Obstructive Lung Disease: Step 1 review notes and self-test
Notes for the Obstructive Lung Disease rapid review: the clue that separates each of its 5 confusion pairs, with timestamps and a self-test.
October 21, 2026
This video covers the clues that separate asthma, COPD, emphysema, bronchitis, and bronchiectasis look-alikes. Watch the video, then use these notes to test yourself.
Asthma vs COPD
Asthma has episodic wheeze, cough, triggers, atopy, and obstruction that reverses by at least 12 percent and 200 mL after a bronchodilator. COPD has chronic progressive dyspnea with a smoking or exposure history and largely fixed obstruction. Both can cause wheeze and an FEV1/FVC below 0.70, so use the post-bronchodilator response to separate them. Asthma-COPD overlap can occur in older smokers with reversibility.
Asthma vs COPD Asthma: obstruction reverses at least 12 percent and 200 mL after a bronchodilator; COPD: largely fixed obstruction. Open the comparison and video →Chronic bronchitis vs Emphysema
Chronic bronchitis is defined by mucus and a productive cough for at least 3 months in each of 2 consecutive years. Emphysema causes alveolar destruction, air trapping, hyperinflation, and reduced DLCO. Most people with COPD have overlapping features, so use the dominant clue of sputum and mucus or alveolar destruction and air trapping.
Chronic bronchitis vs Emphysema Chronic bronchitis is mucus-defined airway disease; emphysema is alveolar destruction with low DLCO and hyperinflation. Open the comparison and video →Centriacinar emphysema vs Panacinar emphysema
Centriacinar emphysema is smoking-related, centered on respiratory bronchioles, and classically affects the upper lobes. Panacinar emphysema is linked to alpha-1 antitrypsin deficiency, involves the entire acinus, and classically affects the lower lobes. Both destroy alveolar walls, so use the risk factor and distribution to separate them.
Centriacinar emphysema vs Panacinar emphysema Centriacinar is smoker upper-lobe bronchiole-centered disease; panacinar is alpha-1 antitrypsin lower-lobe whole-acinus disease. Open the comparison and video →Acute bronchitis vs Chronic bronchitis
Acute bronchitis is a short-term cough from acute bronchial inflammation, usually viral, without pneumonia or a chronic sputum timeline. Chronic bronchitis requires productive cough on most days for at least 3 months per year over 2 consecutive years. Both can cause productive cough, so the strict timeline is the deciding clue. A cough lasting 4 to 6 weeks after a viral upper respiratory infection is still acute bronchitis.
Acute bronchitis vs Chronic bronchitis Acute bronchitis is short-term postinfectious cough; chronic bronchitis is a strict productive-cough duration diagnosis. Open the comparison and video →Non-cystic fibrosis bronchiectasis vs Cystic fibrosis
Non-cystic fibrosis bronchiectasis is permanent bronchial dilation with chronic daily purulent sputum, recurrent infections, hemoptysis, and CT airway widening. Cystic fibrosis is a CFTR disease that causes bronchiectasis with a genetic or sweat chloride finding or a multisystem exocrine pattern. Do not diagnose cystic fibrosis from bronchiectasis alone.
Non-cystic fibrosis bronchiectasis vs Cystic fibrosis Bronchiectasis is the airway damage pattern; cystic fibrosis is a multisystem CFTR cause of bronchiectasis. Open the comparison and video →Quick self-test
Name the diagnosis from the clue, then tap to check.
Alveolar wall destruction with air trapping, hyperinflation, pursed-lip breathing, weight loss, barrel chest, and reduced DLCO.
Emphysema · Chronic bronchitis vs Emphysema
Permanent bronchial dilation with chronic daily purulent sputum, recurrent infections, hemoptysis, and CT airway widening from many possible non-CF causes.
Non-cystic fibrosis bronchiectasis · Non-cystic fibrosis bronchiectasis vs Cystic fibrosis
Chronic progressive dyspnea in a smoker or exposure history with less reversible obstruction.
COPD · Asthma vs COPD
Chronic productive cough for at least 3 months in each of 2 consecutive years, often with mucus plugging, cyanosis, recurrent infections, and pulmonary hypertension risk.
Chronic bronchitis · Chronic bronchitis vs Emphysema
Short-term cough from acute bronchial inflammation, usually viral, without pneumonia and without a chronic sputum timeline.
Acute bronchitis · Acute bronchitis vs Chronic bronchitis
Productive cough for at least 3 months per year over 2 consecutive years, usually in a smoker or COPD context.
Chronic bronchitis · Acute bronchitis vs Chronic bronchitis
Episodic wheeze, cough, triggers, atopy, and reversible airflow obstruction.
Asthma · Asthma vs COPD
CFTR disease with bronchiectasis plus recurrent sinus/lung infections, pancreatic insufficiency, failure to thrive, high sweat chloride, meconium ileus history, or male infertility.
Cystic fibrosis · Non-cystic fibrosis bronchiectasis vs Cystic fibrosis
Keep going
Every pair in this review has a free page in the library with a side-by-side comparison and a practice question. Work through the ones you missed in the self-test first.