Verification of endotracheal tube placement using electrical stimulation through electrodes placed on the endotracheal tube cuff.

Abstract

Current methods for verification of endotracheal intubation can fail, particularly in emergency settings. We investigated whether a verification method using electrical stimulation through electrodes placed on the endotracheal tube cuff could distinguish endotracheal and esophageal intubations in an experimental setting. During three sequential sessions simulating emergency intubation without paralysis, rapid sequence intubation (RSI) with neuromuscular blockade, and intubation during cardiopulmonary resuscitation, eight pigs were intubated with an endotracheal tube fitted with two electrodes exposed on the cuff of the tube, first in the esophagus and next in the trachea or in reverse sequence. Cuff pressure was monitored during a 5-s electrical stimulation (20 mA, 80 Hz, 500 μs), and delta pressure was calculated as the difference between baseline cuff pressure and maximum cuff pressure during the electrical stimulation. Delta pressure was significantly higher in esophageal than in tracheal placements in all three sequential sessions (86.0 [78.3-89.7] vs. 6.5 [2.0-7.9] mmHg, P = 0.001; 16.6 [13.2-22.8] vs. 0.8 [0.3-2.6] mmHg, P = 0.004; 66.1 [60.0-84.7] vs. 2.7 [0.7-9.7] mmHg, P = 0.001). The delta pressure did not overlap between tracheal and esophageal intubations except for the session simulating RSI with neuromuscular blockade, in which one of eight esophageal placements showed a delta pressure within the delta pressure range of tracheal placements. Electrical stimulation through electrodes placed on the endotracheal tube cuff produced remarkably greater increases in cuff pressure in esophageal intubations than in tracheal intubations in an experimental setting.