Identification of the difficult airway

Nearly all patients who are seriously difficult to manage are easily identified because they have grossly obvious abnormalities. Conversely, it is difficult to identify the few normal-looking patients that are difficult to manage.     

Alternative techniques for tracheal intubation

Alternative rigid blade intubation devices available in recent years include the Glidescope, Airtraq and Bonfils laryngoscopes. The Macintosh blade works by displacing the tongue to one side and into the submandibular space while the tip of the device sits in the vallecula lifting the hyoid and so the epiglottis forward to reveal the laryngeal inlet. Under less favourable intubating conditions, the tongue is not accommodated in the submandibular space and tends to be compressed downwards. As a result the vallecula is not accessible and the blade tip is less able to be drawn forward. The retro-molar Bonfils avoids this problem by starting from a posterior position in the mouth and approaching the larynx below and alongside the tongue. The Bonfils also serves as a rigid stylet inside the tracheal tube again producing minimal tongue displacement. Airtraq also compresses the tongue less and usually sits on the posterior pharyngeal wall where it maintains the laryngeal view with a minimum of effort. It houses the tracheal tube in a channel that delivers it into the device's field of view. While better optical systems have tended to improve visualization of the laryngeal inlet, this has not necessarily resulted in easier intubation conditions, shorter intubation times or improved overall success rates. Part of the problem has been that they have limited fields of view compared with the stereoscopic view of tube advancement down to the larynx as afforded by Macintosh.     

术前不同CT测量方式对指导双腔支气管插管效果的影响

目的探讨CT平扫及重建分别应用于指导患者双腔支气管插管的效果,并分析气管内径与患者一般资料的相关性。方法选择2015年6月至2018年6月于我院行择期肺叶切除的患者53例,按照随机数字表法分为平扫组(n=27)和重建组(n=26),两组患者均于麻醉前行CT检查支气管情况,平扫组采用CT平扫法进行测量,而重建组则采用CT重建法进行测量,而后根据测量结果行双腔支气管插管。比较两组患者导管合适程度评价指标情况,插管并发症之间的差异。对患者通过重建测量出的气管内径与其身高、体重、年龄和BMI等一般资料进行相关性分析。结果重建组LT1、PT1及APP显著低于平扫组,插管1次成功率显著高于平扫组(P<0.05),重建组患者插管并发症总发生率显著低于平扫组(P<0.05);重建组胸廓入口处、主动脉弓处以及气管最狭窄处气管内径值显著高于平扫组(P<0.05);Pearson相关分析显示,身高与气管四个位置的内径呈正相关(P<0.05)。结论CT重建应用于指导双腔支气管导管型号的选择,能有效提升术前气管导管选择型号合适程度,并有效减少插管并发症;患者身高与气管内径呈显著正相关。     

Clinical tests for confirming tracheal intubation or excluding oesophageal intubation: a diagnostic test accuracy systematic review and meta-analysis

Unrecognised oesophageal intubation causes preventable serious harm to patients undergoing tracheal intubation. When capnography is unavailable or doubted, clinicians still use clinical findings to confirm tracheal intubation, or exclude oesophageal intubation, and false reassurance from clinical examination is a recurring theme in fatal cases of unrecognised oesophageal intubation. We conducted a systematic review and meta-analysis of the diagnostic accuracy of five clinical examination tests and the oesophageal detector device when used to confirm tracheal intubation. We searched four databases for studies reporting index clinical tests against a reference standard, from inception to 28 February 2023. We included 49 studies involving 10,654 participants. Methodological quality was overall moderate to high. We looked at misting (three studies, 115 participants); lung auscultation (three studies, 217 participants); combined lung and epigastric auscultation (four studies, 506 participants); the oesophageal detector device (25 studies, 3024 participants); ‘hang-up’ (two non-human studies); and chest rise (one non-human study). The reference standards used were capnography (22 studies); direct vision (10 studies); and bronchoscopy (three studies). When used to confirm tracheal intubation, misting has a false positive rate (95%CI) of 0.69 (0.43–0.87); lung auscultation 0.14 (0.08–0.23); five-point auscultation 0.18 (0.08–0.36); and the oesophageal detector device 0.05 (0.02–0.09). Tests to exclude events that invariably lead to severe damage or death must have a negligible false positive rate. Misting or auscultation have too high a false positive rate to reliably exclude oesophageal intubation and there is insufficient evidence to support the use of ‘hang-up’ or chest rise. The oesophageal detector device may be considered where other more reliable means are not available, though waveform capnography remains the reference standard for confirmation of tracheal intubation.     

Transtracheal jet ventilation

Transtracheal jet ventilation is a technique for ventilation of apnoeic lungs. This article outlines the indications, equipment required, insertion technique and complications of transtracheal jet ventilation. It can be used electively to aid management of the difficult airway and for laryngeal surgery. It also has a vital role in the management of the ‘can't intubate – can't ventilate’ scenario. Death and hypoxic brain damage under anaesthesia are fortunately rare, but most commonly occur as a result of problems with tracheal intubation. No patient should suffer hypoxic brain damage without an attempt at transtracheal ventilation being made.     

芬太尼复合不同浓度七氟醚吸入诱导对气管插管反应的影响

目的:比较肺活量吸入诱导法中不同七氟醚维持诱导浓度对气管插管反应的影响.方法:选择ASAⅠ~Ⅱ级,年龄20~50岁,将择期行腹腔镜手术的女性患者60例随机分为A、B、C三组各20例.各组诱导前静脉注射2μg·kg-1芬太尼,2 min后使用肺活量法吸入8%七氟醚,意识消后失立即静脉注射0.2 mg·kg-1顺式阿曲库铵,同时三组分别换用3%,5%和8%七氟醚维持诱导,面罩机械通气3 min后气管插管,使用Narcotrend监测诱导期的麻醉深度,记录诱导过程中和气管插管后意识消失的时间,气道反应及血流动力学变化.结果:(1)插管前C组MBP下降最明显,达基础值(MBPbase)的33.6%(P <0.001);(2)插管后1min,三组MBP上升至最大值,与MBPbase相比无统计学差异(P >0.05);与插管前相比,三组上升幅度为A组34.9%(P <0.01)、B组27.7%(P <0.001)和C组32.9%(P <0.01).插管后2 min三组HR上升到最大值,与插管前比较,三组上升幅度分别为A组20.0%(P <0.01)、B组15.2%(P <0.001)和C组20.6%(P <0.01).(3)诱导插管过程中,C组MBPmin较MBPbase下降42.2%(P <0.001),C组HRmax较HRbase升高22.3%(P <0.01).(4)C组MBP降低<30% MBPbase和HR升高>100次/分的发生率均高于A、B组(P <0.001).结论:芬太尼2μg·kg-1复合3%、5%、8%七氟醚吸入诱导均可减轻气管插管反应,芬太尼与5%七氟醚复合诱导血流动力学最稳定.     

在头戴式放大镜直视下小鼠气管插管方法的建立

目的建立并评价一种新的小鼠气管插管方法。方法30只NIH小鼠分设A、B、C组(n=10),麻醉后特殊体位固定,在头戴式放大镜直视下施行气管插管。A组小鼠经套管注射美蓝,死后解剖判断插管成功与否;B组插管后即拔管,隔天1次,连续2周。C组仅麻醉但不插管,方法同B组。在实验的最后1天,B、C组小鼠的处理同A组。结果所有小鼠死后解剖可见气管下端至肺部均有蓝色物质浸染,插管成功率为100%,B组小鼠经多次插管操作仍能健康存活,与C组比较未发现生长迟缓、体重明显减低等情况。结论我们建立的小鼠气管插管方法操作简单、易学、可重复性强,值得推广。     

气管插管全麻术中预防气道感染的临床研究

目的观察一次性病毒/细菌过滤器在气管插管全麻术中预防气道感染的应用价值,为临床预防策略的制定提供参考。方法选择2011年3月-2013年3月接受气管插管全麻手术的患者76例,按照随机数字表法将其分为观察组和对照组各38例;观察组应用一次性病毒/细菌过滤器,而对照组则未用,分别在麻醉前和手术结束时用无菌棉签采集麻醉机呼气端、吸气端表面标本行细菌学检测;在手术结束时收集钠石灰罐底部10g钠石灰行细菌学检测,对比两组患者的检测结果和术后24h内气道感染发生率。结果两组患者在麻醉开始前麻醉机呼气端、吸气端细菌学培养结果均为阴性;手术结束时,麻醉机吸气端、呼气端和钠石灰的细菌学培养阳性率均为0,对照组分别为5.26%、42.11%和15.79%,观察组细菌培养阳性率均显著低于对照组,差异有统计学意义(P<0.05);术后24h内气道感染发生率观察组为2.63%,显著低于对照组的18.62%,差异有统计学意义(P<0.05)。结论麻醉机气管插管全麻可增加患者气道感染的机会,通过一次性病毒/细菌过滤器、及时更换钠石灰等措施,可有效预防气道感染的发生。     

Understanding and improving airway management in companion animals - part 1

Airway Management, briefly taught within the veterinary nursing curriculum, is performed many times a day and a vital part of the anaesthesia process. Students are shown how to place an endotracheal tube, taught little about dead-space and airway resistance but, although there are many publications on the pitfalls of intubation, it is often sub-optimally managed in a busy clinic. To provide excellent, safe airway management for our patients, we must understand the history, mechanics and pitfalls about the process: It is only then can we truly apply better techniques in order to improve both care and safety to our patients.