Structure and severity of pharyngeal obstruction determine oral appliance efficacy in sleep apnoea.

KEY POINTS: •Some patients with obstructive sleep apnoea (OSA) respond well to oral appliance therapy, whereas others do not for reasons that are unclear. •In the present study, we used gold-standard measurements to demonstrate that patients with a posteriorly-located tongue (natural sleep endoscopy) exhibit a preferential improvement in collapsibility (lowered critical closing pressure) with oral appliances. •We also show that patients with both posteriorly-located tongue and less severe collapsibility (predicted responder phenotype) exhibit greater improvements in severity of obstructive sleep apnoea (i.e. reduction in event frequency by 83%, in contrast to 48% in predicted non-responders). •The present study suggests that the structure and severity of pharyngeal obstruction determine the phenotype of sleep apnoea patients who benefit maximally from oral appliance efficacy. ABSTRACT: A major limitation to the administration of oral appliance therapy for obstructive sleep apnoea (OSA) is that therapeutic responses remain unpredictable. In the present study, we tested the hypotheses that oral appliance therapy (i) reduces pharyngeal collapsibility preferentially in patients with posteriorly-located tongue and (ii) is most efficacious (reduction in apnoea-hypopnea index; AHI) in patients with a posteriorly-located tongue and less-severe baseline pharyngeal collapsibility. Twenty-five OSA patients underwent upper airway endoscopy during natural sleep to assess tongue position (type I: vallecula entirely visible; type II: vallecula obscured; type III: vallecula and glottis obscured), as well as obstruction as a result of other pharyngeal structures (e.g. epiglottis). Additional sleep studies with and without oral appliance were performed to measure collapsibility (critical closing pressure; Pcrit) and assess treatment efficacy. Overall, oral appliance therapy reduced Pcrit by 3.9 ± 2.4 cmH2 O (mean ± SD) and AHI by 69 ± 19%. Therapy lowered Pcrit by an additional 2.7 ± 0.9 cmH2 O in patients with posteriorly-located tongue (types II and III) compared to those without (type I) (P < 0.008). Posteriorly-located tongue (p = 0.03) and lower collapsibility (p = 0.04) at baseline were significant determinants of (greater-than-average) treatment efficacy. Predicted responders (type II and III and Pcrit < 1 cmH2 O) exhibited a greater reduction in the AHI (83 ± 9 vs. 48 ± 8% baseline, P < 0.001) and a lower treatment AHI (9 ± 6 vs. 32 ± 15 events h-1 , P < 0.001) than predicted non-responders. The site and severity of pharyngeal collapse combine to determine oral appliance efficacy. Specifically, patients with a posteriorly-located tongue plus less-severe collapsibility are the strongest candidates for oral appliance therapy.

Mouth Closing to Improve the Efficacy of Mandibular Advancement Devices in Sleep Apnea.

Rationale: Mouth breathing increases upper airway collapsibility, leading to decreased efficacy of obstructive sleep apnea (OSA) treatments. We hypothesized that the use of mandibular advancement devices (MAD) increases mouth breathing, and thus, using an adhesive mouthpiece (AMT) to prevent mouth breathing in combination with MAD can improve the treatment efficacy. Objectives: To evaluate the efficacy of MAD + AMT in comparison with MAD alone. Methods: A prospective crossover pilot study was designed to test this hypothesis. Briefly, adult participants with an apnea-hypopnea index (AHI) between 10 and 50 events/h at the screening visit were randomized to no treatment (baseline), MAD treatment, AMT treatment, and MAD + AMT treatment. As a primary analysis, absolute AHI was compared between MAD and MAD + AMT arms. Secondary analyses included quantifying the percent change in AHI, percentage of complete (AHI < 5 events/h) and incomplete (5-10 events/h) responders, and the efficacy of AMT alone in comparison with other treatment arms. Results: A total of 21 participants were included (baseline AHI = 24.3 ± 9.9 events/h). The median AHI (interquartile range) in the MAD and MAD + AMT arms were 10.5 (5.4-19.6) events/h and 5.6 (2.2-11.7) events/h (P = 0.02), respectively. A total of 76% of individuals achieved an AHI of <10 events/h in the MAD + AMT arm versus 43% in the MAD arm (P < 0.01). Finally, the observed effect was similar in moderate to severe OSA (AHI ⩾ 15 events/h) in terms of absolute reduction and treatment responders, and AMT alone did not significantly reduce the AHI compared with baseline. Conclusions: A combination of an adhesive mouthpiece and MAD is a more effective therapy than MAD alone. These findings may help improve clinical decision making in sleep apnea.