A comparison of vital capacity breath and tidal breathing techniques for induction of anaesthesia with high sevoflurane concentrations in nitrous oxide and oxygen.

Vital capacity breath and tidal breathing techniques were compared for induction of anaesthesia with 7.5% sevoflurane in nitrous oxide, and oxygen. Thirty five subjects were randomly assigned to a vital capacity breath group (19) or to a tidal breathing group (16). The mean time for induction was faster with vital capacity breath (41 s) than with tidal breathing (52 s, p < 0.05). Some involuntary movements were seen in the tidal breathing group but none in the vital capacity breath group. Coughing was seen in a quarter of the subjects in the tidal breathing group and in one subject of the vital capacity breath group. The vital capacity group showed excellent characteristics: rapid, and pleasant induction without premedication. We conclude that the vital capacity breath technique is necessary for the inhalation induction of anaesthesia; it provides enough overpressure to allow the subject to pass reliably and rapidly through the initial stages of excitement.