Department of Surgery, University of Cincinnati, Cincinnati, OH, USA.
Respir Care. 2012 Mar;57(3):399-403. doi: 10.4187/respcare.01236. Epub 2011 Oct 12.
A mass-casualty respiratory failure event where patients exceed available ventilators has spurred several proposed solutions. One proposal is use of a single ventilator to support 4 patients.
A ventilator was modified to allow attachment of 4 circuits. Each circuit was connected to one chamber of 2 dual-chambered, test lungs. The ventilator was set at a tidal volume (V(T)) of 2.0 L, respiratory frequency of 10 breaths/min, and PEEP of 5 cm H(2)O. Tests were repeated with pressure targeted breaths at 15 cm H(2)O. Airway pressure, volume, and flow were measured at each chamber. The test lungs were set to simulate 4 patients using combinations of resistance (R) and compliance (C). These included equivalent C and R, constant R and variable C, constant C and variable R, and variable C and variable R.
When R and C were equivalent the V(T) distributed to each chamber of the test lung was similar during both volume (range 428-442 mL) and pressure (range 528-544 mL) breaths. Changing C while R was constant resulted in large variations in delivered V(T) (volume range 257-621 mL, pressure range 320-762 mL). Changing R while C was constant resulted in a smaller variation in V(T) (volume range 418-460 mL, pressure range 502-554 mL) compared to only C changes. When R and C were both varied, the range of delivered V(T) in both volume (336-517 mL) and pressure (417-676 mL) breaths was greater, compared to only R changes.
Using a single ventilator to support 4 patients is an attractive concept; however, the V(T) cannot be controlled for each subject and V(T) disparity is proportional to the variability in compliance. Along with other practical limitations, these findings cannot support the use of this concept for mass-casualty respiratory failure.
大量需要呼吸支持的患者同时出现，而可供使用的呼吸机数量有限，这一事件引发了多种解决方案的提出。其中一个提议是使用一台呼吸机为 4 名患者提供支持。
对呼吸机进行了改造，使其可以连接 4 个回路。每个回路连接到两个双腔测试肺的一个腔室。呼吸机设置潮气量（V(T)）为 2.0 L，呼吸频率为 10 次/分钟，呼气末正压（PEEP）为 5 cm H(2)O。在压力目标为 15 cm H(2)O 的情况下重复了测试。在每个腔室测量气道压力、容量和流量。测试肺使用阻力（R）和顺应性（C）的组合模拟 4 名患者。这些组合包括等效 C 和 R、恒定 R 和可变 C、恒定 C 和可变 R 以及可变 C 和可变 R。
当 R 和 C 相同时，在容积（范围 428-442 mL）和压力（范围 528-544 mL）呼吸时，每个测试肺腔室的 V(T)分布相似。当 R 保持不变而 C 发生变化时，输送的 V(T) 会发生很大变化（容积范围 257-621 mL，压力范围 320-762 mL）。当 C 保持不变而 R 发生变化时，V(T) 的变化较小（容积范围 418-460 mL，压力范围 502-554 mL），与仅 C 变化相比。当 R 和 C 都发生变化时，在容积（336-517 mL）和压力（417-676 mL）呼吸时，输送的 V(T) 范围更大，与仅 R 变化相比。
使用一台呼吸机为 4 名患者提供支持是一个很有吸引力的概念；然而，无法为每个患者控制 V(T)，并且 V(T) 的差异与顺应性的变化成正比。除了其他实际限制外，这些发现不支持将该概念用于大量呼吸衰竭患者的支持。
