Physiological signal determination of bioimpedance signals

• US 20150282768A1
• Filed: 11/04/2014
• Published: 10/08/2015
• Est. Priority Date: 09/29/2012
• Status: Abandoned Application

• Current Assignee: JB IP Acquisitions LLC
• Original Assignee: AliphCom, Inc. (AliphCom Corp.)
• Inventors: Luna, Michael Edward Smith, Primas, Sidney, Stivoric, John
• Application Number:
  US14/121,943
• Publication Number:
  US 20150282768A1
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: A61B 2562/0219 Inertial sensors, e.g. accelerometers, gyroscopes, tilt switches
• CPC Class Codes: A61B 2562/043 in a linear array
• 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 5/024 Detecting, measuring or recording pulse rate or heart rate A61B5/0205, A61B5/021 take precedence
• CPC Class Codes: A61B 5/02438 with portable devices, e.g. worn by the patient
• CPC Class Codes: A61B 5/02444 Details of sensor A61B5/02427 takes precedence
• CPC Class Codes: A61B 5/0245 by using sensing means generating electric signals, i.e. ECG signals
• CPC Class Codes: A61B 5/053 Measuring electrical impedance or conductance of a portion of the body
• CPC Class Codes: A61B 5/0816 Measuring devices for examining respiratory frequency measuring frequency of electric signals G01R23/00
• CPC Class Codes: A61B 5/1101 Detecting tremor
• CPC Class Codes: A61B 5/1118 Determining activity level
• CPC Class Codes: A61B 5/165 Evaluating the state of mind, e.g. depression, anxiety
• CPC Class Codes: A61B 5/4812 Detecting sleep stages or cycles
• CPC Class Codes: A61B 5/681 Wristwatch-type devices
• CPC Class Codes: A61B 5/6824 Arm or wrist
• CPC Class Codes: A61B 5/6885 Monitoring or controlling sensor contact pressure
• 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 5/7246 using correlation, e.g. template matching or determination of similarity
• 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: A61M 2021/0083 : especially for waking up
• CPC Class Codes: A61M 21/00 : Other devices or methods to cause a change in the state of consciousness; Devices for producing or ending sleep by mechanical, optical, or acoustical means, e.g. for hypnosis
• CPC Class Codes: A61M 2230/04 : Heartbeat characteristics, e.g. ECG, blood pressure modulation

Abstract

Embodiments relate generally to wearable computing devices in capturing and deriving physiological characteristic data. More specifically, disclosed are one or more electrodes and methods to determine physiological characteristics using a wearable device (or carried device) and one or more sensors. In one embodiment, a method includes determining a drive signal magnitude for a bioimpedance signal to capture data representing a physiological-related component and selecting the drive signal magnitude as a function of an impedance of a tissue. The bioimpedance signal can be applied to electrodes that are configured to convey the bioimpedance signal to the tissue. In some cases, data representing a value a signal-to-noise (“SNR”) ratio may be adapted to form an adaptive signal-to-noise value. A portion of a received bioimpedance signal may be detected, the received bioimpedance signal being based on the adaptive signal-to-noise value. A physiological characteristic can be derived.

Claims

1. A method comprising:

determining a drive signal magnitude for a bioimpedance signal to capture a sensor signal including data representing a physiological-related component;

selecting the drive signal magnitude as a function of an impedance of a sample of a tissue;

driving the bioimpedance signal to one or more drive electrodes that are configured to convey the bioimpedance signal to the sample of tissue;

adapting data representing a value a signal-to-noise (“

SNR”

) ratio as a function of the impedance of the sample of the tissue to form an adaptive signal-to-noise value;

detecting a portion of the physiological-related signal component from a received bioimpedance signal as the sensor signal based on the adaptive signal-to-noise value; and

deriving a physiological characteristic from the physiological-related signal component.

2. The method of claim 1, wherein selecting the drive signal magnitude comprises:

selecting a drive current magnitude.

3. The method of claim 1, wherein selecting the drive signal magnitude comprises:

determining a dynamic range of operation based on the impedance of the sample of tissue; and

selecting a drive current magnitude for the dynamic range of operation.

4. The method of claim 1, further comprising:

adjusting a gain of a channel based on impedance of the sample of the tissue.

5. The method of claim 4, wherein adjusting the gain of the channel comprises:

adjusting the gain of the channel based on the received bioimpedance signal.

6. The method of claim 1, wherein detecting a portion of the physiological-related signal component comprises:

extracting the portion of the physiological-related signal component in the time-domain.

7. The method of claim 1, further comprising:

determining a state of contact for the drive electrodes and sink electrodes; and

generating data representing the state of contact for the drive electrodes and the sink electrodes.

8. The method of claim 1, wherein deriving the physiological characteristic from the physiological-related signal component comprises:

determining a heart rate (“

HR”

) signal, a galvanic skin response (“

GSR”

) signals, or a respiration rate (“

RR”

) signal as the physiological characteristic.

9. The method of claim 8, wherein deriving the physiological characteristic from the physiological-related signal component further comprises:

calculating a first value representing a maximal oxygen consumption (“

VO2 max”

) or a second value representing pulse or blood pressure based one or more of the HR and the respiration signal.

10. An apparatus comprising:

a wearable housing;

an array of electrodes disposed at a surface of the wearable housing, at least a portion of the array including electrodes configured to either drive a first signal to a target location or receive a second signal from the target location, the second signal including data representing one or more physiological characteristics;

a signal driver configure to apply an adjustable current signal to a subset of the electrodes, a magnitude of the adjustable current signal being a function of an impedance of tissue;

an adaptive signal-to-noise characterizer configured to determine data representing a value of a signal-to-noise ratio for a portion of the second signal including data representing the one or more physiological characteristics, and further configured to adapt the value of a signal-to-noise ratio; and

a physiological characteristic determinator configured to derive physiological signals representative of one or more physiological characteristics.

11. The apparatus of claim 10, wherein the one or more physiological characteristics comprise one or more of a heart rate, a respiration rate, a galvanic skin resistance value, data representing an affective state or mode, an amount of energy expenditure and an amount of calories expended.

12. The apparatus of claim 10, further comprising:

a drive signal adjuster configured to determine a drive signal magnitude for a bioimpedance signal, and further configured to select the drive signal magnitude as a function of the impedance of the tissue.

13. The apparatus of claim 10, further comprising:

an instrumentation amplifier channel processor configured to determine a first gain, and further configured to apply the first gain; and

a physiological channel processor configured to determine a second gain, and further configured to apply the second gain.

14. The apparatus of claim 13, wherein the second gain is adapted to amplify a heart rate signal or a respiration signal.