Predictors of Difficult Intubation with Hypercurved Glidescope or C-MAC devices

by Joseph Esherick, M.D., FAAFP, FHM

Investigators have conducted a secondary analysis in order to identify predictors of difficult or prolonged intubation with hypercurved videolaryngoscopes. The analysis was of a randomized control trial of 1100 elective surgery patients. After anesthesia and neuromuscular blockade, these patients were intubated with either GlideScope or C-MAC D-blade video laryngoscopes.

More than one attempt or single successful attempt that lasted longer than 60 seconds was considered a difficult intubation. Intubation was reflected as difficult in 301 patients. A second attempt was required for 27 of those patients. In 244 patients the single attempt exceeded 60 seconds. Lastly, 30 of these patients experienced a difficult intubation due to both reasons.

Factors independently associated with difficult intubation


Odds ratio

Attending vs. resident


Reduced mouth opening


Cardiothoracic surgery vs. general surgery


Otolaryngologic surgery vs. general surgery


Sniffing position vs. neutral cervical spine position



Emergency physicians or hospital physicians using a hypercurved videolaryngoscope should should be familiar with its use to maximize intubation success and efficiency. In addition, patients should be placed in neutral cervical spine position as opposed to sniffing position.  I suspect the reason that attending physicians had more trouble with intubations compared with resident physicians is due to the infrequency with which they perform intubations


  1. Aziz MF et al. Predictors of difficult video laryngoscopy with either GlideScope® or C-MAC® with D-blade: Secondary analysis from a large comparative videolaryngoscopy trial. Br J Anaesth 2016 Jul; 117:118. (