33. THE P50 OF THE OXYGENHAEMAGLOBIN DISSOCIATION

[Editor]

33. THE P50 OF THE OXYGENHAEMAGLOBIN DISSOCIATION CURVE


a) is 3.5kPa
b) is influenced by 2 3 DPG levels
c) shifted to the right with fetal haemoglobin
d ) is shifted to the left in acidotic conditions
e) is affected by erythropoietin

[Editor]

TTFFF

The p50 is the po2 of blood when 50% of the haemoglobin is saturated with oxygen. It gives a good reference point as to right and left movements of the oxygen haemoglobin dissociation curve under different physiological conditions.
The p50 is shifted to the right (p50>3.5KPa) with acidosis, hyperthermia, hypercapnia (bohr effect), increased 2,3 DPG.
It is shifted to the left with fetal haemoglobin, methaemoglobinaemia, carbon monoxide poisoning.
Erythropoietin controls the haemoglobin concentration so directly affects the oxygen carrying capacity of blood. It does not alter the p50.