DECAY-RATE OF INSPIRATORY MUSCLE PRESSURE DURING EXPIRATION IN MAN

Decay rate of inspiratory muscle pressure (Pmus1) was studied in 4 subjects during post-inspiratory period of zero flow (TEz) occuring discontinuous inspiratory elastic load (DIL). End-inspiratory pressure (PmuseI) was increased by dead spaces or excercise. Decay rate was related to PmuseI by a power function with exponent >1. It was not directly affected by concomitant changes of PCO. It did not increase when an expiratory resistive load was added, i.e. when braking action of inspiratory muscles was no longer required. Time course of Pmus1 during TEz was more straight than exponential. Relative decay rate increased with PmuseI and with decrease of inspiratory or expiratory time. Experiments with resistive loads suggest that relative rate is mainly related to timing factors. During voluntary inspiratory efforts with closed airways, relatively decay rate was not related to PmuseI, while decay rate increased linearly with PmuseI. © 1979.