Epidemiology: - Prevalence of injury causing death or brain damage: in the respiratory events category, difficult intubation (23% of total respiratory events) and inadequate ventilation/oxygenation (22%) were the most frequent. Esophageal intubation (13%) and premature extubation (12%) were the next most common (1).
- Prevalence of difficult airway with conventional direct laryngoscopy: difficult tracheal intubation (>2 laryngoscopies) in 1.8% (25% of which are predicted pre-operatively), awkward tracheal intubation (<=2 laryngoscopies) in 2.5%, failure of tracheal intubation in 0.1-0.3% (which rises to 3.7% if the patient also has difficult mask ventilation) and surgery postponed in 0.05% (3,4).
- Prevalence of unanticipated difficult airway (1.73%), 93% of which were not predicted pre-operatively (4).
Measurements (2): airway examination components -> nonreassuring findings if... - Length of upper incisors -> relatively long.
- Relation of maxillary and mandibular incisors during normal jaw closure -> prominent "overbite" (maxillary incisors anterior to mandibular incisors).
- Relation of maxillary and mandibular incisors during voluntary protrusion of the lower jaw -> patient cannot bring mandibular incisors anterior (in front of) maxillary incisors.
- Interincisor distance -> <3 cm.
- Visibility of uvula -> not visible when tongue is protruded with patient in sitting position (e.g., Mallampati > II).
- Shape of palate -> highly arched or very narrow.
- Compliance of mandibular space -> stiff, indurated, occupied by mass, or nonresilient.
- Thyromental distance -> <3 ordinary finger breadths.
- Lenght of neck -> short.
- Thickness of neck -> thick.
- Range of motion of head and neck -> patient cannot touch tip of chin to chest or cannot extend neck.
References: - Trends in anesthesia-related death and brain damage. Anesthesiology. 2006;105:1081-1086: full text | pdf.
- Practice guidelines for management of the difficult airway. An updated report by the American Society of Anesthesiologys task force on management of the difficult airway. Anesthesiology. 2003;98(5):1269-1277: full text | pdf.
- The airway: problems and predictions in 18'500 patients. Can Anaesth Soc J. 1994;41:361-365: pdf.
- A. K. Nørskov et al. Diagnostic accuracy of anesthesiologists' prediction of difficult airway management in daily clinical practice: a cohort study of 188064 patients registered in the Danish Anaesthesia Database. Anaesthesia. 2015;70(3): 272-281: full text | pdf.
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