A 50-year-old man Shahid K. John has had increasing dyspnea for the past 3 years with associated occasional cough but little sputum production. Auscultation reveals that his lungs are hyper-resonant and is associated with expiratory wheeze. Pulmonary function tests reveal increased total lung capacity (TLC) and slightly increased FVC. There is decreased FEV1 and FEV1/FVC ratio also. ABG analysis reveals pH of 7.35, pO2 of 60 mm Hg and pCO2 of 48 mm Hg. What is the most likely diagnosis?

The findings of Mr. John point to an obstructive lung disease like emphysema which occurs due to airway narrowing or even from loss of elastic recoil. So, emphysema is the most likely diagnosis. • Sarcoidosis is a chronic restrictive lung disease with all lung volumes decreased, low FVC, and normal FEV1/FVC ratio. • Diffuse alveolar damage is an acute restrictive lung disease. • Chronic pulmonary embolism does not affect FVC because the airways are not affected. It is however associated with a ventilation/perfusion mismatch.