Disposable C-MAC(®) - not the same but same enough.

Abstract

We read with interest the letter by Greenland, expressing the view that the disposable C-MAC® videolaryngoscope blade (Karl Storz, Tuttlingen, Germany) was not the same as the re-usable blade, and thought we might share our experience of the disposable blade 1. Anaesthetists are becoming more skillful with the technique of videolaryngoscopy and it could soon become standard procedure for patients with a known or suspected difficult airway 2, particularly given the risk of transmission of infection between patients when re-using blades 3. The challenge remains to reproduce the same quality of equipment, but using different materials. We agree that the blade is not the same as the re-usable one but disagree with a few of the comments made by Greenland. Firstly, the comment made regarding the need for a more thickened plastic version of the blade to avoid breakage has been supported by a reference for a completely different product, the GlideScope® (GVL®, Verathon, USA), which uses a different polymer with a different tensile strength. Greenland notes a ‘marked thickening’ of the plastic version, but no measurements are given. We have examined the dimensions of MAC-3 and -4 disposable blades, but have found these to be only 2.4 and 2.8 mm thicker at the outlet than the equivalent metal blade. Furthermore, any harmful effect of a thicker blade is likely to be trivial once a comparatively much larger tracheal tube is passed. Incorrect use of the equipment is far more likely to cause airway trauma than any minor variation in dimensions 4. Greenland's comments about a ‘blind spot’ apply equally to the metal re-usable version. In difficult airway scenarios, an indirect monitor image is used rather than a direct view on the monitor, so any concern about a blind spot lacks clinical significance. We think the disposable C-MAC blade adequately reproduces the qualities of a re-usable blade and we support its continued use. We agree with Greenland that the disposable is not the same as the re-usable blade, but in our experience, it's the same enough.