Category Archives: Airway Assessment

Difficult Face Mask Ventilation – ATOTW 321

The newest edition of the Anaesthesia Tutorial of the Week (ATOTW #321) covers the much underestimated but critically important topic of predicting and managing difficulty in face mask ventilation.  Irish anaesthetists Jonathan Holland and Will Donaldson have created a useful resource for anyone studying or performing airway management, or refreshing for exam purposes.

ATOTW is a free resource created and hosted by the World Federation of Societies of Anaesthesiologists.  You can sign up to receive the weekly mails here, and download this edition on mask ventilation here:

ATOTW 321 – Difficult Mask Ventilation

The authors discuss the predictors of difficult mask ventilation and report/propose another two mnemonics, to add to the existing stable (MOANS, BONES, etc):

Two mnemonics for prediction of difficult face mask ventilation
Two mnemonics for prediction of difficult face mask ventilation.  Source: ATOTW 321

I’ve always used MOANS for mask factors (like I use LEMON for laryngoscopy), but all these mnemonics cover the same ground.  MOANS, for instance, stands for

  • M   Mask seal factors, like beards, NGTs, odd shaped faces
  • O   Obesity and causes of Obstruction, like tumours/angioedema
  • A   Age extremes (the elderly and very young)
  • N   No teeth (or nasty dentition)
  • S   Snoring and Stiff lungs (the latter being issues like inhalation burns and acute bronchospasm, where the higher pressures required increase the risk of gastric insufflation and Splinting of the diaphragm)

As you can see, they are all much the same, although there are a few things that are not covered by every algorithm.  The purist would point out that obesity is defined as a BMI of >30 kg/m2, not 26 as stated in the table.

Hollan & Donaldson’s flowchart for management of difficult face mask ventilation. Source: ATOTW 321

The authors then present a useful flowchart for addressing unexpected difficulty, which is quite sensible.  It is much in line with the DAS guidelines and other algorithms for general airway difficulty, and useful for instruction.  Of course, in a dire emergency, using a cognitive aid such as the Vortex would be  effective.


Cormack-Lehane Grading Examples

Here are some real-life examples of Cormack-Lehane classification of laryngoscopic view taken with a video laryngoscope.  Although initially described for direct laryngoscopy in obstetric patients, it is a useful descriptive system in many settings, but is frequently misreported and/or misunderstood.  We will continue to expand the set as we collect good images.

Original and revised (Yentis & Lee, 1998) CL grading:

Click to access the paper in Anaesthesiology, 1998

Colour-coded to make it a little easier to read:

…and here from the CoPilot VL material, a more anatomically-correct sketch which shows the distinction between 2a and 2b clearly:

Cormack–Lehane 1:Cormack-Lehane 1

Cormack-Lehane 2a:Cormack-Lehane 2a

Cormack-Lehane 2b:2014.01.16_08.04.59 Cormack-Lehane 2b (nearly 3)

Cormack-Lehane 3:2014.02.03_10.21.59 Cormack-Lehane 3a

Cormack-Lehane 4:2013.09.20_11.19.39_tongue CL4

See the original article by RS Cormack and J Lehane in Anaesthesia, 1994;(39):1105-1111.

Various modifications to this scheme have been proposed for use with video laryngoscopy (VL), including suggestions by Cook and Fremantle: