Investigation: visual inspection: a deformation of the outer housing of the progav was observed through the visual inspection.The progav housing was subsequently measured and the presence of a deformation was confirmed.The housing deformation measured at -0.0510mm, outside the tolerance of 0 +/- 0.02mm.Permeability test: a permeability test has shown that the progav is permeable, although slower draining than expected.Adjustment test: the progav was tested and is adjustable to all specified pressures.Braking force and brake function test: the brake functionality test has shown that the brake function is fully operational and the braking force is within the given tolerances.Computer controlled test: to test the opening pressure, we use a miethke computer controlled testing apparatus which simulates a cerebrospinal fluid flow.The progav is not operating within acceptable tolerances.The opening pressure is higher than expected.Results: finally, we have dismantled the valve.Inside the valve we have found minimal evidence of deposits of substances (likely protein).Based on out investigation, we are unable to substantiate the claim of over-drainage.Conversely, we have determined that the valve is operating in a state of under-drainage and showing signs of blockage.This is likely due to the build-up observed inside the valve.Even slight or non-visible amounts of blood or protein found in the cerebrospinal fluid and deposited inside the valve can cause the observed malfunction.As described in our literature, the problem encountered is one of the known, inevitable risks of hc-therapy by shunt implants.
|