Clinical meaning
Asthma is chronic inflammatory disease driven by Th2 immune response producing IL-4 (IgE switching), IL-5 (eosinophil recruitment), IL-13 (mucus, hyperresponsiveness). IgE cross-linking triggers mast cell degranulation. Stepwise therapy: Step 1-2 = PRN ICS-formoterol; Step 3 = low-dose ICS-LABA; Step 4-5 = medium-high ICS-LABA +/- LAMA +/- biologic.
Diagnosis & workup
Diagnostics & workup: - CT pulmonary angiography for PE evaluation - Methacholine challenge for suspected asthma with normal spirometry - Pulmonary function tests: FEV1, FVC, FEV1/FVC ratio, DLCO - Peak expiratory flow rate monitoring for asthma - Pulse oximetry and continuous SpO2 monitoring - D-dimer (high sensitivity, low specificity for PE) - Sputum culture, Gram stain, and AFB stain
Risk factors: - Childhood asthma with persistent airway hyperreactivity - Radiation therapy to chest - Current or former tobacco use (pack-year calculation) - Age >65 with declining mucociliary clearance - Obesity with restrictive physiology and OSA - GERD with chronic microaspiration - Immunocompromised state increasing pneumonia susceptibility