A comparative study of the Spiegelberg compliance device with a manual volume-injection method: a clinical evaluation in patients with hydrocephalus.

A new automated method of compliance measurement has been developed which may overcome some of the problems of the manual method. Measurement of craniospinal compliance in brain-injured patients offers the potential for early detection of raised intracranial pressure (ICP) before it rises to levels that may damage brain parenchyma. However, limitations of the existing manual volume pressure techniques have meant few centres routinely perform compliance testing. We report on the results of testing this new method against a manual volume pressure response method (VPR) in 10 patients with hydrocephalus. In this comparison study, 19 pairs of compliance measurements were obtained from 10 patients. The compliance values obtained ranged from 0.141 to 1.407 ml/mmHg. There was a good correlation between the two methods (r2 = 0.8508). The average bias in compliance between the two methods was 0.111 ml/mmHg (95% CL for the bias = 0.0438, 0.1788) with the new method reading higher compliance than the manual method. These results indicate that the new automatic method of compliance measurement correlates well with an independent and classical measurement of compliance, and defines the bias and limits of agreement by which the new method measures craniospinal compliance in patients with hydrocephalus. Further work is needed to validate this device over a wider compliance range, especially at the lower compliance range often found in head injured patients. Studies are also required to determine the normal range of compliance values in the patient populations who undergo ICP monitoring. Research into determining which patient populations may benefit from continuous compliance measurement is warranted.