Journal of Applied Physiology, Vol 51, Issue 6 1484-1487, Copyright © 1981 by American Physiological Society
Vagotomy reverses apnea induced by high-frequency oscillatory ventilation
W. K. Thompson, B. E. Marchak, A. C. Bryan and A. B. Froese
Apnea has been observed in both animals and patients during high-frequency
oscillatory ventilation. The effects of vagotomy were studied during
periods of oscillator-induced apnea in 11 pentobarbital-anesthetized dogs.
The animals were intubated and breathing spontaneously. An arterial cannula
was inserted for monitoring blood pressure and blood gases. Intratracheal
airway pressure was measured, and respiratory activity was assessed using
either an intrapleural catheter or esophageal balloon. The dogs then
underwent high-frequency ventilation at 15 Hz. Apnea was induced by
appropriate selection of volume displacement of the piston pump and the
distal airway pressure in eucapnic animals. Segments of right and left
vagus nerves were exposed in the neck, bathed in local anesthetic, and
transected. Spontaneous ventilation resumed immediately in nine animals and
could not be suppressed at the same CO2 partial pressure despite
continuation of oscillation. We conclude that the apnea observed during
high-frequency ventilation is mediated by active vagal inhibition of
central respiratory activity and is usually reversed by vagotomy.
