, Volume 42, Issue 2, pp 223-241

Standardization of Barostat Procedures for Testing Smooth Muscle Tone and Sensory Thresholds in the Gastrointestinal Tract

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Abstract

An international working team of 13 investigatorsmet on two occasions to develop guidelines forstandardizing the procedures used to testgastrointestinal muscle tone and sensory thresholds usinga barostat. General recommendations were: (1) Use athin-walled plastic bag that is infinitely compliantuntil its capacity is reached. Maximum diameter of thebag should be much greater than the maximum diameter of the viscus. (2) The pump should be able toinflate the bag at up to 40 ml/sec. (3) Pressure shouldbe monitored inside the bag, not in the pump or inflationline. (4) Subjects should be positioned so that the bag is close to the uppermost surface of thebody. (5) For rectal tests, bowel cleansing should belimited to a tap water enema to minimize rectalirritation. Oral colonic lavage is recommended for studies of the proximal colon, and magnesiumcitrate enemas for the descending colon and sigmoid. (6)If sedation is required for colonic probe placement,allow at least one hour for drug washout and clearance of insufflated air. Ten to 20 min of adaptationbefore testing is adequate if no air or drugs were used.(7) The volumes reported must be corrected for thecompressibility of gas and the compliance of the pump, which is greater for bellows pumps thanfor piston pumps. (8) Subjects should be tested in thefasted state. For evaluation of muscle tone: (9) Thevolume of the bag should be monitored for at least 15 min. For evaluation of sensory thresholds:(10) It is recommended that phasic distensions be ≥60sec long and that they be separated by ≥60 sec. (11)Sensory thresholds should be reported as bag pressure rather than (or in addition to) bag volumebecause pressure is less vulnerable to measurement error.(12) Tests for sensory threshold should minimizepsychological influences on perception by making the amount of each distension unpredictable to thesubject. (13) Pain or other sensations should be reportedon a graduated scale; not “yes-no.” Theworking team recommends verbal descriptor scales,containing approximately seven steps, or visual analogscales in which subjects place a mark on a straight linemarked “none” on one end and“maximum” on the other end. (14) It isrecommended that subjects should be asked to rate the unpleasantness ofdistensions separately from their intensity.