Airway Assessment

Airway Assessment

David Ray Velez, MD

Table of Contents

Assessment of the Difficult Airway
Classification/Scoring
Difficult Bag Mask Ventilation (BMV)
Difficult Laryngeal Mask Airway (LMA) Placement
Difficult Cricothyroidotomy

See Also:
*See Rapid Sequence Intubation (RSI)
*See Cricothyroidotomy

Assessment of the Difficult Airway

Difficult Airway: A Clinical Condition in Which There is Difficulty with Face Mask Ventilation, Supraglottic Ventilation, or Endotracheal Intubation

  • Review History for Prior Intubation Attempts to Understand Prior Grades, Difficulties, and Necessary Adjuncts
  • Measures to Predict a Difficult Airway are Neither Sensitive nor Specific
  • Airway Assessment May Be Contraindicated in Emergency Scenarios

Indicators of Difficult Intubation

  • History of Difficult Intubation
  • Interincisor Distance < 3 cm
  • Thyromental Distance < 3 Fingerbreadths (About 7 cm)
  • High, Arched, Narrow Palate
  • Mallampati Class III-IV
  • Inability to Bring Mandibular Incisors Anterior the Maxillary Incisors
  • *Morbid Obesity is a Predictor of Difficult Mask Ventilation but Not Independently Associated with Difficult Intubation

LEMON Approach to Airway Assessment

  • L: Look Externally
    • Level of Consciousness
    • Obesity
    • Bearded
    • Craniofacial Deformity
  • E: Evaluate 3-3-2 Rule
    • Interincisor Distance: Distance Between the Upper and Lower Teeth
      • Distance < 3 Fingerbreadths Indicates a Difficult Airway
    • Hyoid-to-Mental Distance: Distance Between the Hyoid Bone and Mental Protuberance of the Mandible
      • Distance < 3 Fingerbreadths Indicates a Difficult Airway
    • Thyroid-to-Hyoid Distance: Distance Between the Thyroid Cartilage and Hyoid Bone
      • Distance < 2 Fingerbreadths Indicates a Difficult Airway
  • M: Mallampati Score
    • Class III-IV Indicates Difficult Intubation
    • *See Classification/Scoring Below
  • O: Obstruction
    • Epiglottitis
    • Head/Neck Cancer
    • Neck Hematoma
    • Foreign Body
    • Thermal Injury
  • N: Neck Mobility
    • Evaluate for Neck Extension if Able
    • May Be Unable to Move in Trauma Patient (Cervical Collar)

6-D Approach to Airway Assessment

  • 1D: Disproportion
    • Mallampati Class
    • Enlarged Tongue
    • Airway Swelling
    • Airway Trauma
    • Tracheal Deviation
  • 2D: Distortion
    • Neck Mass
    • Neck Hematoma/Abscess
    • Prior Surgical Airway
  • 3D: Decreased Thyromental Distance
    • Thyromental Distance < 7 cm (3 Fingerbreadths)
  • 4D: Decreased Interincisor Distance
    • Interincisor Distance < 3 Fingerbreadths
  • 5D: Decreased Range of Motion
    • Limited Neck Extension
    • Cervical Collar
    • Cervical Contracture or Burns
    • Short/Thick Neck
  • 6D: Dental Overbite
    • Overbite
    • Large Angled Teeth Disrupting Alignment

Classification/Scoring

Cormack-Lehane Laryngoscopy Classification

  • View During Direct Laryngoscopy Associated with Risk for Difficult Intubation
  • Classification:
    • Grade 1: Full Glottis
    • Grade 2: Partial Glottis
      • 2a: Partial Glottis
      • 2b: Arytenoids Only
    • Grade 3: Epiglottis, No Glottis
    • Grade 4: No Epiglottis or Glottis
  • Class ≥ 2b Indicates Difficult Intubation

Cormack-Lehane Classification 1

Grade Percentage of Patients Percentage with Difficult Intubations
1 74% < 1%
2a 21% 13%
2b 3% 65%
3 2% 80%
4 < 1% 100%

Mallampati Score (Modified)

  • External View of the Oral Cavity Used to Estimate Risk for Difficult Intubation
  • Modified Classification:
    • Class I: Visualize Soft Palate, Entire Uvula, Fauces, and Tonsillar Pillars
    • Class II: Visualize Soft Palate, Partial Uvula, and Fauces
    • Class III: Visualize Soft Palate and Base of Uvula
    • Class IV: Visualize Only Hard Palate
  • Class III-IV Indicates Difficult Intubation
    • Positive Predictive Value is Only 21-50%
  • *Worse Prognostic Value than the Cormack-Lehane Classification

Mallampati Score 2

Difficult Bag Mask Ventilation (BMV)

MOANS Mnemonic

  • Mask Seal (Beards, Crusted Blood on Face, Craniofacial Deformity)
  • Obesity
  • Age > 55 Years
  • No Teeth
  • Sleep Apnea/Stiff Lungs (COPD, Asthma, ARDS)

BONES Mnemonic

  • Beard or Other Cause of Difficult Mask Seal
  • Obesity
  • No Teeth
  • Elderly (Age > 55 Years)
  • Sleep Apnea/Stiff Lungs (COPD, Asthma, ARDS)

ROMAN Mnemonic

  • Restriction (Poor Lung Compliance – ARDS, etc.)
  • Obesity or Obstruction (Sleep Apnea)
  • Mask Seal (Beards, Crusted Blood on Face, Craniofacial Deformity)
  • Age > 55 Years
  • No Teeth

Difficult Laryngeal Mask Airway (LMA) Placement

RODS Mnemonic

  • Restricted Mouth Opening
  • Obstruction
  • Disrupted/Distorted Airway
  • Stiff Lungs or C-Spine

Difficult Cricothyroidotomy

SHORT Mnemonic

  • Surgery
  • Hematoma or Abscess
  • Obesity
  • Radiation Distortion or Deformity
  • Tumor

SMART Mnemonic

  • Surgery
  • Mass (Hematoma, Abscess)
  • Access or Anatomy (Obese, Poor Landmarks)
  • Radiation Distortion or Deformity
  • Tumor

References

  1. Zeger WG, Branecki CE, Nguyen TT, Hall T, Boedeker B, Boedeker D, Wadman MC. A description of teaching methods using an on-site instructor versus a distant site instructor to train laryngoscopy to medical students in Hanoi, Vietnam, from Omaha, Nebraska, by video communication. Int J Emerg Med. 2015 Dec;8(1):44. (License: CC BY-4.0)
  2. Nørskov AK, Rosenstock CV, Wetterslev J, Lundstrøm LH. Incidence of unanticipated difficult airway using an objective airway score versus a standard clinical airway assessment: the DIFFICAIR trial – trial protocol for a cluster randomized clinical trial. Trials. 2013 Oct 23;14:347. (License: CC BY-2.0)