Investigation: visual inspection: no significant deformations or damage of the valve were detected during the visual inspection.Permeability test: a permeability test has shown that the valve is permeable.Adjustment test: this is a fixed pressure valve.An adjustment test is not applicable.Braking force and brake function test: this is a fixed pressure valve.A braking force and brake function test is not applicable.Computer controlled test: to investigate the claim of blockage, the opening pressure is measured using a miethke computer controlled testing apparatus which simulates a cerebrospinal fluid flow.The valve is tested in the vertical positions.The result show that the valve is not operating within the acceptable tolerances.Results: first, we performed a visual inspection of the valve.No significant deformations or damage of the valve were detected during the visual inspection.Next we tested the permeability of the valve.The valve was shown to be permeable.Then we carried out a computer controlled simulated flow test.The measured opening pressure was not within the accepted tolerance range.The opening pressure was minimal lower than expected, indicating a tendency towards over-drainage.Finally, we have dismantled the valve.Inside the valve we have found a minimal build-up of visible substances (likely protein).Based on our investigation, we are unable to substantiate the claim of occlusion.At the time of our investigation the valve was shown to be permeable.Despite the lack of significant deposits, it is possible that even non-visible or small amounts of build-up could have led to a temporary compromise of the valve and to the observed malfunction in the past.As described in scientific literature, the problem encountered is one of the known, inevitable risks of hc-therapy by shunt implants.We can exclude a defect at the time of release.The valve met all specifications of the final inspection when released from christoph miethke (b)(4).No further regulatory actions are required from our point of view.
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