Wrist-worn pulse transit time sensor

Patent metadata

Field	Value
Publication number	US-2016287172-A1
Application number	US-201514750646-A
Country	US
Kind code	A1
Filing date	Jun 25, 2015
Priority date	Apr 2, 2015
Publication date	Oct 6, 2016
Grant date	—

Abstract

A wrist-worn device heart-monitoring device is presented. The wrist-worn heart-monitoring device includes a radial tonometer configured to output a pressure signal indicating a pulse pressure wave at a user's wrist, two or more electrodes configured to output an electrical signal indicating a user's heart has been commanded to contract, and a microphone configured to output an audio signal indicating a closing of a user's aortic valve. The wrist-worn heart-monitoring device further includes a pulse transit time monitor configured to calculate a pre-ejection period of the user's heart based on at least the pressure, electrical, and audio signals, and calculate a pulse transit time based on at least the pre-ejection period, the pressure signal, and the electrical signal.

First claim

1 . A wrist-worn heart monitoring device, comprising:
a radial tonometer configured to output a pressure signal indicating a pulse pressure wave at a wearer's wrist; two or more electrodes configured to output an electrical signal indicating a wearer's heart has been commanded to contract; a microphone configured to output an audio signal indicating a closing of a wearer's aortic valve; and a pulse transit time monitor configured to:
calculate a pre-ejection period of the wearer's heart based on at least the pressure, electrical, and audio signals; and
calculate a pulse transit time based on at least the pre-ejection period, the pressure signal, and the electrical signal.

2 . The wrist-worn heart monitoring device of claim 1 , wherein one or more electrodes are located on a user-adjacent surface of the wrist-worn heart monitoring device, and wherein one or more electrodes are located on an externally-facing surface of the wrist-worn heart monitoring device.

3 . The wrist-worn heart monitoring device of claim 1 , further comprising:
a primary device; a satellite device including the radial tonometer; and an adjustable strap configured to fix a position of the satellite device relative to the primary device, the primary device, satellite device, and adjustable strap cooperatively forming a loop configured to be worn around the wearer's wrist.

4 . The wrist-worn heart monitoring device of claim 3 , wherein the radial tonometer further comprises:
a flexible cap configured to at least partially protrude from an opening in a housing of the satellite device, and further configured to conduct pressure to a pressure transducer within the satellite device.

5 . The wrist-worn heart monitoring device of claim 3 , wherein one or more of the electrodes located on the externally-facing surface of the wrist-worn heart monitoring device are located at the adjustable strap.

6 . The wrist-worn heart monitoring device of claim 1 , wherein the electrical signal indicating a wearer's heart has been commanded to contract is output responsive to a sensed heartbeat command while first electrode contacts a first measurement location on a wearer's skin on a first effective side of the wearer's heart, and a second electrode contacts a second measurement location on the wearer's skin on a second, opposite, effective side of the wearer's heart.

7 . The wrist-worn heart monitoring device of claim 1 , wherein the pulse transit time monitor is further configured to:
calculate a pulse wave velocity based on the pulse transit time and a distance between the wearer's aortic valve and the wearer's wrist.

8 . The wrist-worn heart monitoring device of claim 1 , wherein the pulse transit time monitor is further configured to:
store the calculated pre-ejection period of the wearer's heart; and calculate a radial pulse arrival time responsive to receiving an electrical signal indicating the wearer's heart has been commanded to contract, and a pressure signal indicating a pulse pressure wave at the wearer's wrist; calculate a pulse-transit time based on at least the radial pulse arrival time and the stored pre-ejection period without receiving an audio signal indicating a closing of the wearer's aortic valve.

9 . A wrist-worn heart monitoring device, comprising:
a primary device; an adjustable strap, the primary device and adjustable strap cooperatively forming a loop configured to be worn around a wearer's wrist, the loop having an inner surface facing the wearer's wrist and an outer surface facing away from the wearer's wrist; a first electrode on the inner surface of the loop and configured to contact a first measurement location on a wearer's skin on a first effective side of the wearer's heart; a second electrode on the outer surface of the loop at the adjustable strap and configured to contact a second measurement location on the wearer's skin on a second, opposite, effective side of the wearer's heart; and a controller configured to measure an electrical potential between the first measurement location and the second measurement location.

10 . The wrist-worn heart monitoring device of claim 9 , wherein the first electrode is in contact with an underside of the wearer's wrist when the primary device is located on a back of the wearer's wrist.

11 . The wrist-worn heart monitoring device of claim 9 , wherein the adjustable strap comprises one or more conductive zones on an outer surface of the adjustable strap, and wherein the second electrode is included in a conductive zone on the outer surface of the adjustable strap.

12 . The wrist-worn heart monitoring device of claim 11 , wherein the adjustable strap comprises one or more conductive zones on an inner surface of the adjustable strap, and wherein the first electrode is included in a conductive zone on the inner surface of the adjustable strap.

13 . The wrist-worn heart monitoring device of claim 9 , further comprising:
a third electrode on the outer surface of the loop and configured to contact a third measurement location on the wearer's skin.

14 . The wrist-worn heart monitoring device of claim 13 , further comprising:
fastening componentry configured to adjust a circumference of the loop through interactions with the adjustable strap and including one or more conductive components electrically coupled to the primary device such that the third electrode comprises the one or more conductive components of the fastening componentry.

15 . The wrist-worn heart monitoring device of claim 13 , wherein the controller is further configured to determine a composite negative pole of the wearer based on the electrical potential between the first measurement location and the second measurement location, an electrical potential between the first measurement location and the third measurement location, and an electrical potential between the second measurement location and the third measurement location.

16 . A wrist-worn heart monitoring device, comprising:
a first electrode and a second electrode, the first and second electrodes configured to output a voltage difference indicative of an electrical potential of a wearer's heart when the first electrode contacts a first measurement location on a wearer's skin on a first effective side of the wearer's heart and the second electrode contacts a second measurement location on the wearer's skin on a second, opposite, effective side of the wearer's heart; an electrode-positioning sensor subsystem to determine a three-dimensional position of the second electrode respective to the second measurement location; and a controller configured to:
receive a voltage difference from the first and second electrodes;
receive an indication of the three-dimensional position of the second electrode respective to the second measurement location from the electrode-positioning sensor subsystem; and
output an electrical potential of the wearer's heart responsive to the second electrode being located within a threshold distance of the second measurement location.

17 . The wrist-worn heart monitoring device of claim 16 , further comprising a user interface configured to:
communicate an instruction to adjust the three-dimensional position of the second electrode responsive to the second electrode being located more than the threshold distance from the second measurement location

18 . The wrist-worn heart monitoring device of claim 17 , wherein the electrode-positioning sensor subsystem is further configured to determine a three-dimensional position of the second electrode res

Assignees

• Microsoft Technology Licensing Llc

Inventors

• Morris Daniel
• Tan Desney S
• Saponas T Scott
• Patel Shwetak N
• Villar Nicolas
• Smith Gregory R
• Gupta Sidhant
• Cohn Gabriel Adam
• Kale David C
• Malladi Sailaja
• Paulsen Ronald E

Classifications

• G16H50/20

  for computer-aided diagnosis, e.g. based on medical expert systems · CPC title

• A61B5/02438

  with portable devices, e.g. worn by the patient · CPC title

• A61B5/11

  Measuring movement of the entire body or parts thereof, e.g. head or hand tremor or mobility of a limb {(A61B5/1038 takes precedence; motion detection to correct for motion artifacts in physiological signals A61B5/721)} · CPC title

• A61B5/029 Primary

  Measuring blood output from the heart, e.g. minute volume · CPC title

• A61B5/1072

  measuring distances on the body, e.g. measuring length, height or thickness (A61B5/1076 takes precedence) · CPC title