ABDOMINAL MUSCLE-ACTIVITY IN CONSCIOUS DOGS - EFFECT OF SLEEP AND ROUTE OF BREATHING

Abdominal muscle activity (EMGabd) was studied in 4 adult dogs during wakefulness and sleep. The dogs were previously prepared with a permanent side-hole tracheal stoma, and were trained to sleep with a tightly-fitting snout mask, hermetically sealed in place. They breathed either through a cuffed endotracheal tube inserted distally into the tracheal stoma (tracheal) the upper airway, with the tracheal stoma plugged (nasal). Sleep state was determined by behavioural, electroencephalographic and electromyographic criteria. EMGabd activity was measured using fine bipolar needles inserted into the abdominal muscle layers. Expiratory EMGabd augmented progressively from sleep onset to SWS regardless of route of breathing, and without major changes in the animal's ventilation. Maximal EMGabd occurred in SWS during nasal breathing; EMGabd increased from a mean of 16.6 ± 0.3 mV awake, to 23.8 ± 0.3 mV in SWS, representing an overall increase of 55.0 ± 7.5% from the awake level. EMGabd increased similarly during tracheal breathing, with an overall increase of 62.0 ± 15.4% in SWS. We conclude that the consistent augmentation of expiratory EMGabd activity in sleep indicates that expiration in the dog is an active process, which is enhanced during nasal breathing and NREM sleep. © 1990.