P070 Oronasal masks are associated with increased airway collapsibility and increased therapeutic CPAP requirements

Introduction Continuous positive airway pressure (CPAP) delivered via oronasal masks are associated with lower adherence, higher residual AHI and CPAP requirement in comparison to nasal masks. Mechanisms contributing to increased CPAP requirement are not well understood. This physiological study aimed to assess the effect of mask type on upper airway anatomy and collapsibility. Methods 13 OSA patients, underwent a sleep study during which they wore both nasal and oronasal mask for half the night each (order randomized). CPAP was manually titrated to determine therapeutic pressure. Passive upper airway collapsibility was assessed using the Pcrit technique. Participants then underwent an MRI wearing both the nasal and oronasal mask. Cine MRI was used to dynamically assess cross-sectional area of the retroglossal airway across the respiratory cycle with each mask interface. Scans were repeated at 4cmH2O, as well as at the nasal and oronasal therapeutic pressures. Results The oronasal mask was associated with both higher therapeutic pressure requirements (∆M±SEM; +2.6±0.5, p Conclusions These preliminary findings suggest that oronasal masks worsen the collapsibility of the airway which likely contributes to the need for an elevated therapeutic pressure relative to nasal masks.