APStracts 2:0172A, 1995.

Hypoxic ventilatory decline: site of action. Robbins, Peter A. University Laboratory of Physiology, Parks Road, Oxford OX1 3PT, U.K.

APStracts 2:0172A, 1995.

In a recent editorial on hypoxic ventilatory decline (or depression, or roll-off, HVD), Weil (14) states, "it (HVD) is not due to a direct effect on the carotid body". Such certainty relies implicitly on the assumption that the underlying mechanisms of HVD are the same in all circumstances. However, there is reasonable evidence to suppose that there may be more than one mechanism underlying HVD, and that different mechanisms may be dominant in different situations. One mechanism might involve a progressive reduction in ventilation which is mediated centrally by hypoxia and leaves all chemoreflex sensitivities intact. Another mechanism might involve a progressive reduction of the peripheral chemoreflex sensitivity by the sustained hypoxia. With such a mechanism, the sustained hypoxia could either be acting centrally within the medulla to modulate gradually the chemoreflex sensitivity at this site, or it could be acting peripherally at the carotid body to reduce gradually the discharge within the carotid sinus nerve.

Received 8 September 1994; accepted in final form 13 April 1995.
APS Manuscript Number A946-4.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on  2 May 1995.