Fig3B_standardSplitter_PressureVolumeFlow_PatientModelsAtoD_LungModelB: Variables for a patient with a lung model B (mild ARDS, 20% reduction with respect to A) from A simulated single ventilator/dual patient ventilation strategy for acute respiratory distress syndrome during the COVID-19 pandemic

The potential for acute shortages of ventilators at the peak of the COVID-19 pandemic has raised the possibility of needing to support two patients from a single ventilator. To provide a system for understanding and prototyping designs, we have developed a mathematical model of two patients supported by a mechanical ventilator. We propose a standard set-up where we simulate the introduction of T-splitters to supply air to two patients and a modified set-up where we introduce a variable resistance in each inhalation pathway and one-way valves in each exhalation pathway. Using the standard set-up, we demonstrate that ventilating two patients with mismatched lung compliances from a single ventilator will lead to clinically significant reductions in tidal volume in the patient with the lowest respiratory compliance. Using the modified set-up, we demonstrate that it could be possible to achieve the same tidal volumes in two patients with mismatched lung compliances, and we show that the tidal volume of one patient can be manipulated independently of the other. The results indicate that, with appropriate modifications, two patients could be supported from a single ventilator with independent control of tidal volumes.

新冠疫情（COVID-19 pandemic）大流行峰值阶段，呼吸机急性短缺的风险催生了单台机械呼吸机（mechanical ventilator）同时支持两名患者的救治思路。为搭建可用于理解相关设计并开展原型验证的研究系统，我们开发了单台机械呼吸机支持两名患者的数学模型。我们提出两类配置方案：标准配置方案中，通过引入T型分流器（T-splitters）为两名患者供气；改进配置方案中，在每条吸入通路增设可变电阻（variable resistance），并在每条呼出通路加装单向阀（one-way valves）。借助标准配置方案的实验验证，我们证实：若单台呼吸机为两名肺顺应性（lung compliance）不匹配的患者通气，肺顺应性更低的患者的潮气量（tidal volume）会出现具有临床意义的降幅。借助改进配置方案的实验验证，我们证实：可为两名肺顺应性不匹配的患者设置一致的潮气量，且可独立调节其中一名患者的潮气量而不影响另一患者。研究结果表明，经过合理改装后，单台呼吸机可同时支持两名患者，且可独立控制二者的潮气量。