The oxygen affinity of normal human whole blood measured by double tonometry. I. P50 and n factor.

The Authors refer that the oxygen affinity, determined by double tonometry, in normal adult whole blood, is mainly expressed by a P50 of 26.13 +/- 4.31% and by an n factor of 2.63 +/- 6.63%. These results are in good agreement with those reported in the literature, but here are some doubts that pO2 and SO2 alone, i.e. the data drawn from all the tonometric procedures, can give a full idea of the affinity. In fact, this one is a complicate process, modulated by a number of allosteric effectors. Most of them, like pH, temperature and pCO2 can be always kept at a fixed standard level, whereas DPG, the main one, cannot.