Oxygen Delivery and Consumption article

Question 1

Define arterial oxygen content (CaO2).

Answer 1

the amount of oxygen bound to hemoglobin plus the amount of oxygen dissolved in arterial blood

Question 2

What is the equation for arterial oxygen content (CaO2)?

Answer 2

CaO2 (mL O2/dL) = (1.34 x hgb concentration x SaO2) + (0.0031 x PaO2)

(normal CaO2 is approx. 20mL O2/dL)

Question 3

Define mixed venous blood oxygen content (CvO2)?

Answer 3

the amount of oxygen bound to hemoglobin plus the amount of oxygen dissolved in mixed venous blood

Question 4

What is the equation for mixed venous oxygen content (CvO2)?

Answer 4

CvO2 (mL O2/dL) = (1.34 x hemoglobin concentration x SvO2) + (0.0031 x PvO2)

(normal CvO2 is approx. 15mL O2/dL)

Question 5

Define oxygen delivery (DO2).

Answer 5

the rate at which oxygen is transported from the lungs to the microcirculation

[DO2 (mL/min) = Q x CaO2]

(normal is approx. 1L/min)

Question 6

Define oxygen consumption (VO2)

Answer 6

the rate at which oxygen is removed from the blood for use by the tissues

(it can be measured directly or calculated. Both approaches assume that all unused oxygen passes from the arterial to the venous circulation)

Question 7

The oxygen extraction ratio is the relationship between what 2 things?

Answer 7

oxygen delivery (DO2) and oxygen consumption (VO2)

(it is most commonly expressed as the oxygen extraction ratio, which is the proportion of arterial oxygen that is removed from the blood as it passes through the microcirculation:

O2 Extraction Ratio = (CaO2 - CvO2)/CaO2

Normal O2 extraction ratios range from 0.25 to 0.30)

Question 8

Is oxygen consumption (VO2) directly or inversely proportional to oxygen delivery (DO2) and oxygen extraction?

Answer 8

directly proportional

Question 9

Are oxygen delivery (DO2) and oxygen extraction directly or inversely proportional?

Answer 9

inversely proportional

Question 10

Decreased oxygen delivery is a common sequelae of medical illness. What are some ways that oxygen delivery can decrease?

Answer 10

• decreased cardiac output (d/t cardiac disease or hypovolemia)
• anemia
• poor oxygenation (d/t lung disease, right-to-left shunting, diminished inspired oxygen, or hypoventilation)

Question 11

Increased metabolic demand is a common sequelae of medical illness. What are some illnesses that may increase metabolic demand?

Answer 11

• ARDS
• sepsis
• septic shock