A comparison of the forces exerted during laryngoscopy. The Macintosh versus the McCoy blade.

The forces exerted at laryngoscopy with the McCoy and Macintosh blades have been compared in 40 patients. The variables measured were the duration of laryngoscopy, the three maximally-applied forces and the mean force. The mean (SD) forces recorded were 18.9 (7.82) and 10.1 (5.33) N, respectively, with the Macintosh and the McCoy blades (p < 0.001) with a similar duration of laryngoscopy. There was a significant positive correlation between the mean force and patients' weight, height and body mass index for the Macintosh blade but only for weight and height for the McCoy blade. It is concluded that the use of the McCoy blade results in significantly less force being applied during laryngoscopy. This may be the reason for the reduction in the stress response reported previously with the use of the McCoy blade.