BackgroundVentilator-associated pneumonia (VAP) is the most common nosocomial infection in intensive care units. Distal airway mucus clearance has been shown to reduce VAP incidence. Studies suggest that mucus clearance is enhanced when the rate of expiratory flow is greater than inspiratory flow. The time-controlled adaptive ventilation (TCAV) protocol using the airway pressure release ventilation (APRV) mode has a significantly increased expiratory relative to inspiratory flow rate, as compared with the Acute Respiratory Distress Syndrome Network (ARDSnet) protocol using the conventional ventilation mode of volume assist control (VAC). We hypothesized the TCAV protocol would be superior to the ARDSnet protocol at clearing mucus by a mechanism of net flow in the expiratory direction.MethodsPreserved pig lungs fitted with an endotracheal tube (ETT) were used as a model to study the effect of multiple combinations of peak inspiratory (IPF) and peak expiratory flow rate (EPF) on simulated mucus movement within the ETT. Mechanical ventilation was randomized into 6 groups (n = 10 runs/group): group 1—TCAV protocol settings with an end-expiratory pressure (PLow) of 0 cmH2O and PHigh 25 cmH2O, group 2—modified TCAV protocol with increased PLow 5 cmH2O and PHigh 25 cmH2O, group 3—modified TCAV with PLow 10 cmH2O and PHigh 25 cmH2O, group 4—ARDSnet protocol using low tidal volume (LTV) and PEEP 0 cmH2O, group 5—ARDSnet protocol using LTV and PEEP 10 cmH2O, and group 6—ARDSnet protocol using LTV and PEEP 20 cmH2O. PEEP of ARDSnet is analogous to PLow of TCAV. Proximal (towards the ventilator) mucus movement distance was recorded after 1 min of ventilation in each group.ResultsThe TCAV protocol groups 1, 2, and 3 generated significantly greater peak expiratory flow (EPF 51.3 L/min, 46.8 L/min, 36.8 L/min, respectively) as compared to the ARDSnet protocol groups 4, 5, and 6 (32.9 L/min, 23.5 L/min, and 23.2 L/min, respectively) (p < 0.001). The TCAV groups also demonstrated the greatest proximal mucus movement (7.95 cm/min, 5.8 cm/min, 1.9 cm/min) (p < 0.01). All ARDSnet protocol groups (4–6) had zero proximal mucus movement (0 cm/min).ConclusionsThe TCAV protocol groups promoted the greatest proximal movement of simulated mucus as compared to the ARDSnet protocol groups in this excised lung model. The TCAV protocol settings resulted in the highest EPF and the greatest proximal movement of mucus. Increasing PLow reduced proximal mucus movement. We speculate that proximal mucus movement is driven by EPF when EPF is greater than IPF, creating a net force in the proximal direction.

中文翻译：

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时间控制的自适应通气 (TCAV) 通过增加呼气流速加速模拟粘液清除

背景呼吸机相关性肺炎 (VAP) 是重症监护病房中最常见的院内感染。已显示远端气道粘液清除可降低 VAP 的发生率。研究表明，当呼气流速大于吸气流速时，粘液清除能力增强。与使用常规通气模式的急性呼吸窘迫综合征网络 (ARDSnet) 协议相比，使用气道压力释放通气 (APRV) 模式的时间控制自适应通气 (TCAV) 协议相对于吸气流速具有显着增加的呼气流量。音量辅助控制 (VAC)。我们假设 TCAV 协议在通过呼气方向的净流量机制清除粘液方面优于 ARDSnet 协议。方法以装有气管插管 (ETT) 的保存猪肺为模型，研究吸气峰 (IPF) 和呼气峰流速 (EPF) 的多种组合对 ETT 内模拟粘液运动的影响。机械通气随机分为 6 组（n = 10 次/组）：第 1 组——TCAV 协议设置，呼气末压力 (PLow) 为 0 cmH2O 和 PHigh 25 cmH2O，第 2 组——改进的 TCAV 协议，增加 PLow 5 cmH2O和 PHigh 25 cmH2O，第 3 组——使用 PLow 10 cmH2O 和 PHigh 25 cmH2O 的改良 TCAV，第 4 组——使用低潮气量 (LTV) 和 PEEP 0 cmH2O 的 ARDSnet 协议，第 5 组——使用 LTV 和 PEEP 10 cmH2O 的 ARDSnet 协议，以及组6 - 使用 LTV 和 PEEP 20 cmH2O 的 ARDSnet 协议。ARDSnet 的 PEEP 类似于 TCAV 的 PLow。在每组通气 1 分钟后记录近端（朝向呼吸机）粘液运动距离。结果 TCAV 方​​案第 1、2 和 3 组产生显着更大的呼气峰值流量（EPF 51.3 L/min、46.8 L/min、36.8 L /min) 与 ARDSnet 协议组 4、5 和 6（分别为 32.9 L/min、23.5 L/min 和 23.2 L/min）相比（p < 0.001）。TCAV 组还表现出最大的近端粘液运动（7.95 cm/min、5.8 cm/min、1.9 cm/min）（p < 0.01）。所有 ARDSnet 协议组 (4-6) 的近端粘液运动为零 (0 cm/min)。结论与 ARDSnet 协议组相比，TCAV 协议组在该切除肺模型中促进了模拟粘液的最大近端运动。TCAV 协议设置导致最高的 EPF 和最大的粘液近端运动。增加 PLow 减少近端粘液运动。我们推测，当 EPF 大于 IPF 时，近端粘液运动是由 EPF 驱动的，从而在近端方向产生净力。