Journal of Applied Physiology, Vol 57, Issue 1 271-277, Copyright © 1984 by American Physiological Society
Model analysis of tidal volume response to inspiratory elastic loads
W. A. Zin, A. Rossi, L. Zocchi and J. Milic-Emili
Based on experimental inspiratory driving pressure waveforms and active
respiratory impedance data of anesthetized cats, we made model predictions
of the factors that determine the immediate (first loaded breath) intrinsic
(i.e., nonneural) tidal volume compensation to added inspiratory elastic
loads. The time course of driving pressure (P) was given by P = atb, where
a is the pressure at 1 s from onset of inspiration and represents the
intensity of neuromuscular drive, t is time, and b is an index of the shape
of the driving pressure wave. For a given active respiratory impedance,
tidal volume compensation to added elastic loads decreases with increasing
inspiratory duration and decreasing value of b but is independent of a. We
have also assessed the validity of the "effective elastance" (Lynne-Davies
et al., J. Appl. Physiol. 30: 512-516, 1971) as a predictor of tidal volume
responses to elastic loads. In absence of vagal feedback, the effective
elastance appears to be a reliable predictor, except for short inspiratory
duration and a very high intrinsic resistance.
