Dynamic tongue base thickness measured by drug-induced sleep ultrasonography in patients with obstructive sleep apnea

The aim of this study was to determine the value of drug-induced sleep ultrasonography (DISU) for evaluating tongue base thickness (TBT) from the awake state to drug-induced sleep, to further understand the impact of dynamic changes in TBT in obstructive sleep apnoea (OSA) patients.

From May 2017 to May 2018, thirty patients with OSA were prospectively recruited. Sleep was induced with propofol via use of a target-controlled infusion (TCI) system. The depth of sedation was monitored by the bispectral (BIS) index with BIS levels ranging from 50 to 70. The dynamic change in the tongue base from the awake state to drug-induced sleep was recorded. The correlation between TBT in the awake state and in drug-induced sleep with OSA severity was analysed.

The mean TBT in drug-induced sleep was significantly greater than that in the awake state (66.2 ± 4.8 mm vs 61.6 ± 4.6 mm, P < 0.001). TBT in drug-induced sleep was more correlated with AHI compared to TBT in the awake state (r = 0.50 vs r = 0.40). This study showed that TBT in drug-induced sleep had the largest AUC (Area Under the Curve) in the ROC (Receiver Operating Characteristics) analysis (0.875), providing a cut-off point of 63.20 mm with 95% sensitivity for diagnosis of moderate versus severe OSA.

Our findings validate the use of DISU in objectively assessing the tongue base collapse in OSA patients. It provides a convenient and non-invasive way to evaluate the upper airway changes in OSA patients in the future.