How do you assess for airway restrictions on physical exam in a patient, potentially with a history of respiratory disease such as Chronic Obstructive Pulmonary Disease (COPD) or asthma?

Physical Examination Assessment for Airway Restrictions

Key Physical Examination Parameters

For patients with suspected airway obstruction, perform a focused respiratory system examination assessing five critical anatomical parameters that predict difficult airway management and obstruction severity. 1

Essential Airway Assessment Components

The American College of Chest Physicians recommends evaluating these specific parameters that impact airway patency and management 1:

1. Mouth Opening - Measure inter-incisor distance; normal is ≥3 finger breadths (approximately 4-5 cm). Reduced opening suggests potential upper airway restriction 1

2. Mallampati Classification - With patient sitting upright, mouth fully open, tongue protruded without phonation, assess visible oropharyngeal structures. Modified Mallampati Class III-IV indicates higher likelihood of airway difficulty, though sensitivity is limited (0.51 for difficult intubation) 2

3. Thyromental Distance - Measure from thyroid notch to mentum with neck fully extended; normal is >3 finger breadths (>6.5 cm). Reduced distance correlates with airway restriction 1

4. Neck Mobility and Cervical Spine Assessment - Evaluate ability to assume "sniff position" (neck flexion with head extension). Limited mobility increases airway management difficulty 1, 3

5. Upper Lip Bite Test - Ask patient to bite upper lip with lower incisors. This test demonstrates the highest sensitivity (0.67) for detecting difficult laryngoscopy among bedside tests 2

Respiratory-Specific Physical Findings

For patients with chronic airway disease (COPD/asthma), the following signs become apparent as disease progresses 1:

• Quiet or diminished breath sounds - Positive likelihood ratio >5.0 for COPD presence 1
• Prolonged expiratory phase - Indicates expiratory flow limitation 1
• Hyperresonance to percussion - Suggests hyperinflation 1
• Use of accessory muscles - Indicates increased work of breathing 4
• Cyanosis - Late sign of severe obstruction 1
• Weight loss and reduced BMI - Values <21 kg/m² associated with increased mortality 1

Important caveat: Physical examination is commonly normal in mild COPD, and history/examination alone are not sensitive for diagnosis 1. Many patients deny symptoms because they've restricted activities to avoid triggering them 1.

Functional Assessment

Beyond static examination 1:

• Respiratory rate at rest - Document baseline 4
• Oxygen saturation - Measure at rest and with exertion 1
• Modified Medical Research Council (mMRC) dyspnea score - Quantifies functional limitation; scores ≥2 predict mortality 1
• Observe for stridor or stertor - Audible respiratory sounds indicate significant upper airway narrowing 5

Critical Pitfall to Avoid

Do not rely solely on physical examination to rule out airway obstruction. 1 The American Thoracic Society emphasizes that history and physical examination in isolation lack sensitivity for detecting airflow limitation 1. Spirometry is essential for confirming obstruction in symptomatic patients with risk factors 1, 6. For central airway obstruction specifically, chest CT imaging is recommended alongside physical examination 1.

When to Escalate Assessment

Proceed immediately to advanced airway evaluation (bronchoscopy, CT imaging) if 1:

• Acute respiratory distress with stridor
• Progressive dyspnea at rest
• Inability to lie flat due to orthopnea
• Oxygen saturation <90% on room air
• Signs of impending respiratory failure