A clinical study of parenchymal and subdural miniature strain-gauge transducers for monitoring intracranial pressure.

OBJECTIVE

Previous studies have shown that a new strain-gauge MicroSensor (Codman/Johnson & Johnson Professional, Inc., Randolph, MA) for measuring intracranial pressure (ICP) performs well in the intraventricular space. We hoped to evaluate the MicroSensor in the subdural space and the brain parenchyma, because ICP is often measured in these compartments when the ventricles are difficult to cannulate.

METHODS

Fifteen patients had simultaneous recordings of ICP from an externally transduced fluid-filled subdural catheter, a MicroSensor placed within the subdural catheter, and a nearby MicroSensor placed intraparenchymally in the right frontal lobe.

RESULTS

The total number of valid simultaneous recordings of ICP was 95,946. A highly significant correlation was found between the tissue MicroSensor ICP (TMICP) and the subdural MicroSensor ICP (SMICP) (n = 95,946; r = 0.89; P < 0.00005), the TMICP and the fluid-transduced subdural catheter ICP (r = 0.86, P < 0.00005), and the fluid-transduced subdural catheter ICP and SMICP (r = 0.88, P < 0.00005). The mean simultaneous difference between the TMICP and the SMICP was 0.1 +/- 3.8 mm Hg with no obvious bias. The fluid-transduced subdural catheter ICP was 2.8 +/- 3.9 mm Hg lower than the TMICP and 2.7 +/- 3.9 mm Hg lower than the SMICP (P < 0.0005). The mean zero drifts of the tissue and subdural MicroSensors were 0.312 and 0.475 mm Hg/d, respectively. The tissue MicroSensor recordings showed the best quality wave form with the least damping.

CONCLUSION

The strain-gauge MicroSensor is highly accurate and stable in the tissue and subdural spaces.