Accuracy of ultrasound for endotracheal intubation between different transducer types

Introduction: Ultrasound has been increasingly utilized for the identification of endotracheal tube (ETT) location after an intubation attempt, particularly among patients in cardiac arrest. However, prior studies have varied with respect to the choice of transducer and no studies have directly compared the accuracy between transducer types. Our study is the first to directly compare the accuracy of ETT confirmation between the linear and curvilinear transducer. Methods: This study was performed in a cadaver lab using three different cadavers chosen to represent varying neck circumferences. Cadavers were randomized to tracheal or esophageal intubation. Blinded sonographers assessed the location of the ETT using either a linear or curvilinear transducer in an alternating sequence. Accuracy of sonographer identification, time to identification, and operator confidence were assessed. Results: Four hundred and five assessments were performed with 198 (48.9%) tracheal and 207 (51.1%) esophageal intubations. The linear transducer was 98% (95% CI 95.1% to 99.2%) accurate. The curvilinear transducer was 95% (95% CI 91.1% to 97.3%) accurate. The mean time to identification was significantly lower with the linear transducer [7.46 s (95% CI 6.23 to 8.7 s)] as compared with the curvilinear transducer [11.63 s (95% CI 9.05 to 14.2 s)]. The mean operator confidence was significantly higher with the linear transducer [4.84/5.0 (95% CI 4.76 to 4.91)] than with the curvilinear transducer [4.44/5.0 (95% CI 4.3 to 4.57)]. All operators preferred the linear transducer over the curvilinear transducer. Conclusion: The diagnostic accuracy of ultrasound for ETT confirmation did not significantly differ between ultrasound transducer types, but the curvilinear transducer was associated with a longer time to confirmation and lower operator confidence. Further studies are needed to determine if the accuracy would change with more novice providers or in specific patient populations.