Short-term changes in respiratory muscle strength before and after sleep in patients with obstructive sleep apnea.

OBJECTIVE

Obstructive sleep apnea (OSA) is characterized by recurrent upper airway obstruction during sleep, leading to intermittent hypoxemia and increased respiratory effort. This study investigated whether evening-to-morning changes in respiratory muscle strength reflect short-term physiological responses to overnight apnea-hypopnea-related loading.

METHODS

Eighty patients undergoing overnight polysomnography for suspected OSA between February and June 2025 were prospectively evaluated. Maximal inspiratory (MIP) and expiratory (MEP) pressures were measured in the evening before and in the morning after PSG, and changes were calculated as morning minus evening values (ΔMIP and ΔMEP).

RESULTS

Positive ΔMIP and ΔMEP values were significantly higher in patients with OSA compared to the control group (p < 0.001 for both). During sleep, both minimum and maximum oxygen saturation values were significantly lower in the OSA group than in controls (p < 0.001, 0.009). In multivariate regression analysis, ΔMIP was positively associated with BMI (β = 0.609, p < 0.001), REM-AHI (β = 0.693, p < 0.001), and supine AHI (β = 1.597, p < 0.001), and negatively associated with ODI (β = -1.000, p < 0.001). Similarly, ΔMEP was positively associated with BMI (β = 0.370, p = 0.001), REM-AHI (β = 0.506, p = 0.002), and supine AHI (β = 1.706, p < 0.001), while negatively associated with ODI (β = -1.128, p < 0.001).

CONCLUSION

Evening-to-morning changes in respiratory muscle strength reflect acute overnight respiratory muscle loading in patients with OSA and provide physiological insight into short-term neuromuscular adaptations associated with recurrent apnea-hypopnea events.