Blood gases

Question 1

Atmospheric gas composition

Answer 1

Nitrogen (78.6%)
Oxygen (20.9%)
Carbon Dioxide (0.04%)
Water Vapour (0.5%)

Question 2

Partial pressures of:

1. Nitrogen
2. Oxygen
3. CO2

Answer 2

1. 597 mmHg
2. 159 mmHg
3. 0

Question 3

Dalton’s Law

Answer 3

The pressure exerted by each gas in a mixture is independent of the pressure exerted by the others

Question 4

Sum of all the partial pressure in atm air at sea level

Answer 4

760 mmHg

Question 5

5 important parameters for gas diffusion

Answer 5

1. Driving force (partial pressure differences across the membrane)
2. Distances to cross need to be small
3. Diffusion coefficient (CO2 diffuses faster than O2)
4. Total surface contact needs to be large
5. Blood flow and airflow need to be coordinated

Question 6

How many molecules of oxygen can on Hb carry?

Answer 6

4

Question 7

4 factors Hb saturation is affected by

Answer 7

1. Partial pressure of O2
2. Blood pH
3. Temperature
4. RBC metabolism

Question 8

The amount of O2 delivered to tissues is determined by… (2)

Answer 8

Blood flow (cardiac output) x O2 content of blood

Question 9

What is the lower limit for saturation?

Answer 9

60 mmHg

Question 10

Causes of shift to the right (4)

Answer 10

Harder to load the Hb, but easier to unload

1. Increase in partial pressure of CO2
2. Decrease in pH
3. Increase in temperature
4. Increase in 2,3-DPG

Question 11

Causes of shift to the left (4)

Answer 11

Easier to load Hb, harder to unload
1. Decrease in partial pressure of CO2
2. Increase in pH
3. Decrease in temperature
4. Decrease in 2,3-DPG
Ex: hyperventilation

Question 12

How is CO2 transported (3 ways)

Answer 12

1. Dissolved in arterial blood
2. Bound to hemoglobin (forms carbamino-Hb)
3. Transported as bicarbonate