Haemoglobin and Oxygen Transport Flashcards
Composition of air?
78% Nitrogen
21% Oxygen
As altitude increases kPa **
Decreases
Partial pressure of a dissolved gas is equal to what?
The air it equilibrates with
*Overlooks fact that gases have different solubilities in different liquids. Example CO2 is 25 times more soluble in water than Oxygen.
How is alveolar air different to atmospheric air?
Has a lower PAO2 of 14kPa and a higher PACO2 of 5kPa
Tidal volume is small relative to?
Residual lung capacity
What is functional residual capacity?
Air remaining in lungs after exhaling.
*2L when breathing normally
Number of polypeptide chains in Haemoglobin (HbA) and their make up?
4 polypeptide chains. 2 are Alpha chains and 2 are Beta chains.
How many binding sites in Hb?
4 and also there are 4 Iron atoms
Structural difference between HbA and HbF?
HbF has Alpha, Delta and Gamma chains because it needs to compete with the mother for oxygen
What is O2 content?
How much O2 is present in a certain volume of blood including plasma.
*Normally 190-200ml/L
What is O2 Saturation?
Percentage of Hb binding sites which are occupied by O2.
Anaemic people have a lower RBC count and so less Hb. This means that…
O2 content will be low even though saturation and PaO2 are normal.
What is Hypoxia?
PaO2 of 9/10kPa which means Oxygen is not reaching tissues.
What is Cyanosis and why does it occur?
Cyanosis = Blue discolouration of skin.
Due to excessive concentration of deoxy Hb. If 5g/100ml present in blood then colour becomes noticeable.
Central Cyanosis vs Peripheral Cyanosis
Central = Bluish under tongue and lips. Failure of oxygenation due to circulatory or ventilation problems. Peripheral = Bluish at fingertips only. Due to slow flow through peripheral tissue from vasoconstriction.
Why are anaemic patients less likely to get Central Cyanosis?
They have an overall lower concentration of Hb which means saturation is high and occurs faster so there is a lower concentration of deoxy Hb.
What is Polycythaemia?
Patient has abnormally high concentration of Hb due to a high RBC count and therefore has high O2 content.
Why are Polycythaemic patients more likely to present with Central Cyanosis?
High RBC count means a lower saturation.
What causes the O2 Dissociation curve to shift to the left?
*What does a left shift mean?
Lower CO2 Lower 2,3-DPG Higher pH Lower Temperature *Left shift = Saturation at lower PaO2 because it has a higher affinity for Oxygen.
What causes the O2 Dissociation curve to shift to the right?
*What does a right shift mean?
Higher CO2
Higher 2,3-DPH
Lower pH
Higher Temperature
*Right shift = Saturation at higher PaO2 because it has a lower affinity for Oxygen. Therefore easily released to tissue.
What is myoglobin?
Found in hardworking muscles. Used as a back up system to haemoglobin. Made up of a single polypeptide chain and a single ahem group.
