METHOD AND APPARATUS FOR MONITORING A SUBJECT FOR FRACTIONAL BLOOD OXYGEN SATURATION

• US 20150018654A1
• Filed: 07/09/2013
• Published: 01/15/2015
• Est. Priority Date: 07/09/2013
• Status: Abandoned Application

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: MESTHA, Lalit Keshav, MANDEL, Barry P., NYSTROM, Peter Johan
• Application Number:
  US13/937,949
• Publication Number:
  US 20150018654A1
• Time in Patent Office: Days
• US Class Current: 600/328
• CPC Class Codes: A61B 5/0022 Monitoring a patient using a global network, e.g. telephone networks, internet
• CPC Class Codes: A61B 5/14546 for measuring analytes not otherwise provided for, e.g. ions, cytochromes
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/6831 Straps, bands or harnesses
• CPC Class Codes: A61B 5/7282 Event detection, e.g. detecting unique waveforms indicative of a medical condition A61B5/4094, A61B5/4818, A61B5/349, A61B5/0823 take precedence
• CPC Class Codes: A61B 5/742 using visual displays A61B5/339 takes precedence

Abstract

What is disclosed is a system and method for monitoring a subject of interest for fractional blood oxygen saturation using an apparatus that can be comfortably worn by the subject around an area of exposed skin where a photoplethysmographic (PPG) signal can be registered. In one embodiment, the apparatus is a reflective or transmissive wrist-worn device with emitter/detector pairs fixed to an inner side of a band with at least three illuminators, each emitting source light at a different wavelength band. Each photodetector comprises sensors that are sensitive to a wavelength band of a respective illuminator. Each photodetector measures an intensity of sensed light emitted by a respective illuminator. The signal obtained by the sensors comprises a continuous PPG signal. The continuous PPG signal analyzed for fractional blood oxygen saturation levels and communicated to a remote device. Various embodiments are disclosed.

Claims

1. A method for monitoring a subject of interest for fractional blood oxygen saturation, the method comprising:

activating an apparatus comprising at least one emitter/detector pair with at least three illuminators each emitting source light at a different wavelength band, and fixed to an inner side of a band worn circumferentially around an area of exposed skin by a subject of interest being monitored for fractional blood oxygen saturation, each detector comprises at least one sensor that is sensitive to a wavelength band of a respective illuminator, each detector measuring an intensity of received light emitted by a respective illuminator, said measurements comprising a continuous photoplethysmographic (PPG) signal for said subject, each illuminator being separated from its paired detector by a distance D; and

analyzing said continuous PPG signal for a determination of fractional blood oxygen saturation.

2. The method of claim 1, wherein said apparatus is a transmissive device where distance D separating each illuminator and paired detector defines a chord of living tissue through which said emitted source light passes, said distance being less than 75% of a diametrical distance of the area where said band is being worn, each detector measuring an intensity of light passing through said chord of living tissue.

3. The method of claim 1, wherein said apparatus is a reflective device, distance D is a distance between each illuminator and paired detector as measured around said circumference, said emitted light impacting said skin surface at an angle θ

_L, each detector measuring an intensity of light reflecting off a surface of skin at an angle θ

_R, where 0°

<

(θ

_L,θ

_R)<

90°

.

4. The method of claim 1, wherein multiple emitter/detector pairs are fixed circumferentially around an inner side of said band.

5. The method of claim 1, wherein a wavelength band of illuminators is centered around wavelength any of:

660 nm, 805 nm, 880 nm, 950 nm.

6. The method of claim 1, wherein each emitter/detector pair is configured to emit/detect a different wavelength band.

7. The method of claim 1, wherein said fractional blood oxygen saturation comprises:

8. The method of claim 1, further comprising:

processing signals received by said detectors to generate a ratio; and

calibrating said ratio to an approved standard.

9. The method of claim 1, further comprising:

obtaining information from each of said emitter/detector pairs; and

increasing an accuracy of said measurements by performing any of;

averaging signals, discarding signals, weighting signals based on a statistical analysis, and discarding intensity values determined to be below a level of acceptability.

10. The method of claim 1, further comprising any of:

activating said illuminators to emit source light for a desired length of time; and

turning said illuminators ON/OFF according to a pre-defined interval.

11. The method of claim 1, further comprising communicating said fractional blood oxygen saturation to a remote device comprising any of:

a smartphone, a Wi-Fi router, an I-Pad, a Tablet-PC, a laptop, and a desktop computer.

12. The method of claim 11, said remote device further comprising any of:

a USB connection, memory, a transmitter, a receiver, a display, a storage device, and a connection for delivering power from said remote device.

13. The method of claim 11, wherein said remote device turns said illuminators ON/OFF according to a pre-defined schedule.

14. The method of claim 11, wherein said communication occurs in response to said fractional blood oxygen saturation being outside a pre-defined limit of acceptability.

15. The method of claim 11, wherein said communication comprises any of:

text, email, picture, graph, chart, and pre-recorded message.

16. An apparatus for monitoring a subject of interest for fractional blood oxygen saturation, the apparatus comprising:

at least one emitter/detector pair with at least three illuminators each emitting source light at a different wavelength band, and fixed to an inner side of a band worn circumferentially around an area of exposed skin by a subject of interest being monitored for fractional blood oxygen saturation, each detector comprises at least one sensor that is sensitive to a wavelength band of a respective illuminator, each detector measuring an intensity of received light emitted by a respective illuminator, said measurements comprising a continuous photoplethysmographic (PPG) signal for said subject, each illuminator being separated from its paired detector by a distance D; and

a processor executing machine readable program instruction for analyzing said continuous PPG signal for a determination of fractional blood oxygen saturation.

17. The apparatus of claim 16, wherein said apparatus is a transmissive device where distance D separating each illuminator and paired detector defines a chord of living tissue through which said emitted source light passes, said distance being less than 75% of a diametrical distance of the area where said band is being worn, each detector measuring an intensity of light passing through said chord of living tissue.

18. The apparatus of claim 16, wherein said apparatus is a reflective device, distance D is a distance between each illuminator and paired detector as measured around said circumference, said emitted light impacting said skin surface at an angle θ

_L, each detector measuring an intensity of light reflecting off a surface of skin at an angle θ

_R, where 0°

<

(θ

_L,θ

_R)<

90°

.

19. The apparatus of claim 16, wherein multiple emitter/detector pairs are fixed circumferentially around an inner side of said band.

20. The apparatus of claim 16, wherein a wavelength band of illuminators is centered around wavelength any of:

660 nm, 805 nm, 880 nm, 950 nm.

21. The apparatus of claim 16, wherein each emitter/detector pair is configured to emit/detect a different wavelength band.

22. The apparatus of claim 16, wherein said fractional blood oxygen saturation comprises:

23. The apparatus of claim 16, said processor further performing:

processing signals received by said detectors to generate a ratio; and

calibrating said ratio to an approved standard.

24. The apparatus of claim 16, said processor further performing:

obtaining information from each of said emitter/detector pairs; and

increasing an accuracy of said measurements by performing any of;

averaging signals, discarding signals, weighting signals based on a statistical analysis, and discarding intensity values determined to be below a level of acceptability.

25. The apparatus of claim 16, said processor further performing any of:

activating said illuminators to emit source light for a desired length of time; and

turning said illuminators ON/OFF according to a pre-defined interval.

26. The apparatus of claim 16, said processor communicating said fractional blood oxygen saturation to a remote device comprising any of:

a smartphone, a Wi-Fi router, an I-Pad, a Tablet-PC, a laptop, and a desktop computer.

27. The apparatus of claim 26, said remote device further comprising any of:

a USB connection, memory, a transmitter, a receiver, a display, a storage device, and a connection for delivering power from said remote device.

28. The apparatus of claim 26, wherein said remote device turns said illuminators ON/OFF according to a pre-defined schedule.

29. The apparatus of claim 26, wherein said communication occurs in response to said fractional blood oxygen saturation being outside a pre-defined limit of acceptability.

30. The apparatus of claim 26, wherein said communication comprises any of:

text, email, picture, graph, chart, and pre-recorded message.