Li Bassi Gianluigi, Zanella Alberto, Cressoni Massimo, Stylianou Mario, Kolobow Theodor
Pulmonary and Critical Care Medicine Branch, Section of Pulmonary and Cardiac Assist Devices, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA.
Crit Care Med. 2008 Feb;36(2):518-25. doi: 10.1097/01.CCM.0000299741.32078.E9.
Critically ill intubated patients are positioned in the semirecumbent position to prevent pneumonia. In tracheally intubated sheep, we investigated the effects of gravitational force on tracheal mucus transport and on bacterial colonization of the respiratory system.
Prospective randomized animal study.
Animal research facility at the National Institutes of Health.
Sixteen healthy sheep.
Spontaneously breathing or mechanically ventilated sheep were randomized to be positioned with the orientation of the trachea above (40 degrees, trachea-up) or below (5 degrees, trachea-down) horizontal.
Tracheal mucus velocity was measured through radiographic tracking of radiopaque tantalum disks, insufflated into the trachea. After 24 hrs, sheep were euthanized, and samples from the airways and lungs were taken for microbiological analysis. The proximal trachea was colonized in all sheep. In trachea-down sheep, all mucus moved toward the glottis at a mean velocity of 2.1 +/- 1.1 mm/min. When mucus reached the endotracheal tube, it either entered the endotracheal tube or was lodged at the inflated endotracheal tube cuff. In all trachea-up sheep, abnormal tracheal mucus clearance was found. Mucus, mostly on the nondependent part of the trachea, moved toward the glottis at an average velocity of 2.2 +/- 2.0 mm/min and constantly accumulated at the inflated endotracheal tube cuff. From the proximal trachea, mucus eventually moved toward the lungs on the dependent part of the trachea, leading to an "intratracheal route" of colonization of the lungs. Pneumonia was found in 6/8 of trachea-up sheep and the same microorganisms were isolated from the lungs and the proximal trachea. No pneumonia was found in trachea-down sheep (p = .007).
The study indicates that following tracheal intubation gravitational force influences tracheal mucus clearance. When the trachea is oriented above horizontal, a flow of mucus from the proximal trachea toward the lungs is highly associated with bacterial colonization of the airways and pneumonia.
危重症插管患者采用半卧位以预防肺炎。在气管插管的绵羊中，我们研究了重力对气管黏液转运及呼吸系统细菌定植的影响。
前瞻性随机动物研究。
美国国立卫生研究院的动物研究设施。
16只健康绵羊。
将自主呼吸或机械通气的绵羊随机分为气管高于水平位（40度，气管向上）或低于水平位（5度，气管向下）的体位。
通过对注入气管的不透射线钽盘进行影像学追踪来测量气管黏液速度。24小时后，对绵羊实施安乐死，并采集气道和肺部样本进行微生物分析。所有绵羊的近端气管均有细菌定植。在气管向下的绵羊中，所有黏液均以2.1±1.1毫米/分钟的平均速度流向声门。当黏液到达气管内导管时，它要么进入气管内导管，要么滞留在充气的气管内导管套囊处。在所有气管向上的绵羊中，均发现气管黏液清除异常。黏液大多位于气管的非下垂部分，以2.2±2.0毫米/分钟的平均速度流向声门，并不断积聚在充气的气管内导管套囊处。从近端气管开始，黏液最终沿着气管的下垂部分流向肺部，导致肺部出现“气管内途径”的定植。在8只气管向上的绵羊中有6只发生了肺炎，且从肺部和近端气管分离出相同的微生物。气管向下的绵羊未发现肺炎（p = 0.007）。
该研究表明气管插管后重力会影响气管黏液清除。当气管高于水平位时，近端气管的黏液流向肺部与气道细菌定植及肺炎高度相关。
