Primary Teaching - Respiratory Physiology Flashcards
Hb oxygen dissociation curve in healthy individual - PaO2 when sats 50%
3.5 kPa
Hb oxygen dissociation curve in healthy individual - PaO2 when sats 75%
5.3 kPa
Hb oxygen dissociation curve in healthy individual - PaO2 when sats 100%
13.3 kPa
Myoglobin dissociation curve
Hyperbolic curve
Why is myoglobin dissociation curve steeper than Hb dissociation curve
Myoglobin only binds one oxygen molecule
Analogy for environment where Hb has lower affinity for O2
Exercising muscle - eg. heat, higher PaCO2, acidosis, (higher 2,3 DPG + pregnancy don’t fit)
Why is there a delay in increasing oxygen carriage post blood transfusion
Stored blood transfusions depletes levels of 2,3 DPG in circulation and therefore causes delay in increase of oxygen carriage post transfusion
Haldane effect
Deoxygenated Hb has higher affinity for CO2
Bohr effect
Rightward shift of Hb oxygen dissociation curve as PaCO2 / acidosis increases
Oxygen requirements of vital organs per minute
200-250 ml/min
Modes of transport of O2
Bound to Hb (majority at sea level in healthy)
Dissolved in plasma
Oxygen content of blood
CaO2 = (SaO2 x 1.34 x [Hb]) + (PaO2 x 0.023)
(SaO2 x 1.34 x Hb) is oxygen bound to Hb
(PaO2 x 0.023) is oxygen dissolved in plasma
0.023 is oxygen solubility coefficient
1.34 is Hüfner constant, amount of oxygen in millilitres carried by each gram of haemoglobin
Oxygen cascade graph
Saturated water vapour pressure
6.3 kPa
PaO2 in atmospheric air at sea level
21.2 kPa
PaO2 in trachea air where humidification occurs
(Atmospheric pressure - saturated water vapour pressure) x PaO2 in atmosphere
(101 - 6.3) x 0.21 = 19.9