System and methods for video-based monitoring of vital signs

Patent metadata

Field	Value
Publication number	US-10702188-B2
Application number	US-201916450010-A
Country	US
Kind code	B2
Filing date	Jun 24, 2019
Priority date	Feb 19, 2016
Publication date	Jul 7, 2020
Grant date	Jul 7, 2020

Abstract

The present invention relates to the field of medical monitoring, and in particular non-contact, video-based monitoring of pulse rate, respiration rate, motion, and oxygen saturation. Systems and methods are described for capturing images of a patient, producing intensity signals from the images, filtering those signals to focus on a physiologic component, and measuring a vital sign from the filtered signals.

First claim

What is claimed is:

1. A video-based method of measuring a patient's vital sign, comprising:
generating a video signal from a video camera having a field of view that includes exposed skin of a patient;
extracting from the video signal a plurality of time-varying intensity signals;
combining two or more of the time-varying intensity signals within a region of the field of view to produce a regional intensity signal;
transforming the regional intensity signal into the frequency domain to produce a regional frequency signal;
accumulating peaks in the regional frequency signal over a sliding time window;
selecting a median frequency from the accumulated peaks;
converting the median frequency into a measured vital sign value and adding the measured vital sign value to a running average; and
outputting the averaged vital sign value for further processing or display.

2. The method of claim 1 , wherein the region is selected based on a strength of modulations of intensity signals in the region.

3. The method of claim 1 , wherein the region includes non-adjacent areas or pixels.

4. The method of claim 1 , further comprising removing peaks from the accumulated peaks when they reach an age limit.

5. The method of claim 1 , further comprising discarding peaks outside of a physiologic limit.

6. The method of claim 1 , further comprising discarding the measured vital sign value when it differs from the running average by more than a defined amount.

7. The method of claim 1 , further comprising discarding peaks if they are sub-harmonics of already identified peaks.

8. The method of claim 1 , further comprising identifying a frequency content of each of said plurality of time-varying intensity signals, averaging the color signals from said plurality of time-varying intensity signals, and de-noising the signal.

9. The method of claim 8 , further comprising performing a fast Fourier transform operation over a sliding time window to identify frequency components of said plurality of time-varying intensity signals.

10. The method of claim 1 , wherein the vital sign comprises respiration rate or heart rate.

11. The method of claim 10 , wherein the vital sign comprises heart rate.

12. A video-based method of measuring a patient's vital sign, comprising:
generating a video signal from a video camera having a field of view that includes exposed skin of a patient;
extracting from the video signal a time-varying color signal for each of a plurality of pixels in the field of view;
identifying a frequency content of each color signal;
combining color signals within a region of the field of view;
measuring said vital sign from the combined color signal, including over a period of time, accumulating frequency peaks from the combined signal, selecting a median frequency and updating a running average vital sign value of a patient by converting the median frequency into a measured vital sign value and adding the measured vital sign value to the running average, wherein accumulating frequency peaks comprises cross-correlating the frequency spectrum of each color signal to amplify results; and
outputting the updated average vital sign value for further processing or display.

13. The method of claim 12 , wherein said colors comprise red, green and blue, and wherein cross-correlating the frequency spectrum of each color signal provides four spectrums that are analyzed to select and accumulate peaks.

14. The method of claim 13 , wherein said cross-correlated spectrum is calculated by multiplying or summing existing spectrums together.

15. The method of claim 14 , wherein individual spectrums are scaled prior to multiplying or summing based on weighting parameters.

16. The method of claim 15 , wherein said weighting parameters are based upon the relative numbers of colors of pixels of said video camera.

17. The method of claim 12 , further comprising de-noising the color signal.

18. The method of claim 12 , wherein said vital sign comprises respiration rate or heart rate.

19. The method of claim 18 , wherein said vital sign comprises heart rate.

20. A video-based method of measuring a patient's vital sign, comprising:
generating a video signal from a video camera having a field of view that includes exposed skin of a patient;
extracting from the video signal a time-varying color signal for each of a plurality of pixels in the field of view;
identifying a frequency content of each color signal;
combining color signals within a region of the field of view;
measuring said vital sign from the combined color signal, including over a period of time, accumulating frequency peaks from the combined signal, selecting a median frequency and updating a running average vital sign value of a patient by converting the median frequency into a measured vital sign value and adding the measured vital sign value to the running average, wherein accumulating frequency peaks comprises adding frequencies multiple times based on a peak's relative height, with harmonics of already added frequencies only added once; and
outputting the updated average vital sign value for further processing or display.

21. The method of claim 20 , wherein said vital sign comprises heart rate.

Assignees

• Covidien Lp

Inventors

• Addison Paul S
• Foo David
• Jacquel Dominique

Classifications

• A61B2562/0233

  Special features of optical sensors or probes classified in A61B5/00 · CPC title

• A61B5/6843

  Monitoring or controlling sensor contact pressure · CPC title

• A61B5/0077

  Devices for viewing the surface of the body, e.g. camera, magnifying lens · CPC title

• A61B5/0205

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

• A61B5/441

  Skin evaluation, e.g. for skin disorder diagnosis · CPC title