Predicting Optimal Insertion Depth of a Left-sided Double-Lumen Endobronchial Tube

Appropriate placement of the double-lumen endobronchial tube (DLT) is essential for one-lung ventilation. Several formulae based on body height (BH) have been used for estimating the optimal insertion depth of a left-sided DLT. In this study, the authors examined the following 5 formulae for accuracy of prediction: 0.11×BH+10.53 (cm) from Brodsky et al(1); 0.15×BH+3.96 (cm) from Bahk and Oh(2); 0.148×BH+3.8 (cm) from Chow et al;(3) 0.1×BH+12.5 (cm) from Takita et al(4); and 0.1977×BH - 4.2423 (cm) (authors' formula).

Single-center, retrospective, observational study.

University hospital.

Anesthetic records of patients older than 20 years who received one-lung ventilation using a left-sided DLT were included.

The patients' sex, age, body weight, BH, and the final correct insertion depth of the left-sided DLT after fiberscope verification were recorded. Linear regression and correlation were used to analyze the data.

One hundred seventy anesthetic records were analyzed. The insertion depth was distributed normally in 4 groups with different BH intervals. The correlations between the correct insertion depth and all the lengths calculated using each formula were significant (p<0.001), with a similar high coefficient of determination (r = 0.809). The regression line derived from the authors' formula-0.1977×BH - 4.2423 (cm)-showed the most accuracy in predicting the correct insertion depth.

The height-based formula of 170 - 29.5 - 5 - 1 (the insertion depth is 29.5 cm for patients who are 170 cm tall, and the insertion length is increased or decreased by 1 cm for every 5 cm increase or decrease in BH) modified by the equation of 0.1977×BH - 4.2423 is a useful tool to predict the optimal insertion depth in initially blind left-sided DLT insertion.