Abstract
The author measured the margin of safety (MS) in positioning disposable doublelumen endotracheal tubes (DLT) in Japanese adults. MS in posittoning left and right sided DLT was defined as the length of the left mainstem bronchus (LL) minus the length from the proximal margin of the left cuff to left lumen tip (DL), and the length of the right mainstem bronchus (LR) minus the length of the right cuff (DR), respectively, as being described by Benumof and others. Remaining negative value MS indicated it would not be possible to position DLT without some degree of upper lobe obstruction. The incidence of negative value MS was associated with the manufacturers and the size of DLT (27% at MAX). As DLT size decreased, however, MS did not increase except in some cases. Even if using DLT of the same manufacturer and same size, MS was different because of the variations of DL and DR Since the incidence of negative value MS in positioning right-sided DLT is greater than that in positioning left-sided DLT, left-sided DLT should be used whenever possible. Before intubating DLT, not only LL and LR but also DL or DR should be measured, and MS should be confirmed to be enough or not.
