Purpose: Obstructive sleep apnoea (OSA) negatively impacts quality of life and increases cardiovascular and metabolic risks. Although continuous positive airway pressure is the gold-standard treatment, limited adherence reduces its clinical effectiveness. This study investigates whether steam-assisted respiratory muscle training (RMT) can alleviate symptoms, improve pulmonary function, and explore potential differences in response between men and women with OSA.

Methods: This open-label, 12-week prospective pilot study included 60 participants with mild to moderate OSA, who performed individualized inspiratory and expiratory counter-pressure breathing exercises with steam inhalation. Pulmonary function tests, sleep-related questionnaires, and general health assessments were conducted at baseline and post-intervention. Participants showing notable improvements from baseline were classified as high responders, enabling subgroup analyses.

Results: Final results of 33 of the 60 participants showed significant mean improvements, with the Insomnia Severity Index (ISI) decreasing by 1.8 points, the Pittsburgh Sleep Quality Index (PSQI) by 2 points, and the 12-item General Health Questionnaire (GHQ-12) by 7.9 points (all p < 0.01). Forced expiratory volume in one second (FEV₁) increased from from 3.6 L to 3.8 L (p = 0.04). Subgroup analysis revealed an enhancement in sleep-related symptoms and pulmonary function.

Conclusions: RMT may serve as a patient-centered alternative for managing the symptomatic burden of mild to moderate OSA. While larger trials are needed to confirm these preliminary findings, these pilot results do not yet demonstrate sustained benefit and should be interpreted with caution. Trial registration ClinicalTrials.gov, register no. NCT05320952.

Keywords: Gender differences; Pulmonary function; Respiratory exercises; Sleep quality.