Physical Background; Selecting The Appropriate Dsv Shuntsystem; Reading The Pressure Setting From An X-Ray Image - MIETHKE DUALSWITCH VALVE Instrucciones De Manejo

| INSTRUCTIONS FOR USE
GB

PHYSICAL BACKGROUND

In the lying-down position, the intraventricu-
lar pressure is positive in a healthy human. To
adjust this pressure using valve drainage, only
the pressure in the abdominal cavity has to be
taken into account.
Fig. 5 Calculation of the intraventricular pressu-
re for the horizontal and standing body position.
In the standing body position, the ventricular
horizontal: IVP = P + P
L B
standing: IVP = P - P - P
H S B
IVP Intraventricular pressure
P Opening pressure in horizontal position
L
(adjustable unit only)
P Opening pressure in vertical position
S
(adjustable + gravitational unit)
P Pressure in the abdominal cavity
B
P Hydrostatic pressure
H
IVP
Fig. 5: Pressure situation at the shunt for horizontal and vertical position
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pressure should be slightly negative. To regulate
ventricular pressure using shunt valve drainage,
valve opening pressure in standing position
must be set considerably higher. Only in this
way can the shunt valve compensate for the
hydrostatic pressure reduced by the pressure
in the abdominal cavity. Conventional valves
open instantly, as soon as the patient rises to
a standing position, and a critical overdrainage
may occur.
IVP
P
H
P
S
P
L
P
P
B
B
SELECTING THE APPROPRIATE
DSV SHUNTSYSTEM
The mode of operation of the DUAL SWITCH-
VALVE depends on the position of the patient.
It features two different opening pressures. One
opening pressure is effective when the patient
is in a horizontal position; the other is for the
patient standing upright. Percutaneous read-
justment of the valve characteristics is unne-
cessary, since the higher opening pressure in
the upright position counteracts any uninten-
tional overdrainage, while the lower opening
pressure in the horizontal position prevents
underdrainage.
Horizontal position:
For the horizontal position, four different ope-
ning pressure ratings are available (5, 10, 13
and 16 cmH O). The recommended standard
2
pressure rating is 10 cmH O (valve pressure at
2
a flow of 20 ml/h). The pressure rating 5 cmH
2
is available for normalpressure hydrocephalus
patients.
Vertical position:
The opening pressure for the standing position
depends on the body height of the patient (hy-
drostatics). The high-pressure side of the valve
is chosen in such a way that, with the patient
standing upright, a ventricular pressure of at
least -5 cmH O is maintained under all circum-
2
stances. The procedure is the following:
1) The distance between the third ventricle (at
the level of the Foramen Monroi) and the dia-
phragm of the patient is measured.
2) 5 cm are subtracted from the measured di-
stance.
3) The valve is chosen whose pressure rating for
the high-pressure side exceeds the measured
distance minus 5 cm by the smallest amount.
The available opening pressure ratings are 30,
40 and 50 cmH O. The ventricular pressure in
2
the patient will then be kept between -5 cmH
2
and +5 cmH O at all times.
2
INSTRUCTIONS FOR USE |
READING THE PRESSURE SETTING FROM
AN X-RAY IMAGE
Strict quality control is applied in the calibration
of each individual DUALSWITCH VALVE. The
following pressure level combinations, which
can also be read from an X-ray visible coding,
are available:
The code for the low-pressure side is always
situated close to the ball switch (white dot). The
code for the high-pressure side is always fur-
ther away from the ball switch, no matter on
which side of the ball switch the code is visible.
horizontal 5 cmH O:
2
O
5/30 5/40
Standard-valve: horizontal 10 cmH O:
2
10/30 10/40
horizontal 13 cmH O:
2
13/30 13/40
O
horizontal 16 cmH O:
2
16/30 16/40
GB
5/50
10/50
13/50
16/50
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