Role of airway resistance in the control of ventilation during exercise

Publisher Website
Google Scholar
Abstract
The interdependence of respiratory drive, ventilation and airway resistance during exercise, mouth occlusion pressure (P0.1), minute ventilation (.ovrhdot.V) and mean inspiratory flow (VT/TI) were studied in 8 normal subjects [human] performing cycle-ergometer exercise at loads ranging from 0 W to 200 W under 2 different ambient conditions: during O2 breathing at 1.3 ATA [atmospheres absolute] and during air breathing at 6 ATA (PO2 = 1.3 ATA). Comparison of measurements at 6 ATA with those at 1.3 ATA indicated that a 4.2-fold increase in respired gas density (D) had little or no influence on the .ovrhdot.V and VT/TI responses whereas P0.1 at any given VT/TI was increased by a factor of 1.9. In both conditions, PO.1 increased at a faster rate than VTTI as the work load increased. At loads higher than 40 W, the relationship between between P0.1, D and VT/TI was found to approximate the equation P0.1 = K .cntdot. D0.5(VT/TI), where K is a constant that varies among subjects. The ratio P0.1/(VT/TI), an estimate of respiratory impedance, increased with both D and VT/TI. Evidence is presented that the respiratory drive was reflexly enhanced in response to loading as airway resistance increased with D and/or VT/TI. Neural mechanisms compensating for internal flow-resistive loading evidently play an important role in the control of ventilation during exercise, both at normal and at raised air pressures.