[The role of hemoglobin affinity for oxygen in the efficiency of the respiratory function of the blood].

In acute experiments the oxygen transport properties of two solutions of modified stroma-purified hemoglobin were investigated using anesthetized Wistar rats. The solutions were: solution 1 (Hb = 8.0 g per 100 g, P50 = 12.5 mm Hg) and solution 2 (Hb = 4.4 g per 100 g, P50 = 21.5 mm Hg). The solutions were used in stage-by-stage isovolumic substitution in rats of two groups. The modified hemoglobin solution with a lower hemoglobin oxygen affinity was found to be a more efficient blood substitute. In spite of its low oxygen capacity, it could sustain life activity at very low hematocrit values. When the oxygen capacity of blood is moderate or low, hemoglobin oxygen affinity plays a very important part in oxygen supply to different tissues, specifically to the heart. The latter determines the crucial compensatory physiological reaction to acute anemia, i. e. increase of cardiac output.