25
ASTHMA
INTRODUCTION
Pathologic Findings
Description: Asthma (from the Greek for “panting”) is an intermittent or chronic obstructive tracheobronchial condition that is
characterized by wheezing or cough. Adult-onset asthma is more
common in women and poses potential problems during
pregnancy.
Prevalence: Seven percent of the United States population.
Predominant Age: Adults aged 16–40 years (50% of patients are
younger than 10 years).
Genetics: Familial association with reactive airway disease, ectopic
dermatitis, and allergic rhinitis.
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 histologically observed. Biochemical factors related to inflammation mediators include chemical, eosinophil, and neutrophil chemotactic factors, bradykinins,
and others.
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 and viral pneumonitis in infancy.
SIGNS AND SYMPTOMS
•
•
•
•
•
•
•
Shortness of breath
Wheezing and coughing (one or both)
Prolonged exhalation
Decreased breath sounds, hyperresonant chest
Periodic (especially nocturnal) attacks
Cyanosis and tachycardia
Pulsus paradoxus, accessory muscle used for breathing, flattened
diaphragm on chest radiograph or physical examination
Symptoms are usually worse at night and in the early morning. Up
to 40% of asthmatic women of childbearing age may experience
a cyclical exacerbation of asthmatic symptoms during the perimenstrual period.
DIAGNOSTIC APPROACH
Differential Diagnosis
• Recurrent pneumonia
• Chronic bronchitis
• Viral or fungal infection
• Aspiration (foreign body)
• Cystic fibrosis
• Tuberculosis
• Mitral valve prolapse
• Congestive heart failure
• Chronic obstructive pulmonary disease
Associated Conditions: Reflux esophagitis, sinusitis.
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.
56
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 10–20 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 (eg, cold
weather, excessive activity).
Patient Education: Understanding of disease and use of inhalers,
education about triggering factors and allergens.
Drug(s) of Choice
• Cromoglycate and nedocromil
• Steroids (beclomethasone, prednisone)
• β-Agonists (albuterol, bitolterol, salmeterol, terbutaline)
• Methylxanthines (theophylline)
• Anticholinergics (atropine, ipratropium bromide)
• Leukotriene antagonists
Contraindications: Sedatives, mucolytics.
Precautions: β-Agonists should only be intermittently used.
Interactions: Erythromycin and ciprofloxacin slow theophylline
clearance and can increase levels by 15%–20%.
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, 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
25 • Asthma
A. Immunologic
response
C. Cholinergic dominance
B. -adrenergic
blockade
caused by
Antigen
Central
influences?
D. -adrenergic
amine
deficiency
Infection
57
E. Intrinsic
smooth
muscle
defect
Metabolites
Adenyl cyclase
deficiency
Antigenantibody
reaction
Drugs
Block
Reflex
bronchospasm
Vagus
efferent
Sensitized
mast cell
Release of
pharmacologic
mediators
(histamine,
SRS-A, etc.)
Vagus
afferent
Nonantigenic stimuli or
antigenically modulated
stimuli
Block
Direct action
on end-organs
(glands, smooth
muscle, blood
vessels)
Vagus
nerves
Sympathetic
nerves
F. Multiple factors
Figure 25.1 Postulated mechanisms of airway hyperactivity causing asthma
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 (eg, 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.
REFERENCES
LEVEL III
Ali Z, Hansen AV, Ulrik CS. Exacerbations of asthma during pregnancy:
impact on pregnancy complications and outcome. J Obstet Gynaecol.
2015;14:1.
Pregnancy Considerations: Approximately 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 gestation. The effects are highly
variable but may include chronic hypoxia, intrauterine growth
restriction, and (rarely) fetal death.
ICD-10-CM Codes: J45.909 (Unspecified asthma, uncomplicated),
J45.998 (Other asthma).
American College of Obstetricians and Gynecologists. Asthma in pregnancy. ACOG Practice Bulletin No. 90. Obstet Gynecol. 2008;111:457.
(reaffirmed 2014).
Bain E, Pierides KL, Clifton VL, et al. Interventions for managing asthma
in pregnancy. Cochrane Database Syst Rev. 2014;(10):CD010660.