CORRELATION BETWEEN MATERNAL AND FOETAL Po2 AND Pco2 DURING CAESAREAN SECTION

Fifteen cases of elective Caesarean section at term were studiedunder general anaesthesia. Maternal carbon dioxide tensionswere controlled by adjusting the minute ventilation volume;Pa_co2 ranged from 13 to 80 mm Hg. Maternal oxygen tensions werecontrolled by changing the inspired oxygen concentrations (20,33.3, 50, or 100 per cent); Pa_o2 ranged from 78 to 500 mm Hg.Umbilical vein Po₂ and Pco₂ of the newborn varied accordingto the maternal level. Foetal Pco₂ was always higher than maternalPa_oo2; the mean maternal-foetal gradient was 11.3 mm Hg (SD4.7). Foetal Po₂ was positively correlated with maternal Pa_o2within the range 78 to 200–300 mm Hg, but was not correlatedwith further elevation of maternal Pa_o2 from 200 to 500 mm Hg.This might be attributed to the shape of Hb_o2 dissociation curve.