Force of Endotracheal Tube Extubation; Esophagus vs. Trachea; an Exploratory Crossover Clinical Trial

Correct endotracheal tube (ETT) placement is important. Ideal ETT position is achieved when the distal tip is in mid-trachea with the head in neutral alignment. Unrecognized tube misplacement is an uncommon but significant cause of hypoxemia and death during general anesthesia and emergency intubation of critically ill patients. It is commoner in out-of-hospital intubations, where it is reported to occur in 1 to 15% of cases, often with disastrous results. 1, 2 Three types of malpositioning can occur: one outside the trachea (esophageal), and two within the trachea: too shallow (hypopharyngeal), or too deep (endobronchial). Esophageal intubation results in rapid hypoxemia, hypercarbia, and inflation of the stomach as the patient receives no ventilation at all. 3 Too-shallow placement of the ETT can result in inadvertent extubation, especially with manipulation of head and neck. 4 Endobronchial intubation occurs when the ETT is advanced into a mainstem bronchus, which results in hypoxia and the potential for barotrauma in the hyperventilated lung. 5, 6 Confirmation of correct ETT depth is currently performed by several methods. In the operating room, simple measurement of the length of the tube at the corner of the mouth is rapid but not reliable. One study improved on this by using additional anatomical landmarks to determine ETT tube length as measured at the mouth.7 It enabled a reduction in the incidence of too-deep placement of the ETT from 58.8% to 24%.

Cuff ballottement at the level of the suprasternal notch is a technique that has been studied with cuffed tubes in adults. Ballottement as described in these papers involves moving the fingers in a direction normal to the long axis of the ETT in order to alternately compress and release the finger pressure on the cuff, while feeling and watching the corresponding movement of the pilot balloon. Ease of palpation of ballottement was inconsistent, and in one study 15 of 82 patients had ETT tips <2.5 cm above the carina. 8-10 Studies to date of ballottement do not comment on its ability to prevent esophageal intubation. Ultrasound guided intubation has been shown to provide correct placement, but requires training and machine availability. 11-14 We proposed to refine methods of palpating the trachea that we studied in previous experiments. We found that palpation of the anterior trachea with the fingertips during intubation enabled us to feel the tip of the endotracheal tube sliding into the trachea and improve correct depth compared to measurement at the teeth. 15 That study was undertaken to determine whether palpation of the trachea could enable correct position of the endotracheal tube with respect to depth. Esophageal intubation was studied subsequently, but the study was stopped when it became clear that we could not determine esophageal intubation by anterior tracheal palpation (unpublished).

However, during two instances of inadvertent esophageal intubation, we accidentally discovered a technique that may be able to detect inadvertent esophageal intubation as well as ensure correct endotracheal tube depth. Following tracheal intubation, with the cuff inflated to 50cm water pressure in the trachea, there was a sudden marked increase in the force necessary to gently tug the endotracheal tube proximally as the inflated cuff impinges on the rigid, encircling cricoid cartilage. When the increased force is sensed, then pushing the ETT down 2cm will ensure it is correctly positioned. If the cuff is in the esophagus, it will slide out without the sudden increased force being felt.

We plan a clinical pilot study of intubation of esophagus versus trachea with initial intubation of the esophagus flowed by intubation of the trachea.

Hypotheses. The force required for esophageal extubation with cuff inflated will be that required for tracheal extubation.