GAV ®

The GRAVITY ASSISTED VALVE is a posture-dependent valve. It is made from titanium, a material that guarantees outstanding precision, reliability and biocompatibility. It is MRI-conditional and is unaffected by subcutaneous pressure.

The valve consists of a sturdy titanium casing, which houses in its proximal section, a ball-cone valve. A spiral spring maintains the opening pressure of the ball-cone unit. The gravitational unit at the distal end of the valve contains a tantalum and sapphire ball. The sapphire ball ensures precise closure of the gravitational unit. 

Horizontal position

When the patient is supine, the ball-cone unit of the GAV controls the intraventricular pressure (IVP). The freely moving balls in the gravitational unit do not provide any resistance when the patient is supine, and therefore the flow channel is always open in this position. The ball-cone valve is closed however, thus preventing any drainage, shown on the left depiction. If the patient's IVP increases and continues to rise, the spring pressure of the ball-cone unit will eventually be overcome and the sealing ball will move away from the cone. Now the GAV is open and CSF can flow, shown on the right depiction. 

Vertical position

As soon as the patient stands up, the tantalum and sapphire balls close the gravity valve and fluid drainage is interrupted. This prevents overdrainage effectively. Fluid drainage resumes only once the intraventricular pressure exceeds the sum of the opening pressures of both the ball-cone and gravitational units.