Department of Mechanical Engineering, The Cooper Union for the Advancement of Science and Art, New York, NY, USA.
J Appl Physiol (1985). 2011 Dec;111(6):1819-27. doi: 10.1152/japplphysiol.01230.2010. Epub 2011 Aug 18.
Computational fluid dynamics (CFD) analysis was used to model the effect of collapsing airway geometry on internal pressure and velocity in the pharyngeal airway of three sedated children with obstructive sleep apnea syndrome (OSAS) and three control subjects. Model geometry was reconstructed from volume-gated magnetic resonance images during normal tidal breathing at 10 increments of tidal volume through the respiratory cycle. Each geometry was meshed with an unstructured grid and solved using a low-Reynolds number k-ω turbulence model driven by flow data averaged over 12 consecutive breathing cycles. Combining gated imaging with CFD modeling created a dynamic three-dimensional view of airway anatomy and mechanics, including the evolution of airway collapse and flow resistance and estimates of the local effective compliance. The upper airways of subjects with OSAS were generally much more compliant during tidal breathing. Compliance curves (pressure vs. cross-section area), derived for different locations along the airway, quantified local differences along the pharynx and between OSAS subjects. In one subject, the distal oropharynx was more compliant than the nasopharynx (1.028 vs. 0.450 mm(2)/Pa) and had a lower theoretical limiting flow rate, confirming the distal oropharynx as the flow-limiting segment of the airway in this subject. Another subject had a more compliant nasopharynx (0.053 mm(2)/Pa) during inspiration and apparent stiffening of the distal oropharynx (C = 0.0058 mm(2)/Pa), and the theoretical limiting flow rate indicated the nasopharynx as the flow-limiting segment. This new method may help to differentiate anatomical and functional factors in airway collapse.
计算流体动力学 (CFD) 分析用于模拟气道几何形状塌陷对阻塞性睡眠呼吸暂停综合征 (OSAS) 患儿和三名对照受试者咽气道内压力和速度的影响。模型几何形状是通过容积门控磁共振成像在呼吸周期内通过 10 个潮气量增量重建的。每个几何形状都使用非结构化网格进行网格划分，并使用低雷诺数 k-ω 湍流模型求解，该模型由 12 个连续呼吸周期的平均流量数据驱动。门控成像与 CFD 建模相结合，创建了气道解剖结构和力学的动态三维视图，包括气道塌陷和流动阻力的演变以及局部有效顺应性的估计。在 OSAS 患者中，上气道在潮气量呼吸时通常更具顺应性。沿气道不同位置得出的顺应性曲线（压力与截面积）量化了咽部分段和 OSAS 患者之间的局部差异。在一名患者中，远鼻咽部比鼻咽部更具顺应性（1.028 比 0.450 mm(2)/Pa），且理论极限流量较低，证实该患者远鼻咽部为气道的限流段。另一名患者在吸气时有更顺应性的鼻咽部（0.053 mm(2)/Pa），远鼻咽部（C = 0.0058 mm(2)/Pa）明显变硬，理论极限流量表明鼻咽部为限流段。这种新方法可能有助于区分气道塌陷的解剖学和功能因素。
