Difficult Airway Assessment

Evidence-based predictors and management strategies

Clinical Predictors of Difficult Airway

Identifying patients at risk for difficult airway management is essential for safe anesthesia practice. The following validated clinical predictors help assess risk:

  • Mallampati Classification (Class III-IV) - Limited view of pharyngeal structures correlates with difficult laryngoscopy.
  • Thyromental Distance < 6 cm - Reduced distance limits laryngoscope maneuverability.
  • Mouth Opening < 3 cm - Restricted access for laryngoscope blade insertion.
  • Limited Neck Mobility - Inability to extend at atlanto-occipital joint impairs laryngeal visualization.
  • Obesity (BMI > 35 kg/m²) - Increases risk of difficult mask ventilation and intubation.
  • Obstructive Sleep Apnea (OSA) - Associated with pharyngeal soft tissue redundancy and obstruction.
  • Previous Difficult Intubation - Strong predictor; always review prior anesthesia records.
  • Anatomical Features - Short neck, large tongue, receding mandible, prominent incisors, high arched palate, or facial trauma.
ASA Difficult Airway Algorithm 2022

Approach to the Difficult Airway

  1. Assess Likelihood of Difficulty: Evaluate for difficult mask ventilation, supraglottic airway use, laryngoscopy, intubation, and front-of-neck access.
  2. Prepare Equipment & Personnel: Ensure availability of difficult airway cart, video laryngoscopy, supraglottic airways, and backup personnel.
  3. Optimize Patient Positioning: Head-elevated laryngoscopy position (HELP) improves glottic view in obese patients.
  4. Pre-oxygenate Adequately: Aim for EtO₂ > 90% to extend safe apnea time. Consider apneic oxygenation via nasal cannula.
  5. Initial Intubation Attempt: Use video laryngoscopy as first-line (improves first-pass success). Limit attempts to preserve airway anatomy.
  6. If Intubation Fails - Call for Help: Activate difficult airway protocol. Ensure oxygenation via mask or supraglottic airway.
  7. Awaken Patient vs. Emergency Pathway: If surgery is elective and patient is stable, awaken and consider awake intubation. If cannot intubate/cannot oxygenate → Emergency front-of-neck access (cricothyrotomy).
Management Strategies
  • Video Laryngoscopy - Improves first-pass success and should be considered first-line for anticipated difficult airways.
  • Awake Fiberoptic Intubation - Gold standard for known difficult airways. Requires topical anesthesia and patient cooperation.
  • Supraglottic Airways (LMA) - Rescue device for failed intubation; can serve as conduit for fiberoptic intubation.
  • Bougie/Gum Elastic Stylet - Increases success rate when only epiglottis is visualized.
  • Emergency Front-of-Neck Access - Life-saving procedure for "cannot intubate, cannot oxygenate" scenarios. Requires scalpel cricothyrotomy training.

Key Principle: Always have a backup plan. The most important decision is recognizing when to stop attempts at intubation, maintain oxygenation, and escalate to advanced techniques or emergency airway access. Early preparation and communication with the surgical team are critical for patient safety.

References
  1. Apfelbaum JL, et al. 2022 American Society of Anesthesiologists Practice Guidelines for Management of the Difficult Airway. Anesthesiology. 2022;136(1):31-81. PMID: 34762729
  2. Cook TM, et al. Major complications of airway management in the UK: results of the Fourth National Audit Project (NAP4). Br J Anaesth. 2011;106(5):617-631. PMID: 21447488
  3. Frerk C, et al. Difficult Airway Society 2015 guidelines for management of unanticipated difficult intubation in adults. Br J Anaesth. 2015;115(6):827-848. PMID: 26556848
  4. Shiga T, et al. Predicting difficult intubation in apparently normal patients: a meta-analysis of bedside screening test performance. Anesthesiology. 2005;103(2):429-437. PMID: 16052126
  5. Aziz MF, et al. Routine clinical practice effectiveness of the Glidescope in difficult airway management: an analysis of 2,004 Glidescope intubations. Anesth Analg. 2011;112(3):578-582. PMID: 21224234
  6. Chrimes N. The Vortex: a universal 'high-acuity implementation tool' for emergency airway management. Br J Anaesth. 2016;117(suppl 1):i20-i27. PMID: 27566802
  7. Levitan RM, et al. Head-elevated laryngoscopy position: improving laryngeal exposure during laryngoscopy by increasing head elevation. Ann Emerg Med. 2003;41(3):322-330. PMID: 12605196
  8. Law JA, et al. Canadian Airway Focus Group updated consensus-based recommendations for management of the difficult airway: part 1. Can J Anaesth. 2021;68(9):1373-1404. PMID: 34251647