A prospective comparison of fibre-optic and fluid-filled single lumen bolt subdural pressure transducers in ventilated neurosurgical patients

A clinical comparison was made between fibre-optic and fluid-filled Bolt subdural pressure transducers in ventilated head injured patients. Twelve subjects had both devices inserted in neighbouring sites. In two patients there were obvious technical problems with the fibre-optic system and the results were therefore excluded from further analysis. In the remaining 10 patients, 2167 pairs of simultaneous recordings were made for up to 9 days and the degree of correspondence studied. A quarter of paired readings differed by more than 5 mmHg. There was no evidence of any overall bias, but in individual patients one device often read higher or lower than the other. The proportion of closely corresponding readings tended to diminish after 4 days. Therapeutically relevant episodes, where treatment might have been initiated on the basis of the readings from only one of the two systems, were equally likely with both devices and occurred on average approximately every 30 h. The relative accuracy of the two devices remains uncertain, but there is evidence suggesting that both were prone to errors.