Written by Thomas Davis, MD.
When intubating edentulous patients, using a smaller Macintosh curved blade (Mac 3 for men and Mac 2 for women) led to an improved glottic view.
Why does this matter?
Although you don’t need to worry about breaking a tooth when intubating edentulous patients, edentulism causes collapse of the oropharyngeal space. As patient anatomy changes, your optimal technique for intubating edentulous patients may also need to be modified. This study tests whether using a smaller Macintosh curved blade for direct laryngoscopy changes the glottic view. Remember, your first look is your best look.
No teeth? No problem.
This was an unblinded, cross-over trial of 35 patients intubated in the operating room by an individual board certified anesthesiologist. The anesthesiologist randomly crossed over between a Mac 4 and Mac 3 for edentulous men and a Mac 3 and Mac 2 for edentulous women. A digital photograph was taken at two points: when the tip of the blade was engaged in the valleculae and at the best laryngeal view. The percentage of glottic opening (POGO) score was then assessed. The average POGO score was significantly improved with the smaller-sized blade compared to the standard-sized blade (87% vs 71%, P<0.001, respectively).
Although the study is vulnerable to significant bias, it does propose a plausible mechanism to explain the improved view. As shown in the image below, the larger blade has to be rotated clockwise in order to adjust for a smaller portion of the blade being inserted into the oropharynx. As a result, the angle A2 in the photo was significantly more acute in the standard-sized blade than in the smaller-sized blade (35% vs 45%, p<0.001, respectively).
Effect of the Macintosh curved blade size on direct laryngoscopic view in edentulous patients. Am J Emerg Med. 2017 Sep 28. pii: S0735-6757(17)30793-3. doi: 10.1016/j.ajem.2017.09.050. [Epub ahead of print]
Peer reviewed by Alex Chen, MD and Clay Smith, MD.