Department of Mechanical Engineering, Yonsei University, Seoul, Korea.
Department of Oral and Maxillofacial Surgery, Oral Science Research Institute, Yonsei University College of Dentistry, Seoul, Korea.
J Appl Physiol (1985). 2019 Feb 1;126(2):330-340. doi: 10.1152/japplphysiol.00522.2018. Epub 2018 Nov 9.
The present study aimed to detail the relationship between the flow and structure characteristics of the upper airways and airway collapsibility in obstructive sleep apnea. Using a computational approach, we performed simulations of the flow and structure of the upper airways in two patients having different facial morphologies: retruding and protruding jaws, respectively. First, transient flow simulation was performed using a prescribed volume flow rate to observe flow characteristics within upper airways with an unsteady effect. In the retruding jaw, the maximum magnitude of velocity and pressure drop with velocity shear and vortical motion was observed at the oropharyngeal level. In contrast, in the protruding jaw, the overall magnitude of velocity and pressure was relatively small. To identify the cause of the pressure drop in the retruding jaw, pressure gradient components induced by flow were examined. Of note, vortical motion was highly associated with pressure drop. Structure simulation was performed to observe the deformation and collapsibility of soft tissue around the upper airways using the surface pressure obtained from the flow simulation. At peak flow rate, the soft tissue of the retruding jaw was highly expanded, and a collapse was observed at the oropharyngeal and epiglottis levels. NEW & NOTEWORTHY Aerodynamic characteristics have been reported to correlate with airway occlusion. However, a detailed mechanism of the phenomenon within the upper airways and its impact on airway collapsibility remain poorly understood. This study provides in silico results for aerodynamic characteristics, such as vortical structure, pressure drop, and exact location of the obstruction using a computational approach. Large deformation of soft tissue was observed in the retruding jaw, suggesting that it is responsible for obstructive sleep apnea.
本研究旨在详细描述上气道的流动和结构特征与阻塞性睡眠呼吸暂停中气道塌陷之间的关系。我们使用计算方法，对具有不同面型的两位患者（分别为前突型和后缩型下颌）的上气道流动和结构进行了模拟。首先，通过施加规定的体积流量进行瞬态流动模拟，以观察具有非定常效应的上气道内的流动特征。在前突型下颌中，在口咽水平处观察到速度和压降的最大幅度以及速度剪切和涡旋运动。相比之下，在突出型下颌中，速度和压力的整体幅度相对较小。为了确定前突型下颌中压降的原因，检查了流动引起的压力梯度分量。值得注意的是，涡旋运动与压降高度相关。为了观察上气道周围软组织的变形和塌陷，进行了结构模拟，使用从流动模拟中获得的表面压力。在峰值流速时，前突型下颌的软组织高度扩张，在口咽和会厌水平观察到塌陷。
本研究使用计算方法对上气道的气动特性，如涡旋结构、压降和阻塞的确切位置进行了研究，为气动特性提供了数值模拟结果。在前突型下颌中观察到软组织的大变形，表明其是导致阻塞性睡眠呼吸暂停的原因。
