Figure 1.

Matched vs mismatched ventilation/perfusion ($\stackrel{.}{\mathrm{V}}/\stackrel{.}{\mathrm{Q}}$) defects. (A) Matched $\stackrel{.}{\mathrm{V}}/\stackrel{.}{\mathrm{Q}}$ defect due to interstitial lung disease. An 83-year-old man with shortness of breath on exertion. Chest CT showed interstitial lung disease with a basal predominance consistent with usual interstitial pneumonitis. (B) Mismatched defect indicating pulmonary embolism. A 57-year-old man with obesity, hypertension, and OSA presenting with shortness of breath and desaturation with minimal exertion. PA = posteroanterior; LAT = lateral.