DISTENSION-RELATED RESPONSES IN CIRCULAR AND LONGITUDINAL MUSCLE OF THE HUMAN ESOPHAGUS - AN ULTRASONOGRAPHIC STUDY

Both circular muscles (CM) and longitudinal muscles (LM) of the esopha gus participate in peristalsis. Various measurement techniques have yi elded conflicting information as to the temporal correlation between c ontraction in the two muscle layers. High-frequency intraluminal ultra sound (HFIUS) is a novel technique to detect contraction of LM and CM of the esophagus. We investigated the temporal correlation between the CM and LM contraction during ascending excitatory and descending inhi bitory reflexes using HFIUS. A manometric catheter equipped with two b alloons and a 12.5-MHz ultrasound transducer catheter was used to stud y 10 normal healthy subjects. The changes in muscle thickness and pres sure, proximal and distal to esophageal distension, were recorded at 5 and 10 cm above the lower esophageal sphincter (LES). The esophageal distension induced an increase in pressure and an increase in muscle t hickness of both CM and LM layers proximal to the distension site. The onset of increase in muscle thickness and peak muscle thickness in tw o layers occurred at the same time. There was a close temporal correla tion between the changes in pressure and changes in muscle thickness. Atropine inhibited the distension-related pressure and muscle thicknes s increase in both layers. Distal to the esophageal distension, there was no change in pressure but a decrease in the thickness of the two m uscle layers. The decrease in muscle thickness of the two layers occur red at the same time. The responses of the two muscle layers to disten sion were similar at 5- and 10-cm sites above the LES. HFIUS is a rela tively noninvasive technique to study the LM layer response during per istalsis in vivo. Our data indicate that the two muscle layers may con tract and relax together during distension-related peristaltic reflexe s in the esophagus.