Pathophysiology for Asthma

• Asthma is increased bronchial reactivity in the lower respiratory tract to various stimuli, which produces episodic bronchospasm and airway obstruction and inflammation.
• It is the most common respiratory disease in children. In younger children, it affects twice as many boys as girls and evens out by adolescence.
• Immunologic/allergic reaction results in histamine production causing edema of the mucus membrane, spasm of the smooth muscle of bronchi and bronchioles, and accumulation of secretions.
• Asthma can be intrinsic (allergen is not obvious) or extrinsic (results from sensitivity to specific external allergens).

Etiology:
• Extrinsic asthma: exposure to pollens, animal dander, house dust or mold, feather pillows, silky materials, food additives.
• Intrinsic asthma: irritants, emotional stress, fatigue, endocrine changes, temperature and humidity changes, and exposure to noxious fumes.

Precipitating/risk factors:
• Allergen
• Upper airway infection
• Sudden change in temperature or weather
• Exercise, anxiety, excessive coughing, or laughing

Signs and Symptoms:
• Sudden dyspnea, wheezing, and tightness in the chest
• Coughing that produces thick, clear, or yellow sputum
• Tachypnea and use of accessory respiratory muscles
• Rapid pulse, profuse perspiration, hyperresonant lung fields, diminished breath sounds
• Barrel chest appearance from chronic air trapping
• Irritability from hypoxia

Diagnosis:
• Physical examination
• Chest X-ray: hyperinflated lungs with air trapping and local atelectasis during attacks, normal during remission
• Sputum: presence of Cruschmann’s spirals (casts of airways), eosinophils
• Skin testing for specific allergens may be necessary if the client lacks history of allergy

Treatment:
• Treatment is usually tailored to individual client’s need and focuses on identifying and avoiding predisposing factors. Desensitization of specific antigen may be helpful, but is not effective in persistent asthma.
• Emergency treatment: Oxygen therapy, corticosteroids, and bronchodilators such as subcutaneous epinephrine, IV theophylline, and inhaled agents such as metaproterenol, albuterol, and ipratropium
• Medication:
—Bronchodilators
—Beta-adrenergic agonists: metered does inhaler—children will need spacers, nebulizer—for infants and toddlers, and rescue drugs for acute attacks.
—Corticosteroids: oral for persistent wheezing, inhaled by MDI or nebulizer, IV in the hospital
—Nonsteroidal anti-inflamatory agents: nedocromil, cromolyn sodium, and leukotriene inhibitors
—Other commonly used medications are as follows:
â–  Rapid-acting epinephrine
â–  Aminophylline
â–  Terbutaline
â–  Theophylline
â–  Corticosteroids

Step Approach to Asthma Management
Step 1 Long-term control: none
Rescue (Short-term control): short-acting bronchodilator (inhaled beta 2 agonist); if used more than biw; long-term control required.

Step 2 Long-term control: daily anti-inflammatory: low dose inhaled corticosteroid or cromolyn or nedocromil
Rescue: short-acting bronchodilator (inhaled beta 2 agonist); if used daily or with increased frequency, additional long-term therapy is needed.

Step 3 Long-term control: daily anti-inflammatory: medium dose inhaled corticosteroid or low to medium dose inhaled corticosteroid plus long-acting bronchodilator (inhaled or oral). If needed, medium to high dose inhaled corticosteroid plus long-acting bronchodilator.
Rescue: short-acting bronchodilator (inhaled beta 2 agonist); if used daily or with increased frequency, improved long-term therapy is needed.
—High-dose inhaled corticosteroid plus long-acting inhaled bronchodilator or oral corticosteroid (2 mg/kg/d) and long-acting beta 2 agonist tablets.
—Rescue: inhaled short-acting beta 2 agonist
• Place the client on semi-Fowler’s position
• Administer oxygen
• Encourage diagrammatic breathing
• Administer medication and IV therapy as ordered
• Provide humidification and hydration to loosen secretions
• Monitor for respiratory distress
• Provide chest percussion and postural drainage once symptoms improve
• If the attack was caused by exertion, have the client sit down, rest, and sip warm water if not contraindicated
• For status asthmaticus, humidified oxygen to achieve full saturation; large, frequent doses of inhaled short-acting beta 2 agonists; continuous treatment with bronchodilators until clinical improvement or toxic side effects occur; subcutaneous epinephrine for those refractive to beta 2 agonists