Reliability of maximal respiratory pressures in multiple sclerosis

Objective To assess the reliability of maximal inspiratory pressure (P i max) and maximal expiratory pressure (P e max) in subjects with multiple sclerosis (MS) and healthy control subjects by identifying the number of testing sessions and the number of measurements needed in a single testing session to obtain consistent, reproducible results. Design A descriptive, comparative design with repeated measures was used. Setting Four sets of 10 P i max and 10 P e max measurements were obtained over a 4-week period from MS subjects in their homes. The same measurements were obtained from healthy control subjects in a private setting. Subjects Seventy-two MS patients and 61 healthy control subjects participated in the study. Measurement P i max and P e max values were obtained by using previously published methods. Results Mean P e max and P i max values for MS patients differed over the first three of the four testing sessions. By contrast, mean P e max and P i max values for healthy control subjects differed only when the first session values were compared with values from the last three sessions. For MS patients, P e max and P i max increased between the first and 10th trial during the first testing session, but not during the subsequent three sessions. Conclusions The results of this study suggest that several practice sessions should be provided in order to obtain reliable P e max and P i max values in persons with MS. At least one practice session should be provided for healthy control subjects before identifying a baseline.