Function Of The Valve - MIETHKE proGAV 2.0 Mode D'emploi

proGAV 2.0
Major components in the gravitational unit are
a tantalum ball (6), which defines the opening
pressure for this valve depending on the body
position and a sapphire ball (7), which ensures
precise closure.

FUNCTION OF THE VALVE

The proGAV 2.0 is a posture dependent hydro-
cephalus valve. The opening pressure for the
proGAV 2.0 is composed of the opening pres-
sures for the adjustable differential pressure
unit and the gravitational unit.
Horizontal position
In the horizontal position, the gravitational unit
is always open and does not present any
resistance.
Fig. 2: Gravitational unit in horizontal body position
Consequently, the opening pressure of the
proGAV 2.0 in the horizontal body position
is characterised by the adjustable differential
pressure unit. The principal working method
used by the adjustable differential pressure
unit is shown in Fig. 3a and 3b. In Fig. 3 it is
closed so that no drainage is possible. In Fig.
3b, the adjustable differential pressure unit is
shown in the open state.
Fig. 3: Adjustable differential pressure unit in
horizontal body position a) closed b) open
INSTRUCTIONS FOR USE | GB
The intraventricular pressure (IVP) of the
patient is increased and the spring force which
would otherwise keep the differential pressure
unit closed is overcome. Now, the sealing ball
moves out of the cone and a gap is sealing for
liquor drainage.
Vertical position
When the patient moves into an upright posi-
tion, in that moment the gravitational unit
closes (fig. 4a). Now, additionally to the open-
ing pressure of the adjustable DP-unit, the
weight of the tantalum ball has to be exceeded
(opening pressure of the gravitational unit),
thus the opening pressure of the proGAV
2.0 is significantly increased. Only when the
sum of the IVP and the hydrostatic pressure
exceeds the opening pressure of the proGAV
2.0, drainage will be possible again (Fig. 4b).
Fig. 4: Gravitational unit in vertical body position
a) closed b) open
During physical activity which is associated
with vibrations (for example jogging) the open-
ing pressure of the proGAV 2.0 can decrease
temporarily by 25 % to 35 % according to lab-
oratory results. This affects both the individ-
ual valve and the combination with a gravita-
tional unit. As a basic principle, functionality
is retained. At the end of physical activity, the
opening pressure returns to its original level
and remains stable.
15