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Borrelli M, Shokohyar S, Rampichini S, Bruseghini P, Doria C, Limonta EG, Ferretti G, Esposito F. Energetics of sinusoidal exercise below and across critical power and the effects of fatigue. Eur J Appl Physiol 2024; 124:1845-1859. [PMID: 38242972 PMCID: PMC11130025 DOI: 10.1007/s00421-023-05410-1] [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: 09/27/2023] [Accepted: 12/23/2023] [Indexed: 01/21/2024]
Abstract
PURPOSE Previous studies investigating sinusoidal exercise were not devoted to an analysis of its energetics and of the effects of fatigue. We aimed to determine the contribution of aerobic and anaerobic lactic metabolism to the energy balance and investigate the fatigue effects on the cardiorespiratory and metabolic responses to sinusoidal protocols, across and below critical power (CP). METHODS Eight males (26.6 ± 6.2 years; 75.6 ± 8.7 kg; maximum oxygen uptake 52.8 ± 7.9 ml·min-1·kg-1; CP 218 ± 13 W) underwent exhausting sinusoidal cycloergometric exercises, with sinusoid midpoint (MP) at CP (CPex) and 50 W below CP (CP-50ex). Sinusoid amplitude (AMP) and period were 50 W and 4 min, respectively. MP, AMP, and time-delay (tD) between mechanical and metabolic signals of expiratory ventilation (V ˙ E ), oxygen uptake (V ˙ O 2 ), and heart rate ( f H ) were assessed sinusoid-by-sinusoid. Blood lactate ([La-]) and rate of perceived exertion (RPE) were determined at each sinusoid. RESULTS V ˙ O 2 AMP was 304 ± 11 and 488 ± 36 ml·min-1 in CPex and CP-50ex, respectively. Asymmetries between rising and declining sinusoid phases occurred in CPex (36.1 ± 7.7 vs. 41.4 ± 9.7 s forV ˙ O 2 tD up and tD down, respectively; P < 0.01), with unchanged tDs.V ˙ O 2 MP and RPE increased progressively during CPex. [La-] increased by 2.1 mM in CPex but remained stable during CP-50ex. Anaerobic contribution was larger in CPex than CP-50ex. CONCLUSION The lower aerobic component during CPex than CP-50ex associated with lactate accumulation explained lowerV ˙ O 2 AMP in CPex. The asymmetries in CPex suggest progressive decline of muscle phosphocreatine concentration, leading to fatigue, as witnessed by RPE.
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Affiliation(s)
- Marta Borrelli
- Department of Biomedical Sciences for Health, Università Degli Studi Di Milano, Via Giuseppe Colombo 71, 20133, Milan, Italy
| | - Sheida Shokohyar
- Department of Biomedical Sciences for Health, Università Degli Studi Di Milano, Via Giuseppe Colombo 71, 20133, Milan, Italy
| | - Susanna Rampichini
- Department of Biomedical Sciences for Health, Università Degli Studi Di Milano, Via Giuseppe Colombo 71, 20133, Milan, Italy.
| | - Paolo Bruseghini
- Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy
| | - Christian Doria
- Department of Biomedical Sciences for Health, Università Degli Studi Di Milano, Via Giuseppe Colombo 71, 20133, Milan, Italy
| | - Eloisa Guglielmina Limonta
- Department of Biomedical Sciences for Health, Università Degli Studi Di Milano, Via Giuseppe Colombo 71, 20133, Milan, Italy
- IRCCS Ospedale Galeazzi - Sant'Ambrogio, Via Cristina Belgioioso, 173, 20157, Milan, Italy
| | - Guido Ferretti
- Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy
| | - Fabio Esposito
- Department of Biomedical Sciences for Health, Università Degli Studi Di Milano, Via Giuseppe Colombo 71, 20133, Milan, Italy
- IRCCS Ospedale Galeazzi - Sant'Ambrogio, Via Cristina Belgioioso, 173, 20157, Milan, Italy
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2
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Nicolò A, Sacchetti M. Differential control of respiratory frequency and tidal volume during exercise. Eur J Appl Physiol 2023; 123:215-242. [PMID: 36326866 DOI: 10.1007/s00421-022-05077-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Accepted: 10/18/2022] [Indexed: 11/06/2022]
Abstract
The lack of a testable model explaining how ventilation is regulated in different exercise conditions has been repeatedly acknowledged in the field of exercise physiology. Yet, this issue contrasts with the abundance of insightful findings produced over the last century and calls for the adoption of new integrative perspectives. In this review, we provide a methodological approach supporting the importance of producing a set of evidence by evaluating different studies together-especially those conducted in 'real' exercise conditions-instead of single studies separately. We show how the collective assessment of findings from three domains and three levels of observation support the development of a simple model of ventilatory control which proves to be effective in different exercise protocols, populations and experimental interventions. The main feature of the model is the differential control of respiratory frequency (fR) and tidal volume (VT); fR is primarily modulated by central command (especially during high-intensity exercise) and muscle afferent feedback (especially during moderate exercise) whereas VT by metabolic inputs. Furthermore, VT appears to be fine-tuned based on fR levels to match alveolar ventilation with metabolic requirements in different intensity domains, and even at a breath-by-breath level. This model reconciles the classical neuro-humoral theory with apparently contrasting findings by leveraging on the emerging control properties of the behavioural (i.e. fR) and metabolic (i.e. VT) components of minute ventilation. The integrative approach presented is expected to help in the design and interpretation of future studies on the control of fR and VT during exercise.
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Affiliation(s)
- Andrea Nicolò
- Department of Movement, Human and Health Sciences, University of Rome "Foro Italico", Piazza Lauro De Bosis 6, 00135, Rome, Italy.
| | - Massimo Sacchetti
- Department of Movement, Human and Health Sciences, University of Rome "Foro Italico", Piazza Lauro De Bosis 6, 00135, Rome, Italy
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Haouzi P, Tubbs N. Effects of fentanyl overdose-induced muscle rigidity and dexmedetomidine on respiratory mechanics and pulmonary gas exchange in sedated rats. J Appl Physiol (1985) 2022; 132:1407-1422. [PMID: 35421320 DOI: 10.1152/japplphysiol.00819.2021] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The objective of our study was to establish in sedated rats the consequences of high-dose fentanyl-induced acute muscle rigidity on the mechanical properties of the respiratory system and on the metabolic rate. Doses of fentanyl that we have previously shown to produce persistent rigidity of the muscles of the limbs and trunk in the rat (150 -300 microg/kg iv), were administered in 23 volume-controlled mechanically ventilated and sedated rats. The effects of a low dose of the FDA approved central alpha-2 agonist, dexmedetomidine (3 microg/kg iv), which has been suggested to oppose fentanyl-induced muscle rigidity, were determined after fentanyl administration. Fentanyl produced a significant decrease in Crs in the 23 rats that were studied. In 13 rats, an abrupt response occurred within 90 seconds, consisting in rapid rhythmic contractions of most skeletal muscles, that were replaced by persistent tonic/tetanic contractions leading a significant decrease of Crs (from 0.51 ± 0.11 ml/cmH2O to 0.36 ± 0.08 ml/cmH2O, 3 minutes after fentanyl injection). In the other 10 animals, a Crs progressively decreased to 0.26 ± 0.06 ml/cmH2O at 30 minutes. There was a significant rise in V̇O2 during muscle tonic contractions (from 8.48 ± 4.31 to 11.29 ± 2.57 ml/min), which contributed to a significant hypoxemia, despite ventilation being held constant. Dexmedetomidine provoked a significant and rapid increase in Crs towards baseline levels, while decreasing the metabolic rate and restoring normoxemia. We propose that the changes in respiratory mechanics and metabolism produced by opioid-induced muscle rigidity contribute to fentanyl lethality.
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Affiliation(s)
- Philippe Haouzi
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Pennsylvania State University, College of Medicine, Hershey, PA, United States
| | - Nicole Tubbs
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Pennsylvania State University, College of Medicine, Hershey, PA, United States
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4
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Fujita M, Kamibayashi K, Aoki T, Horiuchi M, Fukuoka Y. Influence of Step Frequency on the Dynamic Characteristics of Ventilation and Gas Exchange During Sinusoidal Walking in humans. Front Physiol 2022; 13:820666. [PMID: 35492612 PMCID: PMC9039249 DOI: 10.3389/fphys.2022.820666] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2021] [Accepted: 02/14/2022] [Indexed: 11/17/2022] Open
Abstract
We tested the hypothesis that restricting either step frequency (SF) or stride length (SL) causes a decrease in ventilatory response with limited breath frequency during sinusoidal walking. In this study, 13 healthy male and female volunteers (mean ± SD; age: 21.5 ± 1.8 years, height: 168 ± 7 cm, weight: 61.5 ± 8.3 kg) participated. The walking speed was sinusoidally changed between 50 and 100 m⋅min–1 with periods from 10 to 1 min. Using a customized sound system, we fixed the SF at 120 steps⋅min–1 with SL variation (0.83–0.41 m) (SFfix) or fixed the SL at 0.7 m with SF variation (143–71 steps⋅min–1) (SLfix) during the subjects’ sinusoidal walking. Both the subjects’ preferred locomotion pattern without a sound system (Free) and the unprompted spontaneous locomotor pattern for each subject (Free) served as the control condition. We measured breath-by-breath ventilation [tidal volume (VT) and breathing frequency (Bf)] and gas exchange [CO2 output (V.CO2), O2 uptake (V.O2)]. The amplitude (Amp) and the phase shift (PS) of the fundamental component of the ventilatory and gas exchange variables were calculated. The results revealed that the SFfix condition decreased the Amp of the Bf response compared with SLfix and Free conditions. Notably, the Amp of the Bf response under SFfix was reduced by less than one breath at the periods of 5 and 10 min. In contrast, the SLfix condition resulted in larger Amps of Bf and V.E responses as well as Free. We thus speculate that the steeper slope of the V.E-V.CO2 relationship observed under the SLfix might be attributable to the central feed-forward command or upward information from afferent neural activity by sinusoidal locomotive cadence. The PSs of the V.E, V.O2, and V.CO2 responses were unaffected by any locomotion patterns. Such a sinusoidal wave manipulation of locomotion variables may offer new insights into the dynamics of exercise hyperpnea.
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Affiliation(s)
- Mako Fujita
- Faculty of Health and Sports Science, Doshisha University, Kyoto, Japan
| | | | - Tomoko Aoki
- Faculty of Environmental Symbiotic Science, Prefectural University of Kumamoto, Kumamoto, Japan
| | - Masahiro Horiuchi
- Division of Human Environmental Science, Mt. Fuji Research Institute, Fujiyoshida, Japan
| | - Yoshiyuki Fukuoka
- Faculty of Health and Sports Science, Doshisha University, Kyoto, Japan
- *Correspondence: Yoshiyuki Fukuoka,
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Differences in the point of optimal ventilatory efficiency and the anaerobic threshold in untrained adults aged 50 to 60 years. Respir Physiol Neurobiol 2020; 282:103516. [DOI: 10.1016/j.resp.2020.103516] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Revised: 07/06/2020] [Accepted: 08/02/2020] [Indexed: 11/18/2022]
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Vaporidi K, Akoumianaki E, Telias I, Goligher EC, Brochard L, Georgopoulos D. Respiratory Drive in Critically Ill Patients. Pathophysiology and Clinical Implications. Am J Respir Crit Care Med 2020; 201:20-32. [DOI: 10.1164/rccm.201903-0596so] [Citation(s) in RCA: 97] [Impact Index Per Article: 24.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Affiliation(s)
- Katerina Vaporidi
- Department of Intensive Care Medicine, University Hospital of Heraklion, Medical School University of Crete, Heraklion, Greece
| | - Evangelia Akoumianaki
- Department of Intensive Care Medicine, University Hospital of Heraklion, Medical School University of Crete, Heraklion, Greece
| | - Irene Telias
- Interdepartmental Division of Critical Care Medicine, University of Toronto, Toronto, Ontario, Canada
- Keenan Research Center and Li Ka Shing Knowledge Institute, St. Michael’s Hospital, Toronto, Ontario, Canada
| | - Ewan C. Goligher
- Interdepartmental Division of Critical Care Medicine, University of Toronto, Toronto, Ontario, Canada
- Department of Medicine, University Health Network, Toronto, Ontario, Canada; and
- Toronto General Hospital Research Institute, Toronto, Ontario, Canada
| | - Laurent Brochard
- Interdepartmental Division of Critical Care Medicine, University of Toronto, Toronto, Ontario, Canada
- Keenan Research Center and Li Ka Shing Knowledge Institute, St. Michael’s Hospital, Toronto, Ontario, Canada
| | - Dimitris Georgopoulos
- Department of Intensive Care Medicine, University Hospital of Heraklion, Medical School University of Crete, Heraklion, Greece
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7
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8
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Nicolò A, Girardi M, Bazzucchi I, Felici F, Sacchetti M. Respiratory frequency and tidal volume during exercise: differential control and unbalanced interdependence. Physiol Rep 2018; 6:e13908. [PMID: 30393984 PMCID: PMC6215760 DOI: 10.14814/phy2.13908] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2018] [Revised: 10/02/2018] [Accepted: 10/03/2018] [Indexed: 01/14/2023] Open
Abstract
Differentiating between respiratory frequency (fR ) and tidal volume (VT ) may improve our understanding of exercise hyperpnoea because fR and VT seem to be regulated by different inputs. We designed a series of exercise manipulations to improve our understanding of how fR and VT are regulated during exercise. Twelve cyclists performed an incremental test and three randomized experimental sessions in separate visits. In two of the three experimental visits, participants performed a moderate-intensity sinusoidal test followed, after recovery, by a moderate-to-severe-intensity sinusoidal test. These two visits differed in the period of the sinusoid (2 min vs. 8 min). In the third experimental visit, participants performed a trapezoidal test where the workload was self-paced in order to match a predefined trapezoidal template of rating of perceived exertion (RPE). The results collectively reveal that fR changes more with RPE than with workload, gas exchange, VT or the amount of muscle activation. However, fR dissociates from RPE during moderate exercise. Both VT and minute ventilation ( V ˙ E ) showed a similar time course and a large correlation with V ˙ CO 2 in all the tests. Nevertheless, V ˙ CO 2 was associated more with V ˙ E than with VT because VT seems to adjust continuously on the basis of fR levels to match V ˙ E with V ˙ CO 2 . The present findings provide novel insight into the differential control of fR and VT - and their unbalanced interdependence - during exercise. The emerging conceptual framework is expected to guide future research on the mechanisms underlying the long-debated issue of exercise hyperpnoea.
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Affiliation(s)
- Andrea Nicolò
- Department of Movement, Human and Health SciencesUniversity of Rome “Foro Italico”RomeItaly
| | - Michele Girardi
- Department of Movement, Human and Health SciencesUniversity of Rome “Foro Italico”RomeItaly
| | - Ilenia Bazzucchi
- Department of Movement, Human and Health SciencesUniversity of Rome “Foro Italico”RomeItaly
| | - Francesco Felici
- Department of Movement, Human and Health SciencesUniversity of Rome “Foro Italico”RomeItaly
| | - Massimo Sacchetti
- Department of Movement, Human and Health SciencesUniversity of Rome “Foro Italico”RomeItaly
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9
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Gonzalez NC, Kuwahira I. Systemic Oxygen Transport with Rest, Exercise, and Hypoxia: A Comparison of Humans, Rats, and Mice. Compr Physiol 2018; 8:1537-1573. [PMID: 30215861 DOI: 10.1002/cphy.c170051] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The objective of this article is to compare and contrast the known characteristics of the systemic O2 transport of humans, rats, and mice at rest and during exercise in normoxia and hypoxia. This analysis should help understand when rodent O2 transport findings can-and cannot-be applied to human responses to similar conditions. The O2 -transport system was analyzed as composed of four linked conductances: ventilation, alveolo-capillary diffusion, circulatory convection, and tissue capillary-cell diffusion. While the mechanisms of O2 transport are similar in the three species, the quantitative differences are naturally large. There are abundant data on total O2 consumption and on ventilatory and pulmonary diffusive conductances under resting conditions in the three species; however, there is much less available information on pulmonary gas exchange, circulatory O2 convection, and tissue O2 diffusion in mice. The scarcity of data largely derives from the difficulty of obtaining blood samples in these small animals and highlights the need for additional research in this area. In spite of the large quantitative differences in absolute and mass-specific O2 flux, available evidence indicates that resting alveolar and arterial and venous blood PO2 values under normoxia are similar in the three species. Additionally, at least in rats, alveolar and arterial blood PO2 under hypoxia and exercise remain closer to the resting values than those observed in humans. This is achieved by a greater ventilatory response, coupled with a closer value of arterial to alveolar PO2 , suggesting a greater efficacy of gas exchange in the rats. © 2018 American Physiological Society. Compr Physiol 8:1537-1573, 2018.
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Affiliation(s)
- Norberto C Gonzalez
- Department of Molecular and Integrative Physiology, University of Kansas Medical Center, Kansas City, Kansas, USA
| | - Ichiro Kuwahira
- Department of Pulmonary Medicine, Tokai University School of Medicine, Tokai University Tokyo Hospital, Tokyo, Japan
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10
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Serna LY, Mañanas MA, Hernández AM, Rabinovich RA. An Improved Dynamic Model for the Respiratory Response to Exercise. Front Physiol 2018; 9:69. [PMID: 29467674 PMCID: PMC5808356 DOI: 10.3389/fphys.2018.00069] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2017] [Accepted: 01/19/2018] [Indexed: 11/30/2022] Open
Abstract
Respiratory system modeling has been extensively studied in steady-state conditions to simulate sleep disorders, to predict its behavior under ventilatory diseases or stimuli and to simulate its interaction with mechanical ventilation. Nevertheless, the studies focused on the instantaneous response are limited, which restricts its application in clinical practice. The aim of this study is double: firstly, to analyze both dynamic and static responses of two known respiratory models under exercise stimuli by using an incremental exercise stimulus sequence (to analyze the model responses when step inputs are applied) and experimental data (to assess prediction capability of each model). Secondly, to propose changes in the models' structures to improve their transient and stationary responses. The versatility of the resulting model vs. the other two is shown according to the ability to simulate ventilatory stimuli, like exercise, with a proper regulation of the arterial blood gases, suitable constant times and a better adjustment to experimental data. The proposed model adjusts the breathing pattern every respiratory cycle using an optimization criterion based on minimization of work of breathing through regulation of respiratory frequency.
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Affiliation(s)
- Leidy Y Serna
- Biomedical Engineering Research Centre (CREB), Automatic Control Department, ESAII, Universitat Politècnica de Catalunya, Barcelona, Spain.,Biomedical Research Networking Center in Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), Madrid, Spain
| | - Miguel A Mañanas
- Biomedical Engineering Research Centre (CREB), Automatic Control Department, ESAII, Universitat Politècnica de Catalunya, Barcelona, Spain.,Biomedical Research Networking Center in Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), Madrid, Spain
| | - Alher M Hernández
- Bioinstrumentation and Clinical Engineering Research Group - GIBIC, Bioengineering Department, Engineering Faculty, Universidad de Antioquia (UdeA), Medellín, Colombia
| | - Roberto A Rabinovich
- ELEGI and COLT Laboratories, Centre for Inflammation Research, Queen's Medical Research Institute, University of Edinburgh, Edinburgh, United Kingdom.,Department of Respiratory Medicine, Royal Infirmary of Edinburgh, Edinburgh, United Kingdom
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11
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The cessation of breathing in the chicken embryo during cold-hypometabolism. Respir Physiol Neurobiol 2017; 242:19-29. [PMID: 28341290 DOI: 10.1016/j.resp.2017.03.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2016] [Revised: 02/22/2017] [Accepted: 03/08/2017] [Indexed: 01/15/2023]
Abstract
The avian embryo toward end-incubation combines gas exchange through the chorioallantoic membrane (CAM) and pulmonary ventilation (V˙E). The main experiments examined breathing activity during cold-hypometabolism. Chicken embryos close to hatching were prepared for simultaneous measurements of oxygen consumption ( [Formula: see text] ) and carbon dioxide production ( [Formula: see text] ; open-flow methodology) and breathing frequency (f; barometric technique). As ambient (Ta) and egg temperature (Tegg) dropped, breathing eventually ceased at ∼18°C, when [Formula: see text] and [Formula: see text] were 22-28% of the normothermic values. With the eggshell experimentally covered to reduce CAM gas exchange breathing ceased at slightly lower [Formula: see text] and [Formula: see text] (17-18% of normothermia). Once breathing had stopped, egg exposure to hypoxia (10% or 5% O2) or hypercapnia (3% or 8% CO2) did not resume breathing, which recovered with re-warming. In normothermia, 10% O2 caused hypometabolism and tachypnea; differently, in 5% O2 [Formula: see text] dropped as much as with hypothermia and breathing stopped, to recover upon return in air. Correlation analysis among Ta, Tegg, [Formula: see text] , [Formula: see text] and f during cooling and re-warming indicated that f followed more closely the changes in [Formula: see text] and, especially, in [Formula: see text] than the changes in Ta or Tegg. Some considerations suggest that in this experimental model the cessation of breathing in hypothermia or severe hypoxia may be due to hypometabolism, while the lack of chemo-responses may have a different mechanistic basis.
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12
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Fukuoka Y, Iihoshi M, Nazunin JT, Abe D, Fukuba Y. Dynamic Characteristics of Ventilatory and Gas Exchange during Sinusoidal Walking in Humans. PLoS One 2017; 12:e0168517. [PMID: 28076413 PMCID: PMC5226792 DOI: 10.1371/journal.pone.0168517] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2016] [Accepted: 12/01/2016] [Indexed: 11/28/2022] Open
Abstract
Our present study investigated whether the ventilatory and gas exchange responses show different dynamics in response to sinusoidal change in cycle work rate or walking speed even if the metabolic demand was equivalent in both types of exercise. Locomotive parameters (stride length and step frequency), breath-by-breath ventilation (V̇E) and gas exchange (CO2 output (V̇CO2) and O2 uptake (V̇O2)) responses were measured in 10 healthy young participants. The speed of the treadmill was sinusoidally changed between 3 km·h-1 and 6 km·h-1 with various periods (from 10 to 1 min). The amplitude of locomotive parameters against sinusoidal variation showed a constant gain with a small phase shift, being independent of the oscillation periods. In marked contrast, when the periods of the speed oscillations were shortened, the amplitude of V̇E decreased sharply whereas the phase shift of V̇E increased. In comparing walking and cycling at the equivalent metabolic demand, the amplitude of V̇E during sinusoidal walking (SW) was significantly greater than that during sinusoidal cycling (SC), and the phase shift became smaller. The steeper slope of linear regression for the V̇E amplitude ratio to V̇CO2 amplitude ratio was observed during SW than SC. These findings suggested that the greater amplitude and smaller phase shift of ventilatory dynamics were not equivalent between SW and SC even if the metabolic demand was equivalent between both exercises. Such phenomenon would be derived from central command in proportion to locomotor muscle recruitment (feedforward) and muscle afferent feedback.
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Affiliation(s)
- Yoshiyuki Fukuoka
- Laboratory of Environmental Physiology, Faculty of Environmental and Symbiotic Sciences, Prefectural University of Kumamoto, Kumamoto, Japan
- Laboratory of Environmental Physiology, Faculty of Health and Sports Science, Doshisha University, Kyotanabe, Japan
- * E-mail:
| | - Masaaki Iihoshi
- Laboratory of Environmental Physiology, Faculty of Environmental and Symbiotic Sciences, Prefectural University of Kumamoto, Kumamoto, Japan
| | - Juhelee Tuba Nazunin
- Laboratory of Environmental Physiology, Faculty of Health and Sports Science, Doshisha University, Kyotanabe, Japan
| | - Daijiro Abe
- Biodynamics Laboratory, Center for Health and Sports Science, Kyushu Sangyo University, Fukuoka, Japan
| | - Yoshiyuki Fukuba
- Department of Sports Science and Physiology, Hiroshima Prefectural University, Hiroshima, Japan
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Muscat KM, Kotrach HG, Wilkinson-Maitland CA, Schaeffer MR, Mendonca CT, Jensen D. Physiological and perceptual responses to incremental exercise testing in healthy men: effect of exercise test modality. Appl Physiol Nutr Metab 2015; 40:1199-209. [DOI: 10.1139/apnm-2015-0179] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In a randomized cross-over study of 15 healthy men aged 20–30 years, we compared physiological and perceptual responses during treadmill and cycle exercise test protocols matched for increments in work rate — the source of increased locomotor muscle metabolic and contractile demands. The rates of O2 consumption and CO2 production were higher at the peak of treadmill versus cycle testing (p ≤ 0.05). Nevertheless, work rate, minute ventilation, tidal volume (VT), breathing frequency (fR), inspiratory capacity (IC), inspiratory reserve volume (IRV), tidal esophageal (Pes,tidal) and transdiaphragmatic pressure swings (Pdi,tidal), peak expiratory gastric pressures (Pga,peak), the root mean square of the diaphragm electromyogram (EMGdi,rms) expressed as a percentage of maximum EMGdi,rms (EMGdi,rms%max), and dyspnea ratings were similar at the peak of treadmill versus cycle testing (p > 0.05). Ratings of leg discomfort were higher at the peak of cycle versus treadmill exercise (p ≤ 0.05), even though peak O2 consumption was lower during cycling. Oxygen consumption, CO2 production, minute ventilation, fR, Pes,tidal, Pdi,tidal and Pga,peak were higher (p ≤ 0.05), while VT, IC, IRV, EMGdi,rms%max, and ratings of dyspnea and leg discomfort were similar (p > 0.05) at all or most submaximal work rates during treadmill versus cycle exercise. Our findings highlight important differences (and similarities) in physiological and perceptual responses at maximal and submaximal work rates during incremental treadmill and cycle exercise testing protocols. The lack of effect of exercise test modality on peak work rate advocates for the use of this readily available parameter to optimize training intensity determination, regardless of exercise training mode.
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Affiliation(s)
- Kristina M. Muscat
- Clinical Exercise and Respiratory Physiology Laboratory, Department of Kinesiology and Physical Education, McGill University, Montréal, QC H2W 1S4, Canada
| | - Houssam G. Kotrach
- Clinical Exercise and Respiratory Physiology Laboratory, Department of Kinesiology and Physical Education, McGill University, Montréal, QC H2W 1S4, Canada
| | - Courtney A. Wilkinson-Maitland
- Clinical Exercise and Respiratory Physiology Laboratory, Department of Kinesiology and Physical Education, McGill University, Montréal, QC H2W 1S4, Canada
| | - Michele R. Schaeffer
- Clinical Exercise and Respiratory Physiology Laboratory, Department of Kinesiology and Physical Education, McGill University, Montréal, QC H2W 1S4, Canada
| | - Cassandra T. Mendonca
- Clinical Exercise and Respiratory Physiology Laboratory, Department of Kinesiology and Physical Education, McGill University, Montréal, QC H2W 1S4, Canada
| | - Dennis Jensen
- Clinical Exercise and Respiratory Physiology Laboratory, Department of Kinesiology and Physical Education, McGill University, Montréal, QC H2W 1S4, Canada
- Respiratory Epidemiology and Clinical Research Unit, Montréal Chest Institute, McGill University Health Centre, Montréal, QC H4A 3J1, Canada
- Research Centre for Physical Activity and Health, McGill University, Montréal, QC H2W 1S4, Canada
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Caterini JE, Duffin J, Wells GD. Limb movement frequency is a significant modulator of the ventilatory response during submaximal cycling exercise in humans. Respir Physiol Neurobiol 2015; 220:10-6. [PMID: 26369445 DOI: 10.1016/j.resp.2015.09.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2015] [Revised: 07/16/2015] [Accepted: 09/10/2015] [Indexed: 11/27/2022]
Abstract
Human experimentation investigating the contribution of limb movement frequency in determining the fast exercise drive to breathe has produced controversial findings. To evaluate the role of limb movement frequency in determining the fast exercise drive to breathe, endurance runners and recreationally-active controls performed two sinusoidal exercise protocols on a cycle ergometer. One protocol was performed at constant workload with sinusoidal pedaling cadence, and a second with sinusoidal workload at constant cadence. Metabolic rate (VO2) increases and means were matched between these two experiments. The ventilatory response was significantly faster when limb movement speed was varied, compared to when pedal loading was varied (18.49 ± 15.6s vs. 50.5 ± 14.5s, p<0.05). Ventilation response amplitudes were significantly higher during pedal cadence variation versus pedal loading variation (3.99 ± 0.25 vs. 2.58 ± 0.17 L/min, p<0.05). Similar findings were obtained for endurance athletes, with significantly attenuated ventilation responses to exercise versus control subjects. We conclude that fast changes in limb movement frequency are a potent stimulus for ventilation at submaximal workloads, and that this response is susceptible to attenuation through training.
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Affiliation(s)
- Jessica E Caterini
- Graduate Department of Exercise Sciences, University of Toronto, 100 Devonshire Place, Toronto, Ontario M5S 2C9, Canada; Physiology and Experimental Medicine, The Hospital for Sick Children, 555 University Avenue, Toronto, Ontario M5G 1X8, Canada
| | - James Duffin
- Department of Physiology, University of Toronto, 1 King's College Circle, Toronto, Ontario M5S 1A8, Canada; Department of Anaesthesia, University of Toronto Health Network, 200 Elizabeth St., Toronto, Ontario M5G 2C4 Canada
| | - Gregory D Wells
- Physiology and Experimental Medicine, The Hospital for Sick Children, 555 University Avenue, Toronto, Ontario M5G 1X8, Canada; Faculty of Kinesiology and Physical Education, University of Toronto, 100 Devonshire Place, Toronto, Ontario M5S2C9, Canada.
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Ba A, Brégeon F, Delliaux S, Cissé F, Samb A, Jammes Y. Cardiopulmonary response to exercise in COPD and overweight patients: relationship between unloaded cycling and maximal oxygen uptake profiles. BIOMED RESEARCH INTERNATIONAL 2015; 2015:378469. [PMID: 25866778 PMCID: PMC4383510 DOI: 10.1155/2015/378469] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/17/2014] [Revised: 09/03/2014] [Accepted: 09/21/2014] [Indexed: 11/25/2022]
Abstract
Cardiopulmonary response to unloaded cycling may be related to higher workloads. This was assessed in male subjects: 18 healthy sedentary subjects (controls), 14 hypoxemic patients with chronic obstructive pulmonary disease (COPD), and 31 overweight individuals (twelve were hypoxemic). They underwent an incremental exercise up to the maximal oxygen uptake (VO2max), preceded by a 2 min unloaded cycling period. Oxygen uptake (VO2), heart rate (HR), minute ventilation (VE), and respiratory frequency (fR) were averaged every 10 s. At the end of unloaded cycling period, HR increase was significantly accentuated in COPD and hypoxemic overweight subjects (resp., +14 ± 2 and +13 ± 1.5 min(-1), compared to +7.5 ± 1.5 min(-1) in normoxemic overweight subjects and +8 ± 1.8 min(-1) in controls). The fR increase was accentuated in all overweight subjects (hypoxemic: +4.5 ± 0.8; normoxemic: +3.9 ± 0.7 min(-1)) compared to controls (+2.5 ± 0.8 min(-1)) and COPDs (+2.0 ± 0.7 min(-1)). The plateau VE increase during unloaded cycling was positively correlated with VE values measured at the ventilatory threshold and VO2max. Measurement of ventilation during unloaded cycling may serve to predict the ventilatory performance of COPD patients and overweight subjects during an exercise rehabilitation program.
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Affiliation(s)
- Abdoulaye Ba
- Service des Explorations Fonctionnelles Respiratoires, Hopital Nord (Assistance Publique-Hôpitaux de Marseille) and UMR MD2, Faculté de Médecine Secteur Nord, Boulevard Pierre Dramard, 13916 Cedex 20 Marseille, France
- Laboratory of Physiology, Faculty of Medicine, University of Cheikh Anta Diop, Dakar, P.O. Box 45698, Dakar Fann, Dakar, Senegal
- Unité Mixte Internationale Environnement, Santé, Sociétés (UMI3189 ESS), Université Cheikh Anta Diop (UCAD), P.O. Box 5005, Dakar Fann, Senegal
| | - Fabienne Brégeon
- Service des Explorations Fonctionnelles Respiratoires, Hopital Nord (Assistance Publique-Hôpitaux de Marseille) and UMR MD2, Faculté de Médecine Secteur Nord, Boulevard Pierre Dramard, 13916 Cedex 20 Marseille, France
| | - Stéphane Delliaux
- Service des Explorations Fonctionnelles Respiratoires, Hopital Nord (Assistance Publique-Hôpitaux de Marseille) and UMR MD2, Faculté de Médecine Secteur Nord, Boulevard Pierre Dramard, 13916 Cedex 20 Marseille, France
| | - Fallou Cissé
- Laboratory of Physiology, Faculty of Medicine, University of Cheikh Anta Diop, Dakar, P.O. Box 45698, Dakar Fann, Dakar, Senegal
| | - Abdoulaye Samb
- Laboratory of Physiology, Faculty of Medicine, University of Cheikh Anta Diop, Dakar, P.O. Box 45698, Dakar Fann, Dakar, Senegal
- Unité Mixte Internationale Environnement, Santé, Sociétés (UMI3189 ESS), Université Cheikh Anta Diop (UCAD), P.O. Box 5005, Dakar Fann, Senegal
| | - Yves Jammes
- Service des Explorations Fonctionnelles Respiratoires, Hopital Nord (Assistance Publique-Hôpitaux de Marseille) and UMR MD2, Faculté de Médecine Secteur Nord, Boulevard Pierre Dramard, 13916 Cedex 20 Marseille, France
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Wienecke J, Enríquez Denton M, Stecina K, Kirkwood PA, Hultborn H. Modulation of spontaneous locomotor and respiratory drives to hindlimb motoneurons temporally related to sympathetic drives as revealed by Mayer waves. Front Neural Circuits 2015; 9:1. [PMID: 25713515 PMCID: PMC4322721 DOI: 10.3389/fncir.2015.00001] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2014] [Accepted: 01/05/2015] [Indexed: 12/12/2022] Open
Abstract
In this study we investigated how the networks mediating respiratory and locomotor drives to lumbar motoneurons interact and how this interaction is modulated in relation to periodic variations in blood pressure (Mayer waves). Seven decerebrate cats, under neuromuscular blockade, were used to study central respiratory drive potentials (CRDPs, usually enhanced by added CO2) and spontaneously occurring locomotor drive potentials (LDPs) in hindlimb motoneurons, together with hindlimb and phrenic nerve discharges. In four of the cats both drives and their voltage-dependent amplification were absent or modest, but in the other three, one or other of these drives was common and the voltage-dependent amplification was frequently strong. Moreover, in these three cats the blood pressure showed marked periodic variation (Mayer waves), with a slow rate (periods 9–104 s, mean 39 ± 17 SD). Profound modulation, synchronized with the Mayer waves was seen in the occurrence and/or in the amplification of the CRDPs or LDPs. In one animal, where CRDPs were present in most cells and the amplification was strong, the CRDP consistently triggered sustained plateaux at one phase of the Mayer wave cycle. In the other two animals, LDPs were common, and the occurrence of the locomotor drive was gated by the Mayer wave cycle, sometimes in alternation with the respiratory drive. Other interactions between the two drives involved respiration providing leading events, including co-activation of flexors and extensors during post-inspiration or a locomotor drive gated or sometimes entrained by respiration. We conclude that the respiratory drive in hindlimb motoneurons is transmitted via elements of the locomotor central pattern generator. The rapid modulation related to Mayer waves suggests the existence of a more direct and specific descending modulatory control than has previously been demonstrated.
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Affiliation(s)
- Jacob Wienecke
- Department of Neuroscience and Pharmacology, The Panum Institute, University of Copenhagen Copenhagen, Denmark ; Department of Nutrition, Exercise and Sports, The Panum Institute, University of Copenhagen Copenhagen, Denmark
| | - Manuel Enríquez Denton
- Department of Neuroscience and Pharmacology, The Panum Institute, University of Copenhagen Copenhagen, Denmark ; Sobell Department for Motor Neuroscience and Movement Disorders, University College London Institute of Neurology London, UK ; Universidad del Valle de México Mexico City, Mexico
| | - Katinka Stecina
- Department of Neuroscience and Pharmacology, The Panum Institute, University of Copenhagen Copenhagen, Denmark ; Department of Physiology and Pathophysiology, University of Manitoba Winnipeg, MB, Canada
| | - Peter A Kirkwood
- Sobell Department for Motor Neuroscience and Movement Disorders, University College London Institute of Neurology London, UK
| | - Hans Hultborn
- Department of Neuroscience and Pharmacology, The Panum Institute, University of Copenhagen Copenhagen, Denmark
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Affiliation(s)
- Philippe Haouzi
- Pennsylvania State University, College of Medicine, Department of Medicine, Division of Pulmonary and Critical Care Medicine, Hershey, Pennsylvania
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Abstract
Lung ventilation fluctuates widely with behavior but arterial PCO2 remains stable. Under normal conditions, the chemoreflexes contribute to PaCO2 stability by producing small corrective cardiorespiratory adjustments mediated by lower brainstem circuits. Carotid body (CB) information reaches the respiratory pattern generator (RPG) via nucleus solitarius (NTS) glutamatergic neurons which also target rostral ventrolateral medulla (RVLM) presympathetic neurons thereby raising sympathetic nerve activity (SNA). Chemoreceptors also regulate presympathetic neurons and cardiovagal preganglionic neurons indirectly via inputs from the RPG. Secondary effects of chemoreceptors on the autonomic outflows result from changes in lung stretch afferent and baroreceptor activity. Central respiratory chemosensitivity is caused by direct effects of acid on neurons and indirect effects of CO2 via astrocytes. Central respiratory chemoreceptors are not definitively identified but the retrotrapezoid nucleus (RTN) is a particularly strong candidate. The absence of RTN likely causes severe central apneas in congenital central hypoventilation syndrome. Like other stressors, intense chemosensory stimuli produce arousal and activate circuits that are wake- or attention-promoting. Such pathways (e.g., locus coeruleus, raphe, and orexin system) modulate the chemoreflexes in a state-dependent manner and their activation by strong chemosensory stimuli intensifies these reflexes. In essential hypertension, obstructive sleep apnea and congestive heart failure, chronically elevated CB afferent activity contributes to raising SNA but breathing is unchanged or becomes periodic (severe CHF). Extreme CNS hypoxia produces a stereotyped cardiorespiratory response (gasping, increased SNA). The effects of these various pathologies on brainstem cardiorespiratory networks are discussed, special consideration being given to the interactions between central and peripheral chemoreflexes.
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Affiliation(s)
- Patrice G Guyenet
- Department of Pharmacology, University of Virginia, Charlottesville, Virginia
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Abstract
During dynamic exercise, the healthy pulmonary system faces several major challenges, including decreases in mixed venous oxygen content and increases in mixed venous carbon dioxide. As such, the ventilatory demand is increased, while the rising cardiac output means that blood will have considerably less time in the pulmonary capillaries to accomplish gas exchange. Blood gas homeostasis must be accomplished by precise regulation of alveolar ventilation via medullary neural networks and sensory reflex mechanisms. It is equally important that cardiovascular and pulmonary system responses to exercise be precisely matched to the increase in metabolic requirements, and that the substantial gas transport needs of both respiratory and locomotor muscles be considered. Our article addresses each of these topics with emphasis on the healthy, young adult exercising in normoxia. We review recent evidence concerning how exercise hyperpnea influences sympathetic vasoconstrictor outflow and the effect this might have on the ability to perform muscular work. We also review sex-based differences in lung mechanics.
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Affiliation(s)
- Andrew William Sheel
- The School of Kinesiology, The University of British Columbia, Vancouver, Canada.
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20
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Abstract
During exercise by healthy mammals, alveolar ventilation and alveolar-capillary diffusion increase in proportion to the increase in metabolic rate to prevent PaCO2 from increasing and PaO2 from decreasing. There is no known mechanism capable of directly sensing the rate of gas exchange in the muscles or the lungs; thus, for over a century there has been intense interest in elucidating how respiratory neurons adjust their output to variables which can not be directly monitored. Several hypotheses have been tested and supportive data were obtained, but for each hypothesis, there are contradictory data or reasons to question the validity of each hypothesis. Herein, we report a critique of the major hypotheses which has led to the following conclusions. First, a single stimulus or combination of stimuli that convincingly and entirely explains the hyperpnea has not been identified. Second, the coupling of the hyperpnea to metabolic rate is not causal but is due to of these variables each resulting from a common factor which link the circulatory and ventilatory responses to exercise. Third, stimuli postulated to act at pulmonary or cardiac receptors or carotid and intracranial chemoreceptors are not primary mediators of the hyperpnea. Fourth, stimuli originating in exercising limbs and conveyed to the brain by spinal afferents contribute to the exercise hyperpnea. Fifth, the hyperventilation during heavy exercise is not primarily due to lactacidosis stimulation of carotid chemoreceptors. Finally, since volitional exercise requires activation of the CNS, neural feed-forward (central command) mediation of the exercise hyperpnea seems intuitive and is supported by data from several studies. However, there is no compelling evidence to accept this concept as an indisputable fact.
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Affiliation(s)
- Hubert V Forster
- Medical College of Wisconsin, Department of Physiology, Milwaukee, Wisconsin, USA.
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21
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Haouzi P. Tracking pulmonary gas exchange by breathing control during exercise: role of muscle blood flow. J Physiol 2013; 592:453-61. [PMID: 23981720 PMCID: PMC4317246 DOI: 10.1113/jphysiol.2013.261396] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
Populations of group III and IV muscle afferent fibres located in the adventitia of the small vessels appear to respond to the level of venular distension and to recruitment of the vascular bed within the skeletal muscles. The CNS could thus be informed on the level of muscle hyperaemia when the metabolic rate varies. As a result, the magnitude and kinetics of the change in peripheral gas exchange – which translates into pulmonary gas exchange – can be sensed. We present the view that the respiratory control system uses these sources of information of vascular origin, among the numerous inputs produced by exercise, as a marker of the metabolic strain imposed on the circulatory and the ventilatory systems, resulting in an apparent matching between pulmonary gas exchange and alveolar ventilation.
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Affiliation(s)
- Philippe Haouzi
- Pennsylvania State University College of Medicine, Department of Medicine, 500 University Drive, H041, Hershey, PA 17033, USA.
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Bates ML, Pillers DAM, Palta M, Farrell ET, Eldridge MW. Ventilatory control in infants, children, and adults with bronchopulmonary dysplasia. Respir Physiol Neurobiol 2013; 189:329-37. [PMID: 23886637 DOI: 10.1016/j.resp.2013.07.015] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2013] [Revised: 07/16/2013] [Accepted: 07/16/2013] [Indexed: 12/17/2022]
Abstract
Bronchopulmonary dysplasia (BPD), or chronic lung disease of prematurity, occurs in ~30% of preterm infants (15,000 per year) and is associated with a clinical history of mechanical ventilation and/or high inspired oxygen at birth. Here, we describe changes in ventilatory control that exist in patients with BPD, including alterations in chemoreceptor function, respiratory muscle function, and suprapontine control. Because dysfunction in ventilatory control frequently revealed when O2 supply and CO2 elimination are challenged, we provide this information in the context of four important metabolic stressors: stresses: exercise, sleep, hypoxia, and lung disease, with a primary focus on studies of human infants, children, and adults. As a secondary goal, we also identify three key areas of future research and describe the benefits and challenges of longitudinal human studies using well-defined patient cohorts.
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Affiliation(s)
- Melissa L Bates
- Department of Pediatrics, Division of Critical Care, University of Wisconsin, Madison, WI, USA; John Rankin Laboratory of Pulmonary Medicine, University of Wisconsin, Madison, WI, USA.
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Haouzi P, Van de Louw A. Uncoupling mitochondrial activity maintains body [Formula: see text] during hemorrhage-induced O2 deficit in the anesthetized rat. Respir Physiol Neurobiol 2013; 186:87-94. [PMID: 23333818 DOI: 10.1016/j.resp.2012.12.006] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2012] [Revised: 12/20/2012] [Accepted: 12/21/2012] [Indexed: 01/25/2023]
Abstract
During a hemorrhagic shock (HS), O2 uptake ( [Formula: see text] ) decreases as soon as the rate of O2 delivery ( [Formula: see text] ) drops below a "critical level", a response accounted for by the reduction in mitochondrial O2supply. In urethane-anesthetized rats, [Formula: see text] was decreased within 20min from 21.5 to 2.8mlmin(-1) by slowly withdrawing 18mlkg(-1) of blood. This led to a reduction in [Formula: see text] from 6.1 to 2.4mlmin(-1) (n=5, p<0.01). Decoupling mitochondrial oxidative activity by injecting 2,4-DNP (6mgkg(-1), iv) before HS elevated [Formula: see text] to 11.9±1.2mlmin(-1) (n=6, p<0.01), which remained above control HS values throughout most of the hemorrhage. This was associated with higher levels of O2 extraction, cardiac output and ventilation than in control HS. [Formula: see text] relationship was shifted upward and to the left following DNP. In conclusion, cellular and systemic mechanisms, decreasing O2demand, account for a large part of HS induced [Formula: see text] decline resulting in an additional reduction in [Formula: see text] .
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Affiliation(s)
- Philippe Haouzi
- Pennsylvania State University, College of Medicine, Division of Pulmonary and Critical Care Medicine, Penn State Hershey Medical Center, Hershey, PA, United States.
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Power GA, Handrigan GA, Basset FA. Ventilatory response during an incremental exercise test: A mode of testing effect. Eur J Sport Sci 2012. [DOI: 10.1080/17461391.2011.573580] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/15/2022]
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Bartsch S, Gleeson K, Haouzi P. Neck Pain and Dyspnea: Lessons from a Patient with Zoster. PAIN MEDICINE 2012; 13:1250-2. [DOI: 10.1111/j.1526-4637.2012.01425.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Jutand L, Tremoureux L, Pichon A, Delpech N, Denjean A, Raux M, Straus C, Similowski T. Ventilatory response to exercise does not evidence electroencephalographical respiratory-related activation of the cortical premotor circuitry in healthy humans. Acta Physiol (Oxf) 2012; 205:356-62. [PMID: 22356255 DOI: 10.1111/j.1748-1716.2012.02427.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2011] [Revised: 10/10/2011] [Accepted: 02/12/2012] [Indexed: 11/26/2022]
Abstract
AIM The neural structures responsible for the coupling between ventilatory control and pulmonary gas exchange during exercise have not been fully identified. Suprapontine mechanisms have been hypothesized but not formally evidenced. Because the involvement of a premotor circuitry in the compensation of inspiratory mechanical loads has recently been described, we looked for its implication in exercise-induced hyperpnea. METHODS Electroencephalographical recordings were performed to identify inspiratory premotor potentials (iPPM) in eight physically fit normal men during cycling at 40 and 70% of their maximal oxygen consumption ((V)·O(2max) ). Relaxed pedalling (0 W) and voluntary sniff manoeuvres were used as negative and positive controls respectively. RESULTS Voluntary sniffs were consistently associated with iPPMs. This was also the case with voluntarily augmented breathing at rest (in three subjects tested). During the exercise protocol, no respiratory-related activity was observed whilst performing bouts of relaxed pedalling. Exercise-induced hyperpnea was also not associated with iPPMs, except in one subject. CONCLUSION We conclude that if there are cortical mechanisms involved in the ventilatory adaptation to exercise in physically fit humans, they are distinct from the premotor mechanisms activated by inspiratory load compensation.
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Affiliation(s)
| | | | - A. Pichon
- Université Paris 13; UFR SMBH, STAPS, UPRES EA 2363; Laboratoire Réponses Cellulaires et Fonctionnelles à l'Hypoxie; 74 rue Marcel Cachin; 93017; Bobigny; France
| | - N. Delpech
- Université de Poitiers; Laboratoire des Adaptations Physiologiques aux Activités Physiques; Faculté des Sciences du Sport; UPRES EA 3813; 4 Allée Jean Monnet; 86000; Poitiers; France
| | - A. Denjean
- Assistance Publique - Hôpitaux de Paris; Hôpital Robert Debré; Service de physiologie, Explorations Fonctionnelles; 75019; Paris; France
| | | | | | - T. Similowski
- Assistance Publique - Hôpitaux de Paris; Groupe Hospitalier Pitié-Salpêtrière; Service de Pneumologie et Réanimation; 75013; Paris; France
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Haouzi P, Van De Louw A, Haouzi A. Breathing during cardiac arrest following exercise: a new function of the respiratory system? Respir Physiol Neurobiol 2012; 181:220-7. [PMID: 22465526 DOI: 10.1016/j.resp.2012.03.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2012] [Revised: 03/13/2012] [Accepted: 03/14/2012] [Indexed: 11/29/2022]
Abstract
We have found in four sheep that, following a muscular exercise, minute ventilation is maintained for 34-131 s during a cardiac arrest (CA), at a magnitude (from 28.2 and 54.7 l min(-1)) similar to the level of ventilation (and thus proportional to the metabolic rate) preceding the period of asystole. Breathing was maintained despite the lack of pulmonary blood flow and the cessation of the muscle contractions, leading to a dramatic reduction in alveolar FCO(2) (1.9 ± 1%). Secondly, swings in arterial blood pressure (ABP) were observed (pulse pressure of 31 ± 3 Torr) in phase with breathing movements in place of the cardiac activity. This "protective" response, deprived from any role in blood gas homeostasis, as circulation is virtually abolished, is not predictable from the traditional respiratory control feedback systems thought to be involved in exercise. We are presenting the view that this response, dissociated from the pulmonary gas exchanges, is the expression of a rudimentary defense mechanism aimed at limiting the consequences of an acute failure of the cardiac pump by the thoraco-abdominal pump.
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Affiliation(s)
- Philippe Haouzi
- Division of Pulmonary and Critical Care Medicine, Pennsylvania State University, College of Medicine, Penn State Hershey Medical Center, United States.
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Haouzi P. Arterial blood acidity and control of breathing during exercise. Respir Physiol Neurobiol 2011; 180:173-4. [PMID: 22178547 DOI: 10.1016/j.resp.2011.12.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2011] [Accepted: 12/02/2011] [Indexed: 11/19/2022]
Affiliation(s)
- Philippe Haouzi
- Pennsylvania State University, College of Medicine, Division of Pulmonary and Critical Care Medicine, Penn State Hershey Medical Center, 500 University Dr., Hershey, PO Box 850, PA 17033, USA.
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Heinicke K, Taivassalo T, Wyrick P, Wood H, Babb TG, Haller RG. Exertional dyspnea in mitochondrial myopathy: clinical features and physiological mechanisms. Am J Physiol Regul Integr Comp Physiol 2011; 301:R873-84. [PMID: 21813873 DOI: 10.1152/ajpregu.00001.2011] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Exertional dyspnea limits exercise in some mitochondrial myopathy (MM) patients, but the clinical features of this syndrome are poorly defined, and its underlying mechanism is unknown. We evaluated ventilation and arterial blood gases during cycle exercise and recovery in five MM patients with exertional dyspnea and genetically defined mitochondrial defects, and in four control subjects (C). Patient ventilation was normal at rest. During exercise, MM patients had low Vo(2peak) (28 ± 9% of predicted) and exaggerated systemic O(2) delivery relative to O(2) utilization (i.e., a hyperkinetic circulation). High perceived breathing effort in patients was associated with exaggerated ventilation relative to metabolic rate with high VE/VO(2peak), (MM = 104 ± 18; C = 42 ± 8, P ≤ 0.001), and Ve/VCO(2peak)(,) (MM = 54 ± 9; C = 34 ± 7, P ≤ 0.01); a steeper slope of increase in ΔVE/ΔVCO(2) (MM = 50.0 ± 6.9; C = 32.2 ± 6.6, P ≤ 0.01); and elevated peak respiratory exchange ratio (RER), (MM = 1.95 ± 0.31, C = 1.25 ± 0.03, P ≤ 0.01). Arterial lactate was higher in MM patients, and evidence for ventilatory compensation to metabolic acidosis included lower Pa(CO(2)) and standard bicarbonate. However, during 5 min of recovery, despite a further fall in arterial pH and lactate elevation, ventilation in MM rapidly normalized. These data indicate that exertional dyspnea in MM is attributable to mitochondrial defects that severely impair muscle oxidative phosphorylation and result in a hyperkinetic circulation in exercise. Exaggerated exercise ventilation is indicated by markedly elevated VE/VO(2), VE/VCO(2), and RER. While lactic acidosis likely contributes to exercise hyperventilation, the fact that ventilation normalizes during recovery from exercise despite increasing metabolic acidosis strongly indicates that additional, exercise-specific mechanisms are responsible for this distinctive pattern of exercise ventilation.
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Affiliation(s)
- Katja Heinicke
- Neuromuscular Center, Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, 7232 Greenville Ave., #435, Dallas, TX 75231-5129, USA.
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Ventilatory response to moderate incremental exercise performed 24 h after resistance exercise with concentric and eccentric contractions. Eur J Appl Physiol 2011; 111:1769-75. [DOI: 10.1007/s00421-010-1801-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2010] [Accepted: 12/21/2010] [Indexed: 11/26/2022]
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Babb TG, Wood HE, Mitchell GS. Short- and long-term modulation of the exercise ventilatory response. Med Sci Sports Exerc 2010; 42:1681-7. [PMID: 20164813 DOI: 10.1249/mss.0b013e3181d7b212] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The importance of adaptive control strategies (modulation and plasticity) in the control of breathing during exercise has become recognized only in recent years. In this review, we discuss new evidence for modulation of the exercise ventilatory response in humans, specifically, short- and long-term modulation. Short-term modulation is proposed to be an important regulatory mechanism that helps maintain blood gas homeostasis during exercise.
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Affiliation(s)
- Tony G Babb
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, 7232 Greenville Ave, Dallas, TX 75231, USA.
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Haouzi P, Ahmadpour N, Bell HJ, Artman S, Banchs J, Samii S, Gonzalez M, Gleeson K. Breathing patterns during cardiac arrest. J Appl Physiol (1985) 2010; 109:405-11. [DOI: 10.1152/japplphysiol.00093.2010] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The absence of respiratory movements is a major criterion recommended for use by bystanders for recognizing an out-of-hospital cardiac arrest (CA), as the persistence of eupneic breathing is considered to be incompatible with CA. The basis for CA-related apnea is, however, uncertain, since brain stem Po2 is not expected to drop immediately to the critical level where anoxic apnea occurs. It is therefore essential on both clinical and physiological grounds to determine whether and when breathing stops after the onset of CA. In eight patients, we measured the ventilatory response at the onset of ventricular fibrillation (VF) for 12–15 s during the placement of an implantable cardioverter-defibrillator device. We found that regular eupneic breathing was maintained unchanged despite the cessation of systemic and pulmonary blood flow generated by the heart. We extended these findings in adult sheep and found that, as in humans, the normal ventilatory pattern persists unchanged for the first 15 s despite the drop in blood pressure, followed by a progressive increase in minute ventilation, which was sustained for up to 164 s. The ensuing apnea was disrupted by typical gasps occurring at a very slow frequency. These observations suggest a complete “decoupling” between the return of CO2 to the pulmonary circulation and continued effective respiratory activity, contrary to what we predicted. This delayed cessation of eupneic breathing during the absence of cardiac pump function is likely related to the time needed for brain stem anoxia to develop. These findings challenge the notions that 1) ventilation stops as pulmonary blood flow/cardiac output ceases and 2) the presence of eupneic breathing is a reliable sign of effective cardiac pumping activity.
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Affiliation(s)
- Philippe Haouzi
- Division of Pulmonary, Allergy, and Critical Care Medicine, Department of Medicine, College of Medicine, Pennsylvania State University, and
- Heart and Vascular Institute, Penn State Milton Hershey Medical Center, Hershey, Pennsylvania
| | - Nasrollah Ahmadpour
- Division of Pulmonary, Allergy, and Critical Care Medicine, Department of Medicine, College of Medicine, Pennsylvania State University, and
| | - Harold J. Bell
- Division of Pulmonary, Allergy, and Critical Care Medicine, Department of Medicine, College of Medicine, Pennsylvania State University, and
| | - Stephen Artman
- Heart and Vascular Institute, Penn State Milton Hershey Medical Center, Hershey, Pennsylvania
| | - Javier Banchs
- Heart and Vascular Institute, Penn State Milton Hershey Medical Center, Hershey, Pennsylvania
| | - Soraya Samii
- Heart and Vascular Institute, Penn State Milton Hershey Medical Center, Hershey, Pennsylvania
| | - Mario Gonzalez
- Heart and Vascular Institute, Penn State Milton Hershey Medical Center, Hershey, Pennsylvania
| | - Kevin Gleeson
- Division of Pulmonary, Allergy, and Critical Care Medicine, Department of Medicine, College of Medicine, Pennsylvania State University, and
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The increased ventilatory response to exercise in pregnancy reflects alterations in the respiratory control systems ventilatory recruitment threshold for CO2. Respir Physiol Neurobiol 2010; 171:75-82. [DOI: 10.1016/j.resp.2010.03.009] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2010] [Revised: 03/05/2010] [Accepted: 03/06/2010] [Indexed: 11/20/2022]
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Slessarev M, Prisman E, Ito S, Watson RR, Jensen D, Preiss D, Greene R, Norboo T, Stobdan T, Diskit D, Norboo A, Kunzang M, Appenzeller O, Duffin J, Fisher JA. Differences in the control of breathing between Himalayan and sea-level residents. J Physiol 2010; 588:1591-606. [PMID: 20194122 DOI: 10.1113/jphysiol.2009.185504] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
We compared the control of breathing of 12 male Himalayan highlanders with that of 21 male sea-level Caucasian lowlanders using isoxic hyperoxic ( = 150 mmHg) and hypoxic ( = 50 mmHg) Duffin's rebreathing tests. Highlanders had lower mean +/- s.e.m. ventilatory sensitivities to CO(2) than lowlanders at both isoxic tensions (hyperoxic: 2.3 +/- 0.3 vs. 4.2 +/- 0.3 l min(1) mmHg(1), P = 0.021; hypoxic: 2.8 +/- 0.3 vs. 7.1 +/- 0.6 l min(1) mmHg(1), P < 0.001), and the usual increase in ventilatory sensitivity to CO(2) induced by hypoxia in lowlanders was absent in highlanders (P = 0.361). Furthermore, the ventilatory recruitment threshold (VRT) CO(2) tensions in highlanders were lower than in lowlanders (hyperoxic: 33.8 +/- 0.9 vs. 48.9 +/- 0.7 mmHg, P < 0.001; hypoxic: 31.2 +/- 1.1 vs. 44.7 +/- 0.7 mmHg, P < 0.001). Both groups had reduced ventilatory recruitment thresholds with hypoxia (P < 0.001) and there were no differences in the sub-threshold ventilations (non-chemoreflex drives to breathe) between lowlanders and highlanders at both isoxic tensions (P = 0.982), with a trend for higher basal ventilation during hypoxia (P = 0.052). We conclude that control of breathing in Himalayan highlanders is distinctly different from that of sea-level lowlanders. Specifically, Himalayan highlanders have decreased central and absent peripheral sensitivities to CO(2). Their response to hypoxia was heterogeneous, with the majority decreasing their VRT indicating either a CO(2)-independent increase in activity of peripheral chemoreceptor or hypoxia-induced increase in [H(+)] at the central chemoreceptor. In some highlanders, the decrease in VRT was accompanied by an increase in sensitivity to CO(2), while in others VRT remained unchanged and their sub-threshold ventilations increased, although these were not statistically significant.
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Affiliation(s)
- M Slessarev
- Department of Anesthesia, University Health Network, University of Toronto, Toronto, Canada
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Yunoki T, Matsuura R, Arimitsu T, Yamanaka R, Kosugi S, Lian CS, Yano T. Effects of awareness of change in load on ventilatory response during moderate exercise. Respir Physiol Neurobiol 2009; 169:69-73. [PMID: 19703593 DOI: 10.1016/j.resp.2009.08.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2009] [Revised: 08/04/2009] [Accepted: 08/18/2009] [Indexed: 10/20/2022]
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Wells GD, Norris SR. Assessment of physiological capacities of elite athletes & respiratory limitations to exercise performance. Paediatr Respir Rev 2009; 10:91-8. [PMID: 19651378 DOI: 10.1016/j.prrv.2009.04.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Physiological assessment of athletes is an important process for the characterization of the athlete, monitoring progress and the trained state or 'level of preparedness' of an athlete, as well as aiding the process of training program design. Interestingly, the majority of physiological assessments performed on athletes can also be performed on children with disease, and therefore clinicians can learn a great deal about physiology and assessment of patient populations through the examination of the physiological responses of elite athletes. This review describes typical physiological responses of elite athletes to tests of aerobic and anaerobic metabolism and provides a specific focus upon respiratory limitations to exercise performance. Typical responses of elite athletes are described to provide the scientist and clinician with a perspective of the upper range of physiological capacities of elite athletes.
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Affiliation(s)
- Greg D Wells
- Physiology and Experimental Medicine, The Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8.
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Haouzi P. Venous pressure and dyspnea on exertion in cardiac failure: Was Tinsley Randolph Harrison right? Respir Physiol Neurobiol 2009; 167:101-6. [DOI: 10.1016/j.resp.2008.09.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2008] [Revised: 07/14/2008] [Accepted: 09/01/2008] [Indexed: 11/25/2022]
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Mechanisms of activity-related dyspnea in pulmonary diseases. Respir Physiol Neurobiol 2009; 167:116-32. [DOI: 10.1016/j.resp.2009.01.010] [Citation(s) in RCA: 161] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2009] [Accepted: 01/30/2009] [Indexed: 01/22/2023]
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40
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Jensen D, Ofir D, O’Donnell DE. Effects of pregnancy, obesity and aging on the intensity of perceived breathlessness during exercise in healthy humans. Respir Physiol Neurobiol 2009; 167:87-100. [DOI: 10.1016/j.resp.2009.01.011] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2009] [Revised: 01/26/2009] [Accepted: 01/30/2009] [Indexed: 11/29/2022]
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Hotta N, Yamamoto K, Ishida K. The effect of external cuff pressure on initial exercise hyperpnea. J Physiol Anthropol 2009; 28:91-5. [PMID: 19346669 DOI: 10.2114/jpa2.28.91] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022] Open
Abstract
The purpose of this study was to investigate the effect of an increase in intramuscular pressure on ventilatory response at the onset of exercise. Seven subjects participated in this study. We measured ventilatory responses to a 20-s single-arm extension-flexion exercise and passive movement. Each subject performed two kinds of exercise and passive movement in random order: in one, the exercising arm was encircled with a deflated cuff placed around the upper arm; in the other, the exercising arm was compressed by a cuff placed around the upper arm, which was inflated to 25 mmHg. We found that neither ventilatory response during exercise nor during passive movement was significantly changed even though the cuff compressed the arm. In conclusion, the increased intramuscular pressure caused by the 25-mmHg pressure of the cuff did not have a significant influence on ventilatory response at the onset of exercise.
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Affiliation(s)
- Norio Hotta
- Research Institute of Environmental Medicine, Nagoya University.
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Haouzi P, Bell HJ. Control of breathing and volitional respiratory rhythm in humans. J Appl Physiol (1985) 2009; 106:904-10. [DOI: 10.1152/japplphysiol.90675.2008] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
When breathing frequency (f) is imperceptibly increased during a volitionally paced respiratory rhythm imposed by an auditory signal, tidal volume (Vt) decreases such that minute ventilation (V̇e) rises according to f-induced dead-space ventilation changes ( 18 ). As a result, significant change in alveolar ventilation and Pco2 are prevented as f varies. The present study was performed to determine what regulatory properties are retained by the respiratory control system, wherein the spontaneous automatic rhythmic activity is replaced by a volitionally paced rhythm. Six volunteers were asked to trigger each breath cycle on hearing a brief auditory signal. The time interval between subsequent auditory signals was imperceptibly changed for 10–15 min, during 1) air breathing ( condition 1), 2) the addition of a 300 ml of instrumental dead space ( condition 2), 3) an increase in the inspired level of CO2 ( condition 3), and 4) light exercise ( condition 4). We found that as f was slowly increased the elaborated Vt decreased in accordance to the background level of CO2 and metabolic rate. Indeed, for any given breath duration, Vt was shifted upward in condition 2 vs. 1, whereas the slope of Vt changes according to the volitionally rhythm was much steeper in conditions 3 and 4 vs. 1. The resulting changes in V̇e offset any f-induced changes in dead-space ventilation in all conditions. We conclude that there is an inherent, fundamental mechanism that elaborates Vt based on f when imposed by the premotor cortex in humans. The chemoreflex and exercise drive to breath interacts with this cortically mediated rhythm maintaining alveolar rather than V̇e constant as f changes. The implications of our findings are discussed in the context of our current understanding of the central generation of breathing rhythm.
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The respiratory response to passive and active arm movements is enhanced in delayed onset muscle soreness. Eur J Appl Physiol 2008; 105:483-91. [DOI: 10.1007/s00421-008-0926-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/27/2008] [Indexed: 11/25/2022]
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Noah JA, Boliek C, Lam T, Yang JF. Breathing Frequency Changes at the Onset of Stepping in Human Infants. J Neurophysiol 2008; 99:1224-34. [DOI: 10.1152/jn.00868.2007] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Breathing frequency increases at the onset of movement in a wide rage of mammals including adult humans. Moreover, the magnitude of increase in the rate of breathing appears related to the rate of the rhythmic movement. We determined whether human infants show the same type of response when supported to step on a treadmill. Twenty infants (ages 9.7 ± 1.2 mo) participated in trials consisting of sitting, stepping on the treadmill, followed by sitting again. Breathing frequency was recorded with a thermocouple, positioned under one naris and taped to a soother that the infant held in his/her mouth. A video camera, electrogoniometers, and force platforms under the treadmill belts recorded stepping movements. We found that the rate of breathing changed at the beginning of stepping. Most surprisingly, we found that when infants stepped at a frequency slower than their breathing frequency in sitting, the breathing frequency decreased. Average breathing frequency during stepping was positively correlated with stepping frequency. There was no evidence of entrainment between stepping and breathing. In conclusion, the rapid change in breathing frequency at the beginning of movement is functional in infants. The direction and magnitude of change in breathing is associated with the leg movements.
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Control of the Exercise Hyperpnea: The Unanswered Question. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2008; 605:16-21. [DOI: 10.1007/978-0-387-73693-8_3] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
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Wood HE, Mitchell GS, Babb TG. Short-term modulation of the exercise ventilatory response in young men. J Appl Physiol (1985) 2007; 104:244-52. [PMID: 17991790 DOI: 10.1152/japplphysiol.00820.2007] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Arterial isocapnia is a hallmark of moderate exercise in humans and is maintained even when resting arterial Pco(2) (Pa(CO(2))) is raised or lowered from its normal level, e.g., with chronic acid-base changes or acute increases in respiratory dead space. When resting ventilation and/or Pa(CO(2)) are altered, maintenance of isocapnia requires active adjustments of the exercise ventilatory response [slope of the ventilation (Ve)-CO(2) production (Vco(2)) relationship, DeltaVe/DeltaVco(2)]. On the basis of animal studies, it has been proposed that a central neural mechanism links the exercise ventilatory response to the resting ventilatory drive without need for changes in chemoreceptor feedback from rest to exercise, a mechanism referred to as short-term modulation (STM). We tested the hypothesis that STM is elicited by increased resting ventilatory drive associated with added external dead space (DS) in humans. Twelve young men were studied in control conditions and with added DS (200, 400, and 600 ml; randomized) at rest and during mild-to-moderate cycle exercise. DeltaVe/DeltaVco(2) increased progressively as DS volume increased (P < 0.0001). While resting end-tidal Pco(2) (Pet(CO(2))) increased with DS, the change in Pet(CO(2)) from rest to exercise was not increased, indicating that increased chemoreceptor feedback from rest to exercise cannot account for the greater exercise ventilatory response. We conclude that STM of the exercise ventilatory response is induced in young men when resting ventilatory drive is increased with external DS, confirming the existence of STM in humans.
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Affiliation(s)
- Helen E Wood
- Institute for Exercise and Environmental Medicine, Presbyterian Hospital of Dallas, and University of Texas Southwestern Medical Center-Dallas, Dallas, Texas 75231, USA
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Poon CS, Tin C, Yu Y. Homeostasis of exercise hyperpnea and optimal sensorimotor integration: the internal model paradigm. Respir Physiol Neurobiol 2007; 159:1-13; discussion 14-20. [PMID: 17416554 PMCID: PMC2225386 DOI: 10.1016/j.resp.2007.02.020] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2007] [Revised: 02/28/2007] [Accepted: 02/28/2007] [Indexed: 11/16/2022]
Abstract
Homeostasis is a basic tenet of biomedicine and an open problem for many physiological control systems. Among them, none has been more extensively studied and intensely debated than the dilemma of exercise hyperpnea - a paradoxical homeostatic increase of respiratory ventilation that is geared to metabolic demands instead of the normal chemoreflex mechanism. Classical control theory has led to a plethora of "feedback/feedforward control" or "set point" hypotheses for homeostatic regulation, yet so far none of them has proved satisfactory in explaining exercise hyperpnea and its interactions with other respiratory inputs. Instead, the available evidence points to a far more sophisticated respiratory controller capable of integrating multiple afferent and efferent signals in adapting the ventilatory pattern toward optimality relative to conflicting homeostatic, energetic and other objectives. This optimality principle parsimoniously mimics exercise hyperpnea, chemoreflex and a host of characteristic respiratory responses to abnormal gas exchange or mechanical loading/unloading in health and in cardiopulmonary diseases - all without resorting to a feedforward "exercise stimulus". Rather, an emergent controller signal encoding the projected metabolic level is predicted by the principle as an exercise-induced 'mental percept' or 'internal model', presumably engendered by associative learning (operant conditioning or classical conditioning) which achieves optimality through continuous identification of, and adaptation to, the causal relationship between respiratory motor output and resultant chemical-mechanical afferent feedbacks. This internal model self-tuning adaptive control paradigm opens a new challenge and exciting opportunity for experimental and theoretical elucidations of the mechanisms of respiratory control - and of homeostatic regulation and sensorimotor integration in general.
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Affiliation(s)
- Chi-Sang Poon
- Harvard-MIT Division of Health Sciences and Technology, Bldg. 56-046, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA.
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Cherniack NS. Commentary on “Homeostasis of exercise hyperpnea and optimal sensorimotor integration: The internal model paradigm” by Poon et al. Respir Physiol Neurobiol 2007. [DOI: 10.1016/j.resp.2007.04.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Wells GD, Diep T, Duffin J. The ventilatory response to sine wave variation in exercise loads and limb movement frequency. Respir Physiol Neurobiol 2007; 158:45-50. [PMID: 17466602 DOI: 10.1016/j.resp.2007.03.009] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2006] [Revised: 03/12/2007] [Accepted: 03/13/2007] [Indexed: 10/23/2022]
Abstract
The current study's experiments tested the hypothesis that limb movement frequency is a significant determinant of exercise hyperpnoea. To this end, 19 healthy participants walked on a treadmill, where work was varied sinusiodally by alterations in either treadmill speed or grade. Measured responses were fitted with sine waves to determine their amplitudes and phase angles. Walking pace amplitude was greater during speed tests than grade tests, and phase lag relative to the treadmill smaller, as expected. Ventilation, carbon dioxide production, and oxygen uptake amplitudes were higher during speed tests than grade tests. Further, phase angle lags relative to the treadmill for these measures were shorter during speed tests than grade tests. We concluded that these findings demonstrate the presence of changes in breathing during exercise that can be attributed to changes in limb movement frequency.
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Affiliation(s)
- Gregory D Wells
- Department of Physiology and Experimental Medicine, The Hospital for Sick Children, Toronto, Canada.
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