum voluntary apnea in young-trained swimmers. In fifteen trained swimmers and twenty-seven controls we studied minute ventilation (VE), arterial saturation (SpO2), heart rate (HR), and autonomic response [through heart rate variability (HRV) analysis], during acute chemoreflex activation (five inhalations of pure N2) and maximum voluntary apnea test. In apnea tests, the maximum voluntary apnea time and the end-apnea HR were higher in swimmers than in controls (p < 0.05), as well as a higher low frequency component of HRV (p < 0.05), than controls. Swimmers showed lower HVR than controls (p < 0.01) without differences in cardiac hypoxic response (CHR). We conclude that swimmers had a reduced HVR response and greater maximal voluntary apnea duration, probably due to decreased HVR.
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Affiliation(s)
- Alexis Arce-Álvarez
- Escuela de Kinesiología, Facultad de Salud, Universidad Católica Silva Henríquez, Santiago, Chile
| | - Carlos Veliz
- Centro de Investigación en Fisiología del Ejercicio, Facultad de Ciencias, Universidad Mayor, Santiago, Chile
| | - Manuel Vazquez-Muñoz
- Navarrabiomed, Complejo Hospitalario de Navarra (CHN), Universidad Pública de Navarra, IdiSNA, Pamplona, Spain.,Unidad de Estadística, Departamento de Calidad, Clínica Santa María, Santiago, Chile
| | - Magdalena von Igel
- Centro de Investigación en Fisiología del Ejercicio, Facultad de Ciencias, Universidad Mayor, Santiago, Chile
| | - Cristian Alvares
- Laboratory of Human Performance, Quality of Life and Wellness Research Group, Department of Physical Activity Sciences, Universidad de Los Lagos, Osorno, Chile
| | - Rodrigo Ramirez-Campillo
- Centro de Investigación en Fisiología del Ejercicio, Facultad de Ciencias, Universidad Mayor, Santiago, Chile.,Laboratory of Human Performance, Quality of Life and Wellness Research Group, Department of Physical Activity Sciences, Universidad de Los Lagos, Osorno, Chile
| | - Mikel Izquierdo
- Navarrabiomed, Complejo Hospitalario de Navarra (CHN), Universidad Pública de Navarra, IdiSNA, Pamplona, Spain
| | - Gregoire P Millet
- Institute of Sport Sciences, University of Lausanne, Lausanne, Switzerland
| | - Rodrigo Del Rio
- Laboratory of Cardiorespiratory Control, Department of Physiology, Pontificia Universidad Católica de Chile, Santiago, Chile.,Centro de Envejecimiento y Regeneración (CARE), Pontificia Universidad Católica de Chile, Santiago, Chile.,Centro de Excelencia en Biomedicina de Magallanes (CEBIMA), Universidad de Magallanes, Punta Arenas, Chile
| | - David C Andrade
- Centro de Investigación en Fisiología del Ejercicio, Facultad de Ciencias, Universidad Mayor, Santiago, Chile.,Laboratory of Cardiorespiratory Control, Department of Physiology, Pontificia Universidad Católica de Chile, Santiago, Chile.,Centro de Fisiología y Medicina de Altura, Facultad de Ciencias de la Salud, Universidad de Antofagasta, Antofagasta, Chile
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30
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Busch SA, van Diepen S, Roberts R, Steele AR, Berthelsen LF, Smorschok MP, Bourgoin C, Steinback CD. Short-term hypoxia does not promote arrhythmia during voluntary apnea. Physiol Rep 2021; 9:e14703. [PMID: 33426815 PMCID: PMC7797307 DOI: 10.14814/phy2.14703] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2020] [Accepted: 12/06/2020] [Indexed: 12/19/2022] Open
Abstract
The presence of bradycardic arrhythmias during volitional apnea at altitude may be caused by chemoreflex activation/sensitization. We investigated whether bradyarrhythmic episodes became prevalent in apnea following short‐term hypoxia exposure. Electrocardiograms (ECG; lead II) were collected from 22 low‐altitude residents (F = 12; age=25 ± 5 years) at 671 m. Participants were exposed to normobaric hypoxia (Spo2 ~79 ± 3%) over a 5‐h period. ECG rhythms were assessed during both free‐breathing and maximal volitional end‐expiratory and end‐inspiratory apnea at baseline during normoxia and hypoxia exposure (20 min [AHX]; 5 h [HX5]). Free‐breathing HR became elevated at AHX (78 ± 10 bpm; p < 0.0001) and HX5 (80 ± 12 bpm; p < 0.0001) compared to normoxia (68 ± 10 bpm), whereas apnea caused significant bradycardia at AHX (nadir end‐expiratory −17 ± 14 bpm; p < 0.001) and HX5 (nadir end‐expiratory −19 ± 15 bpm; p < 0.001), but not during normoxia (nadir end‐expiratory −4 ± 13 bpm), with no difference in bradycardia responses between apneas at AHX and HX5. Conduction abnormalities were noted in five participants during normoxia (Premature Ventricular Contraction, Sinus Pause, Junctional Rhythm, Atrial Foci), which remained unchanged during apnea at AHX and HX5 (Premature Ventricular Contraction, Premature Atrial Contraction, Sinus Pause). End‐inspiratory apneas were overall longer across conditions (normoxia p < 0.05; AHX p < 0.01; HX5 p < 0.001), with comparable HR responses to end‐expiratory and fewer occurrences of arrhythmia. While short‐term hypoxia is sufficient to elicit bradycardia during apnea, the occurrence of arrhythmias in response to apnea was not affected. These findings indicate that previously observed bradyarrhythmic events in untrained individuals at altitude only become prevalent following chronic hypoxia specificlly.
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Affiliation(s)
- Stephen A Busch
- Neurovascular Health Laboratory, Faculty of Kinesiology, Sport, and Recreation, University of Alberta, Edmonton, Canada
| | - Sean van Diepen
- Department of Critical Care and Divison of Cardiology, Department of Medicine, University of Alberta, Edmonton, Canada
| | - Richard Roberts
- Department of Physiology, Faculty of Medicine & Dentistry, University of Alberta, Edmonton, Canada
| | - Andrew R Steele
- Neurovascular Health Laboratory, Faculty of Kinesiology, Sport, and Recreation, University of Alberta, Edmonton, Canada
| | - Lindsey F Berthelsen
- Neurovascular Health Laboratory, Faculty of Kinesiology, Sport, and Recreation, University of Alberta, Edmonton, Canada
| | - Megan P Smorschok
- Neurovascular Health Laboratory, Faculty of Kinesiology, Sport, and Recreation, University of Alberta, Edmonton, Canada
| | - Cody Bourgoin
- Neurovascular Health Laboratory, Faculty of Kinesiology, Sport, and Recreation, University of Alberta, Edmonton, Canada
| | - Craig D Steinback
- Neurovascular Health Laboratory, Faculty of Kinesiology, Sport, and Recreation, University of Alberta, Edmonton, Canada
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Cialoni D, Brizzolari A, Samaja M, Bosco G, Paganini M, Pieri M, Lancellotti V, Marroni A. Nitric Oxide and Oxidative Stress Changes at Depth in Breath-Hold Diving. Front Physiol 2021; 11:609642. [PMID: 33488400 PMCID: PMC7818785 DOI: 10.3389/fphys.2020.609642] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2020] [Accepted: 12/01/2020] [Indexed: 12/14/2022] Open
Abstract
Background Several mechanisms allow humans to resist the extreme conditions encountered during breath-hold diving. Available nitric oxide (NO) is one of the major contributors to such complex adaptations at depth and oxidative stress is one of the major collateral effects of diving. Due to technical difficulties, these biomarkers have not so far been studied in vivo while at depth. The aim of this study is to investigate nitrate and nitrite (NOx) concentration, total antioxidant capacity (TAC) and lipid peroxidation (TBARS) before, during, and after repetitive breath-hold dives in healthy volunteers. Materials and Methods Blood plasma, obtained from 14 expert breath-hold divers, was tested for differences in NOx, TAC, and TBARS between pre-dive, bottom, surface, 30 and 60 min post-dive samples. Results We observed a statistically significant increase of NOx plasma concentration in the “bottom blood draw” as compared to the pre-dive condition while we did not find any difference in the following samples We found a statistically significant decrease in TAC at the bottom but the value returned to normality immediately after reaching the surface. We did not find any statistically significant difference in TBARS. Discussion The increased plasma NOx values found at the bottom were not observed at surface and post dive sampling (T0, T30, T60), showing a very rapid return to the pre-dive values. Also TAC values returned to pre- diving levels immediately after the end of hyperbaric exposure, probably as a consequence of the activation of endogenous antioxidant defenses. TBARS did not show any difference during the protocol.
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Affiliation(s)
- Danilo Cialoni
- Environmental Physiology and Medicine Laboratory, Department of Biomedical Sciences, University of Padova, Padova, Italy.,Divers Alert Network (DAN) Europe Research Division, Roseto degli Abruzzi, Italy.,Apnea Academy Research, Padova, Italy
| | - Andrea Brizzolari
- Divers Alert Network (DAN) Europe Research Division, Roseto degli Abruzzi, Italy.,Department of Health Sciences, Università degli Studi of Milan, Milan, Italy
| | - Michele Samaja
- Department of Health Sciences, Università degli Studi of Milan, Milan, Italy
| | - Gerardo Bosco
- Environmental Physiology and Medicine Laboratory, Department of Biomedical Sciences, University of Padova, Padova, Italy
| | - Matteo Paganini
- Environmental Physiology and Medicine Laboratory, Department of Biomedical Sciences, University of Padova, Padova, Italy
| | - Massimo Pieri
- Divers Alert Network (DAN) Europe Research Division, Roseto degli Abruzzi, Italy
| | - Valentina Lancellotti
- Cardiothoracic and Vascular Department, Azienda Ospedaliero-Universitaria Pisana (AOUP), Pisa, Italy
| | - Alessandro Marroni
- Divers Alert Network (DAN) Europe Research Division, Roseto degli Abruzzi, Italy
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Morra S, Gauthey A, Hossein A, Rabineau J, Racape J, Gorlier D, Migeotte PF, le Polain de Waroux JB, van de Borne P. Influence of sympathetic activation on myocardial contractility measured with ballistocardiography and seismocardiography during sustained end-expiratory apnea. Am J Physiol Regul Integr Comp Physiol 2020; 319:R497-R506. [PMID: 32877240 DOI: 10.1152/ajpregu.00142.2020] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Ballistocardiography (BCG) and seismocardiography (SCG) assess vibrations produced by cardiac contraction and blood flow, respectively, through micro-accelerometers and micro-gyroscopes. BCG and SCG kinetic energies (KE) and their temporal integrals (iK) during a single heartbeat are computed in linear and rotational dimensions. Our aim was to test the hypothesis that iK from BCG and SCG are related to sympathetic activation during maximal voluntary end-expiratory apnea. Multiunit muscle sympathetic nerve traffic [burst frequency (BF), total muscular sympathetic nerve activity (tMSNA)] was measured by microneurography during normal breathing and apnea (n = 28, healthy men). iK of BCG and SCG were simultaneously recorded in the linear and rotational dimension, along with oxygen saturation ([Formula: see text]) and systolic blood pressure (SBP). The mean duration of apneas was 25.4 ± 9.4 s. SBP, BF, and tMSNA increased during the apnea compared with baseline (P = 0.01, P = 0.002,and P = 0.001, respectively), whereas [Formula: see text] decreased (P = 0.02). At the end of the apnea compared with normal breathing, changes in iK computed from BCG were related to changes of tMSNA and BF only in the linear dimension (r = 0.85, P < 0.0001; and r = 0.72, P = 0.002, respectively), whereas changes in linear iK of SCG were related only to changes of tMSNA (r = 0.62, P = 0.01). We conclude that maximal end expiratory apnea increases cardiac kinetic energy computed from BCG and SCG, along with sympathetic activity. The novelty of the present investigation is that linear iK of BCG is directly and more strongly related to the rise in sympathetic activity than the SCG, mainly at the end of a sustained apnea, likely because the BCG is more affected by the sympathetic and hemodynamic effects of breathing cessation. BCG and SCG may prove useful to assess sympathetic nerve changes in patients with sleep disturbances.NEW & NOTEWORTHY Ballistocardiography (BCG) and seismocardiography (SCG) assess vibrations produced by cardiac contraction and blood flow, respectively, through micro-accelerometers and micro-gyroscopes. Kinetic energies (KE) and their temporal integrals (iK) during a single heartbeat are computed from the BCG and SCG waveforms in a linear and a rotational dimension. When compared with normal breathing, during an end-expiratory voluntary apnea, iK increased and was positively related to sympathetic nerve traffic rise assessed by microneurography. Further studies are needed to determine whether BCG and SCG can probe sympathetic nerve changes in patients with sleep disturbances.
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Affiliation(s)
- Sofia Morra
- Department of Cardiology, Erasme Hospital, Université Libre de Bruxelles, Brussels, Belgium
| | - Anais Gauthey
- Department of Cardiology, Saint-Luc hospital, Université Catholique de Louvain, Brussels, Belgium
| | - Amin Hossein
- Laboratory of Physics and Physiology, Université Libre de Bruxelles, Brussels, Belgium
| | - Jérémy Rabineau
- Laboratory of Physics and Physiology, Université Libre de Bruxelles, Brussels, Belgium
| | - Judith Racape
- Research Centre in Epidemiology, Biostatistics and Clinical Research. School of Public Health. Université Libre de Bruxelles, Brussels, Belgium
| | - Damien Gorlier
- Laboratory of Physics and Physiology, Université Libre de Bruxelles, Brussels, Belgium
| | | | | | - Philippe van de Borne
- Department of Cardiology, Erasme Hospital, Université Libre de Bruxelles, Brussels, Belgium
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33
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Hold your breath: peripheral and cerebral oxygenation during dry static apnea. Eur J Appl Physiol 2020; 120:2213-2222. [PMID: 32748010 DOI: 10.1007/s00421-020-04445-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Accepted: 07/17/2020] [Indexed: 01/17/2023]
Abstract
PURPOSE Acute breath-holding deprives the human body from oxygen. In an effort to protect the brain, the diving response is initiated, coupling several physiological responses. The aim of this study was to describe the physiological responses to apnea at the cardiac, peripheral and cerebral level. METHODS 31 physically active subjects (17 male, 14 female, 23.3 ± 1.8 years old) performed a maximal static breath-hold in a seated position. Heart rate (HR), muscle and cerebral oxygenation (by means of near-infrared spectroscopy, NIRS) were continuously measured. RM MANOVA's were used to identify changes in HR, peripheral (mTOI) and cerebral (cTOI) tissue oxygenation and oxygenated (O2Hb) and deoxygenated (HHb) hemoglobin during apnea. RESULTS Average apnea duration was 157 ± 41 s. HR started decreasing after 10 s (p < 0.001) and dropped on average by 27 ± 14 bpm from baseline (p < 0.001). mTOI started decreasing 10 s after apnea (p < 0.001) and fell by 8.6 ± 4.0% (p < 0.001). Following an immediate drop after 5 s (p < 0.001), cTOI increased continuously, reaching a maximal increase of 3.7 ± 2.4% followed by a steady decrease until the end of apnea. cTOI fell on average 5.4 ± 8.3% below baseline (p < 0.001). CONCLUSION During apnea, the human body elicits several protective mechanisms to protect itself against the deprivation of oxygen. HR slows down, decreasing O2 demand of the cardiac muscle. The decrease in mTOI and increase in cTOI imply a redistribution of blood flow prioritizing the brain. However, this mechanism is not sufficient to maintain cTOI until the end of apnea.
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35
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Kunz M, Lauder L, Ewen S, Böhm M, Mahfoud F. The Current Status of Devices for the Treatment of Resistant Hypertension. Am J Hypertens 2020; 33:10-18. [PMID: 31570933 DOI: 10.1093/ajh/hpz161] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Revised: 09/23/2019] [Accepted: 09/29/2019] [Indexed: 12/22/2022] Open
Abstract
Arterial hypertension is associated with increased cardiovascular morbidity and mortality. Although blood pressure-lowering therapies significantly reduce the risk of major cardiovascular events, blood pressure control remains unsatisfactorily low. Several device-based antihypertensive therapies have been investigated in patients with treatment-resistant hypertension and in patients unable or unwilling to adhere to antihypertensive medication. As the field of device-based therapies is subject to constant change, this review aims at providing an up-to-date overview of different device-based approaches for the treatment of hypertension. These approaches target the sympathetic nervous system (renal denervation, baroreflex amplification therapy, baroreflex activation therapy, and carotid body ablation) or alter mechanical arterial properties by creating an iliac arteriovenous fistula. Notably, the use of all of these treatment options is not recommended for the routine treatment of hypertension by current guidelines but should be investigated in the context of controlled clinical studies.
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Affiliation(s)
- Michael Kunz
- Klinik für Innere Medizin III, Kardiologie, Angiologie und Internistische Intensivmedizin, Universitätsklinikum des Saarlandes, Saarland University, Homburg/Saar, Germany
| | - Lucas Lauder
- Klinik für Innere Medizin III, Kardiologie, Angiologie und Internistische Intensivmedizin, Universitätsklinikum des Saarlandes, Saarland University, Homburg/Saar, Germany
| | - Sebastian Ewen
- Klinik für Innere Medizin III, Kardiologie, Angiologie und Internistische Intensivmedizin, Universitätsklinikum des Saarlandes, Saarland University, Homburg/Saar, Germany
| | - Michael Böhm
- Klinik für Innere Medizin III, Kardiologie, Angiologie und Internistische Intensivmedizin, Universitätsklinikum des Saarlandes, Saarland University, Homburg/Saar, Germany
| | - Felix Mahfoud
- Klinik für Innere Medizin III, Kardiologie, Angiologie und Internistische Intensivmedizin, Universitätsklinikum des Saarlandes, Saarland University, Homburg/Saar, Germany
- Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
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36
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Morra S, Hossein A, Gorlier D, Rabineau J, Chaumont M, Migeotte PF, van de Borne P. Modification of the mechanical cardiac performance during end-expiratory voluntary apnea recorded with ballistocardiography and seismocardiography. Physiol Meas 2019; 40:105005. [PMID: 31579047 DOI: 10.1088/1361-6579/ab4a6a] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE To assess if micro-accelerometers and gyroscopes may provide useful information for the detection of breathing disturbances in further studies. APPROACH Forty-three healthy volunteers performed a 10 s end-expiratory breath-hold, while ballistocardiograph (BCG) and seismocardiograph (SCG) determined changes in kinetic energy and its integral over time (iK, J · s). BCG measures overall body accelerations in response to blood mass ejection into the main vasculature at each cardiac cycle, while SCG records local chest wall vibrations generated beat-by-beat by myocardial activity. This minimally intrusive technology assesses linear accelerations and angular velocities in 12 degrees of freedom to calculate iK during the whole cardiac cycle. iK produced during systole and diastole were also computed. MAIN RESULTS The iK during normal breathing was 87.1 [63.3; 132.8] µJ · s for the SCG and 4.5 [3.3; 6.2] µJ · s for the BCG. Both increased to 107.1 [69.0; 162.0] µJ · s and 6.1 [4.4; 9.0] µJ · s, respectively, during breath-holding (p = 0.003 and p < 0.0001, respectively). The iK of the SCG further increased during spontaneous respiration following apnea (from 107.1 [69.0; 162.0] µJ · s to 160.0 [96.3; 207.3] µJ · s, p < 0.0001). The ratio between the iK of diastole and systole increased from 0.35 [0.24; 0.45] during apnea to 0.49 [0.31; 0.80] (p < 0.0001) during the restoration of respiration. SIGNIFICANCE A brief voluntary apnea generates large and distinct increases in SCG and BCG waveforms. iK monitoring during sleep may prove useful for the detection of respiratory disturbances. ClinicalTrials.gov number: NCT03760159.
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Affiliation(s)
- Sofia Morra
- Department of Cardiology, Erasme Hospital, Université Libre de Bruxelles, Bruxelles, Belgium.,Author to whom any correspondence should be addressed
| | - Amin Hossein
- LPHYS, Université Libre de Bruxelles, Bruxelles, Belgium
| | - Damien Gorlier
- LPHYS, Université Libre de Bruxelles, Bruxelles, Belgium
| | | | - Martin Chaumont
- Department of Cardiology, Erasme Hospital, Université Libre de Bruxelles, Bruxelles, Belgium
| | | | - Philippe van de Borne
- Department of Cardiology, Erasme Hospital, Université Libre de Bruxelles, Bruxelles, Belgium.,Both authors contributed equally
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Kanthack TFD, Guillot A, Saboul D, Debarnot U, Di Rienzo F. Breathing with the mind: Effects of motor imagery on breath-hold performance. Physiol Behav 2019; 208:112583. [PMID: 31220518 DOI: 10.1016/j.physbeh.2019.112583] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2019] [Revised: 06/14/2019] [Accepted: 06/14/2019] [Indexed: 10/26/2022]
Abstract
We aimed at studying the effect of Motor Imagery (MI), i.e., the mental representation of a movement without executing it, on breath-holding performance. Classical guidelines for efficient MI interventions advocate for a congruent MI practice with regards to the requirements of the physical performance, specifically in terms of physiological arousal. We specifically aimed at studying whether an incongruent form of MI practice might enhance the breath-hold performance. In a counterbalanced design including three experimental sessions, participants engaged in maximal breath-hold trials while concomitantly performing i) MI of breathing, ii) MI of breath-hold, and iii) an "ecological" breath-hold trial, i.e., without specific instructions of MI practice. In addition to breath-hold durations, we measured the cardiac activity and blood oxygen saturation. Performance was improved during MI of breathing (73.06 s ± 24.53) compared to both MI of breath-hold (70.57 s ± 18.15) and the control condition (67.67 s ± 19.27) (p < 0.05). The mechanisms underlying breath-hold performance improvements during MI of breathing remain uncertain. MI of breathing might participate to decrease the threat perception associated with breath-holding, presumably due to psychological and physiological effects associated with the internal simulation of a breathing body state.
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Affiliation(s)
- T Ferreira Dias Kanthack
- Univ Lyon, Université Claude Bernard Lyon 1, Laboratoire Interuniversitaire de Biologie de la Motricité, EA 7424, F69622, Villeurbanne Cedex, France; CAPES Foundation, Ministry of Education of Brazil, Brasília, Distrito Federal, Brazil; Faculdade de Ensino Superior do Interior Paulista, Marília, Brazil
| | - Aymeric Guillot
- Univ Lyon, Université Claude Bernard Lyon 1, Laboratoire Interuniversitaire de Biologie de la Motricité, EA 7424, F69622, Villeurbanne Cedex, France; Institut Universitaire de France, Paris, France
| | - Damien Saboul
- Univ Lyon, Université Claude Bernard Lyon 1, Laboratoire Interuniversitaire de Biologie de la Motricité, EA 7424, F69622, Villeurbanne Cedex, France; Be-Studys, a Brand of Be-Ys Group, route de Meyrin 123, 1219 Vernier - Châtelaine, Genève, Switzerland
| | - Ursula Debarnot
- Univ Lyon, Université Claude Bernard Lyon 1, Laboratoire Interuniversitaire de Biologie de la Motricité, EA 7424, F69622, Villeurbanne Cedex, France
| | - Franck Di Rienzo
- Univ Lyon, Université Claude Bernard Lyon 1, Laboratoire Interuniversitaire de Biologie de la Motricité, EA 7424, F69622, Villeurbanne Cedex, France.
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Ott EP, Baker SE, Holbein WW, Shoemaker JK, Limberg JK. Effect of varying chemoreflex stress on sympathetic neural recruitment strategies during apnea. J Neurophysiol 2019; 122:1386-1396. [PMID: 31389742 DOI: 10.1152/jn.00319.2019] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
We sought to examine the effect of varying chemoreflex stress on sympathetic neural recruitment strategies during end-expiratory apnea. We hypothesized that increases in the firing frequency and probability of low-threshold axons at the asphyxic "break point" would be exaggerated during hypoxia and attenuated during hyperoxia. Multiunit muscle sympathetic nervous system activity (MSNA) (peroneal nerve microneurography) was measured in 10 healthy male subjects (31 ± 2 yr, 25 ± 1 kg/m2). Individuals completed maximal voluntary end-expiratory apnea under normoxic, hypoxic (inspired O2 fraction: 0.17 ± 0.01), and hyperoxic (inspired O2 fraction: 0.92 ± 0.03) conditions. Action potential (AP) patterns were examined from the filtered raw signal with wavelet-based methodology. Multiunit MSNA was increased (P ≤ 0.05) during normoxic apnea, because of an increase in the frequency and incidence of AP spikes (243 ± 75 to 519 ± 134 APs/min, P = 0.048; 412 ± 133 to 733 ± 185 APs/100 heartbeats, P = 0.02). Multiunit MSNA increased from baseline (P < 0.01) during hypoxic apnea, which was due to an increase in the frequency and incidence of APs (192 ± 59 to 952 ± 266 APs/min, P < 0.01; 326 ± 89 to 1,212 ± 327 APs/100 heartbeats, P < 0.01). Hypoxic apnea also resulted in an increase in the probability of a particular AP cluster firing more than once per burst (P < 0.01). Hyperoxia attenuated any increase in MSNA with apnea, such that no changes in multiunit MSNA or frequency or incidence of AP spikes were observed (P > 0.05). We conclude that increases in frequency and incidence of APs during apnea are potentiated during hypoxia and suppressed when individuals are hyperoxic, highlighting the important impact of chemoreflex stress in AP discharge patterns. The results may have implications for neural control of the circulation in recreational activities and/or clinical conditions prone to apnea.NEW & NOTEWORTHY Our results demonstrate that, compared with normoxic end-expiratory apnea, hypoxic apnea increases the frequency and incidence of action potential spikes as well as the probability of multiple firing. We further show that this response is suppressed when individuals are hyperoxic. These data highlight the potentially important role of chemoreflex stress in neural firing and recruitment and may have implications for neural control of the circulation in recreational and/or clinical conditions prone to apnea.
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Affiliation(s)
- Elizabeth P Ott
- Department of Nutrition and Exercise Physiology, University of Missouri, Columbia, Missouri
| | - Sarah E Baker
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, Minnesota
| | - Walter W Holbein
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, Minnesota
| | - J Kevin Shoemaker
- School of Kinesiology, University of Western Ontario, London, Ontario, Canada
| | - Jacqueline K Limberg
- Department of Nutrition and Exercise Physiology, University of Missouri, Columbia, Missouri.,Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, Minnesota
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Bain AR, Drvis I, Dujic Z, MacLeod DB, Ainslie PN. Physiology of static breath holding in elite apneists. Exp Physiol 2019; 103:635-651. [PMID: 29512224 DOI: 10.1113/ep086269] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2017] [Accepted: 03/02/2018] [Indexed: 12/16/2022]
Abstract
NEW FINDINGS What is the topic of this review? This review provides an up-to-date assessment of the physiology involved with extreme static dry-land breath holding in trained apneists. What advances does it highlight? We specifically highlight the recent findings involved with the cardiovascular, cerebrovascular and metabolic function during a maximal breath hold in elite apneists. ABSTRACT Breath-hold-related activities have been performed for centuries, but only recently, within the last ∼30 years, has it emerged as an increasingly popular competitive sport. In apnoea sport, competition relates to underwater distances or simply maximal breath-hold duration, with the current (oxygen-unsupplemented) static breath-hold record at 11 min 35 s. Remarkably, many ultra-elite apneists are able to suppress respiratory urges to the point where consciousness fundamentally limits a breath-hold duration. Here, arterial oxygen saturations as low as ∼50% have been reported. In such cases, oxygen conservation to maintain cerebral functioning is critical, where responses ascribed to the mammalian dive reflex, e.g. sympathetically mediated peripheral vasoconstriction and vagally mediated bradycardia, are central. In defence of maintaining global cerebral oxygen delivery during prolonged breath holds, the cerebral blood flow may increase by ∼100% from resting values. Interestingly, near the termination of prolonged dry static breath holds, recent studies also indicate that reductions in the cerebral oxidative metabolism can occur, probably attributable to the extreme hypercapnia and irrespective of the hypoxaemia. In this review, we highlight and discuss the recent data on the cardiovascular, metabolic and, particularly, cerebrovascular function in competitive apneists performing maximal static breath holds. The physiological adaptation and maladaptation with regular breath-hold training are also summarized, and future research areas in this unique physiological field are highlighted; particularly, the need to determine the potential long-term health impacts of extreme breath holding.
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Affiliation(s)
- Anthony R Bain
- Center for Heart, Lung and Vascular Health, University of British Columbia, Kelowna, BC, Canada.,Integrative Physiology, University of Colorado, Boulder, CO, USA
| | - Ivan Drvis
- Faculty of Kinesiology, University of Zagreb, Zagreb, Croatia
| | - Zeljko Dujic
- Department of Integrative Physiology, University of Split School of Medicine, Split, Croatia
| | - David B MacLeod
- Human Pharmacology and Physiology Laboratory, Department of Anesthesiology, Duke University Medical Center, Durham, NC, USA
| | - Philip N Ainslie
- Center for Heart, Lung and Vascular Health, University of British Columbia, Kelowna, BC, Canada
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Busch SA, Bruce CD, Skow RJ, Pfoh JR, Day TA, Davenport MH, Steinback CD. Mechanisms of sympathetic regulation during Apnea. Physiol Rep 2019; 7:e13991. [PMID: 30693670 PMCID: PMC6349657 DOI: 10.14814/phy2.13991] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2018] [Accepted: 12/26/2018] [Indexed: 12/11/2022] Open
Abstract
Volitional Apnea produces a robust peak sympathetic response through several interacting mechanisms. However, the specific contribution of each mechanism has not been elucidated. Muscle sympathetic activity was collected in participants (n = 10; 24 ± 3 years) that performed four maximal volitional apneas aimed at isolating lung-stretch (mechanical) and chemoreflex drive: (Ainslie and Duffin ) end-expiratory breath-hold, (Ainslie et al. ) end-inspiratory breath-hold, (Alpher et al. ) prehyperventilation breath-hold, and (Andersson and Schagatay ) prehyperoxia breath-hold. A final repeated rebreathe breath-hold protocol was performed to measure the peak sympathetic response during successive breath-holds at increasing chemoreflex stress. Finally, the influence of dynamic ventilation was assessed through asphyxic rebreathe. Muscle sympathetic activity was calculated as the change in burst frequency (burst/min), burst incidence (burst/100 heart-beats), and amplitude (au) between baseline and prevolitional breakpoint. Rebreathe was analyzed at similar chemoreflex stress as inspiratory breath-hold. All maneuvers increased muscle sympathetic activity compared to baseline (P < 0.01). However, prehyperoxia exhibited a smaller increase (+22.18 ± 9.13 burst/min; +25.52 ± 11.7 burst/100 heart-beats) compared to inspiratory, expiratory, and prehyperventilation breath-holds. At similar chemoreflex strain, rebreathe sympathetic activity was blunted compared to inspiratory breath-hold (P < 0.01). Finally, muscle sympathetic activity was not different between the repeated rebreathe trials, despite elevated chemoreflex stress and lower breath-hold duration with each subsequent breath-hold. We have demonstrated an obligatory role of the peripheral, but not central, chemoreflex (prehyperventilation vs. prehyperoxia) in producing peak sympathetic responses. At similar chemoreflex stresses the act of dynamic ventilation, but not static lung stretch per se, blunts muscle sympathetic activity. Finally, similar peak sympathetic responses during successive repeated breath-holds suggest a sympathetic ceiling may exist.
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Affiliation(s)
- Stephen A. Busch
- Neurovascular Health LaboratoryFaculty of Kinesiology, Sport, and RecreationUniversity of AlbertaEdmontonAlbertaCanada
| | - Christina D. Bruce
- Department of BiologyFaculty of Science and TechnologyMount Royal UniversityCalgaryAlbertaCanada
| | - Rachel J. Skow
- Neurovascular Health LaboratoryFaculty of Kinesiology, Sport, and RecreationUniversity of AlbertaEdmontonAlbertaCanada
| | - Jaime R. Pfoh
- Department of BiologyFaculty of Science and TechnologyMount Royal UniversityCalgaryAlbertaCanada
| | - Trevor A. Day
- Department of BiologyFaculty of Science and TechnologyMount Royal UniversityCalgaryAlbertaCanada
| | - Margie H. Davenport
- Neurovascular Health LaboratoryFaculty of Kinesiology, Sport, and RecreationUniversity of AlbertaEdmontonAlbertaCanada
| | - Craig D. Steinback
- Neurovascular Health LaboratoryFaculty of Kinesiology, Sport, and RecreationUniversity of AlbertaEdmontonAlbertaCanada
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Eichhorn L, Doerner J, Luetkens JA, Lunkenheimer JM, Dolscheid-Pommerich RC, Erdfelder F, Fimmers R, Nadal J, Stoffel-Wagner B, Schild HH, Hoeft A, Zur B, Naehle CP. Cardiovascular magnetic resonance assessment of acute cardiovascular effects of voluntary apnoea in elite divers. J Cardiovasc Magn Reson 2018; 20:40. [PMID: 29909774 PMCID: PMC6004697 DOI: 10.1186/s12968-018-0455-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2017] [Accepted: 05/08/2018] [Indexed: 12/02/2022] Open
Abstract
BACKGROUND Prolonged breath holding results in hypoxemia and hypercapnia. Compensatory mechanisms help maintain adequate oxygen supply to hypoxia sensitive organs, but burden the cardiovascular system. The aim was to investigate human compensatory mechanisms and their effects on the cardiovascular system with regard to cardiac function and morphology, blood flow redistribution, serum biomarkers of the adrenergic system and myocardial injury markers following prolonged apnoea. METHODS Seventeen elite apnoea divers performed maximal breath-hold during cardiovascular magnetic resonance imaging (CMR). Two breath-hold sessions were performed to assess (1) cardiac function, myocardial tissue properties and (2) blood flow. In between CMR sessions, a head MRI was performed for the assessment of signs of silent brain ischemia. Urine and blood samples were analysed prior to and up to 4 h after the first breath-hold. RESULTS Mean breath-hold time was 297 ± 52 s. Left ventricular (LV) end-systolic, end-diastolic, and stroke volume increased significantly (p < 0.05). Peripheral oxygen saturation, LV ejection fraction, LV fractional shortening, and heart rate decreased significantly (p < 0.05). Blood distribution was diverted to cerebral regions with no significant changes in the descending aorta. Catecholamine levels, high-sensitivity cardiac troponin, and NT-pro-BNP levels increased significantly, but did not reach pathological levels. CONCLUSION Compensatory effects of prolonged apnoea substantially burden the cardiovascular system. CMR tissue characterisation did not reveal acute myocardial injury, indicating that the resulting cardiovascular stress does not exceed compensatory physiological limits in healthy subjects. However, these compensatory mechanisms could overly tax those limits in subjects with pre-existing cardiac disease. For divers interested in competetive apnoea diving, a comprehensive medical exam with a special focus on the cardiovascular system may be warranted. TRIAL REGISTRATION This prospective single-centre study was approved by the institutional ethics committee review board. It was retrospectively registered under ClinicalTrials.gov (Trial registration: NCT02280226 . Registered 29 October 2014).
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Affiliation(s)
- L. Eichhorn
- Department of Anaesthesiology and Intensive Care Medicine, University Hospital of Bonn, Bonn, Germany
| | - J. Doerner
- Department of Radiology, University Hospital of Bonn, Bonn, Germany
- Department of Radiology, University Hospital of Cologne, Cologne, Germany
| | - J. A. Luetkens
- Department of Radiology, University Hospital of Bonn, Bonn, Germany
| | | | | | - F. Erdfelder
- Department of Anaesthesiology and Intensive Care Medicine, University Hospital of Bonn, Bonn, Germany
| | - R. Fimmers
- Medical Biometry, Information Technology and Epidemiology, University of Bonn, Bonn, Germany
| | - J. Nadal
- Medical Biometry, Information Technology and Epidemiology, University of Bonn, Bonn, Germany
| | - B. Stoffel-Wagner
- Institute for Medical Biometry, Informatics and Epidemiology (IMBIE), Bonn, Germany
| | - H. H. Schild
- Department of Radiology, University Hospital of Bonn, Bonn, Germany
| | - A. Hoeft
- Department of Anaesthesiology and Intensive Care Medicine, University Hospital of Bonn, Bonn, Germany
| | - B. Zur
- Institute for Medical Biometry, Informatics and Epidemiology (IMBIE), Bonn, Germany
| | - C. P. Naehle
- Department of Radiology, University Hospital of Bonn, Bonn, Germany
- Department of Radiology, University Hospital of Cologne, Cologne, Germany
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Bain AR, Ainslie PN, Hoiland RL, Barak OF, Drvis I, Stembridge M, MacLeod DM, McEneny J, Stacey BS, Tuaillon E, Marchi N, Fayd'Herbe De Maudave A, Dujic Z, MacLeod DB, Bailey DM. Competitive apnea and its effect on the human brain: focus on the redox regulation of blood-brain barrier permeability and neuronal-parenchymal integrity. FASEB J 2018; 32:2305-2314. [PMID: 29191963 DOI: 10.1096/fj.201701031r] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Static apnea provides a unique model that combines transient hypertension, hypercapnia, and severe hypoxemia. With apnea durations exceeding 5 min, the purpose of the present study was to determine how that affects cerebral free-radical formation and the corresponding implications for brain structure and function. Measurements were obtained before and following a maximal apnea in 14 divers with transcerebral exchange kinetics, measured as the product of global cerebral blood flow (duplex ultrasound) and radial arterial to internal jugular venous concentration differences ( a-vD). Apnea increased the systemic (arterial) and, to a greater extent, the regional (jugular venous) concentration of the ascorbate free radical, resulting in a shift from net cerebral uptake to output ( P < 0.05). Peroxidation (lipid hydroperoxides, LDL oxidation), NO bioactivity, and S100β were correspondingly enhanced ( P < 0.05), the latter interpreted as minor and not a pathologic disruption of the blood-brain barrier. However, those changes were insufficient to cause neuronal-parenchymal damage confirmed by the lack of change in the a-vD of neuron-specific enolase and human myelin basic protein ( P > 0.05). Collectively, these observations suggest that increased cerebral oxidative stress following prolonged apnea in trained divers may reflect a functional physiologic response, rather than a purely maladaptive phenomenon.-Bain, A. R., Ainslie, P. N., Hoiland, R. L., Barak, O. F., Drvis, I., Stembridge, M., MacLeod, D. M., McEneny, J., Stacey, B. S., Tuaillon, E., Marchi, N., De Maudave, A. F., Dujic, Z., MacLeod, D. B., Bailey, D. M. Competitive apnea and its effect on the human brain: focus on the redox regulation of blood-brain barrier permeability and neuronal-parenchymal integrity.
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Affiliation(s)
- Anthony R Bain
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, British Columbia, Canada
- Integrative Physiology, University of Colorado, Boulder, Colorado, USA
| | - Philip N Ainslie
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, British Columbia, Canada
| | - Ryan L Hoiland
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, British Columbia, Canada
| | - Otto F Barak
- School of Medicine, University of Split, Split, Croatia
- Faculty of Medicine, University of Novi Sad, Novi Sad, Serbia
| | - Ivan Drvis
- School of Kinesiology, University of Zagreb, Zagreb, Croatia
| | - Mike Stembridge
- Cardiff Centre for Exercise & Health, Cardiff Metropolitan University, Cardiff, United Kingdom
| | | | - Jane McEneny
- Centre for Public Health, Queen's University Belfast, Belfast, Northern Ireland, United Kingdom
| | - Benjamin S Stacey
- Neurovascular Research Laboratory, Faculty of Life Sciences and Education, University of South Wales, Pontypridd, United Kingdom
| | - Eduoard Tuaillon
- Unit Mixte de Recherche (UMR), INSERM l'Etablissement Français du Sang (EFS), Université Montpellier 1, Montpellier, France
| | - Nicola Marchi
- UMR, Laboratory of Cerebrovascular Mechanisms of Brain Disorders, Department of Neuroscience, Centre National de la Recherche Scientifique (CNRS), INSERM, Institute of Functional Genomics, Montpellier, France; and
| | - Alexis Fayd'Herbe De Maudave
- UMR, Laboratory of Cerebrovascular Mechanisms of Brain Disorders, Department of Neuroscience, Centre National de la Recherche Scientifique (CNRS), INSERM, Institute of Functional Genomics, Montpellier, France; and
| | - Zeljko Dujic
- School of Medicine, University of Split, Split, Croatia
| | - David B MacLeod
- Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina, USA
| | - Damian M Bailey
- Neurovascular Research Laboratory, Faculty of Life Sciences and Education, University of South Wales, Pontypridd, United Kingdom
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Abstract
Breath-hold diving is practiced by recreational divers, seafood divers, military divers, and competitive athletes. It involves highly integrated physiology and extreme responses. This article reviews human breath-hold diving physiology beginning with an historical overview followed by a summary of foundational research and a survey of some contemporary issues. Immersion and cardiovascular adjustments promote a blood shift into the heart and chest vasculature. Autonomic responses include diving bradycardia, peripheral vasoconstriction, and splenic contraction, which help conserve oxygen. Competitive divers use a technique of lung hyperinflation that raises initial volume and airway pressure to facilitate longer apnea times and greater depths. Gas compression at depth leads to sequential alveolar collapse. Airway pressure decreases with depth and becomes negative relative to ambient due to limited chest compliance at low lung volumes, raising the risk of pulmonary injury called "squeeze," characterized by postdive coughing, wheezing, and hemoptysis. Hypoxia and hypercapnia influence the terminal breakpoint beyond which voluntary apnea cannot be sustained. Ascent blackout due to hypoxia is a danger during long breath-holds, and has become common amongst high-level competitors who can suppress their urge to breathe. Decompression sickness due to nitrogen accumulation causing bubble formation can occur after multiple repetitive dives, or after single deep dives during depth record attempts. Humans experience responses similar to those seen in diving mammals, but to a lesser degree. The deepest sled-assisted breath-hold dive was to 214 m. Factors that might determine ultimate human depth capabilities are discussed. © 2018 American Physiological Society. Compr Physiol 8:585-630, 2018.
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Magnani S, Mulliri G, Sainas G, Ghiani G, Pinna V, Sanna I, Crisafulli A, Tocco F. Occurrence of cardiac output decrease (via stroke volume) is more pronounced in women than in men during prolonged dry static apnea. J Appl Physiol (1985) 2018; 124:349-355. [DOI: 10.1152/japplphysiol.00991.2016] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Little is known about sex differences in autonomic cardiovascular regulation of the diving response, and the few available studies of these differences were conducted on subjects with limited or no diving experience. We examined the influence of sex on hemodynamics during dry static apnea (SA) in eight male and eight female elite divers matched for their breath hold (BH) ability. Hemodynamics was assessed by means of simultaneous echocardiography and impedance cardiography measurements, and arterial pressure and oxygen saturation ([Formula: see text]) were also collected. In the first quarter (AP25%) and half (AP50%) of apnea duration cardiac output (CO) showed a more rapid and intense decrease in women than in men (−43% vs. −17% during AP25% and −40% vs. −19% during AP50%, respectively, P < 0.05). At the same time points, systemic vascular resistance (SVR) increased more in women than in men (+22% vs. +100% at AP25% and +48% vs. +107% at AP50%, respectively, P < 0.05). [Formula: see text] progressively declined in both groups, but men showed a more pronounced decrease than women at the end of apneas (−13% vs. −5%, respectively, P < 0.05). In men the higher the body surface area values the longer the apnea, while in women the higher the SVR response the longer the apnea. In elite female divers, the magnitude of CO decrease during dry SA was larger than in male divers. The capacities to store oxygen and to reduce O2 consumption play a pivotal role in BH performance, but their extent seems to be different in the sexes. NEW & NOTEWORTHY This is the first study in which the influence of sex on hemodynamics during dry static apnea has been investigated in two groups of elite divers matched for their breath hold ability. We also show the correlation between the performances obtained by divers during a real competition and their anthropometric, respiratory, and cardiovascular characteristics.
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Affiliation(s)
- Sara Magnani
- Sport Physiology Laboratory, Department of Medical Sciences and Public Health, School of Sport Medicine, University of Cagliari, Cagliari, Italy
| | - Gabriele Mulliri
- Sport Physiology Laboratory, Department of Medical Sciences and Public Health, School of Sport Medicine, University of Cagliari, Cagliari, Italy
| | - Gianmarco Sainas
- Sport Physiology Laboratory, Department of Medical Sciences and Public Health, School of Sport Medicine, University of Cagliari, Cagliari, Italy
| | - Giovanna Ghiani
- Sport Physiology Laboratory, Department of Medical Sciences and Public Health, School of Sport Medicine, University of Cagliari, Cagliari, Italy
| | - Virginia Pinna
- Sport Physiology Laboratory, Department of Medical Sciences and Public Health, School of Sport Medicine, University of Cagliari, Cagliari, Italy
| | - Irene Sanna
- Sport Physiology Laboratory, Department of Medical Sciences and Public Health, School of Sport Medicine, University of Cagliari, Cagliari, Italy
| | - Antonio Crisafulli
- Sport Physiology Laboratory, Department of Medical Sciences and Public Health, School of Sport Medicine, University of Cagliari, Cagliari, Italy
| | - Filippo Tocco
- Sport Physiology Laboratory, Department of Medical Sciences and Public Health, School of Sport Medicine, University of Cagliari, Cagliari, Italy
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Badrov MB, Barak OF, Mijacika T, Shoemaker LN, Borrell LJ, Lojpur M, Drvis I, Dujic Z, Shoemaker JK. Ventilation inhibits sympathetic action potential recruitment even during severe chemoreflex stress. J Neurophysiol 2017; 118:2914-2924. [PMID: 28835525 PMCID: PMC5686238 DOI: 10.1152/jn.00381.2017] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Revised: 08/18/2017] [Accepted: 08/21/2017] [Indexed: 01/26/2023] Open
Abstract
This study investigated the influence of ventilation on sympathetic action potential (AP) discharge patterns during varying levels of high chemoreflex stress. In seven trained breath-hold divers (age 33 ± 12 yr), we measured muscle sympathetic nerve activity (MSNA) at baseline, during preparatory rebreathing (RBR), and during 1) functional residual capacity apnea (FRCApnea) and 2) continued RBR. Data from RBR were analyzed at matched (i.e., to FRCApnea) hemoglobin saturation (HbSat) levels (RBRMatched) or more severe levels (RBREnd). A third protocol compared alternating periods (30 s) of FRC and RBR (FRC-RBRALT). Subjects continued each protocol until 85% volitional tolerance. AP patterns in MSNA (i.e., providing the true neural content of each sympathetic burst) were studied using wavelet-based methodology. First, for similar levels of chemoreflex stress (both HbSat: 71 ± 6%; P = NS), RBRMatched was associated with reduced AP frequency and APs per burst compared with FRCApnea (both P < 0.001). When APs were binned according to peak-to-peak amplitude (i.e., into clusters), total AP clusters increased during FRCApnea (+10 ± 2; P < 0.001) but not during RBRMatched (+1 ± 2; P = NS). Second, despite more severe chemoreflex stress during RBREnd (HbSat: 56 ± 13 vs. 71 ± 6%; P < 0.001), RBREnd was associated with a restrained increase in the APs per burst (FRCApnea: +18 ± 7; RBREnd: +11 ± 5) and total AP clusters (FRCApnea: +10 ± 2; RBREnd: +6 ± 4) (both P < 0.01). During FRC-RBRALT, all periods of FRC elicited sympathetic AP recruitment (all P < 0.001), whereas all periods of RBR were associated with complete withdrawal of AP recruitment (all P = NS). Presently, we demonstrate that ventilation per se restrains and/or inhibits sympathetic axonal recruitment during high, and even extreme, chemoreflex stress.NEW & NOTEWORTHY The current study demonstrates that the sympathetic neural recruitment patterns observed during chemoreflex activation induced by rebreathing or apnea are restrained and/or inhibited by the act of ventilation per se, despite similar, or even greater, levels of severe chemoreflex stress. Therefore, ventilation modulates not only the timing of sympathetic bursts but also the within-burst axonal recruitment normally observed during progressive chemoreflex stress.
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Affiliation(s)
- Mark B Badrov
- School of Kinesiology, Western University, London, Ontario, Canada
| | - Otto F Barak
- Department of Physiology, University of Split School of Medicine, Split, Croatia.,Faculty of Medicine, University of Novi Sad, Novi Sad, Serbia
| | - Tanja Mijacika
- Department of Physiology, University of Split School of Medicine, Split, Croatia
| | | | | | - Mihajlo Lojpur
- Department of Physiology, University of Split School of Medicine, Split, Croatia
| | - Ivan Drvis
- Faculty of Kinesiology, University of Zagreb, Zagreb, Croatia; and
| | - Zeljko Dujic
- Department of Physiology, University of Split School of Medicine, Split, Croatia
| | - J Kevin Shoemaker
- School of Kinesiology, Western University, London, Ontario, Canada; .,Department of Physiology and Pharmacology, Western University, London, Ontario, Canada
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47
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Mijacika T, Kyhl K, Frestad D, Otto Barak F, Drvis I, Secher NH, Dujic Z, Lav Madsen P. Effect of pulmonary hyperinflation on central blood volume: An MRI study. Respir Physiol Neurobiol 2017; 243:92-96. [PMID: 28583413 DOI: 10.1016/j.resp.2017.05.012] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2017] [Accepted: 05/31/2017] [Indexed: 11/25/2022]
Abstract
Pulmonary hyperinflation attained by glossopharyngeal insufflation (GPI) challenges the circulation by compressing the heart and pulmonary vasculature. Our aim was to determine the amount of blood translocated from the central blood volume during GPI. Cardiac output and cardiac chamber volumes were assessed by magnetic resonance imaging in twelve breath-hold divers at rest and during apnea with GPI. Pulmonary blood volume was determined from pulmonary blood flow and transit times for gadolinium during first-pass perfusion after intravenous injection. During GPI, the lung volume increased by 0.8±0.6L (11±7%) above the total lung capacity. All cardiac chambers decreased in volume and despite a heart rate increase of 24±29 bpm (39±50%), pulmonary blood flow decreased by 2783±1820mL (43±20%). The pulmonary transit time remained unchanged at 7.5±2.2s and pulmonary blood volume decreased by 354±176mL (47±15%). In total, central blood volume decreased by 532±248mL (46±14%). Voluntary pulmonary hyperinflation leads to ∼50% decrease in pulmonary and central blood volume.
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Affiliation(s)
- Tanja Mijacika
- Dept. of Integrative Physiology, University of Split School of Medicine, Croatia
| | - Kasper Kyhl
- The Cardiac MRI group, Dept. Cardiology, Rigshospitalet, University of Copenhagen, Denmark
| | - Daria Frestad
- Dept. of Cardiology, Copenhagen University Hospital, Hvidovre, University of Copenhagen, Denmark
| | - F Otto Barak
- Dept. of Integrative Physiology, University of Split School of Medicine, Croatia; Dept. of Physiology, Faculty of Medicine, University of Novi Sad, Serbia
| | - Ivan Drvis
- University of Zagreb Faculty of Kinesiology, Croatia
| | - Niels H Secher
- Dept. of Anesthesiology, The Copenhagen Muscle Research Center, Rigshospitalet, University of Copenhagen, Denmark
| | - Zeljko Dujic
- Dept. of Integrative Physiology, University of Split School of Medicine, Croatia.
| | - Per Lav Madsen
- Dept. of Cardiology, Copenhagen University Hospital, Herlev, University of Copenhagen, Denmark
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Eichhorn L, Dolscheid-Pommerich R, Erdfelder F, Ayub MA, Schmitz T, Werner N, Jansen F. Sustained apnea induces endothelial activation. Clin Cardiol 2017; 40:704-709. [PMID: 28464406 DOI: 10.1002/clc.22720] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/19/2017] [Revised: 03/28/2017] [Accepted: 03/30/2017] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND Apnea diving has gained worldwide popularity, even though the pathophysiological consequences of this challenging sport on the human body are poorly investigated and understood. This study aims to assess the influence of sustained apnea in healthy volunteers on circulating microparticles (MPs) and microRNAs (miRs), which are established biomarkers reflecting vascular function. HYPOTHESIS Short intermittent hypoxia due to voluntary breath-holding affects circulating levels of endothelial cell-derived MPs (EMPs) and endothelial cell-derived miRs. METHODS Under dry laboratory conditions, 10 trained apneic divers performed maximal breath-hold. Venous blood samples were taken, once before and at 4 defined points in time after apnea. Samples were analyzed for circulating EMPs and endothelial miRs. RESULTS Average apnea time was 329 seconds (±103), and SpO2 at the end of apnea was 79% (±12). Apnea was associated with a time-dependent increase of circulating endothelial cell-derived EMPs and endothelial miRs. Levels of circulating EMPs in the bloodstream reached a peak 4 hours after the apnea period and returned to baseline levels after 24 hours. Circulating miR-126 levels were elevated at all time points after a single voluntary maximal apnea, whereas miR-26 levels were elevated significantly only after 30 minutes and 4 hours. Also miR-21 and miR-92 levels increased, but did not reach the level of significance. CONCLUSIONS Even a single maximal breath-hold induces acute endothelial activation and should be performed with great caution by subjects with preexisting vascular diseases. Voluntary apnea might be used as a model to simulate changes in endothelial function caused by hypoxia in humans.
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Affiliation(s)
- Lars Eichhorn
- Department of Anesthesiology and Intensive Care Medicine, University Hospital of Bonn, Bonn, Germany
| | | | - Felix Erdfelder
- Department of Anesthesiology and Intensive Care Medicine, University Hospital of Bonn, Bonn, Germany
| | | | - Theresa Schmitz
- Department of Medicine II, Heart Center Bonn, University Hospital of Bonn, Bonn, Germany
| | - Nikos Werner
- Department of Medicine II, Heart Center Bonn, University Hospital of Bonn, Bonn, Germany
| | - Felix Jansen
- Department of Medicine II, Heart Center Bonn, University Hospital of Bonn, Bonn, Germany
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49
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Mijacika T, Dujic Z. Sports-related lung injury during breath-hold diving. Eur Respir Rev 2017; 25:506-512. [PMID: 27903671 DOI: 10.1183/16000617.0052-2016] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2016] [Accepted: 07/01/2016] [Indexed: 12/19/2022] Open
Abstract
The number of people practising recreational breath-hold diving is constantly growing, thereby increasing the need for knowledge of the acute and chronic effects such a sport could have on the health of participants. Breath-hold diving is potentially dangerous, mainly because of associated extreme environmental factors such as increased hydrostatic pressure, hypoxia, hypercapnia, hypothermia and strenuous exercise.In this article we focus on the effects of breath-hold diving on pulmonary function. Respiratory symptoms have been reported in almost 25% of breath-hold divers after repetitive diving sessions. Acutely, repetitive breath-hold diving may result in increased transpulmonary capillary pressure, leading to noncardiogenic oedema and/or alveolar haemorrhage. Furthermore, during a breath-hold dive, the chest and lungs are compressed by the increasing pressure of water. Rapid changes in lung air volume during descent or ascent can result in a lung injury known as pulmonary barotrauma. Factors that may influence individual susceptibility to breath-hold diving-induced lung injury range from underlying pulmonary or cardiac dysfunction to genetic predisposition.According to the available data, breath-holding does not result in chronic lung injury. However, studies of large populations of breath-hold divers are necessary to firmly exclude long-term lung damage.
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Affiliation(s)
- Tanja Mijacika
- Dept of Integrative Physiology, University of Split School of Medicine, Split, Croatia
| | - Zeljko Dujic
- Dept of Integrative Physiology, University of Split School of Medicine, Split, Croatia
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50
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Bierens JJLM, Lunetta P, Tipton M, Warner DS. Physiology Of Drowning: A Review. Physiology (Bethesda) 2017; 31:147-66. [PMID: 26889019 DOI: 10.1152/physiol.00002.2015] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Drowning physiology relates to two different events: immersion (upper airway above water) and submersion (upper airway under water). Immersion involves integrated cardiorespiratory responses to skin and deep body temperature, including cold shock, physical incapacitation, and hypovolemia, as precursors of collapse and submersion. The physiology of submersion includes fear of drowning, diving response, autonomic conflict, upper airway reflexes, water aspiration and swallowing, emesis, and electrolyte disorders. Submersion outcome is determined by cardiac, pulmonary, and neurological injury. Knowledge of drowning physiology is scarce. Better understanding may identify methods to improve survival, particularly related to hot-water immersion, cold shock, cold-induced physical incapacitation, and fear of drowning.
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Affiliation(s)
| | - Philippe Lunetta
- Department of Pathology and Forensic Medicine, University of Turku, Turku, Finland
| | - Mike Tipton
- Department of Sport and Exercise Science, Extreme Environments Laboratory, University of Portsmouth, Portsmouth, United Kingdom; and
| | - David S Warner
- Departments of Anesthesiology, Neurobiology and Surgery, Duke University Medical Center, Durham, North Carolina
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