Physics Background - MIETHKE miniNAV Instrucciones De Manejo

miniNAV

PHYSICS BACKGROUND

The intraventricular pressure is positive in a
healthy human in a the horizontal position. To
maintain this pressure through shunt drainage,
one has to choose the appropriate pressure
range, taking into account the abdominal ca-
vity pressure. The resulting IVP is the sum of
the shunt opening pressure and the abdominal
cavity pressure (fig. 6).
IVP Intraventrikular pressure
PVli Opening pressure (hoizontal)
PVst Opening pressure (vertical)
PB Pressure in the abdominal cavity
PHyd Hydrostatic pressure
hoirzontal: IVP = PVli + PB
vertical: IVP = PHyd - PVst - PB
IVP
Fig. 2: Pressure conditions in horizontal and vertical body positions
In a healthy human, the ventricular pressure in
the 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 for 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
Vli
P
B
INSTRUCTIONS FOR USE |
P
Hyd
GB
IVP
P
Vst
P
B
13