Battle of the Blades: Part 3

Battle of the Blades: Part 3 690 539 Richie Cunningham

Part 3: Can we be competent at both?

As alluded to previously, direct laryngoscopy, standard-geometry or Macintosh (CMAC) video laryngoscopy, and hyperangulated (GlideScope) video laryngoscopy are all distinct devices, with distinct techniques, and (presumably) distinct learning curves.

The ACGME requires that emergency medicine residents perform 35 endotracheal intubations prior to graduation. It also says that critical care fellows must be able to perform intubation, but does not give a specific number of procedures needed for graduation (or competence for that matter).

Where does the ACGME get these numbers (or lack thereof)? Evidently not from the literature. The studies defining a learning curve for direct laryngoscopy are heterogeneous in their methods, settings, and definition of “competence.”  A systematic review performed in 2015 said that at least 50 intubations are needed to achieve a 90% success rate within two attempts in elective circumstances (1). Konrad et al in 1999 showed anesthesiology residents needed on average 57 intubation attempts to achieve a 90% success rate within two attempts, but 18% of residents still required assistance from an attending after 80 attempts (2). Bernhard et al showed that anesthesiology residents showed that first pass success steadily increased from 67% within the first 25 intubations to 83% after 200 intubations (3).

Taken together, we can conclude that 50 intubations is the bare minimum for competence at intubation via direct laryngoscopy, and that number is likely significantly higher for intubation outside the OR where hemodynamic instability, hypoxia, and airway contamination can all complicate manners. A national survey performed in 1999 of EM residencies showed that residents perform an average of 75 intubations during residency with a range from 13 to 180 (4). We can therefore conclude that it’s likely the average emergency physician won’t hit competence  with direct laryngoscopy until near the end of residency.

Hyperangulated video laryngoscopes require a separate technique than that with a Macintosh blade. The more trainees use these devices, the less they progress along the steep but prolonged learning curve of gaining competence with direct laryngoscopy. 

The good news is you can likely learn to use a GlideScope on a mannequin. Here’s why: a small study looked at 20 trainees who had never performed an intubation. They were trained with a Macintosh direct laryngoscope and hyperangulated GlideScope on mannequins until they could perform intubation successfully three times in a row with each device. They then attempted 10 intubations on real patients; 5 with DL and 5 with a GlideScope. Cumulatively, the GlideScope was successful 93% of the time compared to 51% with DL (5).

Why is this? I believe it is for two reasons: direct laryngoscopy is more difficult than video laryngoscopy in general (in my own anecdotal experience, though I’m sure many other EM residents and physicians would agree), and hyperangulated video laryngoscopy is easily learned on mannequins because it is a non-displacement laryngoscope. In order to perform the technique, alignment of the oral, pharyngeal, and laryngeal axes is not required to view the glottis with the camera, unlike with direct laryngoscopy. This minimizes the discrepancy between intubating a mannequin and a real patient. No tongue sweep is required, nor sniffing position, nor lifting up and away to displace the lingual, oropharyngeal, and submandibular tissues. Plastic mannequin “tissue” does not behave the way real human tissue does, and that’s why direct laryngoscopy (a displacement laryngoscope) is harder to learn on plastic airway models.

Take Home Points:

  1. At least 50 intubations are required to become “competent” at direct laryngoscopy in elective settings
  2. This number is likely higher for intubation under emergent conditions
  3. EM residents will often spend their entire residency gaining competency in direct laryngoscopy
  4. Hyperangulated video laryngoscopy can be learned on mannequins; learn direct laryngoscopy on real patients

Some may argue that because of this extensive learning curve, trying to develop and maintain the skill of direct laryngoscopy is a fool’s errand. In the next post, we’ll discuss whether or not video laryngoscopy (specifically with a hyperangulated blade) is a sufficient replacement for DL.

Read Part 4 here.


  1. Buis ML, Maissan IM, Hoeks SE, Klimek M, Stolker RJ. Defining the learning curve for endotracheal intubation using direct laryngoscopy: A systematic review. Resuscitation. 2016;99:63-71. doi:10.1016/j.resuscitation.2015.11.005
  2. Konrad C, Schüpfer G, Wietlisbach M, Gerber H. Learning manual skills in anesthesiology: Is there a recommended number of cases for anesthetic procedures?. Anesth Analg. 1998;86(3):635-639. doi:10.1097/00000539-199803000-00037
  3. Bernhard M, Mohr S, Weigand MA, Martin E, Walther A. Developing the skill of endotracheal intubation: implication for emergency medicine. Acta Anaesthesiol Scand. 2012;56(2):164-171. doi:10.1111/j.1399-6576.2011.02547.x
  4. Hayden SR, Panacek EA. Procedural competency in emergency medicine: the current range of resident experience. Acad Emerg Med. 1999;6(7):728–35.
  5. Nouruzi-Sedeh P, Schumann M, Groeben H. Laryngoscopy via Macintosh blade versus GlideScope: success rate and time for endotracheal intubation in untrained medical personnel. Anesthesiology. 2009;110(1):32-37. doi:10.1097/ALN.0b013e318190b6a7