In vitro performance of combinations of anti-siphon devices with differential pressure valves in relation to the spatial position

Programmable differential pressure valves (DPV) in combination with a fixed anti-siphon device (ASD) represent the present standard of care in preemtping overdrainage associated with ventriculoperitoneal shunting for hydrocephalus. Our aim was to provide comparative data of six combinations of two ASDs with different working principles in combination with three DP valves in an in vitro shunt laboratory achieving a better understanding of their flow characteristics and potential clinical application. We analyzed the flow performance of six possible combinations of three DP valves (CHPV [HM]; proGAV 2.0[PG]); Codman CertasPlus (CP) in combination with either a gravity-regulated (Shuntassistant [SA]) or a flow-regulated (SiphonGuard [SG]) ASD. A DP between 4 to 60 cmH2O was generated and the specific flow characteristics were measured. In addition, the three combinations with gravity-regulated ASDs were measured in defined spatial positions. Flow characteristics of the SA combinations corresponded to the DP in linear fashion and to the spatial position. Flow characteristics of the SG combinations were dependent upon the DP in a non-linear fashion and independent of the spatial position. Highest mean flow rate of the PG-SG- (HM-SG-) combination was 1.41 ± 0.24 ml/min (1.16 ± 0.06 ml/min). The meanflow rates sharply decreased with increasing inflow pressure and subsequently increased slowly up to 0.82 ± 0.26 ml/min (0.77 ±0.08 ml/min). In an experimental setup, all six tested device combinations were able to control the siphon effect which arises in the vertical position. The valve combinations prevent consecutive excessive flow to varying degrees. However, significant differences in flow characteristics can be seen, which might be relevant for their clinical application.2021-09-1