ABSTRACT
The [2,3-DPG]/[Hb] ratio and the P50 were found to be lower in the 10% denser (old) than in the 10% lighter (young) red blood cell (RBC) fractions (0.57 +/- 0.13 vs 0.96 +/- 0.13 and 23.02 +/- 0.85 vs 27.47 +/- 1.05 Torr, respectively, mean +/- SD, P less than 0.0005 for both, n = 6). The RBC aging processes appear thus to affect the RBC oxygen affinity. However, the [2,3-DPG] changes do not fully explain the drop of not fully explain the drop of P50 as measured at constant [H+], [CO2] and [HbCO]. It is therefore postulated that an additional factor is involved in the regulation of the oxygen affinity in the ageing RBC. The RBC density in 59 normal individuals matched for age (infants, adult, and aged) and for sex was found to be younger in adult females than in all other groups (P less than 0.0005), including an age-matched group of pregnant women. Correspondingly, the [2,3-DPG]/[Hb] ratio and the P50 are higher in adult females than in adult males (0.92 +/- 0.10 vs 0.82 +/- 0.09, P less than 0.009, and 29.03 +/- 1.07 vs 27.72 +/- 0.82 Torr, P less than 0.002, respectively). These data are evaluated in terms of the efficiency of the oxygen transport calculating the circulatory load required to transport a given amount of oxygen to the tissues. The results indicate that the lower oxygen affinity (due to the younger RBC population) in adult females partially compensates for their lower [Hb].
Subject(s)
Erythrocyte Aging/physiology , Erythrocytes/metabolism , Oxygen/metabolism , Adult , Aged , Aged, 80 and over , Child , Child, Preschool , Diphosphoglyceric Acids/blood , Female , Hemoglobins/analysis , Humans , Male , Middle Aged , PregnancyABSTRACT
A simplified model is described to estimate the oxygen delivery to tissues as a function of oxygen uptake, gas exchange ratio, 2,3-DPG/Hb concentration ratio, arterial and venous PO2, PCO2 and pH. Due to the complexity of the oxygen delivery system, the aim of this model is to predict relative changes of the oxygen delivery to tissues induced by changes of the other variables, rather than to yield absolute values. In this work, the importance of the observed shifts of the hemoglobin oxygen equilibrium curve at altitude is evaluated in terms of the efficiency of the oxygen transport system. It will be shown that a rightward shift of the oxygen equilibrium curve is beneficial up to 5400 m.a.s.l., while for higher altitudes such shifts lead to less efficient oxygen delivery to tissues.
