COPD and asthma pathophysiology, spirometry patterns, and distinguishing clinical features tested on USMLE Step 1.
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- What FEV1/FVC ratio pattern defines obstructive lung disease?
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A reduced FEV1/FVC ratio (below the lower limit of normal, roughly under 0.7)- What is the approximate normal FEV1/FVC ratio in a healthy adult?
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About 0.8 (80%)- How does total lung capacity (TLC) change in obstructive lung disease?
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TLC increases due to air trapping- How does residual volume (RV) change in obstructive lung disease?
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RV increases due to air trapping- What happens to DLCO in emphysema?
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DLCO decreases because alveolar wall and capillary destruction reduces gas exchange surface area- What happens to DLCO in chronic bronchitis?
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DLCO is typically normal- What happens to DLCO in asthma?
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DLCO is normal or even increased- In asthma, a bronchodilator response is considered positive when FEV1 increases by at least ____.
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12% and 200 mL- Does airflow obstruction in COPD fully reverse with bronchodilators?
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No, obstruction in COPD is only partially reversible or irreversible- What is the clinical definition of chronic bronchitis?
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Productive cough for at least 3 months per year for 2 consecutive years- What is emphysema?
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Permanent enlargement of airspaces distal to the terminal bronchiole with destruction of alveolar walls- What is the main risk factor for centriacinar (centrilobular) emphysema?
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Cigarette smoking- Which lung zones are predominantly affected in centriacinar emphysema?
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The upper lobes- What is the main cause of panacinar (panlobular) emphysema?
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Alpha-1 antitrypsin deficiency- Which lung zones are predominantly affected in panacinar emphysema?
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The lower lobes
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