【Cochrane简语概要】与平板床对比，抬高床头可预防呼吸机相关性肺炎？

研究背景

危重病成人通常需要机器来帮助他们维持其呼吸。这些呼吸机的副作用之一是增加了患肺炎的风险。这被称为呼吸机相关性肺炎（ventilator-associated pneumonia,VAP）。这是危重病人的主要死亡原因，同时也会增加住院时间以及医疗成本。通气病人的躺卧角度可能对预防肺部感染起到重要作用。

系统综述问题

通过倾斜医院病床的角度抬高床头可能会阻止感染源进入肺部。我们评价了半卧位在需要机械通气的危重成人患者中预防呼吸机相关性肺炎的利弊。我们还研究了半卧位时床头仰角的最佳角度。

研究特征

我们纳入10项研究，涉及878名受试者。28名受试者在随访过程中失访了。证据检索截止到2015年10月27日。所有受试者均招募于重症监护室（intensive care units,ICU），并接受了超过48小时的机械通气。

（图片来源于网络）

主要结果和证据质量

来自8项涉及759名受试者的研究（中等质量证据）表明，与0°至10°仰卧位相比，半卧位（30º至60º）可将临床怀疑的呼吸机相关性肺炎降低25.7％。根据此结果，我们预期在半卧位（30º至60º）护理超过48小时的1000名重症成年患者中，与仰卧0°至10°护理的402名患者相比，有145名患者将经历临床怀疑的呼吸机相关性肺炎。在减少微生物证实的呼吸机相关性肺炎（极低质量证据）、死亡率（低质量证据）、ICU住院时间（中等质量证据）、住院时间（极低质量证据）、通气时间或抗生素使用方面，两种方式均无显著差异。证据的主要局限性是纳入分析的数据基于少量的受试者，对于某些研究，研究人员会知道受试者来自哪个治疗组（存在偏倚风险）。

只有2项研究对91名受试者比较了不同的床头角度（半卧位45°与25°至30°）。极低质量证据表明，呼吸机相关性肺炎在（临床怀疑和微生物确认）、死亡率（ICU和住院）、ICU住院时间或抗生素的使用方面的效果，在统计学上无显著性差异。只有1项研究报告了压疮的不良事件，并且在45°半卧位和10°仰卧位之间没有发现差异。没有报告其他不良事件，如血栓栓塞，或对心率、血压的副作用。

由于研究数量和现有低质量证据的限制，半卧位姿势的利弊平衡仍不确定。关于半卧位、仰卧位以及最佳床头仰角的效果，需要更多高质量的证据。

结论: 

与0°至10°仰卧位相比，半卧位（≥30º）可能会减少临床上可疑的呼吸机相关性肺炎。但是，证据严重受限，存在高偏倚风险。没有足够证据可以得出关于其他结局和其他半卧位比较的明确结论。不良事件，特别是静脉血栓栓塞，报告不足。

译者：杨思红，审校：鲁春丽；编辑排版：刘美迪、张晓雯，北京中医药大学循证医学中心

相关文章链接

【Cochrane Plain Language Summary】Head bed elevation versus flat bed for preventing ventilator‐associated pneumonia (VAP) in adults requiring mechanical ventilation

Background

Adults who are critically ill often need a machine to help maintain their breathing. One side effect of these machines is an increased risk of pneumonia. This is known as ventilator‐associated pneumonia (VAP). It is a leading cause of death in critically ill patients and can also increase the length of hospital stay and healthcare costs. The angle at which ventilated patients lie might play an important role in preventing the infection of their lungs.Adults who are critically ill often need a machine to help maintain their breathing. One side effect of these machines is an increased risk of pneumonia. This is known as ventilator‐associated pneumonia (VAP). It is a leading cause of death in critically ill patients and can also increase the length of hospital stay and healthcare costs. The angle at which ventilated patients lie might play an important role in preventing the infection of their lungs.

Review questions

Head bed elevation by tilting the angle of the hospital bed might prevent the source of infection from getting into the lung. We assessed the benefit and harm of semi‐recumbent positioning for the prevention of VAP in critically ill adult patients requiring mechanical ventilation. We also investigated the best angle of head bed elevation in a semi‐recumbent position.

Study characteristics

We identified 10 studies involving 878 participants. Twenty‐eight participants were lost to follow‐up. The evidence is current up to 27 October 2015. All participants were recruited from intensive care units (ICUs) and received mechanical ventilation for more than 48 hours.

Key results and quality of the evidence

Moderate quality evidence from eight studies involving 759 participants demonstrated that a semi‐recumbent (30º to 60º) position reduced clinically suspected VAP by 25.7% when compared to a 0° to 10° supine position. Based on this result, we would expect that out of 1000 critically ill adult patients who are nursed in the semi‐recumbent position (30º to 60º) for more than 48 hours, 145 patients would experience clinically suspected VAP compared to 402 patients nursed in the 0° to 10° supine position. There was no significant difference between the two positions in reducing microbiologically confirmed VAP (very low quality evidence), mortality (low quality evidence), length of ICU stay (moderate quality evidence), hospital stay (very low quality evidence), duration of ventilation or use of antibiotics. The main limitations of the evidence were the small numbers of participants contributing data to the analyses and that for some studies researchers would have known which treatment group participants were from (a risk of bias). 

Only two studies with 91 participants compared different degrees of bed head angle (45° versus 25° to 30° semi‐recumbent position). Very low quality evidence showed no statistically significant differences in the effects of VAP (clinically suspected and microbiologically confirmed), mortality (ICU and hospital), length of ICU stay or use of antibiotics. Only one study reported the adverse event of pressure ulcers and did not find a difference between the 45° semi‐recumbent and 10° supine positions. No other adverse events, such as thromboembolism, or side effects on heart rate or blood pressure were reported. 

The balance of the benefit and harm of semi‐recumbent positioning still remains uncertain due to the limited numbers of studies and the low quality of the existing evidence. More high quality evidence is required on the effects of the semi‐recumbent versus supine position and the optimal body positions.

Authors' conclusions:

A semi‐recumbent position (≧ 30º) may reduce clinically suspected VAP compared to a 0° to 10° supine position. However, the evidence is seriously limited with a high risk of bias. No adequate evidence is available to draw any definitive conclusion on other outcomes and the comparison of alternative semi‐recumbent positions. Adverse events, particularly venous thromboembolism, were under‐reported.

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