Obstructive sleep apnea (OSA) impairs sleep and respiration, and sub-optimal adherence to its gold-standard CPAP therapy compels development of alternative approaches. This study investigates the effects of steam-assisted respiratory muscle training (RMT) on polysomnographic (PSG) outcomes in patients with OSA.

In a 12-week open-label prospective pilot study, 60 working participants with mild to moderate OSA underwent individualized inspiratory and expiratory resistance training with adjunctive steam inhalation. PSG was conducted pre- and post-intervention. Primary outcomes included changes in respiratory indices (AHI, ODI₃, CT₉₀) and sleep quality metrics (sleep efficiency, WASO). Statistical analyses included the Shapiro-Wilk normality test, Paired T, Welch, or Wilcoxon comparing visits, Wilson CIs reporting responders, Mann-Whitney and Fisher assessing associations, regression predicting change, with significance set at p < 0.05.

Of 60 participants, 33 completed the study. Primary outcomes–respiratory indices and sleep continuity metrics–remained unchanged (all p > 0.05). Secondary analyses showed reduced REM latency, increased REM duration, and fewer periodic limb movements and arousal-related events (all p < 0.05). Regression analysis indicated that greater height and BMI were associated with fewer PLM, whereas larger waist circumference predicted more PLM.

Steam-assisted RMT did not significantly alter respiratory or sleep continuity indices but was associated with modest changes in REM architecture and limb movements. These findings should be interpreted cautiously, as exploratory observations in a non-controlled pilot setting. Larger randomized, sham-controlled trials with objective adherence monitoring are warranted to confirm these preliminary results.