Department of Biomedical Engineering, Boston University, Boston, Massachusetts.
OscillaVent, Iowa City, Iowa.
Respir Care. 2020 Jul;65(7):932-945. doi: 10.4187/respcare.07919. Epub 2020 May 6.
The use of shared ventilation, or the simultaneous support of multiple patients connected in parallel to a single mechanical ventilator, is receiving considerable interest for addressing the severe shortage of mechanical ventilators available during the novel coronavirus pandemic (COVID-19). In this paper we highlight the potentially disastrous consequences of naïve shared ventilation, in which patients are simply connected in parallel to a ventilator without any regard to their individual ventilatory requirements. We then examine possible approaches for individualization of mechanical ventilation, using modifications to the breathing circuit that may enable tuning of individual tidal volumes and driving pressures during either volume-controlled ventilation (VCV) or pressure-controlled ventilation (PCV).
Breathing circuit modifications included a PEEP valve on each expiratory limb for both VCV and PCV, an adjustable constriction and one-way valve on the inspiratory limb for VCV, and a pressure-relief valve for peak inspiratory pressure reduction on the inspiratory limb for PCV. The ability to regulate individual tidal volumes using these breathing circuit modifications was tested both theoretically in computer simulations as well as experimentally in mechanical test lungs.
In both the simulations and experimental measurements, naïve shared ventilation resulted in large imbalances across individual tidal volume delivery, dependent on imbalances across patient mechanical properties. The proposed breathing circuit modifications for shared VCV and shared PCV enabled optimization of tidal volume distributions. Individual tidal volume for one patient during shared VCV was sensitive to changes in the mechanical properties of other patients. By contrast, shared PCV enabled independent control of individual patient-received ventilation.
Of the shared ventilation strategies considered, shared PCV, with the inclusion of in-line pressure-relief valves in the individual inspiratory and expiratory limbs, offers the greatest degree of safety and lowest risk of catastrophic mechanical interactions between multiple patients connected to a single ventilator.
在新型冠状病毒肺炎（COVID-19）大流行期间，由于机械通气机严重短缺，同时为多位患者提供通气支持的共享通气策略受到了广泛关注。在本文中，我们强调了盲目使用共享通气策略的潜在灾难性后果，即在未考虑患者个体通气需求的情况下，简单地将患者并联至呼吸机上。然后，我们探讨了通过对呼吸回路进行修改来实现机械通气个体化的方法，这些修改可能使在容量控制通气（VCV）或压力控制通气（PCV）模式下，对个体潮气量和驱动压力进行调整成为可能。
呼吸回路的修改包括在每个呼气支路上都安装呼气末正压（PEEP）阀，用于 VCV 和 PCV；在吸气支路上安装一个可调节的狭窄段和一个单向阀，用于 VCV；在 PCV 的吸气支路上安装一个压力释放阀，用于降低吸气峰压。通过这些呼吸回路的修改来调节个体潮气量的能力，我们分别通过计算机模拟和机械通气测试肺进行了理论和实验测试。
在模拟和实验测量中，盲目共享通气导致了个体潮气量输送的严重失衡，这取决于患者机械特性的不平衡。所提出的用于共享 VCV 和共享 PCV 的呼吸回路修改使潮气量分布得到了优化。在共享 VCV 期间，一位患者的个体潮气量对其他患者机械特性变化敏感。相比之下，共享 PCV 使对每位患者接受的通气进行独立控制成为可能。
在所考虑的共享通气策略中，带有在个体吸气和呼气支路上的内置压力释放阀的共享 PCV 提供了最大程度的安全性和多个患者连接到单个呼吸机时发生灾难性机械相互作用的最低风险。
