A long-term heavy smoker presents with an increased anteroposterior chest diameter ('barrel chest'), pursed-lip breathing and a chronic productive cough. The MOST likely diagnosis is:

Correct answer: C. Chronic obstructive pulmonary disease

• A. ❌ Pulmonary fibrosis is a RESTRICTIVE disease — the lungs become small and stiff, with reduced volumes and fine inspiratory crackles.
• B. ❌ Asthma is episodic and reversible; between attacks the chest is normal, and barrel chest is not a typical feature.
• C. ✅ CORRECT — A BARREL CHEST reflects chronic air trapping and lung hyperinflation, the hallmark of emphysema/COPD. Combined with a heavy smoking history, pursed-lip breathing and chronic productive cough, COPD is the diagnosis.
• D. ❌ CHF causes dyspnea, orthopnea and peripheral edema; the chest shape is unchanged.

Note: Dental management: keep the patient UPRIGHT (never supine), avoid respiratory depressants such as nitrous oxide and opioids, avoid rubber dam if it worsens breathing, and use pulse oximetry.