In pulmonary edema, where fluid accumulation thickens the alveolar-capillary membrane, what change limits oxygen exchange, reducing arterial oxygen saturation during exercise?

💡 Explanation

Thickening of the alveolar-capillary membrane increases the diffusion distance, impairing the rate of oxygen diffusion across the membrane because Fick's Law of Diffusion dictates that diffusion rate is inversely proportional to distance. Therefore, impaired diffusion limits oxygen exchange during exercise, rather than changes in affinity, cardiac output, or surface tension.

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