The Emergency Department frequently uses endotracheal intubation. The endotracheal tube (ETT) depth might be inaccurately estimated and confirmed using conventional methods, which can cause a delay in detection. At the bedside, ultrasound may provide a quick tool for confirming ETT depth.
The randomized experiment evaluated the ultrasound’s ability to confirm ETT depth. The ETT was positioned high (just beneath the vocal cords), middle (2 cm above the carina), or deep (ETT at the carina) on 3 cadavers in random order. Using ultrasonography, 7 sonographers who were blinded evaluated the ETT’s depth. Results included operator confidence based on ETT location, time to identification, and diagnostic accuracy of sonographer identification. To determine operator confidence’s impact on diagnostic accuracy, a subgroup study was conducted.
There were 441 evaluations in all (154 high, 154 middle, and 133 deep ETT placements). The overall accuracy was 84.8% (95% CI 81.1% to 88.0%) and 92.3% specific (95% CI 88.6% to 95.1%). When used high, ultrasonography had a mean time to identification of 15.3 seconds (95% CI 13.6-17.0) and a mean operator confidence of 3.9/5.0 (95% CI 3.7-4.1), making it 82.5% sensitive (95% CI 75.5% to 88.1%) and 92.3% specific (95% CI 88.6% to 95.1%). 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). When sonographers reported a greater confidence level, their accuracy increased dramatically.
In a cadaveric model, ultrasound was somewhat reliable for locating the ETT, and it was more accurate when the sonographers were confident in their vision. Future studies should examine the accuracy of lung sliding and transtracheal ultrasonography combined with additional improvements.