Increased steady-state VO2 and larger O2 deficit with CO2 inhalation during exercise

Lars Østergaard, Kirsten Kjær, Kurt Jensen, L. B. Gladden, Torben Martinussen, Preben K. Pedersen

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Abstrakt

Abstract
Aim:  To examine whether inhalation of CO2-enriched gas would increase steady-state during exercise and enlarge O2 deficit.

Methods:  Ten physically active men ( 53.7 ± 3.6 mL min−1 kg−1; ± SD) performed transitions from low-load cycling (baseline; 40 W) to work rates representing light (≈ 45%; 122 ± 15 W) and heavy (≈ 80%; 253 ± 29 W) exercise while inhaling normal air (air) or a CO2 mixture (4.2% CO2, 21% O2, balance N2). Gas exchange was measured with Douglas bag technique at baseline and at min 0–2, 2–3 and 5–6.

Results:  Inhalation of CO2-enriched air consistently induced respiratory acidosis with increases in PCO2 and decreases in capillary blood pH (P < 0.01). Hypercapnic steady-state was on average about 6% greater (P < 0.01) than with air in both light and heavy exercise, presumably because of increased cost of breathing (ΔVE 40–50 L min−1; P < 0.01), and a substrate shift towards increased lipid oxidation (decline in R 0.12; P < 0.01). during the first 2 min of exercise were not significantly different whereas the increase in from min 2–3 to min 5–6 in heavy exercise was larger with CO2 than with air suggesting a greater slow component. As a result, O2 deficit was greater with hypercapnia in heavy exercise (2.24 ± 0.51 L vs. 1.91 ± 0.45 L; P < 0.05) but not in light (0.64 ± 0.21 L vs. 0.54 ± 0.20 L; ns).

Conclusion:  Inhalation of CO2-enriched air and the ensuing respiratory acidosis increase steady-state in both light and heavy exercise and enlarges O2 deficit in heavy exercise.
OriginalsprogEngelsk
TidsskriftActa Physiologica (Print)
Vol/bind204
Udgave nummer3
Sider (fra-til)371–381
Antal sider11
ISSN1748-1708
DOI
StatusUdgivet - 2012

Bibliografisk note

Article first published online: 7 SEP 2011

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