Indication; Technical Description; Physical Background - MIETHKE paediGAV Mode D'emploi

| INSTRUCTIONS FOR USE
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INDICATION

The paediGAV is intended for use in cases of
pediatric hydrocephalus for the drainage of
cerebrospinal fluid from the ventricles into the
peritoneum.

TECHNICAL DESCRIPTION

The paediGAV is a position-sensitive valve for
the treatment of hydrocephalus. It comprises a
ball-cone unit and a gravitational unit. By this de-
sign, physiological drainage can be assured in-
dependent of the physical position of the patient.
ball-cone unit
gravitational unit
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paediGAV
Fig. 1 shows a schematic cross section of
the paediGAV. It consists of a sturdy titanium
casing, which houses, in its proximal section,
a welltried ball-cone unit. A spiral spring (2)
maintains the opening pressure of the ball-cone
unit. The gravitational unit in the distal part con-
sists of a tantalum ball (3), which defines the
opening pressure of this valve, and a sapphire
ball (4), which ensures its precise closure.
As an option, a connector or a silicone catheter
is installed at the distal end of the valve. Coding
rings (1) allow the identification of the pressure
setting in an x-ray image. The paediGAV regu-
lates the intraventricular pressure (IVP) for the
patient being in a horizontal or in a standing
position.
3
4
1 coding ring
2 spiral spring
3 tantalum ball
4 sapphire ball
Fig. 1: Schematic cross section of the paediGAV
paediGAV

PHYSICAL BACKGROUND

The intraventricular pressure is positive in a
healthy human in a horizontal position. To ad-
just this pressure through shunt drainage, one
has to choose the appropriate pressure range,
taking into account the abdominal cavity pres-
sure. The resulting IVP is the sum of the shunt
opening pressure and the abdominal cavity
pressure (fig.2)
IVP Intraventricular pressure
PVli Opening pressure (horizontal)
(ball-cone unit only)
PVst Opening pressure (vertical)
(ball-cone unit+ gravitational unit)
PB Pressure in the abdominal cavity
PHyd Hydrostatic pressure
horizontal: IVP = PVli + PB
vertical: IVP = PHyd - PVst - PB
1
2
P
IVP
P
Fig. 2: The pressure conditions for horizontal and standing positions
The ventricular pressure in a healthy human in
a vertical position becomes slightly negative.
To maintain this pressure by means of shunt
drainage, the shunt opening pressure has to be
significantly higher so that the shunt can com-
pensate the hydrostatic pressure minus the
sum of the abdominal cavity pressure and the
slightly negative intraventricular pressure.
Conventional shunts open immediately as soon
as the patient stands up, which can lead to cri-
tical overdrainage.
Vli
B
INSTRUCTIONS FOR USE |
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IVP
P P
Hyd Vst
P
B
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