Study objectives:To confirm the ability of the esophageal detector device (EDD) to indicate positioning of endotracheal tubes (ETTs) in patients intubated under emergency conditions and to compare the performance of the EDD with that of endtidal carbon dioxide (ETco(2)). Methods: This single-subject study comprising a prospective case series was conducted in the emergency department of an urban university hospital. All adult patients were intubated either in the ED or by paramedics in the field. ETT position was initially evaluated by means of auscultation, then EDD, and, finally, spectrographic qualitative ETco(2) monitoring in each patient. Discrepancies between the EDD and ETco(2) results were resolved by means of direct laryngoscopy. Results: In 100 intubated patients, both the EDD and ETco(2) monitoring detected the single esophageal intubation that occurred. Of the remaining 99 tracheal intubations, the EDD correctly indicated tracheal placement in 98 (sensitivity, 99%) and was indeterminate in 1 case because of blockage of the Err by secretions resulting from pulmonary edema. By comparison, ETco(2) monitoring correctly indicated tracheal placement in 86 cases (sensitivity, 87%) and was incorrect in 13 cases (P<.01). ETco(2) monitoring failed in 2 patients with pulmonary edema and in 11 patients with cardiac arrest. Among the 37 patients in the cardiac arrest group. the EDD correctly indicated ETT placement in 37 patients (sensitivity, 100%). In contrast, ETco(2) monitoring correctly indicated ETT placement in 26 patients (sensitivity, 70%; P<.01). Conclusion: The EDD reliably confirms tracheal intubation in the emergency patient population. The EDD is more accurate than ETco(2) monitoring in the overall emergency patient population because of its greater accuracy in cardiac arrest patients.