Blood gases and acid-base status in chicken embryos with naturally varying egg shell conductance

In chicken eggs selected for widely varying values of specific water vapor conductance, gH2O (= water vapor conductance per freshly laid egg mass), PCO2, pH, PO2 and hematocrit were measured in arterialized blood sampled from an allantoic vein (after 16 days of incubation) or in blood termed 'venous', sampled from an allantoic artery (after 18 days of incubation). Both arterialized and 'venous' PCO2 were inversely related to gH2O. Since the variations of blood plasma pH with PCO2 were smaller than predicted for true plasma, partial compensation by appropriate non-respiratory changes of plasma bicarbonate concentration must have occurred. Only with extremely high and low gH2O a definite alkalosis and acidosis, respectively, were observed. Both arterialized and 'venous' PO2 tended to diminish with decreasing gH2O. The hematocrit value showed a tendency to increase with decreasing gH2O and with decreasing arterialized PO2.