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Definition
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• Inflammatory condition of the airways
• hyperresponsiveness leading to airway edema + bronchoconstriction • Recurrent/intermittent episodes of wheezing, shortness of breath, and/or cough • Usually reversible either spontaneously or with treatment. |
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Causes
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Atopy (IgE mediated) + Environmental triggers (allergens, irritants, chemicals, respiratory infections, physical stress, and emotional stress).
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Diagnosis
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Reversible bronchoconstriction on own or with bronchodilator and a history. Consider challenge test
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Severity
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Intermittent, mild persistent, moderate persistent, and severe persistent
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Relationships
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• GERD, Allergic rhinitis
• Worsened by Allergic bronchopulmonary aspergillosis (ABPA), Obstructive sleep apnea-hypopnea (OSA), Stress |
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PFT's
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• Normal if no active disease.
• FEV1/FVC < 70% • Decreased expiratory flow • Significant response to beta2-agonist. • Normal or increased TLC (due to hyperinflation). • Normal or reduced VC. • DLCO is normal. |
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Exercise induced bronchospasm
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Decrease in FEV1 of >10% on a treadmill or a stationary bicycle.
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CXR
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Normal in mild cases. Severe asthma shows hyperinflation.
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Arterial Blood Gas
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• Indicated in respiratory distress.
• Hypocarbia from hyperventilation. • Hypoxemia may be present. • If CO2 level is normal or high sign that the patient is decompensating due to fatigue or severe airway obstruction and intubation may be required. |
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Challenge Test
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•Methacholine challenge, histamine challenge, and thermal (cold air). Principle of nonspecific hyperirritability.
•Must both tighten up with the challenge and loosen up with subsequent bronchodilators. • Response to short-acting bronchodilator (increase in the FEV1 > 12% and increase of 200 mL). |
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Rescue
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SABA (albuterol)
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Quick relief (acute, mild, intermittent disease)
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• Short-acting beta2-agonists (SABAs)
• Systemic corticosteroids • Anticholinergics |
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Long-Term control
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• Inhaled corticosteroids (ICS; most potent and most effective)
• Long-acting beta2-agonists (LABAs) • Mast-cell stabilizers (cromolyn sodium +nedocromil) • Leukotriene modifiers • Methylxanthines (theophylline) • Immunomodulators (omalizumab = anti-IgE) |
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Acute Exacerbation
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• Inhaled B agonist and ipratropium via nebulizer or MDI. Assess response clinically and with peak flow.
• IV or oral corticosteroids, then taper when improvement occurs. • Third-line agents include IV magnesium, which helps with bronchospasm in severe refractory cases. • Supplemental oxygen to keep Osat>90%. Antibiotics if necessary. Intubation for respiratory failure. |
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Mild Intermittent
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• Symptoms <2 times per week, nighttime awakenings <2x per month.
• Normal baseline FEV1 and FEV1/FVC. • Needs no long-term control medications, just short acting beta agonist (albuterol). |
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Mild Persistent
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• Symptoms >2 times per week but not every day. 3-4 nighttime awakenings per month, minor limitations on activities.
• Normal PFTs. • Low dose inhaled corticosteroid indicated with PRN albuterol inhaler. |
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Moderate Persistent
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• Daily symptoms with frequent exacerbations.
• FEV1 is 60-80% of expected. • Daily inhaled low dose corticosteroid, PRN albuterol inhaler, and LABA inhaler. +/- cromolyn/methylxanthine/antileukotriene. |
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Severe Persistent
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• Continual symptoms with frequent exacerbations and limited physical activity.
• FEV1 <60% of predicted. • Daily high dose inhaled corticosteroid, PRN albuterol, and long-acting beta agonists. +/- methylxanthine and systemic corticosteroids. |
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• CHF: due to edema of airways and congestion of bronchial mucosa.
• COPD: inflamed airways may be narrowed or bronchospasm may be present. • Asthma: most common cause. • Cardiomyopathy/Pericarditis: can lead to edema around the bronchi. • Lung Cancer: due to obstruction of airways (central tumor or mediastinal invasion). |
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