Evaluation of Upper Airway in Obstructive Sleep Apnea: Synchronized Imaging and Acoustic Analyses

Abstract

Objectives:

Snore signals are produced by soft tissue vibration in the upper airway (UA). To date, there is no gold standard to localize UA narrowing sites in patients with obstructive sleep apnea syndrome (OSAS). In this study, we use a “vocal tract model” to investigate the association between snore acoustic characteristics and UA collapse. Dynamic magnetic resonance imaging (dMRI) was used to provide UA anatomy information.

Methods:

We report data from 44 polysomnography (PSG)-confirmed snoring episodes. Dynamics of UA and acoustic manifestations of snore events during natural sleep were recorded with synchronized dMRI and fiber-optic microphone recording. After the deletion of background dMRI noises, the spectrum envelope was reconstructed by applying a vocal tract model to characterize the snoring patterns. The temporal change of spectrum envelope was analyzed using Gabor transformation to correlate with UA dynamics.

Results:

The snore events were categorized into 28 none, 7 typical (velopharyngeal), and 9 mixed (velopharyngeal and hypopharyngeal) obstructions. The snore’s dominant frequency of envelop spectrum can differentiate none from typical UA obstructions (82.3±16.4Hz vs 101.9±9.1 Hz, p<0.01); and can differentiate mixed from typical obstructions (131.9±19.8 Hz vs.101.9±9.1 Hz, p < 0.05)

Conclusions:

The dynamics of acoustic patterns derived from the envelope of Gabor spectrogram are unique and characteristics in different types of obstruction with the advantage of low-cost and easy availability. Therefore, the dynamics of acoustic patterns warrants further investigation to identify the structural changes of the obstruction sites in OSAS patients.