The McCoy Laryngoscope, External Laryngeal Pressure, and Their Combined Use

Abstract

The efficacy of the McCoy laryngoscope, external laryngeal pressure, and their combination to improve the laryngoscopic view was evaluated in 219 patients and compared with the Macintosh laryngoscope. An experienced laryngoscopist performed laryngoscopy twice using the Macintosh laryngoscope and the McCoy laryngoscope in a random sequence, and external laryngeal pressure was applied in each laryngoscopy with the laryngoscopist's right hand. The laryngoscopic view obtained was graded on our modified Cormack's method. Without external laryngeal pressure, the McCoy laryngoscope provided a better laryngoscopic view than that obtained by the Macintosh laryngoscope (P<0.001, signed rank test), but the view was worse than that with the Macintosh laryngoscope under external laryngeal pressure (P<0.001). The McCoy laryngoscope combined with external laryngeal pressure provided a better view than the Macintosh laryngoscope with external laryngeal pressure (P<0.001).

Optimal external laryngeal manipulation versus McCoy blade in active position in patients with poor view of glottis on direct laryngoscopy

“…This was consistent with the finding of an earlier study by Harioka et al , in which the addition of external laryngeal pressure to the Macintosh laryngoscope made the distribution of the laryngoscopic view better than that obtained by the McCoy laryngoscope with the tip in the elevated position. [9]…”

“…[1] McCoy and Mirakhur reported a modification of the Macintosh blade, popularly known as the McCoy blade, which could aide in improving the view of glottis during direct laryngoscopy. [2] Previous reports have shown that McCoy blade[3–8] as well as OELM[19] are effective in cases of difficult intubation. This study was undertaken to find out whether one of these techniques is better than the other, in patients with poor view of glottis, and to identify specific airway parameters that may influence the success of either technique.…”

The Evolution of Upper Airway Retraction: New and Old Laryngoscope Blades

“…33,86,168 Subsequent prospective series have 545 confirmed the CLM's utility in some difficult situations as well as confirming clinical suspicions that its use in otherwise easy situations may in fact worsen the view. 34,40,74,166 In most 34,137,166 but not all 74 studies, the CLM blade has failed to meaningfully improve Cormack grade 4 views. 34,40,74,137,166 In this population presenting with a grade 3 view, the view rarely worsens with blade tip activation.…”

“…Although one report documented a 66% improvement in laryngoscopic view in 38 Cormack grade 2 (arytenoids only) patients, the same report revealed a 22% overall incidence of worsening of the view obtained with tip activation, all in patients in Cormack grades 1 and 2. 40,74,137,166 Two studies have documented that the improvement in laryngoscopic view obtained with tip activation of the CLM is less than that obtained simply with external laryngeal pressure, 74,137 although application of both external laryngeal pressure and tip activation has an additive effect. With no potential for further upward travel, blade tip activation instead forces the midportion of the blade downward and into the direct line of sight, thus potentially obscuring the view ( Fig.…”

“…166 One explanation for this effect may be that in easy laryngoscopy situations, the blade tip easily engages and can lift the hyoepiglottic ligament and hyoid bone at the appropriate angle. 74 McCoy and colleagues 119 found that force incurred when using the levering tip blade was significantly less than that needed to visualize the larynx with the Macintosh blade. 23-30).…”