Effect of a non-adjustable oral appliance on upper airway morphology in obstructive sleep apnoea

To evaluate the effect of oral appliance (OA) on upper airway morphology and its relationship with treatment response in subjects with obstructive sleep apnoea (OSA).

Symptomatic OSA subjects were recruited. Non-adjustable OA was custom made. Variables examined at baseline and while wearing the device at 2 months included polysomnographic data, computed tomographic measurements of upper airway cross sectional area at level of velopharynx (VA) and hypopharynx (HA), upper airway volume, and cephalometric parameters. Treatment outcome was based on post-treatment apnoea-hypopnoea index (AHI).

Forty patients were recruited and 23 (7 women) completed the study. They were middle-aged (49, 40-58 years) (median, interquartile range) and overweight (BMI 26, 23.3-29.5 kg/m2), with moderate OSA (AHI 26.4, 14.1-36). The overall post treatment AHI was 8.4 (2.4-12.5), with 14 (61%) patients showing good response (AHI<10), and the other 9 patients showing moderate response (>50% reduction in AHI but still 10). OA decreased the cross-sectional area of the HA (P=0.046), showed a trend of decreasing the ratio of cross-sectional area of the HA to cross-sectional area of the VA (P=0.053) and significantly increased the overall upper airway volume (P=0.006, n=11). No significant relationship between upper airway parameters and treatment outcome was identified.

OA altered upper airway morphometry towards a profile consistent with decreased propensity to collapse, which may thus have contributed to improvement of OSA.