CN112587133A - Method for measuring blood oxygen saturation - Google Patents
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- 239000008280 blood Substances 0.000 title claims abstract description 44
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 title claims abstract description 43
- 210000004369 blood Anatomy 0.000 title claims abstract description 43
- 229910052760 oxygen Inorganic materials 0.000 title claims abstract description 43
- 239000001301 oxygen Substances 0.000 title claims abstract description 43
- 238000000034 method Methods 0.000 title claims abstract description 29
- 238000001914 filtration Methods 0.000 claims abstract description 31
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- 238000004364 calculation method Methods 0.000 claims abstract description 11
- 238000012935 Averaging Methods 0.000 claims description 9
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- 108010054147 Hemoglobins Proteins 0.000 description 2
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- 230000002612 cardiopulmonary effect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/145—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue
- A61B5/1455—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue using optical sensors, e.g. spectral photometrical oximeters
- A61B5/14551—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue using optical sensors, e.g. spectral photometrical oximeters for measuring blood gases
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/02—Detecting, measuring or recording pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography or electroauscultation; Heart catheters for measuring blood pressure
- A61B5/024—Detecting, measuring or recording pulse rate or heart rate
- A61B5/02416—Detecting, measuring or recording pulse rate or heart rate using photoplethysmograph signals, e.g. generated by infrared radiation
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/72—Signal processing specially adapted for physiological signals or for diagnostic purposes
- A61B5/7203—Signal processing specially adapted for physiological signals or for diagnostic purposes for noise prevention, reduction or removal
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/72—Signal processing specially adapted for physiological signals or for diagnostic purposes
- A61B5/7203—Signal processing specially adapted for physiological signals or for diagnostic purposes for noise prevention, reduction or removal
- A61B5/7207—Signal processing specially adapted for physiological signals or for diagnostic purposes for noise prevention, reduction or removal of noise induced by motion artifacts
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/72—Signal processing specially adapted for physiological signals or for diagnostic purposes
- A61B5/7225—Details of analog processing, e.g. isolation amplifier, gain or sensitivity adjustment, filtering, baseline or drift compensation
Abstract
The invention discloses a method for measuring blood oxygen saturation, which comprises the steps of collecting PPG signals of red light and infrared light by a PPG signal collecting module, eliminating noise by low-pass filtering and convolution filtering of the collected PPG signals, removing motion artifact signals existing in pulse waves by an LMS adaptive filter, detecting an effective signal period of PPG alternating current component signals by establishing a signal characteristic sequence, processing waveforms in the effective signal period to obtain alternating current components of target signals, and further utilizing a calculation formula
Calculating the R value of the blood oxygen saturation, calculating the blood oxygen saturation according to the calculated R value, and the calculation formula is SpO2＝A*R2And + B R + C, the accuracy of the detection of the blood oxygen saturation is improved.
Description
Technical Field
The invention relates to the technical field of medical detection, in particular to a method for measuring blood oxygen saturation.
Background
Blood oxygen saturation (SpO)2) Refers to the amount of oxygen in the blood of a human body, which is measured by the amount of oxygenated hemoglobin (HbO) in the blood2) The saturation of blood oxygen is calculated as the percentage of the total content of reduced hemoglobin (Hb).The blood oxygen saturation is an important physiological parameter of the cardiopulmonary function and the health degree of a circulatory system of a human body, can reflect the oxygen-containing condition in the blood of the human body, and can judge whether the respiratory tract and the circulatory system are normal or not. The devices for detecting the blood oxygen saturation on the market are very easily affected by motion artifacts, so that the detection accuracy is not high, and particularly, under the condition that the pulse wave signals have sudden changes and contain noise, the detected result is not ideal.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a method for measuring the blood oxygen saturation, which can improve the detection accuracy.
In order to solve the technical problems, the invention adopts the following technical scheme:
a method for measuring blood oxygen saturation comprises the following steps:
s10, collecting PPG signals of red light and infrared light, wherein the PPG signals comprise target signals and interference signals;
s20, performing low-pass filtering on the PPG signal to extract a direct current component to obtain a PPG direct current component signal, removing low-frequency interference in the PPG direct current component signal to obtain a direct current component of a target signal, wherein the direct current component of the target signal of the red light is SrddcThe DC component of the target signal of infrared light is Sirdc；
S30, performing band-pass filtering on the PPG signal to extract an alternating current component to obtain a PPG alternating current component signal, and performing convolution filtering on the extracted PPG alternating current component signal by using an average convolution kernel;
s40, eliminating the interference signal in the PPG alternating current component signal after convolution filtering by using an LMS adaptive filtering algorithm;
s50, detecting the effective signal period of the PPG alternating current component signal by establishing a signal characteristic sequence and correspondingly setting the effective signal period as a calibration period, and calibrating the effective wave peak point in the calibration period;
s60, finding the nearest trough point through the effective wave peak point in the calibration period, and solving the peak-trough difference value of the PPG alternating current component signal to obtain the alternating current component of the target signal, wherein the alternating current component of the red target signalAmount is SrdacThe alternating current component of the target signal of the infrared light is Sirac；
S70, calculating the R value of the blood oxygen saturation, wherein the calculation formula is
Calculating the blood oxygen saturation degree according to the calculated R value, wherein the calculation formula is SpO2＝A*R2+ B × R + C, wherein A, B, C is a value calculated by fitting from the blood oxygen values measured by the reference oximeter and the R values calculated from the corresponding signals.
The invention has the beneficial technical effects that: according to the method for measuring the blood oxygen saturation, low-pass filtering and convolution filtering are adopted to eliminate noise, an LMS adaptive filter is used for removing motion artifact signals existing in pulse waves, on the basis, the effective signal period of a PPG alternating current component signal is detected by building a signal characteristic sequence, and the alternating current component of a target signal is obtained by processing waveforms in the effective signal period, so that the accuracy of the blood oxygen saturation detection is improved.
Drawings
Fig. 1 is a schematic flow chart of a method of measuring blood oxygen saturation in one embodiment of the present invention;
FIG. 2 is a block diagram of an LMS adaptive filter architecture;
FIG. 3 is a signal waveform with motion artifacts before LMS adaptive filtering;
FIG. 4 is a signal waveform after bandpass filtering, LMS adaptive filtering;
fig. 5 is a flowchart illustrating a method for measuring blood oxygen saturation in another embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more clearly understood by those skilled in the art, the present invention is further described with reference to the accompanying drawings and examples.
As shown in fig. 1, in one embodiment of the present invention, the method for measuring blood oxygen saturation includes the following steps:
s10, collecting a PPG (Photo pulse mapping, abbreviated as PPG) signal of red light and infrared light, where the PPG signal includes a target signal and an interference signal.
Specifically, PPG signals P of red light and infrared light are respectively acquired at a sampling frequency of 32HZ, wherein the PPG signals P comprise a target signal S and an interference signal N, and the PPG signals of the red light are marked as PrdPPG signal of infrared light is denoted as PirRed light target signal is denoted as SrdInterference signal of red light is denoted as NrdThe target signal of infrared light is denoted as SirAnd the interference signal of infrared light is recorded as Nir. In this embodiment, the red light signal is a 660nm wavelength red light signal, and the infrared light signal is a 900nm wavelength infrared light signal.
S20, performing low-pass filtering on the PPG signal to extract a direct current component to obtain a PPG direct current component signal, removing low-frequency interference in the PPG direct current component signal to obtain a direct current component of a target signal, wherein the direct current component of the target signal of the red light is SrddcThe DC component of the target signal of infrared light is Sirdc。
Specifically, the step S20 further includes steps S21-S23:
and S21, performing low-pass filtering on the PPG signals of the red light and the infrared light by using a Butterworth filter, extracting a direct current component to obtain a PPG direct current component signal, wherein the cut-off frequency of the PPG signal is less than 0.5 HZ.
And S22, calculating an envelope curve of the PPG direct current component signal after low-pass filtering, calculating the mean value of the envelope curve through the upper envelope curve and the lower envelope curve, and processing the signal by using the mean value of the envelope curve to remove low-frequency noise interference in the PPG direct current component signal. The envelope curve calculation method comprises the following steps: calculating an extreme point in the signal by using a difference method, wherein a zero-crossing point of the signal subjected to difference processing corresponds to the extreme point of the PPG signal; and (4) taking the extreme point as an original data point, and expanding the data by adopting an interpolation calculation method to obtain an envelope curve of the PPG signal.
S23, calculating the direct current component of the target signal of the red light as S by using the PPG direct current component signal processed in the step S22rddcAnd the purpose of infrared lightThe DC component of the reference signal is Sirdc。
And S30, performing band-pass filtering on the PPG signal, cutting off the signal with the frequency between 0.5HZ and 4HZ, extracting the alternating current component to obtain a PPG alternating current component signal, and performing convolution filtering on the extracted PPG alternating current component signal by using an average convolution kernel to enable the waveform to be smoother.
And S40, eliminating the interference signal in the PPG alternating current component signal after convolution filtering by using an LMS adaptive filtering algorithm.
As shown in fig. 2, step S40 is mainly implemented by LMS (Least Mean Square) adaptive filtering, and performs cancellation processing on the interference signal in the alternating current component of the PPG signal by extracting the relevant reference signal. The ac component of the PPG signal pac (t) ═ p (t), p (t-1), … … p (t-k +1)]The PPG signal interference suppression device comprises a target signal alternating current component Sac (t) and an interference signal alternating current component Nac (t), and the PPG signal interference suppression device utilizes the alternating current component difference of the PPG signals of red light and infrared light as a reference signal N (t) ([ n (t), n (t-1).. n (t-k + 1))]Inputting the reference signal and PPG alternating current component signals of red light and infrared light into an adaptive filter for adaptive processing to eliminate motion interference noise, wherein the output of the processor is ytW (t) x (t), the processor outputs an error e from the ac componentT＝Pac-ytK is the length of the adaptive filtering, and W (t) is the processor coefficient. The target signal with the motion noise removed is obtained through the adaptive processing of the adaptive filter, and the effects before and after the adaptive processing are shown in fig. 3 and 4.
And S50, detecting the effective signal period of the PPG alternating current component signal by constructing a signal characteristic sequence, correspondingly setting the effective signal period as a calibration period, and calibrating the effective wave peak point in the calibration period.
The step S50 is mainly used for signal quality screening, identifying waveforms with good signal quality, and extracting effective signal periods. And forming effective signal characteristics into a signal characteristic sequence which comprises a red light signal wave peak value threshold value, a red light signal wave peak value difference threshold value, an infrared light wave peak value threshold value, an infrared light signal wave peak value difference threshold value and a corresponding periodic wave peak value interval difference between double-color light. And then detecting the effective signal period of the PPG alternating current component signal by establishing a signal characteristic sequence and correspondingly setting the effective signal period as a calibration period, and calibrating the effective peak point in the calibration period. The step S50 further includes steps S51-S54:
and S51, carrying out extreme value detection on the PPG alternating current component signals of the red light and the infrared light to obtain extreme value points of the PPG alternating current component signals of the red light and the infrared light and obtain peak value points.
Specifically, an argrlemax algorithm or other extreme values may be used to detect extreme points of PPG alternating current component signals of red light and infrared light, and then the detected extreme points are classified to obtain a peak point and a trough point, and a peak value is recorded respectively.
And S52, screening the quasi-calibration cycle and the remaining undetermined cycle of the PPG alternating current component signals of the red light and the infrared light according to the wave peak value of the PPG alternating current component signals of the red light and the infrared light.
Before step S52, threshold values of the peak values of red light and infrared light are set in advance. The setting method of the wave peak value threshold value comprises the following steps: averaging all wave peak values of PPG alternating current component signals of red light and infrared light to obtain a first average value of wave peak value points, and setting a wave peak value threshold value according to the first average value to obtain the wave peak value threshold values of the red light and the infrared light. The averaging of the peak values may be arithmetic averaging of the peak values or weighted averaging of the peak values, which is not limited in this embodiment. The setting of the peak value threshold according to the first average value may be to multiply the first average value by a predetermined peak value coefficient, which may be set according to actual needs, for example, 1.2, to obtain a product as the peak value threshold. The wave peak value threshold value comprises a first threshold value and a second threshold value, and the wave peak value predetermined coefficient comprises a first predetermined coefficient and a second predetermined coefficient corresponding to the first threshold value and the second threshold value; the first threshold is an upper limit value of a wave peak threshold range, the second threshold is a lower limit value of the wave peak threshold range, and the wave peak threshold range is determined by the first threshold and the second threshold.
The step S52 specifically includes: if the wave peak values of the PPG alternating current component signals of the red light and the infrared light are within the corresponding wave peak value threshold range, the signal quality of the period is good, and the period is set as a quasi-calibration period; if the wave peak value of the PPG alternating current component signal of one of the red light and the infrared light exceeds the corresponding wave peak value threshold value and the wave peak value of the PPG alternating current component signal of the other light is within the corresponding wave peak value threshold value range, the quality of the periodic signal is poor, and the period does not meet the calibration; and if the wave peak values of the PPG alternating current component signals of the red light and the infrared light exceed the corresponding wave peak value thresholds, reserving the period to be determined.
And S53, calculating a quasi-calibration period and keeping the wave peak point interval between the two colors of the PPG alternating current component signal in the undetermined period, if the wave peak point interval does not exceed the interval threshold range, indicating that the corresponding period belongs to the calibration period, and calibrating the wave peak point of the calibration period.
Before step S53, a threshold interval between the two colors of the PPG ac component signal is set in advance. The interval threshold comprises an interval upper limit value and an interval lower limit value, and the interval threshold range is determined by the interval upper limit value and the interval lower limit value; the interval upper limit value and the interval lower limit value can be directly set by technicians according to actual needs.
And S54, respectively carrying out primary difference operation on all wave peak values of the PPG alternating current component signals of the red light and the infrared light in the calibration period, if the wave peak values do not exceed the difference threshold range, retaining the wave peak values, and otherwise, deleting the wave peak values.
Before step S54, a difference threshold corresponding to red light or infrared light is set in advance. The setting method of the differential threshold value comprises the following steps: and carrying out primary difference operation on each wave peak value of PPG alternating current component signals of red light and infrared light to obtain a difference value, averaging the obtained difference values to obtain a third mean value, and setting a difference threshold value according to the third mean value. The averaging of the obtained difference values may be an arithmetic average of the obtained difference values or a weighted average of the obtained difference values, which is not limited in this embodiment. The setting of the difference threshold according to the third mean value may be that the third mean value is multiplied by a predetermined coefficient of a difference value, and the obtained product is used as the difference threshold, and the predetermined coefficient of the difference value may be set according to actual needs. The differential threshold value comprises a third threshold value and a fourth threshold value, and the differential value predetermined coefficient comprises a third predetermined coefficient and a fourth predetermined coefficient corresponding to the third threshold value and the fourth threshold value; the third threshold is an upper limit value of a differential threshold range, the fourth threshold is a lower limit value of the differential threshold range, and the differential threshold range is determined by the third threshold and the fourth threshold.
S60, finding the nearest trough point through the effective wave peak point in the calibration period, and solving the peak-trough difference value of the PPG alternating current component signal to obtain the alternating current component of the target signal, wherein the alternating current component of the target signal of the red light is SrdacThe alternating current component of the target signal of the infrared light is Sirac。
S70, calculating the R value of the blood oxygen saturation, wherein the calculation formula is
Calculating the blood oxygen saturation degree according to the calculated R value, wherein the calculation formula is SpO2＝A*R2+ B × R + C, wherein A, B, C is a value calculated by fitting from the blood oxygen values measured by the reference oximeter and the R values calculated from the corresponding signals.
Since the red light signal in this embodiment is the red light signal with the wavelength of 660nm, and the infrared light signal is the infrared light signal with the wavelength of 900nm, therefore,
Vac600representing the amplitude, V, of the AC component of the red signaldc600Representing the magnitude, V, of the DC component of the red signalac900Representing the amplitude, V, of the AC component of the infrared light signaldc900Representing the magnitude of the dc component of the infrared light signal.
The method for measuring the blood oxygen saturation eliminates noise by adopting low-pass filtering and convolution filtering, removes motion artifact signals existing in pulse waves by utilizing an LMS adaptive filter, detects the effective signal period of PPG alternating current component signals by establishing a signal characteristic sequence on the basis, and processes the waveform in the effective signal period to obtain the alternating current component of a target signal, thereby improving the accuracy of the blood oxygen saturation detection.
As shown in fig. 5, in another embodiment of the present invention, the step S20 is preceded by the steps of: and S11, performing windowing processing on the collected PPG signals of the red light and the infrared light. Specifically, the collected PPG signals of red light and infrared light are windowed, and the moving process is performed with 4s as a window and 2s as a step length. The windowing processing can avoid the influence of false detection caused by sudden interference on the whole data, so that the small-range processing is more accurate. In the embodiment, the window size is 4s, generally, several cycles can appear in 4s, and the several cycles can be accurately identified only by one or two effective cycles; meanwhile, due to windowing processing, the sampling rate is low, the data length is just moderate, the data length is greatly shortened relative to the whole data processing, the front-back relation can be reflected, the current characteristics can be solved more accurately, and the accuracy is improved.
As shown in fig. 5, the step S20 further includes the following steps: and S12, judging whether the user is quiet or not according to the acceleration sensing signal, if so, jumping to the step S20, and if not, directly quitting the detection.
The step S12 is mainly to detect whether the user is in a quiet state at the time of the test. Specifically, whether the user is in a quiet state is judged through signals of the acceleration sensor, and if the amplitude change of the signals of any one axis of the acceleration sensor in the time of 1S is lower than a set lower limit value, the user is considered to be in the quiet state; if the amplitude change of the signal within the time of 1S exceeds the set lower limit value but is lower than the set upper limit value, the user is considered to be in a motion state but the motion state is not severe, and the user should be prompted to keep quiet at the moment, so that the signal can be more stable; if the amplitude change of the signal within the time of 1S exceeds the set upper limit value, the user is considered to be in a violent exercise state, and the detection of the blood oxygen saturation is directly withdrawn. The accuracy of measurement can be ensured as long as the measurement of the blood oxygen saturation is performed in a state where the user remains quiet.
The foregoing is considered as illustrative of the preferred embodiments of the invention and is not to be construed as limiting the invention in any way. Various equivalent changes and modifications can be made by those skilled in the art based on the above embodiments, and all equivalent changes and modifications within the scope of the claims should fall within the protection scope of the present invention.
Claims (10)
1. A method for measuring blood oxygen saturation is characterized by comprising the following steps:
s10, collecting PPG signals of red light and infrared light, wherein the PPG signals comprise target signals and interference signals;
s20, performing low-pass filtering on the PPG signal to extract a direct current component to obtain a PPG direct current component signal, removing low-frequency interference in the PPG direct current component signal to obtain a direct current component of a target signal, wherein the direct current component of the target signal of the red light is SrddcThe DC component of the target signal of infrared light is Sirdc；
S30, performing band-pass filtering on the PPG signal to extract an alternating current component to obtain a PPG alternating current component signal, and performing convolution filtering on the extracted PPG alternating current component signal by using an average convolution kernel;
s40, eliminating the interference signal in the PPG alternating current component signal after convolution filtering by using an LMS adaptive filtering algorithm;
s50, detecting the effective signal period of the PPG alternating current component signal by establishing a signal characteristic sequence and correspondingly setting the effective signal period as a calibration period, and calibrating the effective wave peak point in the calibration period;
s60, finding the nearest trough point through the effective wave peak point in the calibration period, and solving the peak-trough difference value of the PPG alternating current component signal to obtain the alternating current component of the target signal, wherein the alternating current component of the target signal of the red light is SrdacThe alternating current component of the target signal of the infrared light is Sirac；
S70, calculating the R value of the blood oxygen saturation, wherein the calculation formula is
Calculating the blood oxygen saturation degree according to the calculated R value, wherein the calculation formula is SpO2＝A*R2+ B × R + C, wherein A, B, C is a value calculated by fitting from the blood oxygen values measured by the reference oximeter and the R values calculated from the corresponding signals.
2. The method of measuring blood oxygen saturation as set forth in claim 1, wherein said step S20 further includes the steps of:
s21, performing low-pass filtering on the PPG signal by using a Butterworth filter to extract a direct current component to obtain a PPG direct current component signal;
s22, calculating an envelope curve of the PPG direct current component signal after low-pass filtering, calculating the mean value of the envelope curve through the upper envelope curve and the lower envelope curve, and processing the signal by using the mean value of the envelope curve to remove low-frequency noise interference in the PPG direct current component signal;
s23, calculating the direct current component of the target signal of the red light as S by using the PPG direct current component signal processed in the step S22rddcAnd the DC component of the target signal of infrared light is Sirdc。
3. The method for measuring blood oxygen saturation according to claim 2, wherein the envelope is calculated by: calculating an extreme point in the signal by using a difference method, wherein a zero-crossing point of the signal subjected to difference processing corresponds to the extreme point of the PPG signal; and (4) taking the extreme point as an original data point, and expanding the data by adopting an interpolation calculation method to obtain an envelope curve of the PPG signal.
4. The method of measuring blood oxygen saturation as set forth in claim 1, wherein said step S40 further includes the steps of:
s41, using the difference between the alternating current components of the PPG signals of red and infrared light as a reference signal n (t) ([ n (t), n (t-1).. n (t-k +1) ];
s42, inputting the reference signal and PPG alternating current component signals of red light and infrared light into an adaptive filter for adaptive processing to eliminate motion interference noise, and outputting the signal ytW (t) x (t), the processor outputs an error e from the ac componentT＝Pac-ytK is the length of the adaptive filtering, and W (t) is the processor coefficient.
5. The method of measuring blood oxygen saturation as set forth in claim 1, wherein said step S50 further includes the steps of:
s51, carrying out extreme value detection on the PPG alternating current component signals of the red light and the infrared light to obtain extreme value points of the PPG alternating current component signals of the red light and the infrared light and obtain peak value points;
s52, screening the quasi-calibration cycle and the reservation undetermined cycle of the PPG alternating current component signals of the red light and the infrared light according to the wave peak value of the PPG alternating current component signals of the red light and the infrared light;
s53, calculating a quasi-calibration period and reserving the interval of the peak value points among the bicolor light of the PPG alternating current component signal in the undetermined period, if the interval does not exceed the range of the interval threshold, indicating that the corresponding period belongs to the calibration period, and calibrating the peak value points of the calibration period;
and S54, respectively carrying out primary difference operation on all wave peak values of the PPG alternating current component signals of the red light and the infrared light in the calibration period, if the wave peak values do not exceed the difference threshold range, reserving the wave peak value points, and if the wave peak values do not exceed the difference threshold range, deleting the wave peak values.
6. The method of measuring blood oxygen saturation according to claim 5, wherein said step S52 further includes the steps of:
s521, if the wave peak values of the PPG alternating-current component signals of the red light and the infrared light are within the corresponding wave peak value threshold range, the signal quality of the period is good, and the period is set as a quasi-calibration period;
s522, if the wave peak value of the PPG alternating current component signal of one of the red light and the infrared light exceeds the corresponding wave peak value threshold value and the wave peak value of the PPG alternating current component signal of the other light is within the corresponding wave peak value threshold value range, the signal quality of the period is poor, and the period does not accord with the calibration;
and S523, if the wave peak values of the PPG alternating-current component signals of the red light and the infrared light exceed the corresponding wave peak value thresholds, reserving the period to be determined.
7. The method of measuring blood oxygen saturation according to claim 6,
the setting method of the wave peak value threshold value comprises the following steps: averaging all wave peak values of the PPG alternating current component signal to obtain a first mean value of the wave peak values, and setting a wave peak value threshold value according to the first mean value;
the setting method of the interval threshold comprises the following steps: and calculating the wave peak point interval between each wave peak point of the red light signal and the wave peak point corresponding to the infrared light signal, averaging the obtained wave peak point intervals to obtain a second average value, and setting an interval threshold value according to the second average value.
8. The method of measuring blood oxygen saturation as set forth in claim 5, wherein said differential threshold value is set by: and carrying out primary difference operation on each wave peak value of the PPG alternating current component signal to obtain a difference value, averaging the obtained difference values to obtain a third mean value, and setting a difference threshold value according to the third mean value.
9. The method of measuring blood oxygen saturation according to claim 1, further comprising, before said step S20, the step of: and S11, windowing the collected PPG signals of the red light and the infrared light, wherein the window size is 4S, and the step length is 2S.
10. The method of measuring blood oxygen saturation according to claim 9, further comprising, before said step S20, the step of: and S12, judging whether the user is quiet or not according to the acceleration sensing signal, if so, jumping to the step S20, and if not, directly quitting the detection.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114403823A (en) * | 2022-01-20 | 2022-04-29 | 杭州纳境科技有限公司 | Heart rate blood oxygen detection method and device and wearable device |
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