【Cochrane简语概要】床边检查以发现有可能难以插管的成人

系统综述问题 

我们寻找最合适和准确的快速筛选试验以能在没有明显气道异常的成年人中，确定那些可能难以插管的人（即插管入气管内）。

研究背景 

气管插管确保病人在被深度镇静、昏迷或麻醉时的气道畅通，以便他们的呼吸可以通过机器（通气）来控制，并且在手术中，在主要创伤、危重疾病或心脏停止跳动之后可以提供病人适当的氧水平。有难以插管的气道是一种潜在性危及生命的情况。

插管前做的喉镜检查（插入微型摄像机以查看插入管的路线），需要先进的技能，通常可以顺利完成检查。插管在大约10%的患者中是困难的，需要特殊的设备和预防措施。一些物理特征与困难气道和插管失败有关，因此警告潜在的困难气道将是有帮助的。几个快速床边测试是在常规临床使用，以确定那些高风险的困难气道，但这些测试有多准确仍然不清楚。

（图片来源于网络）

人口 

我们纳入了16岁或以上没有明显气道异常的成年人接受标准插管的研究。

在研究中的测试 

我们评估了七个最常见的床边测试，常规用于检测困难气道。这些测试只需几秒钟就完成，不需要特殊设备。

诊断测试包括：

- Mallampati试验（原版或改版；要求就诊病人张开嘴，尽可能突出舌头，以便确定咽部结构可见度）；

- Wilson风险评分（包括患者的体重、头颈部运动、下颌运动、下颚下移、颊齿）；

-甲状腺距离（下颚与喉结上缘之间的长度）；

-胸骨间距（颏与领骨间凹口的长度）；

-张口试验；

-上唇咬合试验；

-或者这些测试的任何组合。

检索日期 

当前证据检索截至2016年12月16日。（我们在2018年3月检索了新的研究，但我们还没有把它们纳入这项系统综述。）

研究特征 

我们纳入了133项研究（844206位受试者），研究了七个以上测试的准确性，再加上69个其他常见的测试和32个测试组合，在检测困难气道的应用。

主要结果 

对于困难的喉镜检查，平均的诊断的灵敏度（正确诊断困难气道的百分比）范围从22%（张口试验）到63%（上唇咬合试验）。平均特异度（正确诊断无困难气道的患者的百分比）从80%（改良Mallampati试验）到95%（Wilson风险评分）。上唇咬合试验在所有测试中的灵敏度最高。

对于困难的气管插管，平均诊断的灵敏度范围从24%（甲状腺距离）到51%（改良Mallampati试验），平均特异度从87%（改良Mallampati试验）到93%（张口试验）。修改后的Mallampati测试具有所有测试中最高灵敏度。

对于面罩通气困难（另一个困难气道的指示），只有足够的数据来计算修改后的Mallampati测试的平均灵敏度为17%和特异度为90%。

证据质量 

总体而言，研究的证据是中等到高等质量。研究提供可靠结果的可能性通常很高，虽然其中的一半，插管医师知道先前测试的结果，这可能影响结果，但这是常规临床护理中的正常情况。在大多数日常临床场所中，患者、测试和条件的特点是可比的。这项系统综述的结果应适用于在世界各地显然是正常的医院患者的标准的术前气道评估。

结论 

这项系统综述中检索的床边筛查测试不适合于检测预料之外的困难气道，因为他们错过了大量的气道困难的人。

结论: 

床边气道检查试验，以评估没有明显气道解剖异常的成人患者气道的物理状况，设计为筛选试验。诊断试验预期会有很高灵敏度。我们发现所有研究的诊断试验都具有低灵敏度和高变异性。相比之下，特异度在所有试验中较一致，显著高于所有诊断试验的灵敏度。标准床边气道检查应谨慎诠释，因为它们似乎不是很好的筛选试验。在我们所评估的诊断试验中，上唇咬合试验的准确度最高。鉴于现有数据的匮乏，未来的研究需要开发具有高诊断灵敏度的测试，并考虑其用于筛选困难面罩通气和插管失败。在尚未分类的27项研究中，一旦我们评估了这些研究的结果，就可能改变系统综述的结论。

译者：Nyuk Jet Chong；审校：李静，北京中医药大学循证医学中心；编辑排版：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】Bedside examination tests to detect beforehand adults who are likely to be difficult to intubate

Review question

We looked for the most suitable and accurate rapid screening test in adults with no obvious airway abnormalities, to identify those who are likely to be difficult to intubate (i.e. insertion of a tube into the windpipe).

Background

Intubation ensures a patient’s airway is clear while they are heavily sedated, unconscious or anaesthetized, so their breathing can be controlled by machine (ventilation), and appropriate levels of oxygen can be given during surgery, following major trauma, during critical illness, or following cardiac arrest. Having an airway that is difficult to intubate is a potentially life-threatening situation.

Tube insertion is preceded by laryngoscopy (insertion of mini-camera to view route of tube insertion), requires advanced skills, and is generally uneventful. Intubation is difficult in approximately 10% of patients, who require special equipment and precautions. Several physical features are associated with difficult airways and failed intubation, so warning of potentially difficult airways would be helpful. Several quick bedside tests are in routine clinical use to identify those at high risk for difficult airways, but how accurate these are remains unclear.

Population

We included studies of adults aged 16 years or older without obvious airway abnormalities who were to receive standard intubation.

Test under investigation

We assessed the seven most common bedside tests, routinely used to detect difficult airways. These take only a few seconds to complete and require no special equipment.

The index tests (diagnostic tests of interest) included:

- the Mallampati test (original or modified; asking a sitting patient to open his mouth and to protrude the tongue as much as possible so that visibility can be determined);

- Wilson risk score (including patient's weight, head and neck movement, jaw movement, receding chin, buck teeth);

- thyromental distance (length between the chin and the upper edge of Adam's apple);

- sternomental distance (length between the chin and the notch between the collar bones);

- mouth opening test;

- upper lip bite test;

- or any combination of these tests.

Search date

The evidence is current to 16 December 2016. (We searched for new studies in March 2018, but we have not yet included them in the review.)

Study characteristics

We included 133 studies (844,206 participants) which investigated the accuracy of the seven tests above, plus 69 other common tests and 32 test combinations, in detection of difficult airways.

Key results

For difficult laryngoscopy, the average sensitivity (percentage of correctly identified difficult airways) ranged from 22% (mouth opening test) to 63% (upper lip bite test). The average specificity (percentage of correctly classified patients without difficult airways) ranged from 80% (modified Mallampati test) to 95% (Wilson risk score). The upper lip bite test had the highest sensitivity of all tests considered.

For difficult tube insertion, the average sensitivity ranged from 24% (thyromental distance) to 51% (modified Mallampati test) and the average specificity ranged from 87% (modified Mallampati test) to 93% (mouth opening test). The modified Mallampati test had the highest sensitivity of all tests considered.

For difficult face mask ventilation (another indication of a difficult airway), there were only enough data to calculate average sensitivity of 17% and specificity 90% for the modified Mallampati test.

Quality of the evidence

Overall, the evidence from the studies was of moderate to high quality. The likelihood of the studies providing reliable results was generally high, although in half of them, the intubating physician knew the result of the preceding test, which may have influenced results, but this is the normal situation in routine clinical care. The characteristics of patients, tests, and conditions were comparable to those seen in a wide range of everyday clinical settings. The results of this review should apply to standard preoperative airway assessments in apparently normal hospital patients worldwide.

Conclusion

The bedside screening tests examined in this review are not well suited for the purpose of detecting unanticipated difficult airways because they missed a large number of people who had a difficult airway.

Authors' conclusions: 

Bedside airway examination tests, for assessing the physical status of the airway in adults with no apparent anatomical airway abnormalities, are designed as screening tests. Screening tests are expected to have high sensitivities. We found that all investigated index tests had relatively low sensitivities with high variability. In contrast, specificities were consistently and markedly higher than sensitivities across all tests. The standard bedside airway examination tests should be interpreted with caution, as they do not appear to be good screening tests. Among the tests we examined, the upper lip bite test showed the most favourable diagnostic test accuracy properties. Given the paucity of available data, future research is needed to develop tests with high sensitivities to make them useful, and to consider their use for screening difficult face mask ventilation and failed intubation. The 27 studies in 'Studies awaiting classification' may alter the conclusions of the review, once we have assessed them.

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