STANDARDIZATION OF BAROSTAT PROCEDURES FOR TESTING SMOOTH-MUSCLE TONEAND SENSORY THRESHOLDS IN THE GASTROINTESTINAL-TRACT

An international working team of 13 investigators met on two occasions to develop guidelines for standardizing the procedures used to test g astrointestinal muscle tone and sensory thresholds using a barostat. G eneral recommendations were: (1) Use a thin-walled plastic bag that is infinitely compliant until its capacity is reached. Maximum diameter of the bag should be much greater than the maximum diameter of the vis cus. (2) The pump should be able to inflate the bag at up to 40 ml/sec . (3) Pressure should be monitored inside the bag, not in the pump or inflation line. (4) Subjects should be positioned so that the bag is c lose to the uppermost surface of the body. (5) For rectal tests, bowel cleansing should be limited to a tap water enema to minimize rectal i rritation. Oral colonic lavage is recommended for studies of the proxi mal colon, and magnesium citrate enemas for the descending colon and s igmoid. (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 adaptation before testing is adequate if no air or dr ugs were used. (7) The volumes reported must be corrected for the comp ressibility of gas and the compliance of the pump, which is greater fo r bellows pumps than for piston pumps. (8) Subjects should be tested i n the fasted state. For evaluation of muscle tone: (9) The volume of t he bag should be monitored for at least 15 min. For evaluation of sens ory thresholds: (10) It is recommended that phasic distensions be grea ter than or equal to 60 sec long and that they be separated by greater than or equal to 60 sec. (11) Sensory thresholds should be reported a s bag pressure rather than (or in addition to) bag volume because pres sure is less vulnerable to measurement error. (12) Tests for sensory t hreshold should minimize psychological influences on perception by mak ing the amount of each distension unpredictable to the subject. (13) P ain or other sensations should be reported on a graduated scale; not ' 'yes-no.'' The working team recommends verbal descriptor scales, conta ining approximately seven steps, or visual analog scales in which subj ects place a mark on a straight line marked ''none'' on one end and '' maximum'' on the other end. (14) It is recommended that subjects shoul d be asked to rate the unpleasantness of distensions separately from t heir intensity.