Session 3: Oxygen In The Blood

Question 1

What is the solubility factor for O2?

Answer 1

0.01mmol/L/kPa

Question 2

Which is more soluble: O2 or CO2?

Answer 2

CO2

Question 3

How can you work out the concentration of dissolved oxygen?

Answer 3

Solubility factor X pO2

Question 4

What are the axes of a oxygen disassociation curve?

Answer 4

X - partial pressure (kPa)

Y - % saturation

Question 5

Why is percentage of oxygen bound at saturation used instead of amount of O2 bound for disassociation curves?

Answer 5

The value is independent of pigment concentration

Question 6

How do you work out how much o2 will be bound or given up when moving from one partial pressure to another?

Answer 6

Work out the difference between the two pO2 values

Question 7

What state is haemoglobin in when pPO2 is low?

Answer 7

Tense state - so low affinity for o2

Question 8

Below what pO2 is haemoglobin virtually unsaturated?

Answer 8

1kPa

Question 9

Above what pO2 is haemoglobin saturated?

Answer 9

9-10kPa

Question 10

What is the normal oxygen content of arterial blood?

Answer 10

8.8mmol/l

Question 11

What is typical tissue pO2?

Answer 11

5kPa

Question 12

What proportion of oxygen is still bound in venous blood?

Answer 12

Over half

Question 13

What factor increases chance of O2 disassociation from Hb in the tissues?

Answer 13

Lower pO2

Question 14

What level should tissue pO2 remain above in most tissues?

Answer 14

3kPa

Question 15

Why is it that tissues with higher capillary density can have a lower pO2?

Answer 15

The oxygen doesn’t have as far to diffuse

Question 16

In which direction will the disassociation curve shift in acidic conditions?

Answer 16

Right

Question 17

Which state of Hb does an alkaline condition promote?

Answer 17

R state

Question 18

What direction will the disassociation curve shift with an increase in temperature?

Answer 18

Right

Question 19

What state of Hb will an acidic state promote?

Answer 19

T state

Question 20

Is oxygen more or less readily given up when the disassociation curve shifts to the right?

Answer 20

More readily given up

Question 21

How much oxygen from arterial blood is given up over the whole body?

Answer 21

About 27%

Question 22

What is present to increase the amount of oxygen given up to tissues in exercise?

Answer 22

Oxygen reserve

Question 23

How much 2,3-BPG do red blood cells normally contain?

Answer 23

~5mM

Question 24

What two conditions increase 2,3-BPG levels?

Answer 24

Anaemia

High altitude

Question 25

What will an increase in 2,3-BPG do to the disassociation curve?

Answer 25

Shift it to the right

Question 26

What is cyanosis?

Answer 26

Bluish colouration due to presence of deoxygenated haemoglobin

Question 27

Where does peripheral cyanosis occur?

Answer 27

Hands and feet

Question 28

What is the cause of peripheral cyanosis?

Answer 28

Poor local circulation

Question 29

What is the cause of central cyanosis?

Answer 29

Poorly saturated blood in systemic circulation

Question 30

Where does central cyanosis occur?

Answer 30

Mouth
Tounge
Lips
Mucous membranes

Question 31

What does pulse oximetry measure?

Answer 31

Level of Hb saturation in pulsatile arterial blood

Question 32

What is the main drawback of pulse oximetry?

Answer 32

Does not say how much haemoglobin is present

Question 33

Which artery is used for arterial blood gas?

Answer 33

Radial artery

Question 34

What is alveolar pO2?

Answer 34

13.3kPa