As long as the patient is lying down, the intraventricular pressure is controlled exclusively by the Differential pressure unit of the GRAVITY ASSISTED VALVE. The freely movable balls of the gravity unit do not provide any additional resistance when the patient is lying down and automatically keep the flow channel open at this point. In the illustration a), the Differential pressure unit is closed and prevents any liquor drainage. If the intraventricular pressure increases, this force acts on the Differential pressure unit and finally causes the spring to give way and a gap to form between the cone and the ball, which now allows the cerebrospinal fluid to flow. In the illustration b), the GAV is open.

In the upright position, the gravitational unit is automatically activated when the balls fall down. A higher valve opening pressure is established, since the opening pressures of both valve mechanisms (differential pressure and gravitational unit) must now be overcome. If the patient therefore straightens up, the gravitational unit closes and the risk of overdrainage is reduced. If the sum of both valve units is exceeded by the increasing intraventricular pressure, the valve opens and thus enables the necessary drainage of the cerebral fluid.