The effects of positive airway pressure on upper airway dilator
muscle activity and ventilatory timing .
Deegan, P. C., P. Nolan, M. Carey, W. T. McNicholas.
Department of Respiratory Medicine and the Respiratory Sleep
Laboratory, St. Vincent's Hospital and the Department of Human
Anatomy and Physiology, University College, Dublin, Ireland
APStracts 3:0099A, 1996.
To determine upper airway (UA) and ventilatory responses to nasal
continuous positive airway pressure (NCPAP) and expiratory positive
airway pressure (EPAP), we quantitated changes in alae nasi (AN) and
genioglossus (GG) electromyographic (EMG) activity, ventilatory
timing and end-expiratory lung volume (EELV) at various levels of
CPAP and EPAP in six normal subjects during wakefulness and seven
during sleep. The same measurements were also made before and after
UA anesthesia in six normal subjects during wakefulness. During both
wakefulness and sleep, CPAP application significantly increased EELV
and decreased AN and GG EMG activities. In contrast EPAP
significantly increased EMG activities of both muscles, while also
increasing EELV during wakefulness. The EMG responses were less
marked during sleep. Anesthesia of the UA abolished the EMG responses
to CPAP but not to EPAP. These results suggest that, in normals, CPAP
application causes a reflex reduction in UA dilator muscle activity
mediated by UA sensory receptors. In contrast, EPAP increases UA
dilator muscle activity, with the response mediated by conscious
influences or reflexes arising outside of the UA.
Received 14 September 1995; accepted in final form 5 February
1996.
APS Manuscript Number A1006-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 14 February 96