KR101002365B1 - Measuring System of Pulse Transit Time and Method thereof - Google Patents

Abstract

The present invention relates to a pulse transit time (PTT) measuring system and a method thereof, and more particularly, to extract feature information from an analog signal processing circuit from signals of electrocardiogram (ECG) and photoelectric exclusive pulse wave (PPG). In addition, the present invention relates to a pulse wave propagation time measurement system and method for easily calculating a PTT by outputting information corresponding to a PTT in a width of a waveform. In the pulse wave propagation time measuring system according to the present invention, an ECG electrode and an ECG detecting circuit for detecting ECG, a PPG sensor and a PPG detecting circuit for detecting PPG, and the ECG and PPG signals are differentiated, respectively, and thus the slope of the ECG and PPG signals is steep. The differential and the derivative ECG value and PPG value are highlighted, and the output value is 1 when the ECG value or the PPG value is large and 0 when the value is small. Comparator for detecting peak and feature points from ECG and PPG, and output from waveform generator using waveform generator and self-provided timer / counter for generating a clock for a predetermined time when peak and feature points are detected through the comparator And a microprocessor for calculating a PTT by calculating a time difference between the clock rising point of the ECG and the clock rising point of the PPG.

Description

Pulse wave transit time measurement system and its method {Measuring System of Pulse Transit Time and Method

The present invention relates to a pulse transit time (PTT) measuring system and a method thereof, and more particularly, to extract feature information from an analog signal processing circuit from signals of electrocardiogram (ECG) and photoelectric exclusive pulse wave (PPG). In addition, the present invention relates to a pulse wave propagation time measurement system and method for easily calculating a PTT by outputting information corresponding to a PTT in a width of a waveform.

In general, ECG signals and pulse wave signals are the most basic of the biological signals and contain a lot of health information. In this case, the electrocardiogram is a curve recording the action current according to the contraction of the heart, and diagnoses various cardiac diseases, for example, aberrations and excitatory conductions of parts where electrical excitation occurs in the heart such as atrial fibrillation, ventricular hypertrophy, myocardial infarction, and arrhythmia. Used to know the above. In addition, the pulse wave refers to a pulse formed by the pulse transmitted to the peripheral nerve, and when a microscopic abnormality occurs in the function of the heart or peripheral blood vessels, it is used to diagnose heart disease or vascular disease because the abnormality is reflected in the pulse wave. The ECG and pulse wave contain a lot of health information in our body, and it helps us to understand our health condition easily.

Pulse wave transit time (PTT), which is the time delay of electrocardiogram and pulse wave, is the time between the peak of electrocardiogram R wave and the reference point of pulse wave measured at the peripheral part of the human body, and the pulsating pressure wave is transmitted from the aortic valve to the peripheral part. It's time. This PTT is proportional to the purity of the blood vessels and is dependent on the distance of the vessels, the diameter of the vessels, and the structural properties of the vessel walls. In order to calculate the PTT, the ECG and pulse wave are simultaneously measured to calculate the time between the R-peak of the ECG and a specific point of the pulse wave.

As shown in FIG. 1, an ECG is detected using an ECG electrode 10 in an ECG (electrocardiogram) detection circuit 12, while a PPG sensor is detected in a PPG (photoplethysmography) detection circuit 22. PPG is detected using 20 to output each analog signal to the microprocessor 30. The microprocessor calculates the PTT by converting the analog signal into a digital signal and extracting the peak value of the ECG and the feature point of the PPG by a digital signal processing technique.

However, in the conventional PTT system, analog ECG and PPG signals must be sampled at high speed in order to calculate the PTT (the resolution of the PTT is determined according to the sampling rate). There is a problem that a lot of load is generated in the transmission. In particular, when the biosignal measurement is not for diagnosis but for health monitoring, the electrocardiogram uses a frequency band of about 35 Hz and about 10 Hz for pulse wave, but it requires hundreds of samplings per second to calculate the PTT. There is a problem that the amount of data is huge, there is a problem that the system requirements for high-speed sampling and data processing is increased. In addition, such a problem could cause a very big problem in the ultra-compact, battery-powered system for health monitoring in daily life.

Meanwhile, a technology for calculating a PTT value using ECG and PPG information is disclosed in a recording medium on which a blood pressure regulating function measuring device and a program recorded in Korean Patent Registration No. 10-0861337 are recorded. High-speed A / D conversion is required because the PTT is calculated by program after conversion to signal.

In addition, in the case of the blood pressure detection method and apparatus of the Korean Patent Laid-Open Publication No. 10-2008-0090194, a method of converting ECG and PPG into a digital signal and then processing the same is applied, so that the high-speed A / D conversion described above is required. .

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and extracts feature information necessary for PTT calculation from signals of ECG and PPG through an analog signal processing circuit, and outputs information corresponding to PTT in the width of a microprocessor. It is an object of the present invention to provide a pulse wave propagation time measurement system and a method thereof, which can easily calculate a PTT using a flip flop or the like, and can significantly reduce the signal processing burden.

Pulse wave transmission time measurement system according to the present invention for achieving the above object is an ECG electrode and ECG detection circuit for detecting ECG (electrocardiogram) and PPG sensor and PPG detection circuit for detecting PPG (photoelectric pulse wave); A differentiator for differentiating the ECG and PPG signals, respectively, to highlight a feature portion in which slopes of the ECG and PPG signals change abruptly; The differential ECG value and the PPG value are compared with the preset values, respectively, and output 1 when the ECG value or the PPG value is large, and output 0 when the value is small to detect the peak value and the characteristic point from the differential ECG and PPG value. Comparator; A waveform generator for generating a clock for a predetermined time when the peak value and the feature point are detected through the comparator; The microprocessor includes a microprocessor that calculates a PTT (pulse wave propagation time) by calculating a time difference between the clock rising point of the ECG and the clock rising point of the PPG output from the waveform generator using a self-equipped timer / counter.

In addition, the pulse wave propagation time detection method according to the present invention is a first step of extracting the characteristic information required for PTT calculation from the signals of the ECG and PPG through an analog signal processing circuit, and outputs the information corresponding to the PTT in the width of the waveform It is characterized by consisting of a second step of calculating the PTT.

According to the problem solving means described above, feature information necessary for PTT calculation is extracted from signals of ECG and PPG through an analog signal processing circuit, and information corresponding to the PTT is output in the width of a waveform so that the PTT can be easily used in a microprocessor or flip-flop. Can be calculated to significantly reduce the signal processing burden.

Hereinafter, a pulse wave propagation time measuring system and a method thereof according to the present invention will be described in detail with reference to the accompanying drawings, and the following drawings and the description only show the best mode of the present invention by way of example. It is not intended to be limiting. In the following, ECG is expressed as a peak value in the case of ECG and a characteristic point in the case of PPG, but the meaning is the same.

2 is a block diagram of a PTT measurement system according to a first embodiment of the present invention.

Referring to FIG. 2, the ECG electrode 40, the PPG sensor 50, the ECG detection circuit 42, the PPG detection circuit 52, the differentiators 44 and 54, the comparators 46 and 56, and the waveform generator ( 48, 58 and a microprocessor 60. At this time, the ECG electrode 40 detects the ECG and outputs an electrical signal. In general, an Ag-AgCl electrode is used. The ECG detection circuit 42 amplifies and filters the electrical signal detected by the ECG electrode 40.

Fig. 3 is a detailed block diagram of the ECG detection circuit shown in Fig. 2, showing a low pass filter 42a, a preamplifier 42b, a high pass filter 42c, a twinty notch filter 42d, an amplifier 42e, and a low pass. It is comprised including the pass filter 42f. In this case, the low pass filter (LPF) 42a filters noise of, for example, a cutoff frequency of 35 Hz or more, and the preamplifier 42b uses a differential amplifier having a high input impedance, for example, to detect an ECG signal. Amplify by double. The high pass filter (HPF) 42c removes baseline fluctuations, for example, by filtering out a noise having a cutoff frequency of 0.05 Hz or less. The T-T Notch Filter 42d varies the Q value to filter electrical signals, for example, power supply noise having a cutoff frequency of 60 Hz. The amplifier 42e amplifies by 20 times, for example, and the low pass filter LPF 42f once again filters out noise, for example, a cutoff frequency of 35 Hz or more.

Meanwhile, in FIG. 2, the PPG sensor 50 detects PPG and outputs an electrical signal. The PPG sensor 50 is composed of a near-infrared LED and a photodiode, and according to the amount of reflected light corresponding to the amount of oxidized hemoglobin according to the volume change in the peripheral blood vessel of the finger. Detect the current. At this time, the PPG detection circuit 52 amplifies and filters the electrical signal detected by the PPG sensor 50.

FIG. 4 is a detailed block diagram of the PPG detection circuit shown in FIG. 2, which shows a current / voltage converter 52a, a twinty notch filter 52b, a high pass filter 52c, an amplifier 52d, and a low pass filter 52e. It is configured to include. At this time, the current / voltage (I / V) converter 52a detects the current change according to the amount of light from the signal output from the PPG sensor 50, thus converting the current change into a voltage signal and filtering out noise of 10 Hz or more. Performs a lowpass filter function. In addition, the twinty notch filter 52b filters power supply noise having a cutoff frequency of 60 Hz to remove noise due to power and noise that may exist due to a change in optical characteristics of the light source itself. The high pass filter HPF 52c filters the noise having a cutoff frequency of 0.5 Hz or less to block the offset signal of the PPG sensor 50. Then, the amplifier 52d amplifies the PPG signal passing through the high pass filter 52c, and the low pass filter LPF 52e filters noise, for example, a cutoff frequency of 10 Hz or more. Each differential 44,54 consists of analog differential circuits, differentiates ECG and PPG signals to remove the baselines contained in the ECG and PPG signals, and rapidly changes the slope of the ECG and PPG signals (ECG). R wave part, and the rising part of PPG) are highlighted. The comparators 46 and 56 compare the differentiated ECG values or PPG values with the set values set in the comparators 46 and 56 themselves to output waveforms at peak and feature points from the differentiated ECG and PPG signals. If the value or the PPG value is large, 1 is outputted, and if the value is small, 0 is outputted to detect peak values and feature points from the differential ECG and PPG (see FIGS. 6 and 7). The waveform generators 48 and 58 generate a clock for a predetermined time using the monostable oscillator when the peak value and the feature point are detected through the comparators 46 and 56. The microprocessor 60 calculates the PTT by calculating a time difference between the clock rising point of the ECG and the clock rising point of the PPG, which are output from the waveform generators 48 and 58, using the self-equipped timer / counter 62. (See FIG. 8).

In the configuration of the first embodiment as described above, the ECG is detected using the ECG electrode 40 and the ECG detection circuit 42, while the PPG sensor 50 and the PPG detection circuit 52 are used to detect the PPG, and the differential powder 44 54) removes the baseline included in the ECG and PPG signals by differentiating the ECG and PPG signals, and highlights the characteristic portions (the R wave portion of the ECG and the rising portion of the pulse wave) in which the slope of the ECG and PPG signals changes rapidly. Let's do it.

Next, the comparators 46 and 56 detect peaks and feature points from the differentiated ECGs and PPGs by comparing the differentiated ECG values or PPG values with the set values set in the comparators 46 and 56, and the waveform generators 48 and 58. ) Generates a clock for a predetermined time when the peak value and the specific point are detected through the comparators 46 and 56, and the microprocessor 60 uses its own timer / counter 62 from the waveform generators 48 and 58. PTT is calculated by calculating the time difference between the clock rising point of the output ECG and the clock rising point of the PPG.

As described above, the first embodiment of the present invention does not require fast A / D conversion, feature extraction from ECG and PPG signals, and complicated calculations for PTT calculation. It can be seen that the calculation is made.

Therefore, when transmitting the result of the PTT measurement, the amount of data is drastically reduced compared to the conventional system, and the high resolution PTT calculation is possible according to the speed of the timer and the counter.

5 is a block diagram of a PTT detection system according to a second embodiment of the present invention.

Referring to FIG. 5, an ECG electrode 40, a PPG sensor 50, an ECG detection circuit 42, a PPG detection circuit 52, a differentiator 44, 54, a comparator 46, 56, and a waveform generator ( 48, 58 and flip-flop 70, respectively. At this time, the ECG electrode 40 detects the ECG and outputs an electrical signal. In general, an Ag-AgCl electrode is used. The ECG detection circuit 42 amplifies and filters the electrical signal detected by the ECG electrode 40. Since the ECG detection circuit 42 and the PPG detection circuit 52 described later are described in detail in the first embodiment, the description thereof will be omitted here.

The PPG sensor 50 detects PPG and outputs an electrical signal. The PPG sensor 50 is composed of a near-infrared LED and a photodiode to detect a current according to the amount of reflected light corresponding to the amount of oxidized hemoglobin according to the volume change in the peripheral blood vessel of the finger. do. The PPG detection circuit 52 amplifies and filters the electrical signal detected by the PPG sensor 50. Each differential 44,54 consists of analog differential circuits and differentiates ECG and PPG signals to remove the baselines included in the ECG and PPG signals, and the characteristic part of which the slope of the ECG and PPG signals changes rapidly (R of ECG). Wave portion, rising portion of PPG). The comparators 46 and 56 compare the differentiated ECG values or PPG values with the set values set in the comparators 46 and 56 themselves to output waveforms at peak and feature points from the differentiated ECG and PPG signals. If the value or the PPG value is large, 1 is outputted, and if the value is small, 0 is outputted to detect peak values and feature points from the differentiated ECG and PPG (see FIGS. 6 and 7). The waveform generators 48 and 58 generate a clock for a predetermined time using the monostable oscillator when the peak value and the feature point are detected through the comparators 46 and 56.

In the second embodiment, in order to output the time difference PTT between the peak value generated by the ECG signal and the feature point generated by the PPG signal with a pulse width, the input conditions of the set terminal and the reset terminal are determined and output at the input point of the clock clk. Flip-flop 70 is used to hold the value until the next clock input. At this time, the flip-flop 70 operates by the clock input of the ECG waveform, outputs the output Q to 1 when the ECG peak value (R peak) occurs, and forces the output Q to 0 when the PPG feature point occurs. Reset it. That is, the output Q of the flip-flop 70 maintains an output of 1 only between the R wave of the ECG and the feature point of the PPG, so that the PTT can be automatically calculated by calculating the output width of the flip-flop 70.

In the configuration of this second embodiment, the ECG is detected using the ECG electrode 40 and the ECG detection circuit 42, while the PPG is detected using the PPG sensor 50 and the PPG detection circuit 52, and the differential powder 44 54) removes the baseline included in the ECG and PPG signals by differentiating the ECG and PPG signals, and highlights the characteristic portions (the R wave portion of the ECG and the rising portion of the pulse wave) in which the slope of the ECG and PPG signals changes rapidly. Let's do it.

Next, the comparators 46 and 56 detect peaks and feature points from the differentiated ECGs and PPGs by comparing the differentiated ECG values or PPG values with the set values set in the comparators 46 and 56, and the waveform generators 48 and 58. ) Generates a clock for a predetermined time when the peak value and the specific point are detected through the comparators 46 and 56. The flip-flop 70 outputs the output Q to 1 when the ECG peak value (R peak) occurs, and forcibly resets the output Q to 0 when the PPG feature point occurs, thereby outputting the output width of the flip-flop 70. Calculate PTT by calculating

As described above, the second embodiment of the present invention does not require fast A / D conversion, feature extraction from ECG and PPG signals, and complicated calculations for PTT calculation, but only the pulse width itself of the flip-flop 70. Has a PTT value, making PTT measurement very easy.

Although the above description refers to one preferred embodiment of the present invention, this is merely exemplary, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible. Such changes are within the same or equivalent ranges as those described in the claims of the present invention.

1 is a block diagram of a conventional PTT system,

2 is a block diagram of a PTT detection system according to a first embodiment of the present invention;

3 is a detailed block diagram of the ECG detection circuit shown in FIG. 2;

4 is a detailed block diagram of the PPG detection circuit shown in FIG.

5 is a block diagram of a PTT detection system according to a second embodiment of the present invention;

6 is a graph showing the results of ECG and ECG peak detection according to the present invention;

7 is a graph showing the PPG and PPG feature detection results according to the present invention,

8 is a graph illustrating calculating PTT from ECG peaks and PPG features in accordance with the present invention.

* Description of the symbols for the main parts of the drawings *

40: ECG electrode 42: ECG detection circuit

44,54: Differential 46,56: Comparator

48,58: waveform generator 50: PPG sensor

52: PPG detection circuit 60: microprocessor

62: timer / counter 70: flip-flop

Claims (9)

An ECG electrode and ECG detection circuit for detecting ECG (ECG) and a PPG sensor and PPG detection circuit for detecting PPG (photoelectric pulse wave); A differentiator for differentiating the ECG and PPG signals, respectively, to highlight a feature portion in which slopes of the ECG and PPG signals change abruptly; The differential ECG value and the PPG value are compared with the preset values, respectively, and output 1 when the ECG value or the PPG value is large, and output 0 when the value is small to detect the peak value and the characteristic point from the differential ECG and PPG value. Comparator; A waveform generator for generating a clock for a predetermined time when the peak value and the feature point are detected through the comparator: Pulse wave propagation time measurement system including a microprocessor that calculates the pulse wave propagation time (PTT) by calculating the time difference between the clock rise point of the ECG and the clock rise point of the PPG output from the waveform generator using a self-equipped timer / counter. . An ECG electrode and ECG detection circuit for detecting ECG (ECG) and a PPG sensor and PPG detection circuit for detecting PPG (photoelectric pulse wave); A differentiator for differentiating the ECG and PPG signals to obtain a feature portion in which the slopes of the ECG and PPG signals change abruptly; The differential ECG value and the PPG value are compared with the preset values, respectively, and output 1 when the ECG value or the PPG value is large, and output 0 when the value is small to detect the peak value and the characteristic point from the differential ECG and PPG value. Comparator; A waveform generator for generating a clock for a predetermined time when the peak value and the feature point are detected through the comparator: A flip that operates by a clock input of an ECG waveform output from the waveform generator, outputs an output Q differently depending on whether an ECG peak value or a PPG feature point is generated and calculates a PTT (pulse wave propagation time) according to the output width. Pulse wave propagation time measurement system including a flop. The method of claim 2, The flip-flop outputs the output Q to 1 when the ECG peak value occurs, and forcibly reset the output Q to 0 when the PPG feature point occurs. The method according to claim 1 or 2, The differential is a pulse wave propagation time measurement system, characterized in that consisting of an analog differential circuit. The method according to claim 1 or 2, The waveform generating unit pulse generation time measurement system, characterized in that for generating a clock for each predetermined time using a monostable generator. A first step of extracting feature information necessary for PTT calculation from signals of ECG and PPG through an analog signal processing circuit; And a second step of calculating the PTT by outputting the information corresponding to the PTT in the width of the waveform. The method of claim 6, The first step is to obtain a feature that the slope of the ECG and PPG signal changes rapidly by differentiating the ECG and PPG signal using an analog differential circuit, Detecting the ECG peak value and the PPG characteristic point from the differentiated ECG and PPG by comparing the differentiated ECG value and the PPG value with a set value set in the comparator. The method of claim 7, wherein In the second step, when the peak value and the feature point are detected in the first step, generating a clock for a predetermined time and outputting an ECG waveform and a PPG waveform; Calculating a PTT by calculating a time difference between the clock rising point of the output ECG waveform and the clock rising point of the PPG waveform. The method of claim 7, wherein In the second step, when the peak value and the feature point are detected in the first step, generating a clock for a predetermined time and outputting an ECG waveform and a PPG waveform; Calculating the PTT according to the output width by varying the output when the ECG peak value and the PPG feature point are generated.

Images