What is the recommended approach for airway assessment?

Comprehensive Approach to Airway Assessment

A thorough airway assessment must include evaluation of risks for difficult intubation, difficult rescue techniques, and aspiration, with particular attention to head and neck pathology, mouth opening, neck extension, and body habitus to reduce morbidity and mortality associated with airway management. 1

Key Components of Airway Assessment

Physical Examination Tests

1. Mallampati Classification

   • Assess visibility of oropharyngeal structures with mouth open and tongue protruded
   • Classes III and IV indicate higher risk of difficult laryngoscopy (specificity 84%) 2
   • Valid even in supine patients with voluntary mouth opening 1

2. Thyromental Distance (Patil-Aldreti Test)

   • Measure distance from thyroid notch to mental prominence
   • < 6.5 cm suggests difficult laryngoscopy
   • Highest sensitivity, negative predictive value, and accuracy among common tests 3

3. Upper Lip Bite Test

   • Assess ability to bite upper lip with lower incisors
   • Class III (inability to bite upper lip) has highest specificity and positive predictive value 3
   • Highest sensitivity (67%) for predicting difficult laryngoscopy compared to other tests 4

4. Mouth Opening/Inter-incisor Gap

   • Measure distance between upper and lower incisors
   • < 4 cm suggests potential difficulty 5

5. Head and Neck Movement

   • Assess atlantooccipital extension
   • Limited extension/flexion has 99% specificity for difficult intubation 2
   • Position for optimal intubation: lower cervical spine flexed, upper cervical spine extended ("sniffing position") 1

6. Neck Circumference/Obesity Assessment

   • Increased neck circumference associated with difficult intubation 1
   • BMI ≥ 25 kg/m² increases odds of difficult intubation 5

7. Laryngeal Handshake Technique

   • Recommended to identify cricothyroid membrane 1
   • Important for planning potential front-of-neck airway access

Advanced Assessment Methods

1. Ultrasonography

   • More accurate than palpation for identifying cricothyroid membrane 1
   • Can detect airway pathology and distorted anatomy 6
   • Useful for uncooperative or unstable patients 6

2. MACOCHA Score

   • Score ≥ 3 predicts difficult intubation in critically ill patients 1
   • Incorporates multiple risk factors specific to critical care setting

3. Total Airway Score (TAS)

   • Combines multiple assessment factors
   • TAS > 6 has odds ratio of 13.57 for difficult intubation 5

Special Considerations

Critically Ill Patients

• Full assessment may be impractical but removing facemask briefly can enable basic assessment 1
• Consider nasal oxygenation to facilitate assessment and subsequent pre-oxygenation 1
• Assess cardiorespiratory status as hemodynamic optimization prior to induction improves outcomes 1

Obstetric Patients

• Risk factors similar to non-pregnant patients: high Mallampati score, short neck, receding mandible, protruding maxillary incisors, increased neck circumference 1
• Consider physiological changes of pregnancy that may impact airway management

Anticipated Difficult Airway

• Consider awake tracheal intubation when difficult airway is predicted 1
• Ensure appropriate team assembly and pre-intubation briefing 1
• Develop clear plans for primary approach and backup strategies 1

Limitations and Pitfalls

• No single test is perfect: Prediction of difficult airway management is unreliable with poor sensitivity and specificity 1, 4
• Combine multiple tests: Using several assessment methods improves predictive accuracy 3
• False negatives are dangerous: Even with thorough assessment, unanticipated difficult airways will occur 4
• Avoid relying solely on Mallampati: Despite widespread use, it has limited predictive value when used alone 4
• Avoid diagnostic laryngoscopy: Not recommended for airway assessment as it may lead to critical situations 1

Practical Implementation

1. Document all airway assessment findings systematically
2. Communicate findings clearly to the entire team
3. Develop primary and backup airway management plans based on assessment
4. Ensure appropriate equipment and assistance are available
5. Position patient optimally based on assessment findings
6. Consider awake techniques when multiple risk factors are present

Remember that even with thorough assessment, the unanticipated difficult airway will still occur, making preparation for alternative approaches essential for patient safety.