DETERMINATION OF THE ONSET OF REBREATHING IN AN ENCLOSED AFFERENT RESERVOIR BREATHING SYSTEM IN ANESTHETIZED, SPONTANEOUSLY BREATHING ADULTS - A COMPARISON OF 3 METHODS

We used three methods to determine the onset of rebreathing in the Ohm eda enclosed afferent reservoir breathing system and compared the resu lts with the previously published rebreathing characteristics of this system. Of the methods studied, expiratory limb capnography proved uns uitable for determining the onset of rebreathing in this system. Inspi ratory limb capnography and minimum inspired carbon dioxide at the mou th did enable the onset of rebreathing to be determined. However the f resh gas flow:minute volume ratio at which rebreathing occurred as det ermined by these criteria was less than that determined by the Kain an d Nunn criteria and thus offer no clinical advantage over the latter.