Predicting Difficult Mask Ventilation and Intubation




Predicting Difficult and Impossible Mask Ventilation



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  • Overall incidence of difficult mask ventilation (DMV) is 1.4% with impossible mask ventilation (IMV) 0.15%
  • Obesity, snoring, and lack of teeth can probably be overcome with simple airway maneuvers, which is why they are not risk factors for IMV:

    • Lack of teeth actually makes DL and intubation easier

  • Neck circumference (> 50 or 60 cm at the level of the cricoid cartilage) is the most predictive factor of IMV
  • Patients with three or more risk factors have a much higher likelihood of being IMV (odds ratio 8.9)
  • Most patients (75%) who are IMV will be easy to intubate




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Risk Factors Associated with Difficult versus Impossible Mask Ventilation





























Difficult mask ventilation Impossible mask ventilation
Neck circumference Neck circumference
Male sex Male sex
Sleep apnea Sleep apnea
Mallampati class 3 or 4 Mallampati class 3 or 4
Beard Beard
BMI >26
Snoring
Lack of teeth




Predicting Difficult Intubation



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  • Overall incidence of difficult intubation (DI) is 5.2% (obstetric: 3.1%, obese: 15.8%) with failed tracheal intubation 0.15%
  • A combination of tests tends to be a better predictor of DI than individual tests




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Reliability of Different Characteristics Associated with Difficult Intubation










































































Characteristics associated with difficult intubation Definition Sensitivity (%) Specificity (%) Positive predictive value or positive likelihood (PL)
Interincisor gap <4 cm 30 97 28
Range of neck extension Head extension ≤80° 10 93 18
Retrognathia >90° 7 99 20
Thyromental distance <6.5 cm 48 79 9.4 (<4 cm)
Mentohyoid distance <4.5 cm 16 91 6
Sternomental distance <12.5 cm 44 87 11
Neck circumference >43 cm 92 84 37
Mallampati classification Grade 3 or 4 view 49 86 3 (PL)
BMI >30 83 50 14
Indirect laryngoscopy Grade 3 or 4 view 69 98 31
Upper lip bite test Class 3 (lower incisors cannot bite upper lip) 8 97 8

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Jun 27, 2019 | Posted by in ANESTHESIA | Comments Off on Predicting Difficult Mask Ventilation and Intubation
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