Ultrasonography of the neck in patients with obstructive sleep apnea

Introduction In resource-limited settings, obstructive sleep apnea (OSA) often goes undiagnosed as polysomnography (PSG) is expensive, time-consuming, and not readily available. Imaging studies of upper airway have been tried as alternatives to PSG to screen for OSA. However, racial differences in upper airway anatomy preclude generalizability of such studies. We sought to test the hypothesis that ultrasonography (USG), an inexpensive, readily available tool to study soft tissue structures of the upper airway, would have predictive value for OSA in South Asian people. Methods Adult patients with sleep-related complaints suspicious for OSA were taken for overnight PSG. After the PSG, consecutive patients with and without OSA were studied with submental ultrasonography to measure tongue base thickness (TBT) and lateral pharyngeal wall thickness (LPWT). Results Among 50 patients with OSA and 25 controls, mean age was 43.9 +/- 11.4 years, and 39 were men. Patients with OSA had higher TBT (6.77 +/- 0.63 cm vs 6.34 +/- 0.54 cm, P value = 0.004) and higher LPWT (2.47 +/- 0.60 cm vs 2.12 +/- 0.26 cm, P value = 0.006) compared to patients without OSA. On multivariate analysis, TBT, LPWT, and neck circumference were identified as independent factors associated with OSA. These variables could identify patients with severe OSA with a sensitivity of 72% and a specificity of 76%. Conclusion Patients with OSA have higher tongue base thickness and lateral pharyngeal wall thickness proportionate to the severity of the disease, independent of BMI and neck circumference. These findings suggest that sub-mental ultrasonography may be useful to identify patients with severe OSA in resource-limited settings.