Qs/Qt calculation: Using CcO2 = 20, CaO2 = 16, CvO2 = 12. Result?

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Qs/Qt calculation: Using CcO2 = 20, CaO2 = 16, CvO2 = 12. Result?

Shunt fraction is found with the oxygen content shunt equation: Qs/Qt = (CcO2 − CaO2) / (CcO2 − CvO2). Here CcO2 is the end-capillary oxygen content, CaO2 arterial content, and CvO2 mixed venous content. Plugging in: numerator = 20 − 16 = 4; denominator = 20 − 12 = 8. So Qs/Qt = 4/8 = 0.50. The result is 0.50 (50%). This means half of the mixed venous blood would be matched with alveolar blood lacking complete oxygenation, per the math of the shunt equation. Normal shunt values are much lower, so this indicates a large diffusion or V/Q mismatch in theory.

Shunt fraction is found with the oxygen content shunt equation: Qs/Qt = (CcO2 − CaO2) / (CcO2 − CvO2). Here CcO2 is the end-capillary oxygen content, CaO2 arterial content, and CvO2 mixed venous content.

Plugging in: numerator = 20 − 16 = 4; denominator = 20 − 12 = 8. So Qs/Qt = 4/8 = 0.50.

The result is 0.50 (50%). This means half of the mixed venous blood would be matched with alveolar blood lacking complete oxygenation, per the math of the shunt equation. Normal shunt values are much lower, so this indicates a large diffusion or V/Q mismatch in theory.

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