JP2745466B2 - Electronic sphygmomanometer - Google Patents

Description

The present invention relates to an electronic sphygmomanometer capable of detecting insufficient pressurization.

(B) Conventional technology In a blood pressure measurement method called the Liberlotch method, for example, an arm band (cuff) is attached to an upper arm, and air in the cuff is pressurized to a set value (pressurized the cuff), and a day is performed. After the ischemia of the brachial artery, the air in the cuff is evacuated at a constant minute speed, and systolic pressure and diastolic pressure are determined based on cardiovascular information generated in the process, which is safer than the direct method, It has a simple measurement procedure and is used in many automated electronic sphygmomanometers at medical sites and homes.

Electronic sphygmomanometers that employ the Leverotti method include an oscillometric type using a pulse wave as cardiovascular information and a Korotkoff type using a Korotkoff sound as cardiovascular information. The oscillometric electronic sphygmomanometer detects a pulse wave in the process of evacuating the cuff at a very low speed, and for example, detects a change in the amplitude value of the pulse wave and detects a systolic pressure and a diastolic pressure (hereinafter collectively referred to as a blood pressure value). Is determined). On the other hand, a Korotkoff-type electronic sphygmomanometer detects a Korotkoff sound generated from a blood vessel using a microphone in the process of evacuation at a very low speed, and determines a blood pressure value.

(C) Problems to be Solved by the Invention Both types of electronic sphygmomanometers need to perform measurement after increasing the air pressure (cuff pressure) in the cuff to the systolic pressure or more. If the set value is lower than the systolic pressure, the blood pressure value cannot be determined in principle.

In the above-mentioned oscillometric electronic sphygmomanometer, insufficient pressurization is not known until the measurement is in its infancy. For this reason, even if the pressurization is insufficient, the measurement is continued as it is, and after a certain period of time, it is determined that the pressurization is insufficient, and the measurement may have to be performed again.

On the other hand, in the Korotkoff-type electronic sphygmomanometer, underpressurization can be determined from the presence or absence of the Korotkoff sound at the start of measurement. However, it is not possible to determine how much under-pressurization is performed, and even if the pressurization value is increased by a certain amount and re-pressurization is performed, the pressurization is still insufficient or excessive pressurization is necessary. There is. In addition, since a highly sensitive microphone is used, unnecessary re-pressurization may be performed by erroneously recognizing surrounding noise as Korotkoff sound.

As described above, in the electronic blood pressure monitor that employs the conventional Leveroch method, the subject must carefully set a value in order to avoid insufficient pressurization, which is troublesome. There is a risk that the test subject may suffer pain or stasis due to erroneous detection of insufficient pressurization. Further, there is another problem that the measurement efficiency is reduced by the re-measurement.

The present invention has been made in view of the above, and an object of the present invention is to provide an electronic sphygmomanometer that can determine not only insufficient pressurization but also how much underpressurization.

(D) Means for Solving the Problems In order to solve the above problems, the electronic sphygmomanometer of the present invention comprises:
In an electronic sphygmomanometer that measures a blood pressure by pressurizing a cuff attached to a subject to a set pressure, a pulse wave detecting unit that detects a pulse wave from the subject and outputs a pulse wave signal, and calculates a waveform of the pulse wave signal. Membership function storage means for storing a membership function obtained from statistical data relating to the pulse wave parameter to be represented, and one or a number from the pulse wave detection means immediately after the cuff is pressurized to the set pressure. Pulse wave parameter calculating means for calculating pulse wave parameters from the waveforms of the individual pulse wave signals, and insufficient pressurization based on the pulse wave parameters calculated by the pulse wave parameter calculating means and the data stored in the membership function storage means. And under-pressurization detecting means for detecting the pressure.

In the electronic sphygmomanometer of the present invention, a cuff is attached to the subject,
As the pressure in the cuff is increased, the pulse wave detecting means detects a pulse wave and outputs a pulse wave signal in synchronization with the pulse of the subject. The membership function storage means stores a membership function obtained from statistical data on pulse wave parameters representing the waveform of the steam pulse wave signal. When the pressure in the cuff increases to the set value, the pulse wave parameter calculating means calculates the pulse wave parameter from the waveform of one or several pulse wave signals outputted from the pulse wave detecting means immediately thereafter. If the pressure is insufficient even if the pressure is increased to the set value, the insufficient pressure detection means should be insufficient under pressure based on the pulse wave parameter just obtained and the data stored in the membership function storage means. Is detected.

(F) Examples Hereinafter, the present invention will be described in more detail with reference to examples.

First, the principle of measurement used by an electronic blood pressure monitor according to an embodiment of the present invention will be described with reference to FIGS. 1, 2, and 7. FIG. It is known that the waveform of the pulse wave changes with the cuff pressure, and it can be expected from the waveform of the pulse wave how much the current cuff pressure is different from the systolic pressure, that is, the relative pressure can be estimated.

In order to evaluate the waveform of the pulse wave, for example, parameters such as the pulse wave amplitude AMP, the pulse wave integration level RAV, the waveform width ratio WID, and the refractive index CON may be calculated and used as shown in FIG. now,
Considering pulse wave amplitude AMP, FIG. 7 (a) shows pulse wave amplitude AMP and relative cuff pressure P obtained for a large number of subjects.
_This is a dot plot of the relationship of _C ′. This seventh
FIG. 7A shows a probability density distribution in which the pulse wave amplitude AMP and the relative cuff pressure P _C ′ are varied, and a membership function can be generated using the probability density distribution.

If the pulse wave amplitude AMP is actually measured, when the membership function shown in FIG. 7A is cut at this pulse wave amplitude AMP ^* , the cut end becomes as shown in FIG. 1A. Wave amplitude AM
It can be a membership function of the relative cuff pressure P _C ′ with respect to P ^* . Such a membership function is similarly obtained for other parameters [(b) in FIG.
(See (c) and (d)). A function obtained by performing a predetermined logical calculation such as multiplication or addition on the membership function for each parameter obtained in this manner is as shown in FIG. 1 (e), for example. It can be assumed that the relative cuff pressure corresponding to the value is most likely. If the relative cuff pressure can be estimated, it is possible to know how far the current cuff pressure is from the systolic pressure, and it is possible to determine the presence or absence of each pressure shortage and its degree.

FIG. 3 is a block diagram for explaining the configuration of the electronic blood pressure monitor of this embodiment. Reference numeral 2 denotes a cuff to be attached to the upper arm of the subject. The cuff 2 is connected to an exhaust valve 3, a pressurizing pump (pressurizing means) 4, and a pressure sensor (pressure detecting means) 5. The exhaust valve 3 and the pressure pump 4 are controlled by the MPU 10. After an output signal of the pressure sensor 4 (hereinafter, referred to as a cuff pressure signal) is amplified by an amplifier 6, one of the output signals is directly input to an analog / digital (A / D) converter 8, digitally converted, and taken into the MPU 10. On the other hand, the cuff pressure signal is
The pulse wave signal is input to the band pass filter 7 and detected. This pulse wave signal is also digitally converted by the A / D converter 8 and
It is taken into PU10.

The MPU 10 has a function of calculating parameters of the pulse waveform, a function of selecting a membership function based on the calculated parameters, a function of performing a logical operation on the selected membership function to determine insufficient pressurization, And the like to determine the blood pressure value from the fluctuation of the pulse wave amplitude at the time.

In the memory 10a in the MPU 10, a data table of the membership function and an operation program are stored. The display unit 9 is connected to the MPU 10, and the determined blood pressure value and the like are displayed.

Next, the overall operation of the electronic blood pressure monitor of the embodiment will be described below with reference to FIG.

First, the cuff 2 is wrapped around the upper arm of the subject to start blood pressure measurement. First, the MPU 10 closes the exhaust valve 3, turns on the pressurizing pump 4, and starts pressurizing [step (hereinafter referred to as ST) 1]. The MPU 10 fetches the cuff pressure signal from the A / D converter 8 (ST2), and the current cuff pressure becomes the set pressure P
_It is determined whether or not _co has been reached (ST3). If the determination is NO, the process branches to ST2, and if the determination is YES, the process branches to ST4. That is, until the current cuff pressure reaches the set pressure P _co, processing ST2, ST3 are repeated. The set pressure _Pco may be fixed, or a setting switch may be provided so that the subject can select the set pressure. The design can be changed as appropriate.

In ST4, the MPU 10 stops the pressurizing pump 4. Then, the MPU 10 captures the pulse wave Pw (t), and this pulse wave Pw (t)
Separate the pulse wave by applying the threshold TH ₀ to [in FIG. 2 (b) refer to Fig. Then, the MPU 10 determines whether or not the break points T _st and T _en have been detected from the pulse wave Pw (t) (ST7). If the determination is NO, the process branches to ST5, and if the determination is YES, the process proceeds to ST8. Branch to That is, the processing of ST5 to ST7 is repeated until one pulse wave is obtained.

In ST8, the MPU 10 calculates the following four parameters from the pulse wave Pw (t). In this embodiment, one pulse wave is detected and parameters are calculated. However, if several pulse waves are detected, parameters are calculated for each pulse, and an average of these parameters is obtained, higher reliability is obtained. Is obtained.

In addition ST9, MPU 10 estimates the recompression pressure setpoint P _c1 from the parameters obtained in ST8. In ST10, the re-pressurization set value P _c1 is compared with the initial set value P _C0 ,
If _c1 is greater than the set value P _c0 branch to (P _c1> P _c0) ST11 determines that the pressure shortage, if P _c1 is P _c0 less (P _c1 ≦
_Pc0 ), it is determined that the pressure is not insufficient, and the process branches to ST13.

In ST11, the MPU 10 causes the display 9 to indicate that pressurization is insufficient. In addition to or instead of this display, a configuration may be used in which the subject is notified of insufficient pressurization by voice.

In ST12, MPU 10 activates the respective pressure pump 4 again, to re-pressurized to recompression pressure setpoint P _c1. In ST13, MPU10
The blood pressure value is determined by an oscillometric method. In this blood pressure value determination process, the exhaust valve 3 is set to the slow exhaust state, and the pulse wave amplitude in the slow exhaust process is captured. The pulse wave amplitude increases as the cuff pressure decreases, reaches a maximum near the average value of the systolic pressure and the diastolic pressure, and then decreases again. The cuff pressure when the pulse wave amplitude becomes about 50% of the maximum amplitude on the increasing side corresponds to the systolic pressure, and the cuff pressure when the pulse wave amplitude becomes about 70% of the maximum amplitude on the decreasing side corresponds to the diastolic pressure Therefore, for example, the blood pressure value can be determined based on this. Note that the present invention does not include the blood pressure value determination process itself as a main part, and thus a detailed description is omitted. Also,
The blood pressure value determination processing may be performed by the Korotkoff method, and the design can be appropriately changed.

In ST14, the MPU 10 puts the exhaust valve 3 into the rapid exhaust state, rapidly exhausts the cuff 2 and releases the subject's upper arm from compression. Further, the MPU 10 displays the determined blood pressure value on the display 9 (ST15).

Next, the pulse wave parameter calculation process (ST8) will be described below with reference to FIGS. 2 and 5.

In this example electronic blood pressure monitor, as a pulse wave parameter,
Pulse wave amplitude AMP, integration level RAV, waveform width ratio WID, flexion rate CON
Are adopted. Of course, the pulse wave parameters are not limited to these four.

First, the MPU 10 determines the time T at which the pulse wave Pw (t) becomes maximum and minimum.
_max, searching T _min, T _max, T _min to the corresponding pulse wave maximum value Pw _max, stores the pulse wave minimum value Pw _min in the memory 10a [ST 101, in FIG. 2 (a) see FIGS. And from Pw _max
The pulse wave amplitude AMP is calculated by subtracting Pw _min (ST102).

Next, an integral level RAV [%], which is a value obtained by normalizing the time average of the pulse wave Pw (t) with the amplitude AMP, is calculated by the following equation (1) [ST103, see FIG. 2 (b)]. .

Subsequently, the waveform width ratio WID [%] is calculated (ST1).
04 to ST108, see FIG. 2 (c)), and the WID is the pulse wave Pw.
The time from the maximum value Pw _max emergence of (t) to decrease to a predetermined threshold value TH _1, a normalized value in a cycle of the pulse wave (T _en -T _st).

First, to set the threshold TH ₁ by the following equation (2),
X in the equation (2) is a constant that is predetermined in the range of 0 to 1 (ST104).

TH ₁ = Pw _min + AMP × x (2) Next, the time t is set to T _max (ST105), and the sampling width Δt is added to this t (ST106), and the pulse wave Pw for this t is added.
(T) determines whether it is TH ₁ below (ST 107).
When the determination in ST107 is NO, the process branches to ST106, and when the determination is YES, the process branches to ST108. In ST108, the following equation (5) is used.
Calculate WID.

Here, T _dec is the time a Pw (t) ≦ TH _1.

Finally, calculate the bending ratio CON [%] (ST109 to ST11).
1). This CON is a reference connecting the maximum point and the minimum point of the pulse wave at a point T _cen which internally _divides the time section [T _max , T _min ] between the maximum point and the minimum point in one beat at a predetermined ratio y. Straight line L and pulse wave
This is a relative ratio to Pw (t).

First, T _cen is obtained by the following equation (4) (ST109).
Here, y is a constant preset in the range of 0 to 1.

T _cen = T _max + (T _en −T _max ) × y (4) Next, the level Ref of the reference straight line L at T _cen is calculated by the following equation (5) (ST110).

Ref = Pw _max −AMP × y (5) Then, CON is calculated by the following equation (6).

Next, the re-pressurization set value estimation process will be described with reference to FIGS. 1, 6, and 7. FIG.

First, in ST201 to ST204, the parameter AMP obtained in ST8,
Classification (ranking) processing is performed for each of RAV, WID, and CON. Since the data table of the membership function described later is discrete, a classifying process is required to correspond to this. Specifically, the following (7) to (10)
This is done by the formula

R _amp = AMP / I _amp …… (7) R _rav = (RAV−O _rav ) / I _rav …… (8) R _wid = (WID−O _wid ) / I _wid …… (9) R _con = CON / I _con ... (10) where I _amp , I _rav , I _wid , and I _con are rank widths, respectively. Also, O _rav, O _wid is offset value. RAV
Since the minimum values of WID and WID are not zero, the offset values O _rav and O _wid are subtracted from these values, and then divided by the rank widths I _rav and I _wid .

In ST205 and thereafter, the re-pressurization set value is estimated using the parameters R _amp , R _rav , R _wid , and R _con ranked in this manner. Before describing the specific processing, a data table will be described.

FIGS. 7 (a), (b), (c), and (d) show the measured data of AMP, RAV, WID, and CON obtained for a large number of subjects by plotting the relative pressure P _c ′ on the horizontal axis. is there.
What is shown in each figure is a so-called probability density distribution using parameters and relative pressure as variables, and these are adopted as membership functions. In FIG. 7, if the pulse wave parameters are AMP ^* , RAV ^* , WID ^* , and CON ^* , and if the respective membership functions are cut off at AMP ^* , RAV ^* , WID ^* , and CON ^* , The cuts are as shown in FIGS. 1 (a), (b), (c) and (d). FIGS. 7 (a), (b), (c) and (d) show AMP ^* and RAV, respectively.
^* , WID ^* , CON ^* can be seen as the selected membership function.

In the electronic blood pressure monitor of this embodiment, the parameters and the relative cuff pressure P _c ′ are ranked, and the membership function is discretized and stored in the memory 10a in the form of a data table. For example, the membership function for AMP can be expressed by the following matrix, assuming that P _c ′ and AMP are ranked m and n, respectively.

If AMP is calculated and its ranked value is R
_{In the case of amp} , a vertical column corresponding to R _amp is selected from the above matrix as a membership function corresponding to the value of AMP.

Returning to the description of the processing of ST205, in ST205, the initial value of the pointer j of the relative cuff pressure _Pc 'and the variable _Pmax storing the maximum value of the multiplied membership function are set to 0. ST
At 206, the above j is incremented by one, and at ST207, the membership function is multiplied by the following equation (11).

P = P _amp (j, R _amp ) × P _rav (j, R _rav ) × P _wid (j, R _wid ) × P _con (j, R _con ) …… (11) In ST208, it was calculated in ST207. It is determined whether P is _{equal to} or greater than _Pmax . If this determination is YES, the process branches to ST210, where NO
In the case of, the process branches to ST209. In ST209, j, P at this time
In m _max and P _max respectively. In ST210, it is determined whether or not j is equal to or less than m. If the determination is NO, the process branches to ST206; if the determination is YES, the process branches to ST211.

The processing of ST206 to ST210 is repeated until the determination of ST210 becomes YES, and this is performed by using the parameters AMP, R as shown in FIG.
This corresponds to a process of calculating a function P obtained by multiplying the membership functions for AV, WID, and CON, and extracting the maximum value _Pmax .

In ST211, the following (1) was obtained from the obtained M _max and P _max.
Estimate the relative cuff pressure P _c ′ _* according to equation (2).

'In _{* = P cmin + (M max} -1) × R pc ...... (12) wherein, R _pc is the relative cuff pressure P _c' P _c is a rank width.

In ST212, the estimated relative cuff pressure P _c 'is subtracted from the initial set value P _c0 to estimate the re-pressurization set value P _c1 . When the relative cuff pressure P _c ′ is positive, the set value P _c0 is equal to or more than the systolic pressure, the re-pressurization set value P _c1 is equal to or less than P _c0, and the determination in ST10 is NO. Conversely, when the relative cuff pressure P _c ′ is negative, the set value P _c0 is less than the systolic pressure, the re-pressurization set value P _c1 becomes larger than P _c0, and the determination in ST10 becomes YES.

In the above embodiment, the re-pressurization is automatically performed. However, the re-pressurization set value or the re-pressurization amount (difference between the re-pressurization set value and the initial set value) is set together with the insufficient pressurization. The display may be displayed and the subject may repressurize in accordance with the display, and the design may be changed as appropriate.

(G) Effects of the Invention As described above, the electronic sphygmomanometer of the present invention detects a pulse wave from a subject and outputs a pulse wave signal, and a pulse wave parameter representing a waveform of the pulse wave signal. A membership function storing means for storing a membership function obtained from statistical data relating to one or more pulse wave signals from the pulse wave detecting means immediately after the cuff is pressurized to a set pressure. Pulse wave parameter calculating means for calculating a pulse wave parameter from a waveform; and insufficient pressurization for detecting insufficient pressurization based on the pulse wave parameter calculated by the pulse wave parameter calculating means and data stored in the membership function storage means. And a detecting means.

Therefore, it is not only possible to accurately determine insufficient pressurization after the end of each initial pressure, it is also possible to know the degree of the lack,
Re-pressurization can be completed only once. Therefore, it is less necessary to be careful in determining the initial set value, and it is possible to prevent the subject from setting an unnecessarily high set value. In addition, since insufficient pressurization is detected using the pulse wave, erroneous detection of insufficient pressurization due to ambient noise can be prevented, and the risk of causing pain or congestion in the subject is reduced.
Further, the need for re-measurement is reduced, and the measurement efficiency is improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a membership function for explaining a re-pressurization set value estimating process of an electronic sphygmomanometer according to one embodiment of the present invention, and FIG. 2 is a pulse wave parameter calculation of the electronic sphygmomanometer. FIG. 3 is a block diagram illustrating the configuration of the electronic sphygmomanometer, FIG. 4 is a flowchart illustrating the overall operation of the electronic sphygmomanometer, and FIG. FIG. 6 is a flowchart illustrating a pulse wave parameter calculating process of the electronic sphygmomanometer, and FIG. 6 is a flowchart illustrating a re-pressurization set value estimating process of the electronic sphygmomanometer; FIGS. 7 (a) and 7 (b) , FIG. 7 (c) and FIG. 7 (d) are diagrams showing actually measured data for explaining the relationship between the pulse wave amplitude, the integration level, the waveform width ratio, and the flexion rate with the relative cuff pressure, respectively. . 2: Cuff, 3: Exhaust valve, 4: Pressure pump, 5: Pressure sensor, 7: Band pass filter, 10: MPU, 10a: Memory, P _c : Cuff pressure, P _c ′: Relative cuff pressure, Pw ( t): pulse wave, AMP: pulse wave amplitude value, RAV: integration level, WID: waveform width ratio, CON: flexion rate.

Claims (1)

(57) [Claims] 1. An electronic sphygmomanometer that measures a blood pressure by pressurizing a cuff attached to a subject to a set pressure, wherein the pulse wave detecting means detects a pulse wave from the subject and outputs a pulse wave signal; Membership function storage means for storing a membership function obtained from statistical data on pulse wave parameters representing the waveform of the wave signal, and from the pulse wave detection means immediately after the cuff is pressurized to the set pressure. Pulse wave parameter calculating means for calculating a pulse wave parameter from the waveform of one or several pulse wave signals; and a pulse wave parameter calculated by the pulse wave parameter calculating means and data stored in the membership function storing means. An electronic sphygmomanometer provided with under-pressurization detecting means for detecting under-pressurization based on the pressure.