This blood, the fluid, is pushed into the skull with every heartbeat, every second. Once the brain has extracted the necessary oxygen and gotten rid of carbon dioxide from the fluid, there is a drainage system that drains the fluid to other parts of the body. This must be done otherwise the pressure inside the skull becomes too high. However, according to Project Brain Drain, in one in 500 people the drainage system does not work properly, thus increasing pressure, crushing the brain and ultimately killing them. Neurosurgeons have developed a medical device called a shunt that can alleviate this drainage problem, but it is quite invasive. A shunt is placed directly in the skull and is a one-way valve that drains excess fluid. This device works well except that this flow tends to drag debris into the pipe and in about 40% of cases it clogs. As a result, many shunt patients develop symptoms such as headaches, vomiting and neurological problems, and once they develop these symptoms doctors have no idea whether these symptoms are due to an illness or an increase in blood pressure, which could be fatal. “One of the problems is that we don't even know the pressure we're dealing with, and we certainly don't know if the mechanical valves meet that particular patient's pressure requirements,” he said