以超音波舌肌功能影像來評估睡眠呼吸中止症

Abstract

根據美國學者統計五成的成年人患有睡眠呼吸症困擾。本研究探討的阻塞型睡眠呼吸中止症(Obstructive sleep apnea, OSA)主要因為年紀大或肥胖使口腔周圍肌肉張力下降壓迫到呼吸道而導致身體缺氧，發展成心血管疾病和腦神經系疾病等之症。文獻指出觀察呼吸道與口腔肌肉動態影像變化能有效篩選OSA，呼吸道與OSA發病特徵的關聯性較高，因此精準度較好，但影像上的限制難以適用於每位受測者，相反的，口腔肌肉則容易尋找軟組織特徵、動態分析過程誤差較小且較適用於每位受測者。臨床診斷為多導睡眠圖中的呼吸中止指數，需在睡眠中心睡上一晚，過程中容易因環境影響導致診斷誤差。因此希望能透過操作簡單且無游離輻射的即時超音波影像系統並搭配舌頭功能性運動量測的結果來判斷需要治療的重度患者，並利用肌肉應變來進行本研究的實驗。在文獻顯示正常呼吸與口鼻不進氣為有效判斷OSA的方法，而本研究則同時利用舌壓測定器(Maximum tongue pressure measurement, TP)量測頦舌肌的肌肉張力下降，並觀察OSA組內是否在應變情況下有明顯差別。研究中將透過量測舌肌參數：最大舌根厚(Maximum tongue base apex, TBA)、舌動脈距離和最大舌厚，並利用斑點追蹤量測舌肌特定區域的位移大小與方向，且同時記錄連續的舌肌變化影像與應變趨勢圖。本研究收案為12位健康、30位輕度、30位中度、30位重度OSA患者，其中10位健康的MRI影像將用來與超音波影像之軟組織位置進行比對。結果顯示利用TP量測TBA和參考線之應變距離比能有效預測重度與非重度OSA，結果中曲線下面積0.81、敏感性73%、特異性78%，這說明TP下的肌肉應變量測有潛力可作為睡眠呼吸中止症的有效檢查方式。

Statistics show that a significant percentage of adults suffer from sleep apnea, and it is one of the major causes of cardiovascular and neural diseases. Our research focuses on obstructive sleep apnea (OSA), with which the primary cause is regarding the low tension around oral muscle related to age and obesity. The low tension results in upper airway obstruction by gravity during sleep. As the tongue is one of the major muscles around the airway, tongue hypertrophy reduces or blocks the retroglossal space as it does not adequately support surrounding tissues. Previous works show that dynamic changes of airspace and tongue motion are correlated with OSA severity. Upper airway anatomy is important and has strong connection with OSA pathogenesis. However, images of retropharyngeal space are difficult to acquire and determination of the landmarks is challenging. In contract, tongue motion measurements are relatively more robust in the capturing process and suitable for most patients when awake. Currently, the clinical diagnosis of OSA is performed by using apnea-hypopnea index (AHI) and polysomnography (PSG) that are collected at the sleep center overnight. The procedure is time-consuming and easily affected during monitoring. On the other hand, ultrasound examinations may be preferred because the procedure is simple, time-efficient, and non-invasive. It is the goal of this research to correlate the tongue muscle stiffness characteristics with the degree of OSA as defined by AHI. Specifically, maneuver and tongue pressure measurements (TP) are adopted to quantify the functions of the genioglossus muscle. In addition, other ultrasound parameters such as maximum tongue base apex (TBA), the distance between lingual arteries (DLA), and tongue apex (TA) are also used to measure muscle deformation and strain curves by the speckle tracking method. In this study, 12 healthy volunteers, 60 patients with mild-moderate OSA, and 30 severe OSA patients were recruited. PSG was performed at the sleep center of National Taiwan University Hospital, along with the ultrasound examinations and MRI for the healthy volunteers. The TBA and TP results show that the proposed method is able to separate severe and non-severe OSA patients. In addition, the area under the receiver operating characteristic curve is 0.81, and sensitivity is 73%, specificity is 78 percent. Thus, the clinical potential of the proposed method for OSA diagnosis is demonstrated.