If CcO2 = 20, CaO2 = 15, CvO2 = 12, what is Qs/Qt?

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Multiple Choice

If CcO2 = 20, CaO2 = 15, CvO2 = 12, what is Qs/Qt?

The question is about calculating the shunt fraction using the oxygen content shunt equation. Qs/Qt represents the portion of the cardiac output that bypasses ventilated alveoli, and it’s found from the difference between end-capillary oxygen content and arterial content, relative to the difference between end-capillary content and mixed venous content. Use Qs/Qt = (CcO2 − CaO2) / (CcO2 − CvO2). With CcO2 = 20, CaO2 = 15, CvO2 = 12, the numerator is 20 − 15 = 5, and the denominator is 20 − 12 = 8. So Qs/Qt = 5/8 = 0.625, or 62.5%. A zero value would mean no shunting (all blood participating in gas exchange), while a higher value indicates more blood bypassing ventilated alveoli.

The question is about calculating the shunt fraction using the oxygen content shunt equation. Qs/Qt represents the portion of the cardiac output that bypasses ventilated alveoli, and it’s found from the difference between end-capillary oxygen content and arterial content, relative to the difference between end-capillary content and mixed venous content.

Use Qs/Qt = (CcO2 − CaO2) / (CcO2 − CvO2). With CcO2 = 20, CaO2 = 15, CvO2 = 12, the numerator is 20 − 15 = 5, and the denominator is 20 − 12 = 8. So Qs/Qt = 5/8 = 0.625, or 62.5%.

A zero value would mean no shunting (all blood participating in gas exchange), while a higher value indicates more blood bypassing ventilated alveoli.

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