Effects of different masks on diaphragm motion in OSAS patients undergoing CPAP: results from an ultrasound-based proof of concept study.

Purpose: Obstructive sleep apnea (OSA) is characterized by recurrent upper airway narrowing or collapse during sleep. Continuous positive airway pressure (CPAP) remains the preferred treatment in selected patients and masks' choice plays an important role for subsequent respiratory events' reduction. It is known that oronasal masks are not as effective at opening the upper airway compared to nasal ones. Thus, the objective of this study was to investigate differences in US-assessed diaphragmatic excursion (DE) using oronasal vs. nasal CPAP masks.

Methods: This observational study included 50 OSA patients presenting a moderate to severe apnea-hypopnea index and requiring CPAP treatment. All participants received US evaluations on diaphragm motion during their oronasal and nasal CPAP trial at equal positive end-expiratory pressure level.

Results: The difference of DE switching mask during CPAP was assessed by using the non-parametric Wilcoxon signed-rank test. A statistically significant increase in US- assessed DE was found when shifting from oronasal to nasal mask (p-value < 0.01). Linear regression models revealed that increased neck circumference and more severe AHI were associated with decreased DE when shifting to an oronasal mask.

Conclusion: This study evaluated the acute impact on US-assessed DE after changing CPAP route from oronasal to nasal mask. Our results suggest that the nasal type should be the more suitable option for most patients with OSA, especially those with higher nasal circumference. Diaphragmatic motion throughout US may become a practical tool to help in the choice of the fittest mask in patients undergoing CPAP.