Respiratory function of velopharyngeal constrictor muscles during wakefulness in normal adults. Launois, Sandrine H., Judy Tsui, J. Woodrow Weiss. Charles A. Dana Research Institute and the Harvard-Thorndike Laboratory of Beth Israel Hospital, the Beth Israel Hospital Sleep Disorders Center and the Department of Medicine, Beth Israel Hospital and Harvard Medical School, Clinical Investigator Training Program: Beth Israel Hospital - Harvard/MIT Health Sciences and Technology, in collaboration with Pfizer Inc., Boston, Massachusetts, USA
APStracts 3:0449A, 1996.
The levator veli palatini (LVP) and the superior pharyngeal constrictor (SPC) influence velopharyngeal patency and soft palate position but their behavior during respiration is incompletely characterized. To further clarify their respiratory function, we recorded electromyographic activity (EMG) in the LVP and in the SPC in awake normal subjects breathing orally. EMG data were obtained in 6 subjects for the LVP and in 9 subjects for the SPC. EMG activity and timing, and ventilation were measured during isocapnic hypoxia and hyperoxic hypercapnia. Phasic EMG activity was inconsistently present during unstimulated oral breathing. Timing of EMG phasic activity was variable for both muscles. Peak LVP activity was mainly or exclusively expiratory in 3/6 subjects. Peak SPC activity was mainly or exclusively expiratory in 5/9 subjects. With chemostimulation, recruitment of phasic activity was observed in the LVP in 4/6 subjects and in the SPC in 5/9 subjects. Tonic activity increased in 4/6 subjects for the LVP and in 3/9 subjects for the SPC. However, the response was alinear and inter-subject as well as breath-to-breath variability was substantial. In conclusion, LVP and SPC are characterized by the high inter- and intra-subject variability of EMG activity, timing of activation and response to chemostimulation. 

Received 27 February 1996; accepted in final form 10 September
1996.
APS Manuscript Number A198-6.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 5 November 1996