gas exchange
Summary
The process of transferring oxygen from inhaled air into blood and removing carbon dioxide from blood into exhaled air, occurring primarily at the alveolar-capillary membrane. Essential for aerobic metabolism and CO2 elimination.
Detail
Gas exchange occurs across the alveolar-capillary membrane, a thin barrier (~0.5 um) composed of alveolar epithelium, interstitium, and capillary endothelium. Oxygen and carbon dioxide diffuse passively along concentration gradients following Fick's law. Factors impairing gas exchange include: decreased alveolar surface area (emphysema), increased membrane thickness (pulmonary edema, fibrosis), V/Q mismatch (atelectasis, pneumonia), diffusion impairment, and hypoventilation. Assessment includes arterial blood gas analysis and the A-a gradient, which widens when intrinsic lung disease impairs gas exchange.
Sources
- First Aid for the USMLE Step 1
- West's Respiratory Physiology
- Pathoma
- Harrison's Principles of Internal Medicine
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