PATIENTS requiring prolonged mechanical ventilation may need replacement of an endotracheal tube (ETT) for various reasons, including a cuff leak or a tube laceration. A common technique used is to change the ETT over a semirigid tube exchanger, also known as a bougie, or an airway exchange catheter (AEC). 1One problem with this technique is that it is difficult to confirm quickly and confidently the correct placement of the tube exchanger. If the old ETT is removed over a misplaced tube exchanger, airway control is threatened.
The anesthesia team was called to examine a 69-yr-old woman who remained intubated in the cardiac surgical intensive care unit 2 days after thoracoabdominal aortic aneurysm repair. A 7.5-mm Univent endotracheal tube (Fuji Systems, Tokyo, Japan) had been placed intraoperatively under direct laryngoscopy with “moderate” difficulty. The patient required postoperative mechanical ventilation secondary to slow neurologic recovery. She was sedated with continuous intravenous propofol. Muscle relaxants were not used. An oral bite block had not been placed, and the patient would occasionally bite the ETT. The respiratory therapist expressed concern about a cuff leak. Before our arrival, worsening arterial oxygen saturation had developed in the patient, and there was a discrepancy between inspiratory and expiratory tidal volumes. We performed fiberoptic bronchoscopy to confirm proper ETT placement and absence of mucous plugging. Attempts at reinflating the ETT cuff to prevent continued volume loss were unsuccessful. We elected to change the Univent tube to a standard single-lumen ETT. After bag–valve ventilation increased oxygen saturation measured by pulse oximetry (Spo2) to 100%, intravenous boluses of propofol and succinylcholine were administered. An 83-cm-long airway exchange catheter (Cook Critical Care, Bloomington, IN) was advanced with minor resistance. The Univent tube was withdrawn over the AEC until discovery of the exchange catheter exiting from a tear in the convex wall of the Univent tube at approximately 19 cm from the distal end (fig. 1). The ETT laceration had not been noted at the time of fiberoptic bronchoscopy. Because of the uncertainty of the location of the AEC, both the catheter and the Univent tube were withdrawn. Direct laryngoscopy was immediately performed, followed by successful oral tracheal intubation. Oxygenation and ventilatory parameters improved.
Anesthesiologists are frequently called on to perform endotracheal tube replacement. With this procedure, there is significant risk of losing control of the airway. Two separate but interrelated airway management issues are raised by this case report. The first issue is the patient biting the tube, which led to a complication. The second is that there was a failure of the AEC system.
There are numerous reports in the literature of complications related to ETTs being damaged by biting. 2,3These complications are separated into tube occlusion and tube laceration. Occluded tubes may lead to acute hypoxemia and hypoventilation, and negative-pressure pulmonary edema. Lacerated tubes can also lead to hypoxemia and hypoventilation, plus aspiration and inability to suction the trachea for secretions. Intraoral separation might be the most devastating, as in one case report of a 4-yr-old girl who bit the ETT after emergence from anesthesia; on extubation, the distal portion of the ETT remained below the glottis, causing airway obstruction. 2Particular to this situation are reports of the Univent tube being easily damaged. 4
To prevent biting the ETT, many authors advocate using some apparatus, such as an oropharyngeal airway, oral bite block, or roll of gauze in the mouth. 5,6However, these techniques are not foolproof because oral airways can soften and fail to prevent biting. 7Furthermore, oral airways compete with endotracheal tubes for a central position in the mouth, which can lead to dislodgment, pressure sores, or lip, tongue, and tooth trauma. 8,9Gauze packs are less traumatic but must be placed securely in the molars and packed with enough gauze to ensure a bite block effect. 5
The second issue raised is that as a result of the biting, the tube exchange system failed. Different methods to exchange ETTs have been used in the past. Initially, ETT exchangers were urethral or suction catheters, nasogastric tubes, or stylets. 10–12Creative mechanisms have been constructed to facilitate exchange from a double- to a single-lumen ETT. 13An AEC is a hollow, semirigid catheter that can be used to intubate, change endotracheal tubes, provide oxygen insufflation and jet ventilation, or be left in situ for “trial” extubation. 1,14,15However, these are not without risk because complications include the following: (1) misplacement, (2) tracheobronchial trauma or lung laceration, (3) jet ventilation–associated barotrauma and pneumothorax, and (4) laryngeal or vocal cord trauma from a new ETT “hanging up” during exchange. 16–19
In summary, biting of ETTs in nonparalyzed and sedated or lightly anesthetized patients is a potential problem and can lead to numerous complications if not recognized. Also, airway exchange catheters, although useful, are not foolproof, and misuse may be harmful. Potentially, combining AECs and fiberoptic bronchoscopy may prove to be the best method for safe endotracheal tube exchange. Anesthesiologists are reminded that they must have an algorithm available for extubation as well as intubation of the difficult airway. 20