To the Editor:-In recent correspondence, [1,2]Professor Benumof suggested the need for a Table ofdifferent-sized endotracheal tubes (ETTs) and compatible-sized intraluminal guides and fiberoptic bronchoscopes (FOBs) to change a small-bore ETT to a large-bore ETT.
In practice, it is useful to remember that the combined diameter of the FOB and the intraluminal guide should be at least 1 mm less than the internal diameter (ID) of the ETT, so that the ETT can be slipped easily over the guide and FOB. The FOB with an external diameter (ED) of 4 mm and a guide with a similar ED can be used for 9.0 mm-ID ETT, whereas for a 8.0 mm-ID ETT, one would need a guide of 3 mm ED. An FOB with greater than 4.0 mm ED may also be used, but that would limit the size of the intraluminal guide. A smaller guide may also be more vulnerable to displacement.
Considering the availability of multiple sizes of FOBs and intraluminal guides by different manufacturers, a Table maynot serve its purpose of making the task easy, but confound the anesthesiologist with the problem of exchanging a small ETT.
Pramod Bapat, M.D., F.R.C.A., Visiting Fellow, Department of Anaesthetics, Harefield Hospital, Harefield, Middlesex UB9 6JH, United Kingdom.
(Accepted for publication December 6, 1996.)