Methods and Systems for Detecting a Sensor Off Condition Using A Reference Ambient Characteristic

• US 20140180042A1
• Filed: 12/20/2012
• Published: 06/26/2014
• Est. Priority Date: 12/20/2012
• Status: Abandoned Application

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Covidien LP (Medtronic Plc)
• Inventors: Addison, Paul Stanley, Watson, James Nicholas
• Application Number:
  US13/723,150
• Publication Number:
  US 20140180042A1
• Time in Patent Office: Days
• US Class Current: 600/324
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/6815 Ear
• CPC Class Codes: A61B 5/6824 Arm or wrist
• CPC Class Codes: A61B 5/6826 Finger
• CPC Class Codes: A61B 5/6829 Foot or ankle
• CPC Class Codes: A61B 5/6831 Straps, bands or harnesses
• CPC Class Codes: A61B 5/6843 Monitoring or controlling sensor contact pressure
• CPC Class Codes: A61B 5/6844 Monitoring or controlling distance between sensor and tissue
• CPC Class Codes: A61B 5/7221 Determining signal validity, reliability or quality A61B5/7207 and A61B5/7217 take precedence

Abstract

A physiological monitoring system may use photonic signals at one or more wavelengths to determine physiological parameters. During monitoring, a physiological sensor may become improperly positioned, which may affect the physiological attenuation of the photonic signals, and accordingly a detected light signal. The detected light signal may include an ambient light component and a signal component corresponding to the one or more wavelengths of light. The physiological monitoring system may determine a reference characteristic based on the ambient light component, and compare the signal component with the ambient light component to determine a sensor-off condition.

Claims

1. A method for determining whether a physiological sensor is properly positioned on a subject, the method comprising:

receiving a detected light signal, wherein the light signal comprises an ambient light signal component and a signal component corresponding to a wavelength of light emitted by the physiological sensor;

processing the detected light signal, using processing equipment, to generate a first signal corresponding to the ambient light signal component;

processing the detected light signal, using the processing equipment, to generate a second signal corresponding to the ambient light signal component and the signal component;

determining, using the processing equipment, at least one reference characteristic based on the first signal;

comparing, using the processing equipment, the second signal to the at least one reference characteristic; and

determining, using the processing equipment, whether the physiological sensor is properly positioned based on the comparison.

2. The method of claim 1, wherein the physiological sensor comprises a pulse oximetry sensor.

3. The method of claim 1, wherein determining the at least one reference characteristic comprises generating a threshold based on at least one particular value of the first signal.

4. The method of claim 3, wherein the at least one particular value of the first signal comprises an initial value of the first signal.

5. The method of claim 3, wherein the at least one particular value of the first signal comprises a value selected from the first signal at a particular time interval.

6. The method of claim 3, wherein determining whether the physiological sensor is properly positioned comprises determining whether the second signal crosses the threshold.

7. The method of claim 1, wherein the at least one reference characteristic comprises a first reference characteristic corresponding to a first value of the first signal and a second reference characteristic corresponding to a second value of the first signal, the method further comprising:

determining a first difference between the second signal and the first value;

determining a second difference between the second signal and the second value; and

determining a difference between the first difference and the second difference, wherein determining whether the physiological sensor is properly positioned is based on the determined difference.

8. The method of claim 7, wherein the first difference corresponds to a maximum difference between the second signal and the first signal, and the second difference corresponds to a minimum difference between the second signal and the first signal.

9. The method of claim 1, further comprising setting a sensor-off flag when it is determined that the physiological sensor is not properly positioned.

10. The method of claim 9, further comprising resetting the sensor-off flag when it is subsequently determined that the physiological sensor is properly positioned.

11. A system for determining whether a physiological sensor is properly positioned on a subject, the system comprising:

processing equipment configured to;

receive a detected light signal, wherein the light signal comprises an ambient light signal component and a signal component corresponding to a wavelength of light emitted by the physiological sensor;

process the detected light signal to generate a first signal corresponding to the ambient light signal component;

process the detected light signal to generate a second signal corresponding to the ambient light signal component and the signal component;

determine at least one reference characteristic based on the first signal;

compare the second signal to the at least one reference characteristic; and

determine whether the physiological sensor is properly positioned based on the comparison.

12. The system of claim 11, wherein the physiological sensor comprises a pulse oximetry sensor.

13. The system of claim 11, wherein the processing equipment is further configured to determine the at least one reference characteristic by generating a threshold based on at least one particular value of the first signal.

14. The system of claim 13, wherein the at least one particular value of the first signal comprises an initial value of the first signal.

15. The system of claim 13, wherein the at least one particular value of the first signal comprises a value selected from the first signal at a particular time interval.

16. The system of claim 13, wherein the processing equipment is further configured to determine whether the physiological sensor is properly positioned by determining whether the second signal crosses the threshold.

17. The system of claim 11, wherein the at least one reference characteristic comprises a first reference characteristic corresponding to a first value of the first signal and a second reference characteristic corresponding to a second value of the first signal, wherein the processing equipment is further configured to:

determine a first difference between the second signal and the first value;

determine a second difference between the second signal and the second value;

determine a difference between the first difference and the second difference; and

determine whether the physiological sensor is properly positioned further based on the determined difference.

18. The system of claim 17, wherein the first difference corresponds to a maximum difference between the second signal and the first signal, and the second difference corresponds to a minimum difference between the second signal and the first signal.

19. The system of claim 11, wherein the processing equipment is further configured to set a sensor-off flag when it is determined that the physiological sensor is not properly positioned.

20. The system of claim 19, wherein the processing equipment is further configured to reset the sensor-off flag when it is subsequently determined that the physiological sensor is properly positioned.