Why does supplemental oxygen at high altitude often fail to fully restore arterial oxygen saturation in individuals with advanced emphysema?

💡 Explanation

In emphysema, alveolar wall destruction thickens the diffusion barrier, which impairs oxygen transport into the blood even with high FiO2, because diffusion limitation prevents complete saturation. Therefore, oxygen saturation remains suboptimal, rather than being fully restored as it would be with normal diffusion capacity.

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