Role of the carotid body and of afferent vagal stimuli in the arousal response to airway occlusion in sleeping dogs.

We studied the independent effects of bilateral carotid body denervation and bilateral cold blockade of the vagus nerves on the arousal response to airway occlusion during sleep. Dogs breathed through a cuffed endotracheal tube inserted via a chronic tracheostomy, and airway occlusion was imposed at end-expiration and maintained until the moment of arousal. Arterial O2 saturation (SaO2) was measured with an ear oximeter, and sleep stage was determined by electroencephalographic and behavioral criteria. Mean +/- SE SaO2 values at arousal were 88.7 +/- 2.7% during slow-wave sleep, and 84.9 +/- 3.5% during rapid-eye-movement sleep (0.05 less than p less than 0.1). After carotid body denervation (2 dogs), arousal SaO2 values were less than 60% during slow-wave sleep and less than 50% during rapid-eye-movement sleep, at which time airway occlusion was arbitrarily terminated. In a few studies after denervation, when airway occlusion was maintained beyond these values, the dogs occasionally failed to arouse at all, and resuscitation was required. Bilateral cold blockade of the vagus nerves (2 dogs) resulted in no significant change in SaO2 at arousal. We concluded that the arousal response to airway occlusion is mediated primarily by the carotid bodies.