Department of Mechanical Engineering, University of California Riverside, 900 University Ave., Riverside, CA, 92506, USA.
Division of Biomedical Sciences, Riverside School of Medicine, University of California, Riverside, CA, USA.
Ann Biomed Eng. 2024 Feb;52(2):342-354. doi: 10.1007/s10439-023-03380-1. Epub 2023 Oct 31.
Increased ventilator use during the COVID-19 pandemic resurrected persistent questions regarding mechanical ventilation including the difference between physiological and artificial breathing induced by ventilators (i.e., positive- versus negative-pressure ventilation, PPV vs NPV). To address this controversy, we compare murine specimens subjected to PPV and NPV in ex vivo quasi-static loading and quantify pulmonary mechanics via measures of quasi-static and dynamic compliances, transpulmonary pressure, and energetics when varying inflation frequency and volume. Each investigated mechanical parameter yields instance(s) of significant variability between ventilation modes. Most notably, inflation compliance, percent relaxation, and peak pressure are found to be consistently dependent on the ventilation mode. Maximum inflation volume and frequency note varied dependencies contingent on the ventilation mode. Contradictory to limited previous clinical investigations of oxygenation and end-inspiratory measures, the mechanics-focused comprehensive findings presented here indicate lung properties are dependent on loading mode, and importantly, these dependencies differ between smaller versus larger mammalian species despite identical custom-designed PPV/NPV ventilator usage. Results indicate that past contradictory findings regarding ventilation mode comparisons in the field may be linked to the chosen animal model. Understanding the differing fundamental mechanics between PPV and NPV may provide insights for improving ventilation strategies and design to prevent associated lung injuries.
在 COVID-19 大流行期间，呼吸机的使用增加，再次引发了关于机械通气的持续问题，包括呼吸机引起的生理呼吸和人工呼吸之间的区别（即正压通气与负压通气，PPV 与 NPV）。为了解决这一争议，我们比较了在体外准静态加载下接受 PPV 和 NPV 的鼠标本，并通过测量准静态和动态顺应性、跨肺压和充气频率和体积变化时的能量来量化肺力学。每个研究的机械参数在通气模式之间都存在显著的可变性。最值得注意的是，充气顺应性、松弛百分比和峰值压力始终取决于通气模式。最大充气量和频率则取决于通气模式的不同而有所不同。与之前对氧合和吸气末措施的有限临床研究相反，这里提出的以力学为重点的综合研究结果表明，肺部特性取决于加载模式，而且重要的是，尽管使用了相同的定制设计的 PPV/NPV 呼吸机，但在较小和较大的哺乳动物之间，这些依赖性是不同的。结果表明，过去在通气模式比较方面的矛盾发现可能与所选的动物模型有关。了解 PPV 和 NPV 之间的不同基本力学特性可能为改进通气策略和设计以防止相关肺损伤提供见解。
