Obstructive Airway Diseases (Asthma, COPD)

OAD Overview - The Wheezy Foes

• Obstructive Airway Diseases (OADs): Characterized by chronic inflammation and airflow limitation, primarily expiratory. Wheezing is a hallmark symptom.
• Key Types:
  • Asthma: Reversible bronchoconstriction, bronchial hyperresponsiveness, airway inflammation. Often allergic triggers.
  • COPD (Chronic Obstructive Pulmonary Disease): Progressive, largely irreversible airflow limitation. Primarily due to smoking.
    • Chronic Bronchitis: Clinical (cough & sputum).
    • Emphysema: Pathological (alveolar destruction).
• Spirometry: Key diagnostic tool. Shows ↓$FEV_1$, ↓$FEV_1/FVC$ ratio < 0.7.

⭐ Significant reversibility in asthma is defined as an increase in $FEV_1$ by > 12% and > 200ml from baseline after bronchodilator administration.

Pathophysiology - Suffocation Science

Core: Chronic inflammation → Airflow limitation.

Asthma:

• Triggers (allergens/irritants) → Th2-driven eosinophilic inflammation, IgE, mast cells.
• Reversible bronchoconstriction, Airway Hyperresponsiveness (AHR), remodeling (smooth muscle hypertrophy).

COPD:

• Noxious stimuli (smoking) → Neutrophilic inflammation, macrophages, CD8+ T-cells.
• Protease-antiprotease imbalance (↑elastase) → Emphysema.
• Mucus hypersecretion → Chronic bronchitis.
• Largely irreversible airflow limitation.

⭐ In COPD, FEV1/FVC ratio <0.7 post-bronchodilator confirms persistent airflow limitation.

Clinical & Diagnosis - Breathless Clues

• Key Symptoms:
  • Asthma: Episodic wheeze, nocturnal cough, dyspnea. Reversible.
  • COPD: Persistent progressive dyspnea, chronic cough (sputum), exacerbations.
• History Clues:
  • Asthma: Atopy, family Hx, triggers (allergens, exercise).
  • COPD: Smoking (> 10 pack-yrs), age > 40. AATD if young/non-smoker.
• Examination:
  • Both: Wheeze, prolonged expiration, accessory muscles.
  • Asthma: Normal between attacks.
  • COPD: Barrel chest, pursed lips, late cyanosis.
• Diagnostics:
  • Spirometry:
    • Asthma: ↓FEV1/FVC, reversibility (> 12% & 200ml FEV1 ↑ post-BD).
    • COPD: Post-BD FEV1/FVC < 0.7 (persistent).
  • PEFR (Asthma): Diurnal variation > 20%.
  • CXR:
    • Asthma: Often normal; attack hyperinflation.
    • COPD: Hyperinflation, bullae, flat diaphragm.

⭐ Exam Favourite: In asthma, a >12% AND >200ml increase in FEV1 after bronchodilator administration is considered significant reversibility.

Management Principles - Airway Allies

• Goal: Relieve symptoms, prevent exacerbations, improve quality of life.
• Asthma (GINA Guidelines):
  • Relief: As-needed low-dose ICS-Formoterol (preferred for ≥12 yrs) OR SABA.
  • Control: Stepwise approach. Key: Inhaled Corticosteroids (ICS). Add LABA, LAMA, LTRA, Biologics (Omalizumab, Mepolizumab) as needed.
  • Acute Attack: O2, SABA (nebulized), Systemic Steroids. Consider Ipratropium, MgSO4.
• COPD (GOLD Guidelines):
  • Central: Smoking Cessation. Pulmonary Rehabilitation. Vaccinations (Influenza, Pneumococcal).
  • Pharmacotherapy:
    • Bronchodilators: LAMA (Tiotropium) and/or LABA (Salmeterol, Formoterol).
    • ICS: Add to LAMA/LABA if exacerbations (≥2 moderate/yr or ≥1 severe) OR blood eosinophils ≥300 cells/$\mu$L.
  • LTOT: $PaO_{2}$ ≤ 55 mmHg or $SaO_{2}$ ≤ 88%.
• 📌 Inhaler Technique is CRUCIAL for all!

⭐ GINA 2023 recommends as-needed low-dose ICS-formoterol as the preferred reliever for adults and adolescents (≥12 years) with asthma across all severity steps.

High‑Yield Points - ⚡ Biggest Takeaways

• Asthma: Reversible obstruction, eosinophilic inflammation, IgE often involved. COPD: Irreversible obstruction, neutrophilic inflammation, smoking is key cause.
• Spirometry: FEV1/FVC < 0.7 for COPD diagnosis; reversibility points to asthma.
• Treatment cornerstone: ICS for asthma; LABA/LAMA for COPD symptom management.
• Exacerbations: Managed with SABAs, systemic steroids; antibiotics for infective COPD flares.
• Smoking cessation is paramount in COPD. DLCO is typically ↓ in emphysema.