Visualization of the vocal cords and end-tidal capnography are the usual standards in confirming endotracheal tube placement. Vocal cord visualization is, however, not always possible, and capnography is not 100% reliable and requires ventilation of the lungs to confirm placement. The goal of this study is to determine the accuracy of ultrasonography for detecting endotracheal tube placement into the trachea and esophagus in real time.
This was a prospective, randomized, controlled study. Eligible patients were adults undergoing elective surgery requiring intubation. Exclusion criteria were a history of difficult intubation, abnormal airway anatomy, aspiration risk factors, and esophageal disease. Thirty-three patients were enrolled. After induction of anesthesia and neuromuscular blockade, the anesthesiologist placed the endotracheal tube in the trachea and esophagus in random order with direct laryngoscopy. During the intubations, a high-frequency, linear transducer was placed transversely on the neck at the suprasternal notch. Two emergency physicians, blinded to the order and performance of the intubations, independently recorded the location of the endotracheal tube according to the real-time ultrasonographic image. A 2-by-2 table was used to calculate sensitivity and specificity of the emergency physicians' ability to detect placement of the endotracheal tube.
For each physician, the sensitivity for identifying the first intubation as tracheal was 100% (95% confidence interval [CI] 77% to 100%) with a specificity of 100% (95% CI 82% to 100%). One endotracheal tube was unintentionally placed twice in the esophagus, but both tube placements were identified as esophageal by the emergency physicians.
In this pilot study, 2 emergency physicians experienced in ultrasonography accurately detected placement of endotracheal tubes during intubation with ultrasonography in select patients in the controlled environment of the operating room. Future studies should examine the use of ultrasonography to visualize endotracheal tube placement in real time by emergency physicians with less ultrasonographic training; use of the technique in the emergency department on a wider range of patients, including patients with difficult airways; and assessment of the utility of ultrasonography in confirmation of endotracheal tube position in already intubated patients.