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

• US 9,462,976 B2
• Filed: 12/16/2014
• Issued: 10/11/2016
• 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:
  US14/572,461
• Publication Number:
  US 20150103360A1
• Time in Patent Office: 665 Days
• Field of Search: None
• US Class Current: 1/1
• 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:

using the physiological sensor to emit a photonic signal comprising at least one wavelength of light;

receiving a light signal using the physiological sensor, wherein the light signal includes at least a contribution corresponding to ambient light;

processing, using processing equipment, the light signal to obtain an ambient signal corresponding to the ambient light contribution;

analyzing, using the processing equipment, the ambient signal to determine whether the ambient signal comprises a feature, wherein the feature of the ambient signal comprises a high level of the ambient signal;

analyzing, using the processing equipment, the light signal to determine whether a portion of the light signal comprises a constant amplitude feature by identifying a flatness value and comparing the flatness value to a threshold; and

determining, using the processing equipment, that the physiological sensor is not properly positioned when the light signal comprises the constant amplitude feature and when the ambient signal comprises the feature.

2. The method of claim 1, wherein analyzing the light signal to determine whether a portion of the light signal comprises substantially constant amplitude comprises at least one of:

comparing the light signal to a target value, analyzing a derivative of the light signal, determining a slope of the light signal, and determining a fractal of the light signal.

3. The method of claim 1, wherein the physiological sensor comprises a photoplethysmography sensor.

4. The method of claim 1, wherein using the physiological sensor to emit the photonic signal comprises energizing at least one light emitting diode.

5. The method of claim 1, wherein receiving the light signal comprises receiving the light signal using a photoelectric detector.

6. The method of claim 1, wherein analyzing the light signal to determine whether a portion of the light signal comprises substantially constant amplitude comprises determining whether an analog-to-digital converter receives a maximum input that it can process.

7. The method of claim 1, further comprising determining a probe-off condition based on the determination that the physiological sensor is not properly positioned.

8. The method of claim 1, further comprising providing an alarm in response to the determination that the physiological sensor is not properly positioned.

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

an emitter configured to emit a photonic signal comprising at least one wavelength of light;

a detector configured to receive a light signal, wherein the light signal includes at least a contribution corresponding to ambient light; and

processing equipment configured to;

process the light signal to obtain an ambient signal corresponding to the ambient light contribution;

analyze the ambient signal to determine whether the ambient signal comprises a feature, wherein the feature of the ambient signal comprises a high level of the ambient signal;

analyze the light signal to determine whether a portion of the light signal comprises a constant amplitude feature by identifying a flatness value and comparing the flatness value to a threshold; and

determine that the physiological sensor is not properly positioned when the light signal comprises the constant amplitude feature and when the ambient signal comprises the feature.

10. The system of claim 9, wherein the processing equipment is configured to analyze the light signal to determine whether a portion of the light signal comprises substantially constant amplitude by performing at least one of the following:

comparing the light signal to a target value, analyzing a derivative of the light signal, determining a slope of the light signal, and determining a fractal of the light signal.

11. The system of claim 9, wherein the physiological sensor comprises a photoplethysmography sensor.

12. The system of claim 9, wherein the emitter comprises at least one light emitting diode.

13. The system of claim 9, wherein the detector comprises a photoelectric detector.

14. The system of claim 9 further comprising an analog-to-digital converter, wherein the processing equipment is configured to determine whether a portion of the light signal comprises substantially constant amplitude by determining whether the analog-to-digital converter receives a maximum input that it can process.

15. The system of claim 9, wherein the processing equipment is further configured to determine a probe-off condition based on the determination that the physiological sensor is not properly positioned.

16. The system of claim 9, wherein the processing equipment is further configured to provide an alarm in response to the determination that the physiological sensor is not properly positioned.