Breathing pattern in men during inspiratory elastic loads

Abstract

Breathing pattern was studied in men during inspiratory elastic load applied throughout breathing cycle (CL) or inspiration only (DL). VT decreased similarly under both loads: 40% during 1st loaded breath (1st), 25% after 1 min (min); so did Ti (15% at 1st, 25% at min); Te decreased by 35% under CL, 25% under DL, at both times. Under DL expiratory flow started after a lag of about 0.4 sec, required to raise alveolar pressure above atmospheric. In all subjects the inspiratory muscles activity increased at 1st and in 6 out of 8 the ventilatory response at min was essentially neurogenic. At 1st all subjects recruited expiratory muscles, decreasing FRC by 100--300 ml under DL' in most this phenomenon was negligible at min. Rate of decrease of inspiratory muscle pressure during period of zero flow under DL was proportional to end-inspiratory muscle pressure (Pmuse.i.) and to Pmuse.i./Ti. At beginning of expiration dPmus/dt was greater under DL: under this period difference of Pmus between CL and DL seems mainly due to muscle intrinsic properties.