WO2017209696A1

WO2017209696A1 - Wearable sensor for human pulse diagnosis

Info

Publication number: WO2017209696A1
Application number: PCT/SG2017/050283
Authority: WO
Inventors: Dejian Huang; Woon Loong Daniel LEONG
Original assignee: National University Of Singapore
Priority date: 2016-06-02
Filing date: 2017-06-02
Publication date: 2017-12-07

Abstract

The invention relates to a wearable sensor for human pulse diagnosis, a kit of parts for a sensor system for human pulse diagnosis, and a method for human pulse diagnosis. The wearable sensor for human pulse diagnosis comprises a plurality of broadband light sources, each broadband light source configured for emitting visible green light; a plurality of light detectors, each light detector configured for detecting, in use, a reflected light signal originating from an associated one of the broadband light sources; and an interface for transferring data representative of the detected reflected light signals for analyzing and displaying of the data. Preferably, the broadband light sources are aligned on a single line such that, in use, the broadband light sources are positionable along the radial artery of the human at locations corresponding to the "cun, "guan" and "chi" positions at the wrist according to traditional Chinese medicine.

Description

WEARABLE SENSOR FOR HUMAN PULSE DIAGNOSIS

FIELD OF INVENTION

The present invention relates broadly to wearable sensor for human pulse diagnosis, to a kit of parts for a sensor system for human pulse diagnosis, and to a method for human pulse diagnosis.

BACKGROUND

A person's pulse is an important parameter in the assessment of that person's physical/physiological state. For example, in a traditional Chinese medicine (TCM) diagnosis of pulse, a TCM practitioner would use his fingertips to feel the radial arteries pulse of patients to determine their health conditions. A reference used by the TCM practitioner is typically subjective to the practitioner him/herself. Generally, according to the "Yellow Emperor's Classis of Internal Medicine", the diagnosis could only be done in the early morning before eating in order to be accurate. Since it is all based on the practioner's subjective feeling of the pulse, pulse diagnosis is a very difficult art to master. Only those highly experienced and "senior" TCM practitioners may know the art. In fact, modern day TCM practitioners are gradually doing away with this ancient diagnosis as they adopt western diagnostic methods. As such this unique way of diagnosis may be lost.

It has been hypothesized that if one can read the pulse pattern by an electronic device that translates the pulse signal into data, one would be able to have an unbiased dataset for analysis. From the measured pattern, one may be able to draw some useful information that can be correlated to a person's health status with some accuracy and reproducibility, e.g. against a consistent standard reference pulse wave.

Polymer-based thin film flexible tactile sensors for TCM pulse measurement have been proposed in Hong-Jie Tseng et al {Sensors 2013, 13, 14777-14796; doi: 10.3390/sl31114777). This sensor is based on piezoelectric effect to sense the pressure from the blood vessel. However, the propose device suffers from a complex structure which may not be suitable for development into wearable versions, as is desirable for most practical applications.

CN2857814Y describes an optical sensor with a light source of 950 nm (infra-red) wavelength of 950nm, to which oxyhemoglobin and hemoglobin is very sensitive, so that one can capture fluctuations of the arterial wall. A pressure sensor is additionally used. However, the measurement of the fluctuations of the arterial wall requires precision positioning of the sensor relative to the arterial wall, which may not be suitable for development into wearable versions, as is desirable for most practical applications. A pressure sensor is also sensitive to vibrations from a user's movements which reduces the signal to noise ratio of the device. Wang et al (IEEE Transactions On Instrumentation And Measurement, Vol. 64, No. 7, July 2015) use a light source operating at about 1000 nm (near infra-red, NIR). The photoelectric sensor is composed of a pair of optical emitter (NIR) and optical detector (phototransistor). The NIR source is chosen due to its ability to penetrate the skin and reflect information below the skin. The blood absorbs the NIR light, and the reflected light changes as the blood flow of the radial artery changes..

Chen et al (Sensors 2015, 15, 9899-9914; doi: 10.3390/s 150509899) use a narrow band and coherent red laser in an optical triangulation arrangement to measure the amplitude change on the surface of the skin of the test subject. However, the measurement of the amplitude change on the surface of the skin of the test subject requires precision positioning of the sensor relative to the arterial wall, which may not be suitable for development into wearable versions, as is desirable for most practical applications. Lasers are also costly and require additional optics to create a larger beam size. Another potential problem with using a laser light source is scintillation which can interfere with the readings.

Embodiments of the present invention seek to address at least one of the above problems.

SUMMARY

In accordance with a first aspect of the present invention, there is provided a wearable sensor for human pulse diagnosis comprising a plurality of broadband light sources, each broadband light source configured for emitting visible green light; a plurality of light detectors, each light detector configured for detecting, in use, a reflected light signal originating from an associated one of the broadband light sources; and an interface for transferring data representative of the detected reflected light signals for analyzing and displaying of the data.

In accordance with a second aspect of the present invention, there is provided a kit of parts for a sensor system for human pulse diagnosis comprising the wearable sensor of the first aspect; a digitizing module configured for digitizing the data from the wearable sensor; and a computer module configured for analyzing and displaying of the digitized data.

In accordance with a third aspect of the present invention, there is provided a method for human pulse diagnosis, the method comprising disposing a wearable sensor comprising a plurality of broadband light sources on the human's wrist, each broadband light source configured for emitting visible green light, the wearable sensor further comprising a plurality of light detectors; detecting a reflected light signal originating from an associated one of the broadband light sources using the respective light detectors; and transferring data representative of the detected reflected light signals for analyzing and displaying of the data. BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will be better understood and readily apparent to one of ordinary skill in the art from the following written description, by way of example only, and in conjunction with the drawings, in which:

Figure 1 (a) shows a photograph of a Tri-Pulse Optical Sensor according to an example embodiment.

Figure 1 (b) shows a photograph of the circuit board of a digitizing module for use in a sensor system according to an example embodiment.

Figure 2 shows a schematic diagram illustrating optical reflectance-based pulse sensing according to an example embodiment.

Figure 3 shows a photograph of an assembled kit of parts for a sensor system according to an example embodiment.

Figure 4 (a) shows a graph of pulse signals displayed by a sensor system according to an example embodiment.

Figure 4 (b) shows a graph of the frequency spectra of the pulse signals of Figure 4 (a).

Figure 5A shows a graph illustrating peak ratios of the right hand before and after breakfast displayed by a sensor system according to an example embodiment.

Figure 5B shows a graph illustrating peak ratios of the left hand before and after breakfast displayed by a sensor system according to an example embodiment.

Figure 5C shows a graph of the right hand pulse taken before breakfast displayed by a sensor system according to an example embodiment.

Figure 5E shows a graph of the right hand pulse taken before breakfast displayed by a sensor system according to an example embodiment.

Figure 5D shows a graph of the right hand pulse taken after breakfast displayed by a sensor system according to an example embodiment.

Figure 5F shows a graph of the left hand pulse after breakfast displayed by a sensor system according to an example embodiment.

Figure 6A shows a graph of right hand pulse of a male (age 50) with hyperglycemia after meal (blood glucose concentration 162 milligram per deciliter at the time of pulse measurement), displayed by a sensor system according to an example embodiment.

Figure 6B shows a graph of a right hand pulse of a male (age 50) with hyper glycemia after dinner with blood glucose concentration of 173 milligram per deciliter, displayed by a sensor system according to an example embodiment. Figure 6C shows the ratio of channel A2 maximum signal to that of AO maximum signal of the pulse signal shown in Figure 6A and 6B.

Figure 6D shows a table illustrating measuring blood glucose using a sensor system according to an example embodiment.

Figure 7 shows a flowchart illustrating a method for human pulse diagnosis according to an example embodiment.

DETAILED DESCRIPTION

Example embodiments described herein provide a Tri-Pulse Optical Sensor (3-POS) configured for measuring pulses along the radial artery in the wrist of a person at 3 locations corresponding to the "cun", "guan" and "chi" positions in TCM. The 3-POS sensor according to example embodiments is based on volume displacement plethysmography using a light emitting diode (LED) light source and photodetector. The sensor measurement is digitized and stored with a digital oscilloscope and analyzed using Fourier Transformation and other methods. The 3-POS according to example embodiments can advantageously be used to establish an optical sensor measurement baseline for TCM diagnostics.

A preferred embodiment includes an array of 3 LEDs arranged in 3-POS measurement layout in a wearable manner attached onto the wrist. LEDs can advantageously be manufactured in a small, flat package. For example, the OSRAM LG R971 green LED has a height of 0.9 mm. It is easily mounted on a flexible circuit board and worn against the skin.

The preferred embodiment of the 3-POS uses a broadband (for example, but not limited to, 30 nm full-width at half-maximum (FWHM)) with a peak wavelength of for example, but not limited to, 515 nm, which is visible green. This wavelength is readily absorbed by the blood in the vein to advantageously produce better signal to noise ratio compared to NIR light sources. More particularly, a shorter wavelength light source with higher absorption compared to NIR was found to have a larger change in the intensity of reflected light, resulting in higher sensitivity.

The example embodiments are simple in structure and can be wearable on a person's wrist.

In more detail, and as shown in Fig. 1 (a), the 3-POS 100 according to an example embodiment consists of 3 optical sensors 102, 104, 106 and is configured to measure heart pulses along the radial artery in the wrist at 3 locations corresponding to the "cun", "guan" and "chi" positions in traditional Chinese medicine. Each sensor 102, 104, 106 uses optical reflectance to monitor the volume displacement of the blood vessel 200 as blood flows through it, as shown in Fig. 2. In one embodiment the 3-POS 100 is placed in plastic case with wristband 112 (see Fig. 1 (c)) to secure on the wrist for positioning of the pulse measurements. There are several optical pulse sensors available in the market such as the Shimmer Optical Pulse Probe (http://www.shimmersensing.com/shop/shimmer-optical-pulse-probe) and Withings Pulse Ox (http://www2.withings.com/us/en/products/pulse/). The Pulse Sensor SEN- 11574 from Shimmer available off-the-shelf was used in this example embodiment. Three of such sensors 102, 104, 106 were integrated in to one device 100, as shown in Fig. 1 (a). Each sensor comprises an integrated pair of a light source e.g. 103 and associated detector e.g. 105. An off-the -shelf ICP 12 USB oscilloscope 110 (see Fig. 1 (b)) was used in this example embodiment due to being relatively low cost, readily available and relatively simple to integrate with the optical sensors 102, 104, 106.

As illustrated in Fig. 3, a notebook computer 300 for data storage and analysis completes the set up in this example embodiment. It will be appreciated that other computing devices may be used in different embodiments, such as, but not limited to, a smartphone.

The pulse signals from the 3-POS 100 is digitized by the digital oscilloscope 110 and sent via USB to the notebook computer 300. The computer 300 stores the data in an Excel file for analysis. To analyze the data, Fourier Transformation in Excel is used to break down the pulse signal e.g. 400 into its frequency components e.g. 402, as shown in Figs. 4a) and b). As will be appreciated by a person skilled in the art, Fourier Transform (FT) is an algorithm which converts a signal from the time domain to the frequency domain and vice versa. Since a pulse signal is the sum of different signals, each with its own amplitude and frequency, a FT is useful in decomposing the signal into its constituent frequencies and amplitudes. A Fast Fourier Transformation is an efficient and less complex way to calculate a discrete Fourier Transform.

In use, there are signal differences recorded by the 3-POS 100 at three adjacent points along the same vein at a person's wrist.

The present specification also discloses apparatus for implementing or performing the signal obtaining control operations, the signal processing/analyzing operations and the data displaying operations described herein. Such apparatus may be specially constructed for the required purposes, or may comprise a device selectively activated or reconfigured by a computer program stored in the device. Furthermore, one or more of the steps of the computer program may be performed in parallel rather than sequentially. Such a computer program may be stored on any computer readable medium. The computer readable medium may include storage devices such as magnetic or optical disks, memory chips, or other storage devices suitable for interfacing with a device. The computer readable medium may also include a hard- wired medium such as exemplified in the Internet system, or wireless medium such as exemplified in a mobile communication system. The computer program when loaded and executed on the device effectively results in an apparatus that implements the steps of the operation methods.

The invention may also be implemented as hardware modules. More particular, in the hardware sense, a module is a functional hardware unit designed for use with other components or modules. For example, a module may be implemented using discrete electronic components, or it can form a portion of an entire electronic circuit such as an Application Specific Integrated Circuit (ASIC). Numerous other possibilities exist. Those skilled in the art will appreciate that the system can also be implemented as a combination of hardware and software modules.

To demonstrate that the 3-POS 100 according to an example embodiment can detect the different pulses of the same person under different physical states, the pulse patterns of a person (female, age 15) were examined before and after breakfast. Specifically, Fig. 5 A shows a graph illustrating peak ratios of the right hand before and after breakfast. Fig. 5B shows a graph illustrating peak ratios of the left hand before and after breakfast. Fig 5C shows a graph of the right hand pulse taken before breakfast. Fig 5E shows a graph of the right hand pulse taken before breakfast. Fig. 5D shows a graph of the right hand pulse taken after breakfast. Fig. 5F shows a graph of the left hand pulse after breakfast.

From the data shown in Figs. 5A, B, one can see that the peak ratios of the FFT graph decreases consistently after every meal for both hands and for all three sensors, AO, Al, A2. This demonstrates that the 3-POS 100 according to the example embodiment can differentiate the subtle difference of pre and post prandial pulse patterns.. From the data shown in Figs. 5C, D and 5E, F, one can see that the amplitudes of both hands decrease after meals. This may be due to the fact that, after a meal, the heart pumps stronger and more blood passes through the arteries thus less light is reflected back to the sensor. Also, eating and digesting trigger the release of hormones that can increase the strength of the pulse In addition, there typically is a large influx of sugars from the meal that boost insulin levels, thus increasing pulse by preventing the relaxation of the heart's arteries that typically occurs after a meal.

One possible application of the device according to an example embodiment is to measure the blood glucose of diabetic patient. Fig. 6A shows the pulse patterns of the three channels (AO, Al, and A2) for a male (50) after meal with blood glucose (measured by glucometer) at 162 milligrams per deciliter, while the pulse patterns of the same person were measured after dinner with blood glucose concentration increased to 173 milligrams per deciliter. The ratio of the respective A2 and AO maximum values shows clear correlation with blood glucose concentration (see Fig. 6C and the table in Fig. 6D).

In one embodiments, a wearable sensor for human pulse diagnosis is provided, comprising a plurality of broadband light sources, each broadband light source configured for emitting visible green light; a plurality of light detectors, each light detector configured for detecting, in use, a reflected light signal originating from an associated one of the broadband light sources; and an interface for transferring data representative of the detected reflected light signals for analyzing and displaying of the data.

The broadband light sources may be aligned on a single line such that, in use, the broadband light sources are positionable along the radial artery of the human at locations corresponding to the "cun, "guan" and "chi" positions at the wrist according to traditional Chinese medicine. The plurality of broadband light sources and the light detectors may be configured for, in use, placement on the skin of the human.

Respective pairs of one detector and its associated broadband light source a may be formed integrally.

In one embodiment, a kit of parts for a sensor system for human pulse diagnosis is provided, comprising the wearable sensor of the above embodiment, a digitizing module configured for digitizing the data from the wearable sensor; and a computer module configured for analyzing and displaying of the digitized data.

The computer module may be configured for analyzing and displaying a waveform representing the human pulse based on the digitized data. The computer module may be configured for applying Fourier Forward Transform, FFT, processing to the digitized data. The computer module may be configured for determining peak ratios of FFT graphs of the respective reflected light signals.

The computer module may be configured for measuring blood glucose of the human based on the respective reflected light signals.

Fig. 7 shows a flowchart 700 illustrating a method for human pulse diagnosis according to an example embodiment. At step 702, a wearable sensor comprising a plurality of broadband light sources is disposed on the human's wrist, each broadband light source configured for emitting visible green light, the wearable sensor further comprising a plurality of light detectors. At step 704, a reflected light signal originating from an associated one of the broadband light sources is detected using the respective light detectors. At step 706, data representative of the detected reflected light signals is transferred for analyzing and displaying of the data.

The method may comprise positioning the broadband light sources along the radial artery of the human at locations corresponding to the "cun, "guan" and "chi" positions at the wrist according to traditional Chinese medicine.

The wearable sensor may be placed on the skin of the human.

The method may comprise digitizing data from the wearable, and analyzing and displaying of the digitized data. The method may comprise analyzing and displaying a waveform representing the human pulse based on the digitized data. The method may comprise applying Fourier Forward Transform, FFT, processing to the digitized data. The method may comprise determining peak ratios of FFT graphs of the respective reflected light signals.

The method may comprise measuring blood glucose of the human based on the respective reflected light signals.

Embodiments of the present invention may have one or more of the following features:

3 optical reflectance sensors - Simultaneously measures pulses along the "cun", "guan" and "chi" positions along the radial artery. Comparisons of the pulses at the 3 positions can be made simultaneously.

USB digital oscilloscope - Small, compact, easy to set up and operate on a notebook computer. Future versions will be able to operate from a smartphone for added portability. Fourier Transform Analysis - Spectral data from a Fourier Transformation reveal features in the pulses from the 3 positions.

Embodiments of the present invention can e.g. have applications in home based TCM diagnostics, online TCM consultation, etc.

It will be appreciated by a person skilled in the art that numerous variations and/or modifications may be made to the present invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects to be illustrative and not restrictive. Also, the invention includes any combination of features, in particular any combination of features in the patent claims, even if the feature or combination of features is not explicitly specified in the patent claims or the present embodiments.

Claims

1. A wearable sensor for human pulse diagnosis comprising:

a plurality of broadband light sources, each broadband light source configured for emitting visible green light;

a plurality of light detectors, each light detector configured for detecting, in use, a reflected light signal originating from an associated one of the broadband light sources; and an interface for transferring data representative of the detected reflected light signals for analyzing and displaying of the data.

2. The wearable sensor of claim 1, wherein the broadband light sources are aligned on a single line such that, in use, the broadband light sources are positionable along the radial artery of the human at locations corresponding to the "cun, "guan" and "chi" positions at the wrist according to traditional Chinese medicine.

3. The wearable sensor of claims 1 or 2, wherein the plurality of broadband light sources and the light detectors are configured for, in use, placement on the skin of the human.

4. The wearable sensor of any one of claims 1 to 3, wherein respective pairs of one detector and its associated broadband light source are formed integrally.

5. A kit of parts for a sensor system for human pulse diagnosis comprising:

the wearable sensor of any one of claims 1 to 5;

a digitizing module configured for digitizing the data from the wearable sensor; and a computer module configured for analyzing and displaying of the digitized data.

6. The kit of parts of claim 5, wherein the computer module is configured for analyzing and displaying a waveform representing the human pulse based on the digitized data.

7. The kit of parts of claim 6, wherein the computer module is configured for applying Fourier Forward Transform, FFT, processing to the digitized data.

8. The kit of parts of claim 7, wherein the computer module is configured for determining peak ratios of FFT graphs of the respective reflected light signals.

9. The kit of parts of any one of claims 5 to 8, wherein the computer module is configured for measuring blood glucose of the human based on the respective reflected light signals.

10. A method for human pulse diagnosis, the method comprising: disposing a wearable sensor comprising a plurality of broadband light sources on the human's wrist, each broadband light source configured for emitting visible green light, the wearable sensor further comprising a plurality of light detectors;

detecting a reflected light signal originating from an associated one of the broadband light sources using the respective light detectors; and

transferring data representative of the detected reflected light signals for analyzing and displaying of the data.

11. The method of claim 10, comprising positioning the broadband light sources along the radial artery of the human at locations corresponding to the "cun, "guan" and "chi" positions at the wrist according to traditional Chinese medicine.

12. The method of claims 10 or 11, wherein the wearable sensor is placed on the skin of the human.

13. The method of any one of claims 10 to 12, comprising digitizing data from the wearable, and analyzing and displaying of the digitized data.

14. The method of claim 13, comprising analyzing and displaying a waveform representing the human pulse based on the digitized data.

15. The method of claim 14, comprising applying Fourier Forward Transform, FFT, processing to the digitized data.

16. The method of claim 15, comprising determining peak ratios of FFT graphs of the respective reflected light signals.

17. The method of any one of claims 10 to 16, comprising measuring blood glucose of the human based on the respective reflected light signals.