Methods and systems for determining a venous signal using a physiological monitor

• US 9,888,871 B2
• Filed: 01/27/2015
• Issued: 02/13/2018
• Est. Priority Date: 01/28/2014
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Covidien LP (Medtronic Plc)
• Inventors: Watson, James N., Addison, Paul S.
• Primary Examiner(s): WINAKUR, ERIC FRANK
• Application Number:
  US14/606,919
• Publication Number:
  US 20150208965A1
• Time in Patent Office: 1,113 Days
• CPC Class Codes: A61B 5/02108 from analysis of pulse wave characteristics
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/1495 Calibrating or testing of in-vivo probes

Abstract

A physiological monitoring system may receive a sensor signal from a physiological sensor. The system may determine a first and second change metric based on the sensor signal, and may determine a venous signal based on the change metrics. In some embodiments, the sensor signal may be a photoplethysmograph signal that includes both arterial and venous information. By subtracting a second change metric from a first change metric, arterial contributions may be substantially removed, resulting in a signal primarily comprising venous information. The venous signal may be indicative of changes in the venous blood, and may be used to determine a physiological parameter, for example, blood pressure. The venous signal may also be used to trigger an event, for example, calibration of a blood pressure measurement.

Claims

1. A method of processing a physiological signal, the method comprising:

receiving the physiological signal from a subject, the signal comprising a first component corresponding to a first wavelength of light and a second component corresponding to a second wavelength of light;

determining, using one or more processors, a first change metric based on a change in a baseline of the first component of the physiological signal;

determining, using one or more processors, a second change metric based on a change in a baseline of the second component of the physiological signal and based on a coefficient associated with arterial oxygen saturation;

determining, using one or more processors, a venous signal based on the first change metric and the second change metric, wherein the venous signal is indicative of changes associated with venous blood; and

monitoring, using one or more processors, a physiological parameter based on the venous signal.

2. The method of claim 1, further comprising:

determining, using one or more processors, a ratio-of-ratios value based on the received physiological signal, wherein the ratio-of-ratios value is associated with arterial oxygen saturation; and

determining, using one or more processors, the coefficient based on the ratio-of-ratio value.

3. The method of claim 1, wherein the first change metric is determined based on the following expression:

4. The method of claim 1, wherein the second metric signal is determined based on the following expression:

5. The method of claim 1, wherein the venous signal is determined based on the following expression:

6. The method of claim 1, wherein the physiological parameter comprises blood pressure.

7. The method of claim 1, wherein the physiological parameter comprises systemic vascular resistance.

8. The method of claim 1, further comprising triggering an event based on the venous signal.

9. The method of claim 8, wherein triggering the event comprises triggering a calibration of a calculation of a physiological parameter.

10. The method of claim 9, wherein the calibration of a calculation of a physiological parameter comprises the calibration of a blood pressure calculation.

11. A system for operating a physiological monitor, the system comprising:

an input configured for receiving a physiological signal from a subject, the signal comprising a first component corresponding to a first wavelength of light and a second component corresponding to a second wavelength of light; and

one or more processors configured to perform operations comprising;

determining a first change metric based on a change in a baseline of the first component of the physiological signal;

determining a second change metric based on a change in a baseline of the second component of the physiological signal and based on a coefficient associated with arterial oxygen saturation;

determining a venous signal based on the first change metric and the second change metric, wherein the venous signal is indicative of changes associated with venous blood; and

determining a physiological parameter based on the venous signal.

12. The system of claim 11, wherein the one or more processors are further configured to perform operations comprising:

determining a ratio-of-ratios value based on the received physiological signal, wherein the ratio-of-ratios value is associated with arterial oxygen saturation; and

determining the coefficient based on the ratio-of-ratio value.

13. The system of claim 11, wherein the first change metric is determined based on the following expression:

14. The system of claim 11, wherein the second metric signal is determined based on the following expression:

15. The system of claim 11, wherein the venous signal is determined based on the following expression:

16. The system of claim 11, wherein the physiological parameter comprises blood pressure.

17. The system of claim 11, wherein the physiological parameter comprises systemic vascular resistance.

18. The system of claim 11, wherein the one or more processors are further configured to perform operations comprising triggering an event based on the venous signal.

19. The system of claim 18, wherein triggering the event comprises triggering a calibration of a calculation of a physiological parameter.

20. The system of claim 19, wherein the calibration of a calculation of a physiological parameter comprises the calibration of a blood pressure calculation.