Selecting Double-Lumen Tubes for Small Patients

Abstract

In Response: We would like to thank Brodsky et al. for their interest in and comments on our article [1]. We agree that the introduction of a 32F double-lumen tube (DLT) provides a much welcomed addition to the range of DLT sizes available for smaller patients, and their new guidelines, which included a 32F DLT, would be appropriately used for DLT selection. According to Brodsky et al.'s [2] recent guidelines, some of our patients, who received an oversized 35F DLT, may have been better fitted with a 32F DLT. However, contrary to their expectations, seven of our eight patients who received an oversized 35F DLT in our study had tracheal diameters of 14-15 mm. Only one patient had a tracheal diameter of 13.6 mm, and only that patient would have been selected to receive a 32F DLT by Brodsky et al.'s new guidelines. We believe that the key differences between our results and those of Brodsky et al. [2] lie both in the demographics of the population studied and is the definition of an oversized DLT. We took a conservative view with regard to the definition of a correctly sized DLT, compared with Brodsky et al., who accepted a DLT as appropriately sized based on clinical and functional grounds. For the purpose of the study, we regarded absence of air leak when the bronchial cuff was deflated as being oversized. We felt that this definition was important because a tube that fits too snugly into the airway can cause airway injury. We agree that airway rupture during placement of DLTs should be rare if done properly. However, pressure necrosis can occur with an overinflated cuff and can certainly occur with an oversized DLT that is wedged tightly into the airway. Lesser degrees of airway trauma, including petechiae and erosions, have been reported even after uneventful DLT placement and removal [3]. We agree that our Asian population differs from that of Brodsky et al.'s non-Asian shorter patients. However, a significant relationship between airway size and patient height has been reported in one other study group [4]. The reason and the magnitude to which body height should influence the predictive relationship between the tracheal and bronchial diameter is intriguing. Clearly, the latter would be a more important index. As Brodsky et al. have pointed out, the difference in outer diameters of the bronchial lumen varies very little among the DLT sizes. Hence, in selecting the appropriate DLT size, a means of directly measuring the left main bronchial width (such as computer tomographic scan measurements) more accurately than an indirect method of measuring tracheal width from the chest radiograph would be useful. However, in the absence of the availability of such a method, we agree that the tracheal width measurement (with some modification in short patients) would be a helpful guideline. Mark Y. H. Chow, MMed* B. L. Liam, MMed[dagger] Thomas W. K. Lew, MMed[dagger] R. Y. Chelliah, MMed[dagger] B. C. Ong, MMed* Departments of Anesthesia; *Singapore General Hospital [dagger]Tan Tock Seng Hospital; Singapore 169608