A comparison of the accuracy of the Siemens injection vaporizer and the Enfluratec 3 vaporizer.

: The accuracy of two Siemens injection vaporizers was examined under operating theatre conditions. For comparison, two Enfluratec 3 vaporizers were tested. The concentrations of enflurane produced by the vaporizers were measured both by an anaesthetic agent monitor and by chromatography. Five experimental modes were used with enflurane delivered either in air/oxygen or in nitrous oxide/oxygen mixtures and the experiments were repeated five times. In every case, the mean concentration values produced by the anaesthetic agent monitor were higher than those obtained by chromatography. The difference may have been due to leakage of the gas sample from the "gas-tight" syringes and/or improper calibration of either analyzer. The Siemens devices were less reliable than the Enfluratecs when enflurane was given in nitrous oxide/oxygen. The former vaporizers seem to be less robust than the Enfluratecs and should be used according to the manufacturer's recommendations. The pressures in the central system were higher than those called for. In addition, improper coupling of the Siemens apparatus to the ventilator may well have influenced the results.