During strenuous exercise, why does the ventilation-perfusion ratio (V/Q) mismatch sometimes lead to arterial hypoxemia despite increased alveolar ventilation?

💡 Explanation

Hypoxemia can occur during intense exercise because the increased cardiac output reduces the time red blood cells spend in alveolar capillaries. The diffusion limitation across the alveolar-capillary membrane may not allow complete oxygen saturation, therefore, hypoxemia arises rather than full saturation, due to reduced transit time for gas exchange and mismatched V/Q.

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