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

TY - JOUR

T1 - Increased steady-state VO2 and larger O2 deficit with CO2 inhalation during exercise

AU - Østergaard, L.

AU - Kjær, K.

AU - Jensen, K.

AU - Gladden, L.B.

AU - Martinussen, Torben

AU - Pedersen, P.K.

PY - 2012/3

Y1 - 2012/3

N2 - Aim: To examine whether inhalation of CO 2-enriched gas would increase steady-state during exercise and enlarge O 2 deficit. Methods: Ten physically active men (53.7±3.6mLmin -1kg -1; ±SD) performed transitions from low-load cycling (baseline; 40W) to work rates representing light (≈ 45%; 122±15W) and heavy (≈ 80%; 253±29W) exercise while inhaling normal air (air) or a CO 2 mixture (4.2% CO 2, 21% O 2, balance N 2). Gas exchange was measured with Douglas bag technique at baseline and at min 0-2, 2-3 and 5-6. Results: Inhalation of CO 2-enriched air consistently induced respiratory acidosis with increases in PCO 2 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 40-50Lmin -1; P<0.01), and a substrate shift towards increased lipid oxidation (decline in R 0.12; P<0.01). during the first 2min of exercise were not significantly different whereas the increase in from min 2-3 to min 5-6 in heavy exercise was larger with CO 2 than with air suggesting a greater slow component. As a result, O 2 deficit was greater with hypercapnia in heavy exercise (2.24±0.51L vs. 1.91±0.45L; P<0.05) but not in light (0.64±0.21L vs. 0.54±0.20L; ns). Conclusion: Inhalation of CO 2-enriched air and the ensuing respiratory acidosis increase steady-state in both light and heavy exercise and enlarges O 2 deficit in heavy exercise.

AB - Aim: To examine whether inhalation of CO 2-enriched gas would increase steady-state during exercise and enlarge O 2 deficit. Methods: Ten physically active men (53.7±3.6mLmin -1kg -1; ±SD) performed transitions from low-load cycling (baseline; 40W) to work rates representing light (≈ 45%; 122±15W) and heavy (≈ 80%; 253±29W) exercise while inhaling normal air (air) or a CO 2 mixture (4.2% CO 2, 21% O 2, balance N 2). Gas exchange was measured with Douglas bag technique at baseline and at min 0-2, 2-3 and 5-6. Results: Inhalation of CO 2-enriched air consistently induced respiratory acidosis with increases in PCO 2 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 40-50Lmin -1; P<0.01), and a substrate shift towards increased lipid oxidation (decline in R 0.12; P<0.01). during the first 2min of exercise were not significantly different whereas the increase in from min 2-3 to min 5-6 in heavy exercise was larger with CO 2 than with air suggesting a greater slow component. As a result, O 2 deficit was greater with hypercapnia in heavy exercise (2.24±0.51L vs. 1.91±0.45L; P<0.05) but not in light (0.64±0.21L vs. 0.54±0.20L; ns). Conclusion: Inhalation of CO 2-enriched air and the ensuing respiratory acidosis increase steady-state in both light and heavy exercise and enlarges O 2 deficit in heavy exercise.

U2 - 10.1111/j.1748-1716.2011.02342.x

DO - 10.1111/j.1748-1716.2011.02342.x

M3 - Journal article

C2 - 21791016

SN - 1748-1708

JO - Acta Physiologica

JF - Acta Physiologica

ER -