Surgery – Diagnostic testing – Cardiovascular
Reexamination Certificate
2003-02-10
2004-10-19
Jones, Mary Beth (Department: 3736)
Surgery
Diagnostic testing
Cardiovascular
C600S493000, C600S494000, C600S500000
Reexamination Certificate
active
06805670
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electronic blood pressure monitor, and more particularly to an electronic blood pressure monitor using a pressurizing section (hereinafter referred to as a “cuff”) for pressurizing a portion in one of four limbs and others of a mammal by injecting a fluid such as air thereinto.
2. Description of the Background Art
Among methods measuring a blood pressure using a cuff, there has been available a method in which various kinds of arterial signals (hereinafter referred to as “pulse waves”) originated from changes in inner volume of an artery around which a pressure is applied with the cuff are captured in the course during which a pressure in the cuff (hereinafter referred to as a “cuff pressure”) is gradually changed to calculate and determine a blood pressure based on the captured pulse waves. This method is called an oscillometric method.
FIG. 14
is a diagram showing a construction of an electronic blood pressure monitor that is applied to an example in a prior art practice and embodiments of the present invention. The electronic blood pressure monitor of
FIG. 14
includes: a microprocessor
1
having, therein, a CPU (an abbreviation of a central processing unit)
1
A for intensively controlling and monitoring the electronic blood pressure monitor itself as a center and a memory
1
B; a cuff
2
, being placed at a predetermined portion of a mammal in order to pressurize an artery; a gradual pressure reduction section
3
, a rapid discharging section
4
, a pressurizing section
5
and a cuff pressure detecting section
6
all of which are connected to the cuff
2
by an air system; a pulse wave detecting section
7
detecting a pulse wave originating from a change in volume of the artery produced in the course during which the artery is pressurized with the cuff
2
; an amplifying circuit-AD (analog-digital) converters
8
and
9
; an input interface
10
and an output interface
11
. A pressure inside the cuff
2
is controlled by the gradual pressure reduction section
3
, the rapid discharging section
4
and the pressurizing section
5
.
The CPU
1
A of the microprocessor
1
controls other sections. The pressurizing section
5
has a pressure pump, by which the cuff
2
is pressurized to a predetermined cuff pressure. The gradual pressure reduction section
3
has a valve for reducing a cuff pressure. While the valve is closed during pressurization of the cuff
2
, it works so as to gradually reduce a cuff pressure when being opened. The rapid discharging section
4
has a valve for reducing a cuff pressure. While the valve is closed during pressurization of the cuff
2
, it works so as to rapidly reduce a cuff pressure when being opened. The cuff pressure detecting section
6
has a pressure sensor to detect a cuff pressure. The pulse wave detecting section
7
detects a pulse wave. The amplifying circuit-AD converters
8
and
9
amplify signals outputted from the cuff pressure detecting section
6
and the pulse wave detecting section
7
, respectively, to convert the signals to digital values and to give the digital values to the microprocessor
1
. The microprocessor
1
processes given data to calculate a blood pressure value and to output a result of the calculation through the output interface
11
. The input interface
10
is constituted of switches, buttons and others and installed so as to enable to be externally operable by a user. The output interface
11
is constituted of a display section for displaying information; a printer for printing the information; a speech output section for outputting the information in speech; and others.
A pulse wave is produced by a change in inner volume of an arterial blood vessel, around which an external pressure (a cuff pressure) is applied by pressurization of the cuff
2
, due to a balance between the cuff pressure and an pulsating inner pressure (blood pressure). In an oscillometric method, a blood pressure value (at least one of a systolic blood pressure, a diastolic blood pressure and an average blood pressure) is calculated from a pattern of changes in amplitude of pulse waves corresponding to chronological levels of a cuff pressure that changes in the course during which the cuff pressure increases or decreases gradually, for example, stepwise or continuously in a range between a value in the vicinity of a systolic blood pressure (a so-called maximum blood pressure) and a value in the vicinity of a diastolic blood pressure (a so-called minimum blood pressure).
In this method, though a necessity arises for raising a pressure inside the cuff
2
to a value equal to or higher than a systolic blood pressure at the first stage, the systolic blood pressure largely alters according to an individual difference or various factors of the same individual as well, so pressurization has been started after adjusting a pressurization amount given by the pressurizing section
5
in the cuff
5
with an change-over switch provided to the input interface
10
. Contradiction arises, however, in adjustment of the pressurization amount performed based on in-advance estimation of a user in an electronic blood pressure monitor with which the user measures a blood pressure since the user uses the electronic blood pressure monitor to measure a blood pressure unknown to the user and such operation has actually been tough to the user.
Therefore, a method has been contrived in which a pulse wave is detected during pressurization of the pressurizing section
5
in the cuff
2
to estimate a systolic blood pressure with a certain precision and to cease pressurization in the cuff
2
at an optimal level based on the estimation. This method is called an automatic pressure setting function and disclosed in JP patents No. 2842696, No. 2936814, No. 2936816, No. 3008582, No. 3042051 and No. 3042052. With the method adopted, a necessity has been removed for a manual operation of a user to adjust a pressurization value through estimation of a systolic blood pressure.
In an oscillometric method, however, since there is still a necessity for gradually reducing a cuff pressure down to a comparative low pressure equal to or lower than a diastolic blood pressure from a high pressure higher than a systolic blood pressure, not only has a user been placed under a restraint in a blood pressure measurement for a long time, which is troublesome to the user, but a problem has also arisen that an environment of usage is restricted and a rapid change in blood pressure cannot be captured though a precision of measurement has become high due to acquirement of information for measuring a blood pressure over a long time, that is to say, due to acquirement of much biogenic information. That is to say, a time is consumed in measurement in the oscillometric method for the reason that a cuff pressure cannot be reduced at a high speed in order to maintain a precision.
In contrast thereto, another method has been proposed in which a measuring time can be shortened even though the measuring method still uses the cuff
2
. For simplicity of description of the method, the method is herein called an SPD method (Single Pulse Determination). The SPD method is disclosed in JP patent No. 2745467, No. 2855767 and others. According to an SPD method, a cuff pressure is raised to an arbitrary value to maintain there and a pulse wave signal is captured by one wave or several waves, thereby enabling estimation of a blood pressure value. A construction of an electronic blood pressure monitor to which an SPD method is applied is almost similar to that shown in
FIG. 14
only with the exception that no necessity arises for the gradual pressure reduction section
3
.
An SPD method uses a change in a waveform of a pulse wave depending on a value of a cuff pressure relative to a blood pressure (hereinafter referred to as a “relative cuff pressure”). To briefly describe a principle thereof, a cuff pressure is at first raised to an arbitrary value to then capture at least one pulse wave and to obtain a wavef
Jones Mary Beth
Morrison & Foerster / LLP
Natnithithadha Navin
Omron Corporation
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