Journal of Applied Physiology, Vol 55, Issue 2 329-334, Copyright © 1983 by American Physiological Society
High-frequency ventilation lengthens expiration in the anesthetized dog
R. Banzett, J. Lehr and B. Geffroy
We tested the response of nine barbiturate-anesthetized dogs to
high-frequency ventilation (HFV) (40-55 ml tidal volumes at 15 Hz) while
measuring and controlling lung volume and blood gases. When lung volume and
PCO2 were held constant, six of the nine responded to HFV by lengthening
expiration. In each of these six dogs the maximal response was apnea. The
response was immediate. In submaximal responses only expiration was
changed; inspiratory time and peak diaphragmatic electrical activity were
unaffected. There was a variable effect on abdominal muscle activity. If
mean expiratory lung volume was allowed to increase at the onset of HFV,
the Hering-Breuer inflation reflex added to the response. The strength of
the response depended on level of anesthesia and arterial PO2. Vagotomy
abolished the response in all cases. We conclude that oscillation of the
respiratory system reflexly prolongs expiration via mechanoreceptors,
perhaps those in the lungs.
