Relative effects of flow-resistive and pressure-biased respiratory loading

The effects of pressure-biased breathing (PBB), which simulates positive pressure respirator use, were studied in 15 volunteer subjects during laboratory exercise. PBB was compared with inspiratory resistance: dead space (ID) load and a no-load (N) situation. PBB had adverse subjective effects comparable with those of ID. Physiologically, PBB led to a small decrease in inspiratory time and an increase in expiratory time as well as an increase in the intensity of ventilatory effort as measured by the mean inspiratory flow rate. It is postulated, based on these findings, that PBB has significant effects on the resting lung volume, leading to both physiologic and subjective consequences.