Bronchial Asthma Overview

Bronchial Asthma

• Asthma is a chronic inflammatory airway disease with periodic attacks, marked by coughing, wheezing, and shortness of breath.
• Three characteristics of asthma are:
  • Reversible airway obstruction, either spontaneously or with treatment
  • Airway hyperresponsiveness to various stimuli
  • Inflammation of the bronchi, causing epithelial damage, oedema, and mucus plugging

Prevalence

• Asthma prevalence has increased over the past 30 years.
• The increase is significant in children and young adults, with up to 15% of this population affected.
• Asthma is more common in developed countries and less prevalent in Far Eastern countries.

Classification

• Extrinsic asthma is caused by external factors, notably allergens, often affecting atopic individuals, especially children and young adults.
• Intrinsic or cryptogenic asthma is when no external cause is identifiable. This difference isn't crucial for diagnosis.

Etiology

• Atopy is a genetic predisposition to allergic diseases, including asthma, allergic rhinitis, and atopic dermatitis.
• Allergy is an exaggerated immune response to a foreign antigen, Regardless of mechanism.

Pathogenesis

• Asthma involves mediators and vascular leakage activated by various mechanisms, with exposure to allergens being a prominent one.
• Airway inflammation is key to asthma severity.

Pathophysiology

• Mast cells increase in asthmatic airways and release powerful mediators (histamine, prostaglandin D2, leukotrienes) that affect smooth muscle and blood vessels, driving the asthmatic response.
• Eosinophils are prevalent in the bronchial wall and secretions of those with asthma, and their numbers/activity are reduced by corticosteroids
• Macrophages and lymphocytes increase in airway and alveolar linings. Macrophages process allergens, and lymphocytes release mediators such as prostaglandins, thromboxanes, leukotrienes, and platelet-activating factor (PAF)
• The asthmatic airway's epithelium is often damaged making it more prone to infections, such as from rhinoviruses.

Symptoms

• Common symptoms include:
  • Labored breathing
  • Wheezing
  • Frequent coughing
  • Allergies
  • Sleep problems
  • Chest pain
  • Feeling tired
  • Episodes of shortness of breath (dyspnea)
  • Nocturnal coughing, can be a presenting symptom.

Investigations

• There's no single definitive test, but investigations include:
  • Lung function tests
  • Blood and sputum tests to detect increased eosinophils
  • Skin-prick tests to identify allergic causes

Treatment

• Control measures for extrinsic asthma include avoiding causative allergens (dust mites, pets, some foods) and avoiding smoking, salicylates, NSAIDs, and beta blockers.
• Medications are broadly classified as:
  • Quick-relief medications for acute symptoms
  • Long-term control medications to prevent future exacerbations
• Common treatment drugs include:
  • Metered-dose inhalers with inhaled steroids
  • Long-acting beta₂-agonists
  • Leukotriene modifiers
  • Other bronchodilators, such as antimuscarinic agents and theophylline preparations.