Transmission of oral pressure compromises oronasal CPAP efficacy to treat Obstructive Sleep Apnea.
Oronasal mask is frequently used to treat OSA. In contrast to nasal CPAP, the effectiveness of oronasal CPAP varies for unknown mechanisms. We hypothesized that oral breathing and pressure transmission through the mouth compromises oronasal CPAP efficacy.Thirteen OSA patients, well adapted to oronasal CPAP, were monitored by full polysomnography, pharyngeal pressure catheter and nasoendoscope. Patients slept with low doses of midazolam using an oronasal mask with sealed nasal and oral compartments. CPAP was titrated during oronasal and nasal routes, then reduced to induce stable flow limitation and abruptly switched to the alternate route. In addition, a tape sealing the mouth was used to block pressure transmission to the oral cavity.Best titrated CPAP was significantly higher in oronasal than nasal route (p=0.005) and patients with >25% of oral breathing (n=5) failed to achieve stable breathing during oronasal CPAP. During stable flow limitation, inspiratory peak flow was lower, driving pressure was higher, upper airway inspiratory resistance was higher, retropalatal and retroglossal area were smaller in oronasal than nasal route (p<0.05 for all comparisons). Differences were observed even among patients with no oral flow and were abolished when a tape sealing the mouth was used (n=6).Oral breathing and transmission of positive pressure through the mouth compromises oronasal CPAP. Click here to read full article on original source website