High-resistance proximal "scaled" ventricular catheters.

ABSTRACT

PURPOSE: Prove the concept of high-resistance proximal catheters for valve-independent treatment of hydrocephalus. METHODS: A preliminary design process yielded optimal high-resistance proximal ventricular catheters with a "scaled" design and parallel-oriented, U-shaped inlets. Prototypes were manually constructed using carving tools to stamp through silicone tubings. A testing apparatus was developed to simulate cerebrospinal fluid flow through a catheter, and the prototypes were tested against a control catheter for exhibition of an "on/off" phenomenon whereby no flow occurs at low pressures, and flow begins beyond a pressure threshold. Flow distribution was visualized with India ink. Regression analysis was performed to determine linearity. RESULTS: The new designs showed varying amounts of improved flow control with the "scaled" design showing the most practical flow rate control across various pressures, compared to the standard catheter; however, no true "on/off" phenomenon was observed. The "scaled" design showed various degrees of dynamism; its flow rate can be time dependent, and certain maneuvers such as flushing and bending increased flow rate temporarily. Variation in the number of inlets within each "scaled" prototype also affected flow rate. Contrastingly, the flow rate of standard catheters was found to be independent of the number of inlet holes. Ink flow showed even flow distribution in "scaled" prototypes. CONCLUSIONS: This initial feasibility study showed that high-resistance ventricular catheters can be designed to mimic the current/valved system. The "scaled" design demonstrated the best flow control, and its unique features were characterized.