Asthma (Obstructive Disease)
Definition |
• 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. |
Causes |
Atopy (IgE mediated) + Environmental triggers (allergens, irritants, chemicals, respiratory infections, physical stress, and emotional stress). |
Diagnosis |
Reversible bronchoconstriction on own or with bronchodilator and a history. Consider challenge test |
Severity |
Intermittent, mild persistent, moderate persistent, and severe persistent |
Relationships |
• GERD, Allergic rhinitis
• Worsened by Allergic bronchopulmonary aspergillosis (ABPA), Obstructive sleep apnea-hypopnea (OSA), Stress |
TESTS
PFT's |
• 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 |
Decrease in FEV1 of >10% on a treadmill or a stationary bicycle. |
CXR |
Normal in mild cases. Severe asthma shows hyperinflation. |
Arterial Blood Gas |
• 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. |
Challenge Test |
•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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Treatment
Rescue |
SABA (albuterol) |
Quick relief (acute, mild, intermittent disease) |
• Short-acting beta2-agonists (SABAs)
• Systemic corticosteroids
• Anticholinergics |
Long-Term control |
• 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) |
Acute Exacerbation |
• 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. |
Mild Intermittent |
• 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). |
Mild Persistent |
• 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. |
Moderate Persistent |
• 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. |
Severe Persistent |
• 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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Treatment and Maintenance
Differential Diagnosis of Wheezing
• 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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