CN115153469B - Human body multi-parameter monitoring device based on self-mixing interference and micro-nano optical fiber - Google Patents
Human body multi-parameter monitoring device based on self-mixing interference and micro-nano optical fiber Download PDFInfo
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- 239000013307 optical fiber Substances 0.000 title claims abstract description 59
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Abstract
A human body multi-parameter monitoring device based on self-mixing interference and micro-nano optical fibers relates to the technical field of optical measurement and aims to solve the problems of high cost, poor accuracy and difficult realization of the existing optical pulse and blood pressure monitoring device. The device comprises a sensing diaphragm, a laser, a light splitting element, a photoelectric detector, a data acquisition card, a signal processing unit and a blood pressure calculating unit; the sensing diaphragm is used for collecting pulse information; the laser is used for emitting an output optical signal, and the output optical signal is returned by the sensing diaphragm and carries pulse information and then generates a self-mixing interference signal with the original light field; the photoelectric detector is used for converting the optical signals into continuous analog signals and sending the continuous analog signals to the data acquisition card; the data acquisition card is used for converting the analog signals into digital signals and transmitting the digital signals to the signal processing unit; the signal processing unit is used for processing the digital signals to obtain pulse wave information, and the blood pressure calculating unit is used for calculating the blood pressure value of the human body. The device provided by the invention is a human body multi-parameter monitoring device with good application prospect.
Description
Technical Field
The invention relates to the technical field of optical measurement, in particular to a human body multi-parameter monitoring device based on self-mixing interference and micro-nano optical fibers.
Background
With the continuous improvement of the living standard and the change of the dietary structure of people, the threat of cardiovascular and cerebrovascular diseases to human health is increasingly serious, and the self-management of health conditions and the prevention of diseases by continuously monitoring pulse information and blood pressure in daily life is becoming more important. Therefore, the continuous monitoring of pulse wave and blood pressure has important clinical value for preventing and diagnosing the cardiovascular and cerebrovascular diseases in daily life. The traditional measuring device adopts a mercury sphygmomanometer and an electronic sphygmomanometer, and the mercury sphygmomanometer is used for monitoring blood pressure and pulse, because of artificial hearing and visual errors, the numerical value is required to be measured by means of personal experience, the requirement on an operator is high, and the mercury sphygmomanometer is generally a doctor or an experienced nurse and is not suitable for common people to measure by themselves; the electronic sphygmomanometer is more convenient to use, but the electronic sphygmomanometer is also required to be worn with a sleeve for intermittent inflation, so that the operation of measurement is inconvenient.
At present, photon sensing technology is applied to monitoring human blood pressure and pulse to be concerned by researchers, however, the device obtained by research at the present stage has the problems of high development cost, poor accuracy, lack of comfort, difficulty in realization and the like, and even has potential safety hazards due to the problems of poor bending and ductility of the used materials, lack of elasticity, easiness in breakage and the like, so that development of an optical human blood pressure and pulse detection device with low cost, high accuracy, comfort and feasibility is needed.
Disclosure of Invention
The invention aims to solve the technical problems that:
the existing optical pulse and blood pressure monitoring device has the problems of high cost, poor accuracy and difficult realization.
The invention adopts the technical scheme for solving the technical problems:
The invention provides a human body multi-parameter monitoring device based on self-mixing interference and micro-nano optical fibers, which comprises a sensing diaphragm, a laser, a photoelectric detector, a data acquisition card, a signal processing unit and a blood pressure calculation unit, wherein the sensing diaphragm is arranged on the sensing diaphragm;
The sensing diaphragm comprises a micro-nano optical fiber and a flexible diaphragm, wherein the micro-nano optical fiber is embedded in the flexible diaphragm, the sensing diaphragm is used for collecting pulse information, and the flexible diaphragm is deformed due to pulse vibration so that the refraction slope of the micro-nano optical fiber is changed;
the laser is connected with one end of the micro-nano optical fiber through an optical fiber, the other end of the micro-nano optical fiber is provided with a reflecting end, the laser can emit an output optical signal with a certain wavelength under the action of driving current, the output optical signal passes through a pulse vibration part and is reflected by the reflecting end, and the optical signal carrying pulse information returns to a laser resonant cavity to generate a self-mixing interference signal with an original optical field;
The photoelectric detector is arranged in the laser and is used for converting the self-mixing interference signal into a continuous analog signal and transmitting the continuous analog signal to the data acquisition card;
The data acquisition card is connected with the photoelectric detector, is a USB dynamic signal acquisition card and is used for converting a received analog signal into a digital signal and transmitting the digital signal to the signal processing unit;
the signal processing unit is used for processing the received digital signals to obtain pulse wave information and transmitting the pulse wave information to the blood pressure calculation unit;
The blood pressure calculation unit is used for calculating the blood pressure value of the human body according to the pulse wave information.
Further, the micro-nano optical fiber is a biconical micro-nano optical fiber, the lengths of conical areas at two ends of the biconical micro-nano optical fiber are 15mm, the lengths of waist areas are 12mm, and the diameters of the waist areas are 1.8 mu m.
Further, the flexible membrane is a polydimethylsiloxane membrane.
Further, the sensing diaphragm has a length of 7.5cm and a width of 2.2cm.
Further, the implementation process of embedding the micro-nano optical fiber in the flexible membrane comprises the following steps: and (3) laying a proper amount of degassed polydimethylsiloxane on a glass slide with a certain size, embedding the micro-nano optical fiber into the polydimethylsiloxane, curing the polydimethylsiloxane to form a membrane, and taking the membrane off the glass slide, namely embedding the micro-nano optical fiber into the flexible membrane.
Further, the curing treatment condition is heating at 80 ℃ for 20 minutes.
Further, the preparation method of the biconical micro-nano optical fiber comprises the step of preparing the biconical micro-nano optical fiber by a cone drawing machine through a fusion drawing method.
Further, the signal processing unit is configured to process the received digital signal to obtain pulse wave information, and the specific implementation process is as follows: and processing the digital signals through LabVIEW software to obtain a pulse waveform chart, and simultaneously converting the pulse waveform chart into a pulse spectrogram through Fourier transformation to obtain pulse waveform information and frequency information.
Further, the blood pressure calculating unit is used for calculating the blood pressure value of the human body according to the pulse wave information, and the specific implementation process is as follows:
Determining a time span from a main peak value to a heavy vibration peak value according to a pulse spectrogram, wherein the time span is expressed as pulse transmission time PTT, and the relationship between the pulse transmission time PTT and pulse wave velocity PWV is as follows:
Wherein L represents the length of the blood vessel through which the pulse wave passes;
According to Brawell-hill equation, the pulse wave velocity PWV can be expressed by the blood density ρ and the arterial blood volume v, specifically:
Where V is the intra-arterial blood volume, dV is the amount of change in intra-arterial blood volume, dP is the blood pressure difference between the systolic pressure SBP and the diastolic pressure DBP, in mmHg, dP can be expressed as:
dP＝SBP-DBP (3)
The pulse wave velocity PWV can be expressed as:
from equation (1) and equation (4), it is possible to obtain:
On the other hand, the pulse wave velocity PWV can be expressed by the Moens-korteweg equation:
Wherein E in is the arterial elastic modulus, h is the arterial thickness, r is the arterial radius, ρ is the blood density;
as the mean blood pressure MBP increases, the elastic modulus of the artery increases exponentially, and the elastic modulus of the artery can be expressed as:
Ein＝E0eα*MBP (7)
wherein E 0 is Young's modulus of a blood vessel wall when the blood pressure value is 0, and alpha is a specific parameter related to a human blood vessel;
the following are obtained by formulas (1), (6) and (7):
and mean blood pressure MBP can be expressed as:
Then it is possible to obtain:
the relationship between systolic and diastolic blood pressure and time delay can be obtained according to formulas (5), (10) as:
wherein H a、Hb、Hc、Ja、Jb、Jc is a coefficient associated with the individual, respectively; the correlation coefficient can be obtained by detecting pulse transmission time of a large number of individuals, comparing the obtained value with the blood pressure result measured by a standard blood pressure meter and then fitting the data.
Further, the specific process of determining the coefficient H a、Hb、Hc、Ja、Jb、Jc is: collecting a plurality of adult blood pressure data without hypertension heart disease history, and taking a commercial wristband sphygmomanometer as a reference standard; synchronously collecting blood pressure and pulse information of a subject by the monitoring device and the commercial wristband sphygmomanometer according to claim 1, wherein the pulse waveform collected by the monitoring device at least comprises 10 pulse periods, an average value of pulse transmission time is obtained as a final PTT value, a nonlinear least square method is adopted to fit a PTT-BP curve, reference values are obtained by fitting, and the values of the obtained coefficients are respectively:
Ha＝370.12、Hb＝17.73、Hc＝358.46、Ja＝192.30、Jb＝9.13、Jc＝196.99.
compared with the prior art, the invention has the beneficial effects that:
The human body multi-parameter monitoring device based on self-mixing interference and the micro-nano optical fiber, disclosed by the invention, captures pulse vibration signals by using the sensing diaphragm embedded with the micro-nano optical fiber, captures the pulse vibration signals by utilizing the deformation of the waveguide structure caused by the bending deformation of the micro-nano optical fiber, and has higher sensitivity; by using the self-mixing interference technology of laser, pulse information is monitored through self-mixing interference signals, and blood pressure is further calculated through the pulse information, so that accurate pulse information and blood pressure measurement results can be obtained, and convenience is provided for accurately monitoring the pulse and blood pressure of a human body.
The device comprehensively considers the influences of blood density, arterial radius, arterial thickness, arterial blood volume and arterial elasticity on the physiological factors of each blood vessel in the calculation of the blood pressure, respectively obtains a nonlinear relation model between the systolic pressure, the diastolic pressure and the pulse transmission time, and can accurately measure the systolic pressure and the diastolic pressure through the pulse transmission time.
The device has the advantages of high accuracy, simple structure, good comfort, low cost and convenient measurement, and is a pulse and blood pressure monitoring device with good application prospect.
Drawings
FIG. 1 is a schematic diagram of a human blood pressure monitoring device based on self-mixing interference and micro-nano optical fibers in an embodiment of the invention;
FIG. 2 is a schematic structural diagram of a sensing diaphragm and a photograph of the sensing diaphragm after light with a wavelength of 650nm is introduced in an embodiment of the present invention;
FIG. 3 is a graph showing electric field intensity distribution corresponding to micro-nano optical fibers with different bending states according to an embodiment of the present invention;
FIG. 4 is a chart showing a Fourier transform of pulse waves, wherein (a) is a pulse waveform, (b) is a partial pulse waveform, and (c) is a pulse chart obtained by Fourier transform;
FIG. 5 is a graph of SBP and DBP versus PTT, and a Bland-Altman graph of SBP and DBP, where (a) is a graph of SBP versus PTT, (b) is a graph of DBP versus PTT, (c) is a Bland-Altman graph of SBP, and (d) is a Bland-Altman graph of DBP, according to an embodiment of the present invention;
FIG. 6 is a graph of SBP and DBP measurements taken by a subject during a day in accordance with an embodiment of the present invention;
fig. 7 is a waveform diagram of a finger pulse and a spectrum diagram after fourier transform in an embodiment of the invention.
Detailed Description
In the description of the present invention, it should be noted that the terms "first," "second," and "third" mentioned in the embodiments of the present invention are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first", "a second", or a third "may explicitly or implicitly include one or more such feature.
In order that the above objects, features and advantages of the invention will be readily understood, a more particular description of the invention will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings.
As shown in FIG. 1, the invention provides a human body multi-parameter monitoring device based on self-mixing interference and micro-nano optical fibers, which comprises a sensing diaphragm, a laser, a photoelectric detector, a data acquisition card, a signal processing unit and a blood pressure calculation unit; the model of the laser is S1FC1550PM, THORLABS, the output wavelength of light is 1550nm, the output power of the laser is 2mW, and the model of the data acquisition card is USB-4431, NI;
The sensing diaphragm comprises a micro-nano optical fiber and a flexible diaphragm, wherein the micro-nano optical fiber is embedded in the flexible diaphragm, the sensing diaphragm is used for collecting pulse information, and the flexible diaphragm is deformed due to pulse vibration so that the refraction slope of the micro-nano optical fiber is changed;
the laser is connected with one end of the micro-nano optical fiber through an optical fiber, the other end of the micro-nano optical fiber is provided with a reflecting end, the laser can emit an output optical signal with a certain wavelength under the action of driving current, the output optical signal passes through a pulse vibration part and is reflected by the reflecting end, and the optical signal carrying pulse information returns to a laser resonant cavity to generate a self-mixing interference signal with an original optical field;
The photoelectric detector is arranged in the laser and is used for converting the self-mixing interference signal into a continuous analog signal and transmitting the continuous analog signal to the data acquisition card;
The data acquisition card is connected with the photoelectric detector, is a USB dynamic signal acquisition card and is used for converting a received analog signal into a digital signal and transmitting the digital signal to the signal processing unit;
the signal processing unit is used for processing the received digital signals to obtain pulse wave information and transmitting the pulse wave information to the blood pressure calculation unit;
The blood pressure calculation unit is used for calculating the blood pressure value of the human body according to the pulse wave information.
As shown in fig. 2, the manufacturing process of the sensing diaphragm is as follows: stretching a standard single-mode fiber (the cladding diameter is 125um, the core diameter is 9 um) into a double-cone micro-nano fiber by a fused drawing method through a cone drawing machine to obtain the micro-nano fiber with the cone area length at both ends of 15mm, the waist area length of 12mm and the waist area diameter of 1.8 um; the preparation of the flexible membrane is to select Kang Ninggui rubber, mix Polydimethylsiloxane (PDMS) and curing agent according to the mass ratio of 10:1, degas it by means of vacuum pump, lay the mixed liquid of polydimethylsiloxane with appropriate degassing on the slide with length of 7.5cm and width of 2.2cm, embed the drawn micro-nano optical fiber into the mixed liquid of polydimethylsiloxane, cure for 20 minutes at 80 deg.C, form the membrane, then take it off the slide, get the sensing membrane with length of 7.5cm, width of 2.2cm and thickness of 0.3 mm.
As shown in FIG. 3, the electric field intensity distribution at the bending of the micro-nano optical fiber having a waist diameter of 1.8 μm at a wavelength of 1550nm has bending radii of 60 μm, 30 μm and 10 μm, respectively. It is evident that as the bend radius of the fiber gets smaller, the more pronounced the well-confined guided mode leakage, the more gradually the transition to an asymmetric radiation mode, and the greater the energy loss of the laser.
The refractive index (RI=1.40) of the PDMS flexible membrane of the sensing membrane is lower than that of the micro-nano optical fiber (RI=1.46), the flexible membrane encapsulates and protects the micro-nano optical fiber, the micro-nano optical fiber can be effectively wrapped, an evanescent field is isolated, and high mechanical flexibility and low optical loss of the micro-nano optical fiber are guaranteed.
Compared with a membrane with a sandwich structure, the sensing membrane prepared by the method can avoid the influence of bubbles generated in the membrane on the detection result. The sensing membrane has the advantages of good biocompatibility, corrosion resistance, capability of being tightly attached to the surface of the skin to eliminate air gaps and high sensitivity.
As shown in fig. 4, the signal processing unit processes the received digital signal to obtain pulse wave information, and the specific implementation process is as follows: and processing the digital signals through LabVIEW software to obtain a pulse waveform chart, and simultaneously converting the pulse waveform chart into a pulse spectrogram through Fourier transformation to obtain pulse waveform information and frequency information.
The blood pressure calculating unit calculates the blood pressure value of the human body according to the pulse wave information, and the specific implementation process is as follows:
Determining the time span from the main peak value to the heavy vibration wave peak value according to the pulse spectrogram, wherein the time span is expressed as pulse transmission time PTT; the relationship between the pulse transmission time PTT and the pulse wave velocity PWV is:
Wherein L represents the length of the blood vessel through which the pulse wave passes;
According to Brawell-hill equation, the pulse wave velocity PWV can be expressed by the blood density ρ and the arterial blood volume v, specifically:
Where V is the intra-arterial blood volume, dV is the amount of change in intra-arterial blood volume, dP is the blood pressure difference between the systolic pressure SBP and the diastolic pressure DBP, in mmHg, dP can be expressed as:
dP＝SBP-DBP (3)
The pulse wave velocity PWV can be expressed as:
from equation (1) and equation (4), it is possible to obtain:
On the other hand, the pulse wave velocity PWV can be expressed by the Moens-korteweg equation:
Wherein E in is the arterial elastic modulus, h is the arterial thickness, r is the arterial radius, ρ is the blood density;
as the mean blood pressure MBP increases, the elastic modulus of the artery increases exponentially, and the elastic modulus of the artery can be expressed as:
Ein＝E0eα*MBP (7)
wherein E 0 is Young's modulus of a blood vessel wall when the blood pressure value is 0, and alpha is a specific parameter related to a human blood vessel;
the following are obtained by formulas (1), (6) and (7):
and mean blood pressure MBP can be expressed as:
Then it is possible to obtain:
the relationship between systolic and diastolic blood pressure and time delay can be obtained according to formulas (5), (10) as:
wherein H a、Hb、Hc、Ja、Jb、Jc is a coefficient associated with the individual, respectively; the correlation coefficient can be obtained by detecting pulse transmission time of a large number of individuals, comparing the obtained value with the blood pressure result measured by a standard blood pressure meter and then fitting the data.
The specific process for determining the coefficient H a、Hb、Hc、Ja、Jb、Jc is as follows: collecting a plurality of adult blood pressure data without hypertension heart disease history, and taking a commercial wristband sphygmomanometer as a reference standard; synchronously collecting blood pressure and pulse information of a subject by the monitoring device and the commercial wristband sphygmomanometer according to claim 1, wherein the pulse waveform collected by the monitoring device at least comprises 10 pulse periods, an average value of pulse transmission time is obtained as a final PTT value, a nonlinear least square method is adopted to fit a PTT-BP curve, reference values are obtained by fitting, and the values of the obtained coefficients are respectively:
Ha＝370.12、Hb＝17.73、Hc＝358.46、Ja＝192.30、Jb＝9.13、Jc＝196.99.
The calculation models of the systolic pressure and the diastolic pressure are constructed as follows:
the performance evaluation of the blood pressure measuring device of the invention:
As shown in table 1, 18 subjects were selected for blood pressure measurement, and for each subject, blood pressure was measured using the apparatus of the present embodiment while accuracy was verified using an ohmmeter, and table 1 includes reference values and deviation values of pulse wave time delay PTT(s), systolic blood pressure SBP (mmHg), diastolic blood pressure DBP (mmHg), pulse wave frequency HR (bpm), and an ohmmeter.
The device performance prediction index is based on the MEAN absolute error (Mean Absolute Deviation, MEAN) and standard deviation (Standard Deviation, SD).
TABLE 1
The average absolute error and the average standard deviation are respectively calculated as follows: mean SBP＝-0.222、MeanDBP＝-1.056、SDSBP＝2.636、SDDBP =2.198, and the results are within acceptable ranges, so that the accuracy requirements of people on the blood pressure measuring device can be met, and meanwhile, the reliability of the device is proved.
For better verification of the system test results, as shown in fig. 5 (a) and5 (b), graphs of SBP and DBP versus PTT are shown, respectively, and it can be seen that the measured values of 18 subjects have a high correlation with the graphs; as shown in FIGS. 5 (c) and5 (d), blood pressure of all the testers was analyzed using Bland-Altman consistency analysis, wherein the 95% confidence interval of SBP was-5.457-4.823mmHg and the 95% confidence interval of DBP was-5.651-3.105 mmHg; it can be seen that the measurements of both SBP and DBP are within the 95% confidence test, which also demonstrates the strong agreement between the two, further verifying the reliability of the device of the present invention.
As shown in fig. 6, to verify the accuracy of the device of the present invention for monitoring blood pressure fluctuations multiple times a day, the device of the present invention was used to measure the blood pressure of the subject for 2 minutes every two hours during the day, and the ohmmeter was used to measure the blood pressure of the subject as a reference value for 8 times; the blood pressure change trend of the subject can be clearly seen to be similar to the trend of the reference value, and the device can accurately monitor the blood pressure for a plurality of times in a period of time, so that a foundation is laid for further research of the device for monitoring the blood pressure in the wearable portable real-time blood pressure.
To further verify the performance of the device of the present invention to measure blood pressure, blood pressure was measured for ten consecutive days on the subject. The measurement time is 8 to 9 pm, and the blood pressure of the subject is measured by an ohm-dragon sphygmomanometer as a reference value. As shown in table 2, the measurement results and the measurement errors with reference blood pressure of a subject for ten days are shown. It can be seen from table 2 that the measurement errors were not large, and were within an acceptable range.
TABLE 2
As shown in FIG. 7, when the sensor is placed on the tip of an index finger, the pulse of the tip can be detected, and the fact that the heavy vibration wave in the obtained waveform result is not obvious enough can be seen, so that the sensitivity of the sensor is improved by using a micro-nano optical fiber with smaller diameter and a thinner PDMS membrane, and the high-quality signal acquisition of the finger pulse is realized.
Although the present disclosure is disclosed above, the scope of the present disclosure is not limited thereto. Various changes and modifications may be made by one skilled in the art without departing from the spirit and scope of the disclosure, and such changes and modifications would be within the scope of the disclosure.
Claims (8)
1. The human body multi-parameter monitoring device based on the self-mixing interference and the micro-nano optical fiber is characterized by comprising a sensing diaphragm, a laser, a photoelectric detector, a data acquisition card, a signal processing unit and a blood pressure calculation unit;
The sensing diaphragm comprises a micro-nano optical fiber and a flexible diaphragm, wherein the micro-nano optical fiber is embedded in the flexible diaphragm, the sensing diaphragm is used for collecting pulse information, and the flexible diaphragm is deformed due to pulse vibration so that the refraction slope of the micro-nano optical fiber is changed;
the laser is connected with one end of the micro-nano optical fiber through an optical fiber, the other end of the micro-nano optical fiber is provided with a reflecting end, the laser can emit an output optical signal with a certain wavelength under the action of driving current, the output optical signal passes through a pulse vibration part and is reflected by the reflecting end, and the optical signal carrying pulse information returns to a laser resonant cavity to generate a self-mixing interference signal with an original optical field;
The photoelectric detector is arranged in the laser and is used for converting the self-mixing interference signal into a continuous analog signal and transmitting the continuous analog signal to the data acquisition card;
The data acquisition card is connected with the photoelectric detector, is a USB dynamic signal acquisition card and is used for converting a received analog signal into a digital signal and transmitting the digital signal to the signal processing unit;
the signal processing unit is used for processing the received digital signals to obtain pulse wave information and transmitting the pulse wave information to the blood pressure calculation unit;
the blood pressure calculation unit is used for calculating the blood pressure value of the human body according to the pulse wave information;
The micro-nano optical fiber is a biconical micro-nano optical fiber, the lengths of conical areas at two ends of the biconical micro-nano optical fiber are 15mm, the lengths of waist areas are 12mm, and the diameters of the waist areas are 1.8 mu m;
the micro-nano optical fiber is embedded in the flexible membrane, and the specific implementation process is as follows: and (3) laying a proper amount of degassed polydimethylsiloxane on a glass slide with a certain size, embedding the micro-nano optical fiber into the polydimethylsiloxane, curing the polydimethylsiloxane to form a membrane, and taking the membrane off the glass slide, namely embedding the micro-nano optical fiber into the flexible membrane.
2. The human body multi-parameter monitoring device based on self-mixing interference and micro-nano optical fiber according to claim 1, wherein the flexible membrane is a polydimethylsiloxane membrane.
3. The human body multi-parameter monitoring device based on self-mixing interference and micro-nano optical fiber according to claim 2, wherein the sensing diaphragm is 7.5cm in length and 2.2cm in width.
4. The human body multi-parameter monitoring device based on self-mixing interference and micro-nano optical fiber according to claim 3, wherein the curing treatment condition is heating at 80 ℃ for 20 minutes.
5. The human body multi-parameter monitoring device based on self-mixing interference and micro-nano optical fiber according to claim 4, wherein the preparation method of the biconic micro-nano optical fiber is that a fusion drawing method is adopted for preparation through a cone drawing machine.
6. The human body multi-parameter monitoring device based on self-mixing interference and micro-nano optical fiber according to claim 1, wherein the signal processing unit is used for processing the received digital signal to obtain pulse wave information, and the specific implementation process is as follows: and processing the digital signals through LabVIEW software to obtain a pulse waveform chart, and simultaneously converting the pulse waveform chart into a pulse spectrogram through Fourier transformation to obtain pulse waveform information and frequency information.
7. The human body multi-parameter monitoring device based on self-mixing interference and micro-nano optical fiber according to claim 6, wherein the blood pressure calculating unit is used for calculating the human body blood pressure value according to pulse wave information, and the specific implementation process is as follows:
Determining the time span from the main peak value to the heavy vibration wave peak value according to the pulse spectrogram, wherein the time span is expressed as pulse transmission time PTT; the relationship between the pulse transmission time PTT and the pulse wave velocity PWV is:
Wherein L represents the length of the blood vessel through which the pulse wave passes;
According to Brawell-hill equation, the pulse wave velocity PWV can be expressed by the blood density ρ and the arterial blood volume v, specifically:
Where V is the intra-arterial blood volume, dV is the amount of change in intra-arterial blood volume, dP is the blood pressure difference between the systolic pressure SBP and the diastolic pressure DBP, in mmHg, dP can be expressed as:
dP＝SBP-DBP (3)
The pulse wave velocity PWV can be expressed as:
from equation (1) and equation (4), it is possible to obtain:
On the other hand, the pulse wave velocity PWV can be expressed by the Moens-korteweg equation:
Wherein E in is the arterial elastic modulus, h is the arterial thickness, r is the arterial radius, ρ is the blood density;
as the mean blood pressure MBP increases, the elastic modulus of the artery increases exponentially, and the elastic modulus of the artery can be expressed as:
Ein＝E0eα*MBP (7)
wherein E 0 is Young's modulus of a blood vessel wall when the blood pressure value is 0, and alpha is a specific parameter related to a human blood vessel;
the following are obtained by formulas (1), (6) and (7):
and mean blood pressure MBP can be expressed as:
Then it is possible to obtain:
the relationship between systolic and diastolic blood pressure and time delay can be obtained according to formulas (5), (10) as:
wherein H a、Hb、Hc、Ja、Jb、Jc is a coefficient associated with the individual, respectively; the correlation coefficient can be obtained by detecting pulse transmission time of a large number of individuals, comparing the obtained value with the blood pressure result measured by a standard blood pressure meter and then fitting the data.
8. The human body multi-parameter monitoring device based on self-mixing interference and micro-nano optical fiber according to claim 7, wherein the specific process of determining the coefficient H a、Hb、Hc、Ja、Jb、Jc is: collecting a plurality of adult blood pressure data without hypertension heart disease history, and taking a commercial wristband sphygmomanometer as a reference standard; synchronously collecting blood pressure and pulse information of a subject by the monitoring device and the commercial wristband sphygmomanometer according to claim 5, wherein the pulse waveform collected by the monitoring device at least comprises 10 pulse periods, an average value of pulse transmission time is obtained as a final PTT value, a nonlinear least square method is adopted to fit a PTT-BP curve, reference values are obtained by fitting, and the values of the obtained coefficients are respectively:
Ha＝370.12、Hb＝17.73、Hc＝358.46、Ja＝192.30、Jb＝9.13、Jc＝196.99.
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