Respiratory Effort-Driven Mandibular Opening as a Mechanism of Air Leak During CPAP Therapy.

RATIONALE: Unintentional air leaks are common during continuous positive airway pressure (CPAP) therapy and represent a leading cause of treatment failure. OBJECTIVE: To investigate the temporal association between respiratory effort (RE)-driven mouth opening and the occurrence of mouth leaks in patients with obstructive sleep apnea (OSA) during CPAP therapy. METHODS: Polysomnography with simultaneous mandibular jaw movements (MJM) and leak-flow monitoring was conducted in 200 OSA patients during CPAP therapy. The main analysis included 1,494 data fragments (mean duration: 9.34 ± 6.33 min) classified as leak-free controls, sequential intermittent leaks (Group A), and isolated sustained leaks (Group B). Multistep analyses included regression modeling and bidirectional Granger-causality testing. MEASUREMENTS AND MAIN RESULTS: Compared with leak-free control fragments, leak periods were significantly associated with higher levels of RE and mouth opening amplitudes. Regression analyses showed that mouth leaks were associated with increased sleep fragmentation, significant reduction in N3 sleep stage proportion (-5.34%) and more residual obstructive events during CPAP. Each 1-standard deviation increase in the number of leak episodes was associated with a 38% increase in arousal index and a 34% increase in residual obstructive apnea/hypopnea event rate. Bidirectional Granger-causality tests indicated that mouth opening was preceded by increased RE and subsequently induced leaks in most cases (Group A, 93.6%; Group B, 91.5%). CONCLUSION: Mouth opening driven by persistent RE is a measurable mechanism contributing to the overall burden of mouth leaks during CPAP therapy in OSA. Integrating MJM recordings with leak monitoring may help identify leak origin, guide targeted interventions, and ultimately improve CPAP effectiveness and adherence.