Clinical evaluation of a miniature strain-gauge transducer for monitoring intracranial pressure

IN 25 PATIENTS, we evaluated the accuracy of a new miniature strain-gauge transducer developed for the measurement of intracranial pressure (ICP). The ICP in each patient was measured with the intraventricular, miniature strain- gauge transducer, and that value was compared with the ICP measured with a ventriculostomy catheter coupled to an external strain-gauge transducer. From the two monitors, 2218 simultaneous measurements of ICP were obtained. The average ICP measured with the miniature strain-gauge transducer was 15.9 ± 10.0 mm Hg (range, -3 to 104 mm Hg). The ICP measured with the ventriculostomy-catheter transducer averaged 15.4 ± 10.1 mm Hg (range, -9 to 104 mm Hg). A highly significant correlation was found over the wide range of pressures observed (n = 2218, r = 0.97, P < 0.001). The average difference between the two measurements of the ICP was 0.5 ± 2.6 mm Hg, and the differences were equally positive and negative, demonstrating no consistent bias. The two values for the ICP were within 2 mm Hg of each other on 63% of the measurements and within 4 mm Hg of each other on 89% of the measurements. The average zero drift of the miniature strain-gauge transducer, measured at ambient pressure after removal of the catheter, was 0.2 ± 0.5 mm Hg. The results indicate that this miniature strain-gauge transducer is highly accurate and stable and that it is a reliable alternative to a ventriculostomy for monitoring the ICP.