Investigation of Plasma Carbonic Acid pK′ of the Chicken

Abstract

AN accurate calculation of carbon dioxide tension in blood plasma by means of the Henderson-Hasselbalch equation requires the use of an exact pK′ for carbonic acid. According to Severinghaus (1956a), total errors up to 15% in computing PCO2 of blood samples are not uncommon. To the present time nearly all of the work on pK′ has been with human, canine or horse blood. We are not aware of any studies on the pK′ of chicken plasma, but the value of 6.10 is used. Cullen et al. (1925) measured the rise in pK′ as temperature fell and found it to be 0.005 units/degree. Therefore, this factor alone may influence the pK′ in the chicken since the body temperature is considerably higher than in mammals. Hastings et al. (1928) established a pK′ of 6.10 at 38°C. and this is the most widely accepted figure for human blood. Values from 6.064 to 6.113…