Analgesic action of extradural fentanyl.

the dial by two screws, but in the faulty vaporizer one had fallen out, into the top of the casing. With the cam loose, it was possible to turn the dial a few degrees clockwise beyond the OFF position, when a strong smell of enflurane was noticed in the fresh gas flow. Anaesthetists should be aware that unless the OFF mark on the concentration setting dial coincides with the datum mark, then their Enfluratec or, presumably, Fluotec 3, may still deliver vapour. I have reported this finding to Cyprane, making two suggestions. First, all existing Enfluratecs should be modified by fixing the cam to the dial by four instead of two screws. The cam and dial are already drilled and tapped for this, the extra holes being used at present to attach the name-plate to the dial. Second, the present design, with a hard steel spring working on a soft plastic cam, seems unsatisfactory and bound to cause excessive wear. The cam on the faulty vaporizer was badly worn after only 8 months' use. The rim of the concentration setting dial could be used as a cam, with different machining for different models, from the same stock of parts. A spring made of plastic in the same way as the one-piece hinges found on some plastic boxes would avoid the wear problem.