Controlling optical power in sensors using a Faraday cage

Abstract

The present invention provides a patient monitoring sensor having a communication interface, wherein the patient monitoring sensor can communicate with a monitor through the communication interface. The patient monitoring sensor includes a light emitting diode (LED) communicatively coupled to the communication interface and a detector capable of detecting light communicatively coupled to the communication interface. The patient monitoring sensor also includes a Faraday cage disposed around the detector, wherein the Faraday cage includes an aperture configured to limit the amount of light from the LED that can be detected by the detector.

Description

Technical Field

[0001] The present disclosure relates generally to medical devices and, more particularly, to medical devices that monitor physiological parameters of a patient, such as pulse oximeters. Background Art

[0002] In the medical field, doctors often wish to monitor certain physiological characteristics of their patients. Consequently, a wide variety of devices have been developed to monitor many of these characteristics. These devices provide doctors and other healthcare professionals with the information they need to provide the best possible care for their patients. Consequently, these monitoring devices have become an integral part of modern medicine.

[0003] One technique for monitoring certain physiological characteristics of a patient uses the attenuation of light to determine the patient's physiological characteristics. This is used in pulse oximetry and devices built based on pulse oximetry technology. Light attenuation is also used in local or cerebral oximetry. Oximetry can be used to measure various blood properties, such as the oxygen saturation of hemoglobin in the blood or tissue, the volume of individual blood pulsations supplying the tissue, and / or the rate of blood pulsations corresponding to each heartbeat of the patient. These signals can lead to additional physiological measurements, such as respiratory rate, glucose level, or blood pressure.

[0004] As technology advances and more measurements are obtained from the attenuated optical signal, many caregivers find it convenient to obtain multiple physiological measurement parameters in a single multi-parameter monitoring device. Summary of the Invention

[0005] The technology of this disclosure generally relates to medical devices, such as pulse oximeters, that monitor physiological parameters of a patient.

[0006] In one aspect, the present disclosure provides a patient monitoring sensor having a communication interface through which the patient monitoring sensor can communicate with a monitor. The patient monitoring sensor further includes a light emitting diode (LED) communicatively coupled to the communication interface and a detector capable of detecting light communicatively coupled to the communication interface. The patient monitoring sensor further includes a faraday cage disposed around the detector, wherein the faraday cage includes an aperture configured to limit the amount of light from the LED that can be detected by the detector.

[0007] In another aspect, the present disclosure provides a patient monitoring system having a patient monitor coupled to a patient monitoring sensor. The patient monitoring sensor includes a communication interface through which the patient monitoring sensor can communicate with the patient monitor. The patient monitoring sensor also includes a light emitting diode (LED) communicatively coupled to the communication interface and a detector capable of detecting light communicatively coupled to the communication interface. The patient monitoring sensor also includes a Faraday cage disposed around the detector, wherein the Faraday cage includes an aperture configured to limit the amount of light from the LED that can be detected by the detector.

[0008] The details of one or more aspects of the disclosure are set forth in the accompanying drawings and description below. Other features, objects, and advantages of the techniques described in this disclosure will be apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 shows a perspective view of a patient monitoring system including a patient monitor and patient monitoring sensors according to an embodiment;

[0010] Figure 2 shows a perspective view of a patient monitoring sensor according to an embodiment;

[0011] Figure 3 shows a schematic diagram of a patient monitoring sensor according to an embodiment;

[0012] Figure 4A and 4B shows a schematic diagram of a patient monitoring sensor according to an embodiment; and

[0013] Figure 5A 、 5B 5C show schematic diagrams of patient monitoring sensors according to an embodiment. DETAILED DESCRIPTION

[0014] Advances in light-emitting diode (LED) technology have resulted in LEDs that are significantly brighter than previously available. When these brighter LEDs are used in currently available patient monitoring sensors, the detectors of the patient monitoring sensors may become saturated. Some currently available patient monitoring sensors attempt to address this issue by using electronic circuitry to control the drive current supplied to the LEDs and thereby limit the amount of light emitted by the LEDs. In addition to the complexity of adding drive circuitry to patient monitoring sensors, as LED technology continues to advance, such manipulation of the drive current for controlling the light emitted by the LEDs may be unfeasible.

[0015] The present invention relates to medical sensors and monitors, and more particularly to systems and methods for controlling optical power in patient monitoring sensors using a Faraday cage. In an exemplary embodiment, a patient monitoring sensor is provided in which a detector is disposed within a Faraday cage having an opening configured to limit the amount of light reaching the detector. In addition to limiting the amount of light that can reach the detector, the Faraday cage also provides protection for the detector from electromagnetic interference.

[0016] Now refer to Figure 1 , shows an embodiment of a patient monitoring system 10 that includes a patient monitor 12 and a sensor 14, such as a pulse oximetry sensor, to monitor physiological parameters of the patient. For example, the sensor 14 may be a NELLCOR available from Medtronic (Boulder, CO, USA). TM or INVOS TM Although the depicted embodiments relate to sensors for use on a patient's fingertips, toes, or earlobes, it should be understood that in certain embodiments, features of sensor 14 as provided herein may be incorporated into sensors for use on other tissue locations, such as the forehead and / or temple, heel, abdomen, chest, back, or any other suitable measurement site.

[0017] exist Figure 1 In some embodiments, sensor 14 is a pulse oximetry sensor that includes one or more emitters 16 and one or more detectors 18. For pulse oximetry applications, emitter 16 transmits at least two wavelengths of light (e.g., red light and / or infrared (IR)) into the patient's tissue. For other applications, emitter 16 may transmit 3, 4, or 5 or more wavelengths of light into the patient's tissue. Detector 18 is a photodetector selected to receive light within a range of wavelengths emitted from emitter 16 after the light has passed through the tissue. Additionally, emitter 16 and detector 18 may operate in various modes (e.g., reflection or transmission). In some embodiments, sensor 14 includes sensing components in addition to or in place of emitter 16 and detector 18. For example, in one embodiment, sensor 14 may include one or more actively powered electrodes (e.g., four electrodes) to obtain electroencephalogram (EEG) signals. Sensor 14 also includes a sensor body 46 to house or carry the components of sensor 14. The sensor 14 may be reusable (such as a durable plastic clip sensor), disposable (such as a fabric adhesive sensor), or partially reusable and partially disposable.

[0018] In the illustrated embodiment, the sensor 14 is communicatively coupled to the patient monitor 12. In certain embodiments, the sensor 14 may include a wireless module configured to establish wireless communication 15 with the patient monitor 12 using any suitable wireless standard. For example, the sensor 14 may include a transceiver that enables wireless signals to be sent to and received from an external device (e.g., the patient monitor 12, a charging device, etc.). The transceiver may establish wireless communication 15 with the transceiver of the patient monitor 12 using any suitable protocol. For example, the transceiver may be configured to transmit signals using one or more of the ZigBee standard, the 802.15.4x standard, the WirelessHART standard, the Bluetooth standard, the IEEE 802.11x standard, or the MiWi standard. In addition, the transceiver may transmit raw digitized detector signals, processed digitized detector signals, and / or calculated physiological parameters, as well as any data that may be stored in the sensor, such as data related to the wavelength of the transmitter 16 or data related to the input specifications of the transmitter 16, as described below. Additionally or alternatively, the transmitter 16 and detector 18 of the sensor 14 can be coupled to the patient monitor 12 via a cable 24 through a plug 26 (e.g., a connector having one or more conductors), which is coupled to a sensor port 29 of the monitor. In some embodiments, the sensor 14 is configured to operate in both a wireless mode and a wired mode. Thus, in some embodiments, the cable 24 is removably attached to the sensor 14 so that the sensor 14 can be detached from the cable to increase the patient's range of motion while wearing the sensor 14.

[0019] The patient monitor 12 is configured to calculate physiological parameters of the patient related to the physiological signals received from the sensors 14. For example, the patient monitor 12 may include a processor configured to calculate the patient's arterial oxygen saturation, tissue oxygen saturation, pulse rate, respiratory rate, blood pressure, blood pressure characteristic measurements, autoregulation status, brain activity, and / or any other suitable physiological characteristic. Furthermore, the patient monitor 12 may include a monitor display 30 configured to display information regarding physiological parameters, system information (e.g., instructions for sterilizing and / or charging the sensors 14), and / or alarm indications. The patient monitor 12 may include various input components 32, such as knobs, switches, keys and keypads, buttons, etc., to facilitate operation and configuration of the patient monitor 12. The patient monitor 12 may also display information related to alarms, monitor settings, and / or signal quality via one or more indicator lights and / or one or more speakers or audible indicators. The patient monitor 12 may also include an upgrade slot 28 into which additional modules may be inserted, enabling the patient monitor 12 to measure and display additional physiological parameters.

[0020] Because the sensor 14 can be configured to operate in a wireless mode, and in some embodiments, may not receive power from the patient monitor 12 when operating in a wireless mode, the sensor 14 can include a battery to provide power to the components of the sensor 14 (e.g., the transmitter 16 and the detector 18). In some embodiments, the battery can be a rechargeable battery, such as, for example, a lithium-ion battery, a lithium-polymer battery, a nickel-metal hydride battery, or a nickel-cadmium battery. However, any suitable power source can be utilized, such as one or more capacitors and / or an energy harvesting power source (e.g., a motion-generated energy harvesting device, a thermoelectrically generated energy harvesting device, or the like).

[0021] As described above, in an embodiment, the patient monitor 12 is a pulse oximetry monitor and the sensor 14 is a pulse oximetry sensor. The sensor 14 can be placed at a location on the patient with a pulsating arterial flow, typically a fingertip, toe, forehead, or earlobe, or in the case of a newborn, across the foot. Other suitable sensor locations include, but are not limited to, the neck for monitoring carotid pulsating flow, the wrist for monitoring radial pulsating flow, the inner thigh of the patient for monitoring femoral pulsating flow, the ankle for monitoring tibial pulsating flow, and around or in front of the ear. The patient monitoring system 10 can include sensors 14 located in multiple locations. The emitter 16 emits light that passes through blood-perfused tissue, and the detector 18 photoelectrically senses the amount of light reflected or transmitted by the tissue. The patient monitoring system 10 measures the intensity of the light received at the detector 18 as a function of time.

[0022] A signal representing light intensity relative to time, or a mathematical processing of that signal (e.g., a scaled version thereof, an acquired log thereof, a scaled version of an acquired log thereof, etc.), may be referred to as a photoplethysmography (PPG) signal. Furthermore, the term "PPG signal," as used herein, may also refer to an absorption signal (i.e., representing the amount of light absorbed by tissue) or any suitable mathematical processing thereof. The amount of detected or absorbed light may then be used to calculate any of a number of physiological parameters, including oxygen saturation (the amount of oxygen in pulsating blood, SpO2), the amount of blood constituents (e.g., oxyhemoglobin), and physiological rates (e.g., pulse rate or respiratory rate) and the time at which each individual pulse or breath occurred. For SpO2, red and infrared (IR) wavelengths may be used, as it has been observed that highly oxygenated blood will absorb relatively less red light and more IR light than blood with a lower oxygen saturation. By comparing the intensities of the two wavelengths at different points in the pulse cycle, the oxygen saturation of hemoglobin in arterial blood can be estimated, such as from empirical data that can be indexed by the value of the ratio, a lookup table, and / or from curve fitting and / or other interpolation techniques.

[0023] Now refer to Figure 2 , shows an embodiment of a patient monitoring sensor 100 according to an embodiment. The sensor 100 includes a body 102 that includes a flexible circuit. The sensor 100 includes an LED 104 and a detector 106 disposed on the body 102 of the sensor 100. The body 100 includes a flap portion 116 that includes an aperture 108. The flap portion 116 is configured to fold at a hinge portion 114 so that the aperture 108 overlaps with the detector 106. In one embodiment, the flap portion 116 includes an adhesive 110 that is used to secure the flap portion 116 to the body 102 after the flap portion 116 is folded at the hinge portion 114.

[0024] The sensor 100 includes a plug 120 configured to connect to a patient monitoring system, such as Figure 1 The sensor 100 also includes a cable 122 that connects the plug 120 to the body 102 of the sensor 100. The cable 122 includes a plurality of wires 124 that connect various portions of the plug 120 to terminals 126 provided on the body 102. A flexible circuit is provided in the body 102 and connects the terminals 126 to the LED 104 and the detector 108. In addition, one of the terminals 126 connects a ground line to the flexible circuit.

[0025] In an exemplary embodiment, the aperture 108 is configured to limit the amount of light received by the detector 106. In an exemplary embodiment, the configuration of the aperture 108, i.e., the number, shape, and size of the openings defining the aperture 108, can vary. As shown, in one embodiment, the aperture 108 comprises a single circular opening. In other embodiments, the aperture 108 may comprise one or more openings having various shapes and sizes. The configuration of the aperture 108 is selected to control the amount of light received by the detector 106. In one embodiment, the aperture 108 is configured such that approximately eighty percent (80%) of the sensor portion of the detector 106 is unobstructed and able to receive light from the LED 104. In another embodiment, the aperture 108 is configured such that approximately sixty percent (60%) of the sensor portion of the detector 106 is unobstructed and able to receive light from the LED 104. In one embodiment, the aperture 108 comprises a single circular opening having a diameter of .062 inches, or approximately 1.6 mm. In another embodiment, the aperture 108 comprises a plurality of openings having a diameter of approximately 2 mm. 2 In one embodiment, the active area of ​​the photodetector is approximately 1.6 mm x 1.6 mm, or 2.66 mm 2 .

[0026] In an exemplary embodiment, the body 102 includes a visual indicator 112 for ensuring proper alignment of the flap portion 116 when folded at the hinge portion 114. In one embodiment, the visual indicator 112 includes two adjacent portions positioned such that when the end of the flap portion is placed between the two adjacent portions, the aperture 108 is properly aligned over the detector 106. In another embodiment, the visual indicator 112 includes a single line positioned such that when the end of the flap portion is placed on top of the line, the aperture 108 is properly aligned over the detector 106.

[0027] Now refer to Figure 3 , shows an embodiment of a patient monitoring sensor 200 according to an embodiment. The sensor 200 includes a flap portion 216 that is configured to fold around a hinge portion 214 so that the aperture 208 overlaps with a detector (not shown). The sensor 200 includes a flexible circuit that includes a first conductive material 230 and a second conductive material 240. The first conductive material 230 and the second conductive material 240 are both ground plane layers, but are disposed on separate physical layers and are electrically connected via four vertical vias. The first conductive material 230 is configured to electrically connect the terminal 226 to the contacts 204, 206 for the LED and the detector. When the flap portion 216 of the sensor 202 is folded around the hinge portion 214, the second conductive material 240 at least partially serves to form a Faraday cage around the detector. In one embodiment, the second conductive material 240 is composed of copper. In the exemplary embodiment, the hinge portion 214 includes a notch 238 that is configured to aid in alignment of the tab portion 216 by providing a weak point for bending to occur.

[0028] In an exemplary embodiment, hinge portion 214 includes a limited amount of second conductive material 240 to facilitate folding of flap portion 216 while maintaining electrical connection between the second conductive material 240 disposed in flap portion 216 and the remaining second conductive material 240 in sensor 200. Sensor 200 also includes hinge portion 232, which also includes a limited amount of first conductive material 230 to facilitate folding flap portion 234 onto center portion 236. In an exemplary embodiment, folding flap portion 234 over top of center portion 236 shields the detector signal because flap portion 234 is a solid ground plane copper. In addition, folding flap portion 234 narrows sensor 200, which allows it to fit on the fingers of neonatal patients and adults.

[0029] refer to Figure 4A and 4B, shows a patient monitoring sensor 300 according to an embodiment. In the exemplary embodiment, a faraday cage 340 is formed around a detector 306 by folding a flap portion 316 over a portion of the body 302 of the sensor 300. As shown, the sensor 300 includes a visual indicator 312 that serves as an alignment guide to ensure that the aperture 308 is properly aligned with the detector 306 when the flap portion 316 is in the folded position.

[0030] refer to Figure 5A 、 5B 5C illustrate a patient monitoring sensor 400 according to an embodiment. As shown, the flap portion 416 of the sensor 400 includes a tapered end 420 configured to be inserted into a slot 422 when the flap portion 416 is folded about the hinge portion 414 (i.e., in the folded position). In an exemplary embodiment, fully inserting the tapered end 420 into the slot 422 ensures proper alignment between the aperture 408 and the detector 406. In an exemplary embodiment, the aperture 408 includes a plurality of openings in a pattern. In embodiments having a plurality of openings in a pattern, greater variation in the alignment of the aperture 408 and the detector 406 is permitted. As described above, the configuration of the aperture 408, i.e., the number, shape, position, and size of the openings defining the aperture 408, can vary and be selected to control the amount of light received by the detector 406. In one embodiment, to reduce the effects of misalignment, the pattern of openings defining the aperture 408 extends beyond the dimensions of the detector 408. Thus, in situations where misalignment occurs, the approximate light attenuation remains consistent.

[0031] In one embodiment, Figure 5C As best shown in FIG, the patient monitoring sensor 400 includes a locking member 424 disposed on the end of the tapered portion 420. The locking member 424 is configured to prevent the tapered portion 420 from being displaced once the tapered portion is inserted into the slot 422. In one embodiment, the locking member 424 is configured to be temporarily deformable so that it can be inserted into the slot 422. Once the locking member 424 is fully inserted into the slot, the locking member will return to its original shape and prevent the tapered portion 420 from being removed from the slot 422. In another embodiment, the locking member 424 is rotatably attached to the tapered portion 420 and is rotated to facilitate insertion into the slot 422 and again prevent the tapered portion 420 from being removed from the slot 422.

[0032] One or more specific embodiments of the present technology are described below. To provide a concise description of these embodiments, not all features of an actual implementation are described in this specification. It should be understood that in the development of any such actual implementation, many implementation-specific decisions must be made, and these decisions may vary from one implementation to another. In one embodiment, a medical monitoring system includes a sensor that is actively powered during use.

[0033] It should be understood that the various aspects disclosed herein can be combined in combinations different from those specifically presented in the specification and drawings. It should also be understood that, depending on the examples, certain actions or events in any of the processes or methods described herein may be performed in a different order, may be added, combined, or omitted entirely (e.g., all described actions or events may not be necessary to perform the technology). In addition, although certain aspects of the present disclosure are described as being performed by a single module or unit for purposes of clarity, it should be understood that the technology of the present disclosure may be performed by a combination of units or modules associated with, for example, a medical device.

[0034] In one or more examples, the described techniques can be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions can be stored as one or more instructions or codes on a computer-readable medium and executed by a hardware-based processing unit. Computer-readable media can include non-transitory computer-readable media, which corresponds to tangible media such as data storage media (e.g., RAM, ROM, EEPROM, flash memory, or any other medium that can be used to store desired program code in the form of instructions or data structures and can be accessed by a computer).

[0035] Instructions may be executed by one or more processors, such as one or more digital signal processors (DSPs), general-purpose microprocessors, application-specific integrated circuits (ASICs), field-programmable logic arrays (FPGAs), or other equivalent integrated or discrete logic circuits. Thus, the term "processor," as used herein, may refer to any of the foregoing structures or any other physical structure suitable for implementing the described techniques. Additionally, these techniques may be fully implemented in one or more circuits or logic elements.

Claims

1. A patient monitoring sensor comprising: a communication interface through which the patient monitoring sensor can communicate with a monitor; a light emitting diode (LED) communicatively coupled to the communication interface; a detector communicatively coupled to the communication interface and capable of detecting light; a body having a flexible circuit coupling the LED and the detector to the communication interface; as well as a faraday cage comprising a flap portion of the body extending from a portion of the body housing the detector, wherein the flap portion is configured to fold over the detector, wherein the flap portion defines an aperture configured to limit an amount of light from the LED that the detector is able to detect, and The body further comprises a slot into which the tapered end of the fin portion is inserted when the fin portion is folded over the detector.

2. The patient monitoring sensor of claim 1, wherein the aperture comprises a plurality of openings. 3 . The patient monitoring sensor of claim 1 , further comprising a locking member disposed on the tapered end portion and configured to prevent displacement of the tapered end portion once the tapered end portion is inserted into the slot.

4. The patient monitoring sensor of claim 1, wherein the tab portion of the body is coupled to the portion of the body housing the detector by a hinge.

5. The patient monitoring sensor of claim 4, wherein the hinge comprises a conductive material to electrically connect to the tab portion of the body.

6. A patient monitoring system comprising: a patient monitor coupled to a patient monitoring sensor, the patient monitoring sensor comprising: a communication interface through which the patient monitoring sensor is capable of communicating with the patient monitor; a light emitting diode (LED) communicatively coupled to the communication interface; a detector communicatively coupled to the communication interface and capable of detecting light; a body having a flexible circuit coupling the LED and the detector to the communication interface; as well as A faraday cage comprising a flap portion of the body, the flap portion extending from a portion of the body housing the detector, wherein the flap portion is configured to be folded over the detector, wherein the flap portion defines an aperture configured to limit an amount of light from the LED that the detector can detect, and wherein the body further comprises a slot into which a tapered end of the flap portion is inserted when the flap portion is folded over the detector. The patient monitoring system of claim 6 , wherein the aperture comprises a plurality of openings.

8. The patient monitoring system of claim 6, further comprising a locking member disposed on the tapered end portion and configured to prevent displacement of the tapered end portion once the tapered end portion is inserted into the slot.

9. The patient monitoring system of claim 6, wherein the flap portion of the body is coupled to the portion of the body housing the detector by a hinge.

10. The patient monitoring system of claim 9, wherein the hinge comprises a conductive material to electrically connect to the tab portion of the body.

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