The Rotterdam teletransducer: State of the device

The developments of a telemetric device for monitoring intracranial pressure, the Rotterdam Teletransducer, are described. The major problem in telemetric pressure sensing devices consists of diffusion of water into the transducer, resulting in unpredictable zero drift. Therefore, special attention was paid to bonding techniques for sealing the transducer. The results of improved epoxy sealing, active metal brazing and glass bonding are described. In vitro tests showed transducers sealed with epoxy resin to be stable for two months. Using the more complicated tchniques of glass bonding and active metal brazing, hermetic seals could be achieved with stable transducers for over one year. In vivo functioning of the Rotterdam Teletransducer was tested in acute and chronic animal experiments. The in vivo results corresponded to those obtained in the in vitro experiments. Regression analysis between epidural and ventricular fluid pressure showed a one to one ratio. Results of clinical application of the device in 22 patients are described. Accurate depth setting of the transducer on the dura, according to the pressure depth curve, was shown to be essential. The device has also been used with success for non-invasive fontanelle pressure measurements in infants. The depth positioning of the transducer on the fontanelle according to a pressure depth curve is described.