Effects of respiratory training on obstructive sleep apnea: systematic review and meta-analysis

Purpose: This systematic review sought to answer the following focused question: “What are the effects of respiratory training devices on obstructive sleep apnea (OSA) outcomes in adults?” Methods: The acronym “PICOS” was used to determine eligibility criteria, which consists of (P population) = adults with mild to moderate OSA, (I intervention) = spirometry devices or breathing exercises, (C comparison) = compared to no breathing exercises in adults (> 18 years) with mild to moderate OSA, (O outcomes) = improved sleep quality (sleep quality indexes) and improved apnea-hypopnea indexes (AHI), (S study types) = randomized, pseudo-randomized, and nonrandomized clinical trials. The search was performed in the following databases: PubMed/Medline, LILACS, Scopus, Web of Science, Scopus, and Cochrane Library, in addition to gray literature through Google Scholar, Proquest, and Open Grey. The risk of bias was assessed using the Cochrane Collaboration tool. The certainty of the evidence was assessed using the GRADE tool. Meta-analyses of random effects were performed for the outcomes of interest. Results: A total of 1171 references were found. Applying the eligibility criteria, six studies were included in qualitative synthesis. Expiratory exercises showed a decrease in the apnea–hypopnea index (AHI) when compared to baseline (MD = − 8.4; 95% CI = − 12.4 to − 4.4; I2 = 19%). There was a decrease in values compared to baseline (MD = − 4.4; 95% CI = − 8.2 to − 0.6; I2 = 0%) for the Epworth Sleepiness Scale (ESS), when considering the inspiratory exercises. Both groups of breathing exercises showed a significant decrease in the mean index assessed by the Pittsburgh Sleep Quality Index (PSQI). Conclusion: Results of this meta-analysis suggests that breathing exercises lead to a measurable improvement in AHI for patients with mild to moderate OSA, as well as an improvement in sleep quality and daytime sleepiness.