JPS59131329A - Digital type automatic blood pressure measuring apparatus - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a digital automatic blood pressure measuring device. In particular, when measuring blood pressure, a pulse wave signal representing a pulse wave generated by compressing a part of the human body is
The present invention relates to a device that converts the digital signal into a pretal signal using a D converter and measures blood pressure of the human body with high accuracy over a wide range of measurement targets based on the digital signal.

As the pressure is decreased, it can be seen that a vibrational component appears in the pressure. This vibration component is the pulsation of the arteries caused by the contraction of the heart, which appears as vibrations in the pressure, and is generally called a pulse wave.

By the way, various types of blood pressure measuring devices have been proposed in the past, but among them, the current one has the advantages of being able to measure blood pressure even when the patient is in a low blood pressure state, being resistant to external noise, and being easy to handle. The so-called oscillometric method (OS-CILLO8i, E to RICAiETH), which measures blood pressure based on changes in the size of the pulse wave,
OD) is said to be advantageous. In particular, in recent years, with the development of electronic technology such as computers, pulse waves in pressure can be extracted as electrical pulse wave signals (Figure 1 (b)) and digitally processed, thereby increasing blood pressure. The above-mentioned so-called digital automatic blood pressure measuring device has been developed, and blood pressure measuring devices based on the oscillometric method have come to be widely used.

In a digital automatic blood pressure measuring device, it is natural that the pulse wave signal, which is an analog signal, needs to be converted into a digital signal using a high-precision A/D converter.
Since A/D converters are generally expensive and large, when designing them, a single A/D converter is used to convert the pulse wave signal to maintain high blood pressure measurement accuracy for a wide range of measurement targets. It is desirable to do so.

However, if the measurement target (person being measured) is different, widening the measurement target and maintaining high blood pressure measurement accuracy are contradictory issues, and blood pressure is not necessarily sufficient for a wide range of measurement targets. There was a drawback that measurement accuracy could not be obtained.

That is, 1. An A/D converter converts the input signal within a certain input range into a digital signal using the maximum number of pits. However, since the magnitude of the pulse wave signal changes by several tens of times or more due to different measurement targets, the maximum value of the pulse wave signal is If you try to maintain the measurement target range by setting the input range of the D converter so as not to saturate it, if the pulse wave signal is small, it will be converted into a digital signal with low resolution, reducing blood pressure measurement accuracy. .

The present invention has been made in view of the above-mentioned circumstances, and its purpose is to measure blood pressure reliably and with high precision regardless of the magnitude of the pulse wave signal obtained from the subject. The objective is to provide a digital automatic blood pressure measuring device that can measure blood pressure.

In order to achieve the object, the present invention provides (1) a digital automatic blood pressure measuring device as described above, which detects the magnitude of a pulse wave signal and generates a pulse wave level signal representing the magnitude; (2) pulse wave level detection means for outputting the pulse wave level;
an amplifier circuit having selectable multiple stages of amplification factors, amplifying the pulse wave signal and supplying the pulse wave signal to the A/D converter;
3) A selection circuit that selects the amplification factor of the layer end circuit, and selects the amplification factor of the amplification circuit based on the above-mentioned law wave signal and the amplification factor of the amplified pulse supplied to the A/D converter. A control means is provided for controlling the magnitude of the inverse signal so that it is at least a certain magnitude predetermined for the input range of the A/D converter, and does not exceed the input range.

In this way, the pulse wave signal, regardless of its magnitude, is input with a magnitude greater than a predetermined magnitude and smaller than the input range of the A/D converter. Since the resolution is not affected by the magnitude of the pulse wave signal, highly accurate blood pressure values can always be obtained even when measuring a wide range of subjects. became possible. Moreover, since such control is automatically performed based on the pulse wave level signal detected by the pulse wave level detection means, the blood pressure measuring device does not have to be handled complicatedly.

Furthermore, in the present invention, in order to maintain high resolution of the pulse wave signal, a plurality of expensive A/D converters with different input ranges are selected according to the magnitude of the pulse wave signal. Instead, the amplification factor of an inexpensive amplifier circuit is selected by switching, so the device does not become large-sized and is extremely economically advantageous.

Hereinafter, two or three embodiments of the present invention will be described in detail based on the drawings. It goes without saying that in the following embodiments, for the sake of simplicity, the embodiments can also be applied to a case where blood pressure is measured while compressing a part of the human body.

In Fig. 2, 2 is a bag-shaped cuff attached to a part of the subject to compress that part, and the cuff 2 detects the pressure inside the cuff (Fig. 1 fa)). A pressure sensor 4 is connected thereto which outputs a pressure signal SP representing the pressure. The pressure signal SP is amplified to a predetermined magnitude by a preamplifier 6 and then supplied to a low-pass filter 8 and a band-pass filter 10-. The low-pass filter 8 removes the pulse wave signal component, which is a vibration component, from the pressure signal SP, and outputs a pressure value signal PV representing a static pressure value that does not include the pulse wave signal component. 1st A
The signal is supplied to the I10 port 14 via the /D converter 12. On the other hand, the bandpass filter IO extracts a pulse wave signal SM (FIG. 1(b)) representing a pulse wave of about 0.5 to 200 Hz from the pressure signal SP, and sends it to the amplifier circuit 16 and the pulse wave level. The signal is supplied to the detection circuit 18.

The amplifier circuits 16 have mutually different amplification factors A1. A2, A
s and A4. Second. 3rd and 4th amplifier 2
2, 24, 26, and 28 are provided in parallel, and the pulse wave signal SM is amplified by these amplifiers 22 to 28, and the pulse wave signals SM are amplified by the first, second, . 3rd and 4th
Pulse wave signal SMI, 8M2°8M3 and 8. M4 is designed to be output in parallel. Note that in this embodiment, the first. Second. Third and fourth amplifiers 22, 24, 26 and 2
In order of 8, the amplification factors A, , A, , A3 and A,
is set so that it becomes twice as large.
Second. The levels of the third and fourth pulse wave signals SMI, SM2, 8M3, and 8M4 increase by two times in this order. These first to fourth pulse wave signals SM1 to S
M4 is sent to the level control circuit 30 as a control means, and is input to the multiplexer 32 as a selection circuit.
I, P2. Supplied to Pa and P4, respectively.

On the other hand, the pulse wave level detection circuit 18 includes a reference amplifier 34
and the first of the three. It consists of second and third comparators 36, 38, and 40, and a saturation detection circuit 41, which will be described later.
The pulse wave signal S Bi is first amplified by a reference amplifier 34 and then supplied to each of the comparators 36 to 40. The reference amplifier 34 has a predetermined reference amplification factor A.
Amplify the pulse wave signal S'M with R to obtain the reference pulse wave signal SΔIR
and outputs this to the first to third comparators 36 to 4.
Supply to 0. First to third comparators 36 to 40
compares the input reference pulse wave signal SMR with preset comparison voltages ■l, ■2, and ■3, respectively, and compares the comparison results with the first. Second and third pulse wave level signals SLI, S
L2 and SL8 are output, and these are sent to the selection control circuit 42 of the level control circuit 30. Note that the comparison voltages V, , V2, and (3) are set so that their voltage values increase by twice in this order. These voltage values and the reference amplification factor AR are determined in relation to the amplification factors A1 to A4 of the first to fourth amplifiers 22 to 28, and the relationship between them will be described later.

The control circuit 42 includes a shift register for inputting the customer pulse signal SLI to SL3 from the pulse wave level detection circuit 18 in parallel and holding their contents, and a shift register for holding the contents and outputting them in parallel. It consists of a ROM that converts the contents into a code for controlling the multiplexer 30, and a hold signal S supplied from the I10 port 14.
The contents of the pulse wave level signals SLI to SL3 are held based on the pulse wave level signals SLI to SL3, and a port select signal SPS code-converted according to the held contents is supplied to the port select terminal PS of the multiplexer 30. multiplexer 30
is a well-known circuit, and the port select terminal PS
One of the first to fourth pulse wave signals SMI to SM4 supplied to the input ports PI to P4 is selected according to the content of the port selection signal SPS supplied to the port select signal SPS. 2nd A/D comparator as pulse wave signal SSM
46. In this embodiment, the hold signal SH is, for example, the second waveform from the beginning of the pulse wave signal SM that borders after the pressure of the cuff 2 is increased to a predetermined pressure (hereinafter, this waveform is used for level detection). waveform).

Therefore, in this embodiment, the level of the second level detection waveform of the pulse wave signal S R1 is
The results of the comparison are substantially the pulse wave level signals SLI to SL3, and the first to fourth pulse wave signals 5) 11 to 5) are determined depending on the contents of the pulse wave level signals SLI to SL3. One of the 8M4 is the selected pulse wave signal 5s
It is supplied to the second A/D converter 46 as x1.

Here, the input range of the second A/D converter 46 and the amplification factors A to A4 . By setting the amplification factor AR of the reference amplifier 34 and the comparison voltages vl to 3 of the comparators 36 to 40 in a predetermined relationship, the level of the maximum waveform of the selected pulse wave signal SSM is is the 2nd A/
With respect to the input range of the D converter 46, the input range is set to be greater than a predetermined value and not exceed the input range, so that regardless of the magnitude of the pulse wave signal SM, its resolution is is maintained high.

As shown in Fig. 1(b), the pulse wave signal white M has a maximum waveform level in the middle of the cycle during blood pressure measurement, but this maximum level value is at the beginning of the measurement cycle. It can be predicted from the level value of the waveform, and it has been confirmed that the maximum level value is generally about 10 times the initial level value. That is, the initial stage (in this example, the second stage after boosting)
By detecting the level value of the waveform of the pulse wave signal S
The maximum level value of M, the so-called magnitude of the pulse wave signal, can be estimated in advance (in this sense, it can be said that the pulse wave level signals SL1 to 8L3 represent the maximum magnitude of the pulse wave signal SM). ), in this embodiment, the pulse wave signal SM is amplified by the reference amplification factor AR to obtain the reference pulse wave signal SMB.
After that, the level of the level detection waveform is compared with the voltage ■1
Comparing voltages from v3 to v3, if the level is even lower than the lowest voltage comparison voltage ■1, the fourth voltage with the highest amplification factor
The fourth pulse wave signal S M 4, which is the output signal of the amplifier 28, is supplied to the second A/D converter 46 as the selected pulse wave signal SSM, and similarly, the above-mentioned level is
Comparison voltage V is larger, and 3rd p is smaller than 2.
The A-wave signal S M3 is much larger than the comparison voltage V2.
When the voltage is very small, the second pulse wave signal 5) (2) is larger than the comparison voltage v3, and when the first pulse wave signal SM1 is
Each pulse wave signal SSM is supplied to the second A/D converter 46 as a selected pulse wave signal SSM.

As mentioned above, the relationship between each comparison voltage [■] to 73 and the relationship between each amplification factor Al to A4 are 2, respectively.
Selected pulse wave signal SSM
Since the maximum level (v) is always within a predetermined range, the amplification factors A1 to A1 to By setting A4 in advance, as described above, the level of the maximum waveform of the selected pulse wave signal SS M has a predetermined constant magnitude, for example, with respect to the input range of the second A/D converter 46. It is 50% or more and has a size that does not enclose the input ftl area.

The second A/D converter 46 converts the selected pulse wave signal SSM selected as described above into a digital signal and converts it into a digital signal.
0 port 14, and also to the saturation detection circuit 41 of the pulse wave level detection circuit 18. Saturation detection circuit 41
is provided for the purpose of assisting the original function of the pulse wave level detection circuit 18, and the selected pulse wave signal SSM selected as described above unexpectedly has a magnitude greater than a predetermined level. For example, in this embodiment, the selected pulse wave signal SSM is within the input range of the second A/D converter 46.
When it exceeds 0%, a saturation signal SS is supplied to the 10 port 14 and the selection control circuit 42. When the selection control circuit 42 is supplied with the saturation signal SS, the contents of the shift register are serially shifted in one direction, and the contents of the port select signal 13P8 are changed by such shifting. As a result, the multiplexer 3-2 selects the output of the amplifier having an amplification factor one step lower than the current one. (1) The saturation statement SS supplied to the 10 port 14 notifies the later-described CPU (processing unit) 48 of a change in the substantial level of the selected pulse wave signal SSM due to the switching of the amplifier, and is already stored in the memory. It plays the role of performing calculations to make the data of the selected pulse wave signal 88Ri correspond to a new amplification factor. Note that calculation 1 is as follows.

In this embodiment, the already stored data is simply 1/
You can set it to 2.

If the saturation detection circuit 41 as described in 1 is provided, it is possible to continue measurement of peeping blood pressure even when the pulse wave signal SM becomes larger than expected due to individual differences in the subject.
As in this embodiment, the timing of occurrence of pulse wave signal 88M
If the selected pulse wave signal SSM is set when it exceeds a predetermined ratio of the input range of the second A/D converter 46, and the selected pulse wave signal SSM is not actually larger than the above input range, the necessary pulse wave signal SSM for blood pressure measurement can be determined. This method has the advantage of being able to obtain accurate blood pressure measurements, since there is a risk of missing data.

A start push button 50 for commanding the start of measurement is connected to the I10 port 14 to which the pressure value signal PV and the selected pulse wave signal 88M are supplied.
When is pressed, tart ST is supplied to I/, 0 port 14. ■10 Po) 1
4 is the CPU 48 and RAM 52 via the data path line.
and ROM 54, and supplies a pressure value signal P■, a selected pulse wave signal SSM, a start signal ST and a saturation signal 88 to the data bus line in accordance with commands from the CP 048. The CPU 48 executes signal processing using the temporary storage function of the 14M52 according to a program stored in the ROM 54 in advance, and outputs a hold signal SH, a pump drive signal AP, a rapid discharge signal EQ, and a slow discharge signal via the 10 port 14-. The control circuit 42 selects the discharge signal ES. Electric pump 56. While being supplied to the rapid discharge electromagnetic valve 58 and the slow discharge electromagnetic valve 60, the display signal SD, which is the signal processing result, is supplied to the display 62, so that the display 62 numerically displays the blood pressure measurement value.

Note that the electric pump 56. The rapid discharge solenoid valve 58 and the slow discharge solenoid valve 60 each receive a pump drive signal AP.
, the rapid evacuation signal EQ and the slow evacuation signal ES are supplied, so that air is pumped into the cuff 2 and air is discharged from the cuff 2. It has become.

The operation of this embodiment will be explained below.

When the power switch is suddenly turned on, power is supplied to each part of the device, and the CPO 48 performs control operations according to the flowchart of the main program shown in FIG. 3, which is stored in the ROM 54 in advance.

First, step Sl is executed, and the operating state of the start push button 50 is determined. While the start push button 50 is not operated, the execution of step S1 is repeated, but when the start push button 50 is suppressed to start blood pressure measurement, the next steps S2 and S3 are executed. That is, in step S2, the sending of both evacuation signals EQ and ES is blocked and both evacuation solenoid valves 58 and 60 are closed, and at the same time, the pump drive signal AP is supplied to the electric pump 56 and the pressure feeding of air into the cuff 2 is started. ), step S3
In this step, it is determined whether the actual pressure P within the cuff 2 represented by the pressure value signal PV is greater than the preset target upper limit pressure PM. While the actual output P is still smaller than the target upper limit pressure PM, steps S and S3 are repeated; however, if the actual pressure P exceeds the target upper limit pressure PM, steps S4 and S5 are immediately performed. is executed. That is, in step S4, the output of the pump drive signal AP is canceled and the electric pump 56 is stopped, and in step S5, the output of the slow discharge signal ES is
is supplied to the slow discharge solenoid valve 60 to open the solenoid valve 60. As a result, following steps S4 and S5, the level detection waveform determination routine of step S6 is executed, the level detection waveform in the selected pulse wave signal SSM is determined, and the hold signal SH is sent out. That is, in step S6, according to a program not shown,
The peak in the selected pulse wave signal 88M that appears immediately after the pressure P in the cuff 2 exceeds the target upper limit pressure PM is detected, and the number of peaks is counted, and as soon as the number of peaks becomes equal to 2. Hold signal SH is the selection control circuit 4
2. At that time, each pulse wave level detection circuit 18 outputs pulse wave level signals SL1 to SL3.
The content of is held in the selection control circuit 42, and the pulse wave signal amplified by an amplifier having an amplification factor according to the held content is
As mentioned above, since the selected pulse wave signal SS8 is selected by the multiplexer 32, the selected pulse wave signal SS8 is selected in the second A.
By supplying the /D converter 461C, the pulse wave signal (SM) converted into a digital signal with high resolution is input to the I/D converter 461C.
10 ports 14. Note that in this step S6, as described above, the level detection waveform is determined by counting the number of peaks of the waveform.
Until this step S6 is completed, there is no need to particularly decide which of the first to fourth amplifiers 22 to 28 to select. Further, as is clear from the above-mentioned explanation, this step S6 includes a circuit that integrally cooperates with the pulse wave level detection circuit 18 to detect the magnitude of the pulse wave signal SM. In other words, the level detection waveform determination routine of step S6 and the pulse wave level detection circuit 18 constitute a pulse wave level detection means.

After step S6 is completed, step S7 is immediately executed.

In step S7, a blood pressure measurement routine is executed according to a program (not shown), and a blood pressure value is calculated based on changes in the magnitude of the pulse wave. This blood pressure value is then supplied to the display 62 from the I10 port 14 as a display signal SD. In this blood pressure measurement routine, when the saturation signal SS is supplied from the saturation circuit 41 as described above, data conversion is executed according to a predetermined program, thereby converting the data already stored in the RAM 52. The old data of the selected pulse wave signal 88M is made to correspond to the selected pulse wave signal SSM amplified with a new amplification factor. When the necessary display signal SD is fully pressurized and step S7 is completed, step S8 is executed and the rapid discharge signal EQ is supplied to the rapid soil discharge solenoid valve 58. @ Quick exhaust solenoid valve 58
The cuff 2 is opened in response to the soil evacuation signal EQ from the cuff 2, and the air inside the cuff 2 is thereby rapidly circulated. This step S
can also be implemented in other forms.

For example, in the above embodiment, the level detection waveform is
8L7) It was supposed to be determined by the level detection waveform determination routine in the main program, but the peak detection circuit,
The determination may be made by a so-called hard circuit including a counter or the like. In this embodiment, the auxiliary saturation detection circuit 4 is added to the pulse wave level detection circuit 18.
Although the saturation detection circuit 41 is provided to cope with unforeseen situations, such a saturation detection circuit 41 is not necessarily necessary, and a certain effect can be obtained even without it. ! Historically, in the above-mentioned embodiments, the main circuits such as the pulse wave level detection circuit 18 and the selection control circuit 42 were configured as hard circuits, but they can also be configured as software.

An example thereof will be explained with reference to the block diagram shown in FIG. 4 and the program flowcharts shown in FIGS. 5 and 6. Components that have the same functions as those in the above-mentioned embodiments are designated by the same reference numerals and detailed explanations will be omitted.

First, in FIG. 4, the reference pulse wave signal SMR amplified by the reference amplifier 34 is converted into a digital signal by the third A/D converter 0 and is supplied to the I10 port 14. On the other hand, the port select terminal PS of the multiplexer 32 is supplied with a port select signal SPS from the I10 baud) 14. As shown in the flowchart of FIG. 5, an amplifier selection routine is inserted as step 86' into the main program for blood pressure measurement, which is similar to that of the previous embodiment. This step 86' is step S6
The port selection signal SPS determined in the amplifier selection routine is sent to the Ly1 multiplexer 32 to be sent to a predetermined amplifier/multiplexer. The pulse wave signal SM intensified by 1 is selected, and the blood pressure measurement routine of step S7 is executed immediately after such selection operation is completed. .

That is, the word selection routine in step 86'
The flowchart is shown in the figure, and starts when the level detection waveform is determined by the V-detection shape determination routine in step S6. First, the level sampling routine of step SRI is executed. In this level sampling routine, the voltage (peak value) (2) of the level detection waveform determined in step S6 is sampled according to a program (not shown). Note that this sampling targets the reference pulse wave signal SMR from the third A/D converter 70. Immediately after the voltage V of the level detection waveform is sampled, step SR2 is executed.

In step SR2, the voltage (hereinafter referred to as sampling voltage) of the sampled level detection waveform is the actual comparison voltage v1 of the predetermined reference pulse wave signal SMR.
(same as (1) in the above embodiment, and the same applies hereafter), and if the sampling voltage V is smaller than the comparison voltage (I), step SR3 is carried out, and if it is equal to or greater, step SR is carried out.
4 will be paid immediately. When step SR3 is executed: The port selection signal SPS supplied to the ds multiplexer 32 is such that the fourth pulse wave signals S and M4 are selectively output. Immediately after step SR3 is executed, the blood pressure measurement routine of step 1 (step S7) is executed.

On the other hand, when step SR4 is executed, the sampling voltage V is compared with the comparison voltage ■2, and the voltage V is
If it is smaller than 2, step SR5 is executed; otherwise, ld step SR5 is executed. Step SR5
In , the port set reflex signal 8PS is set to selectively output the third pulse wave signal SM3, and then step S7 is successively executed in the same manner as step SR3.

In step SR5, the sampling voltage V is further compared with the comparison voltage ■3, and when the voltage V is smaller than the voltage ■3, step SR7 is executed; otherwise, step SR8 is executed, and the port select signal S
PS is the second pulse wave signal S M 2 and the first pulse wave signal S M 2 . Pulse, 3 signal S
M Select 1, select 5: Set to . After these steps SR7 and Sn2O, step S7 is executed.

In step S7, the desired blood pressure value is calculated in the same way as in the previous embodiment.

Note that it is also possible to provide this routine with a function similar to that of the saturation detection circuit 41 in the embodiment described above. In this case, 1d, a voltage that is a predetermined ratio to the input range of the second A/D converter 46 is set in advance, and when the voltage actually input to the converter 46 exceeds the set voltage, What is necessary is to provide a step of changing the contents of the hoard select signal SPS so as to select an amplifier with an amplification factor 91 steps lower than the current one.

As is clear from the above description, in this embodiment as well, the amplification factor is automatically selected based on the magnitude of the pulse wave signal SM, and the pulse wave signal SM is always converted into a digital signal with high resolution. It will be converted. In addition, in this embodiment, from the perspective of the Third A/D converter 70. Level detection waveform determination routine (S6) in the main program, Repenon sampling routine (SRI) in the amplifier selection routine (S6), and each sampling voltage comparison step (SR2, SR4, 5R6)/φ;
! 4/"/'/f/'lJl'#fl constitutes a pulse wave level detection circuit, and - power cylinder 2 A/D converter 4
6 and further amplifier selection routine in the main program (
Each amplification factor selection step (8n3.SR5,
8R7, 5R8), it can be seen that the control means is constructed.

Furthermore, in the present invention, instead of selecting the amplifiers (22 to 28) based on the predetermined waveform (level detection waveform) of the pulse wave signal SM as in the above-described embodiment, the amplifiers are selected in advance based on the amplification factor. After setting the pulse wave signal SM to the second largest one (the amplifier 28 in the above embodiment), each time the waveform of the pulse wave signal SM is input, the saturation detection circuit (41) or an equivalent program compares the waveform level. It is also possible to adopt a configuration in which the amplifiers are shifted so that each time the waveform level reaches a predetermined value, an amplifier with a small amplification factor is selected by several stages at a time, either sequentially or depending on the level.

In this case, the saturation detection circuit (41) or a corresponding program serves as the pulse wave level inspection means, and all waveforms of the pulse wave signal become level detection waveforms.

It should be noted that the pulse wave signal SM compared in the above may be input as the selected pulse wave signal SS8 in the above embodiment or as the reference pulse wave signal SMR. Good too. This means that the saturation detection circuit (41) 119ftF\mel11 in the above embodiment
The same is true for the 21-meter system, especially the saturation detection circuit 41.
When the configuration is a hard circuit, as in the case of the circuit, there is no problem even if some of the voltages to be compared are analog voltages.

In the above description, the amplifier circuit includes four amplifiers, each having a predetermined ratio and different amplification factors, arranged in parallel. A case has been described in which a four-stage configuration is used, and the pulse wave signals of different levels outputted in parallel from this circuit are selectively enhanced by the multiplexer 32 serving as a selection circuit, but the ratio between the amplification factors, Of course, the number of amplifier stages (therefore, the ratio of comparison voltages in the pulse wave level detection circuit, the number of stages, etc.) can be changed arbitrarily as necessary, and as shown in FIG. Resistors 几1 to R4, which determine the amplification factor of 72,
and set the output signal to the second A/D converter 4.
There is no problem even if it is supplied to 6. However, it is also possible to adopt a configuration in which the selection circuit is a demultiplexer and the pulse wave signal SM is distributed to amplifiers connected to the outputs of the demultiplexer.

Furthermore, in the above embodiment, the second waveform after the external pressure inside the cuff (2) was used as the waveform for level detection;
Waveforms that appear before and after pressure increase within a range that does not interfere with calculation of blood pressure measurement values can be used as waveforms for level detection.

In addition, it is also possible to replace the first and second A/D converters 12 and 46 with one time-sharing A/D converter.

Although not listed here, it goes without saying that the invention may be implemented in various modifications and improvements within the scope of the invention.

[Brief explanation of the drawing]

FIGS. 1(a) and 1(a) are waveform diagrams for explaining a pulse wave appearing during pressure applied to a part of the human body and a pulse wave signal representing the pulse wave, respectively. FIG. 2 is a block diagram showing an embodiment of the present invention for determining blood pressure based on the waveform field shown in FIG. 1. FIG. −? 7 is a flowchart showing step 7. FIG. 4 is a block diagram showing the main part of another embodiment of the present invention, FIG. 5 is a flowchart showing the main part of the main program of the arithmetic processing device of FIG.
The figure is a flowchart showing the amplifier selection routine shown in No. 5M. FIG. 7 is a block diagram showing another embodiment of the amplifier circuit and selection circuit. 2: Cuff 4: Pressure sensor lO: Band pass filter 16: Expansion circuit 18: Pulse wave level detection circuit (pulse wave level detection means), 3
0 level control circuit (control means)

Claims (1)

[Claims] When measuring blood pressure, a pulse wave signal representing a pulse wave generated by compressing a part of the human body is converted into a digital signal using an A/D converter, and a pulse wave signal representing a pulse wave generated by compressing a part of the human body is converted into a digital signal, and a In a digital automatic blood pressure measurement device that automatically measures blood pressure of a human body, detecting the magnitude of the pulse wave signal,
a pulse/wave level detection means for outputting a pulse wave level signal representing the magnitude; and an amplifier circuit having selectable multiple stages of amplification factors, amplifying the pulse wave signal and supplying the amplified pulse wave signal to the A/D converter. and. a selection circuit for selecting an amplification factor of the amplification circuit; the amplification factor of the amplification circuit is selected based on the pulse wave level signal; and the magnitude of the amplified pulse wave signal supplied to the A/D converter; A digital type, characterized in that it is provided with a control means for controlling the width to be at least a predetermined thickness for one input range of the A/D converter, and not to exceed the input range. Automatic blood pressure measuring device.