Assessment of a new method to distinguish esophageal from tracheal intubation by measuring the endotracheal cuff pressure in a porcine model

Objectives: With the knowledge of differences in anatomic structures between the trachea and the esophagus, the authors conducted an animal study to evaluate the usefulness of endotracheal cuff pressure in distinguishing endotracheal and esophageal intubations. Methods: Six swine were anesthetized and endotracheally intubated with 7.5-mm cuffed endotracheal tubes. The intubations were confirmed by fiber-optic bronchoscopy. Each pilot balloon was connected to a 10-mL syringe and a manometer via a three-way stopcock. The cuff pressures were measured for each 1-mL incremental filling of air (1-10 mL). After removal of the endotracheal tubes, each swine was then intubated with the same endotracheal tubes into its esophagus. The cuff pressures of the esophageal intubation were measured with the same procedure. The cuff pressures and the pressure-volume relationships in both intubations were compared. Results: The cuff pressure increased significantly in the esophageal intubation in comparison with the endotracheal intubation in all the comparisons from 1 mL to 10 mL (p = 0.028 for all Wilcoxon signed-rank tests). The slope of the pressure-volume curve of the cuff pressure was also significantly higher in the esophageal intubation during the inflation of the cuff on average (0.047 vs. 0.032 cm H₂O/mL; p = 0.001), particularly in the first 5 mL of air inflation. Conclusions: The cuff pressure in the esophageal intubation was significantly higher than that in the endotracheal intubation under the same inflated volume from 1 to 10 mL. This may provide the basis for an adjunctive, simple, rapid, and reliable method to verify endotracheal intubation.