Influence of gravity and body position on normal oral-pharyngeal swallowing. Johnsson, Folke, David Shaw, Mary Gabb, John Dent, and Ian Cook. Departments of Surgery, Radiology and Gastroenterology, Royal Adelaide Hospital, Adelaide, South Australia.
APStracts 2:0099G, 1995.
The influence of gravity, if any, on pharyngeal bolus transport is unknown. The aim of the present study was to evaluate the effect of gravity and body position on the radiological and manometric events during the normal oral-pharyngeal swallow. In 8 healthy male volunteers we performed simultaneous videoradiography and manometry using a manometry catheter incorporating a perfused sleeve measuring upper oesophageal sphincter pressure and three solid state transducers recording pharyngeal pressures. Swallows of 5 and 10 mls of barium were performed in three different body positions: upright, horizontal and 30o head down. Hypopharyngeal intrabolus pressure increased significantly in the horizontal and inverted positions compared to upright, p=0.0001. This resulted in increased maximal sphincter diameters during bolus flow (p=0.0001) and shorter duration of sphincter opening (p=0.03). As a result transsphincteric flow increased in the horizontal and inverted positions, p=0.04. Total swallowing duration, oral and pharyngeal transit time, pharyngeal peristaltic amplitude and duration, the length of the bolus in the pharynx and excursions of the hyoid and larynx were unaffected by body position. We conclude that intrabolus pressure is an important determinant of upper oesophageal sphincter opening in the healthy oro-pharynx and that gravity does not influence pharyngeal bolus transport. The healthy upper oesophageal sphincter has residual opening capacity which can be demonstrated by altering body posture. 

Received 10 February 1994; accepted in final form 8 May 1995.
APS Manuscript Number G59-4.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 26 May 1995.