title: In vitro performance and principles of anti-siphoning devices.
abstract: BACKGROUND
  Anti-siphon devices (ASDs) of various working principles were developed to overcome overdrainage-related complications associated with ventriculoperitoneal shunting.
  
  
  OBJECTIVE
  We aimed to provide comparative data on the pressure and flow characteristics of six different types of ASDs (gravity-assisted, membrane-controlled, and flow-regulated) in order to achieve a better understanding of these devices and their potential clinical application.
  
  
  METHODS
  We analyzed three gravity-dependent ASDs (ShuntAssistant [SA], Miethke; Gravity Compensating Accessory [GCA], Integra; SiphonX [SX], Sophysa), two membrane-controlled ASDs (Anti-Siphon Device [IASD], Integra; Delta Chamber [DC], Medtronic), and one flow-regulated ASD (SiphonGuard [SG], Codman). Defined pressure conditions within a simulated shunt system were generated (differential pressure 10-80 cmH2O), and the specific flow and pressure characteristics were measured. In addition, the gravity-dependent ASDs were measured in defined spatial positions (0-90°).
  
  
  RESULTS
  The flow characteristics of the three gravity-assisted ASDs were largely dependent upon differential pressure and on their spatial position. All three devices were able to reduce the siphoning effect, but each to a different extent (flow at inflow pressure: 10 cmH2O, siphoning -20 cmH2O at 0°/90°: SA, 7.1 ± 1.2*/2.3 ±  0.5* ml/min; GCA, 10.5 ± 0.8/3.4 ± 0.4* ml/min; SX, 9.5 ± 1.2*/4.7 ± 1.9* ml/min, compared to control, 11.1 ± 0.4 ml/min [*p < 0.05]). The flow characteristics of the remaining ASDs were primarily dependent upon the inflow pressure effect (flow at 10 cmH2O, siphoning 0 cmH2O/ siphoning -20cmH2O: DC, 2.6 ± 0.1/ 4 ± 0.3* ml/min; IASD, 2.5 ± 0.2/ 0.8 ± 0.4* ml/min; SG, 0.8 ± 0.2*/ 0.2 ± 0.1* ml/min [*p < 0.05 vs. control, respectively]).
  
  
  CONCLUSIONS
  The tested ASDs were able to control the siphoning effect within a simulated shunt system to differing degrees. Future comparative trials are needed to determine the type of device that is superior for clinical application.
authors.affiliation: Department of Neurosurgery, Universitätsmedizin Göttingen, Georg-August University Göttingen, Göttingen, Germany.
authors.forename: Florian Baptist
authors.initials: FB
authors.lastname: Freimann
authors.forename: Takaoki
authors.initials: T
authors.lastname: Kimura
authors.forename: Florian
authors.initials: F
authors.lastname: Stockhammer
authors.forename: Matthias
authors.initials: M
authors.lastname: Schulz
authors.forename: Veit
authors.initials: V
authors.lastname: Rohde
authors.forename: Ulrich-Wilhelm
authors.initials: UW
authors.lastname: Thomale
mesh_terms: D015170:Cerebrospinal Fluid Pressure; D002557:Cerebrospinal Fluid Shunts / Q000295:instrumentation; D004867:Equipment Design; D006112:Gravitation; D006801:Humans; D006849:Hydrocephalus / Q000601:surgery*; D066298:In Vitro Techniques; D011312:Pressure; D019736:Prostheses and Implants; D017287:Ventriculoperitoneal Shunt / Q000295:instrumentation*