Dependency of overall fractionation effect of respiration on hemoglobin concentration within blood at rest

In this study it was investigated in which way varying hemoglobin concentrations within blood influence overall fractionation effect of respiration, meaning a change in composition of isotopic oxygen molecules 16O2 and 16O18O within oxygen transported during entire respiration. Since overall fractionation effect of respiration is known to consist of different fractionating and non-fractionating processes, measuring it under condition of anemia could be useful in relating changes in isotopic compositions of oxygen to limitations of entire oxygen transport caused by one or more of these processes. Experiments were performed on 6 patients suffering from various degrees of anemia of a variety of etiologies and on 6 healthy humans. All test subjects breathed air at rest. Samples from inspiratory and expiratory gas were taken in order to analyse 16O18O/16O2 ratios with the aid of respiratory mass spectrometry. Values of overall fractionation effect decreased with respect to a drop in hemoglobin concentration from 17.6 to 6.6 g/100 ml in terms of a linear relationship (r = 0.79) provided that values of overall fractionation effect were normalized so as to exclude the influence of varying ventilatory conditions. It could be shown that at a value of hemoglobin content of 6.6 g/100 ml, 16O2 was transported in preference to 16O18O with a 0.57% higher rate compared to a value of 0.78% obtained at a hemoglobin concentration of 17.6 g/100 ml.(ABSTRACT TRUNCATED AT 250 WORDS)