Which equation describes systemic oxygen delivery (DO2)?

Which equation describes systemic oxygen delivery (DO2)?

• A. DO2 = CO × CaO2
• B. DO2 = CO × CvO2
• C. DO2 = VO2 × CaO2
• D. DO2 = HR × CaO2

Answer: (A)

Systemic oxygen delivery builds from two things: how much blood is being moved each minute, and how much oxygen that blood carries. That means DO2 equals cardiac output times arterial oxygen content. In other words, you deliver a minute’s worth of blood, and each unit of that blood has a certain amount of O2 bound to hemoglobin (plus dissolved O2); multiply the flow by the content, and you get the total O2 delivered to the tissues per minute.

Cardiac output is the product of heart rate and stroke volume, not just heart rate alone, so using HR × CaO2 would ignore how much blood is pumped per beat. CaO2 depends on hemoglobin and oxygen saturation (plus dissolved oxygen), not on venous content. The quantity VO2 represents oxygen consumed by tissues and is given by CO × (CaO2 − CvO2), linking delivery to extraction, not delivery by itself.

So the expression DO2 = CO × CaO2 correctly captures how much O2 is delivered systemically each minute.