DESFLURANE AND ERRONEOUS VAPOR SETTING ON THE ANALYZER

With monochromatic infrared gas spectrometers (MIS), the displayed con centration is computed from measured IR absorption and a gain factor s pecific for the selected volatile agent (VA). As MIS cannot detect whi ch VA is actually present, the displayed concentration can be very dif ferent from the actual one. As bottles and vaporizers are very specifi c for desflurane, it is impossible to misfill a vaporizer; however an erroneous selection of VA on MIS remains possible. The aim of this stu dy was to assess the displayed concentrations after erroneous vapour s election on the monitor. When either desflurane, or isoflurane or enfl urane were delivered at constant concentrations, all VA measured by th e MIS, namely desflurane, sevoflurane, isoflurane, enflurane and halot hane were successively selected and the displayed concentrations compa red with the actual vapour concentration using a Capnomac(TM) Ultima(D atex) monitor. Consequences of erroneous selection can be included in three categories: 1) dangerous error, when a displayed concentration i s much lower than the actual one, eg desflurane or sevoflurane erroneo usly selected, 2) evident error, when displayed concentration is much higher than 10 vol%; 3) incomfortable situation, when displayed and ac tual concentrations are similar, eg isoflurane erroneously selected in stead of desflurane. This error can only be detected by a careful chec king of the device.