oxygen in blood and tisssues Flashcards
what does an oxygen carrier need to be?
why is the oxygen dissociation curve sigmoidal?
what’s the complex name for this?
around what pO2 does the oxygen saturation become full?
reversible, associate with O at lungs and dissociate at tissues
because its harder for the first oxygen to bind, after this is progressively gets easier - no linear relationship
positive cooperativity
anything above 10kPa ppO2
what is the T state ?
R state?
what is useful about these?
it is when there is a low affinity for O2 in the Hb and difficult for O2 to bind (hard for O2 to bind)
when there is a high affinity for O2 to bind and is relaxed (easy for O2 to bind)
T state means that when O2 has been dissociated at the tissues - it will not easily bind back to Hb due to tense state therefore tissues can use the O2
R state manes that in the lungs the O2 can bind
what is the danger zone in the oxygen dissociation curve?
its the steep part of the curve (2-6kPa)
there are huge changes in oxygen saturation here with only a small change in pO2
can cause rapid deterioration if in this zone
in anaemia what happens the pp and hb saturation?
what’s the difference between hypoxia and hypoxaemia?
they both stay the same - all Hb saturated but less of it - same amount of dissolved O2 hypoxia = tissues not getting enough O2 hypoxaemia = low pO2 in arterial blood
what pO2 doe metabolically active tissue have?
venous blood?
why is this good
5kPa - this means the Hb will still hold onto some of its O2 (65% full)- at this lower pO2 the Hb is tense so won’t take the O2 given off back
6kPa - there is still lots of O2 bound - this is good as it give a buffer for us to give more O2 in disease e.g. sepsis
how low can the pO2 in capillaries supplying tissues get? and why?
how can you help lower the pO2?
around 3kPa - no lower as there sit a sufficient partial pressure gradient for diffusion below this
more capillary density means that diffusion is faster so people who do sport or live at high altitude have this
what shifts the Bohr curve right (reduces Hb affinity for O2)
increased temp - metabolically active have higher so need more O2 to dissociate
increased H (lower pH) - metabolically active have lower pH so need more O2 to dissociate
increased 2,3-BPG - made in glycolysis during hypoxia meaning more likely for RBC to give off O2 to hypoxic tissue - seen more in people who live in high altitudes
what shifts the Bohr curve left (higher affinity)>?
CO
decreased H
decreased 2,3-BPG
decreased temp
how much oxygen is given up in maximum unloading ?
at metabolically active tissues 70% can be given off
its because the pO2 of he tissues will be lower maintaining pp gradient
what way does carbon monoxide shift the Bohr curve?
why?
what would ABG show?
left (more affinity for O2)
not only dos CO bind to Hb reducing oxygen transport
it also increases the affinity of unaffected subunits for Hb therefore reducing the amount of O2 carried and the amount of O2 released to tissue
normal at first them severe derangement
what % of Hb need to have CO for it to be fatal?
why are children more at risk?
symptoms?
does it effect PaO2?
50%
because children breathe faster
headache, nausea, vomiting, slurred speech, confused
nope
what % of Hb need to have CO for it to be fatal?
why are children more at risk?
symptoms?
does it effect PaO2?
50%
because children breathe faster
headache, nausea, vomiting, slurred speech, confused
nope
what is cyanosis?
2 types?
what are they due to?
why can it be difficult to detect ?
blue colouration due to unsaturated Hb - deoxy Hb is more blue in colour that saturated Hb
peripheral (feet hands) or central (mucous membranes, tongue, lips, mouth)
peripheral = hypoxia
central = hypoxaemic
skin colour, lighting, shoes
what does a pulse oximeter do?
what won’t it detect?
who is it less accurate in?
detects Hb saturation level by different absorption of a laser in arterial blood
CO poisoning or anaemia as Hb is still saturated
darker skin
what does an ABG measure?
compare ABG to oximeter
pO2, pCO2, pH, HCO3-
