We present a novel computational model for the dynamics of alveolar recruitment/derecruitment (RD), which reproduces the underlying characteristics typically observed in injured lungs. The basic idea is a pressure- and time-dependent variation of the stress-free reference volume in reduced dimensional viscoelastic elements representing the acinar tissue. We choose a variable reference volume triggered by critical opening and closing pressures in a time-dependent manner from a straightforward mechanical point of view. In the case of (partially and progressively) collapsing alveolar structures, the volume available for expansion during breathing reduces and vice versa, eventually enabling consideration of alveolar collapse and reopening in our model. We further introduce a method for patient-specific determination of the underlying critical parameters of the new alveolar RD dynamics when integrated into the tissue elements, referred to as terminal units, of a spatially resolved physics-based lung model that simulates the human respiratory system in an anatomically correct manner. Relevant patient-specific parameters of the terminal units are herein determined based on medical image data and the macromechanical behavior of the lung during artificial ventilation. We test the whole modeling approach for a real-life scenario by applying it to the clinical data of a mechanically ventilated patient. The generated lung model is capable of reproducing clinical measurements such as tidal volume and pleural pressure during various ventilation maneuvers. We conclude that this new model is an important step toward personalized treatment of ARDS patients by considering potentially harmful mechanisms - such as cyclic RD and overdistension - and might help in the development of relevant protective ventilation strategies to reduce ventilator-induced lung injury (VILI).

翻译：我们提出了一种用于肺泡复张/去复张（RD）动力学的新型计算模型，该模型能够复现损伤肺中通常观察到的典型特征。其基本思想是：在代表腺泡组织的降维粘弹性单元中，引入一种依赖于压力与时间的无应力参考体积变化。从直观的力学角度出发，我们选择由临界开放压和闭合压在时间上触发的可变参考体积。当肺泡结构发生（部分且渐进性）塌陷时，可呼吸扩张的有效体积减小，反之亦然，从而使得我们的模型能够考虑肺泡塌陷与再开放过程。我们进一步提出了一种方法，用于在将新的肺泡RD动力学整合到组织单元（称为终端单元）中时，患者特异性地确定其关键参数。该组织单元属于一个基于物理方法、以解剖学正确方式模拟人体呼吸系统的空间解析型肺模型。其中，终端单元的相关患者特异性参数基于医学影像数据和人工通气期间肺的宏观力学行为确定。我们将整个建模方法应用于一例机械通气患者的临床数据，以检验其在真实场景中的表现。生成的肺模型能够复现多种通气操作下的潮气量和胸膜压等临床测量值。我们得出结论：该新模型通过考虑潜在有害机制（如周期性RD和过度膨胀），是迈向ARDS患者个性化治疗的重要一步，并可能有助于制定相关的保护性通气策略，以减少呼吸机相关性肺损伤（VILI）。