Predictors of positive outcomes following resistive inspiratory muscle training in non-ambulatory persons with advanced multiple sclerosis

Background Inspiratory muscle training (IMT) using a threshold device improves inspiratory muscle strength. What factors influence the IMT outcome has not been examined. Objective To identify predictors of the positive outcome following IMT in persons with advanced multiple sclerosis (PwAMS). Methods Inclusion criteria were non-ambulatory PwAMS, Expanded Disability Status Scale (EDSS) ≥6.5, age >18 years, no acute medical conditions, current non-smokers, and ability to consent. Participants (n = 38) performed daily inspiratory exercises using a resistive threshold device for 10 weeks. Baseline measurements included age, sex, body mass index, year post multiple sclerosis diagnosis, comorbidities, EDSS, Modified Fatigue Impact Scale-5, and oral Symbol Digit Modality Test. The percentage of completed prescribed exercise trials (Trials%) during the 10-week intervention was calculated. Age- and sex-adjusted predicted values of maximum inspiratory pressure (MIP%pred) and maximum expiratory pressure (MEP%pred) were obtained before and after the 10-week intervention. Backward multivariable regression analyses for the primary outcome (MIP%pred) were conducted. Results After controlling for the initial MIP%pred, perceived fatigue at the baseline and Trial% were significant and independent predictors of MIP%pred after IMT. Conclusion Less fatigue at the baseline and higher adherence to the prescribed exercise repetitions were positive predictors of the positive outcome following IMT in PwAMS.