title: Negative intratracheal pressure produced by esophageal detector devices causes tracheal wall collapse in a porcine cardiac arrest model.
abstract: 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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Anesthesiology and Post-Anesthesia Care, Naval Medical Center, San Diego, CA 92134-1005, USA.
authors.forename: Jason R
authors.initials: JR
authors.lastname: Schuh
authors.forename: Robert
authors.initials: R
authors.lastname: Bettendorf
authors.forename: David
authors.initials: D
authors.lastname: Shapiro
authors.forename: David L
authors.initials: DL
authors.lastname: Trowbridge
authors.forename: Eugenio
authors.initials: E
authors.lastname: Lujan
authors.forename: Patrick
authors.initials: P
authors.lastname: Boyle
authors.forename: Sean
authors.initials: S
authors.lastname: Birmingham
authors.forename: Rhodel
authors.initials: R
authors.lastname: Dacanay
authors.forename: Richard
authors.initials: R
authors.lastname: Green
mesh_terms: D000818:Animals; D001999:Bronchoscopy; D015505:Chest Tubes; D004195:Disease Models, Animal; D004867:Equipment Design; D004868:Equipment Failure; D019544:Equipment Failure Analysis; D004947:Esophagus / Q000503:physiopathology*; D006323:Heart Arrest / Q000503:physiopathology*; D007442:Intubation, Intratracheal / Q000009:adverse effects / Q000295:instrumentation*; D008422:Materials Testing; D009126:Muscle Relaxation; D011237:Predictive Value of Tests; D011312:Pressure; D034421:Sus scrofa; D013997:Time Factors; D014132:Trachea / Q000503:physiopathology*