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Ryan BJ, Seeley AD, Pitsas DM, Mayer TA, Caldwell AR, Ceaser TG, Luippold AJ, Charkoudian N, Salgado RM. Influence of graded hypercapnia on endurance exercise performance in healthy humans. Am J Physiol Regul Integr Comp Physiol 2022; 323:R638-R647. [PMID: 36094451 PMCID: PMC9602925 DOI: 10.1152/ajpregu.00132.2022] [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: 06/20/2022] [Revised: 08/22/2022] [Accepted: 09/06/2022] [Indexed: 11/22/2022]
Abstract
Military and/or emergency services personnel may be required to perform high-intensity physical activity during exposure to elevated inspired carbon dioxide (CO2). Although many of the physiological consequences of hypercapnia are well characterized, the effects of graded increases in inspired CO2 on self-paced endurance performance have not been determined. The aim of this study was to compare the effects of 0%, 2%, and 4% inspired CO2 on 2-mile run performance, as well as physiological and perceptual responses during time trial exercise. Twelve physically active volunteers (peak oxygen uptake = 49 ± 5 mL·kg-1·min-1; 3 women) performed three experimental trials in a randomized, single-blind, crossover manner, breathing 21% oxygen with either 0%, 2%, or 4% CO2. During each trial, participants completed 10 min of walking at ∼40% peak oxygen uptake followed by a self-paced 2-mile treadmill time trial. One participant was unable to complete the 4% CO2 trial due to lightheadedness during the run. Compared with the 0% CO2 trial, run performance was 5 ± 3% and 7 ± 3% slower in the 2% and 4% CO2 trials, respectively (both P < 0.001). Run performance was significantly slower with 4% versus 2% CO2 (P = 0.046). The dose-dependent performance impairments were accompanied by stepwise increases in mean ventilation, despite significant reductions in running speed. Dyspnea and headache were significantly elevated during the 4% CO2 trial compared with both the 0% and 2% trials. Overall, our findings show that graded increases in inspired CO2 impair endurance performance in a stepwise manner in healthy humans.
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Affiliation(s)
- Benjamin J Ryan
- Thermal and Mountain Medicine Division, United States Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - Afton D Seeley
- Thermal and Mountain Medicine Division, United States Army Research Institute of Environmental Medicine, Natick, Massachusetts
- Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee
| | - Dina M Pitsas
- Thermal and Mountain Medicine Division, United States Army Research Institute of Environmental Medicine, Natick, Massachusetts
- Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee
| | - Thomas A Mayer
- Thermal and Mountain Medicine Division, United States Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - Aaron R Caldwell
- Thermal and Mountain Medicine Division, United States Army Research Institute of Environmental Medicine, Natick, Massachusetts
- Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee
| | - Tyrone G Ceaser
- Thermal and Mountain Medicine Division, United States Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - Adam J Luippold
- Thermal and Mountain Medicine Division, United States Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - Nisha Charkoudian
- Thermal and Mountain Medicine Division, United States Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - Roy M Salgado
- Thermal and Mountain Medicine Division, United States Army Research Institute of Environmental Medicine, Natick, Massachusetts
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Cao Y, Fujii N, Fujimoto T, Lai YF, Ogawa T, Hiroyama T, Enomoto Y, Nishiyasu T. CO 2-Enriched Air Inhalation Modulates the Ventilatory and Metabolic Responses of Endurance Runners During Incremental Running in Hypobaric Hypoxia. High Alt Med Biol 2022; 23:125-134. [PMID: 35613387 DOI: 10.1089/ham.2021.0114] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Cao, Yinhang, Naoto Fujii, Tomomi Fujimoto, Yin-Feng Lai, Takeshi Ogawa, Tsutomu Hiroyama, Yasushi Enomoto, and Takeshi Nishiyasu. CO2-enriched air inhalation modulates the ventilatory and metabolic responses of endurance runners during incremental running in hypobaric hypoxia. High Alt Med Biol. 23:125-134, 2022. Aim: We measured the effects of breathing CO2-enriched air on ventilatory and metabolic responses during incremental running exercise under moderately hypobairc hypoxic (HH) conditions. Materials and Methods: Ten young male endurance runners [61.4 ± 6.0 ml/(min·kg)] performed incremental running tests under three conditions: (1) normobaric normoxia (NN), (2) HH (2,500 m), and (3) HH with 5% CO2 inhalation (HH+CO2). The test under NN was always performed first, and then, the two remaining tests were completed in random and counterbalanced order. Results: End-tidal CO2 partial pressure (55 ± 3 vs. 35 ± 1 mmHg), peak ventilation (163 ± 14 vs. 152 ± 12 l/min), and peak oxygen uptake [52.3 ± 5.5 vs. 50.5 ± 4.9 ml/(min·kg)] were all higher in the HH+CO2 than HH trial (all p < 0.01), respectively. However, the duration of the incremental test did not differ between HH+CO2 and HH trials. Conclusion: These data suggest that chemoreflex activation by breathing CO2-enriched air stimulates breathing and aerobic metabolism during maximal intensity exercise without affecting exercise performance in male endurance runners under a moderately hypobaric hypoxic environment.
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Affiliation(s)
- Yinhang Cao
- School of Physical Education and Sport Training, Shanghai University of Sport, Shanghai, China.,Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba City, Japan
| | - Naoto Fujii
- Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba City, Japan
| | - Tomomi Fujimoto
- Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba City, Japan.,Department of Health and Sports, Niigata University of Health and Welfare, Niigata, Japan
| | - Yin-Feng Lai
- Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba City, Japan
| | - Takeshi Ogawa
- Division of Art, Music, and Physical Education, Osaka Kyoiku University, Osaka, Japan
| | - Tsutomu Hiroyama
- Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba City, Japan
| | - Yasushi Enomoto
- Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba City, Japan
| | - Takeshi Nishiyasu
- Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba City, Japan
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Kato T, Matsumoto T, Yamashiro SM. Effect of 3% CO2 inhalation on respiratory exchange ratio and cardiac output during constant work-rate exercise. J Sports Med Phys Fitness 2020; 61:175-182. [PMID: 32734753 DOI: 10.23736/s0022-4707.20.11012-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
BACKGROUND The aim of this study was to examine whether the decrease in respiratory exchange ratio (RER) during constant work-rate exercise (CWE) with 3% carbon dioxide (CO<inf>2</inf>) inhalation could be caused by the combination of the decrease in CO<inf>2</inf> output (V̇CO<inf>2</inf>) and the increase in oxygen uptake (V̇O<inf>2</inf>). In addition, we investigated the effect of 3% CO<inf>2</inf> inhalation on cardiac output (Q̇) during CWE. METHODS Seven males (V̇O<inf>2max</inf>: 44.1±6.4 mL/min/kg) carried out transitions from low-load cycling (baseline; 40w) to light intensity exercise (45% V̇O<inf>2 max</inf>; 89.3±12.5 W) and heavy intensity exercise (80% V̇O<inf>2max</inf>; 186.5±20.2 W) while inhaling normal air (Air) or an enriched CO<inf>2</inf> gas (3% CO<inf>2</inf>, 21% O<inf>2</inf>, balance N<inf>2</inf>). Each exercise session was 6 min, and respiratory responses by Douglas bag technique and cardiac responses by thoracic bio-impedance method were measured during the experiment. RESULTS Ventilation for 3% CO<inf>2</inf> was higher than for air through the experiment (P<0.05). Steady and non-steady state RER and V̇CO<inf>2</inf> for 3% CO<inf>2</inf> were less than for air in both light and heavy intensities (P<0.05), but V̇O<inf>2</inf> and Q̇ did not differ between the two conditions. CONCLUSIONS 3% CO<inf>2</inf> inhalation induced the decrease in RER during CWE at light and heavy intensities, which was due to the decrease in V̇CO<inf>2</inf>. The promoted ventilation with 3% CO<inf>2</inf> did not lead to the increase in V̇O<inf>2</inf>. Moreover, 3% CO<inf>2</inf> inhalation did not affect Q̇ during CWE at light and heavy intensities.
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Affiliation(s)
- Takahide Kato
- Department of General Education, National Institute of Technology, Toyota College, Toyota, Japan -
| | - Takaaki Matsumoto
- Laboratory for Exercise Physiology and Biomechanics, School of Health and Sport Sciences, Chukyo University, Toyota, Japan
| | - Stanley M Yamashiro
- Department of Biomedical Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, CA, USA
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Pulmonary hemodynamics responses to hypoxia and/or CO 2 inhalation during moderate exercise in humans. Pflugers Arch 2018; 470:1035-1045. [PMID: 29502264 DOI: 10.1007/s00424-018-2127-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2017] [Revised: 02/07/2018] [Accepted: 02/19/2018] [Indexed: 02/06/2023]
Abstract
In this study, we hypothesized that adding CO2 to an inhaled hypoxic gas mixture will limit the rise of pulmonary artery pressure (PAP) induced by a moderate exercise. Eight 20-year-old males performed four constant-load exercise tests on cycle at 40% of maximal oxygen consumption in four conditions: ambient air, normobaric hypoxia (12.5% O2), inhaled CO2 (4.5% CO2), and combination of hypoxia and inhaled CO2. Doppler echocardiography was used to measure systolic (s)PAP, cardiac output (CO). Total pulmonary resistance (TPR) was calculated. Arterialized blood pH was 7.40 at exercise in ambient and hypoxia conditions, whereas CO2 inhalation and combined conditions showed acidosis. sPAP increases from rest in ambient air to exercise ranged as follows: ambient + 110%, CO2 inhalation + 135%, combined + 184%, hypoxia + 217% (p < 0.001). CO was higher when inhaling O2-poor gas mixtures with or without CO2 (~ 17 L min-1) than in the other conditions (~ 14 L min-1, p < 0.001). Exercise induced a significant decrease in TPR in the four conditions (p < 0.05) but less marked in hypoxia (- 19% of the resting value in ambient air) than in ambient (- 33%) and in both CO2 inhalation and combined condition (- 29%). We conclude that (1) acute CO2 inhalation did not significantly modify pulmonary hemodynamics during moderate exercise. (2) CO2 adjunction to hypoxic gas mixture did not modify CO, despite a higher CaO2 in combined condition than in hypoxia. (3) TPR was lower in combined than in hypoxia condition, limiting sPAP increase in combined condition.
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Taccone FS, Crippa IA, Vincent JL. Normobaric hyperoxia after stroke: a word of caution. Expert Rev Neurother 2017; 18:91-93. [DOI: 10.1080/14737175.2018.1414600] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
- Fabio Silvio Taccone
- Department of Intensive Care, Erasme Hospital, Université Libre de Bruxelles, Brussels, Belgium
| | - Ilaria Alice Crippa
- Department of Intensive Care, Erasme Hospital, Université Libre de Bruxelles, Brussels, Belgium
| | - Jean-Louis Vincent
- Department of Intensive Care, Erasme Hospital, Université Libre de Bruxelles, Brussels, Belgium
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Ding X, Zhou S, Li M, Cao C, Wu P, Sun L, Fei G, Wang R. Upregulation of SRF Is Associated With Hypoxic Pulmonary Hypertension by Promoting Viability of Smooth Muscle Cells via Increasing Expression of Bcl-2. J Cell Biochem 2017; 118:2731-2738. [PMID: 28176371 DOI: 10.1002/jcb.25922] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2016] [Accepted: 02/06/2017] [Indexed: 12/11/2022]
Abstract
The aim of study was to investigate the involvement of hypoxia-induced upregulation of serum response factor (SRF) and its downstream effector, B cell leukemia-2 (Bcl-2), in hypoxia-induced pulmonary hypertension (PH). Immunohistochemistry analysis and western blot analysis were used to detect the levels of SRF and Bcl-2 in rats exposed to hypoxia. Furthermore, the regulatory relationship between SRF and Bcl-2 was investigated in PASMCs using real-time PCR and western-blot analysis. We found that mPAP (mean pulmonary arterial pressure) and WA (the ratio of vascular wall area to external diameter) were increased after exposure to hypoxia, while LA (the ratio of vascular lumen area to total area) decreased after exposure to hypoxia. The immunohistochemistry analysis displayed a substantial increase in SRF and Bcl-2 in pulmonary arterial walls after 14 days of hypoxia. And the western blotting showed that SRF and Bcl-2 protein levels were much higher after 7 days of hypoxia and then remained at a high level. And then the levels of SRF and Bcl-2 in pulmonary artery smooth muscle cells (PASMCs) exposed to hypoxia were substantially suppressed following introduction of SRF siRNA, and the level of Bcl-2 was remarkably inhibited by Bcl-2 siRNA, while Bcl-2 siRNA had no effect on SRF level. Finally, SRF siRNA, and Bcl-2 siRNA significantly reduced viability of PASMCs exposed to hypoxia, and enhanced apoptosis of PASMCs exposed to hypoxia. These data validated that SRF responded to hypoxia, which subsequently was involved in pulmonary hypertension by abnormally promoting viability of PASMCs via modulating expression of Bcl-2. J. Cell. Biochem. 118: 2731-2738, 2017. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Xing Ding
- Department of Respiratory Medicine, First Affiliated Hospital of Anhui Medical University, Hefei, China
| | - Sijing Zhou
- Department of Occupational Medicine, Hefei Third Clinical College Affiliated to Anhui Medical University, Hefei, China
| | - Min Li
- Department of Oncology, First Affiliated Hospital of Anhui Medical University, Hefei, China
| | - Chao Cao
- Department of Respiratory Medicine, Ningbo First Hospital, Ningbo, China
| | - Peipei Wu
- Department of Respiratory Medicine, First Affiliated Hospital of Anhui Medical University, Hefei, China
| | - Li Sun
- Department of Respiratory Medicine, First Affiliated Hospital of Anhui Medical University, Hefei, China
| | - Guanghe Fei
- Department of Respiratory Medicine, First Affiliated Hospital of Anhui Medical University, Hefei, China
| | - Ran Wang
- Department of Respiratory Medicine, First Affiliated Hospital of Anhui Medical University, Hefei, China
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