Park SY, et al. - Via this prospective study, researchers sought to determine the efficacy of transtracheal ultrasonography in confirming the placement of an endotracheal tube introducer during endotracheal intubation using the I-gel supraglottic airway as a guide. Among 106 patients with return of spontaneous circulation after I-gel insertion for out-of-hospital cardiac arrest, they performed endotracheal intubation using an endotracheal tube introducer through the I-gel. Transtracheal ultrasonography indicated artifacts of introducer in the trachea and esophagus in 80 (75.5%) and 26 (24.5%) patients, respectively. Observations support the accuracy of transtracheal ultrasonography for identifying introducer placement during endotracheal intubation using an endotracheal tube introducer through the I-gel.