Examples of Obstructive Lung Disease
The primary examples of obstructive lung disease include chronic obstructive pulmonary disease (COPD), asthma, bronchiectasis, and emphysema, all characterized by airflow limitation that is not fully reversible.
Major Types of Obstructive Lung Disease
1. Chronic Obstructive Pulmonary Disease (COPD)
COPD is the internationally preferred umbrella term that encompasses several clinical conditions characterized by persistent airflow limitation 1. The diagnosis of COPD is confirmed by spirometry showing a post-bronchodilator FEV1/FVC ratio less than 0.70 1.
Key features of COPD include:
- Chronic and progressive dyspnea
- Chronic cough
- Regular sputum production
- History of exposure to risk factors (primarily smoking)
- Wheezing and chest tightness
2. Emphysema
Emphysema is characterized by permanent destructive enlargement of air spaces, destruction of alveolar walls, and loss of pulmonary elastic recoil 2. It results in:
- Increased lung compliance
- Hyperinflation with increases in residual volume (RV) and total lung capacity (TLC)
- Decreased diffusing capacity (DLCO)
There are three distinct patterns of emphysema 2:
- Centriacinar (Centrilobular) Emphysema
- Panacinar Emphysema
- Paraseptal Emphysema
3. Chronic Bronchitis
Chronic bronchitis is clinically defined as regular sputum production for 3 months or more in 2 consecutive years 1. It involves:
- Inflammation of the bronchi
- Excessive mucus production
- Productive cough
4. Bronchiectasis
Bronchiectasis is characterized by permanent abnormal dilation of bronchi 3. While sometimes listed separately, it belongs to the family of chronic obstructive lung diseases. Key features include:
- Chronic cough
- Daily sputum production
- Recurrent respiratory infections
- Hemoptysis
5. Asthma
Asthma is characterized by variable and recurring symptoms of airflow obstruction that is reversible either spontaneously or with treatment 4. While traditionally separated from COPD, some cases of chronic asthma may be included under the COPD umbrella, particularly when airflow limitation becomes less reversible over time 1.
Diagnostic Criteria
Spirometry is essential for diagnosis of obstructive lung diseases 1, 2:
- FEV1/FVC ratio < 0.70 post-bronchodilator confirms persistent airflow limitation
- Reduced FEV1 (< 80% predicted)
- In emphysema: increased TLC, RV, and FRC, and markedly decreased DLCO
- In asthma: significant reversibility with bronchodilators
Clinical Importance of Distinguishing Between Types
Distinguishing between different types of obstructive lung disease is crucial because 5:
- They differ in their clinical courses
- They have different prognoses
- They require different treatment approaches
For example, asthma typically responds well to anti-inflammatory treatment, while COPD management focuses more on bronchodilation and preventing exacerbations 2.
Common Pitfalls in Diagnosis
- Failure to use spirometry for diagnosis, which is essential for confirming airflow obstruction 1
- Misclassifying elderly patients with fixed airflow limitation as having COPD when they may have long-standing asthma 1
- Not recognizing that some patients have features of multiple obstructive lung diseases (overlap syndromes) 6, 7
- Overlooking bronchiectasis as a cause of chronic cough and sputum production 3
Understanding the specific type of obstructive lung disease is essential for appropriate management and improving patient outcomes in terms of morbidity, mortality, and quality of life 2.