Health monitoring system and method

Abstract

Systems, methods, and apparatuses for reducing noise in health monitoring include receiving a health signal and / or a monitoring system, method, and / or apparatus having at least one electrode or sensor for health monitoring.

Description

[0001] This application is a divisional application of patent application No. 201580005960.X (PCT application No. PCT / US2015 / 013113), filed on January 27, 2015, entitled "Health Monitoring System and Method". Technical Field

[0002] Advances in software, electronics, sensor technology, and materials science have revolutionized patient monitoring technology. In particular, numerous devices and systems are now available for a wide range of health monitoring applications. However, improvements to health monitoring devices and systems are still needed to provide one or more of the following: efficient data collection and / or control for parameter determination. Background Technology

[0003] Other alternatives for patients and their physicians can then be developed to include robust and convenient monitors that, in some cases, can collect and transmit long-term data, as well as monitor events in real time, including multivariate parameter determination. Summary of the Invention

[0004] This document describes several alternative monitoring devices, systems, and / or methods for parameter determination, which in some cases can be used for long-term sensing and / or recording of cardiac and / or respiratory data of individuals such as infants, athletes, or heart patients. Various alternative implementations and applications are summarized and / or exemplified throughout the specification below.

[0005] In an alternative aspect, the invention may include embodiments in which a health device is configured to monitor multiple physiological parameters of an individual based on time-consistent measurements collected by one or more sensors, including but not limited to one or more of the following: electrodes for measuring changes in ion potential for electrocardiogram (ECG), a light source and one or more photodetectors (such as LED photodiode arrays) for optically based oxygen saturation measurements, a temperature sensor, an xyz accelerometer for measuring exercise and physical activity, etc. In some embodiments, the methods and devices of the invention may be used to generate respiratory waveforms. Other embodiments may include circuitry that simulates a right leg drive circuit (sometimes referred to herein as a "proxy right leg drive circuit") capable of reducing common-mode noise in a small-footprint device that can be easily attached to an individual or has the capability to be attached to an individual.

[0006] In another alternative aspect of the invention, blood pressure can be determined based on the determination of pulse conduction time. Pulse conduction time is the time it takes for a cardiac pressure wave to travel from the heart to other locations in the body. The measured pulse conduction time can then be used to estimate blood pressure. Heart rate timing from ECG or other signals, as well as photoplethysmography (PPG) signals, can be used to generate the pulse conduction time. It should be noted that such a signal can be generated according to conventional or other future-developed processes and / or devices or systems; alternatively, such a signal can be obtained from one or more wearable monitoring devices, which will also be described below.

[0007] In another alternative aspect, the invention may include one or more methods and / or devices for measuring and / or determining oxygen saturation parameters based on time-consistent pulse oximetry signals and ECG signals. In one embodiment, the ECG signal may be used to define intervals or “frames” of pulse oximetry data, which are collected and averaged to determine constant and major periodic components (e.g., direct current (DC) and alternating current (AC) components) of the pulse oximetry signal, thereby allowing the determination of the oxygen saturation value. Patient-wearable devices in these embodiments, incorporating both a pulse oximetry sensor and an ECG sensor, are particularly suitable for signal acquisition when placed on a patient's chest.

[0008] These and other alternative and / or additional aspects are exemplarily shown in several illustrated alternative and / or additional embodiments and applications, some of which are shown in the accompanying drawings and characterized by the claims that follow. However, as will be understood by those skilled in the art, the foregoing summary and the following detailed description do not describe the full scope of the invention and are not intended to describe every illustrated embodiment or every implementation of the invention, nor are they intended to limit the scope of the claims set forth below. Attached Figure Description

[0009] The attached figures include:

[0010] Including sub Figure 1A-1K Figure 1, defined by these sub-figures, illustrates several alternative embodiments of the invention, including various scale top, bottom, and elevation views of the device and alternative conductive adhesion structures.

[0011] Including sub Figure 2A-2D And Figure 2, defined by these subgraphs, in Figure 2A-2C The diagram provides an alternative to the right leg drive circuit, and in Figure 2D The document provides a circuit diagram for an alternative method to pulse oximetry.

[0012] Figure 3It is a flowchart that includes the alternative methods used.

[0013] Figure 4 Exemplary computer systems or computing resources that can be used in embodiments of the present invention are shown.

[0014] Including sub Figures 5A-5D Furthermore, Figure 5, defined by these sub-figures, provides alternative screenshots of alternative software embodiments according to the present invention.

[0015] Figure 6A and 6B Features of one embodiment for measuring oxygen saturation using pulse oximetry signals and electrocardiogram signals are shown.

[0016] Figure 6C This is a flowchart illustrating the steps of one embodiment for determining an oxygen saturation value.

[0017] Figure 6D and 6E An example for determining respiratory depth values ​​is shown.

[0018] Figure 7A , 7B A flowchart of an alternative method of the present invention is provided in 7C. Detailed Implementation

[0019] While the invention is adaptable to various modifications and alternatives, details therein have been shown by way of example in the accompanying drawings and in the description below. However, it should be understood that this invention is not intended to be limited to the specific embodiments described. The intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention, which are described herein or, even if not explicitly stated, are suffice to be included herein.

[0020] In one aspect, the system of this application may include devices for monitoring physiological parameters such as one or more of the following: electrocardiogram (also known as ECG or EKG), photoplethysmography (also known as PPG), pulse oximetry, temperature, and / or patient acceleration or movement signal.

[0021] Furthermore, the system of this application can be configured to use or include one or more of the following elements to measure and / or process such signals from a patient: (a) a circuit, which is in or on or formed on an elastic or flexible circuit board, the circuit being embedded in a flat elastic substrate or plate having an upper surface and a lower surface, the circuit having one or more of the following: (i) at least one sensor, which is mounted in or on or near the lower surface of the flat elastic substrate, the at least one sensor being electrically or optically connected to a patient; (ii) at least one signal processing module for receiving and / or accepting signals from the at least one sensor, and in some embodiments, converting the signals to store them as patient data; (iii) at least one memory module for receiving and / or accepting and storing patient data; (iv) to The system includes (v) a data communication module for transmitting stored patient data or other data to external devices, and (v) a control module for controlling the timing and operation of at least one sensor, and one or more of the aforementioned signal processing module, at least one memory module, and at least one data communication module, and / or the control module is capable of receiving commands to transmit patient data via at least one data communication module and to erase and / or clear patient data from at least one memory module; and (b) a conductive adhesive removably adhered to the lower surface of a planar elastic substrate, the conductive adhesive being able to adhere to the patient's skin and conduct electrical signals only in a direction substantially perpendicular to the lower surface of the planar elastic substrate, and / or in some embodiments, the conductive adhesive including conductive portions adjacent to one or more sensors and non-conductive portions. In some embodiments, the conductive adhesive is an anisotropic conductive adhesive, including a material region that conducts current only in a direction substantially perpendicular to the skin (i.e., "z-axis" conduction).

[0022] In some embodiments, the device of the present invention will be particularly used for comprehensive long-term cardiac monitoring. Its features may include one or more of a lead-1 ECG, PPG, pulse oximeter, accelerometer, temperature sensor, and / or buttons or other indicators for manually marking patient events. Such a device may be adapted to store, for example, up to two weeks of continuous data (although longer or shorter periods may be stored in alternative embodiments), which in some embodiments may be downloaded to an outpatient computer or other computer via a wired or wireless computer connection (such as via USB in one example) or other acceptable data connection for a short period of approximately 90 seconds (although longer or shorter in alternative embodiments). Accompanying software data analysis packages may be adapted to provide automated event capture and / or allow for immediate or delayed local data parsing.

[0023] Physicians often find it difficult to detect and / or diagnose intermittent cardiac abnormalities because these abnormalities are typically only detected and / or diagnosed during a physical examination of the patient. The device of the present invention addresses this problem, and in some embodiments, can continuously or substantially continuously monitor one or more vital signs.

[0024] Certain alternative features may include one or more of the following: (i) a “right leg” drive circuit with electrodes located only on the chest; (ii) a “z-axis” or anisotropic conductive adhesive electrode interface that allows electrical communication only between the electrode and the patient’s skin directly beneath it; (iii) data being transmitted to and parsed by a local computer accessible to CCU / ICU personnel; and (iv) a unique hardware combination that allows for time-consistent correlation of multiple data resources to aid in diagnosis.

[0025] In some alternative embodiments, the devices and systems of the present invention can provide 1) reusability (in some cases, reusable to approximately or more than 1000 patients), enabling the device cost to be recovered after testing with only about 10 to 15 patients; 2) one or more of ECG waveform data, inertial applied sensing, manual event marking, temperature sensing, and / or pulse oximetry, any one or all of which have temporal consistency for better detection and analysis of arrhythmic events; 3) effective watertightness or waterproofness (enabling the patient / wearer to swim while wearing the device); and 4) a comprehensive analytics package, typically for real-time local data parsing. An alternative device may be adapted to utilize flexible circuitry technology to provide a thin, durable device that flexibly conforms to and moves with the patient's skin during patient / wearer movement.

[0026] Figures 1 and 2 show examples of alternative implementations of the device that can be applied here.

[0027] Figure 1 illustrates a device 100 having a component side or top side 101, a patient side or circuit side 102, one or more internal electrical layers generally identified by reference numeral 103, and an elongated strip layer 105. Electronics may be located above and / or inside the strip layer 105. Figure 1A The above components, as well as other elements that may be used in this application, are shown to a moderate scale in a device that is considered substantially transparent. Figure 1B More specifically regarding the floor plan of the upper 101, and Figure 1C More specifically, a plan view of the lower patient side 102, and Figure 1D More specifically, regarding the side view of the first elevation.

[0028] Many electronic devices in this invention can be disposed in one or more electronic layers 103, and as generally indicated herein, the electronic devices can be encapsulated in a material 104 (such as medical-grade silicone, plastic, or potting material) (see for some examples). Figure 1A , 1B (I, D, and IK) to secure the electronic device in a working position on or within the elongated strip layer 105, or otherwise functionally arrange it relative to the elongated strip layer 105. In many embodiments, potting material or other materials may also or alternatively provide a waterproof, watertight, or water-resistant cover for the electronic device, enabling it to continue operating even in environments with water or sweat. One or more access points, junctions, or other functional units 106 may be located on and / or pass through either side of the encapsulation material 104 for external connection to and / or communication with the electronic device arranged within or beneath the encapsulation material 104. Figure 1A , 1B Figure 1D shows four such access points 106 located on the upper side. These access points may include high-Z data communication ports and / or charging contacts, etc. This upper or component side 101 of the device 100 may be coated with a silicone compound for protection and / or waterproofing. In some examples, only an HS USB connector is exposed via one or more ports 106, for example for data communication or data transfer and / or for charging.

[0029] The elongated strip layer 105 may be or may include circuitry or circuitry portions such as electrical leads or other inner conductors, for example... Figure 1D The diagram shows leads 107 for communication between electronics 103 and conductive pads or contacts 108, 109, and 110, which will be described further below (in some examples, 108 and 109 are for high-impedance / high-Z silver or copper / silver electrodes for electrocardiograms (ECGs), and 110 is sometimes a reference electrode). In many embodiments, the strip layer 105 may be or may include a flexible circuit system, which is understood to provide acceptable deformation, twisting, bending, etc., while still maintaining robust electrical connections within the flexible circuit system. It should be noted that although the electronic device 103 and electrodes 108, 109, 110 are shown attached to layer 105; the electronic device 103 is attached at the top, and electrodes 108, 109, 110 are attached at the bottom or on the patient side; such elements may also be formed in or placed within layer 105, or at least placed relatively indistinguishably in relative working positions in one or more layers that actually have or are adjacent to layer 105 or on layer 105. Similarly, leads or traces 107 are shown embedded (through...) Figure 1D(The dashed lines in the diagram indicate this). However, even though leads and traces are more likely to be located on the upper side to insulate them from electrical communication with other skin sides, they can be located on the upper or lower side. If they start on the upper (lower) side, the traces can then be covered with an insulating sealant or a similar protective covering (not shown separately). In many embodiments, a flexible material is used to cover the traces to flexibly choose whether to maintain the overall or mostly flexible nature of layer 105.

[0030] On the patient side 102, ECG electrodes 108, 109, and 110 may be exposed for substantially direct contact with the patient's skin (although at least a conductive adhesive may be applied between them); and / or in many embodiments, patient-side electrodes 108, 109, and / or 110 may be covered with a conductive adhesive material as described below. The electrodes may be plated with a robust, highly conductive material or may be a robust, highly conductive material (e.g., silver / silver chloride) to achieve biocompatibility and high signal quality, and in some embodiments may be highly robust, suitable for withstanding more than approximately 1000 alcohol wash cycles between multiple patients, for one non-limiting example. The pulse oximeter may be provided with a window or other communication channel or opening 111, 112 ( Figure 1C Examples include LEDs and sensors. These openings 111, 112 can typically be arranged to optimize light communication reaching or from the patient's skin. Figure 1D The non-limiting examples illustrate alternative arrangements of one or more light guides 111a / 112a (and 111b / 112b) arranged closer to and / or connected to the electronics 103. Various alternative arrangements may be used in this application.

[0031] In some implementations, sampling of ambient light (LED off) can be provided, and then the ambient light can be subtracted from each of the pulse ox signals to cancel out noise caused by sunlight or other ambient light sources.

[0032] LED and photodiode sensors can also and / or can alternatively be coated with a silicone layer to eliminate any air gaps between the sensor / LED and the patient's skin. (Separately in...) Figure 1H and 1K Two such examples are given, in which the silicone layer or capping layer 121 is shown as covering / enclosing the light guide and / or sensor / LED 111c / 111d / 112c. LED 111c ( Figure 1H and 1K (in the middle) can be a red LED, LED 111d ( Figure 1H and 1KThe (middle) can be an infrared (IR) LED, and the device 112c ( Figure 1H and 1K The silicone layer (in the middle) can be a sensor. This can reduce light loss reflected from the skin, thereby significantly increasing the signal and reducing noise caused by skin movement relative to the sensor. In some embodiments, the silicone may be referred to as a light guide, and in some cases, it may be a clean, colorless, and / or medical-grade silicone. As further described below, depending on the degree of association between the silicone layer or cover 121 and light emission or transmission when emitting or reflecting reception, the silicone layer or cover 121 may also / alternatively be referred to as a light guide or lens 121 / 121a / 121b in this application.

[0033] In one or more embodiments, the lenses 121 / 121a / 121b herein may be made of medical-grade silicone, which has one or more of the characteristics of being clean, colorless, soft, and having low hardness. Examples of such specialized silicones used in this invention are referred to as “viscous gels” (several suppliers) and typically have an ultra-high viscosity adhesive preferably embedded on both sides. The low-hardness silicone bonded to the viscous gel with the double-sided adhesive can form lenses 121 / 121a / 121b that can be simultaneously adhered to an electronic sensor and the skin, and in some embodiments, exhibit motion artifact reduction properties by restricting movement between the skin-lens-sensor interface. The lenses according to the invention can also / can alternatively be specially shaped such that the lens can be snapped between layers of composite adhesive strips (e.g., see...). Figure 1D , 1G (1I and 1J), and in some embodiments, the size of the opening (typically a rectangular opening) in the adhesive strip, through the raised portion, allows the lens to bulge slightly from the patient side of the adhesive strip (see further below). Figure 1K ).

[0034] exist Figure 1K In this embodiment, an alternative silicone overlay or encapsulant 121a for the LEDs and sensors 111c / 111d / 112c may include a convex lens at or near the overlay on the outer surface 121b. In many embodiments, the outer surface and the lens are the same, and / or the lens may be defined by the surface 121b of the encapsulation material 121a. This provides a structure and method for connecting a pulse oximetry LED emitter 111c / 111d and one or more photodiode sensors 112c to or additionally mounting them on the skin surface of the chest or forehead (e.g., a young child or infant) to a patient or user's body.

[0035] More specifically, as further described in this application, the system and / or device 100 according to the invention can utilize one or more LED emitters 111c / 111d of selected wavelengths and one or more photodiodes. However, to maximize the coupling between the LED / sensor assembly and the skin 1001 of the wearer 1000, a lens 121b made of optically clean, medical-grade silicone can be molded onto the LED / sensor assembly or can be molded such that the lens 121b can then be attached to the LED / sensor assembly 111c / 111d / 112c in a cover-like manner. In many embodiments, the lens 121b can be partially spherical or possibly hemispherical, although the lens does not have to be of this shape. Other shapes of curvature are also available. Curvature reduces loss of skin contact when the device 100 is moved by the wearer's movement or otherwise. That is, movement of the wearer 1000 or movement of the device 100 relative to the wearer 1000 can result in similar rolling contact of the lens on or about the skin 1001. Maintaining better skin contact means better data acquisition in the absence of interference and / or with reduced noise.

[0036] Furthermore, the function of maintaining contact involves a light-guiding effect, which can be achieved when LEDs and sensors of different heights communicate through the light guide of the encapsulation material 121a without air gap interference. Since there is no air gap from the transmitter to and through the light guide 121a, and the curved surface maintains essentially constant contact with the skin, there is no air gap interference during the transmission into, through, and reflected back from the skin, and back to the sensor via the same light guide material 121a (both transmission and reflection refer to light propagation). This reduces the inefficiency caused by light scattering at air gap interfaces (air gaps allow light to reflect from the skin or other surfaces). In other words, the encapsulation of the LED and sensor eliminates air gaps between them and the skin, providing a light-guiding effect to the skin, and the curved surface ensures high-quality, low-scattering reception of light entering the skin and reflecting off the skin and bone. The light guide and the curved lens surface maintain continuous contact between the skin and the lens, reducing signal loss due to skin reflection. The signal-to-noise ratio is reduced, and the quality of data acquisition is improved.

[0037] This lens 121b can therefore be used for one or more purposes, in some cases including: 1) providing a "light guide" effect to ensure equivalent or other high-quality coupling to LEDs and sensors at different heights and equivalent or other high-quality substantially constant fit to the skin, thereby reducing motion artifacts; 2) focusing emitted light through the skin to the bone; and 3) focusing reflected light through the skin to the photodiode sensor.

[0038] It should also be noted that the radius of the lens can be designed to maximize the contents of 1) through 3). The height of the lens is designed so that it can protrude from above the composite adhesive 113 of device 100 and penetrate the skin, but not to a depth sufficient to affect the capillary bed, as this would also result in the generation of undesirable data. Furthermore, there is no need for, and no need for, high control over the bending radius and the angle of LED light emission, because the LEDs used for skin penetration (e.g., red and infrared LEDs) provide a wide array of emission angles, and therefore a large array of reflected light waves will be focused back to the sensor through various curved surfaces. That is, curved surfaces help maintain contact during movement (accidentally or intentionally) and are less important for the angle of emission through the skin versus the angle of reflection back to the sensor. In other words, many different bending radii have little difference in their effect on the emission and reflection of data / waves; therefore, the wide-angle emission of the LED takes into account multiple radii. However, this bending may impose more limitations on the process of maintaining contact due to the movement of device 100; for example, a smaller degree of bending will make rolling less likely, and a very small radius of curvature will result in the inability to emit or receive an equal amount of data.

[0039] In some implementations, for devices containing LEDs and sensors within a compartment of approximately 12.6 mm × 6.6 mm, the range of curvature radii proven useful is approximately between 20 and 40 mm (radii of curvature of 20.34 mm and 39.94 mm have proven useful). It should also be noted that the LEDs can be located on one or the other side, or on two opposite sides, or possibly at four or more substantially equidistant points around the sensor, and can provide the desired results.

[0040] It should also be noted that, such as Figure 1H and 1K As shown in one of the arrangements, the pulse oximetry method of this application may involve multiple light sources and / or sensors. Typical pulse oximetry circuitry systems use one light source (LED) per wavelength (typically red, infrared, and others). However, the devices and / or methods of this invention can use multiple light sources per wavelength. This allows for questioning of a wider area of ​​the capillary bed located above / within the patient / wearer, thereby reducing the effects of local motion artifacts. Similarly, multiple sensors can be used for the same purpose or advantage.

[0041] Furthermore, combining right leg drive and / or surrogate right leg drive with pulse oximetry can offer additional advantages. Right leg circuitry, surrogate right legs, and / or right leg drives for chest, forehead, or other electrode locations can remove common-mode noise and power line noise that would / may otherwise be capacitively coupled to the pulse oximetry sensor, and attenuate the effects of noise generated therein. The combination of right leg drive and / or surrogate right leg drive with [equipment / device] for [electrode / device] ... Figure 1K as well as Figure 1K The combination of the lens described herein with the improved pulse oximetry method can significantly reduce this noise and thereby enhance the quality of data acquisition. For the driving electrodes, see further details below.

[0042] Figure 1D A first example of the adhesive 113 used in this application is provided. The adhesive layer 113 is a double-sided adhesive for application to the underside 102 of the device 100, and a different type of adhesive may be used on the second side for adhesion to the skin of a human patient (not shown). Different types of adhesive materials can be used because the materials selected for the adhesive layer to be adhered to are different; typically, the materials to be adhered are materials for circuitry or circuit boards connected to the device 100, and materials to be adhered to the patient's skin (not shown separately) on the patient side. A protective backing 114 may be arranged on the patient side until it is desired to apply the protective backing to the patient. It should be noted that in many applications, the adhesive 113 is anisotropic because it is preferably conductive in only a single direction or substantially a single direction, for example, on an axis perpendicular to the surfaces of the adhesive contact. Therefore, such an adhesive, bonded to the adhesive layer on the electrical contacts or electrodes 108, 109, and 110, can produce good electrically conductive contacts for signal communication. It should be noted that, in Figure 1D The example adhesive 113 shows one or more corresponding light apertures 111b / 112b, which, together with one or more light guides 111a / 112a in or through layer 105, are used to transmit light, thereby for communication of optical data typically involved in pulse oximetry.

[0043] The adhesive can therefore be placed or arranged on the device 100, in some embodiments, in a substantially permanent manner or in a manner that allows for some degree of replaceability. In some embodiments, Figures 1A to 1DThe devices shown in 1G without (or in some embodiments with) adhesive are reusable. In many of these cases, the adhesive layer 113 can be removed and replaced before each subsequent use, although this does not preclude the possibility of subsequent reuse of layer 113. In the first or subsequent use of the replaceable adhesive layer 113, the user applying the device to a patient can be, for example, a physician or technician or even the patient themselves, who applies the conductive transmission adhesive 113 to the patient side 102 of the device 100. The protective backing 114 can then be removed, the device is adhered to the patient, and activated.

[0044] Once the device is applied to a patient / wearer, it can be activated in various ways. In some cases, activation may be preset not necessarily to be an affirmative activation interaction from a doctor or patient, because inertial activation and / or pulse oximeter activation can be substantially automatic, for example, automatically activated upon receiving sufficient minimal input (motion in the case of light reflection of blood flow in an inertial system or pulse oximeter). However, buttons may be provided at access point 106 or some other location adjacent to the electronics to allow the patient to start or stop the device, or to mark events if needed. In one exemplary embodiment, the device may be worn for a duration such as two weeks for substantially continuous data collection, or for data collection at time intervals preferred and established by or within the system of this application.

[0045] After the monitoring period ends, the physician, technician, patient, or other person can remove the device from the patient, in some cases using alcohol to remove adhesive, and establish a data communication connection for data transfer, for example, using wireless communication or by inserting / connecting a USB or similar data connector to download data. The data can then be processed and / or parsed, and in many cases, interpreted immediately if needed. Onboard power may include a battery pack, which can also be recharged between uses, and in some implementations, can be quickly and fully charged in approximately 24 hours, after which the device can be considered ready for the next patient or the next use.

[0046] Certain alternative conductive adhesives may be used in this application. Figure 1E , 1F 1G shows such an alternative conductive adhesive 113a; Figure 1E The lower plane view and Figure 1F and 1G Elevation side view (in Figure 1G (Connected to device 100). In some embodiments, the conductivity as described above can be anisotropic; it is conductive, if not completely, primarily in the Z-axis direction; the Z-axis direction is... Figure 1E The paper surface is perpendicular (perpendicular to the paper surface inwards and / or outwards), and / or relative to... Figure 1F The horizontal major axis of the device 100 in the implementation view is perpendicular or transverse.

[0047] This particular example implementation includes a composite adhesive 113a, which itself may include certain non-conductive portions 113b and one or more conductive portions 113c. According to the adhesive 113 described above, the composite adhesive 113a may be a double-sided adhesive, such that one side adheres to the patient and the other side adheres to the underside 102 of the device 100 (see [link to documentation]). Figure 1G This allows one or more conductive portions 113c to be arranged or placed at electrical connection and / or conductive contact points that come into contact with the integrated electrodes on the electronic monitoring device 100. Because the electrodes function better when electrically isolated or insulated from each other, the adhesive can also be arranged more specifically in some of the following embodiments to make each electrode electrically contact or connect with the patient's skin.

[0048] like Figure 1E and 1F As shown, the three isolated conductive portions 113c can be arranged separately from each other via the non-conductive body portion 113b. These conductive portions can then correspond to the electrodes 108, 109, and 110 in the example above, and especially as in Figure 1G The illustration is illustrative (note that the proportions of adhesive 113a are exaggerated, and therefore a precise match with the electrodes of device 100 is not necessarily shown). In some examples, electrode regions 113c may be conductive hydrogels that are or are not adhesives, and in some examples, the conductive hydrogel may be made of a viscous conductive material, such as 3M's 98880 hydrogel adhesive (3M, St. Paul, Minnesota). These regions 113c may be isolated from each other by a non-conductive material 113b, such as 3M's 9836 tape or 3M double-sided transfer adhesive 9917 (3M, St. Paul, MN) or equivalents. The additional layer 113d, when used, may be 3M 9917 adhesive and may be bonded to 113b made of 9836 material. These structures can provide the following effect: creating the Z-axis direction of electrode regions 113c (perpendicular to) Figure 1E The paper surface and is perpendicular / cross-cut to Figure 1F and 1G A low-resistivity path is created on the paper (as shown in the image), and a high-resistivity path is created between the electrodes in the X / Y directions. (See also...) Figure 1E , 1F and 1G; in Figure 1E The center is on the same side as the paper, and with Figure 1F and1G (The paper in the image is horizontal and vertical.) Therefore, the composite adhesive strip not only ensures adhesion of the device to the patient but also ensures that both the two or three electrodes shown are electrically connected through the conductive portions of the adhesive strip. The combination of conductive and non-conductive portions reduces signal noise and / or enhances noise-free characteristics. Electrode movement relative to the skin can cause noise; that is, electrodes electrically connected to the skin via the adhesive can cause noise due to movement relative to the skin. However, one or more conductive adhesive portions connected to the individual electrodes in the composite adhesive and subsequently substantially securely attached to the skin will keep the individual electrodes substantially fixed relative to the skin, thereby reducing or even eliminating electrode movement relative to the skin. Removing this movement eliminates noise, thereby providing a clean signal that allows for monitoring of the cardiac P wave, thus increasing the possibility of detecting arrhythmias that cannot be detected by other means. Further explanation follows.

[0049] In some embodiments, an alternative connection and / or insulation structure 113d may be implemented as shown in FIG113d, thereby providing further structural and insulation separation between the electrodes connected to the device 100 on the lower side 102 (see Figure 113d). Figure 1G Despite Figure 1F and 1G The connection and / or insulation structure 113d described in the drawings is shown in a separate form, but the connection and / or insulation structure 113d in these views may be adjacent to the insulating adhesive 113b.

[0050] Certain alternative implementations related to adhesives can be used. In some implementations, the composite adhesive strips used may have features for reducing one or more motion artifacts. Typical ECG attachment systems use conductive adhesive located on the electrodes. However, a hydrogel adhesive can be used here, which is embedded in a continuous laminated adhesive sheet covering a selected area or the entire footprint of the device. The strong adhesive properties of the hydrogel itself, together with the use of adhesive to cover the entire coverage area of ​​the device, ensure a strong bond between the device and the patient's skin. An alternative method of placing the device vertically on the sternum can help reduce motion artifacts, resulting in reduced motion artifacts in one or more of the ECG signal, photoplethysmography waveform, and oxygen saturation signal.

[0051] In some implementations, improvements to the composite adhesive may include waterproofing the hydrogel adhesive to prevent signal amplitude reduction due to decreased ohmic impedance. This also helps prevent degradation of the aqueous adhesive. Specifically, as... Figure 1I and 1JThe non-limiting alternative examples shown herein illustrate that several layers may be used. Here, layer 1 may be an aqueous gel, which is an adhesive designed to make long-term skin contact by absorbing sweat and cells. Layer 2 may also be a layer designed for long-term skin contact; however, layer 2 isolates layer 3 from skin contact. The smaller layer 2 creates a gap between layers 1 and 3. When layers 1 and 3 are bonded together, a watertight seal is formed around layer 2. Layer 2 also isolates the aqueous gel and hydrogel to protect the adhesive properties of the aqueous gel. Layers 3 and 5 are typically electrically insulating, double-sided adhesive-type waterproof layers. These two layers encapsulate the hydrogel adhesive to prevent “short circuits” with respect to layer 4, as described below. Layer 4 is a hydrogel adhesive, which is a conductive element herein. The three island-shaped regions of the hydrogel adhesive in layer 4 must remain electrically isolated from each other. However, because the aqueous adhesive in layer 1 absorbs sweat, it can become conductive and may create a "short circuit" between the three island-shaped regions of the hydrogel adhesive in layer 4, thereby reducing the signal amplitude. However, this "short circuit" can be avoided by the aforementioned layers 3 and 5.

[0052] Some alternative embodiments of this application may include a right leg-driven ECG circuit having one or more electrodes adapted only to the chest (“drive chest electrodes”). In addition to electrodes used for measuring single or multiple lead ECG signals, device 100 may also use, for example, a reference electrode 110 (see [link to application]). Figure 1A , 1C Additional electrodes (such as 1D and 1G) can be used to reduce common-mode noise. This electrode can operate similarly to a commonly used right-leg driven electrode, but in this case, the electrode can be located on the patient's chest instead of their right leg; however, this third / reference electrode can function as a leg electrode. The chest electrode can therefore mimic the right-leg electrode and / or be considered a proxy right-leg driven electrode. Circuitry suitable for operation in this manner, or a portion thereof, may include several amplifier stages for providing gain, as well as filtering to ensure circuit stability and smooth the overall frequency response. This circuitry can be biased to control the common-mode bias of the ECG signal. This implementation of the driven chest electrode can be used in conjunction with a differential amplifier or a measurement amplifier to reduce common-mode noise. In this case, a sensing electrode can be used as one of the ECG electrodes. Alternatively, a single-ended ECG amplifier can be used in cases where the differential ECG signal is referenced to ground or some other known voltage.

[0053] The circuit or sub-circuit 200 using transistor 201 shown in Figure 2 can be such a circuit (also called a module), and therefore... Figure 2AAs further shown, the circuit may include a sensing electrode 202, a driving electrode 203, and an amplifier 204. Both the sensing electrode 202 and the driving electrode 203 are placed on the patient's chest so that they can be electrically connected to the patient. The amplifier 204 may include gain and filtering functions. The amplifier output is connected to the driving electrode, the inverting input is connected to the sensing electrode, and the non-inverting input is connected to a bias voltage 205. The amplifier maintains the voltage of the sensing electrode at a level close to the bias voltage. An additional electrode can then be used to measure the electrocardiogram signal. In practice, in the case described above where conductivity is enhanced by using an anisotropic adhesive portion, similarly or alternatively, using this third electrode as a proxy right leg electrode (i.e., a proxy right leg driving electrode) can provide signal reception in situations where other methods are unavailable. A clean signal can therefore allow reception of the cardiac P wave, which increases the possibility of detecting arrhythmias that cannot be detected by other means.

[0054] Other alternative descriptions of the circuit system include Figure 2B and 2C The content shown; in the non-limiting alternative shown therein, three adjacent electrodes E1, E2, and E3 can be used to acquire ECG signals, with one electrode used as a distal limb electrode in a conventional EGC monitor. Because the electrode-patient interface has associated impedances (Re1 and Re2), the current flowing through the interface will cause a voltage difference between the patient and the electrode. The circuit can use a sensing electrode (E1) to detect the patient voltage. Because this exemplary circuit node has high impedance relative to the circuit ground point (GND), only a very small current flows through the electrode interface, minimizing the voltage drop between the patient and the node. The first of these alternative non-limiting circuits ( Figure 2BThe system also includes an amplifier (U1) whose low-impedance output is connected to a separate drive electrode (E2). This amplifier uses negative feedback to control the drive electrode such that the patient voltage (measured by the sensing electrode E1) equals the bias voltage (V1). This effectively maintains the patient voltage equal to the bias voltage without considering any voltage difference between the drive electrode (E2) and the patient. This voltage difference can include the voltage difference caused by the electric field sensing current flowing between the drive electrode and the patient (through Re2). This setup differs from a conventional "right leg drive" circuit in at least two ways: the drive electrode is placed on the patient's chest (rather than the right leg), and the ECG signal is a single-ended (non-differential) measurement from a third electrode (E3). Because all the electrodes in the chest-mounted example are located on the patient's chest, a small device placed on the patient's chest can contain all the electrodes required for ECG measurement. One possible advantage of single-ended measurement is that the required gain and filtering circuitry (U2 and related components) of the ECG signal can be determined before recording (ECG output). Figure 2C It requires fewer components and is less sensitive to component tolerance matching. Figure 2A , 2B The examples of 2C are non-limiting examples and are not intended to limit the scope of the claims. Those skilled in the art can form other circuits with other circuit elements according to the concepts of the present invention and within the spirit and scope of the claims of the present invention.

[0055] In many embodiments, the system of the present invention may include additional circuitry that can cooperate with the ECG electrodes, which may therefore be accompanied by other sensors to provide time-consistent trajectories as described below: i) ECG p-wave, qrs-wave, and t-wave; ii) oxygen saturation measured using pulse oximetry; and / or iii) xyz acceleration to provide an index of physical activity. Such circuitry may be applied to one or more of the following electrical specifications. The overall system in some embodiments may include continuous operation for up to two weeks (or longer), during which time data is collected. Some embodiments may be adapted to provide up to or even more than 1000 uses. Alternative approaches may include the ability to operate even after or during exposure to liquids or humid environments; in some such examples, this may be water-resistant, waterproof, or watertight; and in some cases, it may function well when fully submerged (in low-salinity water). Other embodiments may include rapid data transfer, such as using HS USB to transfer all data in less than approximately 90 seconds. Rechargeable battery packs may typically be used.

[0056] Another alternative implementation may include an electronic "ground": in the device of the present invention, which is integrally mounted on a flexible circuit board, the grounding layer function can be provided by a coaxial grounding conductor adjacent to the signal conductors. The main advantage of this type of grounding system is that it allows the device to have the flexibility required for fitting and adhering to the skin.

[0057] For electrocardiograms (EKG) or ECGs, some implementations may include an input impedance greater than approximately 10 megohms; some implementations may operate within a bandwidth of 0.1–48 Hz; and some implementations may have a sampling rate close to 256 Hz; and 12-bit resolution may be achieved. For PPGs and pulse oximeters, operation may utilize wavelengths of 660 and 940 nm, an oxygen saturation range of approximately 80–100 Sp, a bandwidth of 0.05–4.8 Hz, a sampling rate of 16 Hz, and 12-bit resolution. For accelerometers, 3-axis measurements may be employed, and in some implementations, a ±2 G range, a sampling rate of 16 Hz, and 12-bit resolution may be used.

[0058] For pulse oximetry, selective removal of ambient light from the pulse oximeter (PPG) may be included. A method and circuit system for reducing errors caused by ambient light during pulse oximetry are described, and... Figure 2D A circuit system selection is shown. A related dual sampling technique is also shown here for removing the effects of ambient light, photodetector noise, dark current, and flash noise.

[0059] exist Figure 2D The schematic diagram illustrates a scenario where the noise signal can be measured first. The light source is turned off, switch S1 is closed, and switch S2 is open. This causes a charge proportional to the noise signal to accumulate on C1. Then, switch S1 is opened. Here, the voltage on C1 equals the noise signal voltage. The light signal can then be measured. The light source is turned on, switch S2 is closed, and charge flows sequentially through C1 and C2. Then, S2 is opened, and the voltage on C2 is maintained until the next measurement cycle, at which point the entire process is repeated.

[0060] If C1 is much larger than C2, then C2 will withstand almost all the voltage, and the voltage across C2 will be equal to one or more noise-free signals. Otherwise, the voltage across C2 will be a linear combination of the previous C2 voltage (p) and the noise-free signal: (C2×s+Cl×p) / (Cl+C2). This has the effect of applying a first-order, low-pass IIR discrete-time filter to the signal. If this filtering effect is not desired, the voltage across C2 can be discharged to zero before each period of signal measurement, so that the voltage across C2 remains only as: (C2×s) / (Cl+C2).

[0061] This circuit can use a transimpedance amplifier to replace the resistor R, a phototransistor to replace the photodiode, and a FET to replace the switch. Additional buffer stages, amplification stages, filtering stages, and processing stages can be connected after the output.

[0062] Some summarization methods can be referenced here. Figure 3 This can be understood, although other summarizing methods can be understood through and based on portions of the remainder of this disclosure. Figure 3 Flowchart 300 may illustrate certain alternative approaches; wherein, the initial operation 301 may be applying device 100 to a patient. In practice, this may include one or more of the alternatives to the adhesive application described above, which may be achieved by means of / using methods such as Figure 1D Adhesives such as 113, or by means of Figure 1E , 1F And / or the adhesive in 1D. Afterwards, as shown, moving along flow line 311, data collection operation 302 can be performed. It should be noted that this can include continuous or substantially continuous collection, or intermittent or periodic collection, or even one-off event collection. This can depend on the type of data to be collected and / or on other characteristics or alternatives, such as whether a long-term data volume is required for ECG, or whether a relatively single data point is useful in certain cases of pulse oximetry (sometimes, a single saturation point may be of interest, e.g., although comparative data may show a trend of a single saturation point over time, it is actually more typical if the single saturation point is significantly too low).

[0063] After that Figure 3 Several alternatives are shown in flowchart 300: a first alternative can proceed along flow line 312 to data transfer operation 303, after which data transfer operation 303 can involve a transfer from device 100 to data analysis device and / or data storage device and / or system (not shown in the flowchart). Figure 3 As shown separately, it may include computing devices, such as those described below. Figure 4 Wireless or wired (e.g., USB or similar) data communication (or similar to the attached diagram). The options at this point are also obvious; however, a first alternative could include proceeding along process line 313 to data analysis operation 304 to analyze data, which could then be used to determine relative health and / or for diagnosing a patient's condition. A computing system, such as a computer (which can be of many types, handheld, personal, mainframe, or others, see [reference]), could also be used. Figure 4(and as described below) can be used to perform this analysis; however, sufficient intelligence can be integrated into the electronics 103 of device 100 to enable certain analyses to run on or within device 100. A non-limiting example could be a threshold comparison, such as for pulse oximetry, where an indication or warning can be activated entirely on or by the electronics 103 of device 100 when a low threshold level is reached (or in some examples, a high pre-high threshold level).

[0064] A similar example is that an alternative process path 312a could be considered to proceed through either of its two branches 312b and 312c. Along process path 312a, and subsequently in the first exemplary path 312b, it is understandable that the data transfer operation 303 could be skipped, thus enabling analysis 304 without a large amount of data transfer. This could explain onboard analysis, for example, according to the threshold example above, or in some cases, depending on the level of intelligence integrated on or within the electronics 103, which could include more detailed analysis. Another point concerns how much transfer might still be required even with the transfer operation 303; since this at one level might involve data from the patient's skin through conductors 108, 109, and / or 110 and then through lead 107 to the electronics 103 for analysis at the electronics 103. Of course, in other examples, the transfer could include off-board downloads to other computing resources (e.g., Figure 4 In some cases, off-board loading of this type of data can allow for or provide more complex analysis by using resources with higher computing power.

[0065] Other alternative approaches may primarily concern the timing and location of data storage. Due to their intelligence, some or no storage devices or memory may be available in or used by the onboard electronics 103 of device 100. If some storage devices (whether few or many) are available on device 100, then some data storage 305 can be implemented along path 312a and through path 312c. This can occur in many cases, even if it doesn't necessarily precede transmission or analysis (note that for some types of data, multiple paths can be used simultaneously, although this may not be at the same time or sequentially (e.g., paths 312b and 312c do not need to be completely independent of each other), so that storage and transmission or storage and analysis can occur without requiring any particular operation to be completed before starting or performing another operation). Therefore, after (or during) storage 305, process path 315a can follow, allowing stored data to be transferred via path 315b to operation 303, and / or via path 315c to operation 304 for analysis. In this storage example (which in many cases could also be an onboard storage example), data can be collected and subsequently stored in local memory, and then loaded / transferred to one or more robust computing resources (e.g., Figure 4 This data is then used for analysis. Generally, the process can include long-term data collection, such as over days or weeks or even longer, and therefore can include remote collection when the patient leaves the doctor's office or other medical facility. Thus, data can be collected from the patient in their real-world environment. After collection, the data can then be transferred from storage devices on device 100 to desired computing resources (e.g., […]). Figure 4 The transmission can be wireless, wired, or a combination of both, such as using Bluetooth or WiFi to connect to a personal computer. Figure 4 (The following is one example), after which the personal computer can transfer the data via the Internet to a designated computer for final analysis. Another example could include connecting to a computer via USB, which could be a PC or a host computer. Figure 4 ), and can be a patient's computer or a doctor's computer used for analysis.

[0066] If device 100 has little or no storage or memory residing on it (or, in some examples, even a large amount of available resident memory), then shortly after collection, it will be necessary or desirable to transfer the data and subsequently store it (see path 313a after operation 303), and / or transfer and analyze the data (see paths 312 and 313), or both. If path 313a is used, then more typically, the data storage device can then be located off-board (although on-board memory can also be used) and computing resources ( Figure 3 Not shown in the text, but see below. Figure 4 () or above, and then any of the paths 315a, 315b and 315c can be used.

[0067] One feature of the invention may include an overall system comprising one or more devices 100 and computing resources (see, for example, see...). Figure 4 The computing resources are onboard or independent of device 100, for example, in personal, mobile, or handheld computing devices (generally powered by...). Figure 4 As provided, the overall system also provides physicians or doctors with the ability to perform real-time in-room analysis and present the collected test data. In some implementations, this will allow on-site data analysis by the device without the use of a third party for data extraction and analysis.

[0068] Alternative embodiments of the invention may therefore include one or more hardware and software combinations for parsing multiple alternative data sources. As noted above, the device 100 of the invention includes hardware that monitors one or more different physiological parameters, subsequently generating and storing relevant data representing the monitored parameters. The system then includes hardware such as device 100 and / or components therein, software, and computing resources (typically in…) for processing therein. Figure 4 (As shown in the diagram). Therefore, the system includes not only data collection, but also data interpretation and related content.

[0069] For example, electrocardiogram traces showing ventricular arrhythmias during intense exercise can be differentiated from the same arrhythmias during rest. Blood oxygen saturation, which fluctuates significantly with exercise, can particularly indicate conditions much more serious than at rest. More combinations of the four physiological parameters are possible, and the ability of the software of this invention to display and highlight potential problems will greatly assist physicians in diagnosis. Therefore, the system described in this invention provides valuable data analysis.

[0070] Certain characteristics that can help achieve this goal can be categorized into Figure 3In one or more of operations 303 and 304, data collected on device 100 can be more easily transmitted / sent to computing resources (again, it can be onboard to device 100 or independent of device 100, for example...). Figure 4 (As shown). For one example, when a patient who has already had the device applied (operation 301) returns to the physician's office after the testing phase of data collection (operation 302), the device is connected to the office via one or more alternative data transmission methods, such as via USB connection to a computer (Windows or Mac) in the office (generally referred to in this invention). Figure 4 (and instructions), thus allowing physicians to perform real-time analysis while the patient is waiting (it should be noted that the device 100 can be removed from the patient or left on the patient while transmitting and analyzing data to determine if more data is needed). In some implementations, the data analysis time may be relatively short, approximately 15 minutes in some implementations, and can be achieved by using a user-friendly GUI (Graphical User Interface) to guide the physician through the analysis software.

[0071] The analysis / software package can be configured to present results to physicians in multiple formats. In some implementations, an overview of the test results can be presented alongside more detailed results, or the overview can replace the more detailed results. In either case, a summary of detected anomalies and / or patient-triggered events can be provided as part of the overview and / or as part of the more detailed presentation. Selecting a single anomaly or patient-triggered event provides the desired flexibility to allow physicians to view additional details, including source data from ECG and / or other sensors. The software package may also allow for data printing and storage with annotations in the industry-standard EHR format.

[0072] In one implementation, patient data can be analyzed using software having one or more of the following specifications. Some alternative capabilities may include: 1. Data acquisition, i.e., loading data files from a device; 2. Data formatting, i.e., formatting source data into an industry-standard file format (e.g., aECG(xml), DICOM, or SCP-ECG) (it should be noted that this data formatting can be part of acquisition, storage, or analysis, or can be a conversion from one format to another (e.g., data in a compact format can be better stored, which may require conversion or other decapsulation for analysis)); 3. Data storage (stored locally, in a clinic / medical facility, or, for example, in the cloud (optionally and allowing for presentation / analysis based on an offline portable browser)); 4. Analysis, particularly including, for example, noise filtering (high-pass / low-pass digital filtering); and / or QRS (heartbeat) detection (in some cases, may include continuous wave transform (CWT) for velocity and accuracy); and / or data / result presentation, which may include one or more graphical user interfaces (GUIs), which more particularly have a comprehensive summary and / or overall statistics and / or anomaly summaries of one or more patient-triggered events; presenting additional levels of detail: one or more strip views of abnormal data such as oxygen saturation, pressure correlation, etc. before and after the event; and / or allowing caregivers to bookmark / annotate / note events and / or print capabilities.

[0073] Additionally, in alternative combinations of hardware and suitable software packages: i) On-device software packages can be adapted to store measurements of data signals acquired from one or more EKG / ECGs (right leg and / or P wave, QRS wave and / or T wave), or oxygen saturation measurements, or XYZ acceleration measurements in a time-consistent manner, so that physicians can access a temporary history of the measurements (i.e., in some examples, maintaining intervals of 1 to 2 weeks), which can provide useful information related to the patient's activity level before, during, and after a cardiac event. ii) An alternative approach is to manage the real-time transmission of real-time measurement parameters to a nearby base station or repeater. And / or, iii) Off-device ECG analysis software designed to identify arrhythmias.

[0074] The aforementioned software may be industry-licensed software provided by a third party, or software particularly suitable for data generated, transmitted, and / or received from the wearable device 100 of this invention. FDA 510(k) is considered preferred throughout the testing process using the standard (MIT-BIH / AHA / NST) arrhythmia database. Such software may be suitable for allowing one or more of the following: automated ECG analysis and parsing by providing callable functions for ECG signal processing; QRS detection and measurement; QRS feature extraction; classification of normal and abnormal ventricular beats; heart rate measurement; measurement of PR and QT intervals; and heart rhythm parsing.

[0075] In many implementations, the software may be adapted to provide and / or be configured to provide one or more of the following measurements:

[0076] Table 1:

[0077] 1. Minimum, maximum, and average heart rate

[0078] 2. Average duration of QRS

[0079] 3. Average PR interval

[0080] 4. Average QT interval

[0081] 5. Average ST deviation

[0082] Furthermore, it can be adapted to identify a wide range of arrhythmias, such as those given below:

[0083] Table 2A:

[0084] 1. Sinus rhythm

[0085] 2. Sinus rhythm + inferior vena cava diameter

[0086] 3. Sinus bradycardia

[0087] 4. Sinus bradycardia + inferior vena cava diameter

[0088] 5. Sinus tachycardia

[0089] 6. Cardiac arrest

[0090] 7. Unclassified heart rhythm

[0091] 8. Artifacts

[0092] The first group of eight arrhythmia types presented above can be identified even in the absence of a discernible P wave. These arrhythmia types are typically identified by existing products in the outpatient monitoring market, as we have proposed.

[0093] The second set or group of arrhythmias described below may require distinguishable and measurable P waves. Some embodiments of the present invention can be adapted to detect and identify such P waves, such as device 100 being able to detect P waves as described above based on the intensity of the P wave affected by the position of device 100 or the patient's physiological condition.

[0094] Table 2B:

[0095] 9. Atrial fibrillation / flutter with slow peripheral vascular resistance.

[0096] 10. Atrial fibrillation / flutter, mechanical heart valves (normal frequency)

[0097] 11. Atrial fibrillation / flutter and repetitive ventricular responses (rapid)

[0098] 12. Grade I atrioventricular block + sinus rhythm

[0099] 13. Grade I atrioventricular block + sinus tachycardia

[0100] 14. Grade I atrioventricular block + sinus bradycardia

[0101] 15. Second-degree atrioventricular block

[0102] 16. Grade III atrioventricular block

[0103] 17. Premature contractions of the atrial tract

[0104] 18. Supraventricular tachycardia

[0105] 19. Ventricular premature contractions

[0106] 20. Ventricular connection

[0107] 21. Ventricular bigeminy

[0108] 22. Ventricular Triad

[0109] 23. Ventricular rhythm

[0110] 24. Ventricular tachycardia

[0111] 25. Bradyventricular tachycardia

[0112] Additionally, in alternative software implementations, some sample screenshots are shown in Figure 5. The first such alternative is... Figure 5AThe alternative shown is an example screenshot of ECG and oxygen saturation data obtained using a block device such as the device 100 of this invention. A very clean signal is shown here (the data has not been filtered or smoothed). Different P waves are also shown (three of which are shown as examples with arrows). P wave detection is crucial for detecting ECG anomalies. Oxygen saturation measured using pulse oximetry is shown in the graph at the bottom. This data is obtained from a device on the chest and is timed in conjunction with the ECG data.

[0113] Figure 5B Another alternative is shown in the example screenshot of the analysis software. This is a sample of ECG data obtained from record 205 of the MIT-BIH arrhythmia database. As analyzed by the system of the present invention, we can see this in the five (5) abnormality types (more normal sinusoidal rhythms) in the event occurrence summary list (top left). The list also shows the number of times each abnormality occurs, the total duration of the abnormality in the entire ECG, and the proportion of time the abnormality occurs in the entire ECG. To view the specific details of each abnormality, the user double-clicks the specific row in the event occurrence summary list, such as... Figure 5C As shown in the image.

[0114] As mentioned above, Figure 5C This is an example screenshot illustrating a specific case of ventricular premature tachycardia. The ECG curve automatically navigates to the specific moment in the ECG waveform and marks the start and end of the event. More detailed data about this specific event is shown in the occurrence details: mean HR, maximum HR, etc., during the event. To illustrate another instance of anomaly in this ECT, the user can click on the ventricular premature contractions (PVC) row in the event occurrence summary, such as... Figure 5D As shown in the image.

[0115] As mentioned above, Figure 5D This is an example screenshot illustrating a specific case of premature ventricular contractions (PVCs). The graph shows the occurrence of PVCs. The start time list (upper middle) shows all instances of PVCs occurring in this ECG, listing the start time for each occurrence. In this case, the user can click on the PVC starting at 00:15:27 (the 11th occurrence). The ECG graph automatically reaches that time point to show and indicate the PVC in the waveform. Because there are three possible PVC scenarios within this time period, all three occurrences are marked.

[0116] As described above, in one aspect of the invention, ECG signals collected in time with pulse oximetry signals can be used to reduce noise in the pulse oximetry signals and allow for the calculation of oxygen saturation values, particularly in environments where the pulse oximetry data sensor is located in a noise-prone location such as a patient's chest. In some embodiments, this aspect can be achieved by the following steps: (a) measuring ECG signals over multiple heartbeats; (b) measuring one or more pulse oximetry signals during the multiple heartbeats such that the ECG signals and the one or more pulse oximetry signals are time-coherent during the one or more heartbeats; (c) comparing a portion of the time-coherent ECG signals during the one or more heartbeats with the one or more pulse oximetry signals to determine a constant component and a major periodic component of each of the one or more pulse oximetry signals; and (d) determining oxygen saturation based on the constant component and major periodic component of the one or more pulse oximetry signals. The measurement of ECG signals and pulse oximetry signals can be achieved through embodiments of the device of the invention. In particular, the pulse oximetry signal can be a reflected infrared signal and a reflected red light signal collected by a photodetector in the device of the invention. The intervals of pulse oximetry signals corresponding to heartbeats can be determined by comparing the signal with a time-consistent ECG signal. For example (and not intended to be limiting), consecutive R-wave peaks in a time-consistent ECG signal can be used to identify such intervals, although other features of the ECG signal can also be used. Once such intervals are identified, the values ​​at the corresponding times within the interval can be averaged to reduce signal noise and obtain more reliable values ​​for the constant component (sometimes called the “DC component”) and the main periodic component (sometimes called the “AC component”) of the pulse oximetry signal (e.g., Warner et al., Anesthesiology, 108:950-958 (2008)). The number of signal values ​​recorded in an interval depends on the signal sampling rate of the detector and processing electronics used. Also, since the duration of the interval can vary, a subset of values ​​within the interval can be averaged. Oxygen saturation values ​​can be calculated from the DC and AC components using conventional algorithms, as described below. The number of heartbeats and the intervals for calculating the averages can vary over a wide range, as described below. In some embodiments, signals from one or more heartbeats or intervals may be analyzed; in other embodiments, signals from multiple heartbeats or intervals may be analyzed; and in some embodiments, the multiple heartbeats or intervals range from 2 to 25, or from 5 to 20, or from 10 to 20.

[0117] In some alternative implementations, a linear regression algorithm can be used to calculate oxygen saturation. Similarly, the patient's ECG signal can be used to determine when a heartbeat occurs. The heartbeat location can be averaged over the relevant time period for each of the two photoelectrovascular volumetric signals. A linear regression of the overall mean can then be used to determine a linear gain factor between the two signals. This gain factor can be used to determine the patient's oxygen saturation.

[0118] ECG data can be recorded temporally in sync with two or more photoplethysmograms (PPGs) of different wavelengths. The heartbeat is detected in the ECG signal. These heartbeats allow for the definition of 'frames' of PPG data within the time interval between two adjacent heartbeats. Two or more of these frames can then be averaged at each time point to create an average frame for that time interval. Because the PPGs are correlated with the heartbeat, the PPG signal is enhanced through this averaging process. However, any motion artifacts or other noise sources that are temporally independent of the heartbeat are eliminated. Therefore, the signal-to-noise ratio (SNR) of the average frame is typically higher than that of a single frame.

[0119] After averaging frames have been constructed for at least two photoplethysmograms with different light wavelengths, linear regression can be used to estimate the gain between the two average frame signals. This gain value can be used to estimate blood oxygen saturation information or other components present in the blood, such as hemoglobin, carbon dioxide, or others. This process can be repeated for additional light wavelengths.

[0120] An exemplary / alternative method of this invention may include, if / when applicable, determining a gain between specific signals, such as determining a gain between red light and infrared frame signals. This gain may first be obtained by averaging the two frames together. This may result in reduced noise in the signal. The gain may also be obtained by performing a linear regression of the relatively combined red light and the relatively combined infrared light and then calculating the ratio of the two results.

[0121] Another approach involves selecting a possible gain value, multiplying that gain value by the average frame signal, and determining the residual error relative to the average frame at different wavelengths. This process can be repeated for multiple potential gain values. While simple linear regression yields the global minimum gain value, this method can also find local minima. Therefore, if the global minimum can represent the correlation caused by motion artifacts, venous blood flow, or another noise source, it can be ignored, and a local minimum can be chosen instead.

[0122] As described above, the patient wearable device of the present invention for achieving the above aspects is particularly useful for monitoring oxygen saturation in noisy areas such as the chest, for example, in areas with significant local skin movement.

[0123] Figures 6A-6C An embodiment of the above aspects of the present invention is shown in the figure. Figure 6A In the diagram, curve A (600) shows the output of the photodiode of the device of the present invention as a function of time, representing the infrared (IR) reflection, and curve B (602) shows the output of the photodiode of the device as a function of time, representing the red light reflection. In some embodiments, alternatively, red LEDs and infrared LEDs are used to illuminate the skin to generate a signal collected by the same photodiode. Figure 6B In the figure, curve C(604) shows that time-synchronized (i.e., time-consistent) ECG data was added. Figure 6A In the curve graph, peaks in the ECG data (e.g., peaks 606 and 608) can be used to define frames or intervals of pulse oximetry data. Additional consecutive frames or intervals are indicated by 612 and 614, and other frames are determined in a similar manner. According to this aspect, pulse oximetry data from multiple frames are collected. The magnitudes of the multiple frames can vary widely depending on the specific application. In some embodiments, the number of frames collected ranges from 5 to 25; in one embodiment, the number of frames ranges from 8 to 10. Typically, frames or intervals of pulse oximetry data contain different numbers of signal samples. That is, the sensor output can be sampled at a predetermined sampling rate, such as 32 samples per second. If the time between ECG peaks varies, the number of samples per frame will vary. In one embodiment, a feature in the ECG data is selected as the starting point of a frame such that the associated peak in the pulse oximetry data is approximately located at the midpoint or center of that frame, and thereafter a predetermined number of signal samples are recorded for each frame. Preferably, in this embodiment, the predetermined number is selected to be sufficiently large to ensure that the peak of the pulse oximetry signal is essentially an intermediate frame. Sample values ​​greater than the predetermined value corresponding to the aforementioned time points are not used. After collecting multiple data frames, the average value at the corresponding time points of these frames is calculated. Based on the value in this average, the AC and DC components of the pulse oximetry data are determined, and these AC and DC components are then used to calculate relative oxygen saturation using conventional methods, such as ratio ratio algorithms, e.g., Cypress Semiconductor document No. 001-26779 Rev A (January 18, 2010). Figure 6CThe basic procedure is summarized in the flowchart. The frame size (i.e., the number of samples) is determined (620). The sample values ​​at the corresponding time points within each frame are summed (622), and then the average value at each time point is calculated, giving the AC and DC components of infrared and red light reflections with reduced noise. In some embodiments, the values ​​of these components can be used to calculate oxygen saturation using conventional algorithms (626). The relative value of oxygen saturation can be converted to an absolute value by calibrating the measurements of a particular embodiment. Calibration can be performed in a controlled environment where individuals are exposed to varying atmospheric oxygen concentrations, and the measured oxygen saturation values ​​are correlated with the corresponding oxygen levels.

[0124] Besides the embodiments described above that compare ECG signals with pulse oximetry signals, several other embodiments for such comparisons are within the understanding of those skilled in the art. For example, to determine the peak value of the AC component of a pulse oximetry signal in the presence of noise, characteristics of the time-consistent ECG signal located before and after the maximum and / or minimum values ​​of the pulse oximetry measurement can be used to reliably determine the peak and trough values ​​of the pulse oximetry measurement when averaging over multiple heartbeats (without needing to average all values ​​of the pulse oximetry signal during multiple heartbeats). For example, if, within an interval, the R-wave peak of the ECG signal is characteristically x milliseconds after the maximum value and y milliseconds before the minimum value of the pulse oximetry signal, then key information about the AC component of the pulse oximetry signal can be obtained by repeatedly measuring only two values ​​in the pulse oximetry signal.

[0125] In some embodiments, the values ​​of infrared or red light reflection measured by the photodiode can be used to estimate respiratory depth and / or respiratory rate. Figure 6D The curve (630) showing the red or infrared value as a function of time is displayed. Figure 6E In the figure, the maximum and minimum values ​​of curve (630) are shown by dashed curves (632) and (634), respectively. The difference between the maximum and minimum values ​​at a given time point is monotonically correlated with the respiratory depth of the monitored individual. Thus, as shown, breathing at time (636) is shallower than breathing at time (638). In some embodiments, the relationship between respiratory depth and time can be monitored and calculated in an individual. Over time, the respiratory rate can be estimated from the curves showing the changes in the maximum and minimum values ​​over time.

[0126] Furthermore, based on the understanding of the respiratory waveform derived from the ECG RS amplitude and / or RR interval, it can be seen that the PPG and / or pulse oximeter described in this application can be used to estimate the respiratory waveform relatively directly. Since the chest expands and contracts during respiration, this motion appears as a baseline drift artifact on the PPG signal. The respiratory signal can be isolated by filtering the PPG data to focus specifically on the respiratory signal. This is particularly relevant to chest-mounted PPGs.

[0127] In addition, chest-mounted accelerometers can / can be used alternatively to measure respiratory waveforms, especially when the user is lying supine. Due to chest expansion and contraction, the chest will accelerate and decelerate (either laterally or depending on orientation), and this acceleration and deceleration can be measured by the accelerometer.

[0128] Any of the PPG and / or accelerometer, device, and / or method can be used separately or in combination with each other, and / or in conjunction with the ECG-based respiratory estimation techniques described above. Using multiple methods can improve accuracy compared to estimations based on a single method. Subsequently, time-domain and / or frequency-domain methods can be used to estimate respiratory rate and respiratory depth from the respiratory signal.

[0129] In some implementations, heart rate timing (e.g., from ECG) and PPG signals can be used to determine pulse conduction time; that is, the time it takes for a pressure wave to travel from the heart to other locations in the body. Measurements of pulse conduction time can then be used to determine or estimate blood pressure. It should be noted that ECG and / or PPG signals can be generated by conventional methods or other methods, systems, or devices developed in the future, or can be generated by wearable devices such as those described in other parts of this application. That is, the algorithms in this application can be independently available and usable in wearable cardiac devices.

[0130] As disclosed herein or elsewhere, the PPG signals of several heartbeats can be averaged by associating each of the PPG signals of several heartbeats with its respective heartbeat. The result is a PPG frame in which the PPG signal associated with the heart rate is enhanced while irrelevant noise is eliminated. Furthermore, since the PPG frames have been associated with heartbeat timing, pulse conduction time can be estimated by determining the location of peaks or troughs associated with the start or end of the frame itself. This can be achieved by finding one or more minimum and / or maximum samples, or by interpolating the signal to find multiple points between the measurement samples. For example, interpolation can be achieved by quadratic fitting, cubic splines, digital filtering, or many other methods.

[0131] Pulse transit time can also be estimated by correlating PPG frames with a sample signal. The time shift that produces the maximum correlation can be determined by shifting the two signals relative to each other. If the sample signal is an approximation of the desired PPG frame, the time shift with the maximum correlation can be used to determine the pulse transit time.

[0132] An exemplary method or algorithm is described herein, and in the appendix Figure 7A , 7B As shown in 7C. First, the method 710 (including portions 710a, 710b and / or 710c, and / or defined by portions 710a, 710b and / or 710c) employs at least one heartbeat (typically ECG) signal 712 and at least one PPG signal 711 as Figure 7A The inputs shown, such as heart rate timing information / signal 712, are used to generate heart rate timing information by detecting R waves or other ECG features from each heartbeat; multiple ECG signals (i.e., from different leads at multiple locations on the body) can be used to obtain a better estimate of the heart rate timing information. PPG 711 can use a single optical wavelength or signals from multiple optical wavelengths. Using the corresponding heart rate timing information associated with each PPG signal 711, each PPG signal 711 is divided into multiple "frames," see [link to relevant documentation]. Figure 7A The PPG frames 1, 2, and N are contained in the PPG frame, where each frame contains a single wavelength of PPG signal within a corresponding heartbeat duration.

[0133] Optionally, but not typically, PPG signal quality estimation can also be performed. One such example is shown below. Figure 7B Method section 710b. This estimation may take into account the variance of the PPG signal, the estimated signal-to-noise ratio of the PPG signal, the saturation of the PPG signal, patient motion information from an accelerometer or gyroscope, noise estimation from ECG or impedance measurements, or other information about the quality of the PPG signal. Figure 7B An example is shown where an accelerometer signal 713 is used in conjunction with the PPG signal 711 to generate a PPG signal quality value / estimate 714. This signal quality estimate 714 can then be used in conjunction with heart rate timing information 712 to generate the gain for each frame; see [link to documentation]. Figure 7B The PPG frame 1 gain, PPG frame 2 gain, and PPG frame N gain are included, where lower signal quality results in a smaller gain. To reduce computation time, signal quality estimation 714 can be omitted, and the gain information can be a constant.

[0134] like Figure 7C As shown, gain information (from...) Figure 7B(PPG frame 1 gain, PPG frame 2 gain, and PPG frame N gain) and frame information (from Figure 7A PPG frames 1, 2, and N are used together (shown herein as a combination / operation) to create a weighted n-sample moving average frame 715, in which the PPG signal associated with heartbeat timing is enhanced while irrelevant noise is attenuated. The number of samples included in frame (n) 715 can be adapted to reduce noise or response time. Additional time-based weighting of the frames can be applied to boost the effect of more recent or recent frames relative to more distant and potentially less relevant frames. This additional time-based weighting can be achieved using IIR or FIR filters.

[0135] Once the average frame for a given instant has been generated, the pulse conduction time 716 can be determined by calculating the shift of the frame signal associated with the heartbeat. This can be achieved simply by calculating the sample exponent 717, where the signal is at its minimum or maximum value, and comparing this signal with the frame range (heartbeat timing) to determine the pulse conduction time. For more accurate results, spline or polynomial fitting can be used to interpolate the signal near the minimum or maximum value 718, allowing the minimum or maximum value to be determined with better accuracy than the sampling rate. Finally, the frame can be compared with a reference frame template 719, where the average frame is shifted relative to the template. This shift, which results in the highest correlation between the average frame and the template, indicates the conduction time 716. The reference template can be a predetermined signal, or it can be adapted to a known conduction time by using long-term frame averages.

[0136] It should be noted that these methods can be used in conjunction with PPG and heart rate timing information obtained from multiple sources, including but not limited to conventional and / or future-developed techniques; or by using one or more of these sources alone or in combination, and / or in conjunction with quality signals (PPG variance, estimated PPG signal-to-noise ratio, PPG signal saturation, patient motion accelerometer or gyroscope data, ECG or impedance measurement noise estimation, or other information about PPG signal quality) obtained from wearable devices and / or systems described below.

[0137] Other alternatives may include data transmission and / or parsing by a local medical facility, such as a physician's office or, for example, an ICU / CCU (Intensive Care / Coronary Care Unit). Accordingly, the device 100, which measures one or more of a number of physiological signals, will be located on the patient's chest and secured with adhesive as described in this application. These physiological signals may include electrocardiograms, photoplethysmography, pulse oximetry, and / or patient acceleration signals. The device transmits the physiological signals wirelessly or via a wired connection (e.g., USB) to a nearby base station for parsing and further transmission when needed. Wireless transmission may use Bluetooth, Wi-Fi, infrared, RFID (Radio Frequency Identification), or other wireless protocols. The device may be powered by wireless sensing, a battery pack, or a combination of both. The device 100 monitors physiological signals and / or collects data representing these signals. The collected data may then be transmitted in real time to a nearby base station via a wireless or wired connection. The device can be wirelessly powered by a base station or battery pack, eliminating the need for wires between the patient and the base station.

[0138] Correlatedly and / or alternatively, wireless monitoring of patients or wearers can be performed in hospitals, including ICUs (Intensive Care Units) or other facilities. Similarly, the small wireless block device of this invention can be used to measure ECG signals on a patient. The signal is then digitized and wirelessly transmitted to a receiver. The receiver converts the signal back to analog format so that the signal is approximately equal to the original ECG signal in amplitude. This output is then presented to an existing hospital ECG display via standard electrode leads. This allows for patient monitoring using existing hospital infrastructure without having to connect the patient to a monitor with any wires. Patient chest impedance can also be measured so that the reconstructed signal is approximately equal to the ECG signal not only in amplitude but also in output impedance. This can be used to detect disconnected blocks. The output impedance can be continuously variable or can have selectable discrete values ​​(e.g., a low value for connecting the device and a high value indicating that the block has begun to loosen). Impedance can also be used to indicate problems with wireless transmission.

[0139] Other alternative implementations may include mounting one or more sensors to the infant's forehead. First, as described above, a method for obtaining oxygen saturation data by mounting a device to the infant's forehead can be used. However, extended or alternative approaches may include coupling an oxygen saturation sensor along with associated position and temperature sensors to the same forehead-mounted device. The combined data can be used to determine whether the infant is at risk of suffocation based on their face-down position.

[0140] Therefore, certain alternative combinations of the present invention may include one or more of the following: 1) selecting a medical-grade adhesive (from many possible sources) based on its ability to be in close contact with the skin for several days (up to 10 days or two weeks in some examples) without harming the skin, and its ability to work with different types of sensors; 2) a conductive electrode or photodetector capable of providing photoresponsive electrical signals from the skin or from tissues on or under the skin; 3) an amplifier, microprocessor, and memory capable of processing and storing these electrical signals; 4) a power supply for the electronics of the present invention, having stored or wireless charging capabilities; and 5) a flexible circuit capable of binding the above components together within a flexible strip that can conform to the skin area of ​​interest.

[0141] Examples of physiological parameters that may be monitored, recorded / collected, and / or analyzed include one or more of the following: electrocardiogram (ECG); light-excited tissue photoresponse for, for example, blood oxygen saturation; pulse rate and related fluctuations; physical activity / acceleration indices. One or more of these parameters may be used in situations where mobile cardiology outpatients are monitored over several 24-hour periods, thereby providing the value of recording continuous ECG signals over several days for post-test analysis, along with simultaneously recorded oxygen saturation and physical activity indices. Similarly, one or more of these parameters may be used in situations where mobile pulmonary patients are monitored over several 24-hour periods to record oxygen saturation and simultaneously record physical activity indices for post-test analysis. Alternatively and / or additionally, one or more of these features can be used to wirelessly (or in some cases wired) monitor hospitalized patients or other patients of interest (e.g., infants) in clinics, emergency rooms, or intensive care units, detecting EKG parameters, oxygen and / or physical activity parameters in some instances, but without storing the parameters; instead, the parameters are wirelessly transmitted to a bedside monitor or a central station monitor, thus freeing the patient from physical wires. In particular, the device of the present invention can be attached to the forehead of an infant for monitoring respiration and oxygen saturation. In other alternatives, the device of the present invention can be used to monitor the respiration and ECG of patients with sleep apnea syndrome.

[0142] Exemplary computer systems or computing resources used in this invention will be described herein, although it should be noted that many alternatives to computing systems and resources are available and workable within the reasonable scope of this invention, so the following is by no means intended to limit the various possible computing alternatives that are appropriately suited to the spirit and scope of this invention.

[0143] Some embodiments of the present invention include multiple steps. Each of these steps may be implemented by hardware components or by machine-executable instructions, which can be used to cause a general-purpose processor or special-purpose processor compiled with those instructions to execute the steps. Alternatively, these steps may be executed by a combination of hardware, software, and / or firmware. Therefore, Figure 4 This is an example of a computing resource or computer system 400 that enables the use of embodiments of the present invention. According to this example, a sample of the example computer system 400 may include a bus 401, at least one processor 402, at least one communication port 403, main memory 404, removable storage medium 405, read-only memory 406, and mass storage device 407. More or fewer of these elements may be used in specific embodiments of the present invention.

[0144] One or more processors 402 can be any known processor, such as, but not limited to, Intel. Ando Or Ando 2 Processor, or AMD Opteron Or Athlon MP Processor, or Motorola The processor product line. One or more communication ports 403 can be any of the following: an RS-232 port shared with a dial-up-based modem, a 10 / 100 Ethernet port, a Universal Serial Bus (USB) port, or a gigabit port using copper or fiber optic cables. One or more communication ports 403 can be selected according to the network, such as a local area network (LAN), a wide area network (WAN), or any network to which the computer system 400 is connected or is adapted to be connected.

[0145] Main memory 404 may be random access memory (RAM), or one or more other dynamic storage devices known in the art. Read-only memory 406 may be one or more any static storage devices, such as a programmable read-only memory (PROM) chip for storing static information such as processor 402 instructions.

[0146] Mass storage device 407 can be used to store information and instructions. For example, a hard drive, such as a SCSI drive, can be used. Series, optical discs, hard disk arrays (such as RAID, for example, the Adaptec series with RAID drivers), or any other high-capacity storage devices.

[0147] Bus 401 communicatively couples one or more processors 402 to other memory, storage devices, and communication blocks. Bus 401 may be a PCI / PCI-X or SCSI-based system bus, depending on the storage devices used.

[0148] Removable storage medium 405 can be any of the following: external hard disk drive, floppy disk drive, Zip drives, CD-ROMs, CD-RWs, and DVD-ROMs.

[0149] The components described above are intended to illustrate certain possible types. Because these examples are merely illustrative embodiments, they do not limit the scope of the invention.

[0150] Embodiments of the present invention particularly relate to devices, systems, methods, media, and settings for monitoring and processing cardiac parameters and data. While a detailed description of one or more embodiments of the invention has been given above, various alternatives, modifications, and equivalents will be apparent to those skilled in the art without departing from the spirit of the invention. Therefore, the above description should not be construed as limiting the scope of the invention as defined by the appended claims.

Claims

1. A method for determining pulse transit time, comprising: generating at least two photoplethysmography, PPG, frames from heartbeat information and one or more PPG signals; creating a weighted n-sample moving average frame using at least two of the PPG frames; and determining pulse transit time by taking a time shift of a frame signal relative to the heartbeat using the n-sample moving average frame.

2. The method of claim 1, wherein, The pulse transit time is used to determine blood pressure.

3. The method of claim 1 or 2, wherein, Each PPG frame contains a single wavelength PPG signal during a respective heartbeat.

4. The method of claim 1 or 2, further comprising the step of generating heartbeat timing information using electrocardiography, ECG, by detecting an R-wave or other ECG feature for each heartbeat.

5. The method of claim 4, further comprising one or more of the following steps: performing a PPG signal quality estimation, wherein The PPG signal quality estimate uses PPG variance, estimated PPG signal-to-noise ratio, PPG signal saturation, patient motion accelerometer or gyroscope data; or performing an electrocardiography, ECG, signal quality estimate; or performing an impedance measurement noise estimate.

6. The method of claim 5, comprising one or more of the following steps: using the signal quality estimate in conjunction with the heartbeat timing information to generate a gain for each PPG frame; using the signal quality estimate in conjunction with the heartbeat timing information to generate a gain for each PPG frame, wherein low signal quality results in a low gain; or using the signal quality estimate as a constant to generate a gain for each PPG frame.

7. The method of claim 6, further comprising using the gain information together with frame information to create a weighted n-sample moving average frame. The method comprises one or more of the following:

8. The method of claim 1 or 2, wherein, the number of samples included in the weighted n-sample moving average frame is adapted to reduce noise or shorten response time; the PPG frames are additionally time-weighted so as to enhance the effect of recent or near PPG frames relative to PPG frames that are progressively more distant and possibly less relevant; and an IIR or FIR filter is used to perform the additional time-weighting.

9. The method of claim 1 or 2, further comprising one or more of the following steps: taking a sample index where the signal of each PPG frame is at a minimum or maximum value and comparing the signal to a PPG frame range represented by heartbeat timing to determine the pulse transit time; using a spline or polynomial fit to interpolate the signal of each PPG frame around the minimum or maximum value to enable determination of the minimum or maximum value with better precision than the sampling rate; or ​ ​ In case the average frame is shifted with respect to a reference frame template, the weighted n-sample moving average frame is compared to the reference frame template; wherein the shift having the highest correlation between the average frame and the template indicates the pulse transit time; wherein the reference frame template is a predetermined signal, or a signal that can be adapted to a known transit time by using a long-term frame average.

10. A device for determining a pulse transit time, comprising: a module for generating at least two photoplethysmogram, PPG, frames from heartbeat information and one or more PPG signals; a module for creating a weighted n-sample moving average frame using at least two of the PPG frames; and a module for determining a pulse transit time by using the n-sample moving average frame to find a time shift of a frame signal with respect to the heartbeat.

11. A system using the apparatus of claim 10, wherein, The device is a wearable health monitoring device.

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