Apparatus and method for measuring radial displacement of pulse wave and applications thereof

Abstract

A device for measuring radial displacement pulse waves and its application method are provided. The device includes a housing, an air bladder, a pressure control module, a displacement sensing module, and a computing unit. The housing has a transparent portion. The air bladder is located below the transparent portion, and the displacement sensing module is located above the transparent portion. The pressure control module controls the internal pressure of the air bladder to adjust the depth of pressure exerted by the air bladder on the subject's skin. The measurement signal from the displacement sensing module penetrates the transparent portion and the air bladder, measuring the dynamic distance between the subject's skin and the displacement sensing module caused by the pulse of an artery. The computing unit controls the pressure control module and the displacement sensing module respectively, and receives and records the dynamic distance to obtain the radial displacement pulse wave.

Description

Technical Field

[0001] This manual relates to a physiological characteristic measurement system and its usage, and in particular to a radial displacement pulse wave measurement device and its usage. Prior Technology

[0002] Pulse waves are used to assess the function and health of the cardiovascular system. Based on different measurement characteristics, pulse waves can be divided into pressure pulse waves, vascular volume pulse waves, photoplethysmography pulse waves, and radial displacement pulse waves.

[0003] The aforementioned pressure pulse wave measurement typically uses piezoelectric, strain gauge, and thin-film piezoresistive pressure sensors as the pulse wave sensor, indirectly measuring the pressure caused by blood vessel expansion. In use, the pressure sensor is placed between an air bladder and the skin. When the air bladder inflates, it compresses the blood vessel located below it. Because the pulse wave changes the blood vessel diameter, it compresses the pressure sensor and air bladder located above the blood vessel, allowing the pressure sensor to indirectly measure the blood vessel's pressure pulse wave through this change in diameter. Common problems with this method of pulse wave measurement include a small dynamic range, susceptibility to noise, complex pressure sensor calibration methods, and poor reproducibility of measurement results.

[0004] [Above] Vascular volume pulse wave measurement typically uses a cuff-shaped air bladder as the measurement tool, with the pressure of the cuff-shaped air bladder measured by a pressure sensor. During use, the cuff-shaped air bladder is placed above the blood vessel, and the air bladder is gradually inflated. The pressure change inside the air bladder is then measured using a pressure sensor. This measurement result is equivalent to integrating all changes in the diameter of all blood vessels under the air bladder and converting them into a change in pressure inside the air bladder. The problem with this method of pulse wave measurement is that when the air inside the air bladder is compressed, the details of the vascular volume pulse wave disappear, leaving only the amplitude of the vascular volume pulse wave for reference.

[0005] The aforementioned photoplethysmography (PPG) is obtained by detecting changes in the intensity of light reflected from blood vessels beneath the skin using a PPG sensor. A common problem with this method of pulse wave measurement is that the results may be affected by differences in physiological parameters of the individual measurement location (such as subcutaneous tissue thickness and tissue absorbance).

[0006] While the radial displacement pulse wave of the aforementioned blood vessels can be measured using ultrasound echo images, extensive and complex calculations and corrections are often required to obtain good image resolution and contrast in order to estimate the amount of change in the radial displacement of the blood vessels. Summary of the Invention

[0007] To address the aforementioned problems, one of the objectives of this disclosure is to provide a radial displacement pulse wave measurement device for measuring the radial displacement pulse wave of an artery in a test part of a subject. The radial displacement pulse wave measurement device includes a housing, a transparent airbag, a pressure control module, a displacement sensing module, and a computing unit.

[0008] The outer shell has a transparent portion, which includes a hole or a first transparent plate. A transparent airbag is located below the transparent portion, and the main body of the transparent airbag is made of a material that is not easily stretched or deformed. A pressure control module is used to control the internal pressure of the transparent airbag, thereby controlling the downward pressure applied by the transparent airbag to the test area to amplify the pulse signal of the artery. A displacement sensing module is located above the transparent portion and is used to sense the pulse of the artery, measure the dynamic distance between the skin of the test area and the displacement sensing module caused by the pulse of the artery, so as to obtain the radial displacement pulse wave. A computing unit is communicatively connected to the pressure control module and the displacement sensing module, respectively, and is used to transmit control signals to the pressure control module and the displacement sensing module, respectively, and to receive information transmitted from the pressure control module and the displacement sensing module and perform calculations.

[0009] According to one embodiment of this disclosure, the main material of the transparent airbag includes polymethyl methacrylate, cellulose acetate, nylon-66 polyamide resin, nylon-6 polyamide resin, polybutylene terephthalate, polyethyl terephthalate, polyphenylene oxide, polycarbonate, ethylene-vinyl acetate copolymer, polyethylene, polypropylene, polyvinyl chloride, polyacetal, or polyurethane.

[0010] According to one embodiment of the present disclosure, when the transparent portion is the hole, the transparent airbag further includes a transparent window that overlaps with the transparent portion of the outer shell, and the transparent window includes a second transparent plate.

[0011] According to one embodiment of this disclosure, the outer surface of the transparent window has an anti-reflective film.

[0012] According to one embodiment of this disclosure, the area of ​​the second transparent plate is larger than the area of ​​the hole. When the internal pressure of the transparent airbag is too high, the second transparent plate will press against the bottom of the hole and will not be squeezed to the top of the hole.

[0013] According to one embodiment of this disclosure, the transparent airbag further includes a contact portion for closely adhering to the skin of the subject's test area, and the contact portion is made of a soft and stretchable thermoplastic elastomer polymer material, which includes at least one of thermoplastic polyurethane, polyolefin elastomer, dynamically sulfurized polyolefin elastomer, polystyrene elastomer, polyether ester elastomer, polyamide elastomer, and polyvinyl chloride.

[0014] According to one embodiment of this disclosure, a reflective layer or a color separation layer is provided on the inner surface of the contact portion.

[0015] According to one embodiment of this disclosure, the radial displacement pulse wave measurement device further includes a wearable portion, in which the limb part of the subject to be measured is accommodated within the internal space of the wearable portion. The wearable portion includes a soft inner layer and a hard outer layer. The soft inner layer includes the transparent airbag. The hard outer layer is located outside the soft inner layer, forming the internal space of the wearable portion together with the soft inner layer. During the measurement of the radial displacement pulse wave, the hard outer layer maintains a fixed distance from the displacement sensing module to the furthest point on the hard outer layer from the displacement sensing module.

[0016] According to one embodiment of the present disclosure, the soft inner layer further includes a plurality of auxiliary airbags, the internal pressure of which is controlled by the pressure control module.

[0017] According to one embodiment of this disclosure, the pressure control module includes a pressure sensor and a pressure adjustment module. The pressure sensor is used to sense the internal pressure of the transparent airbag. The pressure adjustment module is used to adjust the internal pressure of the transparent airbag, and the pressure adjustment module includes a pump.

[0018] According to one embodiment of the present disclosure, the pressure adjustment module further includes a pulse width modulation circuit to adjust the speed of the pump motor.

[0019] According to one embodiment of the present disclosure, the displacement sensing module includes a transmitter and a receiver, the transmitter and the receiver being aligned with the transparent portion, and a measurement signal emitted by the transmitter can pass through the transparent portion and the transparent airbag.

[0020] According to one embodiment of the present disclosure, the displacement sensing module includes a photoelectric displacement sensor.

[0021] According to one embodiment of this disclosure, the photoelectric displacement sensor includes a laser displacement meter, a fiber optic displacement meter, a three-dimensional scanning laser displacement meter, a time-of-flight ranging device, a three-dimensional time-of-flight ranging device, a laser Doppler rangefinder, a laser Doppler velocimeter, a Michelson interferometer, or a ranging device of a laser interferometer.

[0022] According to one embodiment of this disclosure, the displacement sensing module further includes a filter.

[0023] According to one embodiment of the present disclosure, the radial displacement pulse wave measurement device further includes a scanning position control module, which is communicatively connected to the computing unit and used to control the displacement sensing module to perform distance measurement scanning in the part to be measured, wherein the scanning position control module includes a single-axis position controller or a dual-axis position controller.

[0024] Another objective of this disclosure is to provide a radial displacement pulse wave measurement device for measuring the radial displacement pulse wave of an artery in a test part of a subject. The radial displacement pulse wave measurement device includes a housing, a non-transparent airbag, a pressure control module, a displacement sensing module, and a computing unit.

[0025] The outer shell has a transparent portion containing a hole or a first transparent plate. A non-transparent airbag is located below the transparent portion. The main body of the non-transparent airbag is made of a material that is not easily stretched or deformed. The non-transparent airbag includes a transparent window that overlaps with the transparent portion of the outer shell. The transparent window contains a transparent material that is not easily stretched or deformed, or a second transparent plate. A pressure control module is used to control the internal pressure of the transparent airbag, thereby controlling the downward pressure applied by the transparent airbag to the test area to amplify the pulse signal of the artery. A displacement sensing module is located above the transparent portion and is used to sense the pulse of the artery, measure the dynamic distance between the skin of the test area and the displacement sensing module caused by the pulse of the artery, and obtain the radial displacement pulse wave. A computing unit is communicatively connected to the pressure control module and the displacement sensing module, respectively, and is used to transmit control signals to the pressure control module and the displacement sensing module, respectively, and to receive information transmitted from the pressure control module and the displacement sensing module and perform calculations.

[0026] According to one embodiment of this disclosure, the main body material of the non-transparent airbag, which is a transparent material that is not easily stretched or deformed, includes polymethyl methacrylate, cellulose acetate, nylon-66 polyamide resin, nylon-6 polyamide resin, polybutylene terephthalate, polyethyl terephthalate, polyphenylene oxide, polycarbonate, ethylene-vinyl acetate copolymer, polyethylene, polypropylene, polyvinyl chloride, polyacetal or polyurethane, glass, quartz, polystyrene or acrylonitrile-butadiene-styrene copolymer.

[0027] According to one embodiment of this disclosure, the transparent material of the transparent window that is not easily stretched or deformed includes polymethyl methacrylate, cellulose acetate, nylon-66 polyamide resin, nylon-6 polyamide resin, polybutylene terephthalate, polyethyl terephthalate, polyphenylene oxide, polycarbonate, ethylene-vinyl acetate copolymer, polyethylene, polypropylene, polyvinyl chloride, polyacetal or polyurethane, glass, quartz, polystyrene or acrylonitrile-butadiene-styrene copolymer.

[0028] According to one embodiment of this disclosure, the outer surface of the transparent window has an anti-reflective film.

[0029] According to one embodiment of this disclosure, when the transparent portion is the hole, the transparent window is the second transparent plate.

[0030] According to one embodiment of this disclosure, the area of ​​the second transparent plate is larger than the area of ​​the hole. When the internal pressure of the transparent airbag is too high, the second transparent plate will press against the bottom of the hole and will not be squeezed to the top of the hole.

[0031] According to one embodiment of this disclosure, the outer surface of the transparent window has an anti-reflective film.

[0032] According to one embodiment of this disclosure, the non-transparent airbag further includes a contact portion, wherein the contact portion is used to closely adhere to the skin of the subject's test area, and the material of the contact portion is a soft and stretchable thermoplastic elastomer polymer material, the thermoplastic elastomer polymer material including at least one of thermoplastic polyurethane, polyolefin elastomer, dynamically sulfurized polyolefin elastomer, polystyrene elastomer, polyether ester elastomer, polyamide elastomer, and polyvinyl chloride.

[0033] According to one embodiment of this disclosure, a reflective layer or a color separation layer is provided on the inner surface of the contact portion.

[0034] According to one embodiment of this disclosure, the radial displacement pulse wave measurement device further includes a wearable portion, in which the limb part of the subject to be measured is accommodated within the internal space of the wearable portion. The wearable portion includes a soft inner layer and a hard outer layer. The soft inner layer includes the transparent airbag. The hard outer layer is located outside the soft inner layer, forming the internal space of the wearable portion together with the soft inner layer. During the measurement of the radial displacement pulse wave, the hard outer layer maintains a fixed distance from the displacement sensing module to the furthest point on the hard outer layer from the displacement sensing module.

[0035] According to one embodiment of the present disclosure, the soft inner layer further includes a plurality of auxiliary airbags, the internal pressure of which is controlled by the pressure control module.

[0036] According to one embodiment of this disclosure, the pressure control module includes a pressure sensor and a pressure adjustment module. The pressure sensor is used to sense the internal pressure of the transparent airbag. The pressure adjustment module is used to adjust the internal pressure of the transparent airbag, and the pressure adjustment module includes a pump.

[0037] According to one embodiment of the present disclosure, the pressure adjustment module further includes a pulse width modulation circuit to adjust the speed of the pump motor.

[0038] According to one embodiment of the present disclosure, the displacement sensing module includes a transmitter and a receiver, the transmitter and the receiver being aligned with the transparent portion, and a measurement signal emitted by the transmitter can be transmitted through the transparent portion and the transparent window.

[0039] According to one embodiment of the present disclosure, the displacement sensing module includes a photoelectric displacement sensor.

[0040] According to one embodiment of this disclosure, the photoelectric displacement sensor includes a laser displacement meter, a fiber optic displacement meter, a three-dimensional scanning laser displacement meter, a time-of-flight ranging device, a three-dimensional time-of-flight ranging device, a laser Doppler rangefinder, a laser Doppler velocimeter, a Michelson interferometer, or a ranging device of a laser interferometer.

[0041] According to one embodiment of this disclosure, the displacement sensing module further includes a filter.

[0042] According to one embodiment of the present disclosure, the radial displacement pulse wave measurement device further includes a scanning position control module, which is communicatively connected to the computing unit and used to control the displacement sensing module to perform distance measurement scanning in the part to be measured, wherein the scanning position control module includes a single-axis position controller or a dual-axis position controller.

[0043] Another objective of this disclosure is to provide a method for optimizing the measurement conditions of radial displacement pulse waves of blood vessels, wherein the Y-axis is defined as substantially perpendicular to the direction of the artery and substantially parallel to the skin surface of the area to be measured. The method includes using the aforementioned radial displacement pulse wave measurement device; placing a transparent or non-transparent airbag on the skin of the area to be measured, with the displacement sensing module positioned at an initial position, wherein the displacement sensing module is a point-type displacement sensor or an array-type displacement sensor; maintaining the pressure of the transparent or non-transparent airbag at a first pressure, and pressing the transparent or non-transparent airbag down to a first depth on the area to be measured; then scanning along the Y-axis on the surface of the area to be measured until the blood vessel of the artery is located. The first measurement position is when the maximum amplitude signal of the radial displacement pulse wave of the artery is found; the displacement sensing module is kept at the first measurement position, and the pressure of the transparent airbag or the non-transparent airbag is adjusted to find the second pressure applied when the maximum signal of the radial displacement pulse wave of the artery is found; and the pressure of the transparent airbag or the non-transparent airbag is maintained at the second pressure, so that the transparent airbag or the non-transparent airbag presses down on the part to be measured to a second depth, wherein the first measurement position and the second depth are used as the measurement conditions for the radial displacement pulse wave of the artery.

[0044] According to one embodiment of this disclosure, the first pressure is applied by gradually increasing the pressure of the transparent airbag or the non-transparent airbag, causing the transparent airbag or the non-transparent airbag to press vertically down on the part to be tested until the maximum amplitude signal of the artery's vascular volume pulse wave is found.

[0045] According to one embodiment of the present disclosure, the method for optimizing the measurement conditions of radial displacement pulse wave of blood vessels further includes allowing the displacement sensing module to scan along the direction of the artery until a second measurement position is found where the local maximum signal of the radial displacement pulse wave of the artery is found, so as to replace the first measurement position as the measurement condition of the radial displacement pulse wave of the artery.

[0046] Another objective of this disclosure is to provide a method for optimizing the measurement conditions of radial displacement pulse wave of blood vessels. This method includes: finding a first measurement position above the artery of the subject's target area; using a radial displacement pulse wave measurement device as described above; placing a transparent or non-transparent airbag on the skin of the subject's target area; aligning a displacement sensing module with the first measurement position, wherein the displacement sensing module is a point-type displacement sensor or an array-type displacement sensor; gradually increasing the pressure of the transparent or non-transparent airbag, allowing the transparent or non-transparent airbag to press vertically downwards onto the target area until the maximum signal of the radial displacement pulse wave of the artery is found; maintaining the pressure of the transparent or non-transparent airbag at this measurement pressure; and pressing the transparent or non-transparent airbag down onto the target area to a measurement depth, wherein the first measurement position and the measurement depth serve as the measurement conditions for the radial displacement pulse wave of the artery.

[0047] According to one embodiment of the present disclosure, the method for optimizing the measurement conditions of radial displacement pulse wave of blood vessels further includes allowing the displacement sensing module to scan along the direction of the artery until a second measurement position is found where the local maximum signal of the radial displacement pulse wave of the artery is found, so as to replace the first measurement position as the measurement condition of the radial displacement pulse wave of the artery.

[0048] Another objective of this disclosure is to provide a method for optimizing the measurement conditions of radial displacement pulse waves of blood vessels. This method includes using the aforementioned radial displacement pulse wave measurement device; placing the transparent or non-transparent airbag on the skin of the subject's measurement area; maintaining the pressure of the transparent or non-transparent airbag at a first pressure; moving the displacement sensing module above the measurement area, wherein the displacement sensing module is an array-type displacement sensor with a measurement area that intersects the direction of the blood vessel; and finding the maximum measured vibration. One of the point displacement sensors of the amplitude signal indicates that the point displacement sensor is located at a first measurement position; adjusting the pressure of the transparent or non-transparent airbag to find the maximum signal of the radial displacement pulse wave of the artery, and maintaining the pressure of the transparent or non-transparent airbag at the second pressure, so that the transparent or non-transparent airbag presses down on the measured part to a second depth, wherein the first measurement position and the second depth serve as the measurement conditions for the radial displacement pulse wave of the artery.

[0049] According to one embodiment of this disclosure, the first pressure is applied by gradually increasing the pressure of the transparent airbag or the non-transparent airbag, causing the transparent airbag or the non-transparent airbag to press vertically down on the part to be tested until the maximum amplitude signal of the artery's vascular volume pulse wave is found.

[0050] According to one embodiment of the present disclosure, the method for optimizing the measurement conditions of radial displacement pulse wave of blood vessels further includes allowing the displacement sensing module to scan along the direction of the artery until a second measurement position is found where the local maximum signal of the radial displacement pulse wave of the artery is found, so as to replace the first measurement position as the measurement condition of the radial displacement pulse wave of the artery.

[0051] Another objective of this disclosure is to provide a method for measuring blood pressure, comprising using the aforementioned radial displacement pulse wave measuring device; placing the transparent or non-transparent airbag on the part to be measured; using the aforementioned method for optimizing the measurement conditions of the radial displacement pulse wave to locate the artery in the part to be measured of the subject, and measuring the radial displacement pulse wave of the artery; gradually pressurizing the transparent or non-transparent airbag until the radial displacement pulse wave of the artery appears and then disappears; gradually depressurizing the transparent or non-transparent airbag until the radial displacement pulse wave of the artery begins to appear, at which point the pressure of the transparent or non-transparent airbag is the systolic pressure of the artery; and continuing to gradually depressurize the transparent or non-transparent airbag until the radial displacement pulse wave of the artery begins to disappear, at which point the pressure of the transparent or non-transparent airbag is the diastolic pressure of the artery.

[0052] Another objective of this disclosure is to provide a method for measuring pulse wave velocity, comprising, while simultaneously recording an electrocardiogram (ECG), measuring a proximal radial displacement pulse wave at a proximal measurement position of a proximal artery closer to the heart in a subject using the aforementioned radial displacement pulse wave measuring device; simultaneously recording the radial displacement pulse wave of the proximal artery and the subject's ECG to obtain the delay time T1 of the proximal radial displacement pulse wave relative to the ECG R wave; simultaneously recording an ECG, measuring a distal radial displacement pulse wave at a distal measurement position of a distal artery farther from the heart in the subject using the same radial displacement pulse wave measuring device; simultaneously recording the radial displacement pulse wave of the distal artery and the subject's ECG to obtain the delay time T2 of the distal radial displacement pulse wave relative to the ECG R wave; and calculating the time difference ΔT between T1 and T2 = T2 - T1; Measure the distance ΔD between the proximal artery and the distal artery; and calculate the pulse wave velocity PWV = ΔD / ΔT.

[0053] According to one embodiment of this disclosure, the proximal measurement position and the distal measurement position are either the first measurement position found using the above-described method for optimizing the measurement conditions of radial displacement pulse waves of blood vessels, or the second measurement position found using the above-described method for optimizing the measurement conditions of radial displacement pulse waves of blood vessels.

[0054] Another objective of this disclosure is to provide a method for measuring pulse wave velocity, comprising: measuring a proximal radial displacement pulse wave at a proximal measurement position on a proximal artery site closer to the heart of the subject without recording an electrocardiogram; simultaneously measuring a distal radial displacement pulse wave at a distal measurement position on a distal artery site farther from the heart of the subject without recording an electrocardiogram, wherein the proximal measurement position and the distal measurement position use one or two of the aforementioned radial displacement pulse wave measuring devices to simultaneously measure the proximal radial displacement pulse wave and the distal radial displacement pulse wave; calculating the time difference ΔT between the proximal radial displacement pulse wave and the distal radial displacement pulse wave; measuring the distance ΔD between the proximal artery site and the distal artery site; and calculating the pulse wave velocity PWV = ΔD / ΔT.

[0055] According to one embodiment of this disclosure, the proximal measurement position and the distal measurement position are either the first measurement position found using the above-described method for optimizing the measurement conditions of radial displacement pulse waves of blood vessels, or the second measurement position found using the above-described method for optimizing the measurement conditions of radial displacement pulse waves of blood vessels.

[0056] Another objective of this disclosure is to provide a continuous blood pressure measurement method, comprising using the aforementioned blood pressure measurement method to measure the diastolic blood pressure of the subject in an initial state and the corresponding first compression depth of the transparent or non-transparent airbag on a part of the body to be measured, and the systolic blood pressure in the initial state and the corresponding second compression depth of the transparent or non-transparent airbag, wherein the difference between the first compression depth and the second compression depth is the blood vessel diameter R of the subject; calculating the change in blood vessel diameter ΔR of the subject from the radial displacement pulse wave pattern of the subject over time; measuring the pulse wave velocity PWV of the subject using the aforementioned pulse wave velocity measurement method; and obtaining the blood density of the subject. The change in blood pressure ΔP is calculated using the Bramwell-Hill formula as follows: ; and calculate the subject's instantaneous systolic blood pressure (= initial systolic blood pressure + ΔP) and instantaneous diastolic blood pressure (= initial diastolic blood pressure + ΔP).

[0057] The aforementioned radial displacement pulse wave measurement device has the following technical advantages. First, it can directly measure the radial displacement pulse wave in blood vessels, providing more accurate results compared to traditional pressure pulse wave measurement methods. Second, it boasts high accuracy, reaching below 100 micrometers, providing detailed pulse wave information that facilitates various pulse wave analysis applications. Third, it can be applied to many non-invasive measurement methods, offering convenience and stability, providing immediate measurement results and waveforms, and allowing for long-term continuous monitoring. In summary, this radial displacement pulse wave measurement device has broad application value in cardiovascular and biomedical fields, supporting better personalized medicine and health monitoring. Simple Explanation of the Diagram

[0058] Figure 1 is a schematic diagram of the functional block architecture of a radial displacement pulse wave measuring device according to an embodiment of the present disclosure.

[0059] Figure 2 is a cross-sectional structural schematic diagram of the wearable part of a radial displacement pulse wave measuring device according to an embodiment of the present disclosure.

[0060] Figure 3A is a schematic diagram illustrating the operation flow of automatically finding the measurement point of "radial displacement pulse wave" using a scanning position control module 140 according to an embodiment of the present disclosure, wherein the displacement sensing module 130 is a "point-type" displacement sensor.

[0061] Figure 3B is a schematic diagram illustrating the operation process of manually finding the measurement point of "radial displacement pulse wave" according to another embodiment of the present disclosure, wherein the displacement sensing module 130 is a "point type" displacement sensor.

[0062] Figure 3C illustrates a schematic diagram of the operation process for finding the measurement point of "radial displacement pulse wave" according to another embodiment of this disclosure, wherein the displacement sensing module 130 is a "linear array" displacement sensor.

[0063] Figure 4 is a schematic diagram illustrating the waveform changes of vascular volume pulse wave and radial displacement pulse wave with pressure and time according to an embodiment of the present disclosure.

[0064] Figure 5 is a schematic diagram of the process for measuring blood pressure using the radial displacement pulse wave measuring device 100 shown in Figure 1.

[0065] Figure 6A is an enlarged schematic diagram of the radial displacement pulse wave during period III (t2-t3) of Figure 4.

[0066] Figure 6B shows the relationship between the interval between heartbeats and time.

[0067] Figure 6C shows the RRI spectrum distribution obtained after HRV calculation via Discrete Fourier Transform.

[0068] Figure 7A is a schematic diagram of an embodiment of the present disclosure of using electrocardiogram-assisted measurement of pulse wave velocity.

[0069] Figure 7B is a schematic diagram of measuring pulse wave velocity using two pulse wave measuring devices simultaneously, according to one embodiment of the present disclosure.

[0070] Figure 7C is a flowchart of the pulse wave velocity measurement method using the method shown in Figure 7A.

[0071] Figure 8 is a flowchart of the continuous blood pressure measurement method. Implementation

[0072] Therefore, this disclosure provides a device for measuring radial displacement pulse waves and its application method. The aforementioned device for measuring radial displacement pulse waves, through the coordinated design of an airbag, a pressure control module, and a displacement sensing module, can directly measure the waveform of the "vascular radial displacement pulse wave" with an accuracy of less than 100 micrometers. Therefore, it can provide many details of the waveform of the "vascular radial displacement pulse wave" for various application analyses. The measurement of blood pressure, heart rate variability, and pulse wave velocity, as well as continuous blood pressure measurement, will be introduced below. However, these measurement methods represent only a small portion of the applications, and the application methods of the radial displacement pulse wave measurement device are not limited to these.

[0073] The coordinate axes are defined as follows: The XY plane is substantially parallel to the subject's skin surface, with the X-axis substantially parallel to the direction of the subject's blood vessels and the Y-axis substantially perpendicular to the direction of the subject's blood vessels. Therefore, the Z-axis is substantially perpendicular to the subject's skin surface. The definitions of the X, Y, and Z axes mentioned below are the same. [Radial displacement pulse wave measurement device]

[0074] Figure 1 is a functional block architecture diagram of a radial displacement pulse wave measurement device according to an embodiment of the present disclosure. In Figure 1, the radial displacement pulse wave measurement device 100 includes an airbag 110, a pressure control module 120, a displacement sensing module 130, a scan position control module 140, and a computing unit 150. The pressure control module 120, the displacement sensing module 130, and the scan position control module 140 are all communicatively connected to the computing unit 150.

[0075] Figure 2 is a cross-sectional schematic diagram of the wearable part of a radial displacement pulse wave measurement device according to an embodiment of the present disclosure. To better ensure a stable and tight fit between the airbag 110 and the subject's measurement area 160, and to fix the relative position between the displacement sensing module 130 and the subject's measurement area 160, thereby effectively reducing noise generated when the subject changes posture or shakes, a wearable part is designed for the radial displacement pulse wave measurement device 100 to increase the accuracy of pulse wave measurement. In Figure 2, the radial displacement pulse wave measurement device 100 may further include a wearable part 200 and a housing 230. The wearable part 200 includes a hard outer layer 210 and a soft inner layer 220, while the housing 230 has a transparent portion 232. In the radial displacement pulse wave measurement device 100 described above, the airbag 110 is disposed below the transparent portion 232 (outside the housing 230), and the displacement sensing module 130 is disposed above the transparent portion 232 (inside the housing 230). The remaining calculation unit 150, pressure control module 120, and scan position control module 140 can be optionally encapsulated inside the housing 230 or disposed outside the housing 230. To simplify the complexity of the diagram, only the displacement sensing module 130 is shown inside the housing 230 in FIG2. When using the wearable part 200 and housing 230 of FIG2, the airbag 110 can be positioned between the subject's test part 160 and the housing 230, and the displacement sensing module 130 can be aligned with the transparent portion 232 of the housing 230, allowing the emitted signal 130a and reflected signal 130b of the displacement sensing module 130 to pass through the transparent portion 232.

[0076] Next, we will introduce each component in the radial displacement pulse wave measuring device 100.

[0077] In Figures 1 and 2, the airbag 110 has three functions. The first function is to generate downward pressure that compresses the subcutaneous tissue. The second function is to allow the measurement signals (i.e., transmitted signal 130a and reflected signal 130b) from the displacement sensing module 130 to penetrate the internal space of the airbag 110 and then be reflected back to the displacement sensing module 130. The third function is that when the airbag 110 is in close contact with the skin, it can serve as a space to accommodate the increase in the diameter of the arteries with each pulse beat.

[0078] The main body material of the airbag 110 can be made of any usable, non-stretchable, and "transparent" polymer material, or it can be made of any usable, non-stretchable, and "non-transparent" polymer material. In this disclosure, "non-transparent" includes "opaque" and "semi-transparent". The aforementioned transparent or non-transparent polymer materials may be, for example, (but not limited to) polymethyl methacrylate (PMMA), cellulose acetate (CA), nylon-66 polyamide resin (PA-66), nylon-6 polyamide resin (PA-6), polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyphenylene oxide (PPO), polycarbonate (PC), ethylene-vinyl acetate copolymer (EVA), polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polyacetal (POM), or polyurethane (PU).

[0079] When the airbag 110 is constructed using a "transparent" polymer material, the measurement signal (i.e., the emitted signal 130a and the reflected signal 130b) of the displacement sensing module 130 can penetrate the main body material of the airbag 110. When the transparent portion 232 of the outer shell 230 in Figure 2 is a "hole", in order to increase the penetration rate of the measurement signal of the displacement sensing module 130 to the main body material of the airbag 110, or to reduce the refraction and reflection of the measurement signal of the displacement sensing module 130 to the main body material of the airbag 110 and thus affect the accuracy of the measurement, the upper part of the airbag 110 made of the "transparent" polymer material in Figure 2 can also have a transparent window 112 made of a transparent plate that is not easily deformable, and the area of ​​the transparent plate of the transparent window 112 is larger than the hole of the transparent portion 232, so as to prevent the transparent plate of the transparent window 112 from being squeezed into the interior of the outer shell 230 when the pressure of the airbag 110 is too high. In use, the transparent window 112 of the airbag 110 needs to be aligned with the transparent portion 232 of the outer shell 230 (that is, the transparent window 112 and the transparent portion 232 must at least partially overlap) so that the measurement signal of the displacement sensing module 130 (that is, the transmitted signal 130a and the reflected signal 130b) can vertically penetrate the transparent window 112, which is made of a transparent plate, and thus penetrate the internal space of the airbag 110. When the transparent portion 232 of the outer shell 230 in Figure 2 is a "transparent plate" that is not easily deformable, the airbag 110, which is made of "transparent" polymer material, does not need the transparent window 112 made of a transparent plate. Furthermore, regardless of whether the transparent portion 232 of the outer shell 230 is a hole or a transparent plate, since the outer shell 230 is located above the airbag 110, during the pressurization of the airbag 110, the outer shell 230 can also act as a "baffle" to limit the upward expansion of the airbag 110, so that the transparent window 112 in contact with the transparent portion 232 forms a flat plane, and so that the increased pressure in the airbag 110 can be used almost only to press down on the test part 160 of the subject.

[0080] However, when the airbag 110 is constructed using a "non-transparent" polymer material, the measurement signal of the displacement sensing module 130 is difficult to penetrate or can only partially penetrate the main body material of the airbag 110. Therefore, the airbag 110 needs to have at least a transparent window 112 to allow the measurement signal of the displacement sensing module 130 to pass through. In use, the transparent window 112 of the airbag 110 also needs to be aligned with the transparent portion 232 of the outer shell 230 (that is, the transparent window 112 and the transparent portion 232 need to at least partially overlap) in order to allow the measurement signal of the displacement sensing module 130 (that is, the emitted signal 130a and the reflected signal 130b) to pass through the transparent window 112 and the transparent portion 232 to pass through the internal space of the airbag 110. When the transparent portion 232 of the outer shell 230 in Figure 2 is a "hole", the transparent window 112 of the airbag 110, which is made of "non-transparent" polymer material, needs to be constructed using a transparent plate that is not easily deformed. Furthermore, the area of ​​the transparent plate of the transparent window 112 is larger than the hole in the transparent portion 232 to prevent the transparent plate of the transparent window 112 from being squeezed into the interior of the outer shell 230 due to excessive internal pressure in the airbag 110. Other situations are similar to those described above when the airbag 110 is made of "transparent" polymer material, and therefore will not be elaborated further. When the transparent portion 232 of the outer shell 230 in Figure 2 is a "transparent plate" that is not easily deformed, the transparent material used for the transparent window 112 of the airbag 110, which is made of "non-transparent" polymer material, is not limited to a transparent plate; a transparent material that is not easily stretched or deformed can also be used to construct the transparent window 112. The aforementioned transparent materials that are not easily stretched or deformed can be, for example, polymethyl methacrylate, cellulose acetate, nylon-66 polyamide resin, nylon-6 polyamide resin, polybutylene terephthalate, polydiethyl terephthalate, polyphenylene oxide, polycarbonate, ethylene-vinyl acetate copolymer, polyethylene, polypropylene, polyvinyl chloride, polyacetal, or polyurethane, similar to the situation of the airbag 110 made of the aforementioned "transparent" polymer material, so further details will not be elaborated.

[0081] Therefore, in Figure 2, both the transparent window 112 of the airbag 110 formed by the transparent plate and the transparent portion 232 of the outer shell 230 can limit the upward expansion of the airbag 110, so that the increased pressure in the airbag 110 can only press down on the subject's test portion 160 through the contact portion 114 of the airbag 110. Therefore, the radial displacement of blood vessels caused by the pulse can be maximized, which is beneficial for the measurement of the displacement sensor 130.

[0082] The material used for the non-deformable transparent plate constituting the transparent window 112 or transparent portion 232 can be, for example (but not limited to), glass, quartz, polystyrene (PS), or acrylonitrile butadiene styrene copolymer (ABS), or the same transparent material used in the airbag. The transparent window 112 and transparent portion 232 can be made of the same or different materials. According to some embodiments, the transparent portion 232 of the outer shell 230 and the transparent window 112 of the airbag 110 can also be combined into one, as long as a single, high-hardness transparent plate is used.

[0083] According to some other embodiments, the outer surface of the transparent window 112 facing the outside of the airbag 110 can also be coated with an anti-reflective film to increase the penetration of the measurement signal of the displacement sensing module 130 through the transparent window 112, thereby reducing noise caused by the measurement signal reflected by the transparent window 112, and also increasing the wear resistance of the transparent window 112.

[0084] Because the main body material of the airbag 110 is made of a material that is not easily stretched or deformed, the height of the reflective surface pulsation at the point where the skin or airbag is in close contact with the skin will be reduced. In order to reduce the lateral tension of the material while maintaining the downward pressure inside the airbag, a soft, stretchable polymer material can be used in local areas. The airbag 110 can also have a contact portion 114, as shown in Figures 1 and 2. The contact portion 114 is used to contact the skin of the test area 160 of the subject, and the skin of the test area 160 will pulsate due to the pulse of the artery 250 (see Figure 2) located beneath it. Therefore, a soft (hardness range of Shore hardness 20C to 72D) and stretchable polymer material can be used to reduce the lateral tension of the material on the constantly pulsating skin of the test area 160. Combined with the aforementioned non-deformable airbag 110 body and its transparent window 112, the soft and elastic contact portion 114 can effectively transmit the downward pressure of the airbag 110 on the test area 160. Alternatively, by using the same non-stretchable and deformable material as the airbag, after inflation, the compressible and elastic air layer inside the airbag 110 serves as the elastic absorption space required during pulse beats, while reducing the lateral tensile force of the material. This makes it easier for the displacement sensing module 130 to detect the measurement signal of the radial displacement change of blood vessels caused by pulse beats. The contact portion 114 can be transparent, semi-transparent, or opaque. The aforementioned polymer material can be the same as the airbag body material or can be, for example, thermoplastic elastomers (TPE). Suitable thermoplastic elastomers include, for example, thermoplastic polyurethane (TPU), polyolefin elastomer (TPO), dynamically vulcanized polyolefin elastomer (TPV), polystyrene elastomer (TPS / TPR), polyether ester elastomer (TPEE), polyamide elastomer (TPA), and polyvinyl chloride (PVC).

[0085] According to some embodiments, the inner surface of the contact portion 114 facing the airbag 110 may be smooth, or an additional reflective layer or a dichroic layer may be formed on the inner surface of the contact portion 114. For example, when using a red laser light source, the dichroic layer plated on the inner surface of the contact portion 114 of the airbag 110 can reflect the light of the red laser while allowing other visible light to pass through, increasing the reflection intensity of the measurement signal (i.e., the red laser) and facilitating simultaneous alignment with the alignment mark below the contact portion 114. In this way, the reflection intensity and uniformity (rather than scattering) of the measurement signal emitted by the displacement sensing module 130 by the inner surface of the contact portion 114 can be increased. The contact portion 114 may also be translucent, which can simultaneously increase the reflection intensity of the measurement signal and facilitate simultaneous alignment with the alignment mark or reflective patch below the contact portion 114.

[0086] The pressure control module 120 in Figure 1 controls the internal pressure of the airbag 110 by inflating or deflating it, thereby regulating the pressure depth of the airbag 110 on the test area 160. According to some embodiments, the pressure control module 120 may include a pressure sensor 122 and a pressure adjustment module 124 (including a pump, gas lines, and a valve) that are signal-connected to each other. The pressure sensor 122 can sense the internal pressure of the airbag 110 and can therefore be used to measure the subject's "vascular volume pulse wave." The gas lines of the pressure adjustment module 124 are connected to the pump and the airbag 110 respectively, and the valve is installed at an appropriate position in the gas lines. Therefore, the rotation direction (forward and reverse) of the motor in the pump can be controlled, or the speed of the motor in the pump can be adjusted using a pulse width modulation (PWM) circuit. Alternatively, two motors can be used in the pump, one for intake and one for exhaust. The amount of gas entering and exiting the airbag 110 can also be controlled by switching on and off the air valve, thus quickly and accurately controlling the internal pressure of the airbag 110. This, in turn, allows control over the depth of pressure exerted by the airbag 110 on the skin of the subject's test area 160 along the Z-axis. Therefore, the pump described above, combined with an air valve, a pulse width modulation circuit, or a combination of both, along with the maximum amplitude of the detected blood vessel volume, can quickly determine the required airbag pressure, thereby quickly finding the approximate depth of pressure exerted by the radial displacement pulse wave of the target blood vessel on the subject's skin.

[0087] The displacement sensing module 130 in Figures 1 and 2 is used to measure the distance in the Z-axis direction from the displacement sensing module 130 to the skin of the subject's test area 160 (when the contact portion 114 of the airbag 110 is made of transparent material), or to measure the distance in the Z-axis direction from the displacement sensing module 130 to the contact portion 114 of the airbag 110 (when the contact portion 114 of the airbag 110 is made of opaque material). Therefore, the subject's "radial displacement pulse wave" can be measured, hereinafter referred to as "radial displacement pulse wave".

[0088] The displacement sensing module 130 can be any available displacement sensor, comprising a transmitter 132 that emits a measurement signal and a receiver 134 that receives the reflected measurement signal. Classified according to the shape of the maximum detectable area of ​​the displacement sensing module 130, the displacement sensing module 130 can be a point-type displacement sensor or an array-type displacement sensor composed of multiple point-type displacement sensors, such as a linear or surface-type array-type displacement sensor. The measurement resolution of the displacement sensing module 130 can be below 100 micrometers, for example, it can have a displacement sensor with a resolution of 100 micrometers, 90 micrometers, 80 micrometers, 70 micrometers, 60 micrometers, 50 micrometers, 40 micrometers, 30 micrometers, 20 micrometers, 10 micrometers, 1 micrometer, or below 1 micrometer.

[0089] The aforementioned displacement sensor can be, for example, a photoelectric displacement sensor that uses light sources of various wavelengths (i.e., the aforementioned "emitter 132") to measure distance. The aforementioned photoelectric displacement sensor can be, for example, a laser displacement meter, fiber-optic displacement sensors, a three-dimensional laser scanner (3D laser scanner); for example, a binocular depth CCD with a programmable structured light system, a time-of-flight (TOF) device, a three-dimensional time-of-flight (3D TOF) device, a laser doppler stadimeter, a laser doppler velocimetry, a Michelson interferometer, or various other distance measuring devices.

[0090] According to some embodiments, the displacement sensing module 130 may further include a filter 136 to remove various noises doped into the measurement signal, so as to further increase the signal-to-noise ratio of the measurement signal.

[0091] The scanning position control module 140 in Figure 1 is used to control the displacement sensing module 130 to move above the subject's test area 160 and to control the displacement sensing module 130 to perform ranging scans within the test area 160. By using the coordinates set by the position control and the amplitude of the fixed-point pulse wave from the displacement sensing module 130, the module can locate the subject's blood vessel position within the test area 160, or find a measurement position with a better signal-to-noise ratio for the "radial displacement pulse wave" along the direction of the blood vessel, thereby obtaining a better measurement signal for the radial displacement pulse wave. Therefore, the scanning position control module 140 is an optional module, meaning it can be omitted. When the scanning position control module 140 is not present, the user can move the displacement sensing module 130 to the subject's measurement area 160, allowing the displacement sensing module 130 to perform distance scanning on the subject's measurement area 160. Alternatively, the user can touch the point of maximum pulse and attach a reflective sheet, aligning the laser light source with the reflective sheet. The displacement sensing module 130 can be a photoelectric displacement sensor with a detection area of ​​point, line, or area. According to some embodiments, the aforementioned scanning position control module 140 may include, for example, a single-axis position controller or a dual-axis position controller (e.g., an XY dual-axis moving platform or a cylindrical coordinate moving mechanism).

[0092] The computing unit 150 in Figure 1 comprises multiple modules consisting of a plurality of hardware circuits electrically connected to each other. The computing unit 150 can be any usable machine with computing capabilities, such as various types of computers, microprocessors, cloud computing units, mobile computing devices, and edge computing for artificial intelligence. According to some embodiments, the computing unit 150 includes a power module 151, a memory module 152, a communication module 153, an operation module 154, a display module 155, and a processing module 156 that are electrically or signal-connected to each other. Some combinations of these modules can also be integrated into a single chip.

[0093] The power module 151 described above is used to supply the power required by the computing unit 150. The power module 151 can be an AC power source (e.g., power supplied by a power plant through a general power outlet) or a DC power source (e.g., various dry cell batteries or rechargeable batteries).

[0094] The memory module 152 described above can be any available volatile or non-volatile data storage device to store any data generated during the measurement process of the displacement sensing module 130.

[0095] The communication module 153 is signal-connected to the pressure control module 120, displacement sensing module 130, and scan position control module 140, respectively, to transmit control signals from the computing unit 150 to these modules, or to receive information from them, allowing the analysis module 158 to perform calculations and analysis or store the information in the memory module 152. The communication module 153 can also be signal-connected to a cloud database, a cloud computing center, or both, to obtain pulse wave interpretation reference data and perform analysis and calculations for subsequent pulse wave analysis and interpretation. The aforementioned cloud-based database may include, for example, databases related to acupoints and meridians, pulse comparison databases, traditional Chinese medicine databases, or databases for pulse wave analysis, vascular elasticity, pulse wave velocity (PWV), continuous blood pressure analysis, cloud-based artificial intelligence computing, and various other databases related to pulse wave analysis, to increase the accuracy of pulse wave analysis result interpretation, but is not limited to these. The communication module 153 can also send the acquired monitoring data to the cloud computing center for data analysis and calculation to obtain interpretation results.

[0096] The aforementioned operating module 154 provides a user interface for the radial displacement pulse wave measurement device 100, allowing users to issue control commands through the operating module 154 to operate the pressure control module 120, displacement sensing module 130, and scan position control module 140. The user interface can also be displayed on a remote display device via the communication module 153 to facilitate remote operation required for telemedicine.

[0097] The aforementioned processing module 156 may include a control module 157 and an analysis module 158. The control module 157 is responsible for providing control commands to the pressure control module 120, the displacement sensing module 130, and the scan position control module 140. The analysis module 158 is responsible for calculating and analyzing the information transmitted from the pressure control module 120, the displacement sensing module 130, and the scan position control module 140. For example, the measurement signal of the "radial displacement pulse wave" obtained by the displacement sensing module 130 will simultaneously include the Z-axis displacement generated by the pulse (a dynamic AC signal) and the Z-axis displacement generated by the airbag 110 pressing down on the test part 160 (i.e., the "Z-axis compression depth", a static DC signal). At this point, if only the Z-axis displacement caused by the airbag 110 pressing down on the test part 160 needs to be clearly measured, the analysis module 158 of the calculation unit 150 can filter out the dynamic Z-axis displacement caused by the pulse in the obtained "radial displacement pulse wave" measurement signal, leaving only the static Z-axis displacement of the airbag 110 pressing down on the test part 160. Using this static DC signal, the "Z-axis compression depth" corresponding to the pulse wave signal with the maximum signal-to-noise ratio and the corresponding pressure value of the airbag 110 can be easily found, serving as the target setting value for the pressure control module 120. Therefore, the accuracy and repeatability of the measurement signal can be improved, facilitating the acquisition of the "radial displacement pulse wave" signal from the subject's blood vessels.

[0098] The aforementioned display module 155 is used to display the user interface of the control module 157; to display information transmitted to the analysis module 158 by the pressure control module 120, displacement sensing module 130, and scan position control module 140; and to display the results of the analysis of this information by the analysis module 158. If the display module 155 is located at a remote location, the aforementioned information can also be displayed on the remote display module 155 via the communication module 153 to facilitate telemedicine.

[0099] In Figure 2, the wearable part 200 is fixed to the outer shell 230, and the internal space of the wearable part 200 is used to accommodate the limb part 240 where the test part 160 is located. Moreover, an artery 250 passes under the skin of the test part 160, allowing the displacement sensing module 130 to measure the radial displacement pulse wave of the artery 250. The wearable part 200 includes a hard outer layer 210 and a soft inner layer 220. The hard outer layer 210 is essentially cylindrical in shape, and the soft inner layer 220 is basically formed by extending from the air bladder 110.

[0100] The rigid outer layer 210 of the wearable unit 200 allows the distance MD between the displacement sensing module 130 and the furthest point 212 on the rigid outer layer 210 from the displacement sensing module 130 to remain fixed, thus ensuring a stable measurement reference during pulse wave measurement. Therefore, the material of the rigid outer layer 210 needs to have sufficient mechanical strength to maintain the aforementioned distance MD at a fixed value even after the wearable unit 200 is fixed to the subject and the airbag 110 is inflated. According to some embodiments, it is easier to maintain a fixed distance MD when the airbag 110 is only distributed in the upper half of the rigid outer layer 210.

[0101] The available configurations of the hard outer layer 210 can vary depending on the shape of the limb where the test part 160 is located, and can have different structural designs. Therefore, Figure 2 is only a simplified schematic diagram, and the actual structure of the hard outer layer 210 should not be limited by this. For example, the hard outer layer 210 can be designed similarly to a metal watch strap and buckle, allowing the length of the metal strap to be varied for easy application to the limb where the test part 160 is located, and also for easy storage and carrying. If the hard outer layer 210 uses a single annular plate-shaped hard shell structure, then the circumference of the hard outer layer 210 is fixed, as long as the limb where the test part 160 is located can pass through it directly. Alternatively, the hard outer layer 210 can use a structure of two or more annular plate-shaped hard shells, plus suitable hard outer layer fasteners (such as buckles) to fix the overlapping parts of the different annular plate-shaped hard shells. Alternatively, the hard outer layer 210 can be designed as a C-shaped structure, with the wrist inserted through the notch of the C-shaped structure during measurement, and a soft inner layer 220 disposed on the inside of the notch.

[0102] As described above, the soft inner layer 220 is basically composed of an air bladder 110, so the internal gas pressure of the soft inner layer 220 can also be controlled by the pressure control module 120. Therefore, the opening size of the hard outer layer 210 can be adjusted more easily, allowing the wearable part 200 to more conveniently adapt to limbs of different sizes where the test part 160 is located, making pulse wave measurement easier. Similarly, the available configurations of the soft inner layer 220 can vary depending on the shape of the limb where the test part 160 is located, and can have different structural designs. Therefore, Figure 2 is only a simplified schematic diagram, and the actual structure of the soft inner layer 220 should not be limited by this. For example, the structural design of the soft inner layer 220 can be directly composed of a cylindrical air bladder 110. Alternatively, the structural design of the soft inner layer 220 can also be composed of a sheet-like air bladder 110, with the two ends of the air bladder 110 overlapping, and the two ends of the air bladder 110 can be fixed using suitable soft inner layer fasteners (such as Velcro). Furthermore, the soft inner layer 220 only needs to retain the measuring part 110a as shown in Figure 2 (the measuring part 110a includes the transparent window 112 and contact part 114 of the airbag 110), and other parts of the airbag 110 can be omitted.

[0103] According to some embodiments, in order to accommodate a wider range of limb parts 240 where the test part 160 is located, in addition to the airbag 110 mentioned above, the soft inner layer 220 may also include multiple independent auxiliary airbags. The pressure of each auxiliary airbag can be independently controlled by the pressure control module 120, so that each independent airbag can easily fill the space of varying sizes between the inner side of the wearable part 200 and the limb. [Method for finding the measurement point for "radial displacement pulse wave"]

[0104] Next, we will introduce a method for measuring pulse waves using the radial displacement pulse wave measuring device 100 described above. When the radial displacement pulse wave measuring device 100 has a scanning position control module 140, at an appropriate airbag compression depth, the movement of the displacement sensing module 130 can be "automatically" controlled to scan over the subject's measurement area 160 to find a better measurement position within the measurement area 160. Please refer to Figures 3A and 3B first.

[0105] Figure 3A is a schematic diagram illustrating the operation flow of automatically finding the measurement point of "radial displacement pulse wave" using a scanning position control module 140 according to an embodiment of the present disclosure, wherein the displacement sensing module 130 is a "point-type" displacement sensor.

[0106] In step 310 of Figure 3A, the airbag 110 of the radial displacement pulse wave measuring device 100 is first placed on the subject's test area 160, and the contact part 114 of the airbag 110 is brought into contact with the skin of the subject's test area 160. By detecting the maximum value of the vascular volume pulse wave amplitude, the downward pressure depth of the airbag 110 can be roughly adjusted to a depth that can detect the vascular pulse beat, even before the displacement sensing module 130 is aligned with the blood vessel, thus speeding up the overall measurement process.

[0107] In step 320, the pressure control module 120 gradually pressurizes the inside of the airbag 110 to increase the internal pressure of the airbag 110. When the pressure sensor 122 in the pressure control module 120 detects the signal from the pulse to its maximum value, that is, when the amplitude of the "vascular volume pulse wave" is at its maximum value, a rough compression depth has been found, and the pressure control module 120 stops pressurizing the airbag 110 to maintain the internal pressure of the airbag 110. According to some embodiments, step 320 can also be skipped, and step 330a can be executed directly.

[0108] In step 330a, a starting position (coordinates) is first selected on the test part 160 of the subject, and the point displacement sensor is moved above the starting position using the scanning position control module 140 as the starting point of the scan, and the distance between the point displacement sensor and the test part 160 is measured.

[0109] In step 340a, the scanning position control module 140 is used to make the point displacement sensor scan along the direction perpendicular to the direction of the blood vessel (i.e., the direction of the Y-axis). The amplitude of the radial displacement pulse wave can be measured to gradually increase and then gradually decrease within a certain area. The point where the amplitude signal of the "radial displacement pulse wave" on the Y-axis is the maximum is found, which is also the location of the blood vessel (first measurement position).

[0110] In step 350a, the scanning position control module 140 is used to align the point displacement sensor with the first measurement position.

[0111] In step 360, the pressure of the airbag 110 is adjusted until the maximum amplitude signal of the "radial displacement pulse wave" is obtained at the first measurement position, thus obtaining a measurement signal of the "radial displacement pulse wave" with better noise reduction. At this point, the pressure of the airbag 110 is the optimal "measurement pressure," and the depth to which the airbag 110 presses down on the test part 160 is the optimal "measurement depth." Therefore, by step 360, the process of finding the pulse wave measurement point can be concluded.

[0112] However, step 370 is only necessary when there are special requirements (such as specific pulse diagnosis locations in traditional Chinese medicine) or when the signal-to-noise ratio of the detected "radial displacement pulse wave" is insufficient. In step 370, the scan position control module 140 is used to scan along the blood vessel to find the location of the local maximum value of the "radial displacement pulse wave" signal on the X-axis (the second measurement position). Once found, this is the measurement point of the "radial displacement pulse wave" at the second measurement position.

[0113] When the radial displacement pulse wave measuring device 100 does not have a scan position control module 140 or does not wish to use the scan position control module 140, the movement of the point-type displacement sensor can be manually controlled to scan over the subject's measurement area 160 to find a better measurement position within the measurement area 160. Since the movement of the point-type displacement sensor is controlled manually, the first half of the manual control process differs slightly from the first half of the automatic control process. Please refer to Figure 3B.

[0114] Next, please refer to Figure 3B. Figure 3B is a schematic diagram illustrating the operation flow of manually locating the measurement point of "radial displacement pulse wave" according to another embodiment of this disclosure, wherein the displacement sensing module 130 is a "point-type" displacement sensor. Since the measurement point needs to be manually located first, it is preferable that at least the transparent window 112 and the contact portion 114 of the airbag 110 are made of transparent material. Alternatively, the main body of the airbag 110, the transparent window 112, and the contact portion 114 can all be made of transparent material, or openings can be made in the visual area of ​​the wearable part 200 and the outer shell 230, or transparent material can be used to facilitate the user's visual location of the measurement point. In step 305, the "manual" method can be used to replace the scanning position control module 140. After touching the arterial pulsation point of the part to be measured 160, the location of the blood vessel in the part to be measured 160 (first measurement position) can be directly found. In this step, when the contact part 114 is transparent or semi-transparent, a reflective sheet that reflects the measurement signal can also be used. After attaching this reflective sheet to the skin surface where the blood vessel is located, the measurement signal emitted by the displacement sensing module 130 is aligned with the reflective sheet before proceeding to subsequent steps 310, 350a, 360, and 370. Since subsequent steps 310, 350a, 360, and 370 are the same as or similar to those in Figure 3A above, they are omitted and will not be described in detail.

[0115] Next, please refer to Figure 3C. Figure 3C is a schematic diagram illustrating the operation flow for finding the measurement point of the "radial displacement pulse wave" according to another embodiment of this disclosure, wherein the displacement sensing module 130 is a "linear array" displacement sensor. The flow of Figure 3C is similar to that of Figure 3A, except that since the "linear array" displacement sensor is composed of point displacement sensors arranged in a line, the steps related to scanning on the Y-axis to find the first measurement position can be omitted. Therefore, only the slightly different steps 330c and 340c will be described below, and the rest will not be repeated. In addition, step 320 can be skipped, and step 330c can be performed directly to measure the radial displacement pulse wave.

[0116] In step 330c, the scanning position control module 140 or manual mode can be used to directly align the linear measurement area of ​​the linear array displacement sensors parallel to the Y-axis and across the location of the blood vessel. In step 340c, the pressure inside the balloon is gradually adjusted, and it is observed which point displacement sensor in the linear array measures the maximum signal value of the "radial displacement pulse wave." This indicates that the point displacement sensor is located above the location of the blood vessel. In other words, the first measurement position has been found, and the subsequent step 360 can be directly performed.

[0117] If a "surface array" displacement sensor is used, the steps of scanning along the X and Y axes to find the point of maximum signal (i.e., the starting position and the first measurement position) can be omitted. The "surface array" displacement sensor is placed directly above the part to be measured 160. The point displacement sensor in the "surface array" is observed to detect the maximum signal of the "radial displacement pulse wave." The "measurement depth" with the best noise level is then found, indicating that the point displacement sensor is located at the aforementioned second measurement position. Therefore, the measurement signal obtained from this point displacement sensor can be used for various subsequent applications. Thus, if the radial displacement pulse wave measurement device 100 uses a "surface array" or "linear array" displacement sensor, the need to scan the displacement control module 140 can be selected as required.

[0118] As described above, the cooperation between the airbag 110 and the pressure control module 120 allows control over the Z-axis compression depth of the airbag 110 onto the test area 160, enabling the displacement sensing module 130 to find a pulse wave measurement depth with better noise reduction on the Z-axis. With the airbag 110 already compressed onto the test area 160, the scanning position control module 140 allows the displacement sensing module 130 to find a pulse wave measurement position with better noise reduction on the XY plane. Therefore, the radial displacement pulse wave measurement device 100 can easily find a measurement position with a better noise reduction ratio for the radial displacement pulse wave within the test area 160 of the subject, thereby obtaining a better radial displacement pulse wave signal. [Waveform Analysis of Pulse Wave Variation with Pressure]

[0119] Figure 4 is a schematic diagram illustrating the waveform changes of vascular volume pulse wave and radial displacement pulse wave with pressure and time according to an embodiment of the present disclosure. In Figure 4, the horizontal axis is the time axis, and the vertical axis is divided into four segments, from top to bottom: valve, pump, pressure, and depth. The curve of the uppermost "valve" segment shows the constantly changing on / off state of the valve. The curve of the "pump" segment shows the constantly changing on / off state of the pump. The curve of the "pressure" segment shows the constantly changing pressure inside the airbag 110, that is, the "vascular volume pulse wave" measured by the pressure sensor 122. The curve of the lowermost "depth" segment shows the constantly changing pressure depth of the airbag on and off the Z-axis of the tested part, that is, the "radial displacement pulse wave" measured by the displacement sensing module 130. Please refer to Figure 4 and Table 1 simultaneously. The waveform changes at different periods (t0-t1, t1-t2, t2-t3, t3-t4) on the time axis will be explained below.

[0120] Table 1: The relationship between each pressure and depth in Figure 4 and the "radial displacement pulse wave" signal.

[0121] During period I (t0-t1): the air valve is closed to stop deflation of the airbag 110, while the pump is open to allow air into the airbag 110, gradually increasing its pressure. During the gradual pressurization to P5, the signals of the vascular volume pulse wave and radial displacement pulse wave can be observed to appear, gradually increase, decrease, and finally disappear. Thus, the maximum pressure to be released from the airbag 110 can be determined to be P5. The operation during period I is a step that can be omitted; the internal pressure of the airbag can be directly adjusted, and the amplitude and depth of the radial displacement pulse wave can be captured to obtain the radial displacement pulse wave signal with the maximum signal-to-noise ratio.

[0122] During period II (t1-t2): At time t1, the pump is turned off to stop inflating the balloon 110, and the valve is opened to gradually deflate the balloon 110 until the pressure of the balloon 110 reaches P4 and the compression depth reaches D4. At this point, signals of the vascular volume pulse wave and radial displacement pulse wave begin to appear. The pressure of the balloon 110 is then gradually reduced until time t2, when the pressure of the balloon 110 reaches P3 and the compression depth reaches D3. At this time, the amplitude signal of the radial displacement pulse wave is at its maximum value (at this point, the amplitude signal of the vascular volume pulse wave is near its maximum value). This means the optimal balloon pressure for measuring the radial displacement pulse wave is P3 and the optimal compression depth is D3. At time t2, the valve is also turned off, and this state is maintained for a period of time to monitor and record the vascular volume pulse wave, radial displacement pulse wave, or both required for period III. Since the pressure P3 and the compression depth D3 required for the maximum amplitude signals of the vascular volume pulse wave (related to the change in vascular volume) and the radial displacement pulse wave (related to the change in vascular diameter) are not necessarily the same, the optimal pressure P3 and compression depth D3 to be maintained can be determined according to the measurement requirements at this stage.

[0123] During period III (t2-t3): During this period, the pressure of the balloon is maintained at P3 and the balloon depressurization depth is D3, and the required vascular volume pulse wave, radial displacement pulse wave, or both can be monitored and recorded.

[0124] During period IV (t3-t4): At time t3, after the monitoring and recording of period III have ended, the air valve is opened, allowing the airbag 110 to be gradually depressurized. When the pressure of the airbag 110 is P2 and the depressurization depth is D2, the amplitude signals of the vascular volume pulse wave and the radial displacement pulse wave disappear. Then, the airbag 110 is allowed to continue to depressurize until the pressure of the airbag 110 is zero, which is the end time of t4.

[0125] Comparing the vascular volume pulse wave in the "pressure" segment and the radial displacement pulse wave in the "depth" segment during period III (t2-t3), it can be seen that the radial displacement pulse wave waveform has more detail. Therefore, it can be used for more data analysis to obtain multiple related physiological indicators and be applied in a wider range of physiological monitoring fields. Examples will be given below. Methods for measuring blood pressure

[0126] Next, we will explain how to measure blood pressure. When measuring blood pressure, the measurement site 160 of the subject can be, for example, the radial artery on the inside of the wrist or the brachial artery on the inside of the upper arm near the elbow joint.

[0127] Figure 5 is a schematic diagram of the process for measuring blood pressure using the radial displacement pulse wave measuring device shown in Figure 1. After finding the measurement position of the "first measurement position" or "second measurement position" of the "radial displacement pulse wave" using the aforementioned method, the displacement sensing module 130 is aligned with the "first measurement position" or "second measurement position" to measure blood pressure. Although both "vascular volume pulse wave" and "radial displacement pulse wave" can be used to measure blood pressure, the signal of the "radial displacement pulse wave" is clearer than that of the "vascular volume pulse wave". Therefore, the following content will mainly use the "radial displacement pulse wave" as the primary basis for judgment.

[0128] Step 510 roughly corresponds to "Period I" in Figure 4 and Table 1. In step 510, the pressure control module 120 is used to gradually pressurize the inside of the airbag 110 to increase the internal pressure of the airbag 110 until the signal of radial displacement pulse wave amplitude appears and then disappears.

[0129] Step 520 roughly corresponds to the time t1-t2 in period II of Figure 4 and Table 1, starting when the pressure of the airbag 110 is P4 and the compression depth is D4, and ending when the pressure of the airbag 110 is P3 and the compression depth is D3 in period II. In step 520, the pressure control module 120 gradually reduces the internal pressure of the airbag 110. When the radial displacement pulse wave amplitude signal begins to appear again, after filtering out the dynamic signal of the vascular volume pulse wave of the pulse beat, the static DC signal of the vascular volume pulse wave obtained by the pressure sensor 122 of the pressure control module 120 is the internal pressure value (P4) of the airbag 110, which is the systolic pressure (P4) of the subject's blood vessels.

[0130] Step 530 roughly corresponds to the time t3-t4 during period IV in Figure 4 and Table 1, starting when the pressure of the airbag 110 is P3 and the compression depth is D3, and continuing until the pressure of the airbag 110 during period IV is P2 and the compression depth is D2. In step 530, the pressure control module 120 continues to gradually reduce the internal pressure of the airbag 110. When the radial displacement pulse wave amplitude signal begins to disappear again, after filtering out the dynamic signal of the vascular volume pulse wave of the pulse beat, the static DC signal of the vascular volume pulse wave obtained by the pressure sensor 122 of the pressure control module 120 is the internal pressure value (P2) of the airbag 110, which is the diastolic pressure (P2) of the subject's blood vessels. Heart rate variability [ (Heart Rate Variability; HRV) ] [Measurement and Application]

[0131] Figure 6A is an enlarged schematic diagram of the radial displacement pulse wave during period III (t2-t3) of Figure 4. In Figure 6A, since the peak positions of the radial displacement pulse wave are clearly identifiable, they can be used as analogous to the R-wave peak positions in a typical electrocardiogram to extract data on the RR interval (RRI). If the radial displacement pulse wave signal for one minute is extracted and the number of peak occurrences is counted, the heart rate per minute can be obtained. In Figure 6A, the interval between two adjacent peaks on the radial displacement pulse wave curve is used to represent the heart rate interval.

[0132] Heart rate variability refers to the temporal difference between heartbeat intervals. Under normal circumstances, heartbeats do not occur uniformly at constant intervals, but rather exhibit minute variations; these variations are called heart rate variability. Therefore, heart rate variability analysis is a method for measuring the degree of variation in the time intervals between consecutive heartbeats. When using the radial displacement pulse wave measuring device 100 described above to measure heart rate variability, a thinner area of ​​subcutaneous tissue (e.g., on the posterior aspect of the wrist bone, or its anterior and posterior positions, or the earlobe or auricular artery, or the hand artery, the sole of the foot, or the toes) can be selected as the measurement area 160 to locate the blood vessels within it, thereby obtaining a more prominent peak position of the radial displacement pulse wave.

[0133] Methods for analyzing heart rate variability can be divided into two types. The first is time-domain analysis, which typically uses continuously measured electrocardiogram waveforms to directly calculate and analyze the dispersion of the corresponding heartbeat intervals. Common examples include:

[0134] SDNN (Standard deviation of NN intervals): This term is typically used to calculate the standard deviation of the intervals between normal heartbeats over a 24-hour period; the unit is milliseconds (ms).

[0135] SDANN (Standard deviation of the average NN intervals): Typically, the average heart rate interval is calculated first, then the standard deviation of the average interval is calculated, using five-minute intervals as the unit; the unit is milliseconds.

[0136] The following uses SDNN as an example for a more detailed explanation. SDNN is a measure of the overall activation of the autonomic nervous system, that is, the sum of the activation of the sympathetic and parasympathetic nervous systems, which can represent the ability of the autonomic nervous system to regulate bodily processes. SDNN is the standard deviation of RRI over the measurement time range. Since each RRI is not necessarily the same, the unit of SDNN is milliseconds (ms). The standard deviation of RRI describes the degree of dispersion of each RRI around its mean. The greater the dispersion, the larger the standard deviation. Conversely, if all RRI measurements are the same, the standard deviation of RRI will be 0. After calculating all RRIs from the HRV record, the relationship between the inter-heartbeat RRI and time can be obtained as shown in Figure 6B. SDNN can be calculated using the following equations (1) and (2). (1) (2) RRi is the i-th RRI, N is the number of all measured RRIs, and is the average of all RRIs. i is a positive integer.

[0137] The second method is frequency domain analysis, which uses discrete Fourier transform to convert the time series of heart rate intervals into the frequency domain, representing it as power spectral density or spectral distribution, as shown in Figure 6C. Spectral analysis of heart rate variability signals typically requires stable recordings of 200 to 500 consecutive RRIs, thus requiring several minutes of recording time. Typical RRI spectral frequencies appear below 1 Hz; for example, some RRI spectral peaks can be found in the 0-0.4 Hz range, including the ultra-low frequency region (ULF: ≤0.003 Hz), the extremely low frequency region (VLF: 0.0033–0.04 Hz), the low frequency region (LF: 0.04–0.15 Hz), and the high frequency region (HF: 0.15–0.40 Hz). The high-frequency region typically reflects the activity of the parasympathetic nervous system, while the low-frequency region is regulated by both the sympathetic and parasympathetic nervous systems. The ratio of high frequency to low frequency reflects the balance between the activity of the sympathetic and parasympathetic nervous systems. [Pulse velocity] [ (Pulse Wave Velocity; PWV) ] [Measurement Method]

[0138] Pulse wave velocity (PWV) refers to the speed at which the pulsation of arterial blood travels through blood vessels. This pulsation is caused by the pressure waves generated when the heart's ventricles contract, which propagate along the arterial system. Therefore, pulse wave velocity can reflect the elasticity and degree of arterial stiffness. Pulse wave velocity is inversely proportional to the viscoelasticity of the blood vessel wall; that is, the stiffer the artery, the faster the pulse wave velocity, and the more flexible the artery, the slower the pulse wave velocity.

[0139] The interpretation of pulse wave velocity varies depending on age, gender, disease, and risk factors. Generally, a normal aortic pulse wave velocity is approximately 5-7 m / s, while a velocity higher than 10 m / s indicates significant arteriosclerosis. Pulse wave velocity is closely related to the incidence and mortality of cardiovascular diseases; therefore, it can serve as an important indicator for assessing cardiovascular risk and prognosis, including conditions such as coronary artery disease, arteriosclerosis, or connective tissue diseases.

[0140] The pulse wave velocity is mainly measured by simultaneously recording the pressure waveforms at two different locations in the arterial tree. These two locations include the "proximal" location near the heart and the "distal" location far from the heart. Since the waveforms of the proximal and distal locations are recorded simultaneously, the "time difference ΔT (= T2 - T1)" between the distal waveform and the proximal waveform can be directly measured. By measuring the "distance ΔD" from the "proximal" to the "distal", the pulse wave velocity can be calculated, as shown in equation (3) below. (3)

[0141] There are two methods for measuring the aforementioned "delay time ΔT". The first method uses two displacement sensing modules 130, and the second method uses an electrocardiogram and a displacement sensing module 130.

[0142] Figure 7A is a schematic diagram of simultaneously using two pulse wave measuring devices to measure pulse wave velocity according to an embodiment of the present disclosure. In Figure 7A, two radial displacement pulse wave measuring devices 100 are used directly to record the proximal radial displacement pulse wave and the distal radial displacement pulse wave "simultaneously". The "delay time ΔT" between the troughs or between the peaks of the proximal and distal radial displacement pulse waves can be directly measured. Figure 7A shows the "delay time ΔT" between the troughs. If either of the two radial displacement pulse wave measuring devices 100 can be used in a way that allows the displacement sensing module 130 to be "manually" aligned with the part to be measured 160, then the scanning position control module 140 can be omitted. Only the airbag 110, the pressure control module 120, the displacement sensing module 130, and the calculation unit 150 are required in the radial displacement pulse wave measuring device 100. Furthermore, the two radial displacement pulse wave measuring devices 100 mentioned above can also share a single calculation unit 150, so one of the calculation units 150 can be omitted.

[0143] Figure 7B is a schematic diagram of measuring pulse wave velocity using electrocardiogram (ECG) assistance according to one embodiment of this disclosure. In Figure 7B, the peak of the "R wave" in the ECG is used to "time-match" the proximal and distal pulse waves. In the upper part (I) of Figure 7B, the delay time of the trough of the proximal radial displacement pulse wave relative to the peak of the "R wave" in the ECG is T1. In the lower part (II) of Figure 7A, the delay time of the trough of the distal radial displacement pulse wave relative to the peak of the "R wave" in the ECG is T2. The time difference between T1 and T2 is the "delay time ΔT". The "delay time ΔT" measured by the above two methods is the pulse transit time (PTT).

[0144] The distance ΔD between the "proximal" and "distal" ends can be directly measured using a flexible measuring tape between the two measurement points. The "proximal" and "distal" ends can be, for example, the carotid artery, femoral artery, brachial artery, radial artery, ankle artery, finger artery, or posterior tibial artery, with the measurement locations set according to the measurement requirements. Different combinations of "proximal" and "distal" ends can yield different pulse wave velocities.

[0145] Figure 7C is a flowchart of the pulse wave velocity measurement method using the method shown in Figure 7A.

[0146] In step 710, a radial displacement pulse wave measuring device 100 is placed at the first measuring position of the "proximal" artery, and the radial displacement pulse wave of the artery at the first measuring position is captured automatically or manually, according to the operation process of Figure 3A or Figure 3B.

[0147] In step 710, a radial displacement pulse wave measuring device 100 is placed at the second measuring position of the "distal" artery, and the radial displacement pulse wave of the artery at the second measuring position is captured automatically or manually, according to the operation procedure of Figure 3A or Figure 3B.

[0148] In step 730, the radial displacement pulse wave signal of the blood vessel obtained in steps 710 and 720 is simultaneously acquired to obtain the "delay time ΔT" of one pulse wave. Step 730 can be repeated multiple times over a period of time to obtain the successive "delay time ΔTi" of each pulse wave during this period, which is the successive pulse wave conduction time PTTi.

[0149] In step 740, the distance ΔD between the first measurement position and the second measurement position is measured. The method for measuring the distance ΔD can, for example, use different displacement sensors such as point-type, line-type arrays, or area-type arrays. When using a point-type displacement sensor, the distance ΔD can be obtained by measuring the length between two point-type displacement sensors placed at the first and second measurement positions using a measuring tape.

[0150] According to some embodiments, when using linear or planar photoelectric displacement sensors, only one photoelectric displacement sensor is needed. Two non-adjacent sensing units of the photoelectric displacement sensor, with a known distance between them, can simultaneously measure the radial displacement pulse waves at two locations. Since the measurement signal of the photoelectric displacement sensor is typically laser light, by covering the first and second measurement positions with the scanning range of the photoelectric displacement sensor, the distance between the first and second measurement positions within the scanning range can be estimated using the two non-adjacent sensing units of the photoelectric displacement sensor with a known distance and simple geometric proportions.

[0151] In step 750, the successive pulse wave conduction velocity (ΔD / ΔTi = ΔD / PTTi) is calculated based on the successive pulse wave conduction time PTTi obtained in step 730 and the distance ΔD obtained in step 740. [Continuous measurement of blood pressure]

[0152] Currently, commonly used cuff blood pressure monitors on the market determine systolic and diastolic blood pressure by detecting the pulse wave of blood vessel volume. While convenient to use, these measurements are inaccurate and cannot provide real-time blood pressure monitoring. Furthermore, wearable continuous blood pressure monitors typically use the correlation between pulse wave transit time and blood pressure, employing the Bramwell-Hill formula to estimate blood pressure. However, previous methods using the Bramwell-Hill formula to calculate continuous blood pressure suffer from inaccuracies in estimating the instantaneous vessel diameter and insufficient sensitivity in pulse wave measurement, leading to errors in pulse wave transit time calculations. Consequently, the continuous blood pressure calculated using the Bramwell-Hill formula is also inaccurate. Therefore, this invention discloses an embodiment of a continuous blood pressure measurement device that improves the accuracy of vessel diameter measurement and increases the sensitivity of pulse wave measurement, thereby improving the measurement accuracy of wearable continuous blood pressure monitors.

[0153] The Bramwell-Hill equation is a mathematical model describing the relationship between changes in vessel diameter and pulse wave velocity (PWV). This equation is a modification of the Moens-Korteweg equation, taking into account the decrease in arterial compliance with increasing pressure and the increase in volume with increasing pressure (arterial dilation). The Bramwell-Hill equation is shown in equation (4) below: (4) Where ΔP is the change in blood pressure, ρ is the blood density, ΔD is the distance between the first and second measurement positions in the above pulse wave velocity measurement, PTT is the pulse wave propagation time from the first to the second measurement position, ΔR is the change in the diameter of the artery at the first or second measurement position on the wrist as the baseline, and R is the diameter of the artery at the first or second measurement position on the wrist as the baseline. Therefore, (ΔD / PTT) is the pulse wave velocity (PWV).

[0154] Therefore, the ΔRi of each pulse wave can be measured using a displacement sensor, and the PWVi of each pulse wave can be measured using a pulse wave velocity measurement method. The ΔPi of each pulse wave can then be estimated using the Bramwell-Hill formula, thus achieving continuous blood pressure measurement. The method for continuous blood pressure measurement is detailed below.

[0155] Figure 8 is a flowchart of the continuous blood pressure measurement method.

[0156] In step 810, the initial diastolic pressure and initial systolic pressure are measured first. As described in the aforementioned "Blood Pressure Measurement Method" section, the initial diastolic pressure P2 and initial systolic pressure P4 of the subject are measured. The first compression depth D2 of the balloon 110 on the test area 160 is also measured at the initial diastolic pressure P2; and the second compression depth D4 of the balloon 110 on the test area 160 is measured at the initial systolic pressure P4, as shown in Figure 4 and Table 1. The vessel diameter R can be obtained from the difference between the first and second compression depths (D4-D2), so the vessel diameter is R = (D4-D2).

[0157] In step 820, the vessel diameter and the change in vessel diameter are calculated. Since Figure 6A shows the waveform of the radial displacement pulse wave of the vessel over time, the difference between the peak position (R2) and the trough position (R1) of each radial displacement pulse wave is the change in vessel diameter Δ(R) caused by each heartbeat.

[0158] In step 830, the pulse wave velocity (PWV) of each pulse wave is measured in accordance with the "Pulse Wave Measurement Method" section above.

[0159] In step 840, using the changes in blood vessel diameter ΔR, blood vessel diameter R, and pulse wave velocity PWV obtained above, and after obtaining the blood density of the subject, the Bramwell-Hill formula is used to calculate the changes in blood pressure ΔP.

[0160] In step 850, the instantaneous diastolic pressure (P2+ΔP) and instantaneous systolic pressure (P4+ΔP) can be obtained by using the initial diastolic pressure P2 and initial systolic pressure P4 measured in step 810, and the blood pressure change ΔP obtained in step 840.

[0161] Next, steps 820 to 850 are repeated for a period of time. This allows for highly accurate continuous measurement of blood pressure over a given period, achieving the goal of continuous blood pressure monitoring.

[0162] As disclosed above, through the combined design of the airbag, pressure control module, and displacement sensing module, the radial displacement pulse wave measurement device provided in this disclosure can directly measure the waveform of the "vascular radial displacement pulse wave." Compared to traditional pressure pulse wave measurement methods, this direct measurement method can provide more accurate results.

[0163] Furthermore, the radial displacement pulse wave measurement device boasts a measurement accuracy of less than 100 micrometers, thus providing detailed pulse wave information such as waveform shape, amplitude, and temporal characteristics. This high-precision measurement is invaluable for various pulse wave analysis applications. Besides measuring common parameters such as blood pressure, heart rate variability, and pulse wave velocity, the radial displacement pulse wave measurement device can be used for many other analytical applications. For example, it can be used to assess the degree of arteriosclerosis, detect vascular elasticity, monitor cardiovascular disease risk, and study hemodynamics. This multifunctional application potential makes the aforementioned radial displacement pulse wave measurement device widely applicable in the medical and biomedical fields.

[0164] Furthermore, using the aforementioned radial displacement pulse wave measurement device is a non-invasive method for measuring pulse waves. Therefore, it allows for convenient real-time monitoring of pulse wave changes in the subject, providing immediate measurement results and waveforms. The wearable design further facilitates long-term, continuous monitoring of the subject's pulse wave, yielding stable results. This is highly valuable for physicians and researchers, enabling them to better understand the subject's cardiovascular condition and make appropriate diagnostic and treatment decisions, thus providing better personalized medicine.

[0165] In summary, the aforementioned radial displacement pulse wave measurement device offers advantages such as direct measurement of vascular radial displacement pulse waves, high accuracy, versatility in analytical applications, non-invasiveness, and real-time monitoring. These advantages enable its widespread application in cardiovascular and biomedical fields.

[0166] 100: Measurement device for radial displacement pulse wave 110: Airbag 110a: Measurement Department 112: Transparent Window 114:Contact Department 120: Pressure Control Module 122: Pressure sensor 124: Pressure Adjustment Module 130: Displacement sensing module 130a: Transmit signal 130b: Reflected signal 132: Launcher 134: Receiver 136: Filter 140: Scanning Position Control Module 150: Computing Unit 151: Power Module 152: Memory Module 153: Communication Module 154: Operation Module 155: Display Module 156: Processing Module 157: Control Module 158: Analysis Module 160: Part to be tested 200: Wearable Department 210: Hard outer layer 212: furthest point 220: Soft inner layer 230: Outer shell 232: Transparent Part 240: Limbs 250: Artery 305, 310, 320, 330a, 330c, 340a, 340c, 350a, 360, 370, 510, 520, 530, 710, 720, 730, 740, 750, 810, 820, 830, 840, 850: Steps D1, D2, D3, D4, D5: Depth MD: Distance P1, P2, P3, P4, P5: Pressure R:R wave R1: Valley R2: Peak T1: Delay time of the proximal radial displacement pulse wave T2: Delay time of distal radial displacement pulse wave ΔT: Delay time difference

Claims

1. A method for optimizing the measurement conditions of radial displacement pulse wave of a blood vessel, used to find the optimal measurement conditions of an artery in a test part of a subject, the method comprising: providing a measurement device for radial displacement pulse wave of a blood vessel, comprising a pressure sensor for measuring a volumetric pulse wave of the artery and a displacement sensing module for measuring a radial displacement pulse wave of the artery; placing an airbag on the test part to apply pressure to the test part; using a pressure adjustment module to gradually change the internal pressure of the airbag to gradually change the downward pressure of the airbag on the test part, and simultaneously using the pressure sensor to monitor the internal pressure of the airbag to measure the volumetric pulse wave of the artery to find a first maximum amplitude signal of the volumetric pulse wave; when the first maximum amplitude signal of the volumetric pulse wave is measured, setting the pressure of the airbag measured by the pressure sensor as a first pressure; While maintaining the first pressure of the airbag, a displacement sensing module performs a first ranging scan on the surface of the test area along a direction substantially perpendicular to the artery's direction to find a second maximum amplitude signal of the radial displacement pulse wave of the blood vessel; when the second maximum amplitude signal of the radial displacement pulse wave of the blood vessel is measured, the corresponding location is set as a first measurement position, which is the location of the artery; the displacement sensing module is kept at the first measurement position, and the pressure adjustment module is used to gradually change the internal pressure of the airbag, while the pressure sensor is used to monitor the internal pressure of the airbag and the displacement sensing module is used to monitor the signal of the radial displacement pulse wave of the artery to find a third maximum amplitude signal of the radial displacement pulse wave of the blood vessel; and when the third maximum amplitude signal of the radial displacement pulse wave of the blood vessel is measured, the corresponding internal pressure of the airbag and the depth of the airbag's compression on the test area are set as the measurement conditions for the radial displacement pulse wave of the artery.

2. The method for optimizing the measurement conditions of radial displacement pulse wave of blood vessels as described in claim 1 further includes: maintaining the measurement conditions determined by the third maximum amplitude signal under pressure, allowing the displacement sensing module to perform a second ranging scan along the direction of the artery until a local maximum signal of the radial displacement pulse wave of blood vessels is found, and setting its position as a second measurement position to replace the first measurement position as the final measurement position.

3. The method for optimizing the measurement conditions of radial displacement pulse waves of blood vessels as described in claim 1, wherein the displacement sensing module used includes a filter to remove noise doped into the measurement signal.

4. A method for analyzing heart rate variability, comprising: using a measurement condition optimization method as described in claim 1 or 2 to obtain a measurement location and corresponding measurement conditions; measuring the radial displacement pulse wave of the blood vessel at the measurement location under the measurement conditions to obtain continuous waveform data within a preset time interval; extracting the time intervals of a plurality of adjacent peaks from the continuous waveform data to form a plurality of heartbeat intervals; and performing time-domain analysis or frequency-domain analysis on these heartbeat intervals to generate at least one heart rate variability index.

5. The method for analyzing heart rate variability as described in claim 4, wherein the time-domain analysis includes calculating the standard deviation of the heart rate intervals.

6. The method for analyzing heart rate variability as described in claim 4, wherein the frequency domain analysis includes performing a frequency domain transformation on the heartbeat intervals to obtain a spectral distribution.

7. The method for analyzing heart rate variability as described in claim 4 further includes calculating the number of peak occurrences within the preset time interval from the continuous waveform data to obtain the heart rate within the preset time interval.

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