Airway Evaluation in a Patient with Huge Thyroid Swelling + Stridor

1. Why This Is a High-Risk Situation

2. Clinical History

3. Physical Examination

a. General

• Degree of respiratory distress - use of accessory muscles, paradoxical breathing, tracheal tug
• Oxygen saturation on room air

b. Neck/Goiter Assessment

• Size and consistency of the swelling - hard/fixed raises concern for malignancy
• Tracheal deviation - visible or palpable shift from midline
• Substernal extension - goiter descending below sternal notch on swallowing
• Fixity to underlying structures
• Pemberton's sign: Ask the patient to raise both arms above the head. Development of venous engorgement, facial plethora, or subjective respiratory discomfort suggests obstruction at the thoracic inlet from a large/substernal goiter - a positive Pemberton's sign is a critical finding.

c. Laryngeal/Airway Examination

• Vocal cord mobility - must be assessed in ALL patients (indirect laryngoscopy or flexible nasendoscopy); bilateral RLN palsy post-compression is catastrophic
• Stridor character: inspiratory stridor suggests supraglottic or extrathoracic tracheal obstruction; biphasic stridor indicates a fixed, severe obstruction
• Mallampati classification - though less predictive in this context, still useful
• Thyromental distance (<3 fingerbreadths = likely difficult intubation)
• Mouth opening, neck mobility, jaw prognathism

d. Standard Difficult Airway Predictors (ASA 2022)

• Long upper incisors, prominent overbite
• Distance between incisors ≤3 cm
• Uvula not visible with tongue protruded (Mallampati III/IV)
• Highly arched/narrow palate
• Noncompliant mandibular space
• Short thick neck, limited head/neck range of motion

4. Investigations

a. Imaging

• Determines degree and level of tracheal compression/deviation
• Assesses substernal/posterior mediastinal extension
• Identifies vascular anomalies (e.g., lusoria artery, rare non-recurrent laryngeal nerve)
• Scan should span skull base to tracheal bifurcation for complete assessment
• Detects lateral or anteroposterior compression that plain films may miss

• Tracheal narrowing or deviation
• Retrosternal extension
• Calcification within the goiter

b. Pulmonary Function Tests - Flow-Volume Loop

c. Flexible Nasendoscopy / Laryngoscopy

• Performed under topical anaesthesia as an awake procedure
• Assesses supra- and glottic pathology, vocal cord mobility
• Can inspect subglottis and upper trachea
• Identifies any co-existing laryngeal pathology
• Helps plan tube size and placement

d. Laboratory

• TSH - to exclude subclinical hyperthyroidism/thyrotoxicosis (thyroid storm risk perioperatively)
• Thyroid antibodies - autoimmune aetiology
• Serum calcium - baseline before surgery
• FNA cytology of suspicious nodules under ultrasound guidance

e. Ultrasound

• Assess vascularity, nodule characteristics
• Does NOT reliably assess tracheal compression (CT is superior for this)

5. Anaesthetic/Pre-operative Airway Planning

Key decisions:

1. Awake vs. asleep intubation - In patients with significant tracheal compression and stridor, awake fiberoptic bronchoscopic intubation is the technique of choice. Induction of anaesthesia and muscle relaxants can precipitate complete airway collapse in a patient with tracheal softening (tracheomalacia) from chronic compression.
2. Tube size - A narrowed trachea may require a smaller ETT; rigid bronchoscopy may be needed if the tube cannot pass
3. Tracheostomy readiness - A surgical airway setup must be immediately available
4. Tracheomalacia risk - Chronic tracheal compression can cause cartilage softening; post-extubation collapse is a known complication even after goiter removal (see recent meta-analysis on tracheomalacia post-thyroidectomy, PMID 40070511)

Red flags requiring urgent/emergency intervention:

• Rapidly worsening stridor
• Acute respiratory failure (SpO2 falling)
• Recent sudden enlargement (hemorrhage into nodule at thoracic inlet)
• Bilateral vocal cord paralysis

Summary: Evaluation Framework

HISTORY → Severity, progression, positional, voice change, dysphagia
        ↓
EXAMINATION → Pemberton's sign, tracheal deviation, vocal cord mobility,
              difficult airway predictors (Mallampati, TMD, mouth opening)
        ↓
INVESTIGATIONS
  → CT neck/chest (skull base to carina) — anatomy, compression degree
  → Flow-volume loop — functional severity (inspiratory plateau = extrathoracic)
  → Flexible nasendoscopy — cord mobility, subglottic status
  → TSH, FNA of concerning nodules
        ↓
AIRWAY PLAN → Awake FOB intubation preferred
           → Surgical airway standby
           → Tracheomalacia precautions post-op

• Scott-Brown's Otorhinolaryngology Head & Neck Surgery, Vol. 1 - Prediction of Difficulty, p. 360
• K.J. Lee's Essential Otolaryngology - Euthyroid Goiter, p. 729
• Bailey and Love's Short Practice of Surgery, 28th ed. - Goitre Investigations
• Sabiston Textbook of Surgery, 7e - Cross-Sectional Imaging, p. 1494
• Cummings Otolaryngology Head and Neck Surgery - Difficult Airway, p. 104
• Barash, Cullen, and Stoelting's Clinical Anesthesia, 9e - Airway Examination Table 23-7
• Tracheomalacia post-thyroidectomy: PMID 40070511 (2025 systematic review)