gms | German Medical Science

Objective: Adjustable differential pressure valves in combination with anti siphon devices (ASD) of various working principles are implanted to overcome overdrainage-related complications associated with ventriculoperitoneal shunting. We aimed to provide comparative data on the flow characteristics of two anti-siphon devices of different working principles in combination with different types of differential pressure devices, in order to achieve a better understanding of these device combinations and their potential clinical application.

Methods: We analyzed three differential pressure valves (Codman Hakim programmable valve, Codman CertasPlus and Miethke proGAV) in successive combination with the gravity dependent Miethke Shuntassistant [SA] and the flow dependent Codman SiphonGuard [SG]. Defined pressure conditions within a simulated shunt system were generated (differential pressure 4–60 cmH2O) and the specific flow characteristics were measured. In addition, the combinations with gravity-dependent proGAV were measured in defined spatial positions (0–90°).

Results: The flow characteristics of the three differential pressure valves in combinations with the SA were dependent upon differential pressure and their spatial position. All three device combinations were able to reduce the siphoning effect to a similar extent (flow at inflow pressure: 20 cmH2O, siphoning -40 cm H2O at 0°/90°: proGAV set at 8 cmH2O, 11.53±0.22/7.87±0.22 ml/min; Hakim set at 80 mm H2O, 11.61±0.13/7.70±0.18 ml/min; CertasPlus set at level 3, 12.45±0.09/8.86±0.14 ml/min, compared to control, 16.43±0.09 ml/min; p<0.001). The flow characteristics of the differential pressure valves in combination with the SG were primarily dependent upon the differential pressure. The highest mean flow of 1.41±0.24 ml/min was documented in combination with a proGAV (set at 4 cm H2O, inflow pressure 10 cm H2O), which sharply declined with increasing inflow pressure (0.23 ml/min, inflow pressure 20 cm H2O) and subsequently increased slowly up to 0.82 ml/min (inflow pressure 60 cm H2O).

Conclusion: All tested device combinations were able to control siphoning effect and consecutive excessive flow within a simulated shunt system, but to differing degrees. As such, the two different types of ASDs demonstrated significant differences in flow characteristics, which may be relevant for their clinical application.