Journal of Applied Physiology, Vol 51, Issue 1 109-121, Copyright © 1981 by American Physiological Society
Phrenic activity, respiratory pressures, and volume changes in cats
N. M. Siafakas, R. Peslin, M. Bonora, H. Gautier, B. Duron and J. Milic-Emili
In eight anesthetized cats we measured the integrated ("moving time
average") phrenic activity [using phrenic electroneurogram (EPHR)] and the
active transdiaphragmatic pressure [Pdi(mus)] during room air breathing,
hypoxia, and hypercapnia. The relationship between Pdi(mus) and EPHR was
unaffected by either hypoxic or hypercapnic stimulation of breathing,
suggesting that in spontaneously breathing cats the pressure losses are
negligible. In all cats, however, there was a substantial volume-related
decrease in Pdi(mus), indicating that with increasing lung volume the
effectiveness of the diaphragm as a pressure generator decreases. In
addition, we have developed a model that allows prediction of the time
course changes in lung volume for different morphology of inspiratory
driving pressure. This model explains many of the features of control of
breathing found experimentally in our cats.
