Photoacoustic spectroscopy method and system to discern sepsis from shock

• US 8,798,704 B2
• Filed: 09/13/2010
• Issued: 08/05/2014
• Est. Priority Date: 09/24/2009
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Covidien LP (Medtronic Plc)
• Inventors: McKenna, Edward M.
• Primary Examiner(s): Koharski, Christopher D
• Assistant Examiner(s): CAREY, MICHAEL JAMES
• Application Number:
  US12/880,308
• Publication Number:
  US 20110071598A1
• Time in Patent Office: 1,422 Days
• Field of Search: 607/62, 600/326
• US Class Current: 600/326
• CPC Class Codes: A61B 5/0095 by applying light and detecting acoustic waves, i.e. photoacoustic measurements
• CPC Class Codes: A61B 5/0261 using optical means, e.g. infrared light
• CPC Class Codes: A61B 5/412 Detecting or monitoring sepsis
• CPC Class Codes: A61B 5/7275 Determining trends in physiological measurement data; Predicting development of a medical condition based on physiological measurements, e.g. determining a risk factor
• CPC Class Codes: A61B 8/06 Measuring blood flow measuring volume flow in general G01F, e.g. G01F1/66, G01F1/72; measuring speed of fluids in general G01P5/00

Abstract

According to various embodiments, a medical system and method for determining a microcirculation parameter of a patient may include a photoacoustic sensor. Specifically, a signal from a photoacoustic sensor may be used to determine if a patient is likely to have sepsis or shock. Although sepsis and shock present similarly with regard to many patient parameters, they may be differentiated by characteristic microcirculation changes.

Claims

1. A method of monitoring a patient, comprising:

using a processor to perform the steps of;

controlling a driver of a light source of a photoacoustic spectroscopy sensor, wherein the light source is configured to emit one or more wavelengths of light;

receiving a signal from the photoacoustic spectroscopy sensor, wherein the signal is representative of a microcirculatory parameter of a patient;

calculating the microcirculatory parameter based at least in part on the signal via one or more algorithms stored in a memory;

determining whether the patient has shock or sepsis based at least in part on the microcirculatory parameter, wherein determining if the patient has sepsis comprises monitoring the microcirculatory parameter over a period of time and determining if a decrease in the microcirculatory parameter is not followed by a rise in the microcirculatory parameter; and

providing an indication of the microcirculatory parameter on a display.

2. The method of claim 1, comprising triggering an alarm when the micro circulatory parameter is less than a predetermined level or outside of a predetermined range.

3. The method of claim 1, comprising;

controlling a driver of a light emitter of a second sensor to receive a second signal related to a clinical parameter, wherein the clinical parameter is of one or more of the patient'"'"'s blood pressure, a heart rate, a respiration rate, a respiration effort, or a temperature;

determining if one or more of the patient'"'"'s blood pressure, the heart rate, the respiration rate, the respiration effort, or the temperature is indicative of possible shock or sepsis; and

activating the driver of light source of the photoacoustic spectroscopy sensor if the clinical parameter is indicative of possible shock or sepsis.

4. The method of claim 1, comprising providing an indication on the display that shock therapy should be started if the patient has shock.

5. The method of claim 1, comprising providing an indication on the display that sepsis therapy should be started if the patient has sepsis.

6. The method of claim 1, wherein determining if the patient has shock comprises monitoring the microcirculatory parameter over a period of time and determining if a decrease in the microcirculatory parameter is followed by a rise in the microcirculatory parameter.

7. A method of monitoring a patient, comprising:

using a processor;

receiving a first signal from a first sensor related to a clinical parameter, wherein the clinical parameter is one or more of a patient'"'"'s blood pressure, a heart rate, a cardiac output, blood constituents, a respiration rate, a respiration effort, or a temperature;

determining if the first signal is associated with a possible sepsis or a possible shock condition;

activating a photoacoustic sensor if the first signal is associated with the possible sepsis or the possible shock condition, wherein activating the photoacoustic sensor comprises providing instructions to drive a light emitter of the photoacoustic sensor;

receiving a second signal from the photoacoustic sensor related to one or more microcirculatory parameters of the patient;

calculating a microcirculatory parameter of the patient based on the second signal; and

distinguishing between sepsis or shock based at least in part on the determined microcirculatory parameter, wherein the distinguishing comprises;

determining that the patient has shock based on a decrease in the microcirculatory parameter followed by a rise in the microcirculatory parameter; and

determining that the patient has sepsis based on a decrease in the microcirculatory parameter not followed by a rise in the microcirculatory parameter.

8. The method of claim 7, comprising triggering an alarm when the microcirculatory parameter is less than a predetermined level or outside of a predetermined range.

9. The method of claim 7, wherein the microcirculatory parameter is related to one or more of the patient'"'"'s blood flow, the patient'"'"'s blood volume, a depth or distribution of the patient'"'"'s microcirculatory vessels, or a concentration of blood constituents in the patient'"'"'s microcirculatory vessels.

11. The method of claim 7, wherein the first signal is associated with the possible sepsis or the possible shock condition if one or more of an decrease in the temperature, an increase in the blood pressure, an increase in the heart rate, an increase in the respiratory rate, or an increase in the respiration effort is determined.

12. The method of claim 7, wherein the first sensor is a pulse oximetry sensor.

13. The method of claim 7, wherein the first sensor is a blood pressure sensor.

14. The method of claim 7, wherein the first sensor is a respiration rate sensor or a respiration effort sensor.

15. The method of claim 7, wherein the first sensor is a cardiac function sensor.

16. The method of claim 7, wherein the first sensor is a temperature sensor.

10. A method of monitoring a patient, comprising:

using a processor to perform the steps of;

controlling a driver of a light emitter of a first sensor;

receiving a first signal from the first sensor related to a clinical parameter, wherein the clinical parameter is associated with a possible sepsis or a possible shock condition;

activating a driver of a light source of a photoacoustic spectroscopy sensor based on an increase or decrease in the clinical parameter, wherein the light source is configured to emit one or more wavelengths of light;

receiving a second signal from an acoustic detector of the photoacoustic spectroscopy sensor, wherein the second signal is representative of a blood flow parameter of a patient;

determining the blood flow parameter based at least in part on the second signal;

determining whether the patient has shock or sepsis based at least in part on the blood flow parameter, wherein determining if the patient has shock comprises monitoring the blood flow parameter over a period of time and determining if a decrease in the blood flow parameter is followed by a rise in the blood flow parameter; and

providing an indication of the blood flow parameter over the period of time on a display, comprising providing a indication of shock if the patient has shock and an indication of sepsis if the patient has sepsis.