EBQ:ED Airway Assessment Score Predicting Difficult Intubation

Complete Journal Club Article
Reed MJ. "Can an airway assessment score predict difficulty at intubation in the emergency department?". Emergency Medicine Journal. 2005. 22(2):99-102.
PubMed Full text PDF

Clinical Question

Can an airway assessment scale based on LEMON methodology predict difficulty of intubation in the ED?

Conclusion

The LEMON airway assessment score based successfully predicts difficult poor laryngoscopic views although not necessarily predict airway intubation failure.

Mallampati Score
3-3-2 ruleDistance between patient's incisor teeth of 3 finger breadths and distance between the thyroid notch and the floor of the mouth should be at least 2 finger widths

Major Points

Assessment of the airway difficulty prior to intubation allows the emergency physician to stratify the risk of intubation difficulty.[1] Since most emergency department intubations are not elective, it is important to prepare with all airway adjuncts (Bougie, Supraglottic device, and video laryngoscopy) prior to attempt. This study demonstrates that the LEMON mneumonic can successfully stratify risk but not necessarily predict intubation failure. There were no failures in this study and preparation should always anticipate the need for surgical airway management as the end point for patients with respiratory failure and failed intubation.

Difficult Airway Predictor Point
Any of 4 important LOOK criteria:
  1. Facial trauma
  2. Large incisors
  3. Facial Hair
  4. Large tongue|
1 point each
Mouth opening less than three finger breadths 1
Hyo-mental distance less than three finger breadths 1
Thyro-hyoid distance less than two finger breadths 1
Presence of an obstructed airway 1
Presence of poor neck mobility 1

Increasing score equates to increasing difficulty for chord visualization but not necessarily intubation failure rates.

Design

  • Prospective observational study conducted in the ED of a UK teaching hospital between June 2002 and September 2003
  • Intubation was recorded according to Cormack and Lehane scores if the patient required intubation[2]


Population Studied

Inclusion Criteria

  • All patients who entered one of the department’s resuscitation rooms

Exclusion Criteria

  • Only patients requiring intubation underwent the procedure

Baseline Characteristics

  • N= 156
  • Median Age= 55yo
  • Male= 71%

Interventions

  • All patients underwent an airway assessment according to the LEMON method and many underwent the Mallampati score. Only patients requiring intubation had a Cormack and Lehane score recorded and had intubation attempted.

Outcomes

Primary Outcomes

Patients with large incisors, reduced inter-incisor distance and a reduced thyroid to floor of mouth distance were more likely to have worse laryngoscopic view on intubation.

  • All patients were successfully intubated

Subgroup Analysis

  • There was no statistical difference in intubation grade in patients with:
    • Facial trauma (p = 1.0)
    • Beard or moustache (p = 0.49)
    • Large tongue (p = 0.49)
    • Reduced hyoid to chin distance (p = 0.34)
  • There was a statistical association in intubation grade in patients with:
    • Reduced inter-incisor distance (p=0.05)
    • Reduced thyroid to floor of mouth distance (p=0.05)

Discussion

  • The airway manager performing the LEMON assessment also performed the intubation introducing the risk for bias.
  • Difficulty of intubation was defined by vocal cord views however this did not prevent any failed intubations
  • No airway adjuncts were used for intubation however preparation should include appropriate preoxygenation and preparation for cricothyrotomy if all methods of intubation are unsuccessful

Funding

  • No industry funding

See Also

Review Questions

1

The 2 in the 3-3-2 Rule refers to:

the distance between the patient's incisor teeth
the distance between the thyroid notch and the floor of the mouth
the distance between the thyroid notch and the chin
the distance between the hyoid bone and the chin
the distance between the floor of the mouth and the nose

2

National guidelines suggest no more than three ETI attempts before either inviting more skilled personnel or employing ìdifficult airwayî tools.

True
False

3

The 3s in the 3-3-2 Rule refers to:

the distance between the patient's incisor teeth
the distance between the thyroid notch and the floor of the mouth
the distance between the thyroid notch and the chin
the distance between the hyoid bone and the chin
the distance between the floor of the mouth and the nose


References

  1. Murphy MF, Walls RM. The difficult and failed airway. In: Manual of emergency airway management. Chicago: Lippincott Williams and Wilkins, 2000:31–9
  2. Cormack RS, Lehane J. Difficult intubation in obstetrics. Anaesthesia 1984;39:1105–11.