Physiology - Gas Transport of O2 Flashcards
What is the effect of partial pressure on gas solubility using Henry’s Law?
The amount of gas dissolved in a volume of liquid (e.g. blood) is proportional to the partial pressure of the gas. Therefore if the partial pressure of the gas increased more gas would dissolve into the liquid. Slide 6
What are the 2 forms of O2 present in the blood?
Physically 3ml per litre dissolved, 1.5% approx. of the total O2 transported around the body.
Bound to haemoglobin which is the way 98.5% of O2 is transported Slide 7+8
What is the primary factor that determines the percentage saturation of haemoglobin?
PO2. Slide 9
What is the normal PO2 at pulmonary capillaries and systemic capillaries?
Pulmonary = 13.3 kPa/100mmHg Systemic = 5.3 kPa/40mmHg. Slide 11
What is the oxygen delivery index?
The function of oxygen content of arterial blood and the cardiac output and can be calculated by:
DO2I = CaO2 x CI
(multiplying O2 content of arterial blood by cardiac index). Slide 14
What is the oxygen content of arterial blood and what is it determined by?
1 gram of fully saturated Hb carries 1.34ml of O2.
CaO2 = 1.34 x [Hb] x SaO2
It is determined by the haemoglobin conc. and the saturation of it. Slide 15
How can O2 delivery to the tissues be reduced and how?
Respiratory disease - decreased partial pressure of inspired O2 Heart failure - decreased cardiac output
Anaemia - decreased
Hb conc. Slide 16+19
What happens when one O2 molecule binds to Hb?
There is increased affinity of Hb for O2 and works cooperatively and sigmoidal graph flattens when the sites occupied . Slide 20
What does the flat upper portion and the steep lower part of the sigmoid graph for Hb saturation mean?
Flat upper - if there is a drop in alveolar PO2 then the O2 saturation will not be affected too much.
Steep lower - only a small drop in PO2 in capillaries results in the tissues will receive a lot of O2. Slide 22
What is the Bohr Effect and what is the impact of it?
When there are certain conditions the sigmoid curve will shift left or right.
It will shift right where there is high CO2, temp. and BPG and low pH. This means there is increased release of O2 at these conditions which is most likely at the tissues. Slide 23
Why is the Bohr effect important?
It allows more O2 to be released at the tissues which has a pO2 of 5.3 kPa, than it would if the graph hadn’t shifted. Slide 24
How does the structure of foetal haemoglobin(HbF) differ from adult haemoglobin?
HbF has 2 alpha subunits and 2 gamma subunits instead of the 2 alpha and 2 beta subunits. Slide 25
What is different about HbF properties compared to adult?
HbF has a higher affinity for O2 than HbA. The O2-Hb dissociation curve is shifted to the left for HbF compared to HbA. This means that O2 can pass from the mother to the foetus despite a low PO2. Slide 25
Where is myoglobin present and where should it not be found?
It is in skeletal and cardiac muscles. If present in the blood it indicates muscle damage. Slide 26
How many haem groups does myoglobin have?
1 haem group and has no cooperative binding. Slide 26
