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Elia A, Gennser M, Eiken O, Keramidas ME. Effects of hyperventilation on repeated breath-holding while in a fasting state: do risks outweigh the benefits? Am J Physiol Regul Integr Comp Physiol 2024; 326:R319-R329. [PMID: 38314699 DOI: 10.1152/ajpregu.00260.2023] [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: 11/18/2023] [Revised: 01/30/2024] [Accepted: 01/30/2024] [Indexed: 02/07/2024]
Abstract
Breath-holding preceded by either an overnight fast or hyperventilation has been shown to potentiate the risk of a hypoxic blackout. However, no study has explored the combined effects of fasting and hyperventilation on apneic performance and associated physiological responses. Nine nondivers (8 males) attended the laboratory on two separate occasions (≥48 h apart), both after a 12-h overnight fast. During each visit, a hyperoxic rebreathing trial was performed followed by three repeated maximal static apneas preceded by either normal breathing (NORM) or a 30-s hyperventilation (HYPER). Splenic volume, hematology, cardiovascular, and respiratory variables were monitored. There were no interprotocol differences at rest or during hyperoxic rebreathing for any variable (P ≥ 0.09). On nine occasions (8 in HYPER), the subjects reached our safety threshold (oxygen saturation 65%) and were asked to abort their apneas, with the preponderance of these incidents (6 of 9) occurring during the third repetition. Across the sequential attempts, longer apneas were recorded in HYPER [median(range), 220(123-324) s vs. 185(78-296) s, P ≤ 0.001], with involuntary breathing movements occurring later [134(65-234) s vs. 97(42-200) s, P ≤ 0.001] and end-apneic partial end-tidal pressures of oxygen (P ET O 2 ) being lower (P ≤ 0.02). During the final repetition, partial end-tidal pressure of carbon dioxide [(P ET CO 2 ), 6.53 ± 0.46 kPa vs. 6.01 ± 0.45 kPa, P = 0.005] was lower in HYPER. Over the serial attempts, preapneic tidal volume was gradually elevated [from apnea 1 to 3, by 0.26 ± 0.24 L (HYPER) and 0.28 ± 0.30 L (NORM), P ≤ 0.025], with a correlation noted with preapneic P ET CO 2 (r = -0.57, P < 0.001) and P ET O 2 (r = 0.76, P < 0.001), respectively. In a fasted state, preapnea hyperventilation compared with normal breathing leads to longer apneas but may increase the susceptibility to a hypoxic blackout.NEW & NOTEWORTHY This study shows that breath-holds (apneas) preceded by a 12-h overnight fast coupled with a 30-s hyperventilation as opposed to normal breathing may increase the likelihood of a hypoxic blackout through delaying the excitation of hypercapnic ventilatory sensory chemoreflexes. Evidently, this risk is exacerbated over a series of repeated maximal attempts, possibly due to a shift in preapneic gas tensions facilitated by an unintentional increase in tidal volume breathing.
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Affiliation(s)
- Antonis Elia
- Division of Environmental Physiology, Swedish Aerospace Physiology Centre, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Mikael Gennser
- Division of Environmental Physiology, Swedish Aerospace Physiology Centre, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Ola Eiken
- Division of Environmental Physiology, Swedish Aerospace Physiology Centre, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Michail E Keramidas
- Division of Environmental Physiology, Swedish Aerospace Physiology Centre, KTH Royal Institute of Technology, Stockholm, Sweden
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2
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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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3
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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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4
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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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5
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Piedimonte A, Barbiani D, Benedetti F, Zamfira DA, Carlino E. The placebo effect in breath holding: a preliminary behavioral investigation. Neurosci Lett 2020; 739:135434. [PMID: 33091438 DOI: 10.1016/j.neulet.2020.135434] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Revised: 10/13/2020] [Accepted: 10/14/2020] [Indexed: 11/28/2022]
Abstract
PURPOSE This study seeks to evaluate effects of expectations and conditioning on dry breath holding. METHODS Sixty healthy volunteers were subdivided into 3 groups and were tested across 4 breath holding trials. Participants of the Control group (C) did not undergo any manipulation. Participants of the placebo (P) and nocebo (N) groups were told that they would inhale O2 (actually sham O2) or CO2 (actually sham CO2) along with opposite information that this would enhance or worsen their breath holding time, respectively. Opposite conditioning paradigms based on false visual feedback were employed to reinforce participants' positive (placebo) and negative (nocebo) beliefs. RESULTS The P group showed the greater increase in breath holding time from baseline to the last trial (p = 0.0001) and the longest breath holding time in the last trial compared to the C group (p = 0.02) and the N group (p = 0.0001). Additionally, in the last trial the P group showed a greater decrease in peripheral oxygen saturation (SpO2) as compared to the C group (p = 0.04) and the N group (p = 0.001). Heart rate (HR) was accelerated in the N group during breath holding (in comparison to the P group [p = 0.04] and C group [p = 0.04]). CONCLUSIONS Psychological components can affect behavioral and physiological parameters in breath holding. This study may inform future research about the role of placebo and nocebo effects for conditions in which critical functions are at play.
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Affiliation(s)
| | - Diletta Barbiani
- Department of Neuroscience "Rita Levi Montalcini", University of Turin, Italy
| | - Fabrizio Benedetti
- Department of Neuroscience "Rita Levi Montalcini", University of Turin, Italy; Medicine & Physiology of Hypoxia, Plateau Rosa Laboratories, Breuil-Cervinia, Italy, Zermatt, Switzerland
| | | | - Elisa Carlino
- Department of Neuroscience "Rita Levi Montalcini", University of Turin, Italy.
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Aldossary HS, Alzahrani AA, Nathanael D, Alhuthail EA, Ray CJ, Batis N, Kumar P, Coney AM, Holmes AP. G-Protein-Coupled Receptor (GPCR) Signaling in the Carotid Body: Roles in Hypoxia and Cardiovascular and Respiratory Disease. Int J Mol Sci 2020; 21:ijms21176012. [PMID: 32825527 PMCID: PMC7503665 DOI: 10.3390/ijms21176012] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2020] [Revised: 08/13/2020] [Accepted: 08/16/2020] [Indexed: 12/17/2022] Open
Abstract
The carotid body (CB) is an important organ located at the carotid bifurcation that constantly monitors the blood supplying the brain. During hypoxia, the CB immediately triggers an alarm in the form of nerve impulses sent to the brain. This activates protective reflexes including hyperventilation, tachycardia and vasoconstriction, to ensure blood and oxygen delivery to the brain and vital organs. However, in certain conditions, including obstructive sleep apnea, heart failure and essential/spontaneous hypertension, the CB becomes hyperactive, promoting neurogenic hypertension and arrhythmia. G-protein-coupled receptors (GPCRs) are very highly expressed in the CB and have key roles in mediating baseline CB activity and hypoxic sensitivity. Here, we provide a brief overview of the numerous GPCRs that are expressed in the CB, their mechanism of action and downstream effects. Furthermore, we will address how these GPCRs and signaling pathways may contribute to CB hyperactivity and cardiovascular and respiratory disease. GPCRs are a major target for drug discovery development. This information highlights specific GPCRs that could be targeted by novel or existing drugs to enable more personalized treatment of CB-mediated cardiovascular and respiratory disease.
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Affiliation(s)
- Hayyaf S. Aldossary
- Institute of Clinical Sciences, University of Birmingham, Birmingham B15 2TT, UK; (H.S.A.); (A.A.A.); (D.N.); (E.A.A.); (C.J.R.); (P.K.); (A.M.C.)
- College of Medicine, Basic Medical Sciences, King Saud bin Abdulaziz University for Health Sciences, Riyadh 11481, Saudi Arabia
| | - Abdulaziz A. Alzahrani
- Institute of Clinical Sciences, University of Birmingham, Birmingham B15 2TT, UK; (H.S.A.); (A.A.A.); (D.N.); (E.A.A.); (C.J.R.); (P.K.); (A.M.C.)
- Respiratory Care Department, Faculty of Applied Medical Sciences, Umm Al-Qura University, Makkah 24381, Saudi Arabia
| | - Demitris Nathanael
- Institute of Clinical Sciences, University of Birmingham, Birmingham B15 2TT, UK; (H.S.A.); (A.A.A.); (D.N.); (E.A.A.); (C.J.R.); (P.K.); (A.M.C.)
| | - Eyas A. Alhuthail
- Institute of Clinical Sciences, University of Birmingham, Birmingham B15 2TT, UK; (H.S.A.); (A.A.A.); (D.N.); (E.A.A.); (C.J.R.); (P.K.); (A.M.C.)
- Collage of Sciences and Health Professions, Basic Sciences Department, King Saud bin Abdulaziz University for Health Sciences, Riyadh 11481, Saudi Arabia
| | - Clare J. Ray
- Institute of Clinical Sciences, University of Birmingham, Birmingham B15 2TT, UK; (H.S.A.); (A.A.A.); (D.N.); (E.A.A.); (C.J.R.); (P.K.); (A.M.C.)
| | - Nikolaos Batis
- Institute of Cancer and Genomic Sciences, University of Birmingham, Birmingham B15 2TT, UK;
| | - Prem Kumar
- Institute of Clinical Sciences, University of Birmingham, Birmingham B15 2TT, UK; (H.S.A.); (A.A.A.); (D.N.); (E.A.A.); (C.J.R.); (P.K.); (A.M.C.)
| | - Andrew M. Coney
- Institute of Clinical Sciences, University of Birmingham, Birmingham B15 2TT, UK; (H.S.A.); (A.A.A.); (D.N.); (E.A.A.); (C.J.R.); (P.K.); (A.M.C.)
| | - Andrew P. Holmes
- Institute of Clinical Sciences, University of Birmingham, Birmingham B15 2TT, UK; (H.S.A.); (A.A.A.); (D.N.); (E.A.A.); (C.J.R.); (P.K.); (A.M.C.)
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham B15 2TT, UK
- Correspondence: ; Tel.: +44-121-415-8161
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7
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Costalat G, Godin B, Balmain BN, Moreau C, Brotherton E, Billaut F, Lemaitre F. Autonomic regulation of the heart and arrhythmogenesis in trained breath-hold divers. Eur J Sport Sci 2020; 21:439-449. [PMID: 32223533 DOI: 10.1080/17461391.2020.1749313] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
AbstractBreath-hold divers are known to develop cardiac autonomic changes and brady-arrthymias during prolonged breath-holding (BH). The effects of BH-induced hypoxemia were investigated upon both cardiac autonomic status and arrhythmogenesis by comparing breath-hold divers (BHDs) to non-divers (NDs). Eighteen participants (9 BHDs, 9 NDs) performed a maximal voluntary BH with face immersion. BHDs were asked to perform an additional BH at water surface to increase the degree of hypoxemia. Beat-to-beat changes in heart rate (HR), short-term fractal scaling exponent (DFAα1), the number of arrhythmic events [premature ventricular contractions (PVCs), premature atrial contractions (PACs)] and peripheral oxygen saturation (SpO2) were recorded during and immediately following BH. The corrected QT-intervals (QTc) were analyzed pre- and post-acute BH. A regression-based model was used to split BH into a normoxic (NX) and a hypoxemic phase (HX). During the HX phase of BH, BHDs showed a progressive decrease in DFAα1 during BH with face immersion (p < 0.01) and BH with whole-body immersion (p < 0.01) whereas NDs did not (p > 0.05). In addition, BHDs had more arrhythmic events during the HX of BH with whole-body immersion when compared to the corresponding NX phase (5.9 ± 6.7 vs 0.4 ± 1.3; p < 0.05; respectively). The number of PVCs was negatively correlated with SpO2 during BH with whole-body immersion (r = -0.72; p < 0.05). The hypoxemic stage of voluntary BH is concomitant with significant cardiac autonomic changes toward a synergistic sympathetic and parasympathetic stimulation. Co-activation led ultimately to increased bradycardic response and cardiac electrophysiological disturbances.
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Affiliation(s)
- Guillaume Costalat
- Faculty of Sport Sciences, APERE laboratory, EA 3300, University of Picardie Jules Verne, France
| | | | - Bryce N Balmain
- School of Allied Health Sciences, Griffith University, Gold Coast, Queensland, Australia
| | - Clara Moreau
- CHU Sainte Justine - Brain and Child Development, University of Montreal, Canada
| | - Emily Brotherton
- School of Allied Health Sciences, Griffith University, Gold Coast, Queensland, Australia
| | - Francois Billaut
- Département de kinésiologie, Faculté de Médecine, Université Laval, Québec, Canada
| | - Frederic Lemaitre
- Faculty of Sport Sciences, CETAPS laboratory, EA 3832, Normandy University, France
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8
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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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9
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Steinberg F, Doppelmayr M. Neurocognitive Markers During Prolonged Breath-Holding in Freedivers: An Event-Related EEG Study. Front Physiol 2019; 10:69. [PMID: 30792665 PMCID: PMC6374628 DOI: 10.3389/fphys.2019.00069] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2018] [Accepted: 01/21/2019] [Indexed: 01/16/2023] Open
Abstract
Since little is known concerning the psychological, cognitive, and neurophysiological factors that are involved in and important for phases of prolonged breath-holding (pBH) in freedivers, the present study uses electroencephalography (EEG) to investigate event-related neurocognitive markers during pBH of experienced freedivers that regularly train pBH. The purpose was to determine whether the well-known neurophysiological modulations elicited by hypoxic and hypercapnic conditions can also be detected during pBH induced hypoxic hypercapnia. Ten experienced free-divers (all male, aged 35.10 ± 7.89 years) were asked to hold their breath twice for 4 min per instance. During the first pBH, a checker board reversal task was presented and in the second four-min pBH phase a classical visual oddball paradigm was performed. A visual evoked potential (VEP) as an index of early visual processing (i.e., latencies and amplitudes of N75, P100, and N145) and the latency and amplitude of a P300 component (visual oddball paradigm) as an index of cognitive processing were investigated. In a counter-balanced cross-over design, all tasks were once performed during normal breathing (B), and once during pBH. All components were then compared between an early pBH (0–2 min) and a later pBH stage (2–4 min) and with the same time phases without pBH (i.e., during normal breathing). Statistical analyses using analyses of variance (ANOVA) revealed that comparisons between B and pBH yielded no significant changes either in the amplitude and latency of the VEP or in the P300. This indicates that neurocognitive markers, whether in an early visual processing stream or at a later cognitive processing stage, were not affected by pBH in experienced free-divers.
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Affiliation(s)
- Fabian Steinberg
- Department of Sport Psychology, Institute of Sport Science, Johannes Gutenberg-University Mainz, Mainz, Germany
| | - Michael Doppelmayr
- Department of Sport Psychology, Institute of Sport Science, Johannes Gutenberg-University Mainz, Mainz, Germany.,Centre of Cognitive Neuroscience, University of Salzburg, Salzburg, Austria
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10
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Stembridge M, Hoiland RL, Bain AR, Barak OF, Drvis I, MacLeod DB, MacLeod DM, Madden D, Batinic T, O'Donoghue P, Shave R, Dujic Z, Ainslie PN. Influence of lung volume on the interaction between cardiac output and cerebrovascular regulation during extreme apnoea. Exp Physiol 2018; 102:1288-1299. [PMID: 28762565 DOI: 10.1113/ep086429] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2017] [Accepted: 07/20/2017] [Indexed: 12/12/2022]
Abstract
NEW FINDINGS What is the central question of this study? Does the reduction in cardiac output observed during extreme voluntary apnoea, secondary to high lung volume, result in a reduction in cerebral blood flow, perfusion pressure and oxygen delivery in a group of elite free divers? What is the main finding and its importance? High lung volumes reduce cardiac output and ventricular filling during extreme apnoea, but changes in cerebral blood flow are observed only transiently during the early stages of apnoea. This reveals that whilst cardiac output is important in regulating cerebral haemodynamics, the role of mean arterial pressure in restoring cerebral perfusion pressure is of greater significance to the regulation of cerebral blood flow. We investigated the role of lung volume-induced changes in cardiac output (Q̇) on cerebrovascular regulation during prolonged apnoea. Fifteen elite apnoea divers (one female; 185 ± 7 cm, 82 ± 12 kg, 29 ± 7 years old) attended the laboratory on two separate occasions and completed maximal breath-holds at total lung capacity (TLC) and functional residual capacity (FRC) to elicit disparate cardiovascular responses. Mean arterial pressure (MAP), internal jugular venous pressure and arterial blood gases were measured via cannulation. Global cerebral blood flow was quantified by ultrasound and cardiac output was quantified by via photoplethysmography. At FRC, stroke volume and Q̇ did not change from baseline (P > 0.05). In contrast, during the TLC trial stroke volume and Q̇ were decreased until 80 and 40% of apnoea, respectively (P < 0.05). During the TLC trial, global cerebral blood flow was significantly lower at 20%, but subsequently increased so that cerebral oxygen delivery was comparable to that during the FRC trial. Internal jugular venous pressure was significantly higher throughout the TLC trial in comparison to FRC. The MAP increased progressively in both trials but to a greater extent at TLC, resulting in a comparable cerebral perfusion pressure between trials by the end of apnoea. In summary, although lung volume has a profound effect on Q̇ during prolonged breath-holding, these changes do not translate to the cerebrovasculature owing to the greater sensitivity of cerebral blood flow to arterial blood gases and MAP; regulatory mechanisms that facilitate the maintenance of cerebral oxygen delivery.
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Affiliation(s)
- Mike Stembridge
- Cardiff Centre for Exercise and Health, Cardiff Metropolitan University, Cardiff, UK
| | - Ryan L Hoiland
- Centre for Heart Lung and Vascular Health, University of British Columbia, Kelowna, BC, Canada
| | - Anthony R Bain
- Centre for Heart Lung and Vascular Health, University of British Columbia, Kelowna, BC, 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
| | - David B MacLeod
- Department of Anesthesiology, Duke University Medical Center, Durham, NC, USA
| | | | - Dennis Madden
- School of Medicine, University of Split, Split, Croatia
| | - Tonci Batinic
- School of Medicine, University of Split, Split, Croatia
| | - Peter O'Donoghue
- Cardiff Centre for Exercise and Health, Cardiff Metropolitan University, Cardiff, UK
| | - Rob Shave
- Cardiff Centre for Exercise and Health, Cardiff Metropolitan University, Cardiff, UK
| | - Zeljko Dujic
- School of Medicine, University of Split, Split, Croatia
| | - Philip N Ainslie
- Centre for Heart Lung and Vascular Health, University of British Columbia, Kelowna, BC, Canada
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11
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Bain AR, Ainslie PN, Barak OF, Hoiland RL, Drvis I, Mijacika T, Bailey DM, Santoro A, DeMasi DK, Dujic Z, MacLeod DB. Hypercapnia is essential to reduce the cerebral oxidative metabolism during extreme apnea in humans. J Cereb Blood Flow Metab 2017; 37:3231-3242. [PMID: 28071964 PMCID: PMC5584699 DOI: 10.1177/0271678x16686093] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The cerebral metabolic rate of oxygen (CMRO2) is reduced during apnea that yields profound hypoxia and hypercapnia. In this study, to dissociate the impact of hypoxia and hypercapnia on the reduction in CMRO2, 11 breath-hold competitors completed three apneas under: (a) normal conditions (NM), yielding severe hypercapnia and hypoxemia, (b) with prior hyperventilation (HV), yielding severe hypoxemia only, and (c) with prior 100% oxygen breathing (HX), yielding the greatest level of hypercapnia, but in the absence of hypoxemia. The CMRO2 was calculated from the product of cerebral blood flow (ultrasound) and the radial artery-jugular venous oxygen content difference (cannulation). Secondary measures included net-cerebral glucose/lactate exchange and nonoxidative metabolism. Reductions in CMRO2 were largest in the HX condition (-44 ± 15%, p < 0.05), with the most severe hypercapnia (PaCO2 = 58 ± 5 mmHg) but maintained oxygen saturation. The CMRO2 was reduced by 24 ± 27% in NM ( p = 0.05), but unchanged in the HV apnea where hypercapnia was absent. A net-cerebral lactate release was observed at the end of apnea in the HV and NM condition, but not in the HX apnea (main effect p < 0.05). These novel data support hypercapnia/pH as a key mechanism mediating reductions in CMRO2 during apnea, and show that severe hypoxemia stimulates lactate release from the brain.
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Affiliation(s)
- Anthony R Bain
- 1 Centre for Heart Lung and Vascular Health, University of British Columbia, Kelowna, BC, Canada
| | - Philip N Ainslie
- 1 Centre for Heart Lung and Vascular Health, University of British Columbia, Kelowna, BC, Canada
| | - Otto F Barak
- 2 School of Medicine, University of Split, Split, Croatia
| | | | - Ivan Drvis
- 4 School of Kinesiology, University of Zagreb, Zagreb, Croatia
| | - Tanja Mijacika
- 2 School of Medicine, University of Split, Split, Croatia
| | - Damian M Bailey
- 5 Faculty of Life Sciences and Education, University of South Wales, Glamorgan, UK
| | | | | | - Zeljko Dujic
- 2 School of Medicine, University of Split, Split, Croatia
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12
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Ortega-Sáenz P, Macías D, Levitsky KL, Rodríguez-Gómez JA, González-Rodríguez P, Bonilla-Henao V, Arias-Mayenco I, López-Barneo J. Selective accumulation of biotin in arterial chemoreceptors: requirement for carotid body exocytotic dopamine secretion. J Physiol 2016; 594:7229-7248. [PMID: 27570189 DOI: 10.1113/jp272961] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2016] [Accepted: 08/17/2016] [Indexed: 01/01/2023] Open
Abstract
KEY POINTS Biotin, a vitamin whose main role is as a coenzyme for carboxylases, accumulates at unusually large amounts within cells of the carotid body (CB). In biotin-deficient rats biotin rapidly disappears from the blood; however, it remains at relatively high levels in CB glomus cells. The CB contains high levels of mRNA for SLC5a6, a biotin transporter, and SLC19a3, a thiamine transporter regulated by biotin. Animals with biotin deficiency exhibit pronounced metabolic lactic acidosis. Remarkably, glomus cells from these animals have normal electrical and neurochemical properties. However, they show a marked decrease in the size of quantal dopaminergic secretory events. Inhibitors of the vesicular monoamine transporter 2 (VMAT2) mimic the effect of biotin deficiency. In biotin-deficient animals, VMAT2 protein expression decreases in parallel with biotin depletion in CB cells. These data suggest that dopamine transport and/or storage in small secretory granules in glomus cells depend on biotin. ABSTRACT Biotin is a water-soluble vitamin required for the function of carboxylases as well as for the regulation of gene expression. Here, we report that biotin accumulates in unusually large amounts in cells of arterial chemoreceptors, carotid body (CB) and adrenal medulla (AM). We show in a biotin-deficient rat model that the vitamin rapidly disappears from the blood and other tissues (including the AM), while remaining at relatively high levels in the CB. We have also observed that, in comparison with other peripheral neural tissues, CB cells contain high levels of SLC5a6, a biotin transporter, and SLC19a3, a thiamine transporter regulated by biotin. Biotin-deficient rats show a syndrome characterized by marked weight loss, metabolic lactic acidosis, aciduria and accelerated breathing with normal responsiveness to hypoxia. Remarkably, CB cells from biotin-deficient animals have normal electrophysiological and neurochemical (ATP levels and catecholamine synthesis) properties; however, they exhibit a marked decrease in the size of quantal catecholaminergic secretory events, which is not seen in AM cells. A similar differential secretory dysfunction is observed in CB cells treated with tetrabenazine, a selective inhibitor of the vesicular monoamine transporter 2 (VMAT2). VMAT2 is highly expressed in glomus cells (in comparison with VMAT1), and in biotin-deficient animals VMAT2 protein expression decreases in parallel with the decrease of biotin accumulated in CB cells. These data suggest that biotin has an essential role in the homeostasis of dopaminergic transmission modulating the transport and/or storage of transmitters within small secretory granules in glomus cells.
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Affiliation(s)
- Patricia Ortega-Sáenz
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Spain.,Departamento de Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Spain.,Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Spain
| | - David Macías
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Spain
| | - Konstantin L Levitsky
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Spain
| | - José A Rodríguez-Gómez
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Spain.,Departamento de Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Spain
| | - Patricia González-Rodríguez
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Spain.,Departamento de Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Spain.,Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Spain
| | - Victoria Bonilla-Henao
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Spain.,Departamento de Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Spain.,Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Spain
| | - Ignacio Arias-Mayenco
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Spain.,Departamento de Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Spain.,Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Spain
| | - José López-Barneo
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Spain.,Departamento de Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Spain.,Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Spain
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13
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Bain AR, Ainslie PN, Hoiland RL, Barak OF, Cavar M, Drvis I, Stembridge M, MacLeod DM, Bailey DM, Dujic Z, MacLeod DB. Cerebral oxidative metabolism is decreased with extreme apnoea in humans; impact of hypercapnia. J Physiol 2016; 594:5317-28. [PMID: 27256521 DOI: 10.1113/jp272404] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2016] [Accepted: 05/18/2016] [Indexed: 12/25/2022] Open
Abstract
KEY POINTS The present study describes the cerebral oxidative and non-oxidative metabolism in man during a prolonged apnoea (ranging from 3 min 36 s to 7 min 26 s) that generates extremely low levels of blood oxygen and high levels of carbon dioxide. The cerebral oxidative metabolism, measured from the product of cerebral blood flow and the radial artery-jugular venous oxygen content difference, was reduced by ∼29% at the termination of apnoea, although there was no change in the non-oxidative metabolism. A subset study with mild and severe hypercapnic breathing at the same level of hypoxia suggests that hypercapnia can partly explain the cerebral metabolic reduction near the apnoea breakpoint. A hypercapnia-induced oxygen-conserving response may protect the brain against severe oxygen deprivation associated with prolonged apnoea. ABSTRACT Prolonged apnoea in humans is reflected in progressive hypoxaemia and hypercapnia. In the present study, we explore the cerebral metabolic responses under extreme hypoxia and hypercapnia associated with prolonged apnoea. We hypothesized that the cerebral metabolic rate for oxygen (CMRO2 ) will be reduced near the termination of apnoea, attributed in part to the hypercapnia. Fourteen elite apnoea-divers performed a maximal apnoea (range 3 min 36 s to 7 min 26 s) under dry laboratory conditions. In a subset study with the same divers, the impact of hypercapnia on cerebral metabolism was determined using varying levels of hypercapnic breathing, against the background of similar hypoxia. In both studies, the CMRO2 was calculated from the product of cerebral blood flow (ultrasound) and the radial artery-internal jugular venous oxygen content difference. Non-oxidative cerebral metabolism was calculated from the ratio of oxygen and carbohydrate (lactate and glucose) metabolism. The CMRO2 was reduced by ∼29% (P < 0.01, Cohen's d = 1.18) near the termination of apnoea compared to baseline, although non-oxidative metabolism remained unaltered. In the subset study, in similar backgrounds of hypoxia (arterial O2 tension: ∼38.4 mmHg), severe hypercapnia (arterial CO2 tension: ∼58.7 mmHg), but not mild-hypercapnia (arterial CO2 tension: ∼46.3 mmHg), depressed the CMRO2 (∼17%, P = 0.04, Cohen's d = 0.87). Similarly to the apnoea, there was no change in the non-oxidative metabolism. These data indicate that hypercapnia can partly explain the reduction in CMRO2 near the apnoea breakpoint. This hypercapnic-induced oxygen conservation may protect the brain against severe hypoxaemia associated with prolonged apnoea.
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Affiliation(s)
- Anthony R Bain
- Centre for Heart Lung and Vascular Health, University of British Columbia, Kelowna, BC, Canada. ,
| | - Philip N Ainslie
- Centre for Heart Lung and Vascular Health, University of British Columbia, Kelowna, BC, Canada
| | - Ryan L Hoiland
- Centre for Heart Lung and Vascular Health, University of British Columbia, Kelowna, BC, Canada
| | - Otto F Barak
- School of Medicine, University of Split, Split, Croatia.,Faculty of Medicine, University of Novi Sad, Serbia
| | - Marija Cavar
- School of Medicine, University of Split, Split, Croatia
| | - Ivan Drvis
- School of Kinesiology, University of Zagreb, Zagreb, Croatia
| | | | | | - Damian M Bailey
- Faculty of Life Sciences and Education, University of South Wales, Glamorgan, UK
| | - Zeljko Dujic
- School of Medicine, University of Split, Split, Croatia
| | - David B MacLeod
- Department of Anesthesiology, Duke University Medical Center, Durham, NC, USA
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14
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Hoiland RL, Ainslie PN, Bain AR, MacLeod DB, Stembridge M, Drvis I, Madden D, Barak O, MacLeod DM, Dujic Z. β 1-Blockade increases maximal apnea duration in elite breath-hold divers. J Appl Physiol (1985) 2016; 122:899-906. [PMID: 27125844 DOI: 10.1152/japplphysiol.00127.2016] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2016] [Revised: 04/04/2016] [Accepted: 04/26/2016] [Indexed: 11/22/2022] Open
Abstract
We hypothesized that the cardioselective β1-adrenoreceptor antagonist esmolol would improve maximal apnea duration in elite breath-hold divers. In elite national-level divers (n = 9), maximal apneas were performed in a randomized and counterbalanced order while receiving either iv esmolol (150 μg·kg-1·min-1) or volume-matched saline (placebo). During apnea, heart rate (ECG), beat-by-beat blood pressure, stroke volume (SV), cardiac output (CO), and total peripheral resistance (TPR) were measured (finger photoplethysmography). Myocardial oxygen consumption (MV̇o2) was estimated from rate pressure product. Cerebral blood flow through the internal carotid (ICA) and vertebral arteries (VA) was assessed using Duplex ultrasound. Apnea duration improved in the esmolol trial when compared with placebo (356 ± 57 vs. 323 ± 61 s, P < 0.01) despite similar end-apnea peripheral oxyhemoglobin saturation (71.8 ± 10.3 vs. 74.9 ± 9.5%, P = 0.10). The HR response to apnea was reduced by esmolol at 10-30% of apnea duration, whereas MAP was unaffected. Esmolol reduced SV (main effect, P < 0.05) and CO (main effect; P < 0.05) and increased TPR (main effect, P < 0.05) throughout apnea. Esmolol also reduced MV̇o2 throughout apnea (main effect, P < 0.05). Cerebral blood flow through the ICA and VA was unchanged by esmolol at baseline and the last 30 s of apnea; however, global cerebral blood flow was reduced in the esmolol trial at end-apnea (P < 0.05). Our findings demonstrate that, in elite breath-hold divers, apnea breakpoint is improved by β1-blockade, likely owing to an improved total body oxygen sparring through increased centralization of blood volume (↑TPR) and reduced MV̇o2NEW & NOTEWORTHY The governing bodies for international apnea competition, the Association Internationale pour le Développment de l'Apnée and La Confédération Mondaile des Activités Subaquatiques, have banned the use of β-blockers based on anecdotal reports that they improve apnea duration. Using a randomized placebo-controlled trial, we are the first to empirically confirm that β-blockade improves apnea duration. This improvement in apnea duration coincided with a reduced myocardial oxygen consumption.
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Affiliation(s)
- Ryan L Hoiland
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, University of British Columbia-Okanagan, Kelowna, British Columbia, Canada;
| | - Philip N Ainslie
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, University of British Columbia-Okanagan, Kelowna, British Columbia, Canada
| | - Anthony R Bain
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, University of British Columbia-Okanagan, Kelowna, British Columbia, Canada
| | - David B MacLeod
- Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina
| | - Mike Stembridge
- Cardiff School of Sport, Cardiff Metropolitan University, Cardiff, United Kingdom
| | - Ivan Drvis
- University of Zagreb School of Kinesiology, Zagreb, Croatia
| | - Dennis Madden
- Department of Integrative Physiology, University of Split School of Medicine, Split, Croatia
| | - Otto Barak
- Department of Physiology, University of Novi Sad School of Medicine, Novi Sad, Serbia; and
| | | | - Zeljko Dujic
- Department of Integrative Physiology, University of Split School of Medicine, Split, Croatia
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15
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Bain AR, Ainslie PN, Hoiland RL, Willie CK, MacLeod DB, Madden D, Maslov PZ, Drviš I, Dujić Ž. Role of cerebral blood flow in extreme breath holding. Transl Neurosci 2016; 7:12-16. [PMID: 28123816 PMCID: PMC5017590 DOI: 10.1515/tnsci-2016-0003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Accepted: 02/02/2015] [Indexed: 11/15/2022] Open
Abstract
The role of cerebral blood flow (CBF) on a maximal breath-hold (BH) in ultra-elite divers was examined. Divers (n = 7) performed one control BH, and one BH following oral administration of the non-selective cyclooxygenase inhibitor indomethacin (1.2 mg/kg). Arterial blood gases and CBF were measured prior to (baseline), and at BH termination. Compared to control, indomethacin reduced baseline CBF and cerebral delivery of oxygen (CDO2) by about 26% (p < 0.01). Indomethacin reduced maximal BH time from 339 ± 51 to 319 ± 57 seconds (p = 0.04). In both conditions, the CDO2 remained unchanged from baseline to the termination of apnea. At BH termination, arterial oxygen tension was higher following oral administration of indomethacin compared to control (4.05 ± 0.45 vs. 3.44 ± 0.32 kPa). The absolute increase in CBF from baseline to the termination of apnea was lower with indomethacin (p = 0.01). These findings indicate that the impact of CBF on maximal BH time is likely attributable to its influence on cerebral H+ washout, and therefore central chemoreceptive drive to breathe, rather than to CDO2.
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Affiliation(s)
- Anthony R Bain
- Centre for Heart Lung and Vascular Health, University of British Columbia, Kelowna, BC, Canada
| | - Philip N Ainslie
- Centre for Heart Lung and Vascular Health, University of British Columbia, Kelowna, BC, Canada
| | - Ryan L Hoiland
- Centre for Heart Lung and Vascular Health, University of British Columbia, Kelowna, BC, Canada
| | - Chris K Willie
- Centre for Heart Lung and Vascular Health, University of British Columbia, Kelowna, BC, Canada
| | - David B MacLeod
- Department of Anesthesiology, Duke University Medical Center, Durham, NC, United States of America
| | - Dennis Madden
- Department of Integrative Physiology, University of Split School of Medicine, Split, Croatia
| | - Petra Zubin Maslov
- Department of Integrative Physiology, University of Split School of Medicine, Split, Croatia
| | - Ivan Drviš
- School of Kinesiology, University of Zagreb, Zagreb, Croatia
| | - Željko Dujić
- Department of Integrative Physiology, University of Split School of Medicine, Split, Croatia
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16
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Limberg JK, Johnson BD, Holbein WW, Ranadive SM, Mozer MT, Joyner MJ. Interindividual variability in the dose-specific effect of dopamine on carotid chemoreceptor sensitivity to hypoxia. J Appl Physiol (1985) 2016; 120:138-47. [PMID: 26586909 PMCID: PMC4719057 DOI: 10.1152/japplphysiol.00723.2015] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2015] [Accepted: 11/13/2015] [Indexed: 11/22/2022] Open
Abstract
Human studies use varying levels of low-dose (1-4 μg·kg(-1)·min(-1)) dopamine to examine peripheral chemosensitivity, based on its known ability to blunt carotid body responsiveness to hypoxia. However, the effect of dopamine on the ventilatory responses to hypoxia is highly variable between individuals. Thus we sought to determine 1) the dose response relationship between dopamine and peripheral chemosensitivity as assessed by the ventilatory response to hypoxia in a cohort of healthy adults, and 2) potential confounding cardiovascular responses at variable low doses of dopamine. Young, healthy adults (n = 30, age = 32 ± 1, 24 male/6 female) were given intravenous (iv) saline and a range of iv dopamine doses (1-4 μg·kg(-1)·min(-1)) prior to and throughout five hypoxic ventilatory response (HVR) tests. Subjects initially received iv saline, and after each HVR the dopamine infusion rate was increased by 1 μg·kg(-1)·min(-1). Tidal volume, respiratory rate, heart rate, blood pressure, and oxygen saturation were continuously measured. Dopamine significantly reduced HVR at all doses (P < 0.05). When subjects were divided into high (n = 13) and low (n = 17) baseline chemosensitivity, dopamine infusion (when assessed by dose) reduced HVR in the high group only (P < 0.01), with no effect of dopamine on HVR in the low group (P > 0.05). Dopamine infusion also resulted in a reduction in blood pressure (3 μg·kg(-1)·min(-1)) and total peripheral resistance (1-4 μg·kg(-1)·min(-1)), driven primarily by subjects with low baseline chemosensitivity. In conclusion, we did not find a single dose of dopamine that elicited a nadir HVR in all subjects. Additionally, potential confounding cardiovascular responses occur with dopamine infusion, which may limit its usage.
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Affiliation(s)
| | - Blair D Johnson
- Department of Anesthesiology, Mayo Clinic, Rochester, Minnesota; and Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, New York
| | - Walter W Holbein
- Department of Anesthesiology, Mayo Clinic, Rochester, Minnesota; and
| | | | - Michael T Mozer
- Department of Anesthesiology, Mayo Clinic, Rochester, Minnesota; and
| | - Michael J Joyner
- Department of Anesthesiology, Mayo Clinic, Rochester, Minnesota; and
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