<aside> 🫁 A history of episodic dyspnea and cough that worsens at night and with exercise is highly suggestive of asthma. A normal chest x-ray, normal vital parameters when asymptomatic, and an auscultatory wheeze further support the clinical diagnosis of asthma. A history of other allergies (e.g., peanut allergy) raises suspicion of an atopic predisposition, making allergic, i.e. extrinsic asthma, which typically develops before 7 years of age, a likely diagnosis.

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<aside> 😮‍💨 Shortness of breath and nonproductive cough ≤ 2 times per week and ≤ 2 nights per month with an FEV1 > 80% indicates intermittent asthma, which requires treatment (albuterol inhaler) to prevent asthma attacks and to relieve acute symptoms.

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<aside> 💊 Follow the below treatment algorithm (in order) for managing outpatient asthma (high yield):

1. SABA

2. Low dose ICS

3. LABA

4. Medium dose ICS OR Leukotriene antagonist

5. If medium dose ICS is used increase to high dose OR give oral steroid

   

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Pathogenesis of Asthma

• Asthma is a respiratory disease that is characterized by chronic airway inflammation and manifests with variable respiratory symptoms and expiratory airflow limitation.
• Asthma is a type I hypersensitivity reaction, which involves the triggering of an allergic response via the binding of previously recognized antigen to IgE antibodies on mast cells.  Many type I hypersensitivity reactions are composed of both an early and late phase.
  • Histamine is housed in preformed granules of unactivated mast cells and plays an important role in the early phase of type I hypersensitivity.  Upon activation, mast cells rapidly release histamine via degranulation, making histamine the first chemical mediator to take effect.  Once released, histamine triggers smooth muscle contraction leading to bronchoconstriction, increases vascular permeability leading to edema, and increases mucus secretion from glandular tissue.

Clinical Features, Diagnosis & Management

Typical features:

• Persistent, dry cough that worsens at night, with exercise, or on exposure to triggers/irritants (e.g., cold air, allergens, smoke)
• End-expiratory wheezes
• Dyspnea (shortness of breath)
• Chest tightness
• Prolonged expiratory phase on auscultation
• Hyperresonance to lung percussion
• Features of common comorbid conditions: e.g., atopic conditions like allergic rhinitis or eczema

• Spirometry is the initial test of choice in patients ≥ 6 years of age. Findings of an obstructive lung pattern (↓ FEV1, ↓ FEV1/FVC ratio) that reverses with bronchodilation would confirm a diagnosis of asthma. Spirometry may be attempted in children < 6 years of age, but results are often unreliable. Therefore, diagnosis is largely dependant on a detailed history and the response to a trial of asthma medication.

  • If the diagnosis is still nonconclusive, a methacholine challenge test may be attempted or watchful waiting initiated.
  • Support x-ray is not always indicated and, if done, can be normal in mild cases of asthma or may show evidence of hyperinflation (e.g., flattened diaphragm, wide intercostal spaces).

• Obstructive lung disease — reversible

  • 12% improvement in FEV1 after administration of SABA

  • 20% decrease in FEV1 after methacholine challenge

  • note that asthma is diagnosed by spirometry in children >6 years of age
    • < 6 years → Dx by detailed history

  <aside> 💡 Asthma and COPD both cause an obstructive pattern on PFTs. Complete reversibility of bronchial obstruction after bronchodilator administration rules out COPD.

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