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COPD definition pathophysiology etiology risk factors
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COPD diagnosis spirometry GOLD staging management treatment
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Chronic Obstructive Pulmonary Disease (COPD)
Definition
COPD is a heterogeneous lung condition characterized by chronic respiratory symptoms (dyspnea, cough, sputum production, exacerbations) due to airway and/or alveolar abnormalities that cause persistent, often progressive, airflow obstruction. Defined spirometrically as a post-bronchodilator FEV₁/FVC < 0.70.
Pathophysiology
| Component | Mechanism |
|---|---|
| Emphysema | Destruction of alveolar walls → loss of elastic recoil → air trapping |
| Chronic bronchitis | Mucous gland hypertrophy → excessive mucus → airway narrowing |
| Small airway disease | Inflammation, fibrosis → obstructive ventilatory defect |
| Systemic inflammation | Spillover of pulmonary inflammation → comorbidities (cardiovascular, skeletal muscle wasting) |
Risk Factors
Environmental (GOLD 2025, p. 20):
- Cigarette smoking — primary risk factor; dose-dependent, though <50% of heavy smokers develop COPD
- Significant risk even at <10 pack-years (increased risk of severe exacerbation and early death)
- Biomass fuel/indoor smoke exposure
- Occupational dusts and chemicals
- Air pollution (outdoor)
Host Factors:
- Alpha-1 antitrypsin (AAT) deficiency — most common genetic risk
- Abnormal lung development (premature birth, childhood respiratory infections)
- Aging lungs
- Hyperresponsive airways
An estimated half of all COPD cases worldwide are due to risk factors other than tobacco. (GOLD 2025, p. 20)
Clinical Presentation
Symptoms:
- Progressive dyspnea (initially on exertion)
- Chronic cough (productive or non-productive)
- Sputum production
- Wheezing and chest tightness
- Fatigue, weight loss (advanced disease)
Signs:
- Barrel chest, use of accessory muscles
- Prolonged expiratory phase
- Decreased breath sounds, hyperresonance
- Cyanosis (advanced)
Phenotypes:
| Feature | Emphysema ("Pink Puffer") | Chronic Bronchitis ("Blue Bloater") |
|---|---|---|
| Build | Thin, cachexic | Obese |
| Cyanosis | Absent/late | Present |
| Cough/Sputum | Minimal | Prominent |
| Hypoxia | Mild | Severe |
| PaCO₂ | Low/normal | Elevated |
Diagnosis
Spirometry (required for diagnosis)
- Post-bronchodilator FEV₁/FVC < 0.70 confirms airflow obstruction
- Fixed ratio (not reversible to normal with bronchodilator)
GOLD Spirometric Severity (based on post-BD FEV₁ % predicted)
| GOLD Grade | FEV₁ % Predicted | Severity |
|---|---|---|
| 1 | ≥ 80% | Mild |
| 2 | 50–79% | Moderate |
| 3 | 30–49% | Severe |
| 4 | < 30% | Very Severe |
GOLD ABCD / ABE Assessment
Combines spirometry with symptom burden (mMRC dyspnea scale or CAT score) and exacerbation history:
- Group A — Low symptoms, low exacerbation risk
- Group B — High symptoms, low exacerbation risk
- Group E — High exacerbation risk (≥2 moderate or ≥1 hospitalization/year)
Additional Investigations
- CXR/CT chest: Hyperinflation, flattened diaphragm, bullae (not diagnostic but useful)
- ABG: Assess hypoxemia, hypercapnia in severe disease
- Alpha-1 antitrypsin level: Screen all COPD patients at least once
- CBC: Polycythemia (chronic hypoxemia), eosinophilia (guides ICS use)
- DLCO: Reduced in emphysema
Differential Diagnosis
| Condition | Key Distinguishing Feature |
|---|---|
| Asthma | Reversible obstruction, younger onset, atopy |
| Heart failure | Elevated BNP, cardiomegaly, crackles |
| Bronchiectasis | CT findings, recurrent infections |
| Tuberculosis | Exposure history, upper lobe infiltrates |
| Obliterative bronchiolitis | No smoking history, post-transplant |
Management
Pharmacotherapy (GOLD 2025 / Pharmacotherapy in Stable COPD, p. 2)
Step-wise, guided by GOLD group and blood eosinophil count (BEC):
| Group | Initial Therapy |
|---|---|
| A | Short-acting bronchodilator PRN (SABA or SAMA) |
| B | Long-acting bronchodilator (LABA or LAMA) |
| E | LABA + LAMA (dual bronchodilation); add ICS if BEC ≥300 eosinophils/μL |
Bronchodilators (cornerstone):
- LAMA: Tiotropium, umeclidinium, glycopyrrolate — reduce exacerbations, improve lung function
- LABA: Salmeterol, formoterol, indacaterol
- LABA + LAMA combinations: Superior to monotherapy
Inhaled Corticosteroids (ICS):
- Add to LABA+LAMA in Group E with BEC ≥300 or frequent exacerbations
- Avoid as monotherapy in COPD
- Risk of pneumonia with ICS use
Other Agents:
- Roflumilast (PDE-4 inhibitor): Chronic bronchitis phenotype, severe/very severe COPD, recurrent exacerbations
- Azithromycin (long-term): Reduces exacerbation frequency (monitor for hearing loss, resistance)
- N-acetylcysteine: Modest benefit in reducing exacerbations
Non-Pharmacological (Essential)
- Smoking cessation — single most effective intervention to slow FEV₁ decline
- Pulmonary rehabilitation — improves exercise tolerance, dyspnea, and quality of life
- Vaccinations: Influenza (annual), pneumococcal, COVID-19, RSV, Tdap
- Long-term oxygen therapy (LTOT): PaO₂ ≤55 mmHg or SaO₂ ≤88% — improves survival
- Non-invasive ventilation (NIV/BiPAP): Chronic hypercapnic respiratory failure
- Nutrition support
- Self-management education
Surgical / Interventional
- Lung volume reduction surgery (LVRS): Upper-lobe emphysema + low exercise capacity
- Bronchoscopic lung volume reduction (endobronchial valves): Selected emphysema patients
- Lung transplantation: End-stage, selected candidates
Acute Exacerbations of COPD (AECOPD)
Definition: Acute worsening of respiratory symptoms beyond normal day-to-day variation requiring a change in therapy.
Triggers: Respiratory infections (most common — viral > bacterial), air pollution, non-adherence.
Management:
- Short-acting bronchodilators (SABA ± SAMA) — increase dose/frequency
- Systemic corticosteroids — Prednisone 40 mg/day × 5 days (not longer)
- Antibiotics — if purulent sputum, increased dyspnea + sputum, or requiring mechanical ventilation (azithromycin, doxycycline, amoxicillin-clavulanate)
- Controlled O₂ therapy — target SpO₂ 88–92% (avoid hypercapnia)
- NIV — for acute hypercapnic respiratory failure (pH < 7.35, PaCO₂ > 45)
- Intubation/IMV — if NIV fails or contraindicated
Complications
- Respiratory failure (acute or chronic)
- Pulmonary hypertension → cor pulmonale → right heart failure
- Polycythemia
- Pneumothorax (especially with bullous emphysema)
- Lung cancer (independent risk)
- Depression and anxiety
- Cachexia and skeletal muscle dysfunction
Prognosis
BODE Index predicts mortality (BMI, airflow Obstruction, Dyspnea, Exercise capacity):
- Scores 0–10; higher score = worse prognosis
- Outperforms FEV₁ alone in predicting death
Poor prognostic factors: Low FEV₁, frequent exacerbations, low BMI, severe dyspnea, hypoxemia, pulmonary hypertension, low DLCO.
Sources: GOLD 2025 Global Strategy for Prevention, Diagnosis and Management of COPD (p. 20); Pharmacotherapy in Patients With Stable COPD (p. 2); supplemented with standard clinical knowledge.
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