Systems and methods for video-based monitoring of vital signs

• US 10,398,353 B2
• Filed: 02/14/2017
• Issued: 09/03/2019
• Est. Priority Date: 02/19/2016
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Covidien LP (Medtronic Plc)
• Inventors: Addison, Paul Stanley, Foo, David, Jacquel, Dominique
• Primary Examiner(s): Grant, II, Jerome
• Application Number:
  US15/432,063
• Publication Number:
  US 20170238805A1
• Time in Patent Office: 931 Days
• Field of Search: 382128
• CPC Class Codes: A61B 2562/0233 Special features of optical sensors or probes classified in A61B5/00
• CPC Class Codes: A61B 2576/00 Medical imaging apparatus involving image processing or analysis A61B1/00009, A61B6/52 and A61B8/52 take precedence; image processing per se G06T; details of algorithms for analysing medical images G06T7/0012
• CPC Class Codes: A61B 5/0077 Devices for viewing the surface of the body, e.g. camera, magnifying lens
• 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 5/024 Detecting, measuring or recording pulse rate or heart rate A61B5/0205, A61B5/021 take precedence
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/0816 Measuring devices for examining respiratory frequency measuring frequency of electric signals G01R23/00
• CPC Class Codes: A61B 5/1032 Determining colour for diagnostic purposes measuring colour in general G01J3/46
• CPC Class Codes: A61B 5/1176 Recognition of faces
• CPC Class Codes: A61B 5/14542 for measuring blood gases A61B5/14551 takes precedence
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/441 Skin evaluation, e.g. for skin disorder diagnosis
• CPC Class Codes: A61B 5/6843 Monitoring or controlling sensor contact pressure
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61B 5/7221 Determining signal validity, reliability or quality A61B5/7207 and A61B5/7217 take precedence
• CPC Class Codes: A61B 5/7246 using correlation, e.g. template matching or determination of similarity
• CPC Class Codes: A61B 5/7253 characterised by using transforms
• 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: A61B 5/7425 Displaying combinations of multiple images regardless of image source, e.g. displaying a reference anatomical image with a live image geometric transforms for image registration G06T3/14; enhancement using image fusion G06T5/50; algorithms for registration of images G06T7/30
• CPC Class Codes: A61B 5/743 Displaying an image simultaneously with additional graphical information, e.g. symbols, charts, function plots
• CPC Class Codes: A61B 5/746 : Alarms related to a physiological condition, e.g. details of setting alarm thresholds or avoiding false alarms alarms per se G08B
• CPC Class Codes: A61B 5/748 : Selection of a region of interest, e.g. using a graphics tablet
• CPC Class Codes: A61B 5/7485 : Automatic selection of region of interest

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.

Claims

1. A video-based method of measuring a patient'"'"'s vital sign, comprising:

receiving a video signal from a video camera, the video signal 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 regions, each region including exposed skin of the patient;

identifying a frequency content of each color signal;

selecting two or more non-adjacent, non-overlapping regions that have a shared frequency content comprising a modulation at a shared frequency;

combining the color signals of the selected regions;

measuring a vital sign from the combined color signal; and

outputting the vital sign for further processing or display.

2. The method of claim 1, wherein combining comprises averaging the color signals from the selected regions.

3. The method of claim 2, wherein the selected regions have different sizes.

4. The method of claim 1, wherein the vital sign comprises heart rate.

5. The method of claim 4, wherein measuring the heart rate comprises accumulating frequency peaks from the combined signal, selecting a median frequency, and updating a running average heart rate from the selected frequency.

6. The method of claim 3, further comprising updating the selected regions by adding or removing regions from the selected regions based on the frequency content of each region.

7. The method of claim 1, further comprising calculating a statistic of the combined color signal, wherein the statistic comprises an amplitude, a variability, a skew, or a signal to noise ratio.

8. The method of claim 7, wherein combining the color signals comprises applying a weight to each color signal that is being combined, the weight being based on the statistic.

9. The method of claim 7, further comprising determining a weight for the vital sign, the weight being based on the statistic, and adding the vital sign to a running average based on the weight.

10. The method of claim 2, wherein selecting the two or more non-adjacent, non-overlapping regions further comprises selecting regions that satisfy a quality criterion, and wherein the quality criterion comprises a signal to noise ratio that satisfies a threshold, or a skew value that satisfies a threshold.

11. The method of claim 10, further comprising removing a color signal from the combined color signal upon failure of the removed color signal to satisfy the criterion.

12. The method of claim 1, wherein extracting the time-varying color signal comprises extracting two time-varying color signals for each region, and wherein measuring the vital sign comprises measuring oxygen saturation from the two time-varying color signals.

13. A camera-based method of measuring a patient'"'"'s vital sign, comprising:

receiving an image signal from a camera having a field of view encompassing exposed skin of a patient, the image signal comprising a sequence of image frames over time;

within the field of view, identifying a plurality of regions;

for each region of the plurality, extracting an intensity signal comprising a time-varying light intensity detected in the region;

selecting regions whose intensity signals comprise a modulation at a shared frequency, wherein the selected regions are non-adjacent and non-overlapping in the image frame;

combining the intensity signals of the selected regions to produce a combined intensity signal; and

measuring heart rate of the patient from the combined intensity signal.

14. The method of claim 13, wherein the measured vital sign is a first measured vital sign, and wherein the method further comprises:

selecting a second set of regions whose intensity signals comprise a second modulation at a second, different, shared frequency, wherein the second set of selected regions are non-adjacent in the image frame;

combining the intensity signals of the second set of selected regions to produce a second combined intensity signal; and

measuring respiration rate of the patient from the second combined intensity signal.

15. The method of claim 14, further comprising displaying the image signal on a display, highlighting on the display the selected regions for the first vital sign, and highlighting on the display the second, different set of selected regions for the second vital sign.

16. The method of claim 13, wherein the modulation at the shared frequency is above an amplitude threshold.

17. The method of claim 13, wherein extracting the intensity signal for each region comprises extracting a red intensity signal comprising a time-varying average of red values in the region, a green intensity signal comprising a time-varying average of green values in the region, and a blue intensity signal comprising a time-varying average of blue values in the region.

18. A camera-based method of measuring a patient'"'"'s vital sign, comprising:

receiving an image signal from a camera having a field of view encompassing exposed skin of a patient;

receiving a user input identifying a region in the image signal;

measuring a first vital sign of the patient, comprising;

from the region, selecting a first set of pixels that exhibit a first modulation at a first shared frequency, wherein the first selected pixels are non-contiguous and non-overlapping; and

measuring the first vital sign of the patient from the selected first pixels; and

outputting the first measured vital sign for further processing or display.

19. The method of claim 18, further comprising:

measuring and outputting a second vital sign of the patient, comprising;

from the region, selecting a second set of pixels that exhibit a second modulation at a second shared frequency different from the first shared frequency, wherein the second selected pixels are non-contiguous;

measuring the second vital sign of the patient from the selected second pixels.

20. The method of claim 19, wherein the first vital sign comprises heart rate and the second vital sign comprises respiration rate.

21. The method of claim 18, further comprising receiving a second user input moving the region to a new location, and subsequently measuring the first vital sign from the new location.

22. The method of claim 18, further comprising displaying a number derived from the first measured vital sign, and triggering an alarm based on the displayed number and stored alarm conditions, wherein the stored alarm conditions omit a sensor-off or sensor-disconnect alarm.