METHODS AND SYSTEMS FOR PHOTOACOUSTIC MONITORING USING INDICATOR DILUTION

• US 20130144147A1
• Filed: 12/05/2011
• Published: 06/06/2013
• Est. Priority Date: 12/05/2011
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Nellcor Puritan Bennett LLC (Medtronic Plc)
• Inventors: Li, Youzhi, Chen, Bo, Wood, Lockett, Borg, Ulf
• Granted Patent: US 9,131,852 B2
• Time in Patent Office: Days
• US Class Current: 600/407
• CPC Class Codes: A61B 2560/0223 of calibration, e.g. protocols for calibrating sensors
• CPC Class Codes: A61B 5/0095 by applying light and detecting acoustic waves, i.e. photoacoustic measurements
• CPC Class Codes: A61B 5/02028 Determining haemodynamic parameters not otherwise provided for, e.g. cardiac contractility or left ventricular ejection fraction
• 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 5/0261 using optical means, e.g. infrared light
• CPC Class Codes: A61B 5/0275 using tracers, e.g. dye dilution
• CPC Class Codes: A61B 5/028 by thermo-dilution
• 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 5/14546 for measuring analytes not otherwise provided for, e.g. ions, cytochromes
• CPC Class Codes: A61B 5/1455 using optical sensors, e.g. spectral photometrical oximeters

Abstract

A patient monitoring system may provide photoacoustic sensing based on an indicator dilution to determine one or more physiological parameters of a subject. The system may detect an acoustic pressure signal, which may include one or more thermo-dilution responses, one or more hemo-dilution responses, or a combination thereof. For example, a thermo-dilution indicator and/or a hemo-dilution indicator may be used to determine one or more hemodynamic parameters. In a further example, an isotonic indicator and a hypertonic indicator may be used to determine one or more hemodynamic parameters of the subject.

Claims

1. A method for determining a physiological parameter of a subject, the method comprising:

providing a photonic signal to a first blood vessel site of the subject;

detecting an acoustic pressure signal from the first blood vessel site using one or more acoustic detectors, wherein the acoustic pressure signal is caused by the absorption of at least some of the photonic signal by one or more constituents at the first blood vessel site, and wherein the acoustic pressure signal comprises a dilution response corresponding to an indicator provided to a second blood vessel site; and

determining at least one physiological parameter of the subject based at least in part on the dilution response.

2. The method of claim 1, wherein at least one physiological parameter is one or more of cardiac output, intrathoracic blood volume, intrathoracic circulatory volume, global end-diastolic volume, pulmonary circulatory volume, and extravascular lung water.

3. The method of claim 1, further comprising generating a photoacoustic signal based at least in part on the acoustic pressure signal, and wherein the determining the at least one physiological parameter comprises determining the at least one physiological parameter based at least in part on one or more characteristics derived from the photoacoustic signal.

4. The method of claim 3, wherein the one or more characteristics are one or more of a value of the photoacoustic signal, a value of a signal derived from the photoacoustic signal, an area under a dilution curve derived from the photoacoustic signal, a time, and a time difference.

5. The method of claim 1, wherein the dilution response comprises a hemo-dilution response.

6. The method of claim 1, wherein the indicator is provided at a temperature different than the temperature of the second blood vessel site, and wherein the dilution response comprises a thermo-dilution response.

7. The method of claim 1, wherein the dilution response comprises a hemo-dilution response and a thermo-dilution response.

8. The method of claim 1, wherein the first blood vessel site is located at an artery of the subject.

9. The method of claim 1, wherein the second blood vessel site is located at a vein of the subject.

10. The method of claim 1, wherein the indicator is at least one of a dye indicator and a saline solution.

11. A system for determining a physiological parameter of a subject, the system comprising:

a light source configured to provide a photonic signal to a first blood vessel site of the subject;

an acoustic detector configured to detect an acoustic pressure signal from the first blood vessel site, wherein the acoustic pressure signal is caused by the absorption of at least some of the photonic signal by one or more constituents at the first blood vessel site, and wherein the acoustic pressure signal comprises a dilution response corresponding to an indicator provided to a second blood vessel site; and

processing equipment configured to determine at least one physiological parameter of the subject based at least in part on the dilution response.

12. The system of claim 11, wherein at least one physiological parameter is one or more of cardiac output, intrathoracic blood volume, intrathoracic circulatory volume, global end-diastolic volume, pulmonary circulatory volume, and extravascular lung water.

13. The system of claim 11, wherein the processing equipment is further configured to:

generate a photoacoustic signal based at least in part on the acoustic pressure signal, and

determine the physiological parameter based at least in part on one or more characteristics derived from the photoacoustic signal.

14. The system of claim 13, wherein the one or more characteristics are one or more of a value of the acoustic pressure signal, a value of a signal derived from the acoustic pressure signal, an area under a dilution curve derived from the acoustic pressure signal, a time, and a time difference.

15. The system of claim 11, wherein the acoustic detector is configured to detect a hemo-dilution response.

16. The system of claim 11, wherein the indicator is provided at a temperature different than the temperature of the second blood vessel site, and wherein the acoustic detector is configured to detect a thermo-dilution response.

17. The system of claim 11, wherein the acoustic detector is configured to detect a hemo-dilution response and a thermo-dilution response.

18. The system of claim 11, wherein the light source configured to provide a photonic signal to the first blood vessel site is configured to provide a photonic signal to an artery of the subject.

19. The system of claim 11, wherein the indicator provided to the second blood vessel site is provided to a vein of the subject.

20. The system of claim 11, wherein the indicator is at least one of a dye indicator and a saline solution.