Systems and methods for monitoring the circulatory system

• US 9,241,637 B2
• Filed: 04/21/2015
• Issued: 01/26/2016
• Est. Priority Date: 01/27/2011
• Status: Active Grant

• Current Assignee: Board of Trustees of the Leland Stanford Junior University (Stanford University)
• Original Assignee: Board of Trustees of the Leland Stanford Junior University (Stanford University)
• Inventors: Wiard, Richard M., Giovangrandi, Laurent B., Kovacs, Gregory T.
• Primary Examiner(s): Stigell, Theodore
• Assistant Examiner(s): CAREY, MICHAEL JAMES
• Application Number:
  US14/691,965
• Publication Number:
  US 20150282718A1
• Time in Patent Office: 280 Days
• Field of Search: 600/526, 600/527, 600/508
• US Class Current: 1/1
• CPC Class Codes: A61B 5/0002 Remote monitoring of patients using telemetry, e.g. transmission of vital signals via a communication network A61B5/07 takes precedence; transmission systems for measured values G08C; transmission H04B; transmission of digital information H04L; wireless communication networks H04W
• CPC Class Codes: A61B 5/02007 Evaluating blood vessel condition, e.g. elasticity, compliance
• CPC Class Codes: A61B 5/0205 Simultaneously evaluating both cardiovascular conditions and different types of body conditions, e.g. heart and respiratory condition
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/02125 of pulse wave propagation time
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/0261 using optical means, e.g. infrared light
• CPC Class Codes: A61B 5/0265 using electromagnetic means, e.g. electromagnetic flowmeter
• CPC Class Codes: A61B 5/0285 Measuring or recording phase velocity of blood waves
• CPC Class Codes: A61B 5/0535 Impedance plethysmography for measuring blood flow A61B5/0295
• CPC Class Codes: A61B 5/1102 Ballistocardiography
• CPC Class Codes: A61B 5/318 Heart-related electrical modalities, e.g. electrocardiography [ECG]
• CPC Class Codes: A61B 5/6826 Finger
• CPC Class Codes: A61B 5/6829 Foot or ankle
• CPC Class Codes: A61B 5/6887 mounted on external non-worn devices, e.g. non-medical devices
• CPC Class Codes: A61B 5/721 using a separate sensor to detect motion or using motion information derived from signals other than the physiological signal to be measured
• CPC Class Codes: A61B 5/7264 Classification of physiological signals or data, e.g. using neural networks, statistical classifiers, expert systems or fuzzy systems neural networks per se G06N3/00; expert systems per se G06N5/00
• CPC Class Codes: A61B 5/7278 Artificial waveform generation or derivation, e.g. synthesising signals from measured signals A61B5/327 takes precedence
• CPC Class Codes: A61B 5/742 using visual displays A61B5/339 takes precedence
• CPC Class Codes: G01G 19/50 having additional measuring devices, e.g. for height

Abstract

In accordance with embodiments of the present disclosure, a ballistocardiogram (BCG) sensor is used to detect heart and vascular characteristics of a user, and provide a BCG output indicative of the detected cardiovascular characteristics. The BCG output can be used for various purposes, such as detecting arterial aging. Secondary sensors can be used in conjunction with the BCG and can be used to determine the central arterial blood pressure, when used in conjunction with a peripheral blood pressure measurement.

Claims

1. A method comprising:

generating an arterial stiffness measurement by

in a body scale including and integrating a first sensor, using the first sensor to capture, while a user is standing on the body scale, a BCG (ballistocardiogram) or hand-to-hand impedance cardiogram T1 signal that is indicative of mechanical movement of blood through a user'"'"'s aorta and that is indicative of a proximal cardiogram timepoint or a T1 carotid timepoint;

using a second sensor to detect a pressure pulse at a location sufficiently distal to the user'"'"'s aorta to allow a determination of arterial pulse wave velocity; and

using logic circuitry to determine the arterial pulse wave velocity by calculating timings corresponding to the T1 signal and a timing of the pressure pulse.

2. The method of claim 1, wherein using a second sensor to detect the pressure pulse includes detecting the pressure pulse at a user'"'"'s limb.

3. The method of claim 1, wherein using the first sensor to capture the BCG signal includes measuring variations in downward pressure exerted by the user'"'"'s feet.

4. The method of claim 1, further including using the logic circuitry to determine blood pressure changes of the user by using a predetermined relationship between pulse wave velocity and blood pressure changes.

5. The method of claim 1, wherein the body scale further includes:

an integrated visual display to communicate aspects of circulatory function to the user; and

a wireless communication interface configured to provide raw data and computed physiological parameters to care providers.

6. The method of claim 1, further including using the arterial stiffness measurement as an indication of a degree to which an arterial wall is hardened and at least partly based on this indication, assessing the user as having one or more of a plurality of cardiovascular disorders and complications including:

increased blood pressure, left ventricular hypertrophy, myocardial infarction, stroke and renal failure.

7. The method of claim 1, wherein the first sensor is used to measure, while the user is standing on the body scale, multiple signals in the user, wherein each of the multiple signals have their origin at two different locations in the body, and using the multiple signals for determining arterial stiffness.

8. The method of claim 1, wherein the first sensor is a part of a BCG sensor and further including using the BCG sensor to capture a BCG signal from the user, and wherein the second sensor is configured and arranged to detect blood pressure pulse travel time at the user'"'"'s feet, the first sensor and second sensor being used to determine a characteristic of the user'"'"'s distal arterial stiffness.

9. The method of claim 1, wherein the second sensor is configured and arranged to detect blood pressure pulse travel time at the user'"'"'s extremity locations, including at least one member of the feet and hands, to determine differential characteristics of the user'"'"'s arterial stiffness along different branches and further including using a computer-processor circuit as part of the logic circuitry, wherein the computer-processor circuit uses outputs from at least one of the sensors to determine estimates of overall circulatory function of the user along the different arterial branches and to provide estimates of arterial stiffness of intermediate segments.

10. The method of claim 1, further including:

using the arterial stiffness measurement to determine brachial and central pressure differences of the user; and

based on a measured indication of peripheral blood pressure and the arterial stiffness measurement, determining central aortic blood pressure of the user.

11. The method of claim 1, wherein further including using an algorithm for deriving intermediate arterial stiffness values from combining central plus peripheral measurements of BCG and foot PPG.

12. The method of claim 1, wherein the second sensor detects the pressure pulse while the user is in a standing or upright position.

13. The method of claim 1, further including repeating the step of generating an arterial stiffness measurement in order to generate respective multiple arterial stiffness measurements, and then using the multiple arterial stiffness measurements to characterize or assess aberrant central hemodynamic properties of the user.

14. The method of claim 1, wherein the user is considered hypertensive or in antihypertensive treatment, and further including using the arterial stiffness measurement to detect changes in arterial elasticity and other hemodynamic properties of the user.

15. The method of claim 1, further including using the arterial stiffness measurement to detect changes in arterial elasticity and other hemodynamic properties of the user and providing prognostic and diagnostic data for the user as an indication of elevated blood pressure.

16. The method of claim 1, further including determining, using the logic circuitry, a measurement of the Carotid-Femoral Pulse Wave Velocity (cfPWV) to quantify the arterial stiffness of the user.

17. The method of claim 1, further including using the T1 signal and a T2 timepoint to calculate arterial vascular stiffness.

18. The method of claim 1, further including estimating arterial stiffness indirectly by measuring the pulse wave velocity (PWV) along the artery based on mathematic relationships between wave speed (c) to vessel wall elastic modulus (E), wall thickness (t), diameter (D), and blood density (ρ

).

19. The method of claim 1, further including using the arterial stiffness measurement as part of a prognostic or diagnostic for management of the user'"'"'s cardiovascular risk.

20. The method of claim 1, further including using the arterial stiffness measurement and the body scale to carry out longitudinal trending of the user'"'"'s arterial stiffness.

21. The method of claim 1, further including assessing the user'"'"'s cardiovascular risk by using the arterial stiffness measurement and by determining the user'"'"'s arterial stiffness and/or elasticity through multiple pulse wave velocity measurements.

22. The method of claim 1, further including the steps of:

using the first sensor and the second sensor to measure at least one other timepoint;

determining aortic vascular stiffness based on the T1 signal and the at least one other timepoint; and

using data concerning velocity in the central aorta and velocity in the peripheral arteries to assess changes in vascular stiffness in the aorta and to evaluate efficacy of anti-hypertension drugs working on vascular tone.

23. The method of claim 1, further including the steps of:

using the first sensor and the second sensor to measure at least one other timepoint;

determining aortic vascular stiffness based on the T1 signal and the at least one other timepoint; and

using data concerning velocity in the central aorta and velocity in peripheral arteries of the user to evaluate efficacy of anti-hypertension drugs working on vascular tone.

24. The method of claim 1, further including using BCG timing as a start of a pulse wave of the user and measuring peripheral stiffness and central vascular stiffness for characterization of an arterial pressure mismatch.

25. The method of claim 1, wherein the body scale has a limited mechanical frequency response that is set as a function of physical stiffness of the scale and coupling of the scale to the floor, wherein the limited mechanical frequency enables the first sensor and the second sensor to obtain signals concerning relevant information in the bandwidth in a range of approximately 0-20 Hertz, and further including processing the obtained signals by filtering frequency content outside of this range.

26. The method of claim 1, further including verifying the step of generating an arterial stiffness measurement by performing continuous blood pressure measurements using a Valsalva maneuver, wherein the maneuver is divided into three intervals:

(1) rest, (2) strain, and (3) release, and wherein the rest interval depicts normal blood pressure.

27. The method of claim 1, further including using the arterial stiffness measurement to manage hypertension by monitoring blood pressure change based on a relationship between the arterial stiffness measurement and elastic modulus of a vessel and pressure in the vessel, wherein a PWV measurement is used as a correlative parameter for blood pressure change based on BCG and foot PPG signals obtained while the user is standing on the body scale.

28. The method of claim 1, further including obtaining simultaneously, at the feet while the user is standing on the scale, both BCG and PPG measurements for the determination of arterial stiffness/elasticity.

29. The method of claim 1, further including repeating the step of generating the arterial stiffness measurement and further including associating each of the arterial stiffness measurements to one of a plurality of postures of the user for which measurements are taken.

30. The method of claim 1, wherein the logic circuitry includes a computer-processor circuit programmed and arranged with an algorithm configured to process heart and vascular signals and to determine therefrom heart and vascular function characteristics of the user based upon data obtained from the first sensor and the second sensor, wherein the first sensor includes a force-detection circuit to detect weight or weight variances of the user and wherein the second sensor includes circuitry configured and arranged to generate data that is used as a parameter of the algorithm.

31. A method comprising:

generating an arterial stiffness measurement by

in a body scale including and integrating a first sensor, using the first sensor to capture, while a user is standing on the body scale, a BCG (ballistocardiogram) or hand-to-hand impedance cardiogram reference signal that is indicative of mechanical movement of blood through a user'"'"'s aorta and that is indicative of a proximal cardiogram timepoint or a carotid timepoint;

using a second sensor to detect a pressure pulse at a location sufficiently distal to the user'"'"'s aorta to assess or approximate an arterial pulse wave velocity; and

using logic circuitry to assess the arterial pulse wave velocity by calculating timings corresponding to the cardiogram reference signal and a timing of the pressure pulse at said location.

32. The method of claim 31, wherein the arterial pulse wave velocity is a central arterial pulse wave velocity and further including using circuitry in each of the first sensor, the second sensor and the logic circuitry cooperatively to assess the central arterial pulse wave velocity.

33. The method of claim 31, wherein the first sensor includes circuitry arranged to capture a signal indicative of physical movement and/or mechanical output of the heart of the user while the user is standing on the body scale, and the first sensor is used as part of a BCG capture method, the second sensor includes circuitry and is used at a location along the brachial, radial or finger, and wherein the logic circuitry determine differences indicative of pressure differences between central arterial pressure and pressure in the brachial, radial or finger.

34. The method of claim 31, further including using the logic circuitry cooperatively to assess the central arterial pulse wave velocity based on the user'"'"'s standing position altering hemodynamic loads on the arteries in such a manner, and based on patient information including at least one of the user'"'"'s age and the user'"'"'s gender.

35. The method of claim 31, further including using the first sensor, the second sensor and the logic circuitry cooperatively to assess the arterial pulse wave velocity based on an association correspondence between measurements relative to a portion of the user'"'"'s aortic arch, and central pressure-induced forces associated with the arterial pulse wave velocity.