New Imaging Protocol to Assess Endotracheal Tube Placement: A Case-control Study

After intubation, a frontal chest radiograph (CXR) is obtained to assess the endotracheal tube (ETT) position by measuring the ETT tip-to-carina distance. ETT tip location changes with neck position and can be determined by assessing the position of the mandible. As the mandible is typically not visualized on standard CXRs, we developed a new protocol where the mandible is seen on the CXR, hypothesizing that it will improve the accuracy of the ETT position assessment.

Two groups of intubated patients studied (February 9, 2021 to May 4, 2021): CXR taken in either standard or new protocol (visible mandible required). Two observers independently assessed the images for the neck position (neutral, flexed, and extended) based on the mandible position relative to the vertebral bodies. With the mandible absent (ie, neck position unknown), we established terms: "gray zone" (difficult to assess the ETT position adequately) and "clear zone" (confident recommendation to retract, advance, or maintain ETT position). We compared the rate of confident assessment of the ETT in the standard versus the new protocol.

Of 308 patients, 155 had standard CXRs and 153 had the new protocol. Interrater agreements for the distance between the ETT and the carina and mandible height based on vertebral bodies were 0.986 ( P < 0.001) and 0.955 ( P < 0.001), respectively. The mandible was visualized significantly more often ( P < 0.001) with the new protocol (92%; 141/153) than with the standard protocol (21%; 32/155). By visualizing the mandible or the presence of the ETT within the clear zone, a reader could confidently assess the ETT position more often using the new protocol (96.7% vs 51.6%, P < 0.001).

Mandible visibility on postintubation CXR is helpful for assessing the ETT position. The new protocol resulted in a significant increase in both visualizing the mandible and accurately determining ETT position on postintubation CXR.