Pulmonary blood Flow, gas exchange, transport- Transport Flashcards
what does blood transport and why?
oxygen from the lungs to the tissues to produce energy to power our cells. - it produces co2 as waste product which is again carried by blood back to the lungs to get rid of in expiration
how much oxygen can we dissolve per litre of plasma?
3ml / litre of plasma
- oxygen is not very soluble in water
- not enough to meet energy demnd
- consider red blood cells, (not just plasma), which contain Haemoglobin. This increases the oxygen carrying capacity of whole blood to 200ml
- 200ml of oxygen in whole blood (plasma+red blood cells)
what does haemoglobin do?
How is most of our co2 diluted?
in various forms, in solution
what transport of gas is more compliated
what is arterial partial pressure of O2 (PaO2) not the same as?
arterial oxygen concentration content
what does PaO2 refer to? what does PaO2 determined by?
O2 in solution in the plasma and is determined by the O2 SOLUBILITY and the PARTIAL PRESSURE OF O2 in the gaseous phase (alveoli) which is driving o2 into solution
arterial partial pressure of oxygen (PaO2) is ___ the same as _______
not, arterial oxygen concentration/content
what does arterial o2 concentration/content refer to?
- oxygen that is in solution in the plasma
- oxygen that is attached to haemoglobin in the red blood cells
calculate the arterial partial pressure of oxygen
o2 solubility = 0.03ml
3ml o2/L plasma so the partial pressure of oxygen that is driving it into solution form gaseous phase (partial pressure at the alveoli) is 3/0.3=100
=> 100mmHg PaO2
what is the partial pressure in gaseous phase that is driving that gas into solution equal to?
what do gases not travel in in plasma?
with no red blood cells, what is the arterial O2 content?
what is cardiac output?
wht is the o2 demand of resting tissues?
250ml/min
describe the effect haemoglobin has on oxygen transport
-
what is our total oxygen carrying capacity?
200 ml
how saturated is the haemoglobin with oxygen? what is haemoglobin?
98%
- 92% is HbA
- protein, 4 polypeptide chains (2 alpha, 2 beta), each assocaited with an iron containing haem group
- it is the iron heme group which associates with 1 molecule of oxygen
- each haemoglobin molecule carries 4 oxygen molecules
What determines how saturated haemoglobin is with oxygen?
The partial pressure of oxygen in arterial blood
explain the haemoglobin-oxygen graph
- at normal systemic arterial PaO2 100mmHg, haemoglobin is almost 100% satruated with oxygen
- even as systemi arterial PaO2 decreases to 60mmHg, haemoglobin is still 90% satruated with oxygen
alveolar pressure is moderated decreased- still allows a relatively normal uptake of oxygen to haemoglobin
- partial pressure of oxygen can drop by 40%, yet we only lose 8% satrution of o2 with Hb
=> big safety net, we can have a big fall in partial pressure of oxygen with only a minimum impact of total arterial oxygen content.
- affinity for Hb for oxygen starts to fall rapidly below 60mmHg. Small changes in partial pressure of oxygen start to have bigger changes on the saturation of haemoglboin ith oxygen therefore big efffects on total arterial content.
what is the reserve capacity at normal venous PO2?
- partial pressure of resting cell- 40mmHg, haemoglobin is still 75% with oxygen
- 75% reserve capacity
- oxygen delivery to all of our tissues is 1000ml o2/ per min
- we only use/extract 250ml of o2/ 25% that is wrapped up in hb
what are the two other types of haemoglobin?
- myoglobin= higher affinity for o2 than haemoglobin
- HbF(foetal)- find in foetus= higher affinity for o2 than haemoglobin
- they get their o2 from the blood, need to have a higher affinity than adult hB TO BE ABLE TO EXTRCT IT FROM THEM and get it into the muscle cell/foetus
what does myoglobin and foetal hamogolbin have in relation to normal haemoglobin?
for any given partial pressure, foetal haemoglobin and myoglobin will have a higher affnity for oxygen than adult haemoglobin.
what is anaemia?
term where oxygen carrying capacity is compromised
how can anemia occur?
- reduced iron deficiency( iron haem groups in haemoglobin which is binding to oxygen)
- haemorrhage- losing red blood cells
- vitamin b12 defiency - needed to make red blood cells
whats happens to PaO2 in anaemia?
- stays the same. PaO2 partial pressure of oxygen in arterial blood reflects the amount of oxygen in solution in plasma.
determined by gas solubility nd the partial pressure of oxygen in the gaseous phase(alveoli) driving the gas into solution
- nothing about red blood cells
lost lots of red blood cells- no effect on how much oxygen is moving from alveoli into the plasma
- anaemia , PaO2 normal despite smaller total oxygen content is reduced oxygen carrying capacity in the blood
- anaemia still carries the oxygen fine, just smaller arterial o2 content
what happens to PaO2 in anaemia?
PaO2 is normal despite smaller total blood o2 content.
we can have normal PaO2/ partial pressure of arterial oxygen while total blood oxygen content is low
but we cant have low PaO2/partial pressure of arterial oxygen and normal blood oxygen content. it is the partial pressure of oxygen that is determining how much Hb bind to oxygen in red blood cells
a) around 100%
=> the PaO2/partial pressure of oxygen in plasma is normal
=> MAIN determinant of haemoglobin saturation is PaO2/partial pressure of oxygen in plasma
=> so haemoglobin saturation is normal
- only issue is NOT A LOT of Hb but it is fully saturated because the PaO2 is normal
