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Compared with nasal masks, oronasal masks are associated with a more collapsible upper airway, requiring higher therapeutic CPAP levels, according to the study.
With continuous positive airway pressure (CPAP) therapy, oronasal masks are associated with a more collapsible airway than nasal masks in patients with obstructive sleep apnea. According to a recent study, oronasal masks may affect upper airway anatomy and collapsibility, but the underlying mechanisms are poorly understood.1
Previous research has shown patients using oronasal masks have lower treatment adherence, higher residual apnea-hypopnea index (AHI), and increased CPAP therapeutic pressure compared to nasal masks.
In this study, Shane Landry, PhD, Department of Physiology, School of Biomedical Sciences, Faculty of Medicine, Nursing and Health Sciences, Monash University, and a team of investigators aimed to assess how oronasal masks affect upper airway anatomy and collapsibility in OSA patients.
A total of 14 patients with obstructive sleep apnea were included. They participated in a sleep study with both a nasal and oronasal mask, each for half the night. Manual titration was used to determine the therapeutic pressure of CPAP, and upper airway collapsibility was assessed using the pharyngeal critical closing pressure (Pcrit) technique.
The cross-sectional area of the retroglossal and retropalatal airway throughout the respiratory cycle was examined with Cine MRI with each mask interface. As part of the evaluation, scans were repeated at 4 cmH2O and at the nasal and oronasal therapeutic pressures.
Investigators found Pcrit values were significantly higher with oronasal masks compared with nasal masks (3.1; 0.7 cmH2O, respectively). Therapeutic CPAP levels were also higher by a mean of 2.5 cmH2O higher, with oronasal masks averaging 12.6, and nasal masks at 10.1 cmH2O.
While the order of mask-wearing was randomized, investigators noted these differences were highly consistent in the single habitual oronasal mask user. There was no significant difference observed between the nasal mask therapeutic CPAP level and participants’ prescribed CPAP level at the group level.
Additionally, increased CPAP levels generated significant increases in retroglossal and retropalatal airway cross-sectional area. However, after controlling for pressure, there was no significant association in the increase of retroglossal airway size between nasal and oronasal masks.
The analysis showed the nasal mask exhibited a correlation with slightly larger retroglossal airway size than the oronasal mask after controlling for pressure. Changes in the lateral diameter of the airway primarily drove these changes in cross-sectional area, the team noted.
Based on the results, investigators acknowledged the change in therapeutic pressure between masks was strongly correlated with the change in Pcrit, indicating that the increased pressure requirements are related to the increased collapsibility of the upper airway with the oronasal mask.
Furthermore, the increase in CPAP correlated with an increase in both the retroglossal and retro-palatal airway dimensions across both masks. However, after controlling for pressure and breath phase, the retro-palatal cross-sectional area was moderately larger when using a nasal versus an oronasal mask while nasal breathing.
While further research is needed for a better understanding of these mechanisms, these findings suggest that selecting the appropriate mask interface for individual patients may be important for optimizing CPAP therapy and improving treatment adherence and outcomes.