Effect of short-term CO2-breathing on the CO2 content and intracellular pH in skeletal muscle of man.

Subjects inhaled air with 8% CO2 for 10 min. Carbon dioxide tension in arterial blood increased rapidly from about 5 kPa to 7 kPa, whereas venous CO2 tension increased more slowly, reaching the arterial value at the end of the CO2-breathing period. Muscle content of total CO2 (HCO-3, H2CO3, solubilized CO2) did not change during CO2-breathing or the following 15 min of recovery. However, when CO2-breathing was combined with light bicycle exercise, total CO2 increased by 30%. This could be an effect of both increased local circulation and increased endogenous CO2 production in the muscle. It is concluded that 10 min CO2-breathing alone is insufficient to affect CO2 content and intracellular pH in resting skeletal muscle.