Bpm - Gambro AK 95 S Service Manual

BPM

The BPM (Blood pressure monitor) is physically
placed in the MM95.
The BPM monitor is a passive measuring device
that can issue attentions and alarms but the
alarms will not interfere with the
AK 95 S treatment.
The intended use for the BPM is to measure the
patient's blood pressure and to activate an alarm
if the patient's blood pressure goes under an
alarm limit set by the operator. This will give
the nurses the possibility to take measures be-
fore the patient suffers the ill effects of hypoten-
sion (low blood pressure).
The BPM module includes the following compo-
nents; air pump, bleed valve, dump valve, pres-
sure transducers (control and protective) and
microprocessor board. The module includes con-
trol and protective systems.
The control system measures the pressure and
pulse wave to calculate the systolic, diastolic,
mean blood pressure and pulse rate. The air
pump, dump and bleed valves are controlled by
this system as well as external communication.
The protective system supervises the maximum
pressure and inflating time. Maximum pressure
is 320 ± 10 mmHg and maximum inflating time
is 180 seconds. When these values exceed speci-
fied limits, dump and bleed valves are opened
and air pump is stopped by the protective sys-
tem.
A self-calibration/auto zero function is included
in the module, which means that the offset for
the pressure transducers is calibrated/adjusted
each time the module is turned on.
The BPM measures and calculates the non-inva-
sive blood pressure by using the oscillometric
method. This method uses the pulsation that
occurs in the artery in the arm when it is re-
stricted by the inflated cuff. The noise or oscilla-
tion originates from the fact that when the cuff
restricts the vessel, the flow in the vessel be-
comes turbulent, instead of laminar. The pulsa-
tion causes the pressure in the cuff to oscillate
which the pressure transducer in the BPM mod-
ule measures.
AK 95 / AK 95 S Service Manual
HCEN 9134 Rev. 10.2005
The relationship between the changes of cuff
pressure and its oscillation is used to determine
the blood pressure. When the BPM deflates the
cuff and the blood starts to pass the restriction,
the oscillation incline rapidly and the systolic
(high) pressure is measured. When the oscilla-
tion has peaked and is declining rapidly the dias-
tolic (low) pressure is measured. The mean pres-
sure is measured when the oscillation is peaking.
The heart rate is determined by using the pres-
sure oscillations measured by the pressure trans-
ducer.
When to measure the diastolic pressure is deter-
mined by extensive experiments to establish an
algorithm, which is included in the BPM soft-
ware.
In the field it is possible to perform a check of
the device to determine if it works or not.
The device has to be sent to Gambro for repair
incase of malfunction.
Technical Description
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