Efficacy of height-based formula to predict insertion depth of left-sided double lumen tube: A prospective observational study

Expert opinion on the use of fiberoptic bronchospe to check the insertion depth of the left-sided double-lumen tube

Left-sided double-lumen tube (LDLT) is commonly used to achieve one lung isolation in most thoracic surgical procedures. Traditionally, the LDLT is blindly placed using direct or video laryngoscopy. In this brief report, we highlight the importance of using our novel insertion depth formula to predict the appropriate LDLT insertion depth and demonstrate the current evidence supporting the efficacy of the formula. Also, we will discuss two relatively new devices of LDLTs: one with an embedded camera at the distal end of the tracheal lumen and the other with a carinal cuff between the bronchial cuff and the tracheal lumen in reducing the incidence of too deep inserted LDLT. We advocate that using our novel formula and these two new devices may reduce but not eliminate the need for FOB to check the insertion depth of LDLT.

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 tobe directly proportional to height and several height-based recommendations have beensuggested. This retrospective study was designed to find out the difference between calculated depths using height-based formulae and realistic depths in clinical practice of DLTplacement by analyzing pooled data from patients intubated with left-sided DLT.

METHODS

The electronic medical records of adults, intubated with DLT from February 2018to December 2020, were reviewed. Data retrieved included age, sex, height, weight, andsize and depth of DLT. The finally documented DLT depth (depth final, DF) was comparedwith 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 whendepths are calculated using height-based recommendations. Although such discrepanciesmay not be clinically meaningful, efforts are needed to standardize the methods of endobronchial intubation to prevent potential complications associated with malposition.

Double lumen tube: Size and insertion depth

Double lumen tubes (DLTs) are most commonly used to achieve one lung ventilation (OLV) in most thoracic surgical procedures unless contraindicated. Left-sided DLT (LDLT) is most commonly used nowadays for most thoracic surgical procedures. Though, the use of LDLT dates long back in history, two clinical and technical issues are yet to be resolved. The first issue is the ideal size of DLT which is defined as that which provides near-complete seal of the bronchial lumen without cuff inflation. There are no guidelines in literature which help in selecting the size of DLT. However, general consensus among thoracic anesthesiologists recommends the use of smaller sizes to avoid airway trauma. In our practice and for the last few years, we are using smaller size LDLT 35 F for females and 37 F for males with minimal airway trauma and had encouraging results. The second issue is the insertion depth of the LDLT. We have introduced a height-based formula to predict the insertion depth of LDLT with encouraging results. However, even with the use of the formula, we still recommend the use of fiberoptic bronchoscopic confirmation method for final positioning of the LDLT.