Depth of double-lumen endobronchial tube: a comparison between real practice and clinical recommendations using height-based formulae

Background: The depth of double-lumen endobronchial tube (DLT) is reportedly known to be directly proportional to height and several height-based recommendations have been suggested. This retrospective study was designed to find out the difference between calculated depths using height-based formulae and realistic depths in clinical practice of DLT placement by analyzing pooled data from patients intubated with left-sided DLT. Methods: The electronic medical records of adults, intubated with DLT from February 2018 to December 2020, were reviewed. Data retrieved included age, sex, height, weight, and size and depth of DLT. The finally documented DLT depth (depth final, DF) was compared with the calculated depths, and the relationship between height and DF was also evaluated. A questionnaire on endobronchial intubation method was sent to anesthesiologists. Results: A total of 503 out of 575 electronic records of consecutive patients were analyzed. Although the relationship between height and DF was shown to have significant correlation (Spearman’s rho = 0.63, P < 0.001), DF was shown to be significantly greater than calculated depths (P < 0.001). Despite 57.1% of anesthesiologists have knowledge of clinical recommendations to anticipate size and depth of DLT, no one routinely utilizes those recommendations. Conclusions: Anesthesiologists tend to place DLTs in a deeper position than expected when depths are calculated using height-based recommendations. Although such discrepancies may not be clinically meaningful, efforts are needed to standardize the methods of endo-bronchial intubation to prevent potential complications associated with malposition.