Pathophysiology
Clinical meaning
the clinician must master pulmonary function test interpretation, advanced ventilator management, and evidence-based ARDS protocols. Pulmonary Function Tests (PFTs): • Spirometry: Measures airflow and lung volumes during forced breathing maneuvers. - FVC (Forced Vital Capacity): Total volume exhaled during a forced expiration. Reduced in restrictive disease. - FEV1 (Forced Expiratory Volume in 1 second): Volume exhaled in the first second. Reduced in both obstructive and restrictive disease. - FEV1/FVC Ratio: KEY diagnostic ratio. Normal ≥70% (or ≥LLN). <70% = Obstructive pattern (air trapping prevents rapid exhalation). Normal or elevated = Restrictive pattern (lungs can't fill, but what fills empties quickly). - Bronchodilator Response: ≥12% AND ≥200 mL improvement in FEV1 post-bronchodilator = significant reversibility (supports asthma diagnosis). Minimal/no reversibility supports COPD. • Lung Volumes (measured by body plethysmography or gas dilution): - TLC (Total Lung Capacity): Increased in obstructive disease (hyperinflation/air trapping). Decreased in restrictive disease. - RV (Residual Volume): Air remaining after maximal expiration. Increased in obstructive disease (air trapping). Decreased in restrictive. - FRC (Functional Residual Capacity): Volume at end-expiration during tidal breathing. Increased in emphysema. • DLCO...