Letters to the Editor: Letters & Announcements
We appreciate the questions raised by Dr. El-Orbany (1) about our recent comparison of Flexiblade™ and Macintosh laryngoscopes (2). A number of novel modifications to the classic Macintosh laryngoscope have been developed to help improve laryngeal visualization, and therefore, facilitate intubation. The McCoy™ and Flexiblade are examples. Such devices can be used in the same manner as a Macintosh but may be easily and rapidly activated if required. Our study was designed to determine the utility of the Flexiblade in comparison to what most would consider the normal standard: a Macintosh blade. The design of the Flexiblade is such that one would not expect it to be any better than the Macintosh in its unactivated state, and our study clearly showed that it was not as good. However, such a comparison is not relevant to its design. It is important to clearly distinguish a comparison made with the Macintosh when the lever is activated (i.e., its functional state) and when it is not activated, and not to mix the analyses.
The main message from our study is that when the Flexiblade lever was activated, 39.6% of non-Grade I views that had been obtained using a Macintosh blade were improved, and activating the Flexiblade lever never caused a deterioration of view. As well as being statistically significant, most people would consider this to be strongly clinically significant during a critical clinical procedure.
In response to the other points raised, additional aids to accomplish tracheal intubation were only used after laryngoscope views had been recorded, as clearly stated in the text. They were used with a similar frequency in both groups. This, however, does not undermine the clinical significance of our findings, as such maneuvers are often used to further improve laryngeal visualization. Blinding is, of course, impossible in such a study and in any unblinded study there is a potential for bias. In this regard we would like to reassure Dr. El-Orbany that we did whatever we felt was possible to reduce bias (e.g., randomizing the order of laryngoscope use so as to minimize the effect of fatigue in the performance of the operator and having the same person performing laryngoscopy). Additionally, none of the authors had any vested interest in the outcome of this investigation.
Michael Irwin, MD, FRCA
Rochelle Cheung, MB, BS, FHKCA
Department of Anaesthesiology
University of Hong Kong
1. El-Orbany M. Laryngeal exposure using the Flexiblade ™ laryngoscope. Anesth Analg 2006;103:
2. Cheung RW, Irwin MG, Law BC, Chan CK. A clinical comparison of the Flexiblade™ and Macintosh laryngoscopes for laryngeal exposure in anesthetized adults. Anesth Analg 2006;102:626–30.