Chapter 5 Asthma
PATHOPHYSIOLOGY
Asthma, also known as reactive airway disease (RAD), is a disease of the lower airway in which there is airway obstruction, airway inflammation, and airway hyperresponsiveness or spasm of the bronchial smooth muscle, increasing mucus formation. Symptoms usually include wheezing, coughing, shortness of breath, a feeling of tightness in the chest, and fatigue, as well as feeding difficulties in very young children. Clients may have retractions, a prolonged expiratory phase, and decreased breath sounds or poor air movement. An exacerbation of asthma may be precipitated by specific allergens (e.g., pollen, mold, animal dander, dust, or cigarette smoke) or by other factors such as weather changes, respiratory infections, exercise, gastroesophageal reflux, or emotional factors. Although the specific cause of asthma is not known, it is well known that the disease may “run in families,” and genetic investigations are underway.
INCIDENCE
1. Asthma affects over 9 million children under the age of 18 in the United States.
2. Asthma is the number one cause of hospitalization for children under the age of 15, with children under the age of 4 having greater admission rates.
3. Asthma accounts for 25% of school absences caused by chronic illness.
CLINICAL MANIFESTATIONS
1. Clinical evidence of airway obstruction—obstruction may be gradual or acute; severity of acute exacerbations is classified as mild intermittent, mild persistent, moderate persistent, or severe persistent
2. Dyspnea with prolonged expiration
3. Expiratory wheezing, progressing to inspiratory and expiratory wheezing, progressing to inaudibility of breath sounds
4. Grunting respirations in infancy
8. Anxiety, irritability, decreasing level of consciousness
10. Drop in arterial partial pressure of carbon dioxide (PaCO2) initially from hyperventilation; then rise in PaCO2 as obstructive process worsens
LABORATORY AND DIAGNOSTIC TESTS
1. White blood cell count—increased with infection
2. Arterial blood gas values (for severe cases)—initially increased pH, decreased PaO2, and decreased PaCO2 (mild respiratory alkalosis from hyperventilation); subsequently decreased pH, decreased arterial partial pressure of oxygen (PaO2), and increased PaCO2 (respiratory acidosis)
3. Eosinophil count—increased in blood, sputum
4. Chest radiographic study—to rule out infection or other cause of worsening respiratory status
5. Pulmonary function tests—decreased tidal volume, decreased vital capacity, decreased maximal breathing capacity
6. Peak flow meter monitoring—decreased peak expiratory flow volumes (less than 50% of personal best during acute episode)
MEDICAL MANAGEMENT
Medical management is targeted at preventing asthma exacerbations by avoiding asthma triggers and by decreasing airway obstruction, inflammation, and reactivity with medications. Medication choices and combinations depend on the severity classifications indicated in the Clinical Manifestations section in this chapter. Medications include corticosteroids (by oral, inhaled, intramuscular [IM], or intravenous [IV] routes) to decrease inflammation, bronchodilators (nebulized form or by metered dose inhaler). Oxygen may be required during an acute episode to maintain adequate levels of oxygenation. The National Asthma Education Prevention Program (NAEPP) recommended in 2002 that young children be placed on a daily preventive medication if they have had more than three episodes of wheezing within the past year and have risk factors of developing asthma. Risk factors include eczema, parent history of asthma, and the presence of two of the following: allergic rhinitis, wheezing with no upper respiratory symptoms, and/or increased eosinophils shown on the complete blood count (CBC). Prevention of exacerbations is the mainstay of treatment of this chronic illness, and two medication classifications have emerged: long-term control and acute control.
Long-Term Control
1. Inhaled corticosteroids—antiinflammatory; either inhaled form or metered dose inhaler (MDI) such as Pulmicort or Flovent
2. Cromolyn sodium and nedocromil—antiinflammatory; inhaled form; used to reduce exercise-induced asthma
3. Long-acting β-agonists—bronchodilator; inhaled form such as Serevent, Foradil, or Advair is used to reduce exercise-induced asthma and nocturnal symptoms
4. Leukotriene receptor antagonist—improve lung function and reduce need for short-acting β2-agonists; oral form such as Singulair
NURSING INTERVENTIONS
Discharge Planning and Home Care
1. Begin client education at time of diagnosis and integrate it with continuing care.
2. Reinforce understanding of asthma.
3. Provide specific instructions about medications, equipment, and adverse effects.
4. Instruct on monitoring signs and symptoms and peak expiratory flow rate, and recognizing indications for treatment modifications.
5. List steps in managing an acute episode of asthma, and instruct on when to seek emergency medical care.
6. Instruct in how to identify asthma triggers and how to avoid, eliminate, or control them.
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