RESPIRATORY RESPONSES TO TRACHEOBRONCHIAL STIMULATION DURING SLEEP AND WAKEFULNESS IN THE ADULT CAT

The response to tracheal stimulation (50 mu l of tap water) during wak efulness, non-rapid eye movement (NREM) sleep and rapid eye movement ( REM) sleep was investigated in adult cats. In wakefulness, repetitive coughing occurred on 80% of the trials. In NREM and REM sleep, the mos t frequent response (approximately 69% and 58% of the trials, respecti vely) was arousal, followed by coughing, Apneas occurred following the stimulus and before arousal in 11% and 24% of the trials in NREM and REM sleep, respectively. In NREM sleep, the tracheal stimulus sometime s evoked expiratory efforts following a normal inspiratory effort (11% of the trials). These were much weaker than the expiratory efforts du ring coughing in wakefulness. In REM sleep, stimulation in 11% of the trials elicited increased inspiratory efforts. Although these may have been diminutive preparatory inspirations for coughing, they were much smaller than preparatory inspirations associated with coughing in wak efulness, and they were never followed by active expiratory efforts. A rousal from either NREM or REM sleep in response to tracheal stimulati on was sometimes associated with an augmented breath. This response, w hich is common upon spontaneous arousal, may lead to deeper aspiration of the tracheal fluid. We conclude that in cats coughing requires wak efulness and that airway stimuli in sleep cause a variety of respirato ry responses, some of which may be maladaptive.