Asthma, introduction, definition, causes, pathophysiology, classification

Asthma, introduction, definition, causes, pathophysiology, classification, symptoms, diagnosis, prevention and treatment

1. Asthma Archana.k

2. Introduction Definition Causes Classification of Asthma Pathophysiology Symptoms Diagnosis Prevention and Treatment Pharmacological Treatment

3. Introduction and definition Asthma is a chronic inflammatory disorder of the airways associated with variable (usually reversible) airflow obstruction and enhanced bronchial hyper responsiveness to a variety of stimuli. Asthma is characterized by excessive sensitivity of the lungs to various stimuli. There is increasing evidence to suggest genetics play an important role in the etiology of the disease. Many cells plays a major role in the inflammatory response in particular eosinophils, mast cells, macrophages, lymphocytes, neutrophils and epithelial cells.

4. Causes Environmental factors interact with inherited factors to increase the risk of asthma. Environmental triggers range from viral infections and allergies, to irritating gases and particles in the air. Physiological factors that may trigger or increase asthma symptoms include: Viral upper respiratory infections. Heavy exercise. Untreated conditions such as rhinitis(symptoms affecting the nose), sinusitis, and gastroesophageal reflux (GERD). Drugs: NSAIDS such as aspirin Ibuprofen, acetaminophen, naproxen sodium and Ketoprophen; statin drugs (cholesterol reducing medications) and other anti-inflammatory drugs. Stress and strong emotions. Menstrual cycle/hormone changes.

5. Common indoor environmental irritants and allergens that can trigger asthma symptoms or an asthma attack, include: Pet fur or feathers, pet urine, saliva and dander. House-dust mites. Cockroach waste and decomposed body of dead animals. Mold and mildew spores. (leaking plumbing, leaking roof etc.) Tobacco smoke and wood smoke. Perfumes, hairsprays, scented lotions, and cologne. Air fresheners, incense sticks and scented candles. Cleaning solutions, pesticides and paint fumes. Common outdoor environmental irritants and allergens Pollen from trees, grasses and weeds. Mold and mildew spores. (wet rotting leaves on the ground) Changes in humidity (high humidity). Exposure to cold air or hot humid air. Industrial emissions, vehicle or truck exhaust, and other air pollutants such as coal dust.

6. Food allergy: Food allergies involve the body’s immune system reacting to proteins found in food. The body treats these proteins the same way as it would be a disease. Different people react to different types of food Between 2% to 10% of people are affected by food allergies, with a greater percentage occurring in children. Reactions can occur within a few minutes or over a period of several hours. Undiagnosed and untreated, severe attacks can be fatal. Based upon causes, the asthma is divided into two types: 1. Intrinsic Asthma: Usually develop beyond age 40 and have many causes other than exposure to allergens. 2. Extrinsic Asthma: Most commonly develop in childhood and caused by exposure to definite allergens.

7. Classification of Asthma Classification of asthma is based on clinical severity: 1. Mild Intermittent Asthma: Daytime symptoms- Twice a week , night time symptoms- Twice a month Asymptomatic, no long term medications, only short term for quick relief. 2. Mild Persistent Asthma: Daytime symptoms- More than twice a week , night time symptoms-More than twice a month Asymptomatic, abnormal pulmonary tests, daily one medication-daily , quick short relief 3. Moderate Persistent Asthma: Every day and every night symptoms Two medications daily and quick relief daily basis Limited physical activity because attacks are frequent 4. Severe Persistent Asthma: Continued day time, frequent night time symptoms Two medications daily and quick relief Very limited physical activity.

8. Pathophysiology The various common allergens are pollens, dust, mites, some food material and certain drugs which precipitate the asthmatic attack. The allergens upon exposure stimulate production of IgE(immunoglobulins-antibodies produced by the immune system)which further bind to mast cells. Upon re-exposure to same allergen, The said allergens readily bind to IgE and result in degranulation of mast cell to release certain inflammatory mediators such as histamine, leukotrienes, prostaglandins etc. In a response to above changes, WBC’s migrate into the area to engulf the allergens. The phagocytic reaction causes release of basic proteins which are lytic agents for tissue and further promote inflammation.

9. Symptoms Asthma affects the airways, causing them to tighten, become inflamed or to fill with mucus. Asthma symptoms can range from mild to severe. Most people will only experience occasional symptoms, although a few people will have problems most of the time and include: Coughing, especially at night, during exercise or when laughing. Shortness of breath. Chest tightness. Wheezing (a whistling or squeaky sound in chest when breathe, especially while exhaling). Any asthma symptom is serious and can become deadly if left untreated

10. Diagnosis Asthma diagnosis is based on several factors, including a detailed medical history, a physical exam, symptoms and overall health and test results. 1. Medical History and Physical Examination: First step in diagnosing asthma is to look for signs of asthma or allergies. wheezing (high pitched whistling sounds when breathe out) and a runny nose or swollen nasal passages, and allergic skin conditions. 2. Lung Function Tests: The two most common lung function tests used to diagnose asthma are 1. Spirometry 2. Methacholine challenge tests Spirometry: It is a simple breathing test which is of great value for measuring exactly how much bronchial tubes have narrowed Spirometer measures the amount (volume) and speed (flow) of air that can be inhaled and exhaled, giving an indication of how well lungs are performing. It is often used to determine the amount of airway obstruction.

11. 2. Methacholine test: This lung function test for asthma is more commonly used in adults than in children. It might be performed if symptoms and screening spirometry are not clear. Methacholine is an agent that, when inhaled, causes the airways to spasm (contract involuntarily) and narrow if asthma is present. Purpose of the Methacholine Challenge Test is: To identify bronchial hyper responsiveness in people who have normal results To diagnose mild asthma in some atypical cases, such as persistent cough To diagnose occupational (workplace) asthma caused by certain dusts or chemicals. To help determine the risk of developing asthma To evaluate the effectiveness of asthma medications 3. Exhaled Nitric Oxide Test : Easy way to measure inflammation (swelling) in lungs. During inflammation, higher than normal levels of nitric oxide (NO) are released from epithelial cells of the bronchial wall. NO in exhaled breath, can help to identify airway inflammation

12. 4. Allergy Tests: Allergy skin tests are vital in finding out whether asthma is due to inhalant allergens. Drops of a number of allergen extracts are placed on the skin (usually the forearm) and the skin is pricked lightly through the drops. A positive reaction will cause some itching and a bump at the site within 10 minutes.

13. Prevention and Treatment Prevention: Identify and avoid asthma triggers. Identify and treat attacks early and monitor breathing. Other measures include dust free house. Intake of selective type of food. Avoid exposure to extreme cold condition. Get vaccinated for influenza and pneumonia Treatment: The bronchodilators are often considered rescue inhalers, while the other medications are considered. Drug therapy depends on frequency and severity of attacks. 1.Bronchodilators (Sympathomimetics): Bronchodilators bind to the receptors in airway smooth muscle thus causing bronchodilation. e.g. Albuterol, Salbutamol and Terbutaline.

14. 2. Anticholinergic agents : The mechanism of action for anticholinergic agents that decrease or block the actions of acetylcholine on its parasympathetic nervous system receptors on smooth muscle cells. Acetylcholine is a neurotransmitter that contracts smooth muscle. e.g. Ipratropium, Aclidinium. 3. Corticosteroids: The effect of inhaled corticosteroids is reduced airway inflammation. It suppress β- adrenergic receptor action on leukocytes e.g. Beclomethasone, Flunisolide, Triamcinolone. 4. Biologic Response Modifiers (Monoclonal Antibodies): The effect of Biologic Response Modifiers is decreased frequency of allergen induced asthma when the monoclonal antibody binds to IgE, interferes with mast cell binding. This prevents mast cell degranulation and release of inflammatory mediators. E.g. Omalizumab

15. 5 . Leukotriene Receptor Antagonists : The effect of leukotriene receptor antagonists is prevention of allergen induced bronchoconstriction. Antagonism of cysteinyl-leukotriene receptors, thus preventing histamine release. e.g. Montelukast and Zafirlukast. 6. Mast Cell Stabilizers: prevention of bronchoconstriction and inflammation. mast cell stabilizers is to antagonize mast cell degranulation to prevent the release of histamine and other mediators of allergic reaction. e.g. Cromolyn and Nedocromil 7. Methylxanthine Derivatives: Mechanism of action for methylxanthine derivatives is bronchodilation. E.g. Theophylline.