To the Editor:-Topf and Eclaveal endorsed the use of a endotracheal tube exchanger for the extubation of the difficult airway. They advocated several criteria to confirm the correct positioning of a tube exchanger. These included a normal capnographic tracing from the distal tip, audible breath sounds from the tubing, the inability to speak clearly, and an eventual chest radiograph. It has been my experience, using a similar tube exchanger (Endotracheal Ventilation Catheter [ETVC], CardioMed Supplies, Gormley, ON) that a normal capnographic tracing can occur with hypopharyngeal placement, and near-normal speech is generally observed despite tracheal placement.
I concur with their recommendation that the tube exchanger should remain in the trachea until postextubation airway competency is assured. In my experience, using the ETVC, it has been possible to achieve this, in virtually all patients, without the instillation of local anesthetics. In a report of the first 202 patients extubated over an ETVC, all but five patients tolerated this without a need for topical anesthesia. In three patients, the device had been left in situ for 48–72 hs.  It is possible that this reflects differences in the properties of different tube exchangers. If for example, the ETVC became excessively pliable as a result of being warmed by body temperature, it might prove less effective as a reintubation stylet. Nonetheless, the ETVC has proven itself to be reliable in this regard.  Avoidance of local anesthetics in the airway offers the advantage of preserving protective reflexes against aspiration, particularly during the vulnerable postextubation period when laryngeal incompetence and decreased airway reflexes may exist. .
Although the ETVC has generally been well tolerated, it is recommended that this device not be used in areas where it may be mistaken for a oro- or nasogastric tube.
Richard M. Cooper, B.Sc., M.Sc., M.D., F.R.C.P.C.
University of Toronto; Department of Anaesthesia; The Mount Sinai Hospital and the Toronto Hospital; University Avenue, Suite 1515; Toronto, ONT, Canada M5G 1X5
(Accepted for publication April 25, 1997.)