Prediction of oral appliance efficiency in patients with apnoea using phrenic nerve stimulation while awake.

BACKGROUND In patients with sleep apnoea, primary oropharyngeal collapse of the upper airway during sleep is an important predictor of treatment success with an oral appliance. Phrenic nerve stimulation is able to induce upper airway obstruction and was therefore used to mimic the target for an efficient treatment with an oral appliance. OBJECTIVE To test if the site(s) of upper airway collapse identified by means of bilateral anterior magnetic stimulation during wakefulness could predict the efficacy of treatment with an oral appliance in patients with obstructive sleep apnoea. METHODS The site(s) of upper airway collapse while awake were identified by examining the flow-pressure relationship of flow-limited twitches when measuring velopharyngeal and oropharyngeal pressure. Once the mandibular advancement titration had been completed, the efficacy of mandibular advancement was documented during an in-lab sleep study. RESULTS 33 patients (24 men and 9 women, apnoea-hypopnoea index (AHI) 32.5 ± 17.1/h) participated in the study. Flow limitation was obtained in 29, but 3 of these had no follow-up sleep study with the device. Subjects with oropharyngeal and velopharyngeal collapse did not differ in the phenotypic characteristics associated with a positive response to an oral appliance (gender, apnoea severity, body mass index or positional dependency of breathing disturbances). Complete or partial success was seen in 14/17 subjects with twitch-induced oropharyngeal collapse and in 4/12 patients with velopharyngeal closure. Treatment response was significantly different in subjects with twitch-induced oropharyngeal and velopharyngeal collapse (OR 9.5, 95% CI 1.6 to 52.7). CONCLUSIONS Identifying the site of upper airway collapse by using bilateral anterior magnetic stimulation of the phrenic nerve during wakefulness can predict treatment success with an oral appliance in patients with sleep apnoea.