Asthma

Key Features

Essentials of Diagnosis

• Pathologic features

  • Shedding of airway epithelium

  • Edema

  • Mucus plug formation

  • Mast cell activation

  • Collagen deposition beneath the basement membrane

• The inflammatory cell infiltrate includes eosinophils, lymphocytes, and neutrophils, especially in fatal asthma exacerbations

• Airway inflammation contributes to

  • Airway hyperresponsiveness

  • Airflow limitation

  • Disease chronicity

• Persistent airway inflammation can lead to airway wall remodeling and irreversible changes

General Considerations

• Atopy is the strongest identifiable predisposing factor

• About 40% of infants and young children who have wheezing with viral infections in the first few years of life will have continuing asthma through childhood

• Viral infections (eg, respiratory syncytial virus [RSV], rhinovirus, parainfluenza and influenza viruses, metapneumovirus) are associated with wheezing episodes in young children

• Acetaminophen exposure

  • May increase risk of asthma during prenatal periods, infancy, childhood, and even adulthood

  • Evidence suggests that it increases the risk for subsequent asthma exacerbations or wheeze compared to ibuprofen

• Triggers for asthma

  • Exposure to tobacco smoke

  • Exercise

  • Cold air

  • Pollutants

  • Strong chemical odors

  • Rapid changes in barometric pressure

  • Psychological factors

Demographics

• Most common chronic disease of childhood, affecting over 7 million children in the United States

• Up to 80% of children with asthma develop symptoms before their fifth birthday

• Gender, race, and socioeconomic disparities in the prevalence of asthma exist

  • More boys than girls are affected in childhood

  • Higher percentage affected among black children compared to Hispanic and non-Hispanic white children

  • Children belonging to poor families are more likely to be affected

Clinical Findings

Symptoms and Signs

• Wheezing

• Recurrent cough

• Shortness of breath

• Complaints may include "chest congestion," prolonged cough, exercise intolerance, dyspnea, and recurrent bronchitis or pneumonia

• With severe obstruction, wheezes may not be heard because of poor air movement

• Flaring of nostrils, intercostal and suprasternal retractions, and use of accessory muscles of respiration are signs of severe obstruction

• Cyanosis of the lips and nail beds may be seen with underlying hypoxia

• Tachycardia and pulsus paradoxus also occur

• Agitation and lethargy may be signs of impending respiratory failure

Differential Diagnosis

• Viral bronchiolitis

• Aspiration

• Laryngotracheomalacia

• Vascular rings

• Airway stenosis or web

• Enlarged lymph nodes

• Mediastinal mass

• Foreign body

• Bronchopulmonary dysplasia

• Obliterative bronchiolitis

• Cystic fibrosis

• Vocal cord dysfunction

• Cardiovascular disease

Diagnosis

Laboratory Findings

• Bronchial hyperresponsiveness to nonspecific stimuli is a hallmark of asthma

  • Stimuli include histamine, methacholine, mannitol, exercise, and cold air

  • Mannitol bronchoprovocation is simpler and easier to administer in the office

  • Giving increasing concentrations of a bronchoconstrictive agent to induce a decrease in lung function (usually a 20% drop in forced expiratory volume in 1 second [FEV₁] for histamine and methacholine and a 15% reduction for mannitol) and doing an exercise challenge are ways to determine ...