We sought to determine whether gastric distention from air insufflation affects the accuracy of the Toomey syringe in detecting esophageal intubation. We conducted a randomized, single-blinded, crossover trial using human cadavers in which cuffed endotracheal (ET) tubes were placed into the esophagus and trachea. Operators used the Toomey syringe to determine the location of the ET tube before and after gastric insufflation via Ambu-bag ventilation. Greater amounts of air were aspirated (35.4 cc vs. 13.7 cc, respectively, p < 0.001) and less resistance was noted on a five-point scale (3.2 vs. 4.8, respectively, p < 0.001) from esophageally placed ET tubes after gastric insufflation. Sensitivity in detecting esophageally placed ET tubes decreased from 100% in noninsufflated cadavers to only 58% after gastric insufflation (p < 0.001). In the thawed fresh frozen cadaveric model, the Toomey syringe was unreliable in detecting an esophageal intubation after gastric distention insufflation.