Hemodynamics in teenagers and asthmatic children during exercise.

Seventeen normal teenagers and eight asthmatic children were studied during submaximal exercise on a bicycle ergometer. A modification of a noninvasive multiple gas rebreathing method was utilized for the estimation of pulmonary capillary blood flow (Qc), diffusing capacity (DL), oxygen consumption (VO2), functional residual capacity (FRC), and pulmonary tissue plus capillary blood volume (VTPC). Significant increases in Qc, DL, VO2, and heart rate occurred in both groups of subjects. Regression equation of Qc equaled 6.0 + 0.0078 VO2 (ml/min) in the teenagers and 3.39 + 0.0082 X VO2 (ml/min) in the asthmatic children. The values of DL as a function of VO2 in both groups were similar to previously reported data. No significant changes in FRC or VTPC occurred in either group during exercise. This method appears to be an acceptable noninvasive way of studying exercise physiology in healthy or sick children.