Arousal responses to chemical stimuli during sleep

Arousal from sleep is an important component of any co-ordinated response to an external stimulus. Respiratory stimuli imposed during sleep are capable of eliciting arousal responses as well as the classic ventilatory responses Considerable survival advantage may result as a consequence of intact arousal mechanisms. Developmental studies of arousal responses to respiratory stimuli are lacking. Arousal responses to chemoreceptor stimuli have been examined in adult tracheotomized dogs, both before and following bilateral surgical denervation of the carotid bodies. Prior to denervation of the carotid bodies arousal in response to isocapnic progressive hypoxia occurred at an arterial oxygen saturation (SaO2) of 83% during slow-wave sleep and 70% in rapid-eye-movement sleep. Airway occlusion induced arousal from Slow-wave-sleep at SaO2 of 88% and from rapid-eye-movement sleep at SaO2 of 84%. Following denervation of the carotid bodies, arousal failed to occur in response to either progressive hypoxia or airway occlusion despite desaturation to 60% in Slow-wave sleep and 50% in rapid-eye-movement-sleep, at which level experiments were arbitrarily terminated. The effect of sleep fragmentation on arousal responses of sleeping dogs to chemoreceptor stimuli has also been studied. A marked impairment of both hypoxic and hypercapnic arousal was produced by sleep fragmentation. The consequences of interfering with arousal mechanisms in experimental animals indicates the considerable potential for similar dysfunction in man to contribute to the pathophysiology of the clinical syndromes of obstructive sleep apnoea and sudden infant death.(ABSTRACT TRUNCATED AT 250 WORDS)