A 68-year-old male smoker (60 pack-years) presents with severe exertional dyspnea, bibasilar crackles, and lower-extremity edema. HRCT shows upper-lobe centrilobular emphysema and lower-lobe UIP-pattern fibrosis with honeycombing. Echocardiography reveals severe pulmonary hypertension (RVSP 65 mm Hg). Pulmonary function tests show: FVC 82% predicted, FEV1/FVC ratio 79%, TLC 88% predicted, but DLCO 28% predicted with reduced KCO. The pattern marked **B** in the diagram—relatively preserved lung volumes with severely disproportionately reduced DLCO—is the physiologic hallmark of which condition?
A. Usual Interstitial Pneumonia (IPF) alone
B. Acute Respiratory Distress Syndrome (ARDS)
C. Chronic Obstructive Pulmonary Disease (COPD) alone
D. Combined Pulmonary Fibrosis and Emphysema (CPFE)
Explanation
Why Combined Pulmonary Fibrosis and Emphysema (CPFE) is right
The pattern marked B—near-normal or only mildly reduced FVC, FEV1, and TLC (pseudonormalization) coupled with severely reduced DLCO (28% predicted)—is the diagnostic physiologic signature of CPFE as defined by Cottin et al. (Eur Respir J 2005). This discordance occurs because the obstructive physiology of emphysema (hyperinflation, increased RV) counterbalances the restrictive physiology of fibrosis (reduced TLC), producing "pseudonormal" spirometry and lung volumes. However, BOTH disease processes destroy alveolar-capillary surface area, causing DLCO to plummet disproportionately. The clinical presentation—upper-lobe emphysema, lower-lobe UIP-pattern fibrosis, severe pulmonary hypertension, and DLCO/lung-volume discordance—is pathognomonic for CPFE in a heavy smoker.
Why each distractor is wrong
Usual Interstitial Pneumonia (IPF) alone: IPF presents with a restrictive pattern (reduced FVC, reduced TLC, normal or mildly reduced DLCO relative to lung volume). The preserved FVC and TLC here exclude pure IPF; the disproportionate DLCO reduction is due to concurrent emphysema.
Chronic Obstructive Pulmonary Disease (COPD) alone: COPD shows an obstructive pattern (reduced FEV1/FVC ratio, increased TLC/RV). This patient's FEV1/FVC ratio is 79% (preserved), and TLC is near-normal, not elevated—inconsistent with pure emphysema.
Acute Respiratory Distress Syndrome (ARDS): ARDS is an acute, diffuse inflammatory lung injury with bilateral infiltrates and hypoxemia. It does not present with the chronic, compartmentalized (upper-lobe emphysema + lower-lobe fibrosis) pattern or the pseudonormal spirometry seen here.
High-YieldNEET PG
CPFE = "pseudonormal" spirometry + disproportionately reduced DLCO + upper-lobe emphysema + lower-lobe fibrosis + severe pulmonary hypertension in a heavy smoker.
Cottin et al., Eur Respir J 2005; ATS Statement on CPFE
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