Non-invasive ICP monitoring in infants: the Rotterdam Teletransducer revisited.

Measurement of intracranial pressure (ICP) is important in patients at risk of raised ICP, as in hydrocephalus. Ideally, it should be non-invasive, thus avoiding the risk of infection and other complications: Such is provided by measurement of ICP through the anterior fontanelle. There are several methods of measuring anterior fontanelle pressure (AFP); those most frequently used are based on the applanation principle. An evaluation of AFP measurement devices resulted in the choice of the Rotterdam Teletransducer (RTT) to be used in our study of children with hydrocephalus. The literature contains little information on the accuracy or validation of the AFP measurements using the RTT. Therefore, the physical qualities of the RTT were reassessed, using a specially developed calibration device. The results of this study demonstrate that membrane temperature does not have any effect on the measured pressure. The thermal stabilization time of the RTT was found to be 3 h after switching on. Insufficient thermal stabilization results in a pressure underestimation of up to 3 mmHg. Furthermore, a maximum inaccuracy of 2.6 mmHg, after calibration and readjustment of the transducer, was calculated. Validation of the equipment was achieved by simultaneous AFP/ICP measurements in hydrocephalic patients showing high correlations (r = 0.96-0.98). The discussion suggests a measurement protocol as a means of increasing the reliability of RTT measurements.