Diagnostic accuracy of ultrasound to confirm endotracheal tube depth

Endotracheal intubation is commonly performed in the Emergency Department. Traditional measures for estimating and confirming the endotracheal tube (ETT) depth may be inaccurate or lead to delayed recognition. Ultrasound may offer a rapid tool to confirm ETT depth at the bedside.

This was a randomized trial assessing the diagnostic accuracy of ultrasound to confirm ETT depth. Three cadavers were intubated in a random sequence with the ETT placed high (directly below the vocal cords), middle (2 cm above the carina), or deep (ETT at the carina). Seven blinded sonographers assessed the depth of the ETT using ultrasound. Outcomes included diagnostic accuracy of sonographer identification, time to identification, and operator confidence based upon ETT location. A subgroup analysis was performed to assess diagnostic accuracy by operator confidence.

441 total assessments were performed (154 high, 154 middle, and 133 deep ETT placements). Overall accuracy was 84.8% (95% CI 81.1% to 88.0%). When placed high, ultrasound was 82.5% sensitive (95% CI 75.5% to 88.1%) and 92.3% specific (95% CI 88.6% to 95.1%) with a mean time to identification of 15.3 s (95% CI 13.6-17.0) and a mean operator confidence of 3.9/5.0 (95% CI 3.7-4.1). When the ETT was placed in the middle, ultrasound was 83.8% sensitive (95% CI 77.0% to 89.2%) and 92.3% specific (95% CI 88.6% to 95.1%) with a mean time to identification of 16.7 s (95% CI 14.6-18.8) and a mean operator confidence of 3.7/5.0 (95% CI 3.5-3.9). When the ETT was placed deep, ultrasound was 88.0% sensitive (95% CI 81.2% to 93.0%) and 92.2% specific (95% CI 88.6% to 94.6%) with a mean time to identification of 19.0 s (95% CI 17.3-20.7) and a mean operator confidence of 3.4/5.0 (95% CI 3.2-3.6). Sonographers were significantly more accurate when they reported a higher confidence score.

Ultrasound was moderately accurate for identifying the ETT location in a cadaveric model and was more accurate when sonographers felt confident with their visualization. Future research should determine the accuracy of combining transtracheal ultrasound with lung sliding and other modifications to improve the accuracy.