P407 A gender perspective on mandibular advancement device treatment in sleep-related breathing disorders

Abstract

Background:Mandibular advancement (MA) is an alternative to continuous positive airway pressure (CPAP) for the treatment of the obstructive sleep apnea syndrome (OSAS). It improves UA dynamics studied through phrenic stimulation in normals (Verin et al., Sleep Medicine, In press). This study was designed to assess the impact ofMA onUA dynamics in awake OSAS patients. Methods: Measurements were made during exclusive nasal-breathing through an airtight mask in 13 awake OSAS patients (age: 50 ± 12 years; 13 males; AHI: 56 ± 31 n/h; BMI: 27 ± 5 kg/m). Esophageal pressure referenced to mask pressure (Pd) and instantaneous flows (VI) were recorded during diaphragm twitches induced by bilateral anterior phrenic nerve magnetic stimulation (BAMPS), giving access to upper airway resistance (UAR). We have previously demonstrated that twitch-related inspirations are flow-limited in normal individuals and in OSAS patients, flow first rising to a maximum (VImax), then decreasing to a minimum (VImin), and then increasing again (VImin). UAR were calculated at the points of peak pressure (Pd,p), VImax and VImin. BAMPS was first performed without MA, then with a MA of 4, 8, 10 and 12 mm. Results: Twitches always exhibited a flow-limited pattern, whatever the condition tested. VI increased with MA from 8 to 12 mm, Pd was not modified and thus UAR decreased from 8 to 12 mm. The most important change being observed at VImin. The relationship between driving pressure (Pd) and flow (VI) were adequately fitted by a polynomial regression (VI = k1Pd + k2Pd ). This allowed the computation of a predicted closing pressure (k1/k2) in 11 patients, k1/ k2 significantly increased with a 4 mm MA was thereafter not modified. Conclusion: MA improves UA dynamics as studied with phrenic stimulation.