Transcutaneous Photoplethysmography

Abstract

The present invention discloses a reflectance type PPG-based physiological sensing system with a close proximity triangulation approach toward robustly measuring several physiological parameters including, but is not limited to, heart rate, breathing rate, blood oxygen saturation and pulse wave velocity.

Claims

1. A wearable device to determine at least one physiological parameter by way of close-proximity triangulation photoplethysmography to be worn against the user's skin, comprising a plurality of measurement islands including, but not limited to; optical sensing module(s), electronic embodiment(s) for measuring a signal, a given the spatial arrangement of said measurement islands.

2. The wearable device of claim 1 where said optical sensing module(s) comprises one or more light-emitting diode(s) and one or more light-sensitive component.

3. The process of claims 1 and 2 to determine at least one physiological parameter by way of close-proximity triangulation photoplethysmography comprising; where said optical sensing module comprises one or more light-emitting diode(s) and one or more light-sensitive component(s), where the measurement islands measure pulse wave characteristics including, but not limited to, velocity, direction and magnification of the wave phenomena (such as pulse wave, Mayer waves and motion artifacts), including electronic embodiments for measuring a signal, where the amplified and conditioned signal(s) is digitized by an analog to digital converter (ADC), where a microprocessor is employed to algorithmically distinguish between the biological waveforms and is used to store to digital signal.

4. The process of claims 1 to 3 where a microprocessor is used in conjunction with at least three signal modules to algorithmically separate and determine the speed, direction and magnitude of different biological waves, given the spatial arrangement of said measurement island(s); including an electronic component to analyze the timing of the PPG peaks and PPG characteristics between the respective measurement islands, including an algorithm to identify common features and/or align the raw features of the signals from different measurement islands to analyze the speed of the biological waves, as the distances between the measurement islands is known, where the motion compensated, decomposition of the waveforms including, but not limited to, the pulse wave, motion artifacts and Mayer waves, allows for robust measurement of the physiological parameters, where close-proximity triangulation PPG involves simultaneous and/or sequential PPG measurements at the individual sensor islands.

5. Where said measurement islands of claims 1 to 4 are spatially arranged in a configuration including, but not limited to, a triangular formation.

6. The process of claims 1 to 4 for determining a number of physiological parameters including, but not limited to, heart rate, heart rate variability, respiration rate, blood oxygen saturation and pulse wave velocity.

7. The process of claims 1 to 4 whereby the distance and illumination level of the respective measurement islands prevents interference with the light detectors on a separate measurement island.

8. Including embodiments of claims 1 to 4 where the plurality of the light source(s) of a single measurement island are of different wavelengths from the two light sources and are programmed to sequentially emit light, and then the light detector subsequently detects the reflected light.

9. Including embodiments of claims 1 to 4 where the adjustment parameters are adjusted/controlled, including, but not limited to; embodiments where the light source intensity is adjusted, embodiments where signal amplification and/or signal conditioning parameters are adjusted, embodiments where digitized signal values obtained by the microprocessor can be used to readjust said signal amplitude and signal conditioning parameters.

10. A process of claims 1 to 4 where the amplified and/or conditioned digital signal is stored on memory and/or communicated to peripheral electronics by a communication module.

11. A wearable device of claims 1 to 4 that transmits the motion compensated physiological signal to a mobile electronic device, such as a mobile phone or personal computer.

12. The wearable device of claims 1 to 4 with the means to transmit the physiological data wirelessly to a platform where said data can be stored or processed on a server, analyzed and viewed on client computing platforms, including but not limited to mobile computing devices, home computers or a wearable electronic device.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0014] The accompanying figures, where alike reference numerals refer to identical or functionally similar elements throughout the separate views, and which together with the detailed description below are incorporated in and form part of the specification, serve to further illustrate various embodiments of, and to explain principles in accordance with, the present invention.

[0015] The present invention is described by way of an exemplary embodiment with reference to the accompanying representations, not drawn to any scale, in which:

[0016] FIG. 0.1 is a conceptual illustration of the exemplary embodiment of the tPPG-based physiological sensing system comprising three measurement islands (2) (with each island consisting of a light detector (1) and two light sources (3) on either side of the light detector (1)) arranged to form the nodes of an equilateral triangle of a given size (4).

[0017] FIG. 0.2 is a conceptual illustration of some of the types of measurement islands (2).

[0018] FIG. 0.2A illustrates a measurement island (2) consisting of a light detector (1) and two light sources (3) (able to transmit similar or different wavelengths) on either side of the light detector.

[0019] FIG. 0.2B illustrates a measurement island (2) consisting of a light detector (1) and one light source (3) next to the light detector (1).

[0020] FIG. 0.2C illustrates a measurement island (2) consisting of a light detector (1) and one monolithic light source (5) next to the light detector (1).

[0021] FIG. 0.3 is a conceptual illustration of the interaction of the electronic components of a single optical measurement island (2) and peripheral electronics.

[0022] FIG. 0.4 is a conceptual illustration of the electronic components comprising the preferred embodiment of the complete optical sensing module.

[0023] FIG. 0.5 illustrates a basic embodiment of the invention in the context of mobile and internet technologies.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] The following detailed description and appended drawings describe and illustrate various aspects of the present invention. The descriptions, embodiments and figures are not intended to limit the scope of the invention in any way.

[0025] FIG. 0.1 is a conceptual illustration of the exemplary embodiment of the tPPG-based physiological sensing system comprising three measurement islands (2) (with each island consisting of a light detector (1) and two light sources (3) on either side of the light detector) arranged to form the nodes of an equilateral triangle. The distance (4) between measurement islands (2) is as such that the light sources (3) of the respective measurement islands does not interfere with the light detectors (1) of the respective measurement islands (2). There might however still exist minor light contaminations between the respective sensing islands that can be compensated for analytically/mathematically. The respective measurement islands (2) is used to measure the blood pulse wave characteristics such as velocity and direction of the wave by analyzing the timing of the PPG peaks and PPG characteristics between the respective measurement islands. The PPG peak time at the three measurement islands can, for instance, be used to calculate the speed of wave propagation, as the distance (4) between the measurement islands (2) is known.

[0026] FIG. 0.2 is a conceptual illustration of some of the types of measurement islands (2). While many different measurement island configurations are possible, three of the types of measurement islands are briefly discussed.

[0027] FIG. 0.2A illustrates a measurement island (2) consisting of a light detector (1) and two light sources (3) (able to transmit similar or different wavelengths) on either side of the light detector. In the case where the two light sources (3) are of the same wavelength, the two light sources are programmed to simultaneously emit light, and the light detector (1) such as a photodiode or phototransistor then subsequently detects the reflected light coming back from the skin. However, in the case where the two light sources (3) are of different wavelengths, the two light sources are programmed to sequentially emit light, and the light detector (1) then subsequently detects the reflected light.

[0028] FIG. 0.2B is the simplest measurement island configuration where a single light source (3) transmits a specific wavelength into the skin and the light detector (1) measures the reflected light.

[0029] FIG. 0.2C illustrates a similar methodology and configuration as in FIG. 2A, but in this case two different wavelengths are encapsulated into a single monolithic light source (5).

[0030] FIG. 0.3 conceptually illustrates the electronic components involved for a single measurement island (2) with peripheral electronics included. A microprocessor (9) instructs a signal module (7) by adjusting several adjustment parameters (8) (containing parameters for intensity adjustment (6) and signal amplification & signal conditioning (12)) that affects the light source (3) intensity as well as the signal amplification and conditioning measured by the light sensor/detector (1). The amplified and conditioned signal is then digitized by an analog to digital converter (ADC) (13). Subsequently the digitized values are pushed to a microprocessor (9) to store the digitized signals on memory (11) and/or communicate it to peripheral electronics by a communication module (10). The communication module can either be wired or wireless. In addition, digitized signal values obtained by the microprocessor can be used to readjust the adjustment parameters (8) in order to obtain a signal with maximum resolution and the least amount of noise.

[0031] FIG. 0.4 depicts the same configuration as in FIG. 3, but shows that multiple measurement islands (2) can be coupled (14) to a single microprocessor, storage and communication module. In this case the preferred embodiment is displayed with three islands present.

[0032] FIG. 0.5 is a schematic illustration of a wearable device (15) for obtaining physiological parameters of a subject, which in this embodiment may be a human, but could also be an animal or other organism or process. The physiological sensors are incorporated into a band, which contacts the skin and may be worn on parts of the body including, but not limited to, the wrist, forearm and upper arm. The device optionally contains a display unit and is capable of transmitting data to a mobile device, such as a personal computer (16), mobile phone (17) and/or the Internet. The data may be stored (18) and further processed on a server (19) for future use and can be viewed on a computer platform such as a personal computer, mobile phone and/or a wearable device.