Currently available oximetry technologies are designed to function on relatively easy to use sites which exhibit strong pulsatile signals, such as the fingers, head and ears. Other tissue sites, such as the chest, may provide an advantage but skin characteristics and signal artifacts impair the accuracy of oximetry measurement.
An example of the present subject matter includes a wearable oximeter for use on the chest. Among other things, movement of the chest due to breathing presents a particularly difficult signal environment for oximetry. Current approaches developed for legacy sites are inadequate to deal with the problems caused by respiratory motion.
A device can be configured to measure one or more physiological parameters of a patient. A patient can wear the device, for example, on a digit (such as a finger or a toe), a limb (such as a calf or forearm), or the torso (such as the chest). In an example, a device may also be coupled to the patient at a tissue site, such as at the chest (e.g., on the pectoral muscle), the back, an arm, a leg, the head (e.g., on the frontal cortex), or the torso, for example. In an example, the device can be bonded to the tissue site by an adhesive. The adhesive can include a resilient pad in which one side of the pad can be adhered to the skin of the patient and the device can be adhered to another side of the adhesive pad. In one example, the device can be coupled to a location on the patient using the adhesive pad. The adhesive pad can be shaped or sized to fit a particular tissue site.
Motion can be associated with the tissue site, and thus a device affixed to the site. In an example, patient respiration (breathing) can be a source of motion. Motion can also be attributed to physical activity, turbulence from a moving vehicle, or if the patient changes posture, such as sitting down or standing up. In an example, motion of the tissue site can be caused by an external source, such as clothing in contact with the device and relative motion between the device and the patient's skin. Another example of a source of motion of the tissue site can be attributed to device inertia relative to cessation of patient movement. There can be other sources of motion. The adhesive pad can be configured to adhere to the skin of the patient at a particular tissue site during such motion.
The present subject matter includes systems, devices, and methods as described herein. For example, the present subject matter can include structure to stabilize a bond between the device and patient tissue. In one example, the present subject matter provides a consistent interface for the coupling between the device and the skin. This improved consistency can improve accuracy and repeatability of the measurements provided by the device.
In one example, the device can include a first sensor having an optical emitter and a detector. The emitter can be configured to transmit selected wavelengths of light directed at a tissue site and the detector can receive the resulting light as it emerges from the tissue site or light reflected from the tissue site. A signal from the detector can be analyzed to determine a measure of oxygenation based on light attenuation. One example of a device can be used for non-invasive measurement of arterial oxygenation saturation. The device can include a processor configured to operate at least one sensor. The device can include a first sensor configured to measure oxygenation and include a second sensor. The first sensor and the second sensor can provide respective output signals to the processor. In one example, the second sensor is configured to measure a parameter corresponding to motion of the device (or motion of the tissue site). In one example, the second sensor includes a force sensor. A force sensor can be configured to measure a force between the device and the skin of the patient.
In an example, the present subject matter can be configured to compensate for motion associated with the tissue site or compensate for various skin types. Skin type information can be used to improve the accuracy of the measurement. The output from the device can include a physiological waveform.
In one example, an optical sensor uses light passing through a tissue bed in an adhesive patch to determine a measurement of respiration rate.
In one example, a secondary sensor (such as a pressure sensor, an optical energy sensor, or a physical strain sensor) is coupled to the tissue using an adhesive patch and the secondary sensor provides a respiration rate measurement.
In one example, a motion artifact is cancelled or mitigated using a signal from a secondary sensor coupled to tissue using an adhesive patch. The motion artifact can be associated with respiration or physical motion (voluntary or involuntary).
In one example, a motion artifact is cancelled or mitigated by a mechanical apparatus that maintains a relatively constant force between the tissue and the sensor. The mechanical apparatus can be viewed as a constant force unit (CFU) and can be secured to the tissue with an adhesive patch.
This Overview is an overview of some of the teachings of the present application and not intended to be an exclusive or exhaustive treatment of the present subject matter. Further details about the present subject matter are found in the detailed description and appended claims. Other aspects of the invention will be apparent to persons skilled in the art upon reading and understanding the following detailed description and viewing the drawings that form a part thereof, each of which are not to be taken in a limiting sense. The scope of the present invention is defined by the appended claims and their legal equivalents.
Various embodiments are illustrated by way of example in the figures of the accompanying drawings. Such embodiments are demonstrative and not intended to be exhaustive or exclusive embodiments of the present subject matter.
The amount of physical force (or pressure) applied at a sensor-to-skin interface of a measurement device will affect the ability of the device to accurately measure SpO2, heart rate and respiration rate. Variations in the applied pressure due to varying skin characteristics, breathing, and motion can cause undesirable variations in these readings.
An example of the present subject matter includes a method to improve the stability and consistency of the skin-sensor interface and can improve the repeatability, consistency and overall accuracy of the system. In addition, patient comfort can be improved by reducing the surface area of the adhesive patch by which the device is affixed to a tissue site. Various approaches are described herein.
First sensor 110A is affixed within housing 95 such that the contact surface 70 is aligned with a detector element of first sensor 110A. First sensor 110A can include one or more optical emitters and one or more optical detectors. First sensor 110A can provide an output signal corresponding to arterial oxygenation (pulse oximetry) or venous oxygenation (tissue oximetry or regional oximetry), or a measure of other optical-based parameter.
Second sensor 110B is affixed within housing 95 such that it provides a measure of a force, pressure, or acceleration as to device 100A. In the example shown, second sensor 110B is coupled to housing 95 by elastic element 80A, here illustrated as a helical spring.
First sensor 101A, in the example illustrated, includes a pulse oximetry sensor. Adjuster 60 includes a knob on a threaded shaft and allows tuning of the bias force exerted on second sensor 101B.
In the example illustrated, male and female components are configured to cooperatively couple and a spring is utilized to preload a force onto the skin. A force sensor is carried within the housing and low friction sliding elements allow relative movement within the housing.
The dual flexure elements in this example allow the sensor to float perpendicular to the tissue surface, and thus equalize the force (pressure) of the sensor upon the skin. This configuration can reduce or eliminate the effects of friction in the mechanism. This example also includes a force sensor configured to provide periodic or constant data acquisition of the force (pressure) applied.
In this example, a respiration artifact can be mitigated or removed from the SpO2 waveform, using sensor affixed using a suspension apparatus. The optical elements may be independent of, or integrated into, the suspension apparatus. The suspension apparatus provides a signal corresponding to lateral displacement across the patch surface. The example illustrated is configured to provide a waveform to allow extraction of a SpO2 measurement without the respiratory artifact, or to provide a respiration waveform alone, or in conjunction with a sensor to measure another physiological metric. In addition, the configuration illustrated allows for measuring respiration through the optics disposed on the device.
The examples illustrated can be combined in various arrangements to provide an assortment of configurations.
The above detailed description includes references to the accompanying drawings, which form a part of the detailed description. The drawings show, by way of illustration, specific embodiments in which the invention can be practiced. These embodiments are also referred to herein as “examples.” Such examples can include elements in addition to those shown or described.
However, the present inventors also contemplate examples in which only those elements shown or described are provided.
Each of these non-limiting examples can stand on its own, or can be combined in various permutations or combination with one or more of the other examples.
Moreover, the present inventors also contemplate examples using any combination or permutation of those elements shown or described (or one or more aspects thereof), either with respect to a particular example (or one or more aspects thereof), or with respect to other examples (or one or more aspects thereof) shown or described herein.
All publications, patents, and patent documents referred to in this document are incorporated by reference herein in their entirety, as though individually incorporated by reference. In the event of inconsistent usages between this document and those documents so incorporated by reference, the usage in the incorporated reference(s) should be considered supplementary to that of this document; for irreconcilable inconsistencies, the usage in this document controls.
In this document, the terms “a” or “an” are used, as is common in patent documents, to include one or more than one, independent of any other instances or usages of “at least one” or “one or more.” In this document, the term “or” is used to refer to a nonexclusive or, such that “A or B” includes “A but not B,” “B but not A,” and “A and B,” unless otherwise indicated. In this document, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Also, in the following claims, the terms “including” and “comprising” are open-ended, that is, an apparatus, system, device, article, composition, formulation, or process that includes elements in addition to those listed after such a term in a claim are still deemed to fall within the scope of that claim. Moreover, in the following claims, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements on their objects.
Method examples described herein can be machine or computer-implemented at least in part. Some examples can include a computer-readable medium or machine-readable medium encoded with instructions operable to configure an electronic device to perform methods as described in the above examples. An implementation of such methods can include code, such as microcode, assembly language code, a higher-level language code, or the like. Such code can include computer readable instructions for performing various methods. The code may form portions of computer program products. Further, in an example, the code can be tangibly stored on one or more volatile, non-transitory, or non-volatile tangible computer-readable media, such as during execution or at other times. Examples of these tangible computer-readable media can include, but are not limited to, hard disks, removable magnetic disks, removable optical disks (e.g., compact disks and digital video disks), magnetic cassettes, memory cards or sticks, random access memories (RAMs), read only memories (ROMs), and the like.
The above description is intended to be illustrative, and not restrictive. For example, the above-described examples (or one or more aspects thereof) may be used in combination with each other. Other embodiments can be used, such as by one of ordinary skill in the art upon reviewing the above description. The Abstract is provided to allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. Also, in the above Detailed Description, various features may be grouped together to streamline the disclosure. This should not be interpreted as intending that an unclaimed disclosed feature is essential to any claim. Rather, inventive subject matter may lie in less than all features of a particular disclosed embodiment. Thus, the following claims are hereby incorporated into the Detailed Description as examples or embodiments, with each claim standing on its own as a separate embodiment, and it is contemplated that such embodiments can be combined with each other in various combinations or permutations. The scope of the invention should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.
This application claims the benefit of U.S. Provisional Application No. 62/205,211, filed Aug. 14, 2015, which is hereby incorporated by reference herein in its entirety.
Filing Document | Filing Date | Country | Kind |
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PCT/US16/46878 | 8/12/2016 | WO | 00 |
Number | Date | Country | |
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62205211 | Aug 2015 | US |