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 m ay overcome some of the problems of the manual method. Measurement: of cran iospinal compliance in brain-injured patients offers the potential for earl y detection of raised intracranial pressure (ICP) before it rises to levels that may damage brain parenchyma. However, limitations of the existing man ual volume pressure techniques have meant few centres routinely perform com pliance testing. We report on the results of testing this new method agains t a manual volume pressure response method (VPR) in 10 patients with hydroc ephalus. In this comparison study, 19 pairs of compliance measurements were obtained from 10 patients. The compliance values obtained ranged from 0.14 1 to 1.407 ml/mmHg. There was a good correlation between the two methods (r (2)=0.8508). The average bias in compliance between the two methods was 0.1 11 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 inde pendent and classical measurement of compliance, and defines the bias and l imits of agreement by which the new method measures craniospinal compliance in patients with hydrocephalus. Further work is needed to validate this de vice over a wider compliance range, especially at the lower compliance rang e often found in head injured patients. Studies are also required to determ ine the normal range of compliance values in the patient populations who un dergo ICP monitoring. Research into determining which patient populations m ay benefit from continuous compliance measurement is warranted.