Braking of expiratory airflow in obese pigs during wakefulness and sleep

Braking of expiratory airflow is a phenomenon prominently seen in neonates where it is thought to defend end-expiratory lung volume. This paper descri bes pronounced expiratory braking in an adult animal. the obese Vietnamese pot-bellied pig. Three obese pigs were chronically instrumented for recordi ng of intrapleural pressure and bioelectric signals related to sleep. Airfl ow was measured by a pneumotachograph attached to a facemask. Expiratory ai rflow resistance was calculated for 10 consecutive expirations during wakef ulness, NREM, and REM sleep. All animals demonstrated a biphasic expiratory flow pattern characterized by an initial plateau in flow at a low value fo llowed by a rapid increase later in expiration. Airflow resistance during e arly expiration was on average four-fold higher than during late expiration . A striking observation was the maintenance of pronounced expiratory braki ng during NREM and REM sleep. Expiratory braking in these animals is likely due to laryngeal mechanisms and may serve to preserve end-expiratory lung volume or improve hemodynamics. (C) 2001 Elsevier Science B.V. All rights r eserved.