A 52-year-old male with a history of rheumatoid arthritis presents for elective knee replacement surgery. On pre-anesthetic evaluation, he has restricted neck mobility and a history of difficult intubation during a previous surgery 5 years ago. Which investigation is most appropriate to objectively assess his airway and predict intubation difficulty?

## Investigation of Choice for Airway Assessment in High-Risk Patients ### Clinical Context This patient has multiple risk factors for difficult airway: - Rheumatoid arthritis (atlantoaxial subluxation risk, temporomandibular joint involvement) - Restricted neck mobility - Previous history of difficult intubation ### Why Fiberoptic Laryngoscopy Is the Answer **Key Point:** Fiberoptic laryngoscopy is the gold standard for **direct visualization** of the larynx and prediction of intubation difficulty in high-risk patients. It provides: 1. Direct assessment of glottic opening and vocal cord mobility 2. Identification of anatomical abnormalities (stenosis, masses, edema) 3. Ability to perform awake intubation if needed 4. Highest sensitivity and specificity for difficult airway prediction **High-Yield:** In patients with: - Previous difficult intubation - Rheumatoid arthritis with cervical involvement - Restricted neck mobility - Suspected laryngeal pathology ...fiberoptic laryngoscopy is the investigation of choice for **objective airway assessment**. ### Comparison of Airway Assessment Investigations | Investigation | Sensitivity | Specificity | Utility | Limitation | | --- | --- | --- | --- | --- | | **Mallampati Score** | 46–65% | 60–90% | Screening in low-risk patients | Poor predictive value in isolation | | **Fiberoptic Laryngoscopy** | 90–95% | 85–95% | Direct visualization; high-risk patients | Requires expertise; equipment-dependent | | **Thyromental Distance** | 50–70% | 70–80% | Bedside assessment | Unreliable alone; poor in obese patients | | **CT Neck** | High | High | Anatomical detail; masses, stenosis | Radiation; not dynamic; overkill for routine cases | **Clinical Pearl:** Fiberoptic laryngoscopy is **both diagnostic and therapeutic** — if difficult intubation is confirmed, the same instrument can be used for awake intubation, avoiding the need for emergency surgical airway. ### Why Mallampati Score Is Insufficient Here **Warning:** Mallampati score alone has poor positive predictive value (only 5–15%) for difficult intubation. It is a **screening tool**, not a confirmatory test. In this high-risk patient, it is inadequate for decision-making. **Mnemonic for Mallampati Grades:** **"PUFF"** = Pharynx, Uvula, Fauces, Frenulum visibility - Grade I: Soft palate, uvula, fauces, pillars visible - Grade II: Soft palate, uvula visible - Grade III: Soft palate, base of uvula visible - Grade IV: Soft palate not visible Grades III–IV suggest difficult intubation, but sensitivity is low.