Chapter 31: Inflammatory Respiratory Disorders

Asthma represents a chronic, reversible obstructive airway disease characterized by bronchial hyperreactivity and immune-mediated inflammation involving Th2 cells, eosinophils, mast cells, and IgE antibodies. The pathophysiology involves bronchoconstriction, airway edema, and mucus production triggered by allergens, infections, or environmental factors, with potential for irreversible airway remodeling if exacerbations are not prevented. Diagnosis relies on spirometry demonstrating at least ten percent improvement in forced expiratory volume after short-acting beta-agonist use, while management follows a stepwise severity-based approach using rescue therapy with bronchodilators and controller therapy with inhaled corticosteroids as first-line anti-inflammatory agents, often combined with long-acting beta-agonists or advanced biologics for severe cases. Chronic obstructive pulmonary disease represents an irreversible, progressive obstructive condition primarily caused by cigarette smoking, encompassing emphysema with alveolar wall destruction and elastic recoil loss, and chronic bronchitis characterized by persistent productive cough and excessive mucus production. The diagnostic hallmark is a forced expiratory volume to forced vital capacity ratio below seventy percent on post-bronchodilator spirometry, with management centered on smoking cessation as the most critical intervention alongside pharmacotherapy combining short and long-acting agents and oxygen therapy as the only mortality-reducing treatment. Interstitial lung disease comprises nearly two hundred distinct disorders causing progressive inflammation and fibrosis of lung parenchyma, classified as restrictive disease with causes ranging from occupational exposures and medications to connective tissue diseases and idiopathic conditions like idiopathic pulmonary fibrosis. The pathophysiology involves dysregulated wound healing, myofibroblast proliferation, and abnormal collagen deposition that reduce lung compliance and impair gas exchange, diagnosed through high-resolution computed tomography imaging showing ground-glass patterns or honeycombing, restrictive pulmonary function test patterns, and often lung biopsy, with management prioritizing identification and removal of causative agents followed by corticosteroid trials, immunosuppressive therapy, antifibrotic medications, and supportive care including potential lung transplantation.