Dynamic and steady-state respiratory responses to bicycle exercise.

The transient respiratory responses of 10 normal male volunteers to step changes in work load from 0 to 300, 600, and 800 kpm/min were determined by breath-by-breath analysis for tidal volume, minute ventilation, respiratory frequency, end-tidal oxygen and carbon dioxide tensins, oxygen uptake, carbon dioxide elimination, respiratory exchange ratio, and heart rate. Ten experiments were averaged on a 5-s interval basis. Quantitative measures of the dynamics (delay times, half-times, times to peaks, times to plateaus, and plateau amplitudes) are presented. These parameters generally vary with work load and reflect the speed of response of various components of the system. Rapid ventilatory responses were seen at the initiation and termination of exercise; however, they required up to 32.5 s for full development. Repeated runs on three subjects at 600 kpm/min indicate that the experiments are grossly repeatable. The data, at the initiation of exercise, are consistent with the concept of cardiodynamic hyperpnea while the results are not as clear-cut at the termination of exercise.