Session 3: Oxygen In The Blood Flashcards
What is the solubility factor for O2?
0.01mmol/L/kPa
Which is more soluble: O2 or CO2?
CO2
How can you work out the concentration of dissolved oxygen?
Solubility factor X pO2
What are the axes of a oxygen disassociation curve?
X - partial pressure (kPa)
Y - % saturation
Why is percentage of oxygen bound at saturation used instead of amount of O2 bound for disassociation curves?
The value is independent of pigment concentration
How do you work out how much o2 will be bound or given up when moving from one partial pressure to another?
Work out the difference between the two pO2 values
What state is haemoglobin in when pPO2 is low?
Tense state - so low affinity for o2
Below what pO2 is haemoglobin virtually unsaturated?
1kPa
Above what pO2 is haemoglobin saturated?
9-10kPa
What is the normal oxygen content of arterial blood?
8.8mmol/l
What is typical tissue pO2?
5kPa
What proportion of oxygen is still bound in venous blood?
Over half
What factor increases chance of O2 disassociation from Hb in the tissues?
Lower pO2
What level should tissue pO2 remain above in most tissues?
3kPa
Why is it that tissues with higher capillary density can have a lower pO2?
The oxygen doesn’t have as far to diffuse
In which direction will the disassociation curve shift in acidic conditions?
Right
Which state of Hb does an alkaline condition promote?
R state
What direction will the disassociation curve shift with an increase in temperature?
Right
What state of Hb will an acidic state promote?
T state
Is oxygen more or less readily given up when the disassociation curve shifts to the right?
More readily given up
How much oxygen from arterial blood is given up over the whole body?
About 27%
What is present to increase the amount of oxygen given up to tissues in exercise?
Oxygen reserve
How much 2,3-BPG do red blood cells normally contain?
~5mM
What two conditions increase 2,3-BPG levels?
Anaemia
High altitude
What will an increase in 2,3-BPG do to the disassociation curve?
Shift it to the right
What is cyanosis?
Bluish colouration due to presence of deoxygenated haemoglobin
Where does peripheral cyanosis occur?
Hands and feet
What is the cause of peripheral cyanosis?
Poor local circulation
What is the cause of central cyanosis?
Poorly saturated blood in systemic circulation
Where does central cyanosis occur?
Mouth
Tounge
Lips
Mucous membranes
What does pulse oximetry measure?
Level of Hb saturation in pulsatile arterial blood
What is the main drawback of pulse oximetry?
Does not say how much haemoglobin is present
Which artery is used for arterial blood gas?
Radial artery
What is alveolar pO2?
13.3kPa
