Reliability of epidural pressure measurement in clinical practice: behavior of three modern sensors during simultaneous ipsilateral intraventricular or intraparenchymal pressure measurement.

OBJECTIVE

In recent years, new devices for epidural pressure (EDP) measurement have been developed, with claims of improved accuracy. However, there have been no new data from simultaneous pressure measurements to reverse the skepticism regarding this technique.

METHODS

The reliability of EDP recording was investigated in 26 patients with severe head injuries, during simultaneous measurement of ipsilateral intraventricular pressure (IVP) or intraparenchymal pressure (IPP).

RESULTS

Periods of simultaneous measurement ranged from 3.3 to 168 hours. Technical failure occurred in five cases. Clinically significant erroneous pressure values (defined as differences of >10 mm Hg between EDP and IVP or IPP, lasting for >10 min) occurred in 7 of 21 measurements (33%). In three of these seven cases (43%) the difference between the EDP and the IVP or IPP remained nearly stable throughout the period of observation, whereas in four cases (57%) significant drifting over time was observed. Analysis of the transfer function calculated for the first to sixth harmonics between the EDP and the IVP or IPP showed no significant differences between the pulse pressure waveforms, even when significant drifting of more than 20 mm Hg occurred.

CONCLUSION

The reliability of EDP measurement has not improved, compared with 10 years ago. Using this technique, one must be aware of the possibility of overestimating intracranial pressure by more than 10 mm Hg and the possibility of significant drifting of EDP over time, which argues against the use of this method even for trend analysis.