Objective: To determine whether a certain distance measurement on the oral endotracheal tube (ETT) at the corner of the mouth could reasonably ensure proper depth of placement in critically ill patients, without the immediate need for a confirming chest x-ray (CXR).
Methods: A prospective observational cross-sectional design was used to compare ETT mark distance and radiographic location of the ETT tip. The measurement marking on the ETT at the level of the corner of the mouth was noted at the time of intubation. The relationship of the tip of the ETT to the tracheal carina on the postintubation CXR was then determined. The ETT placement was deemed correct if the tip was at least 2 cm cephalad to the carina on the CXR.
Results: Of 83 intubated patients assessed, 52 were men and 31 women. The mean measurement on the ETT at the corner of the mouth was 22.2 cm for the women and 23.1 cm for the men. The mean distance from the tip of the ETT to the carina was 3.45 cm for the women and 4.13 cm for the men. Seventy-five of the 83 patients (90.4%; 95% CI 81.9–95.7%) had correct ETT positions on the initial CXR. If the ETT position had been adjusted at the corner of the mouth to 21 cm for the women and 23 cm for the men, the ETT would have been in correct position for 81 of the 83 patients (97.6%; 95% CI 89.6–99.7%). This represents a significant improvement in tube placement (p < 0.025; the McNemar chi-square).
Conclusion: Proper depth of ETT placement in the critically ill adult patient can be estimated by the technique of this study. In this adult patient population, corner-of-the-mouth placement of the ETT using the 21-cm tube mark for the women and the 23-cm mark for the men would have led to proper placement for most patients.