Airway pressure release ventilation (APRV) has been shown to be protective against atelectrauma if expirations are brief. We hypothesize that this is protective because epithelial surfaces are not given enough time to come together and adhere during expiration, thereby avoiding their highly damaging forced separation during inspiration. We investigated this hypothesis in a porcine model of ARDS induced by Tween lavage. Animals were ventilated with APRV in 4 groups based on whether inspiratory pressure was 28 or 40 cmH2O, and whether expiration was terminated when end-expiratory flow reached either 75% (a shorter expiration) or 25% (a longer expiration) of its initial peak value. A mathematical model of respiratory system mechanics that included a volume-dependent elastance term characterized by the parameter $${E}_{2}$$ was fit to airway pressure-flow data obtained each hour for 6 h post-Tween injury during both expiration and inspiration. We also measured respiratory system impedance between 5 and 19 Hz continuously through inspiration at the same time points from which we derived a time-course for respiratory system resistance ( $${R}_{rs}$$ ). $${E}_{2}$$ during both expiration and inspiration was significantly different between the two longer expiration versus the two shorter expiration groups (ANOVA, p < 0.001). We found that $${E}_{2}$$ was most depressed during inspiration in the higher-pressure group receiving the longer expiration, suggesting that $${E}_{2}$$ reflects a balance between strain stiffening of the lung parenchyma and ongoing recruitment as lung volume increases. We also found in this group that $${R}_{rs}$$ increased progressively during the first 0.5 s of inspiration and then began to decrease again as inspiration continued, which we interpret as corresponding to the point when continuing derecruitment was reversed by progressive lung inflation. These findings support the hypothesis that sufficiently short expiratory durations protect against atelectrauma because they do not give derecruitment enough time to manifest. This suggests a means for the personalized adjustment of mechanical ventilation.

中文翻译：

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如果呼气时间足够短，则可以避免无远端损伤：气道压力释放通气期间来自逆向建模和示波测定的证据


气道压力释放通气 （APRV） 已被证明在短暂呼气时可预防远端创伤。我们假设这是保护性的，因为上皮表面在呼气过程中没有得到足够的时间聚集在一起并粘附，从而避免了它们在吸气过程中极具破坏性的强制分离。我们在 Tween 灌洗诱导的 ARDS 猪模型中研究了这一假设。根据吸气压力是 28 还是 40 cmH2O，以及当呼气末流量达到其初始峰值的 75% （较短的呼气） 或 25% （较长的呼气） 时是否终止呼气，将动物分为 4 组。呼吸系统力学的数学模型包括以参数 $${E}_{2}$$ 为特征的体积依赖性弹性项，适用于吐温损伤后 6 小时在呼气和吸气期间每小时获得的气道压力流量数据。我们还通过吸气连续测量了 5 到 19 Hz 之间的呼吸系统阻抗，从中我们得出了呼吸系统阻力的时程 （ $${R}_{rs}$$ ）。两个较长的呼气组与两个较短的呼气组在呼气和吸气期间的 $${E}_{2}$$ 均存在显著差异（方差分析，p < 0.001）。我们发现，在接受较长呼气时间的高压组中，$${E}_{2}$$ 在吸气时最受抑制，这表明 $${E}_{2}$$ 反映了肺实质应变硬化与随着肺容量增加而持续募集之间的平衡。我们还发现，在这个组中，$${R}_{rs}$$ 在前 0 期间逐渐增加。5 s 的吸气，然后随着吸气的继续再次开始减少，我们将其解释为对应于持续肺复张消失被进行性肺充气逆转的时间点。这些发现支持这样一个假设，即足够短的呼气持续时间可以防止远动脉创伤，因为它们没有给征募失去足够的时间来表现。这提出了一种个性化调整机械通风的方法。