Difficult Airway Algorithms


  • Difficult airway algorithms are useful for considering all the contingencies that may occur during intubation
  • All team members must be aware of all of the contingency plans
  • All intubation attempts should be considered potential difficult airways
  • Algorithms involve a step-wise approach using different techniques for difficult intubation and difficult ventilation


Techniques for difficult intubation

  • Alternative laryngoscope blades
  • Awake intubation (either video laryngoscope or fiberoptic scope)
  • Blind intubation (oral or nasal)
  • Fiberoptic intubation
  • Intubating stylet or tube changer (e.g. Cook catheter or bougie)
  • Laryngeal mask airway as an intubating conduit
  • Light wand
  • Retrograde intubation
  • Invasive airway access

Techniques for Difficult Ventilation

  • Esophageal tracheal Combitube
  • Intratracheal jet stylet
  • Laryngeal mask airway
  • Oral and nasopharyngeal airways
  • Rigid ventilating bronchoscope
  • Invasive airway access
  • Transtracheal jet ventilation
  • Two-person mask ventilation



Patient safety using RSI hinges on a redundancy of safety.

  • Can you intubate? If intubation fails, can you ventilate? Algorithm (above) focuses on the route of intubation and RSI decision.

The colored arrows are contraindications to RSI.

  • In cardiac arrest (blue box – patient apneic) muscle relaxants are not needed. When there is obvious oral pathology, or intrinsic laryngo-tracheal pathology (green boxes – patient breathing spontaneously), the redundancy of safety does not exist – avoid RSI.
  • When the mouth is blocked (step 2), intubate through the nose or through the neck (cricothyroidotomy). RSI is specifically done to optimize laryngoscopy conditions and permit oral intubation. If it is apparent that the oral route has obvious anatomic problems (not merely potential difficulty), RSI should never be considered.
  • When the oral route is impossible, intubation will need to take place through the nose or neck, and this should be done with the patient awake.
  • Examples include massive angioedema, advanced Lundwig’s angina, wired jaw, or readily apparent combinations of airway distortion, disproportion, and dysmobility (cervical spine and mandible), that preclude oral intubation. With intrinsic laryngeal pathology (step 3), safest approach is with the patient breathing spontaneously, using fiberoptic intubation, or a surgical airway (tracheotomy) below the level of the lesion.

At step 4, the decision to use RSI is a matter of judgment, not a strict contraindication.

  • The four Ds (distortion, disproportion, dysmobility, dentition) may make direct laryngoscopy with standard equipment impossible.
  • Is an “awake” approach feasible? Will you be able to rescue ventilate? How fast are intubation and patient control needed? What are the risks of delay vs. the potential risks of RSI?

After crossing the RSI line, patient safety often depends on first pass success at laryngoscopy, since many patients requiring emergent intubation have very short safe apneic periods.

  • Pre-oxygenation is only marginally effective in critically ill patients.


  • RSI vs. Awake – latter preferred if:
    • Less urgent intubation
    • More difficult airway features
    • Low risk of vomiting
  • Prepare for failure of intubation and failure of ventilation
    • Discuss plan A, B, C, D with team
    • Equipment for plan A, B, C, D at bedside
  • Airway attempt successful -> post-intubation management
  • Airway attempt unsuccessful, able to ventilate -> Plan B/C/D
    • change patient position
    • change blade
    • change modality (e.g. direct vs video laryngoscopy)
    • change proceduralist
  • Airway attempt unsuccessful, unable to ventilate -> supraglottic airway -> surgical airway if unsuccessful -> post-intubation management


Ron Wall’s algorithms from his Airway Course and Manual of Emergency Airway Management:



Algorithms from the Austin Hospital ED, Melbourne, courtesy of George Douros. Here’s the RSI pre-intubation checklist

Rapid sequence induction RSI checklist-GD
click to enlarge

Here’s the difficult airway action plan



Nicholas Chrimes and Peter Fritz have developed an algorithmic approach to airway management based on a cognitive aid called ‘The Vortex’


The Difficult Airway Society in the UK has comprehensive guidelines for airway management, including multiple algorithms.

  • The integrated algorithm can be downloaded here (pdf).
  • the Austin Hospital’s algoirthm by George Douros above, is a modified version of the DAS integrated algorithm – note that the option of waking the patient up has been removed for ‘out-of-theatre’ use!

References and Links

Journal articles

  • Apfelbaum JL, et al; American Society of Anesthesiologists Task Force on Management of the Difficult Airway. Practice guidelines for management of the difficult airway: an updated report by the American Society of Anesthesiologists Task Force on Management of the Difficult Airway. Anesthesiology. 2013 Feb;118(2):251-70. PMID: 23364566. [Free Full Text]
  • Henderson JJ, Popat MT, Latto IP, Pearce AC; Difficult Airway Society. Difficult Airway Society guidelines for management of the unanticipated difficult intubation. Anaesthesia. 2004 Jul;59(7):675-94. PMID: 15200543.

FOAM and web resources

CCC 700 6

Critical Care


Chris is an Intensivist and ECMO specialist at the Alfred ICU in Melbourne. He is also a Clinical Adjunct Associate Professor at Monash University. He is a co-founder of the Australia and New Zealand Clinician Educator Network (ANZCEN) and is the Lead for the ANZCEN Clinician Educator Incubator programme. He is on the Board of Directors for the Intensive Care Foundation and is a First Part Examiner for the College of Intensive Care Medicine. He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives.

After finishing his medical degree at the University of Auckland, he continued post-graduate training in New Zealand as well as Australia’s Northern Territory, Perth and Melbourne. He has completed fellowship training in both intensive care medicine and emergency medicine, as well as post-graduate training in biochemistry, clinical toxicology, clinical epidemiology, and health professional education.

He is actively involved in in using translational simulation to improve patient care and the design of processes and systems at Alfred Health. He coordinates the Alfred ICU’s education and simulation programmes and runs the unit’s education website, INTENSIVE.  He created the ‘Critically Ill Airway’ course and teaches on numerous courses around the world. He is one of the founders of the FOAM movement (Free Open-Access Medical education) and is co-creator of litfl.com, the RAGE podcast, the Resuscitology course, and the SMACC conference.

His one great achievement is being the father of three amazing children.

On Twitter, he is @precordialthump.

| INTENSIVE | RAGE | Resuscitology | SMACC

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