Introduction: Although several improvements have been observed in the latest years in shunt technology, current available systems still present several associated problems. Among these ‘overdrainage’ and its complications remains one of the great challenges for new shunt designs.

Methods: In order to address the so-called, “Siphoning Effect”, the “Paddle Wheel Valve” has been designed as a concept in which, by placing the pressure sensor in a separate chamber, the activation pressure and the pressure gradient across the valve are decoupled.The authors employed computer models to theoretically analyze the mechanical variables involved in the operation of the valve. After fabrication of the first superscaled model, the authors performed benchmark testing in order to analyze the new shunt device.

Results: After initial design of the ‘Paddle Wheel Valve’ the authors realized some problems such as silicone paddles’ deformation and excessive friction between the paddles and the inner housing of the valve. The reformulation of the initial design lead to the addition of a pressure chamber which is capable of controlling the drainage through the valve based solely on the intracranial pressure independently of the pressure gradient across the valve. Further testings were performed in order to prove that the siphoning pressure did not activate the valve.

Conclusions: The design of the ‘Paddle Wheel Valve’ demonstrated that it is possible to decouple the activation pressure and the pressure gradient across the valve, avoiding activation of the valve by the ‘siphoning effect’. Although further developments are necessary in order to provide a model compatible to clinical use, the author believe that this new prototype may be an interesting solution for future attempts addressing the solution of the problem of overdrainage due to siphoning.

Patient Care: Will provide readers an overview about current challenges for developing new shunt systems. Will Improve the design of new shunts as well as new alternatives for addressing the siphoning effect.

Learning Objectives: - To realize the importance of the 'siphoning effect' on the design of new shunt models - To be able to explain the possible mechanical designs in order to address the siphoning effect - To explain the importance of the new 'paddle-whell' model as an alternative to overcome the siphoning effect

References: 1. Pollack I, Albright A, Adelson P, Group H-MI. A randomized, controlled study of a programmable shunt valve versus a conventional valve for patients with hydrocephalus. Neurosurgery 1999;45:1399-411. 2. Browd SR, Gottfried ON, Ragel BT, Kestle JR. Failure of cerebrospinal fluid shunts: part II: overdrainage, loculation, and abdominal complications. Pediatr Neurol. 2006 Mar;34(3):171-6. 3. Tokoro K, Chiba Y, Abe H, Tanaka N, Yamataki A, Kanno H.Importance of anti-siphon devices in the treatment of pediatric hydrocephalus. Childs Nerv Syst. 1994 May;10(4):236-8. 4. Pudenz RH, Foltz EL: Hydrocephalus: overdrainage by ventricular shunts. A review and recommendations. Surg Neurol 35: 200–212 1991