Should respiratory muscle training be part of the treatment of Parkinson's disease? A systematic review of randomized controlled trials

Objective: To determine the effectiveness of respiratory muscle training in persons with Parkinson's disease.

Data sources: PubMed/MEDLINE, EMBASE, Web of Science, Scopus and PEDro electronic databases were searched until 15 November 2019. Reference lists of included studies were hand-searched.

Methods: Randomized controlled trials assessing the effects of respiratory muscle training programmes (both inspiratory and expiratory) in patients with Parkinson's disease were included. Two reviewers independently identified eligible studies and extracted data. Method quality was appraised with the PEDro scale.

Results: Five papers including three randomized controlled trials with a total of 111 patients were identified. Method appraisal showed a mean score of 5 in the PEDro scale. One study analysed inspiratory muscle training, one expiratory muscle training and two established a comparison between both of them. Statistically positive results were found in maximal inspiratory pressure (P < 0.05 and d = 0.76), maximal expiratory pressure (P < 0.01 and d = 1.40), perception of dyspnoea (P < 0.01), swallowing function (d = 0.55) and phonatory measures, without significant differences in spirometric indices.

Conclusions: Respiratory muscle training may be an effective alternative for improving respiratory muscle strength, swallowing function and phonatory parameters in subjects with Parkinson's disease. Nevertheless, the lack of primary studies about this type of training prevents obtaining robust evidence.