Respiratory 3 Flashcards
(22 cards)
What percent of oxygen is transported in the plasma?
2%
How many ml of oxygen is transported by 1g of Hb?
1.34ml
How many ml of oxygen is stored in 15g?
100ml (100% saturated) - remember this when working off of a curve
What is the equation for % SaO2
Oxyghaemoglobin / O2 carrying capacity of oxygen
What is the partial pressure of oxygen when we breathe air?
21kPa
What is the partial pressure of oxygen at the alveolus and why?
14 kPa -because it is diluted by the CO2 coming in and also the water vapour needed to humidify it - remember we can’t breathe DRY GASES
How does gas exchange occur at the blood gas barrier of the alveolus?
Diffusion (Fick’s Law)
What does diffusion depend on?
The SURFACE AREA, the THICKNESS of the membrane and the DIFFUSION CONSTANT.
Why does the oxygen dissociation curve move to the right?
To allow offloading to working tissues
What does a left shift of the oxygen dissociation curve mean? Give an example where this is found:
=Increased Hb-O2 affinity and reduced O2 offloading to tissues
-Foetal Hb
What factors cause a right shift of the oxygen dissociation curve?
-acidosis (increased pH)
- Increased pCO2
-Fever (increased core temp)
-Hypoxic glycolysis
↑2,3 Bisphosphoglycerate
What does Hb consist of?
- 2α and 2β subunits (in adult; fetal differs)
- Contains 4 iron-binding HEME domains
-Oxygen reversibly binds to Fe3+ ions in the centreof the heme ring
-CO2, pH and 2,3 BPG alter this affinity by interacting
with charged amino groups between the α and β subunits
What is the Bohr effect?
A rise in the partial pressure of CO2 or a lower pH will cause offloading of oxygen from haemoglobin.
How does CO2 work to release oxygen from Hb?
- Forms H+ ions
- Forms a carbamate at the N terminal of the HB molecule
How is CO2 transported in the blood (3)
Plasma (physical)
1- Soluble CO2 gas (5%)
2- Bicarbonate ion (90%)
3- Carbaminohaemoglobin (5%) (Chemical)
What is the Haldane effect?
The decreased binding to carbon dioxide in the blood due to increased oxygen levels is
-It is important in the transport of carbon dioxide from the tissues to the lungs.
What do the Bohr and Haldane effects enable?
Reciprocal CO2 and O2 gas exchange
What is the effect of poor ventilation and large blood flow?
-Need to reduce perfusion - hypoxia constricts pulmonary arterioles
What is the effect of good ventilation and poor blood flow?
-Need to reduce ventilation - low CO2 constricts bronchioles
What does hypoxia do?
-Constricts pulmonary arteries to increase pulmonary transit time of blood
What is ventilation perfusion?
The body’s way of matching up gas that enters the alveolus with blood that is in the pulmonary capillaries
What is hypoxic pulmonary vasoconstriction?
When the arterioles supplying a part the lungs contracts as there is no oxygen in the alveolus so there is no point in having any blood flow
