A comparison between the Macintosh and the McCoy laryngoscope blades.

The view of the larynx using the Macintosh laryngoscope and the McCoy levering laryngoscope was assessed in 177 adult patients. The view with the McCoy blade in the neutral position and in the position (neutral or elevated) that gave the 'best' view were recorded. The McCoy blade in the neutral position was associated with a lower incidence of grade 1 views and a higher incidence of grade 2 views than the Macintosh blade. There was no difference in the incidence of grade 3 views. When views for each patient using the different blades were compared, the McCoy blade in the neutral position produced a worse view than the Macintosh blade (p < 0.0001). The view obtained with the McCoy blade in its 'best' position and the Macintosh blade were similar. In the 152 patients in whom the vocal cords were seen using the Macintosh blade, the view was worse using the McCoy blade in its 'best' position more often than it was better (p = 0.06). In 25 patients, the vocal cords could not be seen with the Macintosh blade; in these patients the view was better with the McCoy blade (the cords were visible) on 14 occasions and worse in one (p = 0.001). We conclude that the McCoy blade in its neutral position does not behave identically to the Macintosh blade. The McCoy blade is a useful aid to difficult intubation but should not replace the Macintosh blade as the first choice laryngoscope.