We continue our discussion of airway management today. Proper endotracheal tube insertion is important to avoid mainstem bronchial intubation. Today's questions concern proper positioning of an ETT within the trachea.
1. What is the distance from the vocal cords to the carina in normal adults?
2. What is the appropriate distance from the teeth to the tip of an endotracheal tube? From the nares to the tip for a nasal intubation?
3. What is the effect of head position changes on the depth of an endotracheal tube?
恰当的气管内插管对避免主支气管插管非常重要，本周我们讨论ETT在气管内的恰当位置。
1. 正常成人丛声门到隆突的距离有多远？
2. 牙齿到气管导管头端的核实距离为多少？鼻插管时鼻孔到导管尖端的距离有多少？
3. 头部位置的变化对气管内插管深度有何影响？请详细描述。
参考答案：
恰当的气管内插管对避免主支气管插管非常重要，本周我们讨论ETT在气管内的恰当位置。
1. 正常成人丛声门到隆突的距离有多远？
令人惊讶的是，该数值的估计有显著差别。也许是因为测量方法（X线、纤维支气管镜检查、尸体直接检查、外科手术中直接观察）、使用解剖标志或研究人群（尸体解剖、ICU患者、健康的外科患者、男性或女性、患者身高的变异）的不同，估计的距离从11cm、12-15cm到16-17cm。比较共识的意见是气管导管位于隆突上5cm，这样导管尖端应该位于气管中段。
2. 牙齿到气管导管头端的核实距离为多少？鼻插管时鼻孔到导管尖端的距离有多少？
经口气管插管，推荐使用的公式和方法有很多种。但是，有两个前瞻性研究[1，2]认为，使用距离前切牙男性23cm女性21cm的插管深度，95%以上的位置正确（即隆突上5cm）。也有几种方法对合适的气管中段位置提出了建议，这包括光导纤维支气管镜检查、胸部X线摄影以及胸骨颈静脉切迹气囊触诊。后者不能确保气管位置正确（与食管相比），其更可靠的判断气管导管的气管中段位置。
3. 头部位置的变化对气管内插管深度有何影响？请详细描述。
头部位置变化时气管内插管发生移位对麻醉科医生来说很常见，但是对于移位的大小存在争论。像气管内插管一样，无意识下的气管导管拔除也屡有报道。1976年，Conrardy等[4]对ICU的危重病患者在半卧位进行影像学检查，结果认为气管长约12±3cm；颈部屈曲时导管平均前进1.9cm（范围0-3.1cm），颈部伸展位导管平均退出1.9cm（范围-0.2-5.2cm）。后边的研究没有对此进行确认。Mehta[5]发现屈曲位导管平均前进0.5cm。Yap等[6]进行了一个设计严密复杂的实验，通过纤维支气管镜测量不同头位下气管导管尖端到隆突的距离。不同头位下导管的平均运动范围：如图。
What is the distance from the vocal cords to the carina in normal adults?
Surprisingly, there is significant variation between estimates of this presumably easily determined value. Perhaps due to variations in measurement technique (radiographic, bronchoscopic, cadaveric direct observations, surgical direct observations), the anatomic landmarks used, or the population studied (postmortem, ICU patients, healthy surgical patients, men or women, variation in patient height) estimates range from 11 cm, 12-15 cm, to 16-17 cm. The common advice to position an ETT 5 cm above the carina stems from the former measurement; this should result in a mid-tracheal placement of the ETT tip.
What is the appropriate distance from the teeth to the tip of an endotracheal tube? From the nares to the tip for a nasal intubation?
In an oral ETT placement, many formulae and techniques have been proposed. However, two prospective trials (1,2) have concluded that using a depth of 23 cm from the frontal incisors in men and 21 cm in women results in correct placement in greater than 95% correct placement (i.e. 5 cm from the carina). Several methods have also been proposed for confirming proper midtracheal placement. These include fiberoptic bronchoscopy, chest radiography, and palpation of the cuff in the sternal notch. While the latter technique does not reliably confirm tracheal (versus esophageal) placement, it does reliably predict midtracheal placement of tracheal tubes.
Nasotracheal tubes can also be positioned using a simple guideline of 26 cm from the nares for females and 28 cm for males. A prospective study using this guideline found 96-98% correct placement in emergency room intubations (3).
What is the effect of head position changes on the depth of an endotracheal tube?
The movement of endotracheal tubes with changes in head position is well known to the practicing anesthesiologist, but has generated some controversy regarding the magnitude of the effect. Cases of unintentional extubation as well as mainstem bronchial intubation have been reported. In 1976 Conrardy et al. (4) studied 20 semi-erect critically ill patients in the ICU by radiography and concluded that the trachea was 12 ± 3 cm long. Flexion of the neck advanced the tube an average of 1.9 cm (range 0-3.1) and extension withdrew the tube 1.9 cm (range -0.2-5.2 cm). [Ed. note: a possibly helpful mnemonic is flexion further, extension exit.] Subsequent work has not confirmed either the consistency or the magnitude of this effect. Mehta (5) found flexion advanced the tube 0.5 cm on average. In a more sophisticated study, Yap et al. used fiberoptic bronchoscopy to measure the distance to the carina from the ETT tip with various manipulations of the head.
Therefore, while confirming the average direction of the movement of the tube, these authors found the change to be small on average and for there to be tremendous variation between patients. Only clinical assessment can verify continued proper tube placement after moving the patient's head.
References:
1. Owen RL, Cheney FW. Endobronchial intubation: a preventable complication. Anesthesiology 1987; 67:255-7.
2. Roberto JR, Sapdafora M, Cone DC. Proper depth placement of oral endotracheal tubes in adults prior to radiographic confirmation. Acad Emerg Med 1995; 2:20-4.
3. Reed DB, Clinton JE. Proper depth of placement of nasotracheal tubes in adults prior to radiographic confirmation.
4. Conrardy PA, Goodman LR, Laing EF, et al. Alteration of endotracheal tube position. Flexion and extension of the neck. Crit Care Med 1976; 4:8-12.
5. Mehta S. Intubation guide marks for correct tube placement: a clinical study. Anaesthesia 1991; 46:306-8.
6. Yap SJ, Morris RW, Pybus DA. alterations in endotracheal tube position during general anesthesia. Anaesth Intens Care 1994; 22:586-8.
编辑：西门吹血
作者: 西门吹血
| 以下网友留言只代表网友个人观点，不代表网站观点 | |||