Interactions between placental O2 and CO transfer.

In 14 pregnant ewes the fetal side of the placenta was artificially perfused with adult sheep blood or with an emulsion of the fluorocarbon FC-47 containing varying amounts of CO. We measured diffusing capacities for O2 and Ar and permeability for urea and tritiated water (3H2O). We found that O2 diffusing capacity fell markedly in the presence of low levels of CO but that AR diffusing capacity and the permeability of urea and 3H2O remained constant at different levels of exposure to CO. We interpret the results as being consistent with the hypothesis that placental O2 transport is partially carrier mediated and that O2 and CO compete for the same carrier.