Abstract
A wearable electronic device comprises a base for mounting a plurality of sensors, where the sensors acquiring physiological data of a user wearing the device. By providing multiple sensors on a single device, additional physiological data, such as pulse transit time, can be provided. To ensure quality data is collected, the device includes a spring mechanism for applying a compressive force on the sensor to force it into the skin of a user.
Claims
1. A wearable device comprising: a base comprising a spring mechanism; a pulse oximeter positioned on a bottom surface of the base; a plurality of electrodes positioned on opposite ends of the bottom surface of the base, wherein the plurality of electrodes are capable of acquiring EKG signals; and a printed circuit board attached to the base, wherein the printed circuit board electrically connects the pulse oximeter and the plurality of electrodes.
2. The device of claim 1, wherein the base comprises a depressed center section with cantilevered arms extending from the depressed center section.
3. The device of claim 2, wherein the pulse oximeter is positioned in the depressed center section.
4. The device of claim 1, wherein the base comprises: a central housing; cantilevered arms extending from the central housing, wherein the cantilevered arms are flexible; and wires extending from the printed circuit board to the plurality of electrodes.
5. The device of claim 1, further comprising a plurality of electrode snaps attached to the base, wherein each of the plurality of electrodes connects to the plurality of electrode snaps.
6. The device of claim 1, wherein the base comprises a flexible material.
7. The device of claim 1, wherein the base has a non-planar shape.
8. The device of claim 1, wherein the spring mechanism is selected from the group consisting of: a curved cantilever beam, a helical-type spring, and a straight cantilever beam.
9. The device of claim 1, further comprising an insulating conformal coating affixed to the flexible printed circuit board.
10. The device of claim 1, further comprising: an adhesive disposed on a surface of the plurality of electrodes.
11. The device of claim 1, further comprising: a microprocessor, wherein the microprocessor receives PPG data from the pulse oximeter and EKG data from the plurality of electrodes.
12. The device of claim 11, further comprising: an EKG filter.
13. The device of claim 11, further comprising: an accelerometer.
14. A method of determining pulse transit time from a wearable device comprising: affixing the wearable device to the skin of a user at a position near the heart of the user, wherein the wearable device comprises: a base comprising a spring mechanism, a pulse oximeter positioned on a bottom surface of the base, and a plurality of electrodes positioned on opposite ends of the bottom surface of the base, wherein the plurality of electrodes are capable of acquiring EKG signals; identifying an electrical heartbeat from the EKG signals; identifying a peak in data acquired from the pulse oximeter; and determining a time delay between the electrical heartbeat and the peak as the pulse transit time.
15. The method of claim 14, further comprising: estimating the user's blood pressure from the pulse transit time.
16. A wearable device comprising: a central housing; a plurality of spring mechanisms extending from the central housing; a pulse oximeter positioned on a bottom surface of the central housing; an electrode disposed on a distal end of each spring mechanism of the plurality of spring mechanisms, wherein the electrode is capable of acquiring EKG signals; and a printed circuit board attached to the base, wherein the printed circuit board electrically connects the pulse oximeter and the electrode.
Description
BRIEF SUMMARY OF THE SEVERAL VIEWS OF THE DRAWINGS
[0012] FIGS. 1A and 1B are profile views of the device, according to one embodiment.
[0013] FIG. 2 is the device according to an alternative embodiment.
[0014] FIGS. 3A-3D show the spring mechanism of the device, according to several alternative embodiments.
[0015] FIG. 4 shows various components of the device.
[0016] FIG. 5 shows the device with a protective cover, according to one embodiment.
[0017] FIG. 6 depicts the device placed on the chest of a user.
[0018] FIG. 7 is a graph showing data collected by the device, with pulse transit time identified.
DETAILED DESCRIPTION
[0019] The patch 100, according to one example embodiment, can be seen in FIGS. 1A-1B. In FIG. 1A, the patch 100 is shown prior to attachment to the skin of a user. As shown in FIG. 1A, the patch 100 comprises a base 101 preformed in a curved, or stepped, configuration. More specifically, the profile view of the patch 100 in FIG. 1A shows the base 101 having a flat center portion that rises towards each end, forming a non-planar shape. In the embodiment shown in FIG. 1A, a biopotential electrode 102 is affixed to the bottom of each end and a pulse oximeter 103 is attached to the bottom of the center portion. The biopotential electrodes 102 have an adhesive that is used to attach the patch 100 to the skin of a user.
[0020] FIG. 1B depicts the patch 100 affixed to the skin of a user. As compared to the shape of the patch 100 in FIG. 1A, the shape of the patch 100 in FIG. 1B is flattened, with the electrodes 102 and pulse oximeter 103 all in contact with the skin of the user. To enable deformation from the unattached state, the base 101 comprises a flexible material, such as ABS plastic, creating a cantilever, or spring mechanism 107, between the biopotential electrodes 102 and pulse oximeter 103. Referring again to FIG. 1B, the ends of the base 101, or cantilevered arms 108, are depressed compared to the un-affixed shape of the base 101 depicted in FIG. 1A. In this configuration, the pulse oximeter 103, which is geometrically positioned closer to the body than the electrodes 102, is pressed into the skin of the user as the patch 100 deforms elastically. This elastic deformation creates a compressive force at the pulse oximeter 103. In addition to ABS plastic and other flexible polymers, the base 101 may comprise any material with a moderate Young's modulus and high yield strain. For example, a typical ABS plastic has a Young's Modulus of approximately 1 GPa and a yield strain of around 20%. Materials like these offer a compromise between the necessary stiffness required to exert sufficient force into the skin of a user, while also being bendable and accommodating to the curved surfaces typically seen on the chest and back. A person having skill in the art will appreciate that the shape and form of the base 101 can be manufactured according to various techniques, such as injection molding, 3D printing, milling, or any other general additive/subtractive manufacturing process.
[0021] The mechanical spring mechanism 107 can be employed in a variety of configurations. For example, FIG. 2 shows an alternative embodiment of the patch 100 with three electrodes 102 positioned around the center portion of the patch 100. In this embodiment, each electrode 102 is positioned on the same plane, which is different compared to the plane of the center portion of the patch 100 containing the pulse oximeter 103. While all three electrodes 102 occupy the same plane in this embodiment, a compressive force on the center portion of the patch 100 can be created with less than all electrodes 102 raised above the center portion.
[0022] FIGS. 3A-3D shows various configurations of the spring mechanism 107, which can take the form of a beam, spring, or other elastically deformable solid. For example, the apparatus can use a spring mechanism in the form of a curved cantilever beam (FIG. 3A), a helical-type spring (FIG. 3B), a straight cantilever beam (FIG. 3C), or a configuration (FIG. 3D) where the base 101 comprises a central housing 104 with protruding cantilever arms 108 extending from the central housing, where the arms 108 contain the electrode buckle snaps 106. In the embodiment depicted in FIG. 3D, wires extend from the central housing 104 through the cantilever arms 108, which are hollow, to electrically interface with the electrodes buckle snaps 106. In this embodiment, the majority of deformation occurs at the protruding cantilever arms 108 extending away from the central housing 104. The amount of deformation depends on the type of material used and its thickness or cross-section. In one example embodiment, the cantilever arms 108 are made from ABS plastic and have a thickness between 2-3 mm with a 1 mm hollow cross-section. In this configuration, the patch 100 is flexible enough to be applied to curved surfaces, yet stiff enough to transmit enough force onto the pulse oximeter 103.
[0023] In addition to the base 101, electrodes 102, and pulse oximeter 103, the patch 100 further comprises various electronic components that permits the patch 100 to acquire, store, and transmit physiological data. FIG. 4 shows components contained within the interior of the patch 100 and includes a printed circuit board (PCB) 110 that electrically connects a microprocessor 111, an optional accelerometer 112, and a battery 113. The PCB 110 also connects the electrodes 102 (with or without buckle snaps 106), pulse oximeter 103, or other sensors disposed on the exterior of the patch 100. In one embodiment, the PCB 110 comprises a flexible PCB and is adhered to the base 101. In embodiments where the accelerometer 112 is used, the data acquired by the accelerometer 112 can be used to: (1) detect heart rate through undulations in the z-acceleration component; (2) filter noise due to motion artifacts in other sensor signals, such as the EKG and PPG signals; and (3) classify the current state or activity of the user, such as standing, running, or sleeping. Depending on the state detected, the patch 100 can employ a specific sensor mode.
[0024] The PCB 110 contains many of the components necessary to collect and wirelessly transmit physiological data. For example, the microprocessor 111 may include a Bluetooth radio that can be used to transmit data collected by the patch to an external device, such as a computer, tablet, or phone. In the embodiment shown in FIG. 4, an EKG filter 114 is connected to the microprocessor 111 and is used to filter acquired data prior to transmission. Other electrical components can be included depended on the intended application. To protect the electrical components of the patch 100, an insulating conformal coating 120 can be applied to the patch, as shown in FIG. 5. The coating 120 may comprise flexible materials such as acrylic, urethane, silicone, or similar materials.
[0025] In use, the patch 100 with electrodes 102 is attached to the body of a user. For example, as shown in FIG. 6, the patch 100 is attached to the chest of a user. In FIG. 6, the pulse oximeter 103, which is on the bottom surface of the central housing 104, is pressed into the body as a result of the mechanical spring mechanism 107. When the patch 100 is paired to an external device (ex: smart phone, tablet, etc.) over a radio protocol such as Bluetooth, the physiological data can be transmitted in real-time. FIG. 6 further shows the patch 100 with off-the-shelf electrodes 102, which can easily be attached and detached to the patch 100 through the electrode buckle snaps 106.
[0026] A sample of collected EKG and PPG data can be seen in FIG. 7, and pulse transit time is highlighted. In this case, the raw EKG signal is plotted, along with a high-pass filter of the infrared PPG signal. A clear time-delay between the EKG and PPG peaks is seen, which is PTT, and in this case found to be approximately 147 ms. This value can then be calibrated to a user's blood pressure. For example, a user can perform calibration of the patch 100 using a traditional blood pressure cuff. Other data that can be used for calibration include the user's height, weight, gender, and age, which are characteristics that affect the relationship between PTT and blood pressure. In fact, given a large enough sample size of healthy volunteers who undergo this calibration, it is also possible for a user to obtain their blood pressure without the use of a traditional blood pressure cuff; rather, the user would enter their height, weight, gender, and age, and the calibration would be complete.
[0027] While the disclosure has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modification can be made therein without departing from the spirit and scope of the embodiments. Thus, it is intended that the present disclosure cover the modifications and variations of this disclosure provided they come within the scope of the appended claims and their equivalents.
