This document discusses the diagnosis and treatment of COPD. It covers spirometry measurements used to diagnose COPD, the GOLD classification system used to assess COPD severity based on lung function tests and symptoms, radiographic findings seen in COPD, the role of HRCT in evaluating COPD patients, tests to measure alpha-1 antitrypsin levels, and how the severity and progression of COPD relates to small airway disease and emphysema.