16 carriage of O2 Flashcards
In what 2 ways is oxygen carried in the blood?
dissolved in plasma
bound to haemoglobin in RBC’s
How is there a relationship between PO2 and Hb saturation?
only the dissolved O2 exhibits partial pressure, this then dictates the degree to which O2 binds to haem.
What is Henry’s Law?
dissolved O2 = partial pressure x solubility coefficient (0.225 for O2)
What does haemoglobin offer?
Additional carrying capacity
Why can’t there be 100% oxygen in our lungs?
because there is also H2O and CO2
What is the structure of haemoglobin?
In each haem there is iron, which the O2 binds to. The haem structure then binds to one of 4 polypeptides (globin)
What is O2 content measuring?
quantity of dissolved and haem associated O2 in a given volume
What is O2 capacity measuring?
maximum amount of O2 that can combine with haem in blood (independent of partial pressure)
What is Hb saturation measuring?
ratio of quantity of O2 combined with Hb in a given sample to the O2 carrying capacity of that sample
What does the steep part of the haem dissociation curve represent?
dissociation, ensuring adequate delivery of O2 to tissues, maintaining high PO2 levels, so it diffuses in
What does the flat part of the curve represent?
association
ensures almost complete loading of Hb despite fluctations in PO2
How can the curve be shifted right, and why would we want to shift the curve right in these conditions?
increased CO2 decreases pH increasing temp 2,3-DPG conc autoregulated delivery, the amount of O2 delivered depends on how far the curve shifts right
What effect does the Bohr effect have on the lungs?
none, as this is in the flatassociation bit
What effect on the curve does ventilation have?
none, it only affects PaO2
What effect does CO have on Hb?
it has 210x the affinity as O2 does, so very little is required to minimise O2 carring capacity
