Saturday 12 November 2016

What is oxygen flux? b) Draw oxygen haemoglobin dissociation curve ,enumerate the factors producing leftward and rightward shift

Oxygen Flux: The amount of oxygen leaving the left ventricle per minute in the arterial blood has been termed as the "Oxygen Flux"
 O2 Flux = Q  ([Hb] * SatHb * 1.34 ml/g) + (Pa O2 * 0.03ml/L)
Q = cardiac output
                               
                                                                                                                             
At pH 7.4 the Po2 which is then oxygen tension at which the haemoglobin is 50% saturated is  26.6mm of Hg , which is reduced when the curve shifts to left and Po2 is increased when the curve  shifts to right

1) pH(Bohr Effect)-A fall in pH which may either be respiratory or metabolic causes the curve to shift to the right and lowers the O2 affinity which displaces O2 from haemoglobin and makes more O2 available to tissues.
A rise in pH causes a leftward shift in the oxygen-haemoglobin dissociation curve which increases the haemoglobin  affinity for oxygen while reducing its availability to tissues.
2) 2,3 Diphosphoglycerate(2,3 DPG) is a by -product of glycolysis (the Rapoport-luerbering shunt) and accumulates during anaerobic metabolism.
A rise in 2,3 DPG is associated with a rightward shift in the oxyhaemoglobin dissociation curve and a reduction in haemoglobin affinity of oxygen which delivers more oxygen to tissues
A low concentration of 2,3 DPG is associated with a leftward shift of the curve.
3) Temperature-A fall in temperature shifts the curve to the left while a rise in temperature shifts the curve to right and reduced affinity of haemoglobin to oxygen thus facilitates more oxygen delivery to tissues.