Asthma - Clinical Medicine

Introduction

• Asthma is an type of obstructive lung disease.
• Common chief complaints: Dyspnea, wheezing, and sometimes cough.

Key Clinical Features

• Dyspnea: Sensation of shortness of breath.
• Wheezing: Audible on auscultation.
• Hyperresonance: Noted on percussion.
• Cough: May be present due to airway irritation.

Pathophysiology

• Bronchial Wall Edema: Inflammation leads to narrowing of airways.
• Mucus Production: Goblet cells secrete excess mucus, narrowing airways further.
• Bronchoconstriction: Smooth muscle contraction narrows airways.
• Airway Obstruction: Difficulty in air movement causes wheezing, hyperresonance.
• Air Trapping: Causes hyperinflation of lungs.

Triggers

• Allergies: Part of the atopic triad (allergies, dermatitis, asthma).
• Aspirin Sensitivity: Part of Samter’s Triad (asthma, aspirin sensitivity, nasal polyps).
• Other Drugs: Beta-blockers.
• Infections: Usually viral.
• Cold Air & Exercise: Can exacerbate symptoms.

Immune Response

• Dendritic Cells & T Helper Cells: Trigger immune cascade.
• Cytokines & Eosinophils: Lead to bronchoconstriction.
• Mast Cells: Release histamines and leukotrienes, causing inflammation.

Complications

• Respiratory Failure: In severe cases due to CO2 retention (hypercapnia) and oxygen deficiency (hypoxia).
• Nasal Polyps: Associated with aspirin-triggered asthma.
• Type 2 Respiratory Failure: Characterized by high CO2 levels.
• Pulsus Paradoxus: Drop in BP during inspiration due to venous return and ventricular interaction.
• Pneumothorax: Due to hyperinflation and pressure changes.

Diagnosis

• Chest X-ray & ECG: Generally normal; hyperinflation in severe cases.
• ABG: Check for respiratory acidosis in severe exacerbations.
• PFTs: Low FEV1/FVC ratio (<70%) indicates obstruction.
• Methacholine Challenge: Checks for bronchial hyperreactivity.
• Reversibility Test: Improvement with bronchodilators confirms asthma.

Treatment

General Approach

• Beta-2 Agonists: Albuterol for immediate relief.
• Inhaled Corticosteroids: For persistent asthma.
• Leukotriene Receptor Antagonists: For aspirin-sensitive or allergic asthma.
• Omalizumab: For severe allergic asthma.

Stepwise Treatment

• Intermittent Asthma: SABAs PRN.
• Persistent Asthma: Inhaled corticosteroids, LABAs, systemic steroids as severity increases.

Acute Exacerbation

• Bronchodilators: SABAs and SAMAs.
• IV Magnesium: For smooth muscle relaxation.
• Systemic Steroids: For severe inflammation.
• BiPAP Support: To reduce work of breathing and prevent intubation.
• Reduce Anxiety: Consider ketamine for bronchodilation and relaxation.

Conclusion

• Understanding asthma involves recognizing triggers, managing symptoms, and preventing severe complications through a structured treatment plan.