Kinetics of gas exchange and ventilation in transitions from rest or prior exercise.

Seven normal subjects each performed three transitions to a subanaerobic threshold work rate on a cycle ergometer: 1) from rest, 2) from a low work rate (both at 60 rpm), and 3) from a low work rate at 40 rpm to the high work rate at 80 rpm. Oxygen uptake (VO2), carbon dioxide output (VCO2), and ventilation (VE) were computed breath-by-breath and response kinetics extracted. The mean half-times of VO2, VCO2, and VE were 32, 44, and 49 s, respectively, and were not appreciably affected by the prior exercise or by variation of pedal rate. The kinetics of VE was highly correlated with VCO2 (r = 0.94), with VCO2 leading VE, providing further description of the relation of the exercise hyperpnea to CO2 flow to the lungs.