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