Physical Background - miethke GAV Gebrauchsanweisung

GAV

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)
horizontal: IVP = P
IVP = P
vertical:
IVP Intraventricular pressure
P Opening pressure in horizontal position
L
(adjustable DP-unit only)
P Opening pressure in vertical position
S
(adjustable DP-unit + gravitational unit)
P Pressure in the abdominal cavity
B
P Hydrostatic pressure
H
IVP
Fig. 2: Calculating the intraventricular pressure for horizontal and vertical body position
+ P
L B
- P - P
H S B
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.
P
L
P
B
INSTRUCTIONS FOR USE |
P
H
GB
IVP
P
S
P
B
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