WO2016193423A1 - Système et dispositif de détection portable - Google Patents

Système et dispositif de détection portable Download PDF

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Publication number
WO2016193423A1
WO2016193423A1 PCT/EP2016/062639 EP2016062639W WO2016193423A1 WO 2016193423 A1 WO2016193423 A1 WO 2016193423A1 EP 2016062639 W EP2016062639 W EP 2016062639W WO 2016193423 A1 WO2016193423 A1 WO 2016193423A1
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WIPO (PCT)
Prior art keywords
ppg
sensor
subject
lower limb
ecg
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PCT/EP2016/062639
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English (en)
Inventor
Guang-Zhong Yang
Benny Lo
Ching-Mei CHEN
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Sensixa Limited
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Publication of WO2016193423A1 publication Critical patent/WO2016193423A1/fr

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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/02—Detecting, measuring or recording pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography or electroauscultation; Heart catheters for measuring blood pressure
    • A61B5/021—Measuring pressure in heart or blood vessels
    • A61B5/02108—Measuring pressure in heart or blood vessels from analysis of pulse wave characteristics
    • A61B5/02125—Measuring pressure in heart or blood vessels from analysis of pulse wave characteristics of pulse wave propagation time
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/02—Detecting, measuring or recording pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography or electroauscultation; Heart catheters for measuring blood pressure
    • A61B5/024—Detecting, measuring or recording pulse rate or heart rate
    • A61B5/02438—Detecting, measuring or recording pulse rate or heart rate with portable devices, e.g. worn by the patient
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/68—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient
    • A61B5/6801—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient specially adapted to be attached to or worn on the body surface
    • A61B5/6813—Specially adapted to be attached to a specific body part
    • A61B5/6825—Hand
    • A61B5/6826—Finger
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/68—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient
    • A61B5/6801—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient specially adapted to be attached to or worn on the body surface
    • A61B5/6813—Specially adapted to be attached to a specific body part
    • A61B5/6829—Foot or ankle
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B2560/00—Constructional details of operational features of apparatus; Accessories for medical measuring apparatus
    • A61B2560/04—Constructional details of apparatus
    • A61B2560/0462—Apparatus with built-in sensors
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B2562/00—Details of sensors; Constructional details of sensor housings or probes; Accessories for sensors
    • A61B2562/04—Arrangements of multiple sensors of the same type
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/24—Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
    • A61B5/316—Modalities, i.e. specific diagnostic methods
    • A61B5/318—Heart-related electrical modalities, e.g. electrocardiography [ECG]
    • A61B5/332—Portable devices specially adapted therefor

Definitions

  • the present disclosure relates to a system and wearable device for analyzing blood flow in a subject, in particular to assess diabetic peripheral neuropathy (DPN) or arterial stiffness in the subject.
  • DPN diabetic peripheral neuropathy
  • Peripheral neuropathy occurs in a patient when the peripheral nerves have been ruptured. These nerve disruptions can lead to impairment of tactile perception, pain or undesired stings, peculiar changes in skin colour and blood pressure, weakness, muscle loss and pain, depending on the affected nerves.
  • the most common form of diabetic neuropathy is the peripheral sensorimotor neuropathy which affects the feet and worsens over time due to its negative impact on both the nervous and vascular systems. Patients also suffer deterioration in both temperature and vibratory response.
  • peripheral neuropathy Patients with peripheral neuropathy often are not aware of their condition, and many of the patients with peripheral neuropathy may not have any symptom.
  • the main complication of peripheral neuropathy is the diabetic foot. Typically about a fifth of hospital visits from diabetic patients are foot related making it the leading cause of hospital visits for diabetes.
  • Neuropathy leads to numbness due to disrupted blood flow to the limbs which in turn causes trauma (often unnoticeably) as well as joint deformity.
  • trauma often unnoticeably
  • sepsis can occur. Sepsis mainly affects the soles of the feet, which are most vulnerable to pressure during normal daily activities such as walking, running, standing etc. Further development of the sepsis can lead to ulcer development and could lead to complete amputation of the foot; a procedure which has a high mortality rate within the year of amputation. Early detection of DPN is therefore of high importance.
  • PPG photoplethysmography
  • PWV Pulse Wave Velocity
  • ABPI ankle brachial pressure index
  • brachial blood pressure the ratio between the systolic blood pressure of the ankle and upper arm
  • brachial blood pressure the ratio between the systolic blood pressure of the ankle and upper arm
  • ABPI measurement is collected using ultrasound and blood pressure cuffs.
  • ABPI has been widely used as a clinical diagnostic tool for assessing neuropathy.
  • a wearable device for assessing blood flow in a subject comprising a plurality of photoplethysmography (PPG) sensors comprising a first PPG sensor and a second PPG sensor, each sensor being arranged to carry out measurements indicative of blood flow in the subject, wherein the PPG sensors are disposed such that, when the device is worn on an upper or lower limb of the subject, the first PPG sensor is in contact with the upper or lower limb on which the device is worn, and the second PPG sensor is contactable by the other of the upper or lower limb of the subject.
  • PPG photoplethysmography
  • a PPG sensor comprises at least one light emitting device (LED) and at least one light receiving device.
  • LED light emitting device
  • Light emitted from the LED illuminates the skin and is reflected back from various structures beneath the skin. The reflected light is then detected by the light receiving device.
  • light from the LED may be transmitted through a portion of the subject's body, for example, through a finger, such that the transmitted light, rather than the reflected light, is detected by the photo-detector.
  • PPG waveform the time taken for the blood to flow from the heart to the location of the PPG sensor measurement location, known as the pulse arrival time (PAT), may be calculated.
  • the device is a wearable device that is capable of obtaining a PPG waveform using PPG sensors disposed to carry out measurements at locations on a subject's upper limb and lower limb.
  • Deviations in a pulse arrival time (PAT) between the lower limb location and upper limb location can be captured by comparing the PPG waveforms obtained at the first and second PPG sensors and used as a surrogate measure for detecting and assessing DPN or arterial stiffness.
  • a time difference between the arrival of corresponding pulses captured by the respective PPG sensors at the upper and lower limbs may be determined.
  • Arterial stiffness may also be determined which can occur as a result of biological aging and arteriosclerosis and which is associated with an increased risk of heart attack and stroke.
  • the claimed device may be worn by a subject, for example, in their home, and data from the wearable device may then be uploaded subsequent analysis and diagnosis, for example, by a medical professional at a later time. Obtaining these PPG measurements does not require the subject to visit a medical practitioner and so is a more convenient way of obtaining suitable measurements which may then be used to assess DPN or arterial stiffness.
  • PPG sensor Any suitable PPG sensor may be used.
  • the measurements indicative of blood flow may be a measure of light absorption. From the measurements indicative of blood flow a PPG waveform may be produced.
  • two PPG sensors are be used.
  • the first and second PPG sensors are disposed on opposite sides of the device such that, when worn, the first PPG sensor is directed towards the upper or lower limb on which the device is worn and the second PPG sensor is directed away from the upper or lower limb on which the device is worn.
  • a user may conveniently place the other of the upper or lower limb (i.e. the limb on which the device is not worn), for example, a finger, against the second PPG sensor to enable PPG measurements of the other of the upper or lower limb to be made.
  • the wearable device may comprise a band.
  • the PPG sensors may be disposed on opposite sides of the band.
  • the wearable device may comprise an item of clothing, for example, a glove, a sock or an insole.
  • the PPG sensors may be disposed on opposite sides of the item of clothing e.g.in the case of a glove or sock, for example, one PPG sensor may be disposed on the inside and one on the outside.
  • the PPG sensor disposed to carry out measurements indicative of blood flow in a subject's lower limb may be disposed to carry out measurements of the subject's lower leg, ankle, knee or foot, for example.
  • the PPG sensor disposed to carry out measurements indicative of blood flow in a subject's upper limb may be disposed to carry out measurements of the subject's arm, hand, finger or thumb, for example.
  • the device may further comprise an electrocardiogram (ECG) monitor for obtaining an electrocardiogram corresponding to the rhythm of the subject's heart.
  • ECG electrocardiogram
  • the ECG monitor and PPG sensors may be configured to carry out measurements simultaneously.
  • the ECG monitor may comprise a 1-lead ECG monitor.
  • the ECG monitor comprises a plurality of electrodes, for example, 2-10 electrodes, for example 2 or 3.
  • the ECG monitor comprises a first and second electrode wherein the first and second electrodes are disposed on opposite sides of the device such that, when worn, the first electrode is directed towards the upper or lower limb on which the device is worn and the second electrode is directed away from the upper or lower limb on which the device is worn.
  • the second electrode (which is directed away from the limb on which the device is worn), is provided sufficiently close to the second PPG sensor (which is also directed away from the limb on which the device is worn) such that the user may
  • the other of the upper or lower limb i.e. the limb on which the device is not worn
  • a finger against both the second electrode and the second PPG sensor at the same time.
  • the first electrode may be disposed such that, when the device is worn, the first electrode is in contact with the upper or lower limb on which the device is worn. For example, when the device is worn on the lower limb, the first electrode is disposed such that it is in contact with the lower limb. In this way, when a user places the other of the upper or lower limb (i.e. the limb on which the device is not worn) against the second electrode, the electrical circuit between the two electrodes is complete and an ECG measurement is captured.
  • the first PPG sensor and the first electrode When worn, the first PPG sensor and the first electrode may be in contact with the limb on which the device is worn, for example, by virtue of user manipulation of the device to place the first PPG sensor and electrode against the limb, or, for example, by the device being worn sufficiently close to the limb.
  • the wearable device may comprise a memory component for storing measurements made by the first and second PPG sensors and/or the or an ECG monitor.
  • the wearable device may comprise a processor for computing a PAT at the lower limb and a PAT at the upper limb based on the measurements made by the first and second PPG sensors.
  • the processor also uses measurement made by an ECG monitor to compute the pulse arrival time at the respective locations.
  • the PAT may be obtained by measuring the time delay from an ECG R-peak to a subsequent PPG pulse at the first or second PPG sensor.
  • the PAT obtained at the upper limb may be compared to that obtained at the lower limb and a difference between the two determined. This difference may be compared to known values to determine whether or not, and/or to what extent, arterial stiffness or DPN is present in the subject.
  • the wearable device may comprise a communication device for uploading data relating to the measurements made by the first and second PPG sensors and/or the or an ECG monitor and/or results from the or a processor to an external device.
  • the data may be transmitted via any suitable means, for example, wired or wireless communication techniques.
  • the external device may be an external computing or storage device.
  • the wearable device may also comprise a gait sensor for carrying out measurements indicative of a subject's gait.
  • a gait sensor for carrying out measurements indicative of a subject's gait.
  • Such measurements are useful in detecting and assessing DPN since DPN commonly results in nerve disruptions, e.g. pain or numbness, in the subject's foot. These nerve disruptions can affect how a subject places their foot when walking and hence may affect the gait of the subject. Accordingly, analysis of gait together with blood flow provides enhanced detection and assessment of the presence or extent of DPN in a subject.
  • the gait sensor may comprise an accelerometer, for example, a 3D accelerometer (e.g.
  • the gait sensor may be sensitive to shock waves generated by Ground Reaction Forces (GRF).
  • GRFs are the forces exerted by the ground in reaction to the forces that body exerts on the ground through the foot. Whenever the heel strikes, a shock wave is generated and propagated through the skeleton to the sensor position.
  • a signature derived from the sensor acceleration can be determined and compared to known signatures to detect certain types of gait. Hence, a gait indicative of DPN can be identified.
  • Analysis of the measurements made by the gait sensor may be carried out by a processor provided on the wearable device or external to the wearable device.
  • a system for assessing blood flow in a subject, the system comprising: a wearable device comprising a plurality of photoplethysmography (PPG) sensors comprising a first PPG sensor and a second PPG sensor, each sensor being arranged to carry out measurements indicative of blood flow in the subject, wherein the PPG sensors are disposed such that, when the device is worn on an upper or lower limb of the subject, the first PPG sensor is in contact with the upper or lower limb on which the device is worn, and the second PPG sensor is contactable by the other of the upper or lower limb of the subject; and a processor arranged to compute a pulse arrival time at the portion of the lower limb and at the portion of the upper limb based on the measurements made by the first and second PPG sensors.
  • PPG photoplethysmography
  • the system may comprise an ECG monitor and the system may be arranged such that the PPG sensors and ECG monitor carry out measurements simultaneously.
  • Such an ECG monitor may be arranged to record the electrical activity of the subject's heart.
  • the ECG monitor may be positioned to take measurements at any location on the subject's body.
  • the ECG monitor is disposed on the wearable device as described above.
  • the system may comprise a memory component for storing measurements made by the first and second PPG sensors and/or the or an ECG monitor.
  • the system may comprise a communication device for transmitting data relating to the measurements made by the first and second PPG sensors and/or the or a ECG monitor to an external device, for example a storage device or the processor.
  • the wearable device may comprise a communication device for transmitting data to the processor.
  • Any suitable means of communication may be used, e.g. wired or wireless communication.
  • the system may comprise a gait sensor as described above.
  • the gait sensor may be provided at any location on the subject's body e.g. the head. Specific embodiments are described below by way of example only and with reference to the accompanying drawings in which:
  • Figure 1 is a diagram illustrating a wearable device as worn by a subject
  • Figure 2 is a diagram illustrating the wearable device of figure 1
  • Figure 3 is a diagram illustrating the wearable device of figure 1 ;
  • Figure 4 is a plot of the signals obtained from a PPG sensor directed towards a subject's ankle and from a PPG sensor directed towards a subject's finger;
  • Figure 5 is flow diagram illustrating how measurements from the wearable device may be used
  • Figure 6 is a plot of raw PPG sensor signals captured on the finger and ankle
  • Figure 7 is a plot of PPG signals captured by two sensors, one attached to the knee and one attached to the ankle, while pressures of 80mmHg and lOOmmHg were applied to the upper leg;
  • Figure 8 is a plot of a PPG waveform from a finger and an ECG reference from the chest;
  • Figure 9a is a plot of raw sensor signals captured by the ECG sensor and PPG sensor on the ankle, and the rectangle highlights the period when a pressure is applied to the upper leg;
  • Figure 9b is a plot of raw sensor signals captured before pressure was applied
  • Figure 9c is a plot of raw sensor signals captured during pressure application
  • Figure 9d is a plot of raw sensor signals captured after a pressure cuff was released
  • Figure 10 is a plot of the raw ECG and PPG signals captured (upper plot) and the corresponding PAT measurement results (lower plot). The black rectangle highlights the period in which pressure was applied to the subject's upper leg using a pressure cuff;
  • Figures 11a and 1 lb illustrate an alternative wearable device
  • Figure 12 is a diagram illustrating a system comprising a wearable device
  • Figure 13 illustrates the subplantar regions used for GRF analysis
  • Figure 14 illustrates Bayesian networks for detecting steps (left) and left/right foot strikes (right);
  • Figure 15 illustrates Bayesian networks for capturing the hindfoot, mid-foot, the metatarsals and phalanges contacts
  • Figure 16 illustrates Bayesian Networks for capturing medial and lateral foot contacts
  • Figure 17 illustrates Bayesian networks for capturing the contacts at the subdivided regions HO (left) and HI (right).
  • a wearable device 2 is now described with reference to Figures 1, 2 and 3.
  • the device 2 is arranged such that it may be worn around a subject's ankle and comprises a band having an outward facing sensor portion 6 and an inward facing sensor portion 8.
  • the device 2 also comprises a clasp 10 for fastening the device around the subject's ankle.
  • the inward facing sensor portion 8 and outward facing sensor potion 6 are disposed on opposite sides of the band.
  • the outward facing sensor portion 6 is positioned such that it is directed away from the subject's ankle and such that the subject may place their finger against the outward facing sensor portion 6 when the device is worn.
  • the inward facing sensor portion 8 is disposed such that it is directed towards the subject's ankle.
  • the outward facing sensor portion 6 comprises a
  • PPG photoplethysmography
  • the PPG sensors 12, 16 each comprise a pair of light emitting diodes (LED), a red LED and an infrared LED, and a photo-detector. Any suitable PPG sensor may be used.
  • a Hamlyn St0 2 sensor is used for each of the PPG sensors 10, 14. This sensor was developed by Chen et al. at the Hamlyn Centre for Robotic Surgery at Imperial College, London, and is described in further detail in "C.-M. Chen, R. Kwasnicki, B. Lo, and G. Z. Yang, "Wearable Tissue Oxygenation Monitoring Sensor and a Forearm Vascular Phantom Design for Data Validation," in Wearable and Implantable Body Sensor Networks (BSN), 2014 11th International Conference on, 2014, pp. 64-68" which in incorporated herein by reference.
  • the Hamlyn St0 2 sensor comprises an infrared LED, a red LED, and a photo-detector. With the low power design, the St0 2 sensor consumes only 6.6mW on average when sampling at 1 kHz.
  • the infrared LED emits light at 880nm and the red LED emits light at 740nm.
  • An example of the PPG signals obtained from the PPG sensor 16 directed towards the ankle and the PPG sensor 12 directed towards the finger is shown in Figure 4.
  • the device 2 also comprises a 1-lead electrocardiogram (ECG) monitor comprising two electrodes.
  • ECG electrocardiogram
  • a first ECG electrode 14a is disposed on the outward facing portion and a second ECG electrode 14b is disposed on the inward facing portion 6.
  • ECG monitor records the electrical activity of the heart when the subject places a finger on the ECG first electrode 14a and the subject's ankle is in contact with the second electrode 14b.
  • the device 2 comprises a communications unit (not shown) which is configured to transmit data relating to the measurements made by the PPG sensors and ECG monitor to an external device for analysis.
  • the data may be transmitted via any suitable means, for example, wired or wireless communication techniques.
  • the external device may be an external computing or storage device.
  • the device 2 also comprises a memory component (not shown) for storing data relating to the measurements made by the PPG sensors 12, 16 and the ECG monitor 14. This stored data may then be transmitted at desired intervals to the external device, for example, daily or weekly. Alternatively, data may be downloaded from the device as and when required.
  • the device 2 comprises a processor (not shown) for carrying out analysis of the measurements made by the PPG sensors and ECG monitor. The results of this analysis may then be transmitted from the device to an external device, for example for further analysis, by any suitable means as described above.
  • the wearable device 2 is positioned around a subject's ankle and fastened in place with the clasp 10.
  • the PPG sensor 16 directed towards the subject's ankle measures 18 the amount of light emitted by the LEDs which is absorbed and generates a PPG waveform indicative of the pressure pulse in the blood vessels of the ankle.
  • the ECG electrode 14b and PPG sensor 16 directed towards the subject's ankle is placed in contact with the subject's ankle, for example, by fastening the device or by manipulation of the device such that contact is made.
  • the PPG sensor 12 directed towards the subject's finger measures the amount of light emitted by the LEDs which is absorbed and generates a PPG waveform indicative of the pressure pulse in the blood vessels of the finger, and the ECG monitor measures the electrical activity of the heart and generates an electrocardiogram 18. These measurements are then used by the processor to calculate the Pulse Arrival Time (PAT) at the finger and at the ankle.
  • PTA Pulse Arrival Time
  • the Pulse Arrival Time is the time taken for the blood to flow from the heart to a given location, and is determined by measuring the time difference from a R-peak of the ECG signal obtained from the ECG monitor to the subsequent pulse captured on the finger and ankle respectively, using the PPG sensors. As such, to accurately measure the PAT, a robust ECG and PPG peak/valley detection algorithm is used.
  • a fixed window based median filter is used to remove the DC components (i.e. noise) of the signals, and the respective peaks and valleys of the signal are then detected by finding the maximum or minimum values within the time window.
  • the PAT is then obtained by measuring the time delay from an ECG R-peak to the subsequent PPG pulse 22 at each PPG sensor of the finger and ankle.
  • the PAT obtained at the finger is compared to that obtained at the ankle and a difference between the two is determined 24. This difference is then compared to known values 26 to determine whether or not, and to what extent, arterial stiffness or DPN is identified in the subject.
  • known values may comprise values obtained experimentally and for which there is a known relationship between the value and the existence or extent of arterial stiffness or DPN in a subject.
  • the basic experimental setup involved the placement of the Hamlyn PPG sensors at the chosen sites on the body, the ankle and the finger, and fitting a BSN ECG sensor on the chest to capture the R-peaks as reference for measuring PAT. Further detail on the BSN ECG sensor used is given in "B. P. Lo, S. Thiemjarus, R. King, and G.-Z. Yang, Body sensor network-a wireless sensor platform for pervasive healthcare monitoring: na, 2005" which is incorporated herein by reference.
  • To prove the concept of using multiple PPG sensors to detect DPN a simulated study was conducted with two healthy volunteers. In the study, subjects had the PPG sensors attached onto the knee, finger or ankle, and the ECG sensor attached onto the chest. A pressure cuff was used to simulate arterial stiffness or DPN.
  • the first experiment was designed to verify the proposed PPG sensor's ability in capturing pulse rate from the ankle and finger.
  • Figure 4 shows the output waveforms obtained from this procedure. The difference in the shape of the waveforms is clear with the finger signal denoting distinguishable peaks per cycle while the ankle signal has peaks of similar amplitude. This is mainly due to the fact that the fingertip has a much denser vascular structure than the ankle.
  • a blood pressure cuff was wrapped around the lower leg. Arterial stiffness or DPN was simulated by applying different pressures to block the venous blood flow in the leg.
  • the knee signal intensity was much higher than the ankle signal intensity. This is most likely due to the fact that the knee was closer to the pressure cuff where applied pressure can lead to vessel narrowing at that point and subsequently lead to turbulence. Most likely, the knee still experienced the effects of this turbulent flow and the ankle experiences steady, laminar flow as the turbulence might have died down before reaching this site so there was less variation in the magnitude of the result signal.
  • FIG. 8 illustrates the raw signals captured by the ECG sensor and the PPG sensor on the finger.
  • the time difference between the R-peak of the ECG signal to the PPG signal is known as the pulse transit time (or pulse arrival time) which is the time taken from the pulse to reach the finger after the ventricular depolarization of the heart.
  • the pulse arrival time was found to be 0.1917s for this instance.
  • Fig. 9a shows the raw sensor signals captured during the experiment with the time when pressure was applied highlighted with the black rectangle. To allow for proper signal comparison, the graph was divided into three regions: before pressure was applied (Fig. 9b), during pressure application (Fig. 9c) and after pressure cuff was released (Fig. 9d), and the signals are scaled for visual comparison.
  • the pulse arrival time at the ankle is highlighted in Fig. 9b, 9c and 9d.
  • the PAT was 0.1533s which is fairly similar to the value of 0.1917s obtained at the finger.
  • the pulse arrival time obtained was 0.6786s which is significantly higher than the corresponding values obtained from the finger.
  • Fig. 9d the PPG signal after the cuff was released is shown. Three different points where chosen to illustrate the behaviour of the pulse arrival times after the cuff was released.
  • the PAT for point 1, 2 and 3 were 0.6429s, 0.4500s and 0.3571s respectively.
  • the PAT was then measured and the results are shown in Figure 10.
  • the raw ECG and PPG signals captured on the subject's ankle are shown in Figure 10 (Top), and the corresponding PAT is shown in Figure 10 (Bottom).
  • the PAT during the period when pressure was applied onto the upper leg is higher than the other two periods - before introducing pressure/after the pressure was released.
  • the wearable device 20 comprises the same features as outlined above but does not comprise an ECG monitor.
  • measurements from an ECG monitor external to the device are used to calculate deviations in PAT at the ankle compared to the finger.
  • These calculations may be carried out at the wearable device itself.
  • ECG data is transmitted to the wearable device from the external ECG monitor.
  • PAT calculations may be carried out by a processing device external to the wearable device, as described below.
  • a system 200 which comprises a wearable device 202.
  • the wearable device comprises the same features as outlined above in relation to either the embodiment with or without the ECG monitor, but does not comprise a processor. Instead, a processor 204 is provided external to the wearable device 202.
  • Measurements made by the PPG sensors and, if present, on the wearable device, the ECG monitor 202 are stored in a memory component on the wearable device 202.
  • data from the storage device is transmitted to the external processor 204 via a communications unit 206 provided on the wearable device.
  • the data may be transmitted via any suitable means, for example, wired or wireless communication techniques.
  • the processor 204 analyses the received data to calculate the Pulse Arrival Time (PAT) at the finger and at the ankle using the techniques described above.
  • PAT Pulse Arrival Time
  • data may be transmitted directly to the external processor without storage on the wearable device.
  • the system or wearable device comprises a gait sensor.
  • the gait sensor is a 3D accelerometer e.g. Analog Devices ADXL335.
  • gait sensor the e-AR (ear- worn Activity Recognition) sensor
  • e-AR ear- worn Activity Recognition
  • any suitable gait sensor worn at any location on the body may be used e.g. on the ankle as part of the wearable device.
  • the e-AR (ear-worn Activity Recognition) sensor is a bio-inspired sensor designed to emulate the main functions of the human vestibular system. It mainly consists of an 8051 processor with a 2.4 GHz transceiver (Nordic nRF24El), a 3D accelerometer (Analog Devices ADXL335), a 2MB EEPROM (Atmel AT45DB161), and a 55mAhr Li-Polymer battery.
  • the e-AR sensor is also sensitive to shock waves generated by GRF.
  • GRFs are the forces exerted by the ground in reaction to the forces that body exerts on the ground through the foot. Whenever the heel strikes, a shock wave is generated and propagated through the skeleton to the cranium, which may be picked up from the superior and posterior auricular regions. The axial skeleton does not dissipate the transients or affect their interference where matching signals were found from the
  • the accelerometer mounted on the forehead and the accelerometer attached to the tibial tuberosity. This means the axial skeleton is a good conductor for the transient of both high and low-frequency waves generated by the GRFs.
  • Figure 13 schematically illustrates the sub-plantar regions used for this study.
  • the forefoot is divided into phalanges (toes) (T) and metatarsals (F), whereas M represents the midfoot (the five tarsal bones) and H represents the hindfoot (the talus and the calcaneus or the heel).
  • T phalanges
  • F metatarsals
  • M represents the midfoot (the five tarsal bones)
  • H represents the hindfoot (the talus and the calcaneus or the heel).
  • Each region is further separated into lateral (O) and medial (I) halves.
  • HO means the lateral hindfoot region.
  • a hierarchical Bayesian network is designed to estimate the plantar force distribution.
  • the network is designed to match different phases of the foot strike (i.e. three layers of networks are designed to detect foot step, heel (hindfoot) strike, and lateral hindfoot strike).
  • the parameters of the network are learned from the sensor data (20% of all the sensor data was used for the learning phase).
  • a naive Bayesian is constructed to detect steps where the three orthogonal signals of the e-AR sensor (i.e., e-ARx, e-ARy, e-ARz correspond to the lateral, vertical and fore-aft accelerations) are represented as the child nodes as shown in Figure 14 (left).
  • Each step is detected by calculating the maximum a-posteriori probability (MAP):
  • Step arg max P(Step ⁇ eAR x , eAR y , eAR z ⁇ )
  • the output of the step detection together with the accumulated signal Ac are then fused to determine whether it is a left or right foot strike as shown in Figure 14 (right).
  • the posterior probability can therefore be calculated as follows:
  • variable Ac is the accumulated value of the lateral acceleration (i.e. e-ARx).
  • the vertical acceleration signal is fused with the output of the step-detection network to infer the force contact at different areas of the foot. This is depicted in Figure 15.
  • a high pass filter is used to extract the high frequency shock waves and the posterior probability of the heel (hindfoot) strike is formulated as follows:
  • HP is the high pass filtered signal of the vertical acceleration (i.e., e-ARy) signal from the e-AR sensor.
  • the stance phase is Markovian
  • the past states of the hindfoot contact is fused with the vertical acceleration and the posterior probability is calculated as follows:
  • the medial (I) and lateral (O) foot contacts are then inferred by fusing the lateral acceleration with the step detection, and the corresponding Bayesian network is depicted in Figure 16. Accordingly, the posterior probabilities are calculated as follows:
  • FIG. 17 depicts the Bayesian networks for detecting the HO and HI contacts, and the posterior probabilities for the subdivided regions are formulated as follows:
  • ⁇ ⁇ HO, HI, MO, MI, FO, FI, TO, Tlj
  • ⁇ ⁇ H H M, M, F, F, T, T ⁇
  • ⁇ represents the series of the hindfoot to phalanges regions
  • ⁇ represents the series of medial and lateral regions.
  • the wearable device comprises a processor for computation of a difference in the pulse time of arrival at each of the PPG sensor measurement locations.
  • ECG measurements may be obtained from a monitor separate to the wearable device and transmitted to an external device for computation of the pulse arrival time at each of the PPG sensor measurement locations.
  • the device is arranged to be worn on a subject's upper limb e.g. a wrist or finger, such that the subject may bring the device into contact with his or her lower limb e.g. an ankle.

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Abstract

L'invention comprend un dispositif portable pour évaluer le débit sanguin chez un sujet, le dispositif comprenant une pluralité de capteurs de photopléthysmographie (PPG) comprenant un premier capteur de PPG et un second capteur de PPG, chaque capteur étant agencé pour effectuer des mesures indiquant le débit sanguin chez le sujet. Les capteurs de PPG sont disposés de telle sorte que, lorsque le dispositif est porté sur un membre inférieur ou supérieur du sujet, le premier capteur de PPG est en contact avec le membre inférieur ou supérieur sur lequel le dispositif est porté, et le second capteur de PPG peut être mis en contact avec l'autre membre inférieur ou supérieur du sujet.
PCT/EP2016/062639 2015-06-04 2016-06-03 Système et dispositif de détection portable WO2016193423A1 (fr)

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WO2018152189A1 (fr) * 2017-02-17 2018-08-23 Sensogram Technolgies, Inc. Système et procédés photopléthysmographiques portables de surveillance de la pression sanguine
WO2019110553A1 (fr) * 2017-12-04 2019-06-13 Imec Vzw Dispositif portable et système de surveillance de signes vitaux d'une personne
EP3782542A1 (fr) * 2019-08-20 2021-02-24 Stichting IMEC Nederland Procédé et système d'évaluation de la fonction de la microcirculation
KR20220083972A (ko) * 2020-12-09 2022-06-21 선전 구딕스 테크놀로지 컴퍼니, 리미티드 혈압 측정 방법, 장치 및 전자 장치
CN115363553A (zh) * 2022-08-09 2022-11-22 苏州国科医工科技发展(集团)有限公司 一种糖尿病足检测方法及系统
CN115998276A (zh) * 2022-11-01 2023-04-25 中国人民解放军总医院第二医学中心 一种脉搏波传导速度采集装置及方法
WO2023222911A1 (fr) * 2022-05-19 2023-11-23 Guy's And St Thomas' Nhs Foundation Trust Appareil et procédé pour provoquer une vasoconstriction par stimulation électrique
WO2024153587A1 (fr) * 2023-01-17 2024-07-25 Biolab Innovation Gmbh Agencement pour déterminer un temps de transit de l'onde de pouls d'un objet, procédé mis en œuvre par ordinateur et produit programme d'ordinateur

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WO2018152189A1 (fr) * 2017-02-17 2018-08-23 Sensogram Technolgies, Inc. Système et procédés photopléthysmographiques portables de surveillance de la pression sanguine
WO2019110553A1 (fr) * 2017-12-04 2019-06-13 Imec Vzw Dispositif portable et système de surveillance de signes vitaux d'une personne
EP3782542A1 (fr) * 2019-08-20 2021-02-24 Stichting IMEC Nederland Procédé et système d'évaluation de la fonction de la microcirculation
US11717172B2 (en) 2019-08-20 2023-08-08 Stichting Imec Nederland Method and system for determining a parameter related to microcirculation function
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WO2023222911A1 (fr) * 2022-05-19 2023-11-23 Guy's And St Thomas' Nhs Foundation Trust Appareil et procédé pour provoquer une vasoconstriction par stimulation électrique
CN115363553A (zh) * 2022-08-09 2022-11-22 苏州国科医工科技发展(集团)有限公司 一种糖尿病足检测方法及系统
CN115363553B (zh) * 2022-08-09 2024-01-23 苏州国科医工科技发展(集团)有限公司 一种糖尿病足检测方法及系统
CN115998276A (zh) * 2022-11-01 2023-04-25 中国人民解放军总医院第二医学中心 一种脉搏波传导速度采集装置及方法
WO2024153587A1 (fr) * 2023-01-17 2024-07-25 Biolab Innovation Gmbh Agencement pour déterminer un temps de transit de l'onde de pouls d'un objet, procédé mis en œuvre par ordinateur et produit programme d'ordinateur

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