Alternative or adjunctive rehabilitation treatments have emerged for obstructive sleep apnea (OSA) to address low patient compliance with conventional treatments, improve sleep quality, and reduce the number of apnea episodes.

To conduct a comprehensive review of respiratory muscle training as a therapeutic adjunct for OSA. Namely, oromyofunctional therapies (OMF), inspiratory muscle training (IMT), and expiratory muscle training (EMT).

English language articles were selected from the PubMed, Cochrane Library, and ASHA databases, and their methodological quality was assessed using AMSTAR 2. A qualitative review and random-effects meta-analyses were performed on the variables of interest. Because of a specific focus on rehabilitation approaches, we excluded pharmacological therapies and hypoglossal nerve stimulation, thereby centering the research on airway musculature.

A total of 247 articles were identified. Four studies were selected for review, comprising a total of 1468 adult patients and 106 pediatric patients. The meta-analyses showed that only OMF, as an adjunctive or stand-alone therapy (mean difference, MD −14.26 events/hour; P < 0.0001; CI 95% −20.98 to −7.54) and EMT (MD −8.42 events/hour; P < 0.0001; CI 95% −12.41 to −4.43) significantly reduced the apnea-hypopnea index (AHI). However, the 3 therapies were all effective in reducing daytime sleepiness (MD −3.50/24 points; P = 0.003; 95% CI −5.78 to −1.22), and IMT, EMT, or a combination of both also improved sleep quality (MD −2.75, P = 0.01; 95% CI −4.85 to −0.66).

The results of this review suggest that respiratory muscle training improves AHI and has a beneficial effect on clinical symptoms such as sleep quality and daytime sleepiness. Included studies are based on a low level of evidence, despite the generally good methodological quality of the systematic reviews.