Systems and methods for determining cardiac output

• US 8,977,348 B2
• Filed: 12/21/2012
• Issued: 03/10/2015
• Est. Priority Date: 12/21/2012
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Covidien LP (Medtronic Plc)
• Inventors: Su, Mark, Wood, Lockett
• Primary Examiner(s): REMALY, MARK DONALD
• Application Number:
  US13/723,766
• Publication Number:
  US 20140180136A1
• Time in Patent Office: 809 Days
• Field of Search: None
• US Class Current: 600/479
• CPC Class Codes: A61B 5/022 by applying pressure to close blood vessels, e.g. against the skin; Ophthalmodynamometers
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/029 Measuring or recording blood output from the heart, e.g. minute volume A61B8/065 takes precedence
• CPC Class Codes: A61B 5/0295 using plethysmography, i.e. measuring the variations in the volume of a body part as modified by the circulation of blood therethrough, e.g. impedance plethysmography
• CPC Class Codes: A61B 5/7221 Determining signal validity, reliability or quality A61B5/7207 and A61B5/7217 take precedence

Abstract

A system is provided including a thoracic bio-impedance or bio-reactance (TBIR) analysis module, a photoplethysmograph (PPG) analysis module, and a cardiac output module. The TBIR module is configured to obtain TBIR information from a TBIR detector, and the PPG analysis module is configured to obtain PPG information from a PPG detector. The cardiac output module is configured to determine the cardiac output of a patient using the TBIR information and the PPG information.

Claims

1. A method for determining a cardiac output of a patient comprising:

obtaining a thoracic bio-impedance or bio-reactance (TBIR) signal from a TBIR detector configured to detect TBIR activity of the patient;

electronically measuring a voltage of the TBIR signal to determine an impedance value;

determining a first cardiac output value for the patient from a change in the impedance value over a heart cycle;

obtaining a photoplethysmographic (PPG) signal from a PPG detector configured to detect PPG activity of the patient;

calculating a ratio of first and second peaks in the PPG signal;

determining a second cardiac output value for the patient from the ratio;

determining, at a processor, a subsequent cardiac output of the patient from the first and second cardiac output values.

2. The method of claim 1, wherein the subsequent cardiac output of the patient is determined using at least one of a comparison or a combination of the first and second cardiac output values.

3. The method of claim 2, further comprising:

obtaining TBIR signal quality information corresponding to a quality of the TBIR signal; and

obtaining PPG signal quality information corresponding to a quality of the PPG signal;

wherein the at least one of the comparison or the combination is performed using the TBIR signal quality information and the PPG signal quality information.

4. The method of claim 1, wherein

determining the first cardiac output value includes using a pulse rate determined at least in part from the PPG signal.

5. The method of claim 1, further comprising obtaining blood pressure information from a blood pressure detector, wherein

determining the second cardiac output value includes using the blood pressure information obtained from the blood pressure detector.

6. The method of claim 1, wherein the subsequent cardiac output of the patient is determined using a combination of the first and second cardiac output values.

7. The method of claim 6, wherein the combination comprises a weighted combination.

8. The method of claim 7, wherein a weight for the weighed combination is based on one or more signal quality metrics of the TBIR signal or the PPG signal.

9. The method of claim 1, wherein the subsequent cardiac output of the patient is determined using a comparison of the first and second cardiac output values.

10. The method of claim 3, wherein the TBIR signal quality information comprises a signal to noise ratio.

11. The method of claim 3, wherein the TBIR signal quality information comprises a presence or amount of artifact.

12. The method of claim 3, wherein the TBIR signal quality information comprises information about a positive end expiratory pressure.

13. The method of claim 3, wherein the TBIR signal quality information comprises a physiologic condition of the patient.

14. The method of claim 3, wherein the TBIR signal quality information comprises an amount of match between the obtained TBIR signal and an expected characteristic of the TBIR signal.

15. The method of claim 3, wherein the PPG signal quality information comprises a signal to noise ratio.

16. The method of claim 3, wherein the PPG signal quality information comprises a presence or amount of artifact.

17. The method of claim 3, wherein the PPG signal quality information comprises a physiologic condition of the patient.

18. The method of claim 3, wherein the PPG signal quality information comprises an amount of match between the obtained PPG signal and an expected characteristic of the PPG signal.

19. The method of claim 1, wherein the subsequent cardiac output of the patient is determined using a selection of the first cardiac output value or the second cardiac output value.

20. The method of claim 1, wherein determining the first cardiac output value from the change in the impedance value comprises utilizing an empirically derived relationship.

21. The method of claim 1, wherein determining the second cardiac output value from the ratio comprises utilizing an empirically derived relationship.

22. The method of claim 1 further comprising obtaining blood pressure information from a blood pressure detector, and using the blood pressure information to determine the subsequent cardiac output of the patient.