Oxygen in the Blood

Question 1

How is the amount of O2 dissolved in plasma calculated?

Answer 1

[O2] dissolved = solubility x pO2

Question 2

What is CO at rest?

Answer 2

5 L/min

Question 3

What are oxygen binding pigments?

Answer 3

Haemoglobin = blood tetramer – binds 4 oxygen molecules

Myoglobin = muscle monomer – binds 1 oxygen molecule

Question 4

What is mixed venous blood?

Answer 4

Mixture of blood returning from various tissues of varying metabolic levels

Question 5

What is the Bohr shit?

Answer 5

Acid conditions = shift to the R in the oxygen dissociation curve = more O2 given up

Lower pH promotes T state of Hb

PH is lower in the most met active tissues

Question 6

What is 2,3-BPG?

Answer 6

Shifts Hb dissociation curve for O2 to the R = more O2 given up

Increased levels in anaemia, high altitude

Question 7

Outline CO poisoning

Answer 7

Reacts with Hb to form HbCO

Increases affinity for O2 = wont give up O2

Fatal if HbCO = >50%

Question 8

Define hypoxemia

Answer 8

Low pO2 in arterial blood

Question 9

Define hypoxia

Answer 9

Low oxygen levels in the body/tissues

If pO2 is low not all Hb will be saturated

If Hb is low not enough O2 will be present in the blood

Question 10

Define cyanosis

Answer 10

Bluish colouration due to unsaturated Hb

Peripheral = poor circulation

Central poorly saturated blood in systemic circulation, or mixing of arterial and venous blood

Question 11

What is pulse oximetry?

Answer 11

Device that detects Hb saturation

Only detects pulsatile arterial blood

Red and infrared light emitted – absorbed by Hb – remaining is absorbed by light detector

Saturated Hb is red = doesn’t absorb as much red light

Question 12

How can Hb saturation be analysed?

Answer 12

Pulse oximetry

ABG