Journal of Applied Physiology, Vol 57, Issue 3 839-849, Copyright © 1984 by American Physiological Society
Effect of resistive loading on inspiratory work output in anesthetized cats
L. Zocchi, S. C. Luijendijk, W. A. Zin, A. Rossi and J. Milic-Emili
In five spontaneously breathing anesthetized cats, we determined the
inspiratory elastic (Wel), resistive (Wres), and total (WI) mechanical work
rates (power) during control and first loaded inspirations through graded
linear resistances (delta R) by "Campbell diagrams" based on measurement of
esophageal pressure. WI did not change with delta R's up to 0.31 cmH2O X
ml-1 X s, the concomitant decrease in Wel being balanced by an increase in
Wres. The stability of WI in the face of delta R's was due to the vagally
mediated prolongation of inspiration and the intrinsic properties of the
respiratory system and of the contracting inspiratory muscles. To assess
the separate contributions of volume-related and flow-related intrinsic
mechanisms to the stability of WI, we made model predictions of the
immediate effects of delta R's on inspiratory mechanical work output based
on measurements of inspiratory driving pressure waves and passive and
active respiratory resistance and elastance on the same five cats. The
results suggest that the intrinsic stability of WI in the face of delta R's
is provided primarily by the active elastance.
