Comparison of a colorimetric end-tidal CO2 detector and an esophageal aspiration device for verifying endotracheal tube placement in the prehospital setting: a six-month experience

R J Schaller, J S Huff, A Zahn
Prehospital and Disaster Medicine 1997, 12 (1): 57-63

INTRODUCTION: Hand held, colorimetric, end-tidal CO2 detector devices are being used to verify correct endotracheal tube (ETT) placement. The accuracy of these devices has been questioned in situations of cardiac arrest. The use of the esophageal detector device (EDD) is an easy alternative for detection of ETT placement, and may be more accurate in situations of cardiac arrest.

HYPOTHESIS: The use of the esophageal aspiration device in comparison with a colorimetric end-tidal CO2 detector is more accurate in detecting proper ETT placement and easier to use in the prehospital setting than is the colorimetric end-tidal CO2 detection device.

METHODS: This was prospective alternating weeks, 6-month study in a prehospital setting. Participants included all patients older than 18 years who were intubated by the Portsmouth, Virginia Emergency Medical Services (EMS) personnel from 01 July 1993 through 31 December 1993. The aspiration device used, also known as an esophageal detector device (EDD), was a 60 ml, luer-lock syringe attached to a 15 mm ETT adapter. Its efficacy was compared with an already accepted method of ETT position detection, the colorimetric end-tidal CO2 detector. Each device was used on alternating weeks, and correct ETT placement was determined by the receiving emergency department physician using standard techniques. Chi-square analysis and Fisher's Exact test were used to compare parameters, time of device use, and ease of use. Sensitivity and specificity were calculated, and provider preference was assessed using a survey instrument administered following completion of the study.

RESULTS: There were 49 patients who met the inclusion criteria, but six were excluded because of situational circumstances rendering use of the device a possible compromise of patient care. Twenty-five patients were in the EDD group, and 18 were in the end-tidal CO2 detector group. There was no statistically significant difference detected between groups for the gender ratio, underlying condition, CPR in progress, perceived difficulty of intubation, or percentage of nasotracheal intubation. The EDD was significantly easier to use (p < 0.005). There was no statistically significant difference in time required for use of end-tidal CO2 detector device versus the EDD. The sensitivity and specificity for correct tracheal placement using the EDD was 100%, and the sensitivity for correct tracheal placement using the end-tidal CO2 detector device was 78%. Use of the EDD was preferred over use of the end-tidal CO2 detector device by 75% of participating EMS providers. One case of nasotracheal intubation with an ETT placement above the cords raised the question of accuracy of this device in situations where direct visualization is not utilized.

CONCLUSION: The EDD was accurate in all cases of orotracheal intubation, and was easier to use than was end-tidal CO2 detector device. It was preferred by 75% of participating EMS providers. In cases in which the ETT may be above the vocal cords, caution must be used with interpreting the results obtained by use of the EDD.

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