LIFE WITHOUT VENTILATORY CHEMOSENSITIVITY

In healthy humans ventilatory chemoreception results in exquisite regu lation of arterial blood gases during NREM sleep, but during wakefulne ss other behavioral and arousal-related influences on breathing compet e with chemoreceptive respiratory control. This paper examines the ext ent of chemoreceptive control of breathing within the normal physiolog ical range in awake and sleeping humans and explores the consequences upon breathing of absent chemoreceptive function. Recent studies of su bjects with congenital central hypoventilation syndrome (CCHS) demonst rate the extent of behavioral and arousal-related influences on breath ing in the absence of arterial blood gas homeostasis. CCHS subjects la ck chemoreceptor control of breathing and seriously hypoventilate duri ng NREM sleep, requiring mechanical ventilation. Many CCHS subjects br eathe adequately during many waking behaviors associated with arousal, cognitive activity or exercise-presumably reflecting input to the bra instem respiratory complex from the reticular activating system, the f orebrain or mechanoreceptor afferents. In most situations, and despite changes in metabolism, the non-chemoreceptive inputs to breathing res ult in surprisingly well controlled arterial blood gases in CCHS patie nts. (C) 1997 Elsevier Science B.V.