What is the definition of a difficult airway?

Definition of a Difficult Airway

A difficult airway is defined as a clinical situation in which a physician trained in anesthesia care experiences anticipated or unanticipated difficulty or failure with face-mask ventilation, laryngoscopy, ventilation using a supraglottic airway, tracheal intubation, extubation, or invasive airway. 1

Specific Types of Difficult Airways

Difficult Facemask Ventilation

• Occurs when it is not possible to provide adequate ventilation (confirmed by end-tidal carbon dioxide detection) due to:
  • Inadequate mask seal
  • Excessive gas leak
  • Excessive resistance to the ingress or egress of gas 1

Difficult Laryngoscopy

• Defined as inability to visualize any portion of the vocal cords after multiple attempts at laryngoscopy 1
• May be further subdivided into grades according to the Cormack & Lehane classification, with grade 3 being subdivided into 3a (epiglottis can be lifted) and 3b (epiglottis cannot be lifted from the posterior pharyngeal wall) 1

Difficult Supraglottic Airway Ventilation

• Occurs when adequate ventilation cannot be provided due to:
  • Difficult supraglottic airway placement
  • Multiple attempts required for placement
  • Inadequate supraglottic airway seal
  • Excessive gas leak
  • Excessive resistance to gas flow 1

Difficult or Failed Tracheal Intubation

• Defined as either:
  • Tracheal intubation requiring multiple attempts
  • Complete failure of tracheal intubation after multiple attempts 1

Difficult or Failed Tracheal Extubation

• The loss of airway patency and adequate ventilation after removal of a tracheal tube or supraglottic airway from a patient with a known or suspected difficult airway (an "at risk" extubation) 1

Difficult or Failed Invasive Airway

• Anatomic features or abnormalities that reduce or prevent the likelihood of successfully placing an airway into the trachea through the front of the neck 1

Signs of Inadequate Ventilation

• Absent or inadequate exhaled carbon dioxide
• Absent or inadequate chest movement
• Absent or inadequate breath sounds
• Auscultatory signs of severe obstruction
• Cyanosis
• Gastric air entry or dilatation
• Decreasing or inadequate oxygen saturation
• Absent or inadequate exhaled gas flow as measured by spirometry
• Anatomic lung abnormalities detected by lung ultrasound
• Hemodynamic changes associated with hypoxemia or hypercarbia (hypertension, tachycardia, bradycardia, arrhythmia)
• Changed mental status or somnolence 1

Clinical Application

• These definitions apply to all airway management and anesthetic care delivered in:
  • Inpatient settings (perioperative, non-operating room, emergency department, critical care)
  • Ambulatory settings (surgery centers, office-based procedures) 1
• The guidelines are intended for use by anesthesiologists and all others who perform anesthesia care or airway management 1

Important Considerations

• Difficult airways should be anticipated whenever possible through comprehensive assessment 2
• The incidence of difficult mask ventilation varies widely (0.08% to 15%) depending on the criteria used 3
• Predictors of difficult mask ventilation include obesity, age >55 years, history of snoring, lack of teeth, presence of beard, Mallampati Class III or IV, and abnormal mandibular protrusion 3
• Difficult tracheal intubation is more frequent in patients who experience difficult mask ventilation 3
• The most critical airway situation, "cannot intubate, cannot oxygenate," occurs rarely (0.0019-0.04%) but can have severe consequences including hypoxic brain damage and death 4

Management Approach

• Management should follow a structured algorithm with Plans A through D as outlined by airway management societies 1
• Each plan should be implemented sequentially based on the outcome of the previous plan 1
• Preparedness for failed intubation and use of adjuncts such as video laryngoscopy, supraglottic airway devices, and awake intubation techniques are essential components of difficult airway management 2