Mask Type Affects Airway Collapsibility in OSA
Use of an oronasal mask for delivery of continuous positive airway pressure (CPAP) was associated with increased upper airway collapsibility and the need for greater therapeutic pressure compared to nasal masks, as indicated by data from 14 individuals with obstructive sleep apnea (OSA).
Previous research has linked oronasal mask use to lower adherence, higher residual apnea hypopnea index (AHI), and increased pressure requirements for OSA patients, but the underlying mechanisms for differences in performance of nasal and oronasal masks are not well understood, write Shane A. Landry, PhD, of Monash University, Melbourne, Australia, and colleagues.
In a study published in the journal Chest, the researchers compared upper airway changes with CPAP therapy during sleep and wake times using oronasal and nasal masks. A total of 15 adults with OSA were included; 14 completed the study. OSA was defined as an AHI of more than 10 events per hour. The patients ranged in age from 18–65 years.
All participants attended an overnight sleep study. They slept with a CPAP device and an oronasal mask for half the night and a nasal mask for the other half. Mask order was randomly determined in a crossover design, and participants were awake for approximately 5–20 minutes after changing masks. Participants underwent MRI of the upper airway when awake. Airway collapsibility was assessed using pharyngeal
critical closing pressure (Pcrit) and therapeutic CPAP values.
Overall, Pcrit values were significantly higher with an oronasal mask compared to a nasal mask (3.1 cmH2O vs 0.7 cmH2O; P < .001). CPAP therapeutic values were significantly higher with oronasal masks than with nasal masks (12.6 vs 10.1; P < .001).
The average difference in Pcrit of approximately 2 cmH2O was consistent across all participants, even the single patient who regularly used an oronasal mask, the researchers note.
“At the group level, no statistically significant differences were observed between the nasal mask therapeutic CPAP level and participants’ prescribed CPAP level,” they add.
In addition, a significant association appeared between the change in Pcrit and the change in therapeutic pressure level (r2 = 0.72; P < .001), but not between Pcrit changes and demographic factors, including age, body mass index, or sex.
The researchers used imaging to examine the effect of pressure and the route of breathing on cross-sectional airway area. In comparing nasal and oronasal masks during periods of nasal breathing, they found that the retroglossal and retropalatal cross-sectional area was smaller with the oronasal mask than with the nasal mask.
“Taken together, these data provide further evidence that a patient’s therapeutic CPAP level may be a reasonable surrogate marker of airway collapsibility and that oronasal masks cause measurable anatomical compromise that may offset some degree of CPAP efficacy,” the researchers write.
The mechanisms by which oronasal masks contribute to increased airway collapsibility may include the tighter straps on the oronasal mask or the route of breathing (nasal vs oral), they write.
The study findings were limited by several factors, including the incomplete quantitative assessment of nasal vs oral breathing in the sleep or MRI studies, the use of only half a night of sleep, and the measurement of airways only while participants were awake, the researchers note.
The results were strengthened by the use of commercial masks and the within-subjects design and demonstrated worsening airway collapsibility when CPAP was delivered by an oronasal mask, “resulting in increased CPAP level required to induce stable non-flow limited breathing,” they conclude.
The study was supported in part by grants to several authors from the Heart Foundation of Australia Future Leader Fellowship and NHMRC Fellowship. Landry has disclosed no relevant financial relationships.
Chest. Published online March 15, 2023. Abstract
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