Asthma

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Chapter 14 Asthma

INTRODUCTION

Description: Asthma is an intermittent or chronic obstructive tracheobronchial condition characterized by wheezing or cough. Adult-onset asthma is more common in women and poses potential problems during pregnancy.

Prevalence: Ten percent of the population.

Predominant Age: Adult ages 16 to 40 years (50% of patients are younger than age 10).

Genetics: Familial association with reactive airway disease, ectopic dermatitis, and allergic rhinitis.

ETIOLOGY AND PATHOGENESIS

Causes: Allergic factors (airborne pollens, molds, house dust, animal dander, feather pillows; a 2004 study showed that 71% had more than one allergy and 42% had more than three allergies), smoke or pollutants, viral upper-respiratory infections, aspirin or nonsteroidal antiinflammatory agents, exercise, gastrointestinal reflux.

Risk Factors: Family history, viral pneumonitis in infancy.

DIAGNOSTIC APPROACH

Workup and Evaluation

Laboratory: Complete blood count, arterial blood gases (severe cases).

Imaging: No imaging indicated. (Chest radiograph shows hyperinflation, atelectasis, or air leak, but it is nonspecific.)

Special Tests: Sweat chloride test (childhood), nasal eosinophils, pulmonary function testing (peak expiratory flow rate), allergy testing (selected patients).

Diagnostic Procedures: History, physical examination, pulmonary function testing (forced expiratory volume in 1 second, or FEV1). An excellent office screening test is to ask the patient to blow out a lit match held at arm’s length. Patients with reduced FEV1 are unable to accomplish this task.

Pathologic Findings

Narrowing of large and small airways because of bronchial smooth muscle spasm, edema, and inflammation of the bronchial mucosa with increased mucus production characterize acute attacks. Chronic inflammatory changes are seen histologically. Biochemical factors related to inflammation mediators include chemical, eosinophil, and neutrophil chemotactic factors, bradykinins, and others.

MANAGEMENT AND THERAPY

Nonpharmacologic

General Measures: Evaluation, eliminate irritants, education, caffeine for mild symptoms.

Specific Measures: Mild—intermittent β-agonists via inhaler or cromolyn sodium four times daily plus low-dose inhaled steroids (beclomethasone dipropionate 400 mg/day) may add slow-release xanthines, leukotriene modifiers (montelukast, zafirlukast, pranlukast, and zileuton). Methylxanthines (theophylline and aminophylline), if sufficient control cannot be achieved with inhaled glucocorticoids and long-acting β-agonists alone. Severe—cromolyn sodium plus high-dose inhaled steroids plus theophylline (therapeutic level 10 to 20 mg/mL), inhaled β-agonist to reverse airflow obstruction. During asthma attacks patients should avoid fluid loading, intermittent positive pressure breathing, or airway mist or humidification; these worsen symptoms.

Diet: No specific dietary changes indicated. Avoid known allergens (if any).

Activity: No restriction or restriction based on pulmonary function except for those with exercise-induced asthma (e.g., cold weather, excessive activity).

Patient Education: Understanding of disease and use of inhalers, education about triggering factors and allergens.

Alternative Drugs

Histamine H₁-antagonists, methotrexate.

FOLLOW-UP

Patient Monitoring: Normal health maintenance.

Prevention/Avoidance: Avoid known allergens, aspirin, nonsteroidal antiinflammatory and β-adrenergic blocking drugs. Have a prearranged action plan for acute attacks. Obtain annual influenza immunization. Avoid food additives known to precipitate attacks (sulfites and tartrazine).

Possible Complications: Respiratory failure, atelectasis, and pneumothorax; death. (Mortality increases with more than three emergency visits or more than two hospital admissions per year, nocturnal symptoms, history of intensive care unit admission or mechanical ventilation, steroid dependence, and history of syncope with attacks.)

Expected Outcome: Excellent with careful management.

MISCELLANEOUS

Other Notes: For those with exercise-induced asthma, activities in which the patient breathes large amounts of cold air (e.g., skiing or running) are more likely to provoke an attack, whereas swimming in an indoor, heated pool, with warm, humid air, is less likely to cause problems.

Pregnancy Considerations: Roughly 50% of patients have no change in symptoms, 25% improve, and 25% worsen. Asthma is found in 1% of pregnant patients, 15% of whom have one or more significant attacks during the gestation: the effects are highly variable but may include chronic hypoxia, intrauterine growth restriction, and (rarely) fetal death.

ICD-9-CM Codes: 493.9 (others based on type and cause).

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British Thoracic Society, Scottish Intercollegiate Guidelines Network (SIGN). British Guideline on the Management of Asthma. Guideline No. 63. Edinburgh: SIGN, 2004.

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