Figure 4.
A, Temporal profile of the changes (mean ± SD) in mixed expired fraction of H2S (expressed in ppm during lethal sulfide administration (protocol 1) in the non-MB-treated group (closed symbols) and in the MB-treated sheep (open symbols). Note that the level of sulfide in the expired gas was lower in the MB treated group. On note, (B) is illustrating the actual flow of H2S reaching the central circulation, ie, cardiac output times the concentration of gaseous H2S extrapolated from the estimation of alveolar fraction of H2S. Indeed, as H2S was infused at a constant rate, the concentration of H2S in the blood reaching the central circulation was dictated by the level of venous return/cardiac output (see text for further comments). C, Shows the in vitro effects of mixing MB and H2S in the absence of O2, clearly MB is reduced by the presence of H2S, which is being oxidized in the process.