Fresh gas flow requirements using the ADE anaesthetic system during late pregnancy

Thirty-two pregnant patients at term undergoing elective Caesarean section were ventilated with a non-co-axial ADE anaesthetic system (E mode) supplied with fresh gas flows (FGF) of either 70 or 100 ml kg-1 min-1, on a random basis. Ventilation with an FGF of 70 ml kg-1 min-1 produced mean PaCO2 and PE' CO2 values of 6.48 +/- 1.15 kPa and 6.41 +/- 0.76 kPa, respectively. Patients were thus hypercapnic, which contrasts with the normocapnia achieved using an FGF of 100 ml kg-1 min-1 via the ADE system (E mode) (PaCO2 5.07 +/- 0.7 kPa; PE' CO2 4.83 +/- 0.46 kPa) (mean values +/- SD). The latter FGF is therefore recommended for the pregnant patient at term when using a Mapleson E system such as the Humphrey ADE apparatus.