SURFACTANT EFFECTS ON FLUID-ELASTIC INSTABILITIES OF LIQUID-LINED FLEXIBLE TUBES - A MODEL OF AIRWAY-CLOSURE
SURFACTANT EFFECTS ON FLUID-ELASTIC INSTABILITIES OF LIQUID-LINED FLEXIBLE TUBES - A MODEL OF AIRWAY-CLOSURE
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DOI：
10.1115/1.2895486
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发表时间：
1993-08-01
影响因子：
1.7
通讯作者：
GROTBERG, JB
中科院分区：
文献类型：
--
作者：
HALPERN, D;GROTBERG, JB
提出了一种理论分析，预测了终末和呼吸性细支气管区小气道的关闭。呼吸道被模拟为细小的弹性管，内部涂有一层薄薄的粘性液体衬里。该模型通过耦合毛细-弹性不稳定性导致液桥形成、壁面坍塌或两者兼而有之而产生闭合。利用推广的液膜润滑理论，推导了液膜厚度、壁面位置和表面活性剂浓度的非线性演化方程。通过数值求解控制方程，对均匀状态下气液界面和壁液界面的位置和表面活性剂浓度进行了摄动，并考察了这些摄动的稳定性。解决方案表明，存在一个临界膜厚，这取决于流体、壁面和表面活性剂的性质，在该厚度之上会形成液桥。临界膜厚epsilon(C)随平均表面张力或壁柔度的增加而减小。在生理条件下，表面活性物质使epsilon(C)增加高达60%，这与生理观察一致。随着薄膜厚度和壁弹性的增加，呼吸道关闭的速度更快。富含表面活性剂的界面的关闭时间可能比不含表面活性剂的界面长约五倍。
A theoretical analysis is presented predicting the closure of small airways in the region of the terminal and respiratory bronchioles. The airways are modelled as thin elastic tubes, coated on the inside with a thin viscous liquid lining. This model produces closure by a coupled capillary-elastic instability leading to liquid bridge formation, wall collapse or a combination of both. Nonlinear evolution equations for the film thickness, wall position and surfactant concentration are derived using an extended version of lubrication theory for thin liquid films. The positions of the air-liquid and wall-liquid interfaces and the surfactant concentration are perturbed about uniform states and the stability of these perturbations is examined by solving the governing equations numerically. Solutions show that there is a critical film thickness, dependent on fluid, wall and surfactant properties above which liquid bridges form. The critical film thickness, epsilon(c), decreases with increasing mean surface-tension or wall compliance. Surfactant increases epsilon(c), by as much as 60 percent for physiological conditions, consistent with physiological observations. Airway closure occurs more rapidly with increasing film thickness and wall flexibility. The closure time for a surfactant rich interface can be approximately five times greater than an interface free of surfactant.