Asthma is a long-term inflammatory disease of the airways. The tubes that carry air in and out of the lungs become swollen, overly sensitive, and narrow easily. This narrowing causes breathlessness, wheezing, coughing, and chest tightness. The airflow blockage is usually reversible with treatment.
Etiology (Why Asthma Happens)
Asthma develops due to a mix of genetics, environment, and triggers. Some people are born with sensitive lungs, while environmental exposures worsen symptoms. Each person has unique triggers.
Physiological triggers include:
- Viral upper respiratory infections
- Heavy exercise
- Untreated sinusitis, rhinitis, or GERD
- Drugs like aspirin, NSAIDs, ibuprofen, naproxen
- Stress and emotional outbursts
- Hormone changes (e.g., menstrual cycle)
Indoor triggers include:
- Pet hair, fur, feathers, saliva, urine
- Dust mites
- Cockroach droppings
- Mold and mildew
- Tobacco and wood smoke
- Perfumes, hair sprays, strong scents
- Air fresheners, incense sticks
- Cleaning agents and paint fumes
Outdoor triggers include:
- Pollen from trees, grasses, weeds
- Mold from wet leaves
- Weather changes and humidity
- Cold air
- Industrial pollution and vehicle exhaust
- High ozone levels
Food allergies
Certain food proteins can trigger asthma in sensitive individuals. Symptoms may appear within minutes or hours and can be severe if untreated.
Types of Asthma based on cause:
- Intrinsic asthma: Starts after age 40; not usually allergy-related.
- Extrinsic asthma: Childhood onset; triggered by allergens.
Classification of Asthma (Based on severity)
- Mild intermittent: Symptoms ≤2 times/week; nighttime ≤2 times/month.
- Mild persistent: Symptoms >2 times/week but not daily; nighttime >2 times/month.
- Moderate persistent: Daily symptoms; nighttime >1 time/week.
- Severe persistent: Continuous symptoms; frequent nighttime symptoms; limited activity.
Pathophysiology (Simple Explanation)
When an allergen or trigger enters the body, it stimulates the immune system to produce IgE antibodies. These IgE antibodies attach to mast cells. When the trigger enters again, it binds the IgE, causing mast cells to burst and release chemicals like histamine and leukotrienes. These chemicals cause:
- Thick mucus production
- Mucosal swelling
- Constriction of airway smooth muscles
All these changes narrow the airways and make breathing difficult. Air gets trapped, causing hyperinflation, increased breathing effort, and poor oxygen exchange. Severe inflammation can cause long-term airway damage (airway remodeling).
Clinical Manifestations
- Cough (especially at night or during exercise)
- Wheezing — a whistling sound while breathing
- Shortness of breath
- Chest tightness
- Symptoms worsen with allergens, pollutants, or weather changes
- Severe untreated symptoms can be life-threatening
Diagnosis
Diagnosis includes a detailed medical history, physical exam, and tests to rule out other diseases.
Lung Function Tests
- Spirometry: Measures airflow obstruction
- Methacholine challenge: Used when diagnosis is unclear; identifies airway hyperreactivity
- Exhaled Nitric Oxide (FeNO): Measures airway inflammation
Allergy Testing
Skin prick tests or blood tests help identify allergic triggers.
Treatment
Goals of Chronic Asthma Management
- Prevent troublesome symptoms
- Limit rescue inhaler use to ≤2 times/week
- Maintain normal activity and lung function
- Prevent exacerbations and hospitalizations
- Minimize drug side effects
Non-Pharmacological Management
- Patient education and inhaler technique training
- Avoiding known triggers
- Smoking cessation
- Healthy environment with reduced pollutants
- Oxygen therapy for severe acute attacks
- Hydration support
Pharmacological Treatment
1. Bronchodilators (Sympathomimetics)
These relax airway muscles and improve airflow. They act quickly and are known as “rescue inhalers.”
Examples: Salbutamol, Albuterol, Terbutaline
2. Anticholinergics
Block acetylcholine’s effect on airways, preventing bronchoconstriction.
Examples: Ipratropium, Aclidinium
3. Corticosteroids
Reduce airway inflammation and increase responsiveness to bronchodilators.
Examples: Beclomethasone, Flunisolide, Triamcinolone
4. Biologic Agents (Monoclonal Antibodies)
Used for severe allergic asthma; reduce frequency of attacks by blocking IgE.
Example: Omalizumab
5. Leukotriene Receptor Antagonists
Stop leukotriene-mediated bronchoconstriction and inflammation.
Examples: Montelukast, Zafirlukast
6. Mast Cell Stabilizers
Prevent mast cell degranulation and mediator release.
Examples: Cromolyn, Nedocromil
7. Methylxanthines
Work by bronchodilation and reducing inflammatory mediator release.
Example: Theophylline
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