Methods and systems for determining a probe-off condition in a medical device

• US 8,922,788 B2
• Filed: 12/22/2012
• Issued: 12/30/2014
• Est. Priority Date: 12/22/2012
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Covidien LP (Medtronic Plc)
• Inventors: Addison, Paul Stanley, Watson, James Nicholas
• Primary Examiner(s): Ton, Tri T
• Application Number:
  US13/726,075
• Publication Number:
  US 20140176944A1
• Time in Patent Office: 738 Days
• Field of Search: 356614-615, 356/620, 356/622, 600/310, 600/336, 600/324, 600330-334, 600/481, 600/509, 600544-547
• US Class Current: 356/614
• CPC Class Codes: A61B 2562/0233 Special features of optical sensors or probes classified in A61B5/00
• CPC Class Codes: A61B 5/0059 using light, e.g. diagnosis by transillumination, diascopy, fluorescence A61B5/0093, A61B5/1455, A61B5/02416 and A61B5/0261 take precedence
• CPC Class Codes: A61B 5/061 Determining position of a probe within the body employing means separate from the probe, e.g. sensing internal probe position employing impedance electrodes on the surface of the body A61B1/00158 takes precedence
• CPC Class Codes: A61B 5/1455 using optical sensors, e.g. spectral photometrical oximeters
• CPC Class Codes: A61B 5/14552 Details of sensors specially adapted therefor
• CPC Class Codes: A61B 5/4887 Locating particular structures in or on the body
• CPC Class Codes: A61B 5/6814 Head
• CPC Class Codes: A61B 5/6815 Ear
• CPC Class Codes: A61B 5/6822 Neck
• 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 5/684 Indicating the position of the sensor on the body
• 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 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61B 5/7221 Determining signal validity, reliability or quality A61B5/7207 and A61B5/7217 take precedence
• CPC Class Codes: G01B 11/14 for measuring distance or clearance between spaced objects or spaced apertures G01B11/26 takes precedence; rangefinders G01C3/00

Abstract

A physiological monitoring system may determine a probe-off condition. A physiological sensor may be used to emit one or more wavelengths of light. A received light signal may be processed to obtain a light signal corresponding to the emitted light and an ambient signal. The signals may be analyzed to identify similar behavior. The system may determine whether the physiological sensor is properly positioned based on the analysis.

Claims

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

receiving a light signal using the physiological sensor;

processing, using processing equipment, the light signal to obtain a first signal corresponding to ambient light;

processing, using the processing equipment, the light signal to obtain a second signal corresponding to an emitted photonic signal and ambient light;

analyzing, using the processing equipment, the first signal and the second signal to identify similar signal amplitude behavior; and

determining, using the processing equipment, that the physiological sensor is not properly positioned based on the analysis.

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

3. The method of claim 1, wherein receiving the light signal comprises receiving light from a first light emitting diode configured to emit a first wavelength of light and from a second light emitting diode configured to emit a second wavelength of light.

4. The method of claim 1, wherein the light signal is detected by a photoelectric detector.

5. The method of claim 1, wherein analyzing the first signal and the second signal to identify similar signal amplitude behavior comprises determining whether a difference in amplitudes of the first and second signals is substantially constant.

6. The method of claim 1, wherein analyzing the first signal and the second signal to identify similar signal amplitude behavior comprises determining whether a difference in slopes of the first and second signals is substantially constant.

7. The method of claim 1, wherein analyzing the first signal and the second signal to identify similar signal amplitude behavior comprises compensating for nonlinearity.

8. The method of claim 1, wherein analyzing the first signal and the second signal to identify similar signal amplitude behavior comprises:

determining a value based on the first signal and the second signal; and

comparing the value to a threshold.

9. The method of claim 8, wherein the value is selected from the group consisting of difference between the first and second signal, a flatness value, a confidence value, a slope value, an amplitude value, and combinations thereof.

10. The method of claim 1, wherein analyzing the first signal and the second signal to identify similar signal amplitude behavior comprises identifying a substantially constant amplitude in at least one of the first signal and the second signal.

11. The method of claim 1, wherein analyzing the first signal and the second signal to identify similar signal amplitude behavior comprises identifying a threshold crossing by both signals at substantially the same time.

12. The method of claim 1, wherein analyzing the first signal and the second signal to identify similar signal amplitude behavior comprises identifying at least one of a mimicking-equal behavior, a mimicking-parallel behavior, or a nonlinear scaling behavior of the first and second signals.

13. The method of claim 1, further comprising providing an indicator that the physiological sensor is not properly positioned.

14. The method of claim 1, further comprising compensating the received light signal for a light drive setting.

23. The method of claim 1, wherein the ambient light corresponds to light received from light sources other than light sources coupled to the physiological sensor.

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

processing equipment configured to;

receive a light signal from the physiological sensor;

process the light signal to obtain a first signal corresponding to ambient light;

process the light signal to obtain a second signal corresponding to an emitted photonic signal and ambient light;

analyze the first signal and the second signal to identify similar signal amplitude behavior; and

determine that the physiological sensor is not properly positioned based on the analysis.

16. The system of claim 15, wherein the processing equipment comprises a pulse oximeter.

17. The system of claim 15, wherein the processing equipment is further configured to determine whether a difference in amplitudes of the first and second signals is substantially constant.

18. The system of claim 15, wherein the processing equipment is further configured to determine whether a difference in slopes of the first and second signals is substantially constant.

19. The system of claim 15, wherein the processing equipment is further configured to:

determine a value based on the first signal and the second signal; and

compare the value to a threshold.

20. The system of claim 15, wherein the processing equipment is further configured to identify a substantially constant amplitude in at least one of the first signal and the second signal.

21. The system of claim 15, wherein the processing equipment is further configured to provide an indicator that the physiological sensor is not properly positioned.

22. The system of claim 15, wherein the processing equipment configured to analyze the first signal and the second signal to identify similar signal amplitude behavior comprises processing equipment configured to identify at least one of a mimicking-equal behavior, a mimicking-parallel behavior, or a nonlinear scaling behavior of the first and second signals.

24. The system of claim 15, wherein the ambient light corresponds to light received from light sources other than light sources coupled to the physiological sensor.