Oxygen and carbon dioxide dissociation of duck blood

Oxygen and CO2 dissociation of duck blood was studied in blood samples equilibrated with known gas mixtures at the bird's body temperature (41 degrees C) and analyzed in the Van Slyke manometric apparatus and in pH electrodes. At various pH values between 7.38 and 7.55 the Hill plots yielded straight and parallel lines over a wide range of O2 saturation, the Hill coefficient being 2.9. Half saturation pressure P50 at pH = 7.50 was 36 torr. The Bohr effect factor was -0.53. Buffering properties were analyzed by equilibrating blood samples with gas mixtures of different PCO2 at 41 degrees C. The buffer value for whole blood in the range of 3-7% CO2 was 19.3 mMol-L-1-pH-1, the buffer value for true plasma 22.9 mMol-L-1-pH-1. The CO2 dissociation curve constructed using the buffer values had a slope of 0.17 mMol-L-1-torr-1 in the PCO2 range from 40 to 50 torr. The CO2 content of oxygenated blood at PCO2 = 40 torr was 21.7 mMol-L-1. The Haldane effect factor at PCO2 = 35 torr equalled 0.30 mMol of combined CO2 per mMol HbO2. With the values of PO2, PCO2 and pH measured in arterial blood of undisturbed and unrestrained, resting ducks effective dissociation curves for both O2 and CO2 were constructed assuming a metabolic R.Q. of 0.8. These curves are expected to resemble closely the actual in vitro dissociation curves of resting ducks.