Endotracheal intubation is one of the most common procedures used by anesthesiologists, intensivists, and emergency personnel. Complications, such as carinal impingement or endobronchial intubation, are associated with increased incidence of barotrauma, contralateral lung collapse, or both, which result in hypoxemia and hemodynamic instability . One study of emergency orotracheal intubation during cardiac arrest showed a 25% incidence of unrecognized endobronchial intubation . In intensive care patients, the endotracheal tube (ETT) was demonstrated to be close to the tracheal bifurcation, 9% to 15% requiring repositioning [3-5].
For confirmation of ETT placement, fiberoptic bronchoscopy is considered by many to be the definitive procedure, but it is not performed routinely. An alternative, chest radiography, is mainly used in cases of prolonged intubation. One study attempted to correlate the length of the ETT with adequate placement from post mortem body measurements. The investigators recommended securing the ETT (placed at the level of the incisors) at a distance equal to that between the cricoid cartilage and the xiphoid cartilage . Another study using radiography in intensive care patients (men between 165 and 184 cm in height, women between 158 and 174 cm) recommended securing the ETT at the 23-cm mark in men and at the 21-cm mark in women . No attempts were made to standardize head positioning or distance between the radiographic source and the patient, nor was any consideration given to patients of other heights or with abnormal anatomy.
Palpation of the ETT cuff has been used by clinicians for many years to confirm depth of intubation, but the effectiveness of this technique has never been documented. This study was undertaken to determine whether a modification of that technique--palpation of the cuff at the suprasternal notch--could serve as a valid method of placing the ETT a safe distance from carina. The suprasternal notch was chosen as the reference point because it is a fixed anatomic feature. Based on cadaveric studies, the ETT at this point will be well below the vocal cords and within 5 +/- 2 cm of the carina .
Informed consent was not required by the institutional review board, which approved the study. Consecutive adults undergoing general anesthesia during a 3-wk period at one institution were studied, except those who met the following exclusion criteria: Age < 16 yr; intubation with an uncuffed ETT or elective fiberoptic intubation planned as part of the anesthetic; ventilation with positive end-expiratory pressure > 5 cm H2 O, a fraction of inspired oxygen > 0.6, or both; cervical collar in place; increased intracranial pressure, proven or suspected from the patient's history or condition; and presence of a mass that obscured the suprasternal notch. Patients were not otherwise excluded on the basis of operative procedure or severity of their medical conditions. The resulting study group consisted of 82 patients, whose ASA physical status ranged from I to IV.
The anesthetic plan for each patient was decided on by the attending anesthesiologist. For each patient, continuous electrocardiogram, end-tidal carbon dioxide, oxygen saturation by pulse oximetry, temperature, and blood pressure were measured noninvasively. Invasive monitoring was used at the discretion of the attending anesthesiologist. After the patient breathed oxygen, endotracheal intubation was performed in the usual manner. Once endotracheal placement of the ETT was confirmed, the patient's head was placed in a neutral position, and ventilation with 100% oxygen was administered. The ETT was then withdrawn or advanced while gentle, repetitive pressure was applied with the fingers at the level of the suprasternal notch. Simultaneously, in the other hand, the pilot balloon was held to determine when it became maximally distended in reaction to pressure applied at the notch, at which point the ETT was secured Figure 1. The distance (in cm) from the ETT tip to the upper incisors was the recorded.
Before anesthetic induction, the selected ETT had been measured against a pediatric bronchoscope, and the length of the tube marked on the bronchoscope (Mark 1). After successful endotracheal intubation, the ETT was briefly disconnected from the ventilator while the pediatric bronchoscope was passed through the ETT. The distance from the carina to the ventilator end of the ETT was marked on the bronchoscope (Mark 2). The bronchoscope was then removed, and ventilation recommenced. The entire process took only 15-30 s. The distance between the two marks on the bronchoscope was taken as the distance between the tip of the ETT and the carina. This distance was recorded, along with the patient's ASA physical status and age and the size of the ETT.
The sizes of the ETTs used and the distances measured from the ETT tips were within expected ranges Table 1. The most frequent distance from the ETT tip to incisors was 21-22 cm Figure 2 and from the ETT to carina 2-3 cm Figure 3. Bronchoscopy showed no endobronchial intubation, and no ETT manipulation was deemed necessary after the initial insertion.
Once tracheal location of the ETT has been confirmed, proper placement of the ETT relative to the carina remains a concern. In one study, the incidence of malposition of the ETT in intubated patients, depending on the acuity of the intubation, varied from 9% to 28% [2,8,9].
It has been shown that, in patients in whom the right mainstem bronchus was intubated, the incidence of hyperventilation, pneumothorax, and atelectasis was increased [9-11]. Seizure and cardiac arrhythmia also occur more frequently in these circumstances . Breath sounds are compared routinely after ETT placement to check for endobronchial intubation, yet endobronchial placement of an ETT has gone undetected for as long as 24 h, even with the use of chest radiography . Diminished breath sounds on one side necessitates the immediate withdrawal of the ETT until breath sounds become equal. With partial blockage of the left mainstem bronchus, however, breath sounds may be normal. End-tidal carbon dioxide measurements may also be inaccurate in confirming endobronchial intubation .
In a study of displacement of ETT position by manipulation of the neck in orally intubated patients , both ETT and carina were moved down by flexion and up by extension and lateral movement. The net ETT-to-carina movement toward the carina with flexion was 1.5 cm; from the carina with extension, 2.4 cm; and away with lateral rotation, 1.4 cm. The present study confirms that our technique provides safe placement of the ETT relative to the carina: A movement of 1.5 cm provided by flexion would not bring the ETT into contact with the carina if the ETT were placed as recommended. The distance from vocal cords to carina is between 10 and 15 cm and is a function of height. Because it is 6.5 cm from the tip, the proximal end of the cuff would be on average 9.5 cm above the carina. With extension of the neck and a smaller trachea, impingement on the vocal cords is possible.
To avoid carinal impingement or endobronchial intubation, certain depths at which to insert the ETT have been recommended: 21 cm in women and 23 cm in men , which supposedly provide a 4-cm clearance from the tracheal bifurcation . Using the palpation technique and measuring from the upper incisors, we found the range of depth of the ETT in women was 17-23 cm and in men was 19-25 cm. These figures should not be taken as new guidelines for depth of intubation but, rather, should emphasize that following guidelines unthinkingly for endotracheal intubation may risk malpositon of the ETT. With the modified palpation technique, ETT placement can be individualized with assurance.
Palpation of the ETT cuff at the suprasternal notch provides a reliable, cost-effective indication of correct ETT placement. We think this technique has several advantages over other methods of locating the ETT within the trachea. First is the ease and rapidity with which the technique can be performed. (The entire procedure takes approximately 10 s for anyone with a knowledge of anatomy.) Second, it can be taught to any individual responsible for securing an airway. Thirdly, the procedure can be used when no other method for confirming placement of the ETT is available. Finally the cost is minimal in comparison with that of chest radiography or fiberoptic bronchoscopy.
This technique should not be used to verify location within the trachea [17,18]. The results of the present study, however, do show that when tracheal intubation has been confirmed with this technique the ETT lies at a safe distance from the carina and, thus, endobronchial intubation is prevented. Our results also indicate that placement of the ETT merely by using the reference marks on the side of the tube could result in a higher incidence of complications.
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