Patent Application
20210386337
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.
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.
One issue in such sensors relates to light emitting diodes typically used in such applications, including added bulk to the sensor, complexity, and emission of heat. Further, such sensors, based on a standard localized LED source (e.g., dual wavelength RED/IR LEDs) and detector are very sensitive to position and measure only local tissue saturation.
There is a need in the art for robust medical sensors that overcomes limitations of traditional sensors.
The techniques of this disclosure generally relate to medical devices that monitor physiological parameters of a patient, such as pulse oximeters.
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 also includes a waveguide-based light emitter communicatively coupled to the communication interface and a detector, communicatively coupled to the communication interface, capable of detecting light. In exemplary embodiments, the waveguide-based light emitter includes a light source coupled to a waveguide. In further exemplary embodiments, the detector includes a signal pickup waveguide. In further exemplary embodiments, the waveguides and optical components are built over a soft pad.
In another aspect, the 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 waveguide-based light emitter communicatively coupled to the communication interface and a detector, communicatively coupled to the communication interface, capable of detecting light. In exemplary embodiments, the waveguide-based light emitter includes a light source coupled to a waveguide. In further exemplary embodiments, the detector includes a signal pickup waveguide. In further exemplary embodiments, the waveguides and optical components are built over a soft pad.
The details of one or more aspects of the disclosure are set forth in the accompanying drawings and the 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.
Traditional pulse oximeter sensor designs utilize light emitting diodes, which as typically used in such applications, includes added bulk to the sensor, complexity, and emission of heat. Further, such sensors, based on a standard localized light emitting diode (LED) source (e.g., dual wavelength RED/IR LEDs) and detector are very sensitive to position and measure only local tissue saturation.
Accordingly, the present disclosure describes a patient monitoring sensor that includes a waveguide-based light emitter communicatively coupled to the communication interface and a detector, communicatively coupled to the communication interface, capable of detecting light. In exemplary embodiments, the waveguide-based light emitter includes a light source coupled to a waveguide. In further exemplary embodiments, the detector includes a signal pickup waveguide.
In further exemplary aspects, exemplary waveguides for the source and the detector include soft waveguides configured to utilize a total internal reflection effect, where the light (e.g., IR/RED) entering the tissue is distributed over a bigger surface and penetrate the tissue only in places of contact between the waveguide material and the skin at overcritical angles, otherwise reflecting inside. In such a way, the source distributes the light injection and pickup all over the surface of the skin (e.g., on the finger) in order to sample a bigger volume inside the tissue (a volumetric measurement) for a more stable measurement, as compared with local tissue saturation measurements as in traditional pulse oximeters.
Additionally, in exemplary embodiments, the signal pickup waveguide comprises a waveguide with a matching or similar refractive index. Exemplary embodiments for waveguide material include Infrared (IR) transparent silicone, etc. Exemplary embodiments thus provide waveguides that can pick up, deliver and integrate the signal from all directions.
In further exemplary embodiments a light source includes an LED with a narrow opening angle. In exemplary embodiments, the opening angle is between about 10 and 15 degrees, though other opening angles are contemplated. In further exemplary embodiments, the opening angle is between about 5 and 20 degrees.
In further exemplary embodiments, the LED comprises a polarized or highly polarized LED; and the detector includes a polarization film (filter) over the detector. In exemplary embodiments, the shunted signal is filtered (the signal coming from the deep tissue will be non-polarized). In such exemplary embodiments, the shunted, non-scattered signal will remain, with a relatively high degree of polarization and will be filtered out.
In further exemplary embodiments, a suitable LED includes a vertical-cavity surface-emitting laser (VSCEL) diode, which can have both a narrow opening angle and high polarization.
In further exemplary embodiments, the waveguides and optical components are built over a soft pad.
Referring now to
In the embodiment of
Referring again to
The sensor 14 also includes a sensor body 46 to house or carry the components of the sensor 14. The body 46 includes a backing, or liner, bandage or pad, provided around the emitter 16 and the detector 18, as well as an adhesive layer (not shown in
In the embodiment shown, 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 a 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 transmitted 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 a 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, 802.15.4x standards WirelessHART standard, Bluetooth standard, IEEE 802.11x 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 16, or data relating to input specification for the emitters 16, as discussed below. Additionally, or alternatively, the emitters 16 and detectors 18 of the sensor 14 may be coupled to the patient monitor 12 via a cable 24 through a plug 26 (e.g., a connector having one or more conductors) coupled to a sensor port 29 of the monitor. In certain embodiments, the sensor 14 is configured to operate in both a wireless mode and a wired mode. Accordingly, in certain embodiments, the cable 24 is removably attached to the sensor 14 such that the sensor 14 can be detached from the cable to increase the patient's range of motion while wearing the sensor 14.
The patient monitor 12 is configured to calculate physiological parameters of the patient relating to the physiological signal received from the sensor 14. For example, the patient monitor 12 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 12 may include a monitor display 30 configured to display information regarding the physiological parameters, information about the system (e.g., instructions for disinfecting and/or charging the sensor 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 provide for 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, in which additional modules can be inserted so that the patient monitor 12 can measure and display additional physiological parameters.
Because the sensor 14 may be configured to operate in a wireless mode and, in certain embodiments, may not receive power from the patient monitor 12 while operating in the wireless mode, the sensor 14 may include a battery to provide power to the components of the sensor 14 (e.g., the emitter 16 and the detector 18). In certain embodiments, the battery may be a rechargeable battery such as, for example, a lithium ion, lithium polymer, nickel-metal 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 12 is a pulse oximetry monitor and the sensor 14 is a pulse oximetry sensor. The sensor 14 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 10 may include sensors 14 at multiple locations. The emitter 16 emits light which passes through the 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 light that is received at the detector 18 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.
One or more specific embodiments of the present techniques will be described below. In an effort to provide a concise description of these embodiments, not all features of an actual implementation are described in the specification. 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.
It should be understood that various aspects disclosed herein may be combined in different combinations than the combinations specifically presented in the description and accompanying drawings. It should also be understood that, depending on the example, certain acts or events of any of the processes or methods described herein may be performed in a different sequence, may be added, merged, or left out altogether (e.g., all described acts or events may not be necessary to carry out the techniques). In addition, while certain aspects of this disclosure are described as being performed by a single module or unit for purposes of clarity, it should be understood that the techniques of this disclosure may be performed by a combination of units or modules associated with, for example, a medical device.
