Insertion Depth of Left-sided Double-lumen Tube: a New Predictive Formula

Efficacy of Height-Based Formula to Predict Insertion Depth of Left-Sided Double Lumen Tube. A Prospective Observational Study

The authors developed a formula for predicting the accurate depth of DLT insertion into the appropriate bronchus based on height as follows [The predicted insertion depth of left DLT (cm) equals 0.249 × (BH)0.916] [R]. That pilot study showed comparable correlations between five formulae [Brodsky et al, Bahk and Oh R, Takita et al, Chow et al, Lin]. However, that formula developed has not been validated yet.

We hypothesized that previously published formula would predict the accurate depth of left-sided DLT insertion. We aimed to investigate the efficacy of this formula to estimate the optimum insertion depth of the DLT using a flexible bronchoscope and decrease the incidence of DLT displacement into the appropriate bronchus, the need for bronchoscopic adjustment, and complications including soreness of throat and mucosal injury.

Accurate placement of the double-lumen tube [DLT], the commonly used tool to provide one-lung ventilation during thoracic surgery, is a real challenge for the thoracic anesthesiologists. Optimal DLT depth, defined as the blue endobronchial cuff below the carina, would decrease the incidence of obstructing the trachea and the contralateral bronchus (Brodsky). Additionally, deep insertion of the bronchial cuff of the DLT would obstruct the upper lobe bronchus (Brodsky). The careful adjustment of the depth and optimal positioning of the DLT using a flexible fiberoptic bronchoscope need a skilled anesthesiologist to reduce the time to DLT intubation. (Charles D. Boucek et al)

There are several methods have been described to predict the proper depth of DLT insertion. Chow et al. documented the validity of the developed formula based on the clavicular-to-carinal distance of trachea and height in 78% of patients studied. Brodsky et al. demonstrated that a height-and-gender-based formula could predict the depth of DLT insertion. Liu et al. reported an accurate depth of DLT insertion in 90% of patients studied measuring the distance between the vocal cord and carina according to the chest CT.

Inclusion Criteria:

• Underwent thoracic surgery
• Using a left-sided double-lumen tube for one-lung ventilation

Exclusion Criteria:

• Anticipated or known difficult airway
• Refuse to sign the consent
• Withdraw the consent