Abstrict
A wrist type bloodpressure monitor (1) is provided with an interface
connector (16) for calibration purposes. The correct values of the
blood pressure are measured with a calibration device (20) including
an upper arm blood pressure measuring monitor (11). The values (D',
S') measured in this way are used to recalibrate the wrist type
blood pressure monitor (1). The wrist type blood pressure monitor
(1) is therefore provided with an editable memory (5) for the purpose
of recalibration.
Claims
What is claimed is:
1. A self-contained wrist-type blood pressure monitor comprising:
(i) an inflatable cuff adapted to be placed around the wrist of
a patient; (ii) a pressure sensor for measuring the pressure within
said cuff; (iii) a calculating arrangement for calculating diastolic
and systolic blood pressure values based on pressure values measured
within said cuff, which has an editable memory provided with calibration
data such as calibration data to be used in the calculation process
of the calculation arrangement; (iv) an interface connector being
connectable to the interface connector of a calibrating device for
calibration of the wrist type blood pressure monitor, whereby calibration
data provided by the calibration device is storable in the editable
memory of the calculation arrangement.
2. A self-contained wrist-type blood pressure monitor according
to claim 1, wherein the blood pressure monitor has a battery compartment
and wherein said interface connector is arranged within or next
to said battery compartment.
3. A self-contained wrist-type blood pressure monitor according
to claim 2, wherein said interface connector is adapted to be connected
to an external power supply during calibration.
4. A self-contained wrist-type blood pressure monitor according
to claim 1, wherein the editable memory is an EEPROM.
5. A system for calibrating a wrist type blood pressure monitor,
system comprising: (a) a self-contained wrist type blood pressure
monitor adapted to measure the diastolic and systolic blood pressure
of a patient, said monitor having (i) an inflatable cuff adapted
to be placed around the wrist of a patient; (ii) a pressure sensor
for measuring the pressure within said cuff; (iii) a calculating
arrangement for calculating diastolic and systolic blood pressure
values based on pressure values measured within said cuff, said
calculating arrangement having an editable memory; (iv) an interface
connector; (b) a calibration device for calibrating the wrist type
blood pressure monitor, said calibration device having (i) an inflatable
cuff adapted to be placed around the upper arm of a patient; (ii)
a pressure sensor for measuring the pressure within said cuff; (iii)
a calculating arrangement for calculating blood pressure values
based on pressure values measured within said cuff, having an interface
connector; the interface connector of the wrist type blood pressure
monitor being connectable to the interface connector of the calibrating
device for calibration of the wrist type blood pressure monitor,
whereby calibration data provided by the calibration device is storable
in the editable memory of the wrist type blood pressure monitor.
6. A system according to claim 5, whereby the calibration device
provides power supply for the wrist type blood pressure monitor
during calibration.
7. A system according to claim 6, wherein the wrist type blood
pressure monitor has a battery compartment and wherein the interface
connector is arranged within or next to said battery compartment.
8. A system according to claim 5, wherein the editable memory of
the wrist type blood pressure monitor is an EEPROM.
9. A method for calibrating a self-contained wrist type blood pressure
monitor having an inflatable cuff adapted to be placed around the
wrist of a patient and to determine the diastolic and the systolic
blood pressure of the patient, said method comprising the steps
of: a) measuring the patient's blood pressure with the wrist type
blood pressure monitor to be calibrated; b) before or after step
a), coupling the wrist type blood pressure monitor and an upper
arm blood pressure monitor together via respective interface connectors;
c) measuring the blood pressure with the upper arm pressure monitor;
d) comparing the blood pressure values obtained in steps a) and
b); e) depending on the results of step d), recalibrating the wrist
type blood pressure monitor, if necessary; and f) after step c),
d) or e), uncoupling the wrist type blood pressure monitor from
the upper arm blood pressure monitor.
10. A method according to claim 9, wherein steps a) and c) are
repeated, preferably three times, before step d).
11. A method according to claim 9, comprising a further step of,
before carrying out step d), verifying that the blood pressure values
measured in steps a) and/or c) are within a predetermined range.
12. A method according to claim 11, wherein steps a) and/or c)
are repeated once more if the values of the blood pressure are not
within the predetermined range.
13. A method according to claim 9, wherein a pause is made between
steps a) and c) or between subsequent repetitions of steps a) and
c).
14. A method according to claim 9, wherein during calibration,
power for the wrist type blood pressure monitor is supplied by the
calibration device.
Description The present invention relates to a blood pressure monitor, a calibrating
device and system and a method for calibrating a wrist type blood
pressure monitor.
It is well known to use electronic blood pressure monitors for
measuring the blood pressure on a patient. Mainly in the field of
blood pressure monitors for home it is also known to measure the
pressure around the wrist of the patient. This is preferred because
of the easier application of the pressure cuff around the wrist
as compared to the upper arm.
With regard to the quality of the measurement, wrist type blood
pressure monitors are, however, somewhat less favourable. Wrist
type blood pressure monitors have always a higher interindividual
scattering of the measurement accuracy. This is due to the sensitive
and complicate anatomical situation on the human wrist. While in
the wrist, there are two arteries, the ulnar and the radial artery,
the upper arm comprises just one artery. Measurements on the upper
arm are known since a long time and therefore have less uncertainties.
Known blood pressure monitors are calibrated for an anatomical
situation which corresponds to an average patient. This calibration
may not be adapted to patients having e.g. relatively small or large
wrist in the case of wrist type monitors.
It is an object of the present invention to overcome the draw-backs
of the prior art, especially to provide a wrist type blood pressure
monitor which allows an optimum measurement of the blood pressure
on the wrist also for patients who have a different anatomical situation
as compared to the average patient. A further object of the invention
consists in providing a calibration device for calibrating a wrist
type blood pressure monitor. Still a further object of the invention
consists in providing a system for calibrating a wrist type blood
pressure monitor. An other object of the invention consists in providing
a method for calibrating a wrist type blood pressure monitor. The
blood pressure monitor shall be simple and economic to manufacture
and easily to use and apply.
According to the present invention, these objects are solved with
a blood pressure monitor, a calibrating device, a calibration system
and a method for calibrating a wrist type blood pressure monitor
having the features of the independent patent claims. Calibrating
shall mean in the context of the application any adjustment or modification
of data stored in a memory in the BPM and used for calculating the
blood pressure values.
The blood pressure monitor according to the invention comprises
in a known manner an inflatable cuff e.g. adapted to be placed around
the wrist of a patient, a pressure sensor for measuring the pressure
within the cuff and a calculating arrangement for calculating the
blood pressure values based on pressure values measured within the
cuff. Such blood pressure monitors are known to those skilled in
the art. The blood pressure values, i.e. the systolic and the diastolic
blood pressure are determined e.g. with the oscillometric method.
According to the present invention, the calculating arrangement
comprises an editable memory for storing data such as calibration
data to be used in the calculation process of the blood pressure
values within the calculating arrangement. Modifiable data can also
be the weight, age or other parameters of the user. In contrast
to know blood pressure monitors, where calibration data are pre-set
in the factory, the present invention allows to recalibrate the
blood pressure monitor by editing the calibration data in the memory.
If e.g. a user becomes aware of the fact, that measured values are
continuously too high or too low, the blood pressure monitor can
be recalibrated. Obviously, the present invention is also useable
for calibrating others than wrist type blood pressure monitors,
such as finger type monitors or also upper arm monitors, if a reasonable
reference site is available.
In a preferred embodiment, the blood pressure monitor comprises
an interface connector which is connectable to a calibration device.
The calibration device especially may comprise an upper arm type
blood pressure monitor. For calibrating the wrist type blood pressure
monitor, the blood pressure is measured with the usually more accurate
upper arm blood pressure monitor. Other reference measurement sites
are also conceivable.
The wrist type blood pressure monitor can be connected to the calibration
device via the interface connector. The calibration data on the
editable memory can thereafter be adapted in accordance with the
blood pressure values measured with the upper arm type blood pressure
monitor.
In a further preferred embodiment, the blood pressure monitor comprises
a battery compartment for batteries. The interface connector is
preferably arranged within this battery compartment. The interface
connector therefore is not visible to the user if the battery compartment
is closed.
The interface connector is preferably adapted to be connected to
an external power supply during calibration. The external power
supply can be especially provided by the calibration device. For
connecting the interface connector of the wrist type blood pressure
monitor to the calibration device, the batteries must be removed
first. As soon as the wrist type blood pressure monitor is connected
to the calibration device, power for the wrist type blood pressure
monitor is supplied by the calibration device.
The editable memory is preferably an EEPROM or a flash-RAM which
can be arranged in addition to a memory on the chip of the monitor
in which the factory values are stored.
The calibration device for calibrating a wrist type blood pressure
monitor according to the present invention comprises a inflatable
cuff adapted to be placed around the upper arm of a patient, a pressure
sensor for measuring the pressure within the cuff and a calculating
arrangement for calculating the blood pressure values based on the
pressure measured within the cuff. According to the invention, the
calculating arrangement comprises an interface connector connectable
with a wrist type blood pressure monitor. Calibration information
based on the measurement of the blood pressure made on the upper
arm is transferred to the wrist type blood pressure monitor via
the interface connector.
The calibrating device preferably comprises a power supply for
the wrist type blood pressure monitor during calibration.
A system for calibrating a wrist type blood pressure monitor mainly
comprises a calibration device and an upper arm blood measuring
monitor. The calibration device is connected or connectable to the
wrist type blood pressure monitor. Preferably, the calibration device
and the upper arm blood measuring monitor form one unit.
The method for calibration a wrist type blood pressure monitor
according to the invention comprises the following steps: a) The
blood pressure of a patient is measured with the wrist type blood
pressure monitor to be calibrated. b) Before or after step a), the
blood pressure is measured with an upper arm blood pressure monitor.
c) The blood pressure values obtained in steps a) and b) are compared
with each other, e.g. in a calibration device. d) Depending on the
result of the comparison of step c), the wrist type blood pressure
monitor is recalibrated, if necessary.
Recalibration is preferably made automatically with the calibration
device. It is also conceivable to make a manual recalibration based
on values measured with the upper arm blood pressure monitor. In
this case, it will be sufficient to enter the correct setting values
into the wrist type blood pressure monitor before or after a measurement
with the wrist type blood pressure monitor. In this case, it is
not necessary to establish a physical connection between the upper
armblood pressure monitor and the wrist type blood pressure monitor.
The calibration device in this case is contained within the wrist
type blood pressure monitor.
In a preferred embodiment of the method, steps a) and b) are repeated,
e.g. three times. This enhances accuracy of the measurement and
therefore of the calibration.
In a further preferred embodiment, before carrying out step c),
it is verified if the blood pressure values measured in steps a)
and/or b) are within a predetermined range. The range can be .+-.20
mmHg for the systolic blood pressure and .+-.12 mmHg for the diastolic
blood pressure.
If the values are not within the predetermined range, steps a)
and/or b) may be repeated once more.
In a further preferred embodiment a pause may be made between steps
a) and b) and between repetitions of the measurements.
In a further preferred embodiment, the wrist type blood pressure
monitor and the upper arm blood pressure monitor are coupled to
each other with respective interface connectors before steps a)
and b) are carried out. With such a connection, manual entry of
data can be dispensed with.
In a further preferred embodiment, the power for the wrist type
blood pressure monitor during calibration is supplied by the calibration
device. It is necessary to edit the editable memory for calibration.
This process can be rather energy consuming. It is therefore preferred,
that during calibration, power is not supplied by batteries contained
within the wrist type blood pressure monitor but by an external
power supply.
The wrist type blood pressuring monitor according the invention
is used by the owner in a known manner. If the owner wants to make
sure, that his results correlate well with a reference site e.g.
the upper arm results, the blood pressure monitor may be recalibrated.
For this purpose, a doctor or the vendor of the blood pressure measuring
device is provided with a calibrating device. The blood pressure
on the upper arm can be measured under the control of a doctor or
in a pharmacy. The wrist type blood pressure monitor is thereafter
recalibrated. In most general terms, the present invention consists
in recalibrating an electronic blood pressure monitor on behalf
of blood pressure values determined in a reference measurement and
in providing a blood pressure monitor therefore.
The invention will be more clearly understood on behalf of the
following drawings which show:
FIG. 1 a schematic representation of recalibration of a wrist type
blood pressure monitor
FIG. 2 a schematic representation of a calibration device and a
wrist type blood pressure monitor and
FIG. 3 a flow chart for the recalibration.
FIG. 1 schematically shows a patient with a wrist type blood pressure
monitor 1. The blood pressure is measured based on pressure values
measured within a cuff 2 (see FIG. 2) which is placed around the
wrist W of the patient.
At about the same time, the blood pressure is also measured with
an upper arm blood pressuring monitor 11 with a cuff 12 placed around
the upper arm U of the patient.
The wrist type blood pressure monitor 1 is designed in a way known
to those skilled in the art and is operating according to the oscillometric
method. The blood pressure monitor 1 (see FIG. 2) comprises a cuff
2, a pressure sensor 3 for measuring the blood pressure P within
the cuff and calculating arrangement 4 for calculating the blood
pressure values, especially the systolic blood pressure S and the
diastolic blood pressure D.
The wrist type blood pressure monitor further comprises a memory
5 containing data necessary for calculating the blood pressure values
S, D. The memory 5 especially carries data for calibrating the measurement
results.
The wrist type blood pressure monitor 1 further comprises an interface
connector 6. Interface connector 6 allows connection between the
wrist type blood pressure monitor 1 and a calibrating device 20.
In FIG. 1 or 2, a wire connection is shown. Wireless communication
is also conceivable.
The calibrating device 20 comprises a calculating arrangement 14
for calculating the blood pressure values D', S' based on the pressure
P' measured within the cuff 12 placed around the upper arm U of
the patient. The calibration device 20 comprises an interface connector
16 which allows connection with the wrist type blood pressure monitor
1. The calibration device is further provided with a power supply
21 which can also be used to supply the wrist type blood pressure
monitor 1 with electricity during the calibration process.
The upper arm blood pressure monitor 11 is designed in a manner
known to those skilled in the art. It especially comprises a cuff
12 connected via a tube 15 to the calibration device 20.
Within the calibration device 20, a usual calculating arrangement
14 and pressure sensor 13 are arranged.
In FIG. 3, a flow chart for the calibration process is shown. In
a first step, the batteries are removed from the wrist type blood
pressure monitor 1. This is necessary for establishing a connection
with the interface connector 6 which is arranged within the battery
compartment 5.
The wrist type blood pressure monitor is then connected to the
calibration device 20.
Subsequently, the calibration device is switched on. The wrist
type blood pressure monitor 1 is thereafter controlled through the
calibration device 20.
The blood pressure is then measured with the calibration device
20 (i.e. based on the upper arm cuff 12) and with the wrist type
blood pressure monitor 1. These measurements are repeated for e.g.
three times. Each measurement lasts about for sixty seconds. A pause
of sixty seconds is made between to subsequent measurements.
Subsequently, it is determined if the results of the measurements
are within a predetermined range. The range is typically .+-.20
mmHg for the systolic and .+-.12 mmHg for the diastolic blood pressure.
If the readings are not within the predetermined range, the measurement
with the wrist type blood pressure monitor and/or with the calibration
device are repeated. Based on the four-measurements, it is determined
if at least three readings are within the predetermined range. If
this is still not the case, an error message is given.
If after three or four measurements, the readings are within the
predetermined range, the blood pressure values D, S given by the
wrist type blood pressure monitor 1 and the values D',S' given by
the calibration device 20 are compared to each other. Based on possible
differences between the values D and D' and S and S', the calibration
data in the memory 5 are amended according to a specific algorithm.
After writing the corrected calibration values into the memory
5, a message indicating successful calibration may be given and
both, the wrist type blood pressure monitor 1 and the calibration
device 20 are switched off.
The memory 5 is an EEPROM. The calibration device writes the new
defined constants into the EEPROM of the monitor.
There is a factory setting (factory calibration constants for the
"average patient") stored in the masked IC (single chip
microprocessor). After starting the program it first checks if there
is any calibration constant stored in the EEPROM. If there is no
value in the EEPROM, the program will use the factory setting of
the microprocessor. If there is a value (systolic and diastolic
calibration constants) in the EEPROM, the microprocessor will use
the new constants for the EEPROM for evaluation of the patient's
systolic and diastolic blood pressure values.
The wrist type blood pressure monitor 1 further may comprise means
for resetting the calibration to the factory values. It is also
conceivable to provide one and the same wrist type blood pressure
monitor 1 with several calibration sets which may be valid for several
users.
A wrist type blood pressure monitor 1 which is designed for use
by one single patient may further be provided with a label indicating
the name of the user. The label may also be electronic. |