Prediction of the oxygenation of human organs at varying blood oxygen carrying properties.
The oxygenation of some human organs (brain, heart, kidneys, and legs) is correlated to the oxygen carrying characteristics of blood by predicting the PVO2 vs Q relationship at a given metabolic level of the organ. The effect of moderate shifts of the oxygen equilibrium curve [approximately equal to 2 Torr (0.27 kPa), comparable to the shifts caused by non-massive transfusions of blood with altered 2,3-diphosphoglycerate (DPG) concentration] is evaluated in terms of the efficiency of organ oxygenation. The results indicate the following. (1) An increase of the P50 from 27.9 to 30.0 Torr (3.71 to 3.99 kPa), that is the consequence of an increase of the [DPG]/[Hb] ratio from 0.8 to 1.04 M/M, is advantageous for all organs, because the normal metabolic level can be maintained with a considerable reduction of Q (approximately 10%). (2) This reduction is similar to that caused by an increase of [Hb] from 160 to 182 g/L, but without increasing the blood viscosity and the vascular resistance. (3) This advantage is different for the various organs, as a function of their blood supply and metabolic level characteristics. These features were also observed at any PaO2 in the range 60-300 Torr (7.98-39.9 kPa), and when simulating acidemia or alkalemia, as well as a pH gradient across the organ.