Obstructive vs restrictive, the A-a gradient, and how to read a flow-volume loop. A rapid, high-yield review of pulmonary function tests for medical students and exam candidates.
In this episode: • Obstructive — ↓ FEV1/FVC < 0.7 • Restrictive — ↓ FVC, normal/↑ ratio • A-a gradient — normal = age/4 + 4 • ↑ A-a — V/Q mismatch, shunt, diffusion • Normal A-a — hypoventilation, altitude
