Automated time-averaged analysis of craniospinal compliance (short pulse response)

We have developed an automated method [Short Pulse Response (SPR)] of measuring craniospinal compliance using an electronic square wave pressure generator to produce a small (0.05 ml) and reproducible transient volume increase in the CSF space (pulse duration 100 msec). In experimental models of intracranial hypertension, arterial hypertension, arterial hypotension and arterial hypercarbia in cats, the new method accurately followed physiological changes in compliance when compared to the manual volume-pressure injection method. The VPR overestimated compliance compared to the new SPR method (by 20% to 162%, mean = 77%). The SPR method was less variable between sequential measurements with a coefficient of variation (CV) ranging from 0.6% to 9.6% (mean CV = 2.6%), compared with a CV ranging from 5.6% to 48% (mean CV = 17%) for the VPR method. Repeated compliance measurements by the new method over a 12 hour period, produced no neuropathological evidence of either blood brain barrier breakdown or tissue damage resulting from the repeated volume injections.