Asthma
A chronic lung disease causing episodes of airway narrowing and mucus production, leading to wheezing and shortness of breath. Controlled with daily inhaled steroids.
Emergency Management: Acute severe exacerbation. Management requires immediate O2 targeting SpO2 93-95%, continuous Albuterol nebulization (2.5-5 mg), Ipratropium nebulization, and systemic steroids (Methylprednisolone 125 mg IV or Prednisone 40-50 mg PO). Magnesium sulfate 2g IV over 20 minutes for severe cases. Intubation is a last resort due to risks of barotrauma.
Asthma is a chronic inflammatory disorder of the conducting airways characterized by bronchial hyperresponsiveness, reversible airflow obstruction, and mucosal edema. Driven by various triggers, it causes recurrent episodes of wheezing, breathlessness, chest tightness, and coughing, particularly at night or early in the morning.
Detailed Overview
The pathophysiology of asthma primarily involves type 2 (Th2-driven) inflammation, leading to eosinophilic infiltration, IgE production, and mast cell degranulation. Recurrent inflammation can result in 'airway remodeling'—permanent structural changes including basement membrane thickening and smooth muscle hypertrophy. Diagnosis hinges on demonstrating reversible airflow limitation on spirometry. Treatment has shifted significantly; current GINA guidelines no longer recommend SABA monotherapy, instead advocating for ICS-containing inhalers (like ICS-Formoterol) as the primary reliever to control underlying inflammation and prevent fatal exacerbations.
Epidemiology & Demographics
Affects approximately 339 million people globally. In children, it is more common in boys, but in adults, it is more common in women. Often begins in childhood but can manifest at any age.
Etiological Mechanism
A complex interaction between genetic predisposition (atopy) and environmental exposures. Allergic asthma is driven by allergens (dust mites, pollen, pet dander). Non-allergic triggers include viral respiratory infections, exercise, cold air, and stress.
Primary Causes
Sensitization to environmental allergens in genetically susceptible individuals triggers an IgE-mediated immune response, leading to chronic airway inflammation.
Inhalation of a trigger causes cross-linking of IgE on mast cells, releasing histamine, leukotrienes, and prostaglandins. This causes acute bronchoconstriction. Hours later, a late-phase reaction mediated by Th2 cells, IL-4, IL-5, and IL-13 recruits eosinophils, causing mucosal edema and thick mucus plugging. Over years, chronic inflammation drives airway remodeling, leading to subepithelial fibrosis, smooth muscle hyperplasia, and fixed airflow limitation.
Diagnostic Criteria & Guidelines
Clinical history plus Spirometry: FEV1/FVC ratio < 0.70 demonstrating obstruction, WITH reversibility defined as an increase in FEV1 of > 12% and > 200 mL after administering a short-acting bronchodilator. If baseline spirometry is normal, a methacholine challenge test showing a 20% drop in FEV1 confirms bronchial hyperresponsiveness.
As per GINA guidelines: Low-dose Inhaled Corticosteroid (ICS) + Formoterol (LABA) (e.g., Symbicort 160/4.5 mcg 1-2 puffs) used as both daily maintenance and PRN reliever therapy (SMART therapy). For those on step 2, low dose daily ICS (Fluticasone 44 mcg 2 puffs PO BID) + PRN SABA (Albuterol 90 mcg 2 puffs PRN).
Second-Line & Adjunctive Therapy
For moderate-to-severe asthma: Medium or high-dose ICS/LABA combinations. Add-on therapy includes long-acting muscarinic antagonists (LAMA) like Tiotropium 1.25 mcg 2 puffs daily, or Leukotriene receptor antagonists (Montelukast 10 mg PO daily).
Surgical & Procedural Management
Bronchial thermoplasty: a bronchoscopic procedure delivering radiofrequency energy to the airway walls to reduce smooth muscle mass. Reserved for severe, uncontrolled asthma despite maximal medical therapy.
Patient Counseling & Advice
Thoroughly review inhaler technique; poorly executed technique means medication lands in the mouth instead of the lungs. Prescribe and explain a written Asthma Action Plan (Green, Yellow, Red zones based on Peak Flow).
Follow-Up & Monitoring Schedule
Assess asthma control every 3-6 months using the Asthma Control Test (ACT). Perform spirometry yearly to assess lung function trajectory.
Preventive Strategies
Strict adherence to daily controller medication (ICS) is the primary prevention against life-threatening exacerbations and long-term lung scarring.
Generally excellent with appropriate medical management. Most patients lead entirely normal lives with unrestricted athletic capability. However, severe asthma exacerbations still cause thousands of preventable deaths annually.