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Fifty patients scheduled for surgery under lumbar epidural anaesthesia were included in a study toevaluate the possibility of localising the epidural space solely by means of an acoustic signal. With an experimental set-up, the pressure generated during the epidural puncture procedure was translated into a corresponding acoustic signal. One anaesthetist held the epidural needle with both hands and detected the epidural space by means of this acoustic signal. At the same time, a second anaesthetist applied the loss of resistance technique and functioned as control. In all patients the epidural space was located with the acoustic signal. This was confirmed by conventional loss of resistance in 49 (98%) of the patients; in one patient (2%) it was not. We conclude that it is possible to locate the epidural space using an acoustic signal alone.