Carbon dioxide in the chick embryo towards end of development: effects of He and SF6 in breathing mixture.
Using an implanted CO2 electrode in the air cell of the chicken egg, its PCO2 could be followed continuously during the prenatal and paranatal period until hatching occurred. CO2 elimination rate was followed simultaneously. At various stages such eggs were subjects to 75 : 25% He/O2 and SF6/O2 atmosphere, resulting in a large decrease and increase, respectively, in air cell CO2 tension, indicating that during the prenatal stage all CO2 exchange was by gas phase diffusion transport across the pores of the shell. Measurements of the change in PCO2 as well as the CO2 output allowed one to calculate the effective diffusion coefficient for CO2 in the He and SF6 mixtures, which agreed well with the theoretical values calculated according to Wilke (1950). From the CO2 release or retention following exposure, respectively, to He or SF6 the CO2 capacitance values for blood and tissue could be calculated and agreed with values established in mammals. During the last period of development, the paranatal period, the change of PCO2 after replacement of N2 by He gradually declined, indicating that pulmonary ventilation was replacing diffusion through egg shell pores.
D000818:Animals; D002245:Carbon Dioxide; D002642:Chick Embryo / Q000502:physiology*; D004058:Diffusion; D006371:Helium; D010313:Partial Pressure; D013459:Sulfur Hexafluoride
D002245:Carbon Dioxide; D006371:Helium; D013459:Sulfur Hexafluoride