Background: Esophageal detector devices (EDDs) impose negative pressure on the trachea or esophagus to verify endotracheal tube (ETT) position. In cardiac arrest, the smooth muscle of the lower esophageal sphincter relaxes in a time-dependent and irreversible manner. If relaxation also occurs in the muscular posterior tracheal wall, it could predispose tracheal invagination or collapse with negative pressure, potentially yielding false-negative (tracheal ETT, EDD indicates esophagus) results. We compared 3 different EDDs in their ability to correctly discriminate tracheal and esophageal intubation.
Methods: ETTs were placed into the trachea and esophagus of 5 domestic swine, and bronchoscopy was used to visualize the trachea while 3 EDDs were tested. Tracheal wall activity was observed before and after induced cardiac arrest. Tracheal ETTs were aspirated with increasing negative force and pressures at initial wall movement and >50% tracheal lumen obliteration were recorded. Measurements were repeated at 4, 8, and 12 minutes postarrest and pressures at tracheal wall collapse pre- and postarrest were determined. EDDs were also tested on esophageal ETTs prearrest and at 6 and 10 minutes postarrest.
Results: In a closed system, each EDD generated more than -100 cm H(2)O pressure. Average prearrest pressure at tracheal collapse was -112 cm H(2)O. Average postarrest collapse pressures were -68, -66, and -54 cm H(2)O at 4, 8, and 12 minutes postarrest. One EDD consistently gave equivocal results; the remaining 2 gave accurate results in all subjects. Most observed movement was insufficient to cause device failure although tracheal wall movement was noted in all postarrest EDD trials. Esophageal intubation was correctly determined at all times pre- and postarrest.
Conclusion: These findings describe a mechanism for false-negative results from decreased posterior tracheal wall tone during cardiac arrest. Further studies are required to elucidate factors contributing to its occurrence and impact on EDD use.