AJP - Gastrointestinal and Liver Physiology, Vol 250, Issue 6 773-G780, Copyright © 1986 by American Physiological Society
Measurement of resistance to flow across antroduodenal area during fasting
F. Mearin, F. Azpiroz and J. R. Malagelada
Changes in antroduodenal resistance to flow may participate in the
regulation of gastric emptying and duodenogastric reflux. Little is known,
however, about the relationship between antroduodenal resistance and the
physiological patterns of contractile activity in this area. We have
developed an instrument that maintains an electronically regulated
constant-pressure gradient of 2 mmHg across both ends of a flaccid cylinder
positioned fluoroscopically across the pylorus. Because resistance bears a
constant inverse relationship to flow at a fixed pressure gradient, changes
in the recorded rate of airflow through the cylinder are a measure of
antroduodenal resistance. In vitro studies showed that, under these
conditions, airflow was a function of the diameter and length of the air
path and the frequency and duration of external pressure waves greater than
2 mmHg. In vivo studies in four dogs examined the relationship between
interdigestive phases of motor activity and variations in resistance
exerted by the antroduodenal area. We found that flow rates varied markedly
with each phase. Antroduodenal resistance was lowest during motor
quiescence (phase I), rose gradually during irregular activity (phase II),
and reached its peak during maximal contractile activity (phase III) (P
less than 0.05). Resistance was similar for antegrade and retrograde flow.
Additional studies suggested that the pyloric area contributes mostly to
resistance during phase I, whereas duodenal resistance at least matches
that of the pylorus during phase III.
