Inferior pharyngeal constrictor electromyographic activity during permeability pulmonary edema in lambs. V[acute]eronique, Diaz, Irenej Kianicka, Patrick Letourneau, and Jean -Paul Praud. Department of Pediatrics and Pulmonary Research Unit, Faculty of Medicine, University of Sherbrooke, Qu[acute]ebec, Canada J1H5N4
APStracts 3:0287A, 1996.
Newborn mammals exhibit an active expiratory upper airway closure during the first hours of extrauterine life. We have recently shown that permeability pulmonary edema led to active expiratory glottic closure in awake newborn lambs, while hypoxia (FiO2=8%, 15 min) did not. In the present study, we tested the hypothesis that expiratory glottic closure was accompanied by an increase in pharyngeal constrictor muscle expiratory electromyographic activity (EMG). We studied 7 awake non sedated lambs aged 8 to 20 days. Airflow (facial mask + pneumotachograph), blood gases (arterial catheter) and EMG of both the thyroarytenoid muscle (a glottic adductor) and the inferior pharyngeal constrictor muscle were recorded before and after intravenous injection of halothane (0.05 ml/Kg) to induce a permeability pulmonary edema. A central apnea (duration: 15 sec to 5 min) with continuous thyroarytenoid and inferior pharyngeal constrictor activity was observed within seconds following halothane injection. One lamb died despite rescuing maneuvers. An expiratory phasic thyroarytenoid and inferior pharyngeal constrictor muscle activity with simultaneous zero airflow gradually took place and, by 30 min after halothane injection, was present at each expiration, in the 6 remaining lambs. Expiratory glottic and pharyngeal constrictor muscle EMG was subsequently present during the whole study period (1.5 to 5 hours), even after correction of the initial hypoxia. Permeability lung edema was present at postmortem examination in all 7 lambs. We conclude that a permeability pulmonary edema induced by IV halothane in non sedated lambs enhances both glottic and pharyngeal constrictor muscle expiratory EMG. We hypothesize that expiratory contraction of inferior pharyngeal constrictor muscle could participate in the active expiratory upper airway closure; this, in turn, might improve alveolo-capillary gas exchange by increasing the end expiratory lung volume. 

Received 13 October 1995; accepted in final form 23 May 1996.
APS Manuscript Number A1106-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 28 June 96