Asthma

Asthma

• Chronic inflammatory disease of the airways
• Three components
• Reversible airflow limitation
• Airway hyper-responsiveness to stimuli
• Inflammation of the bronchi

Epidemiology

• Prevalence increasing

Aetiology and precipitating factors

• Atopy and allergy
• Increased airway responsiveness
• Cold air, exercise, pollution
• Occupational, e.g. isocyanates (paint-sprayers)
• Drugs, e.g. NSAIDs, Beta-blockers

Clinical features

• Cough
• Wheeze
• Breathlessness
• Chest tightness

Investigations

• Chest X-ray
• Lung function tests
• Peak flow charts
• Skin testing of allergies

Management

• Self-management plan
• Avoid precipitants
• Stepwise drug treatments
• B2-agonists (short acting and long acting)
• Antimuscarinics
• Anti-inflammatories, e.g. sodium chromoglicate
• Corticosteroids
• Leukotriene antagonists

Stepwise treatment

1. Inhaled short acting B2 agonist as required
2. Add inhaled steroid 200-800 micrograms/day (400 normal)
3. Add inhaled Long acting B2 agonists (LABA) and if it doesn't work stop and up dose of inhaled steroid to 800 micrograms/day, it if it works continue it, and if it works but isn't enough continue it but up dose of inhaled steroid to 800 micrograms'/day. If still inadequate try leukotriene receptor antagonists or SR (sustained release) theophylline
4. Either increase inhaled steroid to 2000 micrograms/day or add a fourth drug such as leukotriene receptor antagonist, SR theophylline, or B2 agonist tablets
5. Refer to specialist care, keep inhaled steroid dosage at 2000 micrograms/day, use LOWEST effective dose of ORAL steroid

Acute severe asthma

• Clinical features
• Inability to complete sentence in one breath
• RR = 25/min
• Tachycardia = 110 bpm
• Peak flow = <50% of predicted normal or best
• Life-threatening features
• Silent chest, cyanosis or feeble respiratory effort
• Exhaustion, confusion, or coma
• Bradycardia or hypotension
• Peak flow <30% of predicted normal or best
• Very severe life-threatening features
• A high PaCO2 > 6 kPa
• A very low PaO2 < 8kPa despite oxygen
• A low and falling arterial pH
• Management
• Reassure the patient and monitor pulse oximetry and arterial blood gases
• Give oxygen 40-60%
• Nebulised B2 agonist e.g. salbutamol 5mg and repeat if no improvement otherwise use 4 hourly
• Add nebulised anti-muscarinics e.g. ipratropium bromide 0.5mg
• Give IV steroids e.g. hydrocortisone 200mg IV every 4 hours
• Exclude pneumothorax on CXR
• If no improvement consider IV infusion of magnesium sulphate or salbutamol and ventilation