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.