Asthma

Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management | Referral

Definition

Asthma is a chronic inflammatory disease of the airways characterised by reversible airflow obstruction, bronchial hyperresponsiveness, and inflammation.

Aetiology

The exact cause is unknown, but it is thought to result from a combination of genetic and environmental factors, such as:

  • Atopy (e.g., eczema, hay fever).
  • Environmental allergens (e.g., dust mites, pollen, mould).
  • Occupational triggers (e.g., fumes, chemicals).
  • Viral respiratory infections.
  • Smoking or second-hand smoke exposure.

Pathophysiology

Asthma involves:

  • Airway inflammation: immune response causing oedema and mucus hypersecretion.
  • Airway hyperresponsiveness: exaggerated narrowing of airways in response to triggers.
  • Airway obstruction: reversible narrowing due to bronchoconstriction and mucus plugging.

Risk factors

  • Personal or family history of atopy.
  • Smoking (active or passive).
  • Occupational exposure to irritants.
  • Obesity.
  • Urban living (pollution exposure).

Signs and symptoms

Symptoms:

  • Wheeze (especially at night or early morning).
  • Shortness of breath.
  • Chest tightness.
  • Intermittent dry cough.

Signs:

  • Audible wheeze on auscultation.
  • Prolonged expiratory phase.
  • Tachypnoea (fast breathing) in acute exacerbations.

Investigations

  • Spirometry: shows reduced FEV₁/FVC ratio (<70%) with reversibility after bronchodilator use.
  • Peak Expiratory Flow (PEF): variability >20% supports asthma diagnosis.
  • Fractional exhaled nitric oxide (FeNO): elevated in airway inflammation.
  • Allergy testing: to identify specific triggers if indicated.

Management

The management of asthma in adults according to my local South East London (SEL) guidelines, please follow your local or national guideline:

Step 1: Low-dose ICS + bronchodilator

  • SABA-free pathway (preferred): Symbicort Turbohaler 200/6 (1 puff as needed).
  • SABA pathway:
    • QVAR 100 (1 puff BD or as needed).
    • Salbutamol (rescue inhaler): 2 puffs as needed.

Step 2: Moderate dose ICS/LABA

  • DPI: Fostair Nexthaler 100/6 (2 puffs BD and 1 as needed).
  • pMDI: Fostair 100/6 (2 puffs BD).

Step 3: High dose ICS/LABA or moderate dose ICS/LABA/LAMA

  • Relvar Ellipta 184/22 (1 puff OD).
  • Fostair Nexthaler 200/6 (2 puffs BD).

Step 4: High dose ICS/LAMA/LABA

  • Fostair Nexthaler 200/6 (2 puffs BD) + Spiriva Respimat (2 puffs OD).

General Recommendations:

  • Review inhaler technique regularly.
  • Consider step down if asthma control is maintained for 3 months.
  • Refer to asthma specialists if symptoms persist despite step 3 or 4.

Referral

  • Urgent referral:
    • Severe exacerbation unresponsive to initial treatment.
    • Frequent hospital admissions.
  • Specialist care referral:
    • Step 3 or 4 management required.
    • Suspected occupational asthma.
 
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