JPS6365844A - Oximeter apparatus - Google Patents

Abstract

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

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an oximeter device for measuring the oxygen saturation level 5alt of arterial blood of a living body.

[Prior Art] In an oximeter device that uses a light emitting diode and a photodiode to detect a pulse wave signal of a living body to be measured, performs predetermined processing, and calculates the oxygen saturation level of 5aOt in arterial blood, a measurement probe is placed in the body to be measured. When attached to the measurement site, if the body to be measured moves during measurement, or if the baseline, which is the time-average voltage value of the pulse wave signal, fluctuates, the amplifier that amplifies the pulse wave signal may become saturated or the oxygen Saturation level 5
This causes an error in the measured value of aO7. In order to prevent this, for example, in the oximeter system for which a patent application was filed in Japanese Patent Application No. 61-62986, a so-called instrumental circuit was proposed that forcibly returned the detected pulse wave signal to a predetermined basic level. The circuit has a configuration similar to that of the circuit shown in FIG. In this instrument circuit, the CPU 10, which controls the entire device, connects the amplifier 01) and OF at a predetermined period.

By instantaneously turning on the switch that short-circuits the input terminals of the amplifiers OP+ and OP, saturation of the amplifiers OP+ and OP is stopped, and the oxygen saturation level 5alt can be accurately measured.

[Problems to be Solved by the Invention] However, in the instrumentation circuit of the oximeter device shown in FIG. 4, when the instrumentation switches S and S3 are off, the input terminals of the amplifiers OP1 and OPt are The coupling provided between the
Bias 7[i currents of the amplifiers OP and OPt flow through the capacitors C3 and C2, and charges are accumulated in the capacitors C8 and C7, and then when the switches S and S3 are turned on, the charges are discharged. Ru. In addition, switch S,
A coupling capacitance exists between each input terminal of the amplifiers op, OP t and the ground through the switches S and S, and this coupling capacitance causes the amplifier OP to switch on and off when the switches S and S are turned on and off.
The voltage at each input terminal, + and OP, fluctuates.

Therefore, due to the bias current of the amplifiers OP and OF2 and the coupling capacitance of the switch S and 83,
, amplifier OP I and O when skin S3 is turned on and off
There was a problem in that voltage fluctuations at each input terminal of P caused an error in the measured value of the oxygen saturation level S a Ot of arterial blood.

An object of the present invention is to solve the above problems, and to solve the problem of the oxygen saturation of arterial blood, which includes an error at the time of turning on and off the switch for instrumentation in the instrumentation circuit of an oximeter device.
The object of the present invention is to provide an oximeter device that can correct the measured value of alt and can accurately measure the oxygen saturation Sad.

[Means for Solving the Problems] The present invention provides an amplifying means for amplifying a pulse wave signal of a living body to be measured; an instrument means for setting the signal to a predetermined base d^ level, and a predetermined signal (including no signal) to the amplification means.
storage means for storing the output of the amplification means over time from the point in time when the instrumentation means is operated in a state in which the instrumentation means is operated manually; Calculating means for subtracting a value stored in the storage means corresponding to a predetermined time after the operation of the instrument means from the output of the means, and calculating the oxygen saturation of the arterial blood of the living body to be measured based on the subtracted value. It is characterized by having the following.

[Function] With the above configuration, even if an error occurs in the measured value due to the bias current of the instrument means connected to the input terminal of the amplifying means or the amplifying means, the measured value can be corrected by the arithmetic means. can do.

[Embodiment] FIG. 1 is a block diagram of an oximeter device that is an embodiment of the present invention.

In FIG. 1, the oximeter device is composed of a probe l and a device main body 3, and inside the device main body 3 is a signal processing circuit 7 that processes the output of a light receiving element 25 in the probe 1, which will be described later.
, a multiplexer 8 for selecting the output of the signal processing circuit 7;
A converting the output of multiplexer 8 into a digital signal
/D converter 9, a CPU 10 that calculates the oxygen saturation level 5aOt of arterial blood and pulse rate, and controls the display section 13, operation section 14, etc., which will be described later, and a read-only memory (hereinafter referred to as 110).
It's called M. ) II, random access memory (hereinafter referred to as T
(referred to as A M) 12. A display section 13 that displays the calculated oxygen saturation level S a O2 of arterial blood, pulse rate, etc., an operation section 14 that selects the alarm level, measurement mode, and display mode, and an alarm sound. and an audio output unit 15 that emits a pulse sound, an input/output unit 16 that exchanges data with a dedicated printer or an external computer and outputs a pulse waveform, and an input/output unit 16 that outputs a pulse waveform, and an IC card 2 that is removable for storing measured values. An ICC card input/output section 17 and a clock section 18 are provided, as well as a driving section 19 for lighting up light emitting diodes (hereinafter referred to as LEDs) 20 and 21. A probe 1 is detachably connected to 3.

Probe l is a red light emitting diode (hereinafter referred to as nLED) that emits red light around 660 nm 20.9
= Infrared light emitting diode (hereinafter referred to as IRLED) 21 that emits infrared light around 10 nm, temperature detection section 22 that outputs a signal corresponding to the temperature of RLED 20 or IRLED 21, and determines whether it is a spot measurement probe or a continuous i++ regular probe. a probe identification output unit 24 that outputs a signal for the purpose of detecting a signal; a light receiving element 25 that is a photodiode that receives the light emitted from the RLED 20 and the IRLED 21 and passes through the living body 60 and outputs a signal according to the intensity of the light; A photoelectric conversion circuit 37 that converts the output of the element 25 into an electrical signal, and a nonvolatile memory circuit that is connected to the CPUtO in the device main body 3 and stores information on the emission spectrum of the RLED 20 and the IRLED 21, crosstalk information, and sum check data. It consists of 56 pieces.

Note that this memory circuit 56 can be electrically written into and erased from EEF ROM or El"R.
It may be configured with an OM or a digital switch.

Next, a detailed explanation of the signal processing circuit 7 will be given, and the oxygen content of arterial blood in this example will be explained in detail.

The measurement principle will be explained. Wavelengths λ1 and λ.

When the living body 60 is irradiated with light of
O+

However, here, lot: Incident light intensity 1o at wavelength λ: Incident light intensity E+ 0 at wavelength λ8 Extinction coefficient E, H of oxyhemoglobin at wavelength λ8: Extinction coefficient E, H of oxyhemoglobin at wavelength λ2: Extinction coefficient EfH of hemoglobin at wavelength λ: Extinction coefficient Tt+ of hemoglobin at wavelength λ Transmittance of tissues other than arterial blood at wavelength λ1 Ttt: Transmittance of tissues other than arterial blood at wavelength λ d: Thickness of arterial blood layer Time average value △d: Time variation component of arterial blood layer thickness 5alt:
Arterial blood oxygen saturation g+, g*+ gain coefficient.

Here, the intensity of light of each wavelength after passing through the living body 60 is 1, , I
Let the DC components of , I , DC, I , and DC respectively, log(1, DC/I
Dc/I 2) respectively U,,U! Then, U,
, U, are each approximately expressed as: . . . (3) . . . (4). Also, here, U, , U, are each I
As the temporal variation component of ogl +, logI, (3
X4), and furthermore, T 1. When the temporal fluctuation components of I t are respectively Il and △■2, then U +
, tJ 2 to I, /I, DC, ΔI, respectively
Even if it is calculated as t/1-DC, the formula (3X4) can be obtained. Then, by solving the equation (3X4') for 5aOt, the following equation is obtained.

・・・・・・・・・(5) From equation (5), the oxygen saturation Sad of the arterial blood is determined. Here, K, , , , , are wavelengths λ3, respectively.
．． It is a constant determined by λ. In this example, wavelengths λ1 and λ are around 660 nm and 9 nm, respectively.
A wavelength around 40 nm is used.

Furthermore, the signal processing circuit 7 of the device main body 3 in this embodiment
The configuration will be explained using FIG.

In this embodiment, as described above, the light source is mainly 6
RLEDs 20 and 9 emit red light with a wavelength around 60 nm
IRL, El) that emits infrared light with a wavelength around 40 nm
2+ is used. Each LED 20.2+ is driven by an LED drive unit 19 that is controlled according to a timing pulse output from an oscillation circuit built in the CPU10, and here the LED drive unit 19 is
As shown in a) and (b), two series of drive cycle pulses with the same period but a phase difference of 90° and a duty ratio of 50% are output to each LED 20.21, and each LED 2
0,21. The light emitted from each LED 20, 21 passes through the living body 60, is attenuated, and is received by the light receiving element 25. The light receiving element 25 outputs a current corresponding to the intensity of the incident light, and this output current is converted into a voltage signal by the photoelectric conversion circuit 37 and output to the terminal a+ of the switch S.

Here, when the device main body 3 is set to the measurement mode, the switch S is connected to the terminal al, and therefore the output of the photoelectric conversion circuit 37 is amplified by the amplifier 8S38, and then R
The signal is input to a synchronous rectifier 39 and an In synchronous rectifier 40 . The R synchronous rectifier 39 and the IR synchronous rectifier 40 rectify the manually input photoelectric conversion signal in synchronization with two series of drive cycle pulses output from the LED drive unit 19 . That is,
The R synchronous rectifier 39 amplifies the power signal from which the RLED 20 is emitting light to a factor of 1, and amplifies the power signal from which the RLED 20 does not emit light by a factor of 11. Similarly, the In synchronous rectifier 40 amplifies the power signal from which the IR LED 21 is emitting light by a factor of 1, and the power signal from which the III LED 21 does not emit light by a factor of 11. In addition, Fig. 3(c),
(d) and (e) are the outputs A1 and R of the amplifier 38, respectively.
Output AR of the synchronous rectifier 39.

and the waveforms of the output A I RI of the tR synchronous rectification unit 10 are shown.

Therefore, if the outputs of each synchronous rectifier 39 and 40 are averaged over time, the outputs of RLED 20 only and IRL
It corresponds to the intensity of light emitted only from the ED 21 and incident on the light receiving element 25 through the living body 60. Therefore, the outputs of the R low-pass filter 41 and the In low-pass filter 42 correspond to the intensity of light around 660 nm and around 940 nm that passed through the living body 60, respectively. When separating the signals of light incident on the light receiving element 25 into signals corresponding only to each wavelength in this way, each l4ED
By appropriately selecting the drive frequencies 20 and 21, the influence of external light can be removed.

The frequency determination unit 53 in FIG. 2 determines the frequency of the commercial power supply being used, and according to the output, the CPU 10 sets the driving frequency of each LED 20.21 to approximately (an integer multiple of 60 + 3).
0) Hz (when the commercial power frequency is 60 Hz), or approximately (an integer multiple of 50 + 25) Hz (when the commercial power frequency is 50 Hz)
Hz).

Furthermore, the outputs of the R low-pass filter 4I and the In low-pass filter 42 are sent to a digital analog converter (hereinafter referred to as an A/D converter) via a multiplexer 8.
9, it is A/D converted and manually inputted to CPU 10. CPU
l0 determines the ratio of the output of the R low-pass filter 41 and the output of the IR low-pass filter 42. Then, one LED driving section is controlled so that the ratio falls within a predetermined range, and the light emission intensity of RLED 20 is adjusted to 5 and IF7.1. ED
Adjust the luminescence intensity of 21. As a result, the S/N ratio of the output of the R low-pass filter 41 and the S/N ratio of the output of the 1z low-pass filter 42 become approximately equal, and a favorable state for signal processing can be maintained.

In FIG. 2, CPU10 is the R low-pass filter 41
The gain of the amplifier 38 is adjusted so that the output of the In low-pass filter 42 and the output of the In low-pass filter 42 are within a predetermined range. Further, the output of the In low-pass filter 42 is connected to a signal line 51 that is output to the outside of the main body 3. Further, the outputs of the R low-pass filter 41 and the In low-pass filter 42 are connected to an R log amplifier 43 and an IR log amplifier 44, respectively, and the R bypass filter I.
147, an IR bypass filter 146, and an In bypass filter 147, and then input to the multiplexer 8. Also, ■) Bypass filter 1147 and T
The output of the R bypass filter II48 is also input to the multiplexer 8 via an R inverting amplifier 49 and an R inverting amplifier 50, respectively. Here, R bypass filter 1
When the outputs of 47 or In bypass filter lI48 are positive, their outputs are passed through multiplexer 8 to A/
It is A/D converted by the D converter 9, but if the output is negative, the output of each inverting amplifier=19.50 is A/D converted and output to the CPU10. Furthermore, the outputs of the R low-pass filter 41 and the IR low-pass filter 42,
Output of R bypass filter [47 or R inverting amplifier 4
9 output, IR bypass filter [48 output or I
The output of the R inverting amplifier 50 is A/D converted by the A/D converter 9 at a predetermined sampling period, and CPt
Output to JIO. Further, the CPU 10 can calculate the oxygen saturation level S a Ot of arterial blood by calculating the above-mentioned equation (5) based on the input A/D conversion value.

Further, the output of the II bypass filter +45 is inputted to a comparison circuit 59 via a low-pass filter 57 having a predetermined cut-off frequency, while the output of the In bypass filter 14
6 is input to a comparison circuit 59 via a low-pass filter 58 having a predetermined cutoff frequency. The comparison circuit 59 outputs a match signal Q3 to the CPU10 when the outputs of the low-pass filters 57 and 58 match. The operation of this comparison circuit 59 will be described in detail later.

FIG. 4 shows specific configurations of the R bypass filter 145 and the R bypass filter lI47 in FIG.
The R bypass filter 146 and the I IN bypass filter 1.18 are similarly constructed. The instrumentation function of the oximeter device according to the present invention will be explained below with reference to FIG.

In FIG. 4, the output of the R log amplifier 43 is connected to the input terminal of the amplifier OF through the coupling capacitor CI in the R bypass filter +45.
The input terminal of 50P1 is connected to ground via a resistor R7 and also to ground via a switch S controlled by CPU10. The output terminal of the amplifier OP of the R bypass filter +45 is connected to the input terminal of the amplifier OP through a coupling capacitor C2 in the R bypass filter lI47, and the input terminal of this amplifier OP is connected to ground through a resistor R1. and connected to ground via switch S3 controlled by CP (JlO).R bypass filter lI47
The output terminal of the amplifier OP t is connected to the multiplexer 8 and the inverting amplifier 49 of FIG.

In the oximeter device configured as described above, when the living body 60 is inserted between each of the LEDs 20 and 21 and the light receiving element 25 as shown in FIGS. 1 and 2, the light receiving element 2
The intensity of the light incident on the filter 5 changes rapidly, and the output A1 of the amplifier 38 and the output of the R bypass filter 1147 become saturated. Here, R bypass filter +45. IR bypass filter 146, R bypass filter [147 and In
Since the time constants of the bypass filters 1I48 are set to be large so that even low frequency signals can be measured, their outputs remain saturated for a long time. That is, as shown in FIGS. 5(a) and 5(b), when the living body 60 is not inserted into the probe l, the input OP+i and the output OP of the amplifier OP of the R bypass filter 145. is a constant value, but when the living body 60 is inserted into the probe l, the intensity of the light incident on the light receiving element 25 changes rapidly, and the output oP1o of the amplifier OP reaches a saturation state. Its output OPl. Once the voltage reaches O [V], the average voltage shows a characteristic that the average voltage gradually increases while changing due to pulsations. Likewise, amplifier OP is also saturated, and therefore amplifiers OP and O
It takes a considerable amount of time for the output of Pt to become stable and measurable.

Therefore, in this embodiment, the A/D converted R7\ipass filter [14
7, the output of the R inverting amplifier 19, the output of the R bypass filter 118, and the output of the IR inverting amplifier 50 for a predetermined period of time or more. As shown in j), the CPU 10 sends control signals color and h to the switches S2 and S to turn on the switches S and S3 for a minute time w.

As a result, as shown in FIG. 5(c), the amplifier OP
The saturation of the output OP1° of , is released in a short time, and thereafter, the output of the amplifier OP1° is released.

can output a signal corresponding to the fluctuation components included in the outputs of the R log amplifiers 43 and 44.

Therefore, according to this embodiment, the saturated state of the amplifiers OP1 and OP at the start of measurement is immediately released by turning on the switches S and S3, and measurement becomes possible.

Further, the outputs of the R log amplifiers 43 and 44 generally include noise 61 peculiar to the pulse wave signal, which fluctuates at a frequency lower than the frequency of the signal component. FIG. 6(a) shows the output of the amplifier OP, which is the output after amplifying the outputs of the R log amplifiers 43 and 44, and as shown in FIG. 6(a), the noise 61 is Since the output levels of the log amplifiers 13 and 44 are gradually varied, this becomes a factor of error when determining Sang. Therefore, in this embodiment, as described above,
The outputs of the R bypass filter I.15 and the lR bypass filter 1146 are connected to low pass filters 57 and 5, respectively.
8 to extract the low frequency component and input it to the comparison circuit 59. The comparator circuit 59 outputs a control signal Q3 to the CPLJ 10 when the levels of both low frequency components match, and in response, C1''LIIO sends a control signal Q with a minute pulse width W to the switch S3. , the switch S3 is turned on instantaneously.As a result, when the input signal of the R bypass filter 1147 reaches a level approximately between the -L limit value and the lower limit value, the CPU10 is turned on as shown in FIG. 6(C).
The switch S3 is turned on instantaneously by the control signal Q from the control signal Q, and as shown in FIG.
1, thereby eliminating measurement errors due to low frequency components of the outputs of the R log amplifiers 43 and 44.

In this embodiment, the switch S is turned on twice per cycle of the human input signal, but the switch S3 may be turned on once per cycle.

Due to the above-mentioned instrument function in the signal processing circuit 7 shown in FIG.
8. Even if OP and OP become saturated, it can be immediately released and measurement can be restarted promptly. In addition, the above-mentioned instrumentation function of the switch S3 can attenuate the low frequency component of the pulse wave signal itself, making it possible to reduce errors in measured values.

However, in the signal processing circuit 7 having the above-mentioned instrumental function, there are problems caused by the coupling capacitance in the switch S3 in the R bypass filter L47 and the IR bypass filter 1148, as well as the problems caused by the coupling capacitance in the R bypass filter I47 and the IR bypass filter I48. There are two problems, one due to the bias current in the amplifier OP.

In the former problem, when the switch S is on, the capacitance between the input terminal of the amplifier OP and the ground via the switch S3 (mainly the coupling capacitance of the switch S) is hereinafter referred to as the switch S.

is called the coupling capacity of ), and then when the switch S is turned off, the charge accumulated in the coupling capacitance of the switch S3 is discharged via the resistor R7, as shown in FIG. 7(a). amplification? The voltage at the input terminal of 50 P* fluctuates. In other words, the input voltage of the amplifier OP when only the coupling capacitance of the switch S is considered and the pulse wave signal input to the amplifier OP is removed is 0Pz.
i is switch S.

is on, the voltage is 0 [V], and then the switch S
3 is turned off, the input voltage 0Pti exhibits a characteristic of becoming a predetermined negative voltage and then gradually asymptotic to O[V].

Next, in the latter problem, when the switch S3 turns from on to off, there is a potential difference across the capacitor C2, and the capacitor Ct is connected to the input terminal of the amplifier OP.
Since one end has a lower potential than the other end, the amplification A
The bias current of OPt flows through the input terminal of the amplifier OP to the capacitor C2, the charge is accumulated in the capacitor C1, and then when the charging of the capacitor C7 is finished,
The bias current of the amplifier OPt flows to ground via the resistor R, and is in a steady state.

Considering only the bias current of this amplifier OP, and removing the pulse wave signal input to the amplifier OPt, the amplifier O
As shown in FIG. 7(b), the input terminal OP,i of P is O[V when the switch S3 is on, and then when the switch S3 is turned off, the input voltage 0Pzi gradually decreases. It exhibits the characteristic of increasing and asymptotic to a predetermined steady-state value.

When considering both the coupling capacitance of the switch S and the bias current of the amplifier OPt, and removing the pulse wave signal input to the amplifier OP, the input terminal OPt i of the amplifier OP is the seventh Switch S as shown in figure (C)
, is 0 [V] when switch S3 is turned off, and after that, when switch S3 is turned off, input voltage 0Pti once reaches a predetermined negative voltage, and then gradually rises and asymptotically approaches a predetermined positive voltage.

Therefore, due to the coupling capacitance of the switch S and the bias current of the amplifier 0I) when the switch S is switched from on to off, the amplifier OP! An error voltage generated in the input voltage causes an error in the measured value of the arterial blood oxygen saturation Sad.

In order to solve this problem, in this embodiment, with the input to the capacitor Ct set to zero in advance, for a predetermined time period from the time when the switch S3 is switched from on to off, at predetermined time intervals, CPTJ l O is R bypass filter lI47 and IR bypass filter lI14
After storing the output of amplifier OPt, which is the output of
Depending on the time from the so-called installation time of switch S3, which is the time of switching from on to off of switch S3,
R bypass filter [47, IR bypass filter [4]
8. Correct the A/D conversion values of the respective outputs of the R inverting amplifier 49 and the IR inverting amplifier 50 based on the data stored in the RAMI2. Hereinafter, a method for correcting the error voltage caused by the coupling capacitance of the switch S and the bias current of the amplifier OPt during the installation by the switch S3 will be described with reference to the flowcharts of FIGS. 8 and 9.

In FIG. 8, when the power switch of the okinmeter device is first turned on in step l, the process proceeds to step 2, where the device is initialized and the memory circuit in the probe 1 is
Data regarding each LED 20, 21, etc. stored in CPU 10 is loaded into RAM+2 via CPU10.

Next, in step 3, the above-mentioned switch S is applied.

Measure and store the error voltage during the instrument operation. The operation of step 3 is performed based on the subroutine flowchart shown in FIG. 9. First, in step 5I, switch S in the R bypass filter 145 is turned on, and then, in step 52, switch S3 is turned on momentarily. .

The measurement time of this error voltage is set to the time required for the input voltage of the amplifier OP shown in FIG. 7(C) to reach a predetermined steady-state value after the switch S3 is activated.

Further, the process proceeds to step 53, where the R bypass filter lI4
7, IR bypass filter lI14, R inverting amplifier 49
, and the outputs of the IR inverting amplifier 50 are measured and A/D converted, and in step 54, these A/D converted values (hereinafter referred to as A/D converted values of error voltage) are converted to RA.
Store in M12.

Next, in step 55, the error voltage measurement is repeated a predetermined number of times (hereinafter referred to as the number of error voltage measurements) when the error voltage is measured at predetermined time intervals within the above-mentioned measurement time. In other words, it is determined whether the measurement has been performed for a predetermined error voltage measurement time, and when the error voltage measurement has been repeated a predetermined number of times, the process proceeds to step 56; If the error voltage measurement has not been performed a predetermined number of times, the process returns to step 53;
Re-manipulate the process described above. Furthermore, after the switch St is turned off in step 56, the process proceeds to step 4 in FIG.

After step 1, the oxygen saturation level 5alt of the arterial blood of the living body 60 is measured, and in step 4, first, as described above, depending on the sign of the output of the R bypass filter lI47, the R bypass filter 17 or the R After A/D converting the output of the inverting amplifier 49, the A/D converted value is stored in the RAM 12, and then in step 5, the TR
After A/D converting the output of the TR bypass filter lI48 or the IR inverting amplifier 50 according to the sign of the output of the bypass filter lI48, the A/D converted value is expressed as I'(AM1
Store in 2.

Furthermore, in step 6, the R bypass filter 11
47 or the A/D conversion value of the output of the R inverting amplifier 49, the corresponding A stored in the RAM 12 in step 54
/D conversion value is subtracted and corrected, and the difference value is stored in RAM1.
2, and TR bypass filter lI48
Alternatively, from the A/D conversion value of the output of the IR inverting amplifier 50, the corresponding A/D conversion value stored in the RAM 12 in step 54 is calculated.
Perform correction by subtracting the D conversion value, and store the difference value in RAMI2.
to be memorized. In the correction of the A/D conversion value in step 6, the A/D conversion value measured in steps 4 and 5 is adjusted according to the elapsed time after the switch S is installed.
Correction is performed using the measured value of the error voltage measured in step 53 during the elapsed time. Furthermore, after the oxygen saturation level 5alt of the arterial blood of the living body 60 is calculated by the above-mentioned equation (5) based on the value stored in ItAMI2 calculated in step 6, the calculated value is displayed on the display unit 13. . It is then determined in step 8 whether this measurement is to be terminated, and if so, proceeding to step 9 and the oximeter device is stopped, while if this measurement is to be continued, proceeding to step 4 and as described above. Repeat the process.

In the above embodiment, in steps 53 to 54 of FIG. 9, the error voltage is measured and stored at predetermined time intervals for the above-mentioned predetermined time period after the switch S3 is installed, but immediately after the switch S3 is installed. It is also possible to measure only the error voltage at a steady state of the error voltage and the error voltage, and use the error voltage between them to obtain the error voltage by an appropriate interpolation method such as linear interpolation, and use it as the correction amount in step 6.

[Effects of the Invention] As detailed above, according to the present invention, the pulse wave signal input to the amplification means is measured after a predetermined time from the operation of the instrumentation means to bring the pulse wave signal input to the amplification means to a predetermined reference level. From the output, a value based on the data stored in the storage means corresponding to after the predetermined time, that is, the output of the amplification means is obtained by subtracting the output of the amplification means after the predetermined time from the operation of the instrumentation means. Since the oxygen saturation of the arterial blood of the living body to be measured is calculated based on the measurement result, even if an error occurs in the oxygen saturation measured by, for example, the bias current of the instrument means connected to the input terminal of the amplification means or the amplification means. , there is an advantage that the measured value can be corrected by the arithmetic means, and therefore the oxygen saturation can be accurately measured.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the overall configuration of an oximeter device that is an embodiment of the present invention, FIG. 2 is a block diagram of a signal processing circuit of the device shown in FIG. 1, and FIG. 3 is a block diagram showing the signal processing circuit of the device shown in FIG. A timing chart showing the waveforms of each part of the processing circuit, FIG. 4 is a circuit diagram of IT bypass filters I and ■ and IFL bypass filters I and H in FIG. 2, FIG.
6 and 7 are timing charts showing the waveforms of each part of the R bypass filters l and 11 and the IR bypass filters 1 and H in FIG. 4, and FIGS. 8 and 9 are switch S3 in the device in FIG. 1. What is the error voltage during installation? l+? It is a flowchart which shows the operation|movement for correcting. 1... Probe, 3... Oximeter device main body, 7... Signal processing circuit, 2... Multiplexer, 9... Analog-digital converter (A/D converter)
, lO...CPU. II... Read only memory (ROM), 12...
Random access memory (RAM), l3... Display section, 20... Red light emitting diode (RLED), 21.
・・Infrared light emitting diode (IRLED), 37・
...Photoelectric conversion circuit, 38...Amplifier, 39...R synchronous rectifier, 10...In synchronous rectifier, 4! ...R low pass filter, 42...IR low pass filter, 43...R log amplifier, 44...Ifl log amplifier, 45...R bypass filter I. 46... IR bypass filter 11 47... R bypass filter ■, 48... IR bypass filter ■, 49... R inverting amplifier, 50... IR anti-inverting amplifier, 56... memory circuit, 57.58...Low pass filter, 59...Comparison circuit, 60...Biological body, OP 1. OP t...Amplifier, C,, C,...Capacitor, Rl, Rt...Resistor, S=, St, S3...Switch. Patent Applicant Minolta Camera Co., Ltd. Agent Patent Attorney 2 people mentioned above No. 37 Figure 4 Figure 5 Figure 6 Figure 7 - Cloud 8 Figure 9 #1

Claims (1)

[Claims] (1) an amplifying means for amplifying the pulse wave signal of the living body to be measured; an instrument means for setting the input of the amplifying means to a predetermined reference level when the pulse wave signal is input to the amplifying means; and the amplifying means storage means for storing the output of the amplification means over time from the time when the instrumentation means is operated with a predetermined signal (including no signal) being input to the instrumentation means; The value stored in the storage means corresponding to a predetermined time after the operation of the instrumentation means is subtracted from the output of the amplification means measured after a predetermined time, and the arterial blood of the living body to be measured is calculated based on the subtracted value. An oximeter device characterized by comprising a calculation means for calculating the oxygen saturation level of the oximeter.