The purpose of the present study was to obtain the immediate CO2 storage capacity at the onset of exercise. The CO2 stores at the onset of the exercise were calculated from the difference between the respiratory gas exchange ratio (R) and the metabolic gas exchange ratio (RQ; R obtained at 5.5min of exercise). The CO2 stores per body weight (CO2 stores/w) were linearly related to the CO2 pressure (P′VCO2) determined by the CO2 rebreathing method (r=0.713, p<0.001), the slope being 0.330ml/(mmHg•kg). The CO2 stores were then corrected for change in O2 stores with exercise, that defined as total CO2 stores. P′VCO2 was also corrected for the effect of lung-bag volume shrinkage and Haldane effect during CO2 rebreathing, that defined as true PVCO2. The total CO2 stores/w were also related linearly to the true P′VCO2 (r=0.725, p<0.001), the slope of the regression line defined as the immediate CO2 storage capacity being 0.650ml/(mmHg•kg).
Physiological Society of Japan