SYSTEMS, DEVICES, AND METHODS FOR MEASURING BLOOD PRESSURE OF A USER

• US 20170360306A1
• Filed: 09/08/2015
• Published: 12/21/2017
• Est. Priority Date: 09/08/2014
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Narasimhan, Ravi, Zeng, Zijing, Kimoto, Richard C., Klaassen, Erno, Sullivan, Thomas J., Young, Derek Park-Shing, Whitehurst, Todd K.
• Granted Patent: US 10,702,171 B2
• Time in Patent Office: Days
• CPC Class Codes: A61B 2560/0223 of calibration, e.g. protocols for calibrating sensors
• CPC Class Codes: A61B 2562/0247 Pressure sensors
• CPC Class Codes: A61B 2562/028 Microscale sensors, e.g. electromechanical sensors [MEMS]
• CPC Class Codes: A61B 2562/046 in a matrix array
• CPC Class Codes: A61B 5/0053 by applying pressure, e.g. compression, indentation, palpation, grasping, gauging
• CPC Class Codes: A61B 5/02108 from analysis of pulse wave characteristics
• CPC Class Codes: A61B 5/02125 of pulse wave propagation time
• CPC Class Codes: A61B 5/022 by applying pressure to close blood vessels, e.g. against the skin; Ophthalmodynamometers
• CPC Class Codes: A61B 5/681 Wristwatch-type devices
• CPC Class Codes: A61B 5/6824 Arm or wrist

Abstract

The present invention generally relates to blood pressure monitoring. In some embodiments, methods and devices of measuring a mean arterial pressure are provided and/or monitoring blood pressure changes. A wrist-worn device may include a plurality of sensors backed by a plurality of actuators. Subsets of the plurality of sensors may be selectively actuateable against a wrist of a user using one or more of the plurality of actuators. A preferred sensor and location may be identified based on pressure signals received from each of the sensors. In some embodiments, devices may use a fluid bladder coupled with piezoelectric film sensors. A fluid bladder pressure sensor may be used to calibrate the piezoelectric film signal to provide a static and dynamic pressure reading. In yet another embodiment, a mean arterial pressure may be calculated by processing a swept pressure signal obtained as a sensor is swept through different heights.

Claims

1. A method of measuring blood pressure of a user having a wrist, skin defining an outer surface of the wrist, the method comprising:

maintaining engagement between the skin of the wrist and a skin interface of a wrist-worn device using a band having a length extending about the wrist, the wrist-worn device having a plurality of actuators and a sensor system, the skin interface including an array of surface regions;

selectively urging a first region of the array at a first location of the band against the wrist with a first actuator and receiving a first associated signal from the sensor system;

selectively urging a second region of the array at a second location of the band against the wrist with a second actuator and receiving a second associated signal from the sensor system, wherein the first location is spaced apart from the second location along the length of the band;

identifying a preferred subset of the array by comparing the first signal and the second signal;

deriving a pressure signal indicative of a pressure of blood of the user using signals associated with the preferred subset of the array; and

outputting the pressure signal.

2. The method of claim 1, wherein selectively urging the first region of the array against the wrist of the user is performed concurrently with receiving the first signal so that the first signal is a first swept pressure signal comprising a plurality of pressure waveforms measured while an applied pressure by the first actuator is varied;

and wherein selectively urging the second region against the wrist of the user is performed concurrently with receiving the second signal so that the second signal is a second swept pressure signal comprising a plurality of pressure waveforms measured while an applied pressure of the second actuator is varied.

3. The method of claim 2, wherein comparing the first signal and the second signal comprises identifying a first maximum pressure pulse in the first swept pressure signal and a second maximum pressure pulse in the second swept pressure signal and wherein the preferred subset of the array is associated with the signal with a larger maximum pressure pulse amplitude.

4. The method of claim 1, further comprising withdrawing the first region from the wrist of the user prior to receiving the second signal from the sensor system.

5. The method of claim 1, wherein the sensor system comprises a sensor array with a pressure sensor positioned at each region of skin interface array;

and wherein each pressure sensor is coupled with an actuator of the plurality of actuators so that selectively urging the first region of the array and selectively urging the second region of the array against the wrist is performed by urging a first pressure sensor with the first actuator against the wrist and by urging a second pressure sensor with the second actuator against the wrist, respectively.

6. A device for determining blood pressure of a user having a wrist, skin defining an outer surface of the wrist and an artery;

the device comprising;

an elongate band with a length configured to extend around the wrist of the user so as to support a skin interface surface of the device in engagement with the skin of the wrist;

a plurality of pressure actuators coupling the elongate band to the skin interface surface, the pressure actuators configured to apply a variable pressure between the skin interface surface and the skin of the wrist at an array of regions distributed along the skin interface surface;

a sensor system with a sensor surface extending along the skin interface surface;

a signal processing system coupled with the sensor system and the actuators such that, in use, first and second subsets of the pressure actuators selectively and sequentially urge associated first and second subsets of the array against the wrist so as to generate a plurality of sensor signals from the sensor system, wherein the first subset of the array is at a first location of the band and the second subset of the array is at a second location of the band, and wherein the first location is spaced apart from the second location along the length of the band, and

wherein the signal processing system is configured to output a signal indicative of a pressure of the blood pressure of the user in response to the sensor signals.

7. The device of claim 6, wherein the pressure actuators are each actuated individually so as to urge a single region of the skin interface array against the wrist at a time.

8. The device of claim 6, wherein the pressure actuators comprise a linear solenoid piston.

9. The device of claim 6, wherein the plurality of pressure actuators comprise fluid bladders configured to be selectively filled with a fluid to drive a coupled pressure sensor a desired amount against the wrist and to be selectively deflated to reduce an amount of pressure applied by the coupled pressure sensor against the wrist.

10. The device of claim 9, wherein the fluid bladders are selectively filled by a phase change of a filling fluid from a liquid to a gas.

11. The device of claim 9, further comprising a bladder pressure sensor configured to identify a pressure within one or more of the plurality of fluid bladders.

12. The device of claim 11, wherein the sensor system comprises a piezoelectric film pressure sensor.

13. The device of claim 12, wherein the blood pressure is calculated from piezoelectric film pressure measurements by calibrating the piezoelectric film pressure measurements with the pressure identified within one or more of the plurality of fluid bladders.

14. The device of claim 6, wherein the sensor system comprises a piezoresistive pressure sensor.

15. The device of claim 6, wherein the sensor system comprises a 12×

1 array of pressure sensors or greater.

16. The device of claim 6, wherein the sensor system comprises a 3×

4 array of pressure sensors or greater.

17. The device of claim 6, wherein the device calculates the blood pressure without user interaction or periodic calibration.

18-36. -36. (canceled)