2.5 Blood Gases

Question 1

What are the O₂ Partial pressure values in the arterial blood and in mixed venous blood?

Answer 1

O₂ = 95 in arterial blood

O₂ = 40 in mixed venous blood

Question 2

What is the equation for determining the Dissolved O₂ concentration?

Answer 2

Disolved O₂ concentration = (P₀₂) X (O₂ solubility at body temp)

Normally the O₂ Solubility = 0.0031

Question 3

What four factors can shift the O₂ dissociation curve to either the right or left?

Answer 3

1. Temp
2. P_CO2
3. H⁺
4. 2,3 DPG (2,3-diphosphoglycerate)

Increases in any of these shift the curve to the right and decreases shift to the left

Question 4

Does the P_O2 in the plasma have to be greater or less compared to the tissues for O₂ to diffuse into the tissue?

Answer 4

P_O2 has to be less in the tissues compared to the plasma for O₂ to diffuse in. Tissues consume the O₂ leading to a decrease in the P_O2 there.

Question 5

What is the Hb concentrations at normal conditions, anemic conditions, and during polycythemia?

Answer 5

Normal = 15

Anemia = 10

Polycythemia = 20

Question 6

Patient comes in with difficulty breathing. You order an ABG and get the following results: pH 7.5, HCO₃ 31, Pa_CO2 is 50. How would you label this?

Answer 6

Metabolic alkalosis with respiratory compensation

Question 7

What is the biggest contributor for CO₂ in the arterial blood?

Answer 7

HCO₃^- at 90% of the transport in arterial blood. Its also the highest in venous blood at 60%.

Question 8

How is CO₂ transported in Hemoglobin and why is this more important in venous blood?

Answer 8

CO₂ is transported as carbamino in hemoglobin and it makes up 30% of the CO₂ that is transported in venous blood where there is less oxygen so the hemoglobin holds onto the CO₂