Physiological measurement system with automatic wavelength adjustment

Patent metadata

Field	Value
Publication number	US-9839381-B1
Application number	US-94927110-A
Country	US
Kind code	B1
Filing date	Nov 18, 2010
Priority date	Nov 24, 2009
Publication date	Dec 12, 2017
Grant date	Dec 12, 2017

Abstract

Disclosed herein is a physiological measurement system that can automatically adjust the number of wavelengths used based on the quality of a sensor signal that is reflective of an optical radiation detected at a sensor after tissue attenuation. The signal quality is examined to determine if it is sufficient to support the use of a full set of wavelengths. If it is determined to be insufficient to support the full set, a reduced number of wavelengths is used.

First claim

What is claimed is:

1. An optical non-invasive physiological measurement system that automatically adjusts a number of wavelengths used in a measurement of physiological parameters, the system comprising:
a plurality of light emitting sources, including at least three light emitting sources, configured to emit light at a plurality of wavelengths, including at least three different wavelengths;
a sensor configured to detect the emitted light after attenuation by body tissue of a patient and output a signal that corresponds to at least one physiological parameter of the body tissue of the patient; and
a processor configured to:
cause a test current, which is less than an operational current, to be provided to one or more of the plurality of the light emitting sources;
measure the quality of a signal output by the sensor in response to detecting the light emitted by the one or more of the plurality of the light emitting sources as a result of the test current;
use the signal output to extrapolate a level of an expected signal output by the sensor when the operational current is supplied to the one or more light emitting sources;
determine if the level of the expected signal output falls within an acceptable range to support the measurement of one or more physiological parameters of the body issue; and
reduce the number of the plurality of light emitting sources that are used in operation to determine a physiological parameter of the body tissue based on the expected signal output, so that fewer light emitting sources are used to determine the physiological parameter when the expected signal output is determined to be insufficient to support the plurality of wavelengths, wherein the expected signal output is determined to be insufficient when a level of the expected signal output for the one or more of the plurality of light emitting sources configured to emit a particular wavelength of the plurality of wavelengths falls outside of the acceptable range.

2. The system of claim 1 , wherein the processor is further configured to reduce by activating only the plurality of light emitting sources configured to emit light at two wavelengths of the plurality of wavelengths when the signal quality is determined to be insufficient to support the plurality of wavelengths.

3. The system of claim 2 , wherein the two wavelengths are 660 nm and 905 nm.

4. The system of claim 2 , wherein the two wavelengths are used to calculate a SpO2 reading.

5. The system of claim 1 , wherein the processor is further configured to increase the number of the plurality of light emitting sources after a reduction by activating the plurality of light emitting sources configured to emit light at the plurality of wavelengths when the signal quality is later determined to be sufficient to support the plurality of wavelengths.

6. The system of claim 5 wherein the plurality of wavelengths comprises eight wavelengths.

7. The system of claim 5 wherein the plurality of wavelengths comprises twelve wavelengths.

8. The system of claim 1 , wherein the processor is further configured to maximize the number of physiological parameters measured when the signal quality is determined to be insufficient to support all of the plurality wavelengths.

9. The system of claim 1 wherein the measurement of signal quality is based on a perfusion measurement made by the system.

10. The system of claim 9 wherein the perfusion measurement is based on a perfusion index.

11. A method of automatically adjusting a number of a plurality of wavelengths used in a physiological measurement system with an emitter assembly comprising a plurality of light emitting sources configured to emit optical radiation at a set of wavelengths, the method comprising:
determining a signal quality of the optical radiation emitted by the plurality of light emitting sources by:
for one or more of the plurality of light emitting sources in the emitter assembly of the physiological measurement system:
providing a first test current, which is less than an operational current, to the light emitting source configured to emit optical radiation at a particular wavelength of the set of wavelengths;
measuring a first sensor signal output by the physiological measurement system upon detection of the optical radiation caused by the providing of the first test current after attenuation by body tissue;
using the first measured sensor signal output to extrapolate a level of an expected sensor signal output in response to the operational current provided to the light emitting source; and
determining whether the extrapolated level of the expected sensor signal output falls within an acceptable range of signal level to support a determination of one or more physiological measurements; and
using fewer wavelengths than the set of wavelengths when the signal quality is insufficient to support the set of wavelengths.

12. The method of claim 11 , wherein the determining step further comprises:
providing a second test current to the light emitting source configured to emit optical radiation at the particular wavelength;
measuring a second sensor signal output by the physiological measurement system upon detection of the optical radiation caused by the providing of the second test current after attenuation by body tissue; and
using the first and the second measured sensor signal outputs to extrapolate a level of expected sensor signal output in response to an operational current provided to the light emitting source.

13. The method of claim 11 , wherein the set of wavelengths comprises eight wavelengths.

14. The method of claim 13 , wherein the using fewer wavelengths step uses four wavelengths.

15. The method of claim 13 , wherein the using fewer wavelengths step uses two wavelengths.

16. The method of claim 15 , wherein one of the two wavelengths is in the red range and the other is in the infrared range.

17. The method of claim 15 , wherein the two wavelengths are at 660 nm and 905 nm.

18. The method of claim 15 , wherein the using fewer wavelengths step uses two wavelengths that are used to calculate a SpO2 reading.

19. The method of claim 11 , wherein the set of wavelengths comprises twelve wavelengths.

20. The method of claim 19 , wherein the using fewer wavelengths step uses eight wavelengths.

21. The method of claim 19 , wherein the using fewer wavelengths step uses four wavelengths.

22. The method of claim 19 , wherein the using fewer wavelengths step uses two wavelengths.

23. The method of claim 13 , wherein the using fewer wavelengths step uses a number of wavelengths that support a determination of a maximum number of physiological measurements.

24. The method of claim 11 , further comprising:
determining the signal quality of the optical radiation emitted by plurality of light emitting sources when fewer wavelengths than the set of wavelengths are being used; and
using the set of wavelengths when the signal quality is sufficient to support the set of wavelengths.

25. The method of claim 11 wherein the using fewer wavelengths adjusts the number of the wavelengths used based on a perfusion measurement made by the physiological measurement system.

26. The method of claim 25 wherein the perfusion measurement is based on a perfusion index.

Assignees

• Weber Walter M
• Al-Ali Ammar
• Cercacor Lab Inc

Inventors

• Weber Walter M
• Al-Ali Ammar

Classifications

• A61B5/7221

  Determining signal validity, reliability or quality (preventing, reducing or removing noise induced by motion artefacts A61B5/7207; noise originating from a therapeutic or surgical apparatus A61B5/7217) · CPC title

• A61B5/7203

  for noise prevention, reduction or removal · CPC title

• A61B5/0059

  using light, e.g. diagnosis by transillumination, diascopy, fluorescence (photoacoustic A61B5/0093; optical measurement of heart rate A61B5/02416; optical measurement of blood flow A61B5/0261; optical measurement of analytes A61B5/1455) · CPC title

• A61B5/0205

  Simultaneously evaluating both cardiovascular conditions and different types of body conditions, e.g. heart and respiratory condition · CPC title

• A61B5/14551 Primary

  for measuring blood gases · CPC title