The use of a single venous blood sample to assess oxygen binding in haemoglobin

The measurement of pH, PO2, PCO2 and SO2 in a single venous blood sample can be used to determine the P50 at standard or at in vivo conditions. This technique makes it feasible for a physician, firstly, to make an assessment of the net adaptation of the red cell to reductions in blood oxygen content or flow and, secondly, to make an initial assessment of whether a haemoglobin with altered affinity for oxygen is present in subjects with polycythaemia or anaemia.