Bronchial Asthma - Short Notes for 10 Marks

Definition

• Airway hyper-responsiveness
• Recurrent episodes of wheeze, breathlessness, chest tightness, and cough
• Variable expiratory airflow obstruction
• Obstruction that is usually reversible spontaneously or with treatment.

1. Etiology and Risk Factors

A. Genetic/host factors

• Family history of asthma or atopy
• Atopic dermatitis, allergic rhinitis
• Obesity

B. Environmental triggers

• House dust mite, pollens, animal dander, cockroach allergens
• Viral respiratory infections
• Smoke, air pollution, strong odors
• Cold air and exercise
• Emotional stress

C. Drugs

• Aspirin and other NSAIDs
• Beta-blockers, including eye drops
• Sulfite-containing foods in susceptible individuals

D. Occupational asthma

• Exposure to flour dust, cotton dust, chemicals, paints, latex, animal proteins, etc.

2. Pathogenesis

1. Exposure to allergen activates mast cells, eosinophils, T-lymphocytes, and other inflammatory cells.
2. Release of mediators such as histamine, leukotrienes, and prostaglandins causes:
   • Bronchoconstriction
   • Mucosal edema
   • Increased mucus secretion
3. Repeated inflammation produces airway hyper-responsiveness.
4. Long-standing uncontrolled disease can lead to airway remodeling:
   • Smooth muscle hypertrophy
   • Thickened basement membrane
   • Goblet cell hyperplasia
   • Persistent airflow limitation in some patients.

3. Clinical Features

Symptoms

• Episodic wheeze, especially expiratory
• Breathlessness
• Chest tightness
• Cough, often worse at night or early morning
• Symptoms vary over time and intensity
• Symptoms may occur after exposure to triggers, exercise, cold air, or allergens.

Signs

• Tachypnea and tachycardia
• Prolonged expiration
• Bilateral polyphonic wheeze
• Use of accessory muscles in severe attack
• Hyperinflated chest
• Reduced air entry

Severe/life-threatening features

• Inability to speak full sentences
• Restlessness, exhaustion, confusion, or drowsiness
• Silent chest or markedly reduced breath sounds
• Cyanosis
• Pulsus paradoxus
• Hypotension
• Low oxygen saturation.

4. Diagnosis

Investigations

A. Spirometry

• Obstructive pattern: decreased FEV1/FVC ratio.
• Significant reversibility after bronchodilator supports asthma:
  • Increase in FEV1 by more than 12% and more than 200 mL after inhaled bronchodilator.

B. Peak expiratory flow rate (PEFR)

• Diurnal variability in peak flow supports the diagnosis.
• Useful for home monitoring.

C. Other tests

• Blood eosinophilia may occur.
• Raised serum IgE in allergic asthma.
• Sputum eosinophilia may be present.
• Chest X-ray is usually normal but helps exclude other diseases.
• ABG in severe acute asthma:
  • Early: low PaCO2 due to hyperventilation
  • Normal or raised PaCO2 indicates impending respiratory failure.

5. Differential Diagnosis

• Chronic obstructive pulmonary disease
• Left ventricular failure/cardiac asthma
• Bronchiectasis
• Vocal cord dysfunction
• Foreign body aspiration
• Pulmonary embolism
• Upper airway obstruction
• Gastroesophageal reflux-related cough.

6. Management of Stable Asthma

A. General measures

• Identify and avoid triggers.
• Stop smoking and avoid passive smoking.
• Treat associated allergic rhinitis, sinusitis, obesity, and GERD when relevant.
• Teach correct inhaler technique.
• Provide written asthma action plan.
• Regular assessment of symptom control, inhaler adherence, and lung function.

B. Drugs

1. Reliever therapy

• Inhaled short-acting beta-2 agonist (SABA), e.g., salbutamol, for rapid bronchodilation.
• Overuse suggests poor asthma control.

2. Controller therapy

• Inhaled corticosteroids (ICS) are the main long-term anti-inflammatory treatment.
  • Examples: budesonide, beclomethasone, fluticasone.
• ICS combined with long-acting beta-2 agonist (LABA) for persistent symptoms.
  • Examples: budesonide-formoterol, fluticasone-salmeterol.
• Leukotriene receptor antagonist:
  • Montelukast, especially in allergic asthma or aspirin-sensitive asthma.
• Long-acting muscarinic antagonist:
  • Tiotropium as add-on in selected patients.
• Oral corticosteroids are avoided for long-term use unless severe refractory asthma.
• Biological agents may be used in severe eosinophilic or allergic asthma under specialist care.

7. Management of Acute Severe Asthma

Immediate treatment

1. Oxygen to maintain saturation around 93-95% in adults.
2. Nebulized/inhaled salbutamol, repeated frequently or continuously.
3. Add ipratropium bromide nebulization in severe attacks.
4. Give systemic corticosteroid early:
   • Oral prednisolone if patient can swallow, or
   • Intravenous hydrocortisone if severely ill.
5. Intravenous magnesium sulfate may be used in severe attacks not responding adequately to initial treatment.
6. Monitor:
   • Pulse, respiratory rate, oxygen saturation
   • PEFR/FEV1 where feasible
   • ABG in severe or deteriorating cases.

Indications for ICU/ventilatory support

• Drowsiness, exhaustion, confusion
• Silent chest
• Worsening hypoxemia
• Rising or normal PaCO2
• Respiratory arrest or hemodynamic instability.

8. Complications

• Status asthmaticus
• Acute respiratory failure
• Pneumothorax or pneumomediastinum
• Mucus plugging and atelectasis
• Adverse effects of corticosteroids
• Death in uncontrolled severe asthma.

Conclusion