Wade-Dahl-Till valve

Dahl's son Theo, suffering from hydrocephalus, had had a standard Holter shunt installed to drain excess fluid from his brain; however the shunt jammed too often, requiring emergency surgery.

Till determined that debris accumulated in the hydrocephalic ventricles could clog the slits in the Holter valves, especially with patients, such as Theo, who had had bleeding in the brain. Till, Dahl and Dahl's friend Wade developed a new mechanism using two metal discs, each in a restrictive housing at the end of a short silicon rubber tube. Fluid moving under pressure from below pushed the discs against the tube to prevent retrograde flow; pressure from above moved each disc to the "open" position.

By the time the device was perfected, Theo had healed to the point at which it was not necessary for him; however several thousand of other children benefited from the WDT valve before medicine technology progressed beyond it.

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