💨 Definition: Obstructive lung diseases are characterised by airflow limitation - especially during expiration - due to narrowed, inflamed, or obstructed airways. The hallmark feature is a reduced expiratory flow rate and an FEV₁/FVC ratio < 70%. These disorders impair gas exchange, increase work of breathing, and cause air trapping and hyperinflation. 🫁⚙️

🌈 Common Types

🚬 Chronic Obstructive Pulmonary Disease (COPD): Progressive, largely irreversible airflow limitation due to chronic bronchitis and/or emphysema. Most commonly caused by smoking.
🌬️ Emphysema: Destruction of alveolar walls → loss of elastic recoil → air trapping and hyperinflation. Classic "pink puffer" phenotype.
💦 Chronic Bronchitis: Productive cough for ≥3 months in 2 consecutive years due to mucus gland hypertrophy. Classic "blue bloater" phenotype.
🌪️ Asthma: Reversible airway obstruction due to bronchial hyperresponsiveness; often allergic or atopic. Episodic wheeze, cough, and chest tightness.
🦠 Bronchiectasis: Irreversible bronchial dilation secondary to chronic infection/inflammation (e.g. post-TB, cystic fibrosis, immunodeficiency).

🩺 Clinical Features

😮‍💨 Dyspnoea: Shortness of breath - progressive in COPD and emphysema, episodic in asthma.
🤧 Cough: Productive in chronic bronchitis and bronchiectasis; dry in asthma or early COPD.
🎵 Wheezing: High-pitched expiratory sound from turbulent flow - hallmark of asthma.
🫀 Chest Tightness: Common in acute asthma or COPD exacerbations.
🌡️ Fatigue, weight loss, and cyanosis: Signs of chronic hypoxia or advanced disease.

🔬 Diagnosis & Investigations

📉 Pulmonary Function Tests (PFTs): ↓ FEV₁, normal/↓ FVC → FEV₁/FVC < 0.70 confirms obstruction. Assess reversibility after bronchodilator.
💨 Bronchodilator Reversibility Test: ≥12% and ≥200 mL improvement in FEV₁ suggests asthma.
🩻 Chest X-ray / CT: Hyperinflation, flattened diaphragm (emphysema); peribronchial thickening (bronchitis); dilated airways (bronchiectasis).
🩸 Arterial Blood Gas (ABG): Detects hypoxia, hypercapnia, or respiratory acidosis in severe disease.
📏 Peak Expiratory Flow (PEF): Useful for asthma monitoring and diurnal variability assessment.
🧬 Special Tests: α₁-antitrypsin levels (early-onset emphysema); sweat chloride test (cystic fibrosis); immunoglobulins (hypogammaglobulinaemia).

📚 Key Disorders and Findings

🩺 Disorder	💡 Clinical Features	🔬 Laboratory / Imaging Findings
Chronic Obstructive Pulmonary Disease (COPD)	Progressive dyspnoea, cough, sputum, smoking history	↓ FEV₁/FVC, air trapping, hyperinflation, possible secondary polycythaemia
Emphysema	Minimal sputum, barrel chest, pursed-lip breathing, weight loss	↑ lung compliance, ↓ DLCO, hyperinflated lungs, flattened diaphragm; α₁-antitrypsin deficiency in some
Chronic Bronchitis	Productive cough ≥3 months/year for ≥2 years, cyanosis (“blue bloater”)	Normal DLCO, thickened bronchi, mucus hypersecretion, mild hypoxia ± hypercapnia
Asthma	Episodic wheeze, cough, chest tightness; often nocturnal or allergen-triggered	Variable obstruction reversible with bronchodilators, eosinophilia, ↑ IgE, hyperinflated lungs during attack
Bronchiectasis	Chronic productive cough, large-volume purulent sputum, crackles, finger clubbing	CT: “tram-track” dilated bronchi, mucus plugging, obstruction ± restriction pattern on PFTs
Immotile Cilia Syndrome (Kartagener’s)	Recurrent sinusitis, bronchiectasis, situs inversus, infertility	Defective dynein arms in cilia (seen on EM)
Hypogammaglobulinaemia	Recurrent chest infections, bronchiectasis, sinusitis	↓ IgG/IgA/IgM levels on serum immunology
Cystic Fibrosis	Chronic cough, sinusitis, bronchiectasis, malabsorption, infertility (males)	↑ Sweat chloride, CFTR gene mutation, ↑ faecal fat, abnormal nasal potential difference

🧭 Management Principles

🚭 Smoking cessation – cornerstone for COPD prevention.
💊 Bronchodilators (β₂-agonists, antimuscarinics) and inhaled corticosteroids to reduce inflammation and improve airflow.
💉 Vaccinations: Annual influenza and pneumococcal vaccines to reduce exacerbations.
🏃‍♀️ Pulmonary rehabilitation: Exercise, breathing retraining, and education to improve quality of life.
💧 Hydration and airway clearance techniques in bronchiectasis.
🩸 Oxygen therapy: For chronic hypoxaemia (PaO₂ ≤ 7.3 kPa or SaO₂ ≤ 88%).
🫀 Monitor for complications: Cor pulmonale, respiratory failure, or pneumothorax.

💡 Teaching Tip: Obstructive = air can’t get out 🌀 (narrowed airways). Restrictive = air can’t get in 🚫 (stiff lungs). Always confirm obstruction with spirometry and assess reversibility with bronchodilators. Early recognition and smoking cessation remain the most powerful interventions. 🌿🫁

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Obstructive Lung Diseases

🌈 Common Types

🩺 Clinical Features

🔬 Diagnosis & Investigations

📚 Key Disorders and Findings

🧭 Management Principles

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