Shunt fraction calculation: CcO2 = 20, CaO2 = 16, CvO2 = 12. What is Qs/Qt?

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Shunt fraction calculation: CcO2 = 20, CaO2 = 16, CvO2 = 12. What is Qs/Qt?

Shunt fraction measures how much blood bypasses ventilated alveoli, affecting oxygen transfer. It’s calculated with the shunt equation: Qs/Qt = (CcO2 − CaO2) / (CcO2 − CvO2). Here CcO2 is end-capillary oxygen content, CaO2 is arterial oxygen content, and CvO2 is mixed venous oxygen content. Substitute the values: (20 − 16) / (20 − 12) = 4 / 8 = 0.5. So the shunt fraction is 0.5, or 50%. This indicates a large shunt (normal is about 3–5%), given these content values.

Shunt fraction measures how much blood bypasses ventilated alveoli, affecting oxygen transfer. It’s calculated with the shunt equation: Qs/Qt = (CcO2 − CaO2) / (CcO2 − CvO2). Here CcO2 is end-capillary oxygen content, CaO2 is arterial oxygen content, and CvO2 is mixed venous oxygen content.

Substitute the values: (20 − 16) / (20 − 12) = 4 / 8 = 0.5. So the shunt fraction is 0.5, or 50%. This indicates a large shunt (normal is about 3–5%), given these content values.

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