Patent Description:
In the field of medicine, doctors often desire to monitor certain physiological characteristics of their patients. Accordingly, a wide variety of devices have been developed for monitoring many such physiological characteristics. Such devices provide doctors and other healthcare personnel with the information they need to provide the best possible healthcare for their patients. As a result, such monitoring devices have become an indispensable part of modern medicine.

One technique for monitoring certain physiological characteristics of a patient uses attenuation of light to determine physiological characteristics of a patient. This is used in pulse oximetry, and the devices built based upon pulse oximetry techniques. Light attenuation is also used for regional or cerebral oximetry. Oximetry may be used to measure various blood characteristics, such as the oxygen saturation of hemoglobin in blood or tissue, the volume of individual blood pulsations supplying the tissue, and/or the rate of blood pulsations corresponding to each heartbeat of a patient. The signals can lead to further physiological measurements, such as respiration rate, glucose levels or blood pressure.

As technologies advance and more measurements become available from the attenuated light signals, many caregivers find it convenient to have multiple physiological measurement parameters available in a single, multi-parameter monitoring device. <CIT> describes a remanufactured bandage-type medical sensor. <CIT> describes a flex circuit optical sensor. <CIT> describes a conformable sensor. <CIT> describes measuring and determining physiological parameters of a patient. <CIT> describes a spectrophotometric sensor.

The techniques of this disclosure generally relate to medical devices that monitor physiological parameters of a patient, such as pulse oximeters.

<NUM> According to one aspect of the present invention there is provided 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, capable of detecting light; a body having a flexible circuit that couples the LED and the detector to the communication interface; and a faraday cage provided as a flap portion of the body extending from a portion of the body housing the detector, wherein said flap portion is folded over the detector, wherein the faraday cage includes an aperture configured to limit an amount of light from the LED that the detector is able to 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.

According to another aspect of the present invention there is provided 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 can communicate with the patient monitor; a light-emitting diode (LED) communicatively coupled to the communication interface; a detector, communicatively coupled to the communication interface, capable of detecting light; a body having a flexible circuit that couples the LED and the detector to the communication interface; and a faraday cage provided as a flap portion of the body extending from a portion of the body housing the detector, wherein said flap portion is folded over the detector, wherein the faraday cage includes an aperture configured to limit an amount of light from the LED that the detector is able to 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.

Advances in light-emitting diode (LED) technology have led to LEDs that are much brighter than previously available LEDs. When these brighter LEDs are used in currently available patient monitoring sensors, the detectors of the patient monitoring sensors can become saturated. Some currently available patient monitoring sensors attempt to address this problem by using electronic circuits to control a drive current supplied to the LED and to thereby limit the amount of light emitted by the LED. In addition to the complexity of adding a drive circuit to the patient monitoring sensors, such drive current manipulation to control the light emitted by the LED may not be feasible as LED technology continues to evolve.

The present invention relates to medical sensors and monitors, in particular to systems and methods for controlling optical power in a patient monitoring sensor with the use of a faraday cage. In exemplary embodiments, a patient monitoring sensor is provided in which a detector is disposed within a faraday cage that has an opening that is configured to limit the amount of light that reaches the detector. In addition to limiting the amount of light that can reach the detector, the faraday cage provides protection against electromagnetic interference for the detector.

Referring now to <FIG>, an embodiment of a patient monitoring system <NUM> that includes a patient monitor <NUM> and a sensor <NUM>, such as a pulse oximetry sensor, to monitor physiological parameters of a patient is shown. By way of example, the sensor <NUM> may be a NELLCOR™, or INVOS™ sensor available from Medtronic (Boulder, CO), or another type of oximetry sensor. Although the depicted embodiments relate to sensors for use on a patient's fingertip, toe, or earlobe, it should be understood that, in certain embodiments, the features of the sensor <NUM> as provided herein may be incorporated into sensors for use on other tissue locations, such as the forehead and/or temple, the heel, stomach, chest, back, or any other appropriate measurement site.

In the embodiment of <FIG>, the sensor <NUM> is a pulse oximetry sensor that includes one or more emitters <NUM> and one or more detectors <NUM>. For pulse oximetry applications, the emitter <NUM> transmits at least two wavelengths of light (e.g., red and/or infrared (IR)) into a tissue of the patient. For other applications, the emitter <NUM> may transmit <NUM>, <NUM>, or <NUM> or more wavelengths of light into the tissue of a patient. The detector <NUM> is a photodetector selected to receive light in the range of wavelengths emitted from the emitter <NUM>, after the light has passed through the tissue. Additionally, the emitter <NUM> and the detector <NUM> may operate in various modes (e.g., reflectance or transmission). In certain embodiments, the sensor <NUM> includes sensing components in addition to, or instead of, the emitter <NUM> and the detector <NUM>. For example, in one embodiment, the sensor <NUM> may include one or more actively powered electrodes (e.g., four electrodes) to obtain an electroencephalography signal. The sensor <NUM> also includes a sensor body <NUM> to house or carry the components of the sensor <NUM>. The sensor <NUM> may be reusable (such as a durable plastic clip sensor), disposable (such as a fabric adhesive sensor), or partially reusable and partially disposable.

In the embodiment shown, the sensor <NUM> is communicatively coupled to the patient monitor <NUM>. In certain embodiments, the sensor <NUM> may include a wireless module configured to establish a wireless communication <NUM> with the patient monitor <NUM> using any suitable wireless standard. For example, the sensor <NUM> may include a transceiver that enables wireless signals to be transmitted to and received from an external device (e.g., the patient monitor <NUM>, a charging device, etc.). The transceiver may establish wireless communication <NUM> with a transceiver of the patient monitor <NUM> using any suitable protocol. For example, the transceiver may be configured to transmit signals using one or more of the ZigBee standard, <NUM>. 4x standards WirelessHART standard, Bluetooth standard, IEEE <NUM>. 11x standards, or MiWi standard. Additionally, the transceiver may transmit a raw digitized detector signal, a processed digitized detector signal, and/or a calculated physiological parameter, as well as any data that may be stored in the sensor, such as data relating to wavelengths of the emitters <NUM>, or data relating to input specification for the emitters <NUM>, as discussed below. Additionally, or alternatively, the emitters <NUM> and detectors <NUM> of the sensor <NUM> may be coupled to the patient monitor <NUM> via a cable <NUM> through a plug <NUM> (e.g., a connector having one or more conductors) coupled to a sensor port <NUM> of the monitor. In certain embodiments, the sensor <NUM> is configured to operate in both a wireless mode and a wired mode. Accordingly, in certain embodiments, the cable <NUM> is removably attached to the sensor <NUM> such that the sensor <NUM> can be detached from the cable to increase the patient's range of motion while wearing the sensor <NUM>.

The patient monitor <NUM> is configured to calculate physiological parameters of the patient relating to the physiological signal received from the sensor <NUM>. For example, the patient monitor <NUM> may include a processor configured to calculate the patient's arterial blood oxygen saturation, tissue oxygen saturation, pulse rate, respiration rate, blood pressure, blood pressure characteristic measure, autoregulation status, brain activity, and/or any other suitable physiological characteristics. Additionally, the patient monitor <NUM> may include a monitor display <NUM> configured to display information regarding the physiological parameters, information about the system (e.g., instructions for disinfecting and/or charging the sensor <NUM>), and/or alarm indications. The patient monitor <NUM> may include various input components <NUM>, such as knobs, switches, keys and keypads, buttons, etc., to provide for operation and configuration of the patient monitor <NUM>. The patient monitor <NUM> 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 <NUM> may also include an upgrade slot <NUM>, in which additional modules can be inserted so that the patient monitor <NUM> can measure and display additional physiological parameters.

Because the sensor <NUM> may be configured to operate in a wireless mode and, in certain embodiments, may not receive power from the patient monitor <NUM> while operating in the wireless mode, the sensor <NUM> may include a battery to provide power to the components of the sensor <NUM> (e.g., the emitter <NUM> and the detector <NUM>). In certain embodiments, the battery may be a rechargeable battery such as, for example, a lithium ion, lithium polymer, nickelmetal hydride, or nickel-cadmium battery. However, any suitable power source may be utilized, such as, one or more capacitors and/or an energy harvesting power supply (e.g., a motion generated energy harvesting device, thermoelectric generated energy harvesting device, or similar devices).

As noted above, in an embodiment, the patient monitor <NUM> is a pulse oximetry monitor and the sensor <NUM> is a pulse oximetry sensor. The sensor <NUM> may be placed at a site on a patient with pulsatile arterial flow, typically a fingertip, toe, forehead or earlobe, or in the case of a neonate, across a foot. Additional suitable sensor locations include, without limitation, the neck to monitor carotid artery pulsatile flow, the wrist to monitor radial artery pulsatile flow, the inside of a patient's thigh to monitor femoral artery pulsatile flow, the ankle to monitor tibial artery pulsatile flow, and around or in front of the ear. The patient monitoring system <NUM> may include sensors <NUM> at multiple locations. The emitter <NUM> emits light which passes through the blood perfused tissue, and the detector <NUM> photoelectrically senses the amount of light reflected or transmitted by the tissue. The patient monitoring system <NUM> measures the intensity of light that is received at the detector <NUM> as a function of time.

A signal representing light intensity versus time or a mathematical manipulation of this signal (e.g., a scaled version thereof, a log taken thereof, a scaled version of a log taken thereof, etc.) may be referred to as the photoplethysmograph (PPG) signal. In addition, the term "PPG signal," as used herein, may also refer to an absorption signal (i.e., representing the amount of light absorbed by the tissue) or any suitable mathematical manipulation thereof. The amount of light detected or absorbed may then be used to calculate any of a number of physiological parameters, including oxygen saturation (the saturation of oxygen in pulsatile blood, SpO2), an amount of a blood constituent (e.g., oxyhemoglobin), as well as a physiological rate (e.g., pulse rate or respiration rate) and when each individual pulse or breath occurs. For SpO2, red and infrared (IR) wavelengths may be used because 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 two wavelengths at different points in the pulse cycle, it is possible to estimate the blood oxygen saturation of hemoglobin in arterial blood, such as from empirical data that may be indexed by values of a ratio, a lookup table, and/or from curve fitting and/or other interpolative techniques.

Referring now to <FIG>, an embodiment of a patient monitoring sensor <NUM> in accordance with an embodiment is shown. The sensor <NUM> includes a body <NUM> that includes a flexible circuit. The sensor <NUM> includes an LED <NUM> and a detector <NUM> disposed on the body <NUM> of the sensor <NUM>. The body <NUM> includes a flap portion <NUM> that includes an aperture <NUM>. The flap portion <NUM> is configured to be folded at a hinge portion <NUM> such that the aperture <NUM> overlaps the detector <NUM>. In one embodiment, the flap portion <NUM> includes an adhesive <NUM> that is used to secure the flap portion <NUM> to the body <NUM> after the flap portion <NUM> is folded at the hinge portion <NUM>.

The sensor <NUM> includes a plug <NUM> that is configured to be connected to a patient monitoring system, such as the one shown in <FIG>. The sensor <NUM> also includes a cable <NUM> that connects the plug <NUM> to the body <NUM> of the sensor <NUM>. The cable <NUM> includes a plurality of wires <NUM> that connect various parts of the plug <NUM> to terminals <NUM> disposed on the body <NUM>. The flexible circuit is disposed in the body <NUM> and connects the terminals <NUM> to the LED <NUM> and the detector <NUM>. In addition, one of the terminals <NUM> connect a ground wire to the flexible circuit.

In exemplary embodiments, the aperture <NUM> is configured to limit the amount of light that is received by the detector <NUM>. In exemplary embodiments, the configuration of the aperture <NUM>, i.e., a number, shape, and size of the openings that define the aperture <NUM> can vary. As illustrated, in one embodiment, the aperture <NUM> includes a single round opening. In other embodiments, the aperture <NUM> can include one or more openings that have various shapes and sizes. The configuration of the aperture <NUM> is selected to control the amount of light that is received by the detector <NUM>. In one embodiment, the aperture <NUM> is configured such that approximately eighty percent (<NUM>%) of a sensor portion of the detector <NUM> is unobstructed and able to receive light from the LED <NUM>. In another embodiment, the aperture <NUM> is configured such that approximately sixty percent (<NUM>%) of a sensor portion of the detector <NUM> is unobstructed and able to receive light from the LED <NUM>. In one embodiment, the aperture <NUM> includes a single round opening having a diameter of. <NUM> inches or about <NUM>. In another embodiment, the aperture <NUM> includes a plurality of openings that have a combined area of about <NUM><NUM>. In one embodiment, the active area of the photodetector is about <NUM> x <NUM>, or <NUM><NUM>.

In exemplary embodiments, the body <NUM> includes a visual indicator <NUM> that is used to assure proper alignment of the flap portion <NUM> when folded at the hinge portion <NUM>. In one embodiment, the visual indicator <NUM> includes two adjacent portions located such that when the end of the flap portion is placed between the two adjacent portions the aperture <NUM> is properly aligned over the detector <NUM>. In another embodiment, the visual indicator <NUM> includes a single line that is disposed such that when the end of the flap portion is placed on top of the line the aperture <NUM> is properly aligned over the detector <NUM>.

Referring now to <FIG>, an embodiment of a patient monitoring sensor <NUM> in accordance with an embodiment is shown. The sensor <NUM> includes a flap portion <NUM> that is configured to be folded about a hinge portion <NUM> such that the aperture <NUM> overlaps the detector (not shown). The sensor <NUM> includes a flexible circuit that includes a first conductive material <NUM> and a second conductive material <NUM>. The first conductive material <NUM> and a second conductive material <NUM> are both ground plane layers, but are disposed on separate physical layers and they are electrically connected through <NUM> vertical vias. The first conductive material <NUM> is configured to electrically connect the terminals <NUM> to contacts <NUM>, <NUM> used for the LED and the detector. The second conductive material <NUM> is used, at least in part, to create a faraday cage around the detector, when the flap portion <NUM> of the sensor <NUM> is folded about the hinge portion <NUM>. In one embodiment, the second conductive material <NUM> consists of copper. In exemplary embodiments, the hinge portion <NUM> includes a notch <NUM> which is configured to aid in the alignment of the flap portion <NUM> by providing a weak point for the bend to occur.

In exemplary embodiments, the hinge portion <NUM> includes a limited amount of the second conductive material <NUM> to facilitate folding the flap portion <NUM> while maintaining an electrical connection between the second conductive material <NUM> disposed in the flap portion <NUM> with the remaining second conductive material <NUM> in the sensor <NUM>. The sensor <NUM> also includes hinge portions <NUM> which likewise include a limited amount of the first conductive material <NUM> to facilitate folding flap portions <NUM> onto a central portion <NUM>. In exemplary embodiments, folding the flap portion <NUM> over top of the central portion <NUM> shields the detector signal as the flap portion <NUM> is solid ground plane copper. In addition, by folding flap portion <NUM> makes the sensor <NUM> narrower which makes it fit onto neonatal patients and fingers of adults.

Referring now to <FIG> a patient monitoring sensor <NUM> in accordance with an embodiment is shown. In exemplary embodiments, a faraday cage <NUM> is formed around the detector <NUM> by folding the flap portion <NUM> over a portion of the body <NUM> of the sensor <NUM>. As illustrated, the sensor <NUM> includes a visual indicator <NUM> that is used as an alignment guide to ensure that aperture <NUM> is properly aligned with the detector <NUM>, when the flap portion <NUM> is in the folded position.

Referring now to <FIG> a patient monitoring sensor <NUM> in accordance with the invention is shown. As illustrated, the flap portion <NUM> of the sensor <NUM> includes a tapered end <NUM> that is configured to be inserted into a slot <NUM> when the flap portion <NUM> is folded about the hinge portion <NUM>, i.e., in the folded position. In exemplary embodiments, fully inserting the tapered end <NUM> into the slot <NUM> ensures proper alignment between the aperture <NUM> and the detector <NUM>. In exemplary embodiments, the aperture <NUM> includes a plurality of openings in a pattern. In embodiments having multiple openings in a pattern, a larger variance in the alignment of the aperture <NUM> and the detector <NUM> is permitted. As discussed above, the configuration of the aperture <NUM>, i.e., a number, shape, placement and size of the openings that define the aperture <NUM> can vary and are selected to control the amount of light that is received by the detector <NUM>. In one embodiment, to reduce the impact of misalignment, the pattern of openings defining the aperture <NUM> extends beyond the dimensions of the detector <NUM>. Accordingly, in the cases where manufacturing misalignments occur, the approximate light attenuation would stay consistent.

In one embodiment, best shown in <FIG>, the patient monitoring sensor <NUM> includes a locking member <NUM> disposed on the end of the tapered portion <NUM>. The locking member <NUM> is configured to prevent the tapered portion <NUM> from becoming dislodged once the tapered portion is inserted into the slot <NUM>. In one embodiment, the locking member <NUM> is configured to be temporally deformable such that it can be inserted into the slot <NUM>. Once the locking member <NUM> is fully inserted into the slot, the locking member will return to its original shape and prevent the tapered portion <NUM> from being removed from the slot <NUM>. In another embodiment, the locking member <NUM> is rotatably affixed to the tapered portion <NUM> and is rotated to facilitate insertion into the slot <NUM> and again to prevent the tapered portion <NUM> from being removed from the slot <NUM>.

One or more specific embodiments of the present techniques will be described below. It should be appreciated that in the development of any such actual implementation, numerous implementation-specific decisions must be made, which may vary from one implementation to another. In an embodiment, a medical monitoring system includes a sensor that is actively powered during use.

Claim 1:
A patient monitoring sensor (<NUM>), 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 (<NUM>), communicatively coupled to the communication interface, capable of detecting light;
a body having a flexible circuit that couples the LED and the detector (<NUM>) to the communication interface; and
a faraday cage provided as a flap portion (<NUM>) of the body extending from a portion of the body housing the detector (<NUM>), wherein said flap portion (<NUM>) is folded over the detector (<NUM>), wherein the faraday cage includes an aperture (<NUM>) configured to limit an amount of light from the LED that the detector (<NUM>) is able to detect,
and wherein the body further comprises a slot (<NUM>) into which a tapered end (<NUM>) of the flap portion (<NUM>) is inserted when the flap portion (<NUM>) is folded over the detector (<NUM>).