阻塞性睡眠呼吸中止症(OSAS)是一種在幼童期常見的呼吸道疾病，起因於睡眠狀態時的呼吸道狹窄甚至是阻塞。腺樣體扁桃腺切除術被視為一種有效治療兒童睡眠呼吸中止症的手術治療方法。計算流體力學(CFD)已經被廣泛使用於分析上呼吸道的流場特性。本研究分析每位兒童患者手術前及手術後，上呼吸道的流場型態。以往利用電腦斷層掃瞄(CT)重建呼吸道的三維模型，為了建立非結構性網格，必須經過平滑化等步驟，但會造成呼吸道的外型失真。本研究利用VOS函數，直接從電腦斷層掃瞄圖判斷計算域的固體區及流體區，建立上呼吸道模型，並可以直接應用於直接施力沉浸邊界法(DFIB)數值模擬。由於上呼吸道流場的紊流特性，在此研究中使用紊流模型—大渦模擬法來求解流場中的紊流。此研究中，CFD參數包括窄縮率、最小截面積、呼吸道阻力以及噴流角被用來評估兒童睡眠呼吸中止症的嚴重程度以及手術的結果。此外，手術前以及手術後呼吸道體積的變化常被視為上呼吸道手術的成功與否。然而，由於上呼吸道的幾何外型會產生迴流泡，縮小呼吸時呼吸道的有效體積。因此，本研究會利用上呼吸道的有效體積，以及其他流體力學指標評估腺樣體扁桃腺切除術的結果。

Obstructive sleep apnea syndrome (OSAS) is a common disorder among children, caused by narrowing or collapsed of the upper airway during sleeping. Surgical therapy, adenotonsillectomy, is considered a first choice and recommended as the initial treatment for child patients with OSAS. Before and after adenotonsillectomy surgery of the upper airway of each child patient are investigated in this study. The conventional procedure of reconstructing the upper airway from the Computerized Tomography (CT) scans causes geometry distortion during the process of smoothing. Instead, the volume of solid (VOS) function is used to define the geometry directly from the gray scale value in CT images of the upper airway and three-dimensional models are created in this study. With the implementation of the direct-forcing immersed boundary (DFIB) method, 3D reconstructed models can be straightly applied to the numerical simulations. Due to the turbulence properties in the respiratory tracts, the turbulence model - Large Eddy Simulations (LES) is also employed. Parameters calculated from CFD results are used to evaluate the severity of the children OSAS and are compared with the diagnosis through the polysomnography. Surgery outcomes can also be assessed with CFD endpoints, including stenosis percentage of the upper airway, airway resistance, and jet angle. Furthermore, variation of the airway volume before and after upper airway surgery is usually used to evaluate the success of the surgery. However, te shape of the upper airway results in separation bubbles which reduces the effective volume of the airway for respiratory. As a result, the effective volume of the upper airway as well as other CFD endpoints are utilized to evaluate the anatomical consequences of adenotonsillectomy surgery in this study.

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