Asthma

Asthma

Asthma is a chronic inflammatory disease of the airways thatcauses airway hyperresponsiveness, mucosal edema, and mucus production. This inflammation ultimately leads to recurrent episodes of asthma symptoms: cough, chest tightness, wheezing, and dyspnea (Fig. 24-6). Estimates show that nearly 17 million Americans have asthma, and more than 5,000 die from this dis-ease annually (Centers for Disease Control and Prevention [CDC], 1998; CDC, 1999; NCHS, 2001). In 1998, asthma ac-counted for over 13.9 million outpatient visits to physician of-fices or hospital clinics and over 2.0 million emergency room visits (NCHS, 2001).

Asthma differs from the other obstructive lung diseases in that it is largely reversible, either spontaneously or with treatment. Pa-tients with asthma may experience symptom-free periods alter-nating with acute exacerbations, which last from minutes to hours or days. Asthma can occur at any age and is the most com-mon chronic disease of childhood. Despite increased knowledge regarding the pathology of asthma and the development of bet-ter medications and management plans, the death rate from asthma continues to increase. For most patients it is a disruptive disease, affecting school and work attendance, occupational choices, physical activity, and general quality of life.

Allergy is the strongest predisposing factor for asthma. Chronic exposure to airway irritants or allergens also increases the risk for developing asthma. Common allergens can be seasonal (eg, grass, tree, and weed pollens) or perennial (eg, mold, dust, roaches, or animal dander). Common triggers for asthma symptoms and exacerbations in patients with asthma include airway irritants (eg, air pollutants, cold, heat, weather changes, strong odors or perfumes, smoke), exercise, stress or emotional upsets, sinusitis with postnasal drip, medications, viral respiratory tract infections, and gastroesophageal reflux. Most people who have asthma are sensitive to a variety of triggers. A patient’s asthma condition will change depending upon the environment, activities, manage-ment practices, and other factors (NHLBI, 1998).

Pathophysiology

The underlying pathology in asthma is reversible and diffuse air-way inflammation. The inflammation leads to obstruction from the following: swelling of the membranes that line the airways (mucosal edema), reducing the airway diameter; contraction of the bronchial smooth muscle that encircles the airways (bron-chospasm), causing further narrowing; and increased mucus pro-duction, which diminishes airway size and may entirely plug the bronchi.

The bronchial muscles and mucus glands enlarge; thick, tena-cious sputum is produced; and the alveoli hyperinflate. Some pa-tients may have airway subbasement membrane fibrosis. This is called airway “remodeling” and occurs in response to chronic in-flammation. The fibrotic changes in the airway lead to airway nar-rowing and potentially irreversible airflow limitation (NIH, 2001; NHLBI, 1998).

Cells that play a key role in the inflammation of asthma are mast cells, neutrophils, eosinophils, and lymphocytes. Mast cells, when activated, release several chemicals called mediators. These chemicals, which include histamine, bradykinin, prostaglandins, and leukotrienes, perpetuate the inflammatory response, causing increased blood flow, vasoconstriction, fluid leak from the vascu-lature, attraction of white blood cells to the area, and broncho-constriction (NHLBI, 1998). Regulation of these chemicals is the aim of much of the current research regarding pharmacologic therapy for asthma.

Further, alpha- and beta₂-adrenergic receptors of the sympa-thetic nervous system are located in the bronchi. When the alpha-adrenergic receptors are stimulated, bronchoconstriction occurs; when the beta₂-adrenergic receptors are stimulated, bronchodilation results. The balance between alpha and beta₂ receptors is con-trolled primarily by cyclic adenosine monophosphate (cAMP). Alpha-adrenergic receptor stimulation results in a decrease in cAMP, which leads to an increase of chemical mediators released by the mast cells and bronchoconstriction. Beta₂-receptor stimulation results in increased levels of cAMP, which inhibits the release of chemical mediators and causes bronchodilation (NHLBI, 1998).

Clinical Manifestations

The three most common symptoms of asthma are cough, dysp-nea, and wheezing. In some instances, cough may be the only symptom. Asthma attacks often occur at night or early in the morning, possibly due to circadian variations that influence air-way receptor thresholds.

An asthma exacerbation may begin abruptly but most fre-quently is preceded by increasing symptoms over the previous few days. There is cough, with or without mucus production. At times the mucus is so tightly wedged in the narrowed airway that the patient cannot cough it up. There may be generalized wheez-ing (the sound of airflow through narrowed airways), first on ex-piration and then possibly during inspiration as well. Generalized chest tightness and dyspnea occur. Expiration requires effort and becomes prolonged. As the exacerbation progresses, diaphoresis, tachycardia, and a widened pulse pressure may occur along with hypoxemia and central cyanosis (a late sign of poor oxygenation). Although life-threatening and severe hypoxemia can occur in asthma, it is relatively uncommon. The hypoxemia is secondary to a ventilation–perfusion mismatch and readily responds to sup-plemental oxygenation.Symptoms of exercise-induced asthma include maximal symp-toms during exercise, absence of nocturnal symptoms, and some-times only a description of a “choking” sensation during exercise.

Asthma is categorized according to symptoms and objective measures of airflow obstruction (Table 24-3) (Expert Panel Re-port II, 1997).

Assessment and Diagnostic Findings

A complete family, environmental, and occupational history is es-sential. To establish the diagnosis, the clinician must determine that periodic symptoms of airflow obstruction are present, air-flow is at least partially reversible, and other etiologies have been excluded. A positive family history and environmental factors, including seasonal changes, high pollen counts, mold, climate changes (particularly cold air), and air pollution, are primarily as-sociated with asthma. In addition, asthma is associated with a va-riety of occupation-related chemicals and compounds, including metal salts, wood and vegetable dust, medications (eg, aspirin, antibiotics, piperazine, cimetidine), industrial chemicals and plas-tics, biologic enzymes (eg, laundry detergents), animal and insect dusts, sera, and secretions. Comorbid conditions that may ac-company asthma include gastroesophageal reflux, drug-induced asthma, and allergic bronchopulmonary aspergillosis. Other pos-sible allergic reactions that may accompany asthma include eczema, rashes, and temporary edema.

During acute episodes, sputum and blood tests may disclose eosinophilia (elevated levels of eosinophils). Serum levels of im-munoglobulin E may be elevated if allergy is present. Arterial blood gas analysis and pulse oximetry reveal hypoxemia during acute at-tacks. Initially, hypocapnia and respiratory alkalosis are present. As the condition worsens and the patient becomes more fatigued, the PaCO₂ may rise. A normal PaCO₂ value may be a signal of im-pending respiratory failure. Because CO₂ is 20 times more dif-fusible than oxygen, it is rare for PaCO₂ to be normal or elevated in a person who is breathing very rapidly. During an exacerbation, the FEV₁ and FVC are markedly decreased but improve with bron-chodilator administration (demonstrating reversibility). Pul-monary function is usually normal between exacerbations.

The occurrence of a severe, continuous reaction is referred to as status asthmaticus and is considered life-threatening (see below).

Prevention

Patients with recurrent asthma should undergo tests to identify the substances that precipitate the symptoms. Possible causes are dust, dust mites, roaches, certain types of cloth, pets, horses, de-tergents, soaps, certain foods, molds, and pollens. If the attacks are seasonal, pollens can be strongly suspected. The patient is in-structed to avoid the causative agents whenever possible.

Knowledge is the key to quality asthma care. Although na-tional guidelines are available for the care of the asthma patient, unfortunately health care providers may not follow them. Failure to follow the guidelines in the following areas has been noted: lack of treatment of patients who have symptoms more than 2 days per week with a regular medication schedule, lack of patient-specific advice on improving the environment and an explanation about the importance of doing so, lack of encouragement for pa-tients to monitor their peak flow measurements with a diary, and lack of written, up-to-date educational materials (Plaut, 2001).

A 1998 survey by a group called “Asthma in America” found that 11% of physicians were unaware of the national asthma guidelines. Only 35% of patients with asthma who were surveyed reported having pulmonary function testing in the past year.

While 83% of physicians reported prescribing peak flow meter monitoring, only 62% of patients had ever heard of a peak flow meter (Rickard & Stempel, 1999). All health care providers caring for asthma patients need to be aware of the national guidelines and use them (Expert Panel Report II, 1997).

Complications

Complications of asthma may include status asthmaticus, respira-tory failure, pneumonia, and atelectasis. Airway obstruction, particularly during acute asthmatic episodes, often results in hy-poxemia, requiring the administration of oxygen and the moni-toring of pulse oximetry and arterial blood gases. Fluids are administered because people with asthma are frequently dehydrated from diaphoresis and insensible fluid loss with hyperventilation.

Medical Management

Immediate intervention is necessary because the continuing and progressive dyspnea leads to increased anxiety, aggravating the situation.

PHARMACOLOGIC THERAPY

Two general classes of asthma medications are long-acting med-ications to achieve and maintain control of persistent asthma and quick-relief medications for immediate treatment of asthma symptoms and exacerbations (Table 24-4). Because the under-lying pathology of asthma is inflammation, control of persistent asthma is accomplished primarily with regular use of anti-inflammatory medications. These medications have systemic side effects when used long term. The route of choice for administra-tion of these medications is the MDI because it allows for topical administration. Critical to the success of inhaled therapy is the proper use of the MDI (see Chart 24-4). If the patient has diffi-culty with this procedure, the use of a spacer device is indicated. Table 24-3 presents a stepwise approach for managing asthma (Expert Panel Report II, 1997). Information on use of the MDI and spacer device is given in the previous section on COPD.

Long-Acting Control Medications. 

Corticosteroids are the mostpotent and effective anti-inflammatory medications currently available. They are broadly effective in alleviating symptoms, im-proving airway function, and decreasing peak flow variability. Initially, the inhaled form is used. A spacer should be used with inhaled corticosteroids and the patient should rinse the mouth after administration to prevent thrush, a common complication of inhaled corticosteroid use. A systemic preparation may be used to gain rapid control of the disease; to manage severe, persistent asthma; to treat moderate to severe exacerbations; to accelerate recovery; and to prevent recurrence (Dhand, 2000).

Cromolyn sodium (Intal) and nedocromil (Tilade) are mild to moderate anti-inflammatory agents that are used more com-monly in children. They also are effective on a prophylactic basis to prevent exercise-induced asthma or in unavoidable exposure to known triggers. These medications are contraindicated in acute asthma exacerbations.

Long-acting beta₂-adrenergic agonists are used with anti-inflammatory medications to control asthma symptoms, partic-ularly those that occur during the night. These agents are also effective for preventing exercise-induced asthma. Long-acting beta₂-adrenergic agonists are not indicated for immediate relief of symptoms.

Methylxanthines (theophylline [Slo-bid, Theo-24, Theo-Dur]) are mild to moderate bronchodilators usually used in addition to inhaled corticosteroids, mainly for relief of nighttime asthma symptoms. There is some evidence that theophylline may have a mild anti-inflammatory effect (NHLBI, 1998).

Leukotriene modifiers (inhibitors) or antileukotrienes are a new class of medications. Leukotrienes are potent bronchocon-strictors that also dilate blood vessels and alter permeability. Leukotriene inhibitors act by either interfering with leukotriene synthesis or blocking the receptors where leukotrienes exert their action (Boushey, Fick, Lazarus & Martin, 2000). At this time, they may provide an alternative to inhaled corticosteroids for mild persistent asthma or may be added to a regimen of inhaled corticosteroids in more severe asthma to attain further control.

In addition, combination products are also available (eg, albuterol/ipratropium [Combivent]) and offer ease of use for the patient.

Quick-Relief Medications. 

Short-acting beta-adrenergic agonistsare the medications of choice for relieving acute symptoms and preventing exercise-induced asthma. They have a rapid onset of action. Anticholinergics (eg, ipratropium bromide [Atrovent]) may bring added benefit in severe exacerbations, but they are used more frequently in COPD patients.

MANAGEMENT OF ASTHMA EXACERBATION

Asthma exacerbations are best managed by early treatment and education of the patient (Expert Panel Report II, 1997). Quick-acting beta-adrenergic medications are first used for prompt relief of airflow obstruction. Systemic corticosteroids may be nec-essary to decrease airway inflammation in patients who fail to re-spond to inhaled beta-adrenergic medications. In some patients, oxygen supplementation may be required to relieve hypoxemia associated with a moderate to severe exacerbation (Expert Panel Report II, 1997). Also, response to treatment may be monitored by serial measurements of lung function.

A written action plan is the most useful tool for the patient (Fig. 24-7). This helps to guide the patient in self-management strategies regarding an exacerbation and also provides instruc-tions regarding recognition of early warning signs of worsening asthma. Patient self-management and early recognition of prob-lems lead to more efficient communication with health care providers regarding an asthma exacerbation (Expert Panel Report II, 1997).

PEAK FLOW MONITORING

Peak flow meters measure the highest airflow during a forced ex-piration (Fig. 24-8). Daily peak flow monitoring is recommended for all patients with moderate or severe asthma because it helps measure asthma severity and, when added to symptom monitor-ing, indicates the current degree of asthma control. The patient is instructed in the proper technique, particularly to give maxi-mal effort. The “personal best” is determined after monitoring peak flows for 2 or 3 weeks after receiving optimal asthma ther-apy. The green (80% to 100% of personal best), yellow (60% to 80%), and red (less than 60%) zones are determined, and specific actions are delineated for each zone, enabling the patient to mon-itor and manipulate his or her own therapy after careful instruc-tion (Expert Panel Report II, 1997). This reinforces compliance, independence, and self-efficacy (Reinke, 2000).

Nursing Management

The immediate nursing care of the patient with asthma depends on the severity of the symptoms. The patient may be treated suc-cessfully as an outpatient if asthma symptoms are relatively mild, or he or she may require hospitalization and intensive care for acute and severe asthma.

The patient and family are often frightened and anxious be-cause of the patient’s dyspnea. Thus, an important aspect of care is a calm approach. The nurse assesses the patient’s respiratory status by monitoring the severity of symptoms, breath sounds, peak flow, pulse oximetry, and vital signs. The nurse obtains a history of allergic reactions to medications before administering medications and identifies the patient’s current use of medica-tions. The nurse administers medications as prescribed and mon-itors the patient’s responses to those medications. Fluids may be administered if the patient is dehydrated, and antibiotic agents may be prescribed if the patient has an underlying respiratory in-fection. If the patient requires intubation because of acute respi-ratory failure, the nurse assists with the intubation procedure, continues close monitoring of the patient, and keeps the patient and family informed about procedures.

PROMOTING HOME AND COMMUNITY-BASED CARE

Teaching Patients Self-Care. 

A major challenge is to implementbasic asthma management principles at the community level (Reinke, 2000). Key issues include education of health care providers, establishment of programs for asthma education (for patients and providers), use of outpatient follow-up care for pa-tients, and a focus on chronic management versus acute episodic care. The nurse is pivotal to achieving all of these objectives.

Patient teaching is a critical component of care for the patient with asthma (Plaut, 2001). Multiple inhalers, different types of inhalers, antiallergy therapy, antireflux medications, and avoid-ance measures are all integral for long-term control. This com-plex therapy requires a patient–provider partnership to determine the desired outcomes and to formulate a plan to achieve those outcomes. The patient then carries out daily therapy as part of self-care management, with input and guidance by the health care provider. Before a partnership can be established, the patient needs to understand the following:

·      The nature of asthma as a chronic inflammatory disease

·       The definition of inflammation and bronchoconstriction

·       The purpose and action of each medication

·       Triggers to avoid, and how to do so

·       Proper inhalation technique

·       How to perform peak flow monitoring (Chart 24-5)

·       How to implement an action plan

·       When to seek assistance, and how to do so

An assortment of excellent educational materials is available from the Expert Panel Report II (1997) and the National Heart, Lung and Blood Institute. 

The nurse should obtain current edu-cational materials for the patient based on the patient’s diagno-sis, causative factors, educational level, and cultural factors.

Continuing Care.

The nurse who has contact with the patient inthe hospital, clinic, school, or office uses the opportunity to as-sess the patient’s respiratory status and ability to manage self-care to prevent serious exacerbations. The nurse emphasizes adherence to the prescribed therapy, preventive measures, and the need to keep follow-up appointments with the primary health care provider. A home visit to assess the home environment for aller-gens may be indicated for the patient with recurrent exacerba-tions. The nurse refers the patient to community support groups. In addition, the nurse reminds the patient and family about the importance of health promotion strategies and recommended health screening.