A comparison of 20 laryngoscope blades using an intubating manikin: visual analogue scores and forces exerted during laryngoscopy.

Fifty anaesthetists were recruited to use 20 different laryngoscope blades (one metal re-usable blade, five metal single-use blades and 14 plastic single-use blades, of which eight were bulb-type and 12 were fibreoptic-type) in a manikin to achieve a grade I Cormack and Lehane view. The anaesthetists were asked to provide visual analogue scores (VAS) for: ease of attachment of the blade to the handle; illumination; view of the larynx; and satisfaction for clinical use. The peak force applied and time to achieve the grade I Cormack and Lehane view were also measured. A cluster analysis method was used to group together blades with similar scores or measures. Ease of attachment, illumination, view, clinical use, force and duration were all significantly affected by the blade used (p < 0.0001 for all six). The mean peak force applied and mean duration for the 20 blades were 32-39 N and 4.4-9.5 s, respectively. All five metal single-use and four plastic single-use blades were always placed in the 'best' group in the cluster analysis. Two plastic blades provided a poor view and increased the duration of laryngoscopy.