AROUSAL AND CARDIORESPIRATORY RESPONSES TO AIR-FLOW OBSTRUCTION IN SLEEPING LAMBS - EFFECTS OF SLEEP STATE, AGE, AND REPEATED OBSTRUCTION

We studied the effects of postnatal age on arousal and cardiorespirato ry responses to airflow obstruction in sleeping lambs; we also determi ned the influence of sleep states and repeated airflow obstruction. Si xteen lambs were chronically prepared for monitoring sleep states, art erial O-2 saturation (SaO(2)), heart rate (HR), and intrapleural press ure (Ppl) and were studied from 2-29 days after birth. Obstruction of respiratory airflow by facemask occlusion led to arterial desaturation , augmentation of respiratory efforts, bradycardia, and arousal. Lambs aroused more rapidly and with less desaturation in non-rapid eye move ment (NREM) sleep (7 +/- 1 second and 7 +/- 1%, respectively) than in rapid eye movement (REM) sleep (18 +/- 2 seconds and 22 +/- 2%), and c ardiac slowing was less in NREM than in REM sleep. In REM sleep only, the arousal latency and desaturation at arousal were affected by postn atal age; arousal responses occurred most rapidly in the youngest (les s than or equal to 6 days) and oldest (greater than or equal to 13 day s) age groups and were delayed at 7-12 days. Repeated episodes of airf low obstruction led to reduced arousability in REM sleep only. We conc lude that arousal from REM, but not NREM, sleep in response to the obs truction of respiratory airflow is transiently depressed during early postnatal development and that repeated obstructions and arousals also lead to depressed arousal from REM sleep.