INTRODUCTION
Asthma, or hyperreactive airway disease, is one of the most common chronic diseases worldwide. Despite recent advances in understanding of the pathophysiology and treatment of asthma, the condition continues to have significant medical and economic impacts worldwide. In 1991, the National Asthma Education and Prevention Program Expert Panel from the US National Institutes of Health issued its first report on the guidelines for the diagnosis and management of asthma. They defined asthma as follows:
Asthma is a chronic inflammatory disorder of the airways in which many cells and cellular elements play a role, in particular, mast cells, eosinophils, T lymphocytes, macrophages, neutrophils, and epithelial cells. In susceptible individuals, this inflammation causes recurrent episodes of wheezing, breathlessness, chest tightness and coughing, particularly at night or in the early morning. These episodes are usually associated with widespread but variable airflow obstruction that is often reversible either spontaneously or with treatment. The inflammation also causes an associated increase in the existing bronchial responsiveness to a variety of stimuli.
The Expert Panel Report 2 was issued in 1997 and further refined effective asthma management based on the following components: (i) objective measures of lung function, (ii) environmental control measures, (iii) comprehensive pharmacologic therapy, and (iv) patient education.
Exercise-induced asthma (EIA), or exercise-induced bronchospasm (see chapter 4), is an asthma variant 3defined as a condition in which exercise or vigorous physical activity triggers acute bronchospasm in persons with heightened airway reactivity. It is observed primarily in persons who are asthmatic, but can also be found in patients with atopy, allergic rhinitis, or cystic fibrosis and even in healthy persons. EIA is often a neglected diagnosis, and the underlying asthma may be silent in as many as 50% of patients, except with exercise.
Asthma occurs in persons of all races worldwide. Although genetic factors are of major importance in determining a predisposition to the development of asthma, environmental factors play a greater role than racial factors in the onset of disease.
Asthma predominantly occurs in boys in childhood, with a male-to-female ratio of 2:1 until puberty, when the male-to-female ratio becomes 1:1. Asthma prevalence is greater in females after puberty, and the majority of adult-onset cases diagnosed in persons older than 40 years occur in females. Boys are more likely than girls to experience a decrease in symptoms by late adolescence.
Asthma prevalence is increased in very young persons and very old persons because of airway responsiveness and lower levels of lung function. Two thirds of all asthma cases are diagnosed before the patient is aged 18 years. Approximately half of all children diagnosed with asthma have a decrease or disappearance of symptoms by early adulthood. The diagnosis of EIA is made more often in children and young adults than in older adults and is related to high levels of physical activity. It can be observed in persons of any age based on the level of underlying airway reactivity and the level of physical exertion.4
PATHOPHYSIOLOGY
The pathophysiology of asthma is complex and involves the following components: (i) airway inflammation, (ii) intermittent airflow obstruction, and (iii) bronchial hyperresponsiveness. The mechanism of inflammation in asthma may be acute, subacute, or chronic, and the presence of airway edema and mucus secretion also contributes to airflow obstruction and bronchial reactivity. Varying degrees of mononuclear cell and eosinophil infiltration, mucus hypersecretion, desquamation of the epithelium, smooth muscle hyperplasia, and airway remodeling and inflammation are present (Fig. 1.1).
Some of the principal cells identified in airway inflammation include mast cells, eosinophils, epithelial cells, 5macrophages, and activated T lymphocytes. T lymphocytes play an important role in the regulation of airway inflammation through the release of numerous cytokines. Other constituent airway cells, such as fibroblasts, endothelial cells, and epithelial cells, contribute to the chronicity of the disease. Other factors, such as adhesion molecules (e.g., selectins, integrins), are critical in directing the inflammatory changes in the airway. Finally, cell-derived mediators influence smooth muscle tone and produce structural changes and remodeling of the airway.
The presence of airway hyperresponsiveness or bronchial hyperreactivity in asthma is an exaggerated response to numerous exogenous and endogenous stimuli. The mechanisms involved include direct stimulation of airway smooth muscle and indirect stimulation by pharmacologically active substances from mediator-secreting cells such as mast cells or nonmyelinated sensory neurons. The degree of airway hyperresponsiveness generally correlates with the clinical severity of asthma.
Airflow obstruction can be caused by a variety of changes, including acute bronchoconstriction, airway edema, chronic mucous plug formation, and airway remodeling. Acute bronchoconstriction is the consequence of immunoglobulin E-dependent mediator release upon exposure to aeroallergens and is the primary component of the early asthmatic response. Airway edema occurs 6 to 24 hours following an allergen challenge and is referred to as the late asthmatic response. Chronic mucous plug formation consists of an exudate of serum proteins and cell debris that may take weeks to resolve. Airway 6remodeling is associated with structural changes due to long-standing inflammation and may profoundly affect the extent of reversibility of airway obstruction.
The pathogenesis of EIA (see Chapter 4) is controversial. The disease may be mediated by water loss from the airway, heat loss from the airway, or a combination of both. The upper airway is designed to keep inspired air at 100% humidity and body temperature at 37°C (98.6°F). The nose is unable to condition the increased amount of air required for exercise, particularly in athletes who breathe through their mouths. The abnormal heat and water fluxes in the bronchial tree result in bronchoconstriction, occurring within minutes of completing exercise. Results from bronchoalveolar lavage studies have not demonstrated an increase in inflammatory mediators. These patients generally develop a refractory period, during which a second exercise challenge does not cause a significant degree of bronchoconstriction. EIA has not been reported to cause death. Morbidity is associated with exercise limitation. This is observed most dramatically in elite athletes with high levels of exercise who may be limited by airway hyperreactivity.
The prevalence rate of severe asthma in industrialized countries ranges from 2 to 10%. Recent trends suggest an increase in both the prevalence and morbidity of the disease, especially in children younger than 6 years. Factors that have been implicated include urbanization, air pollution, passive smoking, and change in exposure to environmental allergens.7
CLINICAL FEATURES
History
A detailed medical history should address (1) whether symptoms are attributable to asthma, (2) whether findings support the likelihood of asthma (e.g., family history), (3) asthma severity, and (4) the identification of possible precipitating factors.
- Symptoms may include the following:
- Cough
- Wheezing
- Shortness of breath
- Chest tightness
- Sputum production
- Decreased exercise tolerance.
- Symptom patterns can vary as follows:
- Perennial versus seasonal
- Continual versus episodic
- Duration, severity, and frequency
- Diurnal variations (nocturnal and early-morning awakenings)
- Precipitating or aggravating factors may include the following:
- Allergens
- Occupation
- Medications
- Exercise.
- Disease development variables include the following:
- Age at onset
- History of injury early in life due to infection or passive smoke exposure
- Progress of disease
- Current response to management
- Comorbid conditions.
- Family history may reveal the following conditions:
- Asthma
- Allergy
- Sinusitis
- Rhinitis.
- Social history may reveal the following conditions:
- Home characteristics
- Smoking
- Workplace or school characteristics
- Educational level
- Employment
- Social support.
- Determine the profile of a typical exacerbation.
- The impact on the patient and family may have involved the following:
- Emergency department visits, hospitalizations, intensive care unit (ICU) admissions, intubations
- Missed days from work or school or activity limitation.
- Assess the patient's disease perception based on the following elements:
- Knowledge of asthma and treatment
- Use of medications
- Coping with mechanisms
- Family support
- Economic resources
The clinical history for EIA (see Chapter 4) is typical of asthma, with symptoms such as cough, wheezing, shortness of breath, and chest pain or tightness. Some individuals also may report sore throat or GI upset.
- Symptoms are usually associated with exercise but may be related to exposure to cold air or other triggers, such as seasonal allergens, pollutants (e.g., sulfur, nitrous oxide, ozone), or upper respiratory infections.
- Initially, airway dilation is noted during exercise. If exercise extends beyond approximately 10 minutes, bronchoconstriction supervenes, resulting in asthma symptoms. If the exercise period is shorter, symptoms may develop up to 5 to 10 minutes after completion of exercise. A higher intensity level of exercise results in a more intense attack. Running produces more symptoms than walking.
- Patients may note symptoms are related to seasonal changes or the ambient temperature and humidity in the environment in which a patient exercises. Cold, dry air generally provokes more obstruction than warm, humid air. Consequently, many athletes have good exercise tolerance in sports such as swimming. Athletes who are more physically fit may not notice the typical symptoms and may only report a reduced or more limited level of endurance.
- Several modifiers in the history should prompt an evaluation for causes other than EIA. While patients may report typical obstructive symptoms, a history of a choking sensation with exercise, inspiratory wheezing, or stridor should prompt an evaluation for evidence of vocal cord dysfunction.
Physical Examination
- General
- Evidence of respiratory distress manifests as increased respiratory rate, increased heart rate, diaphoresis, and use of accessory muscles of respiration.
- Marked weight loss or severe wasting may indicate severe emphysema.
- Pulsus paradoxus: This is an exaggerated fall in systolic blood pressure during inspiration and may occur during an acute asthma exacerbation.
- Depressed sensorium: This finding suggests a more severe asthma exacerbation with impending respiratory failure.
- Chest examination
- End-expiratory wheezing or a prolonged expiratory phase is found most commonly, although inspiratory wheezing can be heard.
- Diminished breath sounds and chest hyperinflation may be observed during acute exacerbations.
- The presence of inspiratory wheezing or stridor may prompt an evaluation for an upper airway obstruction such as vocal cord dysfunction, vocal cord paralysis, thyroid enlargement, or a soft tissue mass (e.g., malignant tumor).
- Upper airway
- Look for evidence of erythematous or boggy turbinates or the presence of polyps from sinusitis, allergic rhinitis, or upper respiratory infection.
- Any type of nasal obstruction may result in worsening of asthma or symptoms of EIA.
- Skin: Observe for the presence of atopic dermatitis, eczema, or other manifestations of allergic skin conditions.
CAUSES
- Factors that can contribute to asthma or airway hyperreactivity may include any of the following:
- Environmental allergens (House dust mites, animal allergens [especially cat and dog], cockroach allergens, and fungi are most commonly reported.)
- Viral respiratory infections
- Exercise; hyperventilation
- Gastroesophageal reflux disease (GERD)
- Chronic sinusitis or rhinitis
- Aspirin or nonsteroidal anti-inflammatory drug hypersensitivity, sulfite sensitivity
- Use of beta-adrenergic receptor blockers (including ophthalmic preparations)
- Obesity
- Environmental pollutants, tobacco smoke
- Occupational exposure
- Irritants such as household sprays and paint fumes
- Emotional factors
- Perinatal factors (Prematurity and increased maternal age increase the risk for asthma; breastfeeding has not been definitely shown to be protective. Both maternal smoking and prenatal exposure to tobacco smoke also increase the risk of developing asthma).
- Factors that contribute to EIA symptoms include the following:
- Exposure to cold or dry air
- Environmental pollutants (e.g., sulfur, ozone)
- Level of bronchial hyper reactivity
- Chronicity of asthma and symptomatic control
- Duration and intensity of exercise
- Allergen exposure in atopic individuals
- Coexisting respiratory infection.
INVESTIGATIONS
- Laboratory studies are not routinely indicated for asthma but may be used to exclude other diagnoses.
- Blood eosinophilia greater than 4% or 300–400/mm3 supports the diagnosis of asthma, but an absence of this finding is not exclusionary. Eosinophil counts greater than 8% may be observed in patients with concomitant atopic dermatitis. This finding should prompt an evaluation for allergic bronchopulmonary aspergillosis, Churg-Strauss syndrome, or eosinophilic pneumonia.
- Total serum immunoglobulin E levels greater than 100 IU are frequently observed in patients experiencing allergic reactions, but this finding is not specific for asthma and may be observed in patients with other conditions (e.g., allergic bronchopulmonary aspergil-losis, Churg-Strauss syndrome). A normal total serum immunoglobulin E level does not exclude the diagnosis of asthma.
- In monitoring of asthma control, the British Thoracic Society recommends using sputum eosinophilia determinations to guide therapy. An improvement in asthma control, a decrease in hospitalizations, and a decrease in exacerbations were noted in those patients in whom sputum-guided therapy was used.
- Exhaled nitric oxide (NO) analysis has been shown to predict airway inflammation and asthmatic control; however, it is technically more complex and not routinely used in the monitoring of patients with asthma.
- In most patients, chest radiography finding are normal or indicate hyperinflation. Findings may help rule out other pulmonary diseases such as allergic bronchopulmonary aspergillosis (ABPA) or sarcoidosis, which can manifest with symptoms of reactive airway disease. Sometimes, it may show complications like pneumothorax and pneumomediastinum (Figs 1.2 and 1.3).
HRCT of thorax demonstrates airtrapping during inspiration (Fig. 1.4) in a patient with asthma. Inspiratory findings are normal. High-resolution CT scan of the thorax obtained during expiration demonstrates a mosaic pattern of lung attenuation in a patient with asthma. Lucent areas (arrows) represent areas of airtrapping (Fig. 1.5). High-resolution CT scan of the thorax demonstrates central bronchiectasis, a hallmark of allergic bronchopulmonary aspergillosis (right arrow), and the peripheral tree-in-bud appearance of centrilobular opacities (left arrow), which represent mucoid impaction of the small bronchioles (Fig. 1.6).14
Fig. 1.2: Posteroanterior chest radiograph demonstrates a pneumomediastinum in bronchial asthma. Mediastinal air is noted adjacent to the anteroposterior window and airtrapping extends to the neck, especially on the right
Fig. 1.3: Lateral chest radiograph demonstrates a pneumomediastinum in bronchial asthma. Air is noted anterior to the trachea
Fig. 1.4: High-resolution CT scan of the thorax obtained during inspiration demonstrates airtrapping in a patient with asthma
Fig. 1.5: High-resolution CT scan of the thorax obtained during expiration demonstrates a mosaic pattern of lung attenuation in a patient with asthma. Lucent areas (arrows) represent areas of airtrapping
Fig. 1.6: High-resolution CT scan of the thorax demonstrates central bronchiectasis and the peripheral tree-in-bud appearance of centrilobular opacities (left arrow), which represent mucoid impaction of the small bronchioles
- Sinus CT scan may be useful to help exclude acute or chronic sinusitis (see Chapter 3) as a contributing factor. In patients with chronic sinus symptoms, a CT scan of the sinuses can also help rule out chronic sinus disease.
- Allergy skin testing is a useful adjunct in individuals with atopy. Results help guide indoor allergen mitigation or help diagnose allergic rhinitis symptoms. Allergy immunotherapy may be beneficial in controlling allergic rhinitis and asthma symptoms for some patients.
- In patients with reflux symptoms and asthma, 24-hour pH monitoring can help determine if GERD is a contributing factor.
- Pulmonary function testing (spirometry)
- Perform spirometry measurements before and after inhalation of a short-acting bronchodilator in all patients in whom the diagnosis of asthma is considered. Spirometry measures the forced vital capacity, the maximal amount of air expired from the point of maximal inhalation, and the FEV1. A reduced ratio of FEV1 to forced vital capacity, when compared with predicted values, demonstrates the presence of airway obstruction. Reversibility is demonstrated by an increase of 12% or 200 ml of FEV1 after administration of a short-acting bronchodilator. Spirometry should be performed on initial assessment and after treatment stabilized the disease and then at least every 1 to 2 years. For grading of severity of asthma, measurement of both FEV1 and Peak Expiratory Flow Rate (PEFR) is essential. The PEFR can be measured in outpatient clinic by Mini Peak Flow Meter (Fig. 1.7).
- The diagnosis of asthma cannot be based on spirometry findings alone because many other diseases are associated with obstructive spirometry indices.
- As a preliminary evaluation for EIA, perform spirometry in all patients with exercise symptoms to determine, if any baseline abnormalities (i.e., the presence of obstructive or restrictive indices) are present.
- Methacholine or histamine-challenge testing:
- Bronchoprovocation testing with either methacholine or histamine is useful when spirometry findings are normal or near normal, especially in patients with intermittent or exercise-induced symptoms. Bronchoprovocation testing helps determine if hyper reactive airways are present and a negative test result usually excludes the diagnosis of asthma.
- Trained individuals should perform this testing in an appropriate facility and in accordance with the guidelines of the American Thoracic Society published in 1999. Methacholine is administered in incremental doses up to a maximum dose of 16 mg/ml, and a 20% decrease in FEV1, up to the 4 mg/ml level, is considered a positive test result for the presence of bronchial hyperresponsiveness. The presence of airflow obstruction with an FEV1 less than 65–70% at baseline is generally an indication to not perform the test.
- Exercise testing
- Exercise spirometry is the standard method for evaluating patients with EIA. Testing involves 196 to 10 minutes of strenuous exertion at 85 to 90% of predicted maximal heart rate and measurement of post-exercise spirometry for 15 to 30 minutes. The defined cutoff for a positive test result is a 15% decrease in FEV1 after exercise.
- Exercise testing may be accomplished in 3 different ways, using cycle ergometry, a standard treadmill test, or free running exercise. This method of testing is limited because laboratory conditions may not subject the patient to the usual conditions that trigger EIA symptoms, and results have a lower sensitivity compared with other methods.
- Eucapnic hyperventilation
- Eucapnic hyperventilation with either cold or dry air is an alternate method of bronchoprovocation testing.
- It has been used to evaluate patients for EIA and has been shown to produce results similar to those of methacholine-challenge testing.
- Peak-flow monitoring (Fig. 1.7)
- Peak-flow monitoring is designed for ongoing monitoring of patients with asthma because the test is simple to perform and the results are a quantitative and reproducible measure of airflow obstruction.
- It can be used for short-term monitoring, exacerbation management, and daily long-term monitoring.
- Results can be used to determine the severity of an exacerbation and to help guide therapeutic decisions.
- Guidelines for the use of peak-flow meters are as follows:
- Advise the patient to use the peak-flow meter upon awakening in the morning before using a bronchodilator.
- Instruct the patient on how to establish a personal best peak expiratory flow (PEF) rate. Patient should measure PEF rate daily between 12 noon and 2 P.M. for 2–3 weeks during asthma under good control. A short course of oral steroid may be useful to establish the best PEF rate.
- Inform the patient that a peak flow of less than 80% of the patient's personal best indicates a need for additional medication and a peak flow below 50% indicates severe exacerbation.
- Advise the patient to use the same peak-flow meter over time.
- Exhaled NO
- The use of exhaled NO as a measurement of airway inflammation has been suggested as a nonspecific marker. Elevated levels of NO have been shown in people with asthma compared with people without asthma, but limited data exist on the applicability of exhaled NO in the diagnosis of asthma.
TREATMENT
The goals for successful management of asthma outlined in the 2002 US National Heart, Lung, and Blood Institute publication “Global Strategy for Asthma Management and Prevention” include the following:21
- Achieve and maintain control of symptoms.
- Prevent asthma exacerbations.
- Maintain pulmonary function as close to normal levels as possible.
- Maintain normal activity levels of patients including exercise.
- Avoid adverse effects from asthma medications.
- Prevent the development of irreversible airflow limitation.
- Prevent asthma mortality.
The long-term outpatient management of asthma should follow the stepwise therapy model based on the Global Initiative for Asthma guidelines. These recommendations were updated during the 1997 National Asthma Education and Prevention Program, the results of which were published by the National Institutes of Health. Management should incorporate 4 treatment components: (i) objective measures of lung function, (ii) environmental control measures and avoidance of risk factors, (iii) comprehensive pharmacologic therapy, and (iv) patient education. Two additional management strategies include management of exacerbations and regular follow-up care. Classify the severity of asthma before treatment, based on symptom prevalence and measurement of lung function. Classification (staging) of severity and treatment options (of chronic asthma) are shown below.
- Stage 1— Mild intermittent asthma (Table 1.1):
- Intermittent symptoms occurring less than once a week
- Brief exacerbations
- Nocturnal symptoms occurring less than twice a month
- Asymptomatic with normal lung function between exacerbations
- FEV1 or PEF rate greater than 80%, with less than 20% variability
- No daily medication needed. Salbutamol 100 µg two puffs to be inhaled when required. Interval between both puffs should be at least two minutes.
- Stage 2 — Mild persistent asthma (Table 1.2):
- Symptoms occurring more than once a week but less than once a day
- Exacerbations affect activity and sleep
- Nocturnal symptoms occurring more than twice a month
- FEV1 or PEF rate greater than 80% predicted, with variability of 20–30%
- Stage 3 — Moderate persistent asthma (Table 1.3):
- Daily symptoms
- Exacerbations affect activity and sleep
- Nocturnal symptoms occurring more than once a week
- FEV1 or PEF rate 60–80% of predicted, with variability greater than 30%.
- Anti-inflammatory, inhaled steroid (medium dose), or inhaled steroid (low-to-medium dose) and long-acting bronchodilator, especially for night time symptoms (either long-acting inhaled beta2-agonist [adult: 2 puffs q12h, child: 1–2 puffs q12h], sustained-release theophylline, or long-acting beta2-agonist tablets) (If needed, give inhaled steroids in a medium-to-high dose).
- Stage 4 — Severe persistent asthma (Table 1.4)
- Continuous symptoms
- Frequent exacerbations
- Frequent nocturnal asthma symptoms
- Physical activities limited by asthma symptoms
- FEV1 or PEF rate less than 60%, with variability greater than 30%
- Anti-inflammatory or inhaled steroid (high dose) and long-acting bronchodilator (either long-acting inhaled beta2-agonist [adult: 2 puffs q12h, child: 1–2 puffs q12h] and sustained-release theophylline or long-acting beta2-agonist tablets and steroid tablets or syrup long term) (Make repeated attempts to reduce systemic steroid and maintain control with high-dose inhaled steroid).
For quick relief, the medications are described in Table 1.5. Criteria to step up or step down the treatment are detailed to achieve the control of symptoms or best possible outcome (Table 1.6).25
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- Refer any patient with difficult-to-control asthma to a pulmonologist or allergist to ensure proper stepwise management of asthma, or refer for further evaluation to help rule out other diagnoses such as vocal cord dysfunction.
- Refer patients to a pulmonologist for evaluation of symptoms consistent with EIA. These patients should undergo either exercise or bronchoprovocation testing to document evidence of airway hyperreactivity and response to exercise.
- Refer patients to an otolaryngologist for treatment of nasal obstruction from polyps, sinusitis, or allergic rhinitis or for the diagnosis of upper airway disorders.
- Refer patients to an allergist or immunologist for skin testing to guide indoor allergen mitigation efforts and consideration of immunotherapy to treat seasonal allergic rhinitis. The use of immunotherapy for the treatment of asthma is controversial.
Diet
No special diets are generally indicated. Food allergy as a trigger for asthma is uncommon. Avoidance of foods is recommended after a double-blind food challenge that yields positive results. Sulfites have been implicated in some severe asthma exacerbations and should be avoided in sensitive individuals.
Activity
- Activity is generally limited by patients’ ability to exercise and their response to medications. No specific limitations are recommended for patients with asthma, although they should avoid exposure to agents that may exacerbate their disease.
- A significant number of patients with asthma also have EIA, and baseline control of their disease should be adequate to prevent exertional symptoms. The ability of patients with EIA to exercise is based on the level of exertion, degree of fitness, and environment in which they exercise.
Inpatient Care
The initial assessment of acute asthma exacerbations should focus on several key areas.
- Perform a functional assessment of airway obstruction with a measurement of the FEV1 or PEF initially to assess the patient's response to treatment.
- Assess the adequacy of arterial oxygen saturation in patients with severe distress.
- Obtain a brief history, to include symptoms, onset of exacerbation, medications, prior emergency department visits, and hospitalizations (including endotracheal intubations).
- Perform a physical examination to assess the severity of the exacerbation, the overall patient status, the presence of other diseases or complications, and to rule out upper airway obstruction.
- Laboratory studies should be considered based on the status of the patient. These and other studies may include arterial blood gas measurement, complete blood cell count, serum theophylline level (if indicated), chest radiograph to assess for complications, and electrocardiograms in patients older than 50 years.
Once the initial assessment is completed, begin treatment based on the severity of the asthma exacerbation.
- Supplemental oxygen should be used in most patients to maintain oxygen saturations greater than 90%.
- Inhaled short-acting beta-agonists are the initial treatment.
- Repetitive or continuous administration by nebulizer
- In the emergency department, 3 treatments every 20–30 minutes as initial therapy
- High-dose (6–12 puffs) beta-agonist by MDI or nebulizer therapy (Nebulizer is most effective with more severe exacerbations.)
- Consider inhaled ipratropium bromide in patients with severe exacerbations.
- Administer systemic corticosteroids early in the course of disease in patients with an incomplete response to beta-agonists. Oral administration is equivalent in efficacy to intravenous administration. Corticosteroids speed the resolution of airway obstruction and prevent a late-phase response.
- Methylxanthines (theophylline) can be considered in patients with severe exacerbations, but their use is controversial.
- Antibiotics should be reserved for patients with fever and purulent sputum or other evidence of pneumonia or sinusitis.
- Aggressive hydration is not recommended for adults.
- Chest physiotherapy, mucolytics, and sedation are not recommended.
Indications for hospitalization are based on findings from the repeat assessment of a patient after the patient receives 3 doses of an inhaled bronchodilator. Base the 29decision on (1) the duration and severity of symptoms, (2) the severity of airflow obstruction, (3) the course and severity of prior exacerbations, (4) medication use and access to medications, (5) the adequacy of support and home conditions, and (6) the presence of psychiatric illness.
In certain situations, admit the patient to the ICU for close observation and monitoring.
- Rapidly worsening asthma or a lack of response to the initial therapy in the emergency department is an indication for ICU admission.
- If patients have confusion, drowsiness, signs of impeding respiratory arrest, or loss of consciousness, they should be admitted to the ICU.
- Impending respiratory arrest, as indicated by hypoxemia (PaO2 < 60 mmHg) despite supplemental oxygen and/or hypercarbia with PaCO2 greater than 45 mmHg, should prompt ICU admission.
- If intubation is required because of the continued deterioration of the patient's condition despite optimal treatment, admit the patient to the ICU.
Outpatient Care
For all patients with asthma, monitoring should be performed on a continual basis based on the following parameters, which helps in the overall management of the disease:
- Monitoring signs and symptoms of asthma: Patients should be taught to recognize inadequate asthma control, and providers should assess control at each visit.
- Monitoring pulmonary function: Regularly perform spirometry and peak-flow monitoring.
- Monitoring quality of life and functional status: Inquire about missed work or school days, reduction in activities, sleep disturbances, or change in caregiver activities.
- Monitoring history of asthma exacerbations: Determine if patients are monitoring themselves to detect exacerbations and if these exacerbations are self-treated or treated by health care providers.
- Monitoring pharmacotherapy: Ensure compliance with medications and usage of short-acting beta-agonists.
- Monitoring patient-provider communication and patient satisfaction.
Stepwise Therapy
The pharmacologic treatment of asthma is based on stepwise therapy (Table 1.7). Medications should be added or decreased as the frequency and severity of the patient's symptoms change.
- Step 1: Intermittent asthma
- A controller medication is not needed.
- The reliever medication is a short-acting beta-agonist and is needed for symptoms on demand (p.r.n).
- Step 2: Mild persistent asthma
- The reliever medication is a short-acting beta-agonist as needed for symptoms.
- Step 3: Moderate persistent asthma
- The controller medication is an inhaled corticosteroid (800–2000 µg) and a long-acting bronchodilator (either beta-agonist or sustained-release theophylline).
- The reliever medication is a short-acting beta-agonist as needed for symptoms.
- Step 4: Severe persistent asthma
- The controller medication is an inhaled corticosteroid (800–2000 µg), a long-acting bronchodilator (beta-agonist and/or theophylline), and long-term oral corticosteroid therapy.
- The reliever medication is a short-acting beta-agonist as needed for symptoms.
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In patients with EIA (see chapter 4), the primary aim of therapy is prophylaxis to prevent acute episodes.
- A warm-up period of 15 minutes is recommended prior to a scheduled exercise event and has been shown to have duration of effect as long as 40 minutes. This approach is not helpful for unscheduled events, prolonged exercise, or elite athletes.
- One of the primary treatments is to ensure good control of the underlying asthma.
- Regularly scheduled medications are generally not indicated for persons with isolated EIA without underlying asthma. Prophylaxis in the form of inhaled medications administered 15–30 minutes prior to exercise is usually required.
- The most commonly used medications are short-acting beta-agonists such as salbutamol. Sodium cromolyn and nedocromil used 30 minutes prior to exercise have also been effective. The use of long-acting beta-agonists such as salmeterol (at least 90 min before exercise) can be effective for repetitive exercise. Newer agents such as the leukotriene antagonists, inhaled heparin, and inhaled furosemide have demonstrated an ability to prevent exercise-induced bronchospasm. Inhaled corticosteroids have a limited role in the treatment of EIA, except to control underlying asthma.
PREVENTION
- Another component of the treatment of asthma is the control of factors contributing to asthma severity.
- Exposure to irritants or allergens has been shown to increase asthma symptoms and cause exacerbations. Clinicians should evaluate patients with persistent asthma for allergen exposures and sensitivity to seasonal allergens. Skin testing results should be used to assess sensitivity to perennial indoor allergens, and any positive results should be evaluated in the context of the patient's medical history.
- All patients with asthma should be advised to avoid exposure to allergens to which they are sensitive, especially in the setting of occupational asthma. Other factors may include the following:
- Environmental tobacco smoke
- Exertion during high levels of air pollution
- Use of beta-blockers
- Avoidance of aspirin and other nonsteroidal anti-inflammatory drugs if the patient is sensitive
- Avoidance of sulfites or other food items/additives to which the patient may be sensitive.
COMPLICATIONS
- The most common complications of asthma include pneumonia, pneumothorax or pneumomediastinum, and respiratory failure requiring intubation in severe exacerbations.
- Risk factors for death from asthma include the following:
- Past history of sudden severe exacerbations, history of prior intubation, or ICU admission
- Two or more hospitalizations or 3 or more emergency department visits in the past year; hospitalization or emergency department visit in the past month
- Use of more than 2 beta-agonist canisters per month
- Current use of systemic corticosteroids or recent taper
- Comorbidity from cardiovascular disease
- Psychosocial, psychiatric, or illicit drug use problems
- Low socioeconomic status or urban residence.
- Complications associated with most medications used for asthma are relatively rare. However, in those patients requiring long-term corticosteroid use, complications may include osteoporosis, immunosuppression, cataracts, myopathy, weight gain, addisonian crisis, thinning of skin, easy bruising, avascular necrosis, diabetes, and psychiatric disorders.
PROGNOSIS
- Approximately half the children diagnosed with asthma in childhood outgrow their disease by late adolescence or early adulthood and require no further treatment.
- Patients with poorly controlled asthma develop long-term changes over time, i.e. with airway remodeling. This can lead to chronic symptoms and a significant irreversible component to their disease.
- Many patients who develop asthma at an older age also tend to have chronic symptoms.
PATIENT EDUCATION
- The “Expert Panel Report 2: Guidelines for the Diagnosis and Management of Asthma” emphasizes the need for patient education about asthma and the establishment of a partnership between patient and clinician in the management of the disease. The key points of education include the following:
- Integrate patient education into every aspect of asthma care.
- All members of the health care team, including nurses, pharmacists, and respiratory therapists, provide education.
- Clinicians teach patients asthma self-management based on basic asthma facts, self-monitoring techniques, the role of medications, inhaler use, and environmental control measures.
- Develop treatment goals for the patient and family.
- Develop a written, individualized, daily self-management plan.
- Encourage adherence by the patient.
- The most important factor in the diagnosis of asthma is to recognize exacerbating factors or other diagnoses that may affect the treatment of the disease.
- Sinusitis: Of patients with asthma, 50% have concurrent sinus disease. Sinusitis is the most important exacerbating factor for asthma symptoms. Either acute infectious sinus disease or chronic inflammation may contribute to worsening of airway symptoms. Treatment of nasal and sinus inflammation reduces airway reactivity. Treatment 36of acute sinusitis requires at least 10 days of antibiotics to improve asthma symptoms.
- Gastroesophageal reflux disease: Patients with asthma are 3 times more likely to also have GERD. Treatment with proton pump inhibitors, antacids, or H2 blockers may improve asthma symptoms or unexplained chronic cough. The treatment of asthma with agents such as theophylline may lower esophageal sphincter tone and induce GERD symptoms.
- Respiratory infections: Viral respiratory infections have not been shown to cause asthma but can aggravate chronic asthma symptoms or induce symptoms in patients with allergic rhinitis. Rhinoviruses are the principal triggers of wheezing and worsening of asthma in older children and adults, but all viral respiratory infections are associated with increased asthma symptoms.
- Aspirin-induced asthma: The triad of asthma, aspirin sensitivity, and nasal polyps affects 5 to 10% of patients with asthma. Most patients experience symptoms during the third to fourth decade. A single dose can provoke an acute asthma exacerbation, accompanied by rhinorrhea, conjunctival irritation, and flushing of the head and neck. It can also occur with other nonsteroidal anti-inflammatory drugs and is caused by an increase in eosinophils and cysteinyl leukotrienes after exposure. Primary treatment is avoidance of these medications, but leukotriene antagonists have 37shown promise in treatment, allowing these patients to take daily aspirin for cardiac or rheumatic disease.
- Vocal cord dysfunction: Paradoxical inspiratory closure of the vocal cords may mimic asthma. Patients with symptoms of inspiratory wheezing or those whose asthma is refractory to standard therapy should be evaluated for evidence of vocal cord dysfunction. Usually, the diagnosis can be made by direct laryngoscopy, but only during symptomatic periods or exercise. The presence of flattening of the inspiratory limb of the flow-volume loops may also suggest vocal cord dysfunction but is only seen in 20% of patients at baseline.
- Occupational asthma: Occupational factors are associated with 10% of adult asthma cases. More than 300 specific occupational agents have been associated with asthma. High-risk jobs include farming, painting, janitorial work, and plastics manufacturing. Two types of occupational asthma are recognized. Immune-mediated asthma has a latency of months to years after exposure. Non-immune-mediated asthma or irritant-induced asthma (reactive airway dysfunction syndrome) has no latency period and may occur within 24 hours of an accidental exposure to high concentrations of respiratory irritants. Pay careful attention to the patient's occupational history. Those with a history of asthma who report 38worsening of symptoms during the week and improvement during the weekends should be evaluated for occupational exposure. Peak-flow monitoring during work for 2 weeks and a similar period away from work is one recommended method to establish the diagnosis.
SPECIAL CONCERNS
Nocturnal Asthma
- A large percentage of patients with asthma experience nocturnal symptoms once or twice a month. Some patients only experience symptoms at night and have normal pulmonary function in the daytime. This is due, in part, to the exaggerated response to the normal circadian variation in airflow.
- Bronchoconstriction is highest between the hours of 4:00 am and 6:00 pm (the highest morbidity and mortality from asthma is observed during this time). These patients may have a more significant decrease in cortisol levels or increased vagal tone at night. Studies also show an increase in inflammation compared with controls and with patients with daytime asthma.
- Inhaled corticosteroids and long-acting theophyllines have demonstrated the most benefit. Long-acting beta-agonists and leukotriene antagonists have also been shown to improve symptoms.
Pregnancy
- With the exception of alpha-adrenergic compounds other than pseudoephedrine and some antihistamines, most drugs used to treat asthma and allergic rhinitis have not been shown to increase any risk to the mother or fetus. The National Institute of Health stated that salbutamol, cromolyn, beclomethasone, budesonide, prednisone, and theophylline, when clinically indicated, are considered appropriate for the treatment of asthma in pregnancy.
- Poorly controlled asthma can result in low birth weight, increased prematurity, and increased perinatal mortality.
Surgery
- Complications associated with surgery include acute bronchoconstriction resulting from intubation, impaired cough, hypoxemia, hypercapnia, atelectasis, respiratory infection, and exposure to latex.
- The likelihood of these complications occurring depends on the severity of the underlying asthma, the type of surgery (thoracic and upper abdominal), and the type of anesthesia.
- If evidence of airflow obstruction (< 80% of baseline values) is present, a brief course of corticosteroids is recommended. Patients who have received oral corticosteroids for an asthma exacerbation in the past 6 months should receive systemic corticosteroids in the perioperative period.