Function Of The Valve - MIETHKE proGAV Instrucciones De Manejo

| INSTRUCTIONS FOR USE
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FUNCTION OF THE VALVE

The opening pressure of the proGAV is compo-
sed of the opening pressure of the adjustable
DP-unit and the opening pressure of the gra-
vitational unit.
Horizontal position
When the patient is lying down, the gravitational
unit is always open and therefore does not pre-
sent any resistance to the fl uid fl ow.
Hence, the opening pressure of the proGAV is
defi ned by the adjustable DP-unit. The operati-
onal principle of the adjustable DP-unit is illus-
trated in fi gures 3 and 4.
Fig. 3: Gravitational unit in horizontal position
In fi g. 4a, the ball-cone valve is closed. The
drainage is blocked. In fi g. 4b, the adjustable
DP-unit is shown in the open condition. The
patient's IVP is increased and the spring force,
which otherwise keeps closed the ball-cone
valve, is overcome. The closing ball moves out
of the cone and a gap opens to allow drainage.
a)
b)
Fig. 4: Adjustable DP-unit
a) closed b) open
22
Vertical position
As soon as the patient moves into an upright
position, the gravitational unit closes, the ope-
ning pressure of the proGAV is signifi cantly in-
creased and CSF drainage is blocked (fi g. 5a).
Only when the sum of the IVP and the hydrosta-
tic pressure exceeds the opening pressure of
the proGAV, drainage will be possible again (fi g.
5b). The opening pressure of the proGAV in the
vertical position is the sum of the opening pres-
sures of both the adjustable DP-unit and the
gravitational unit (weight of the tantalum ball).
a)
Fig. 5: Gravitational unit in vertical position
a) closed, b) open
proGAV
b)