Patent Application
20150201858
©2008-2015 Global Cardiac Monitors, Inc. A portion of the disclosure of this patent document contains material which is subject to (copyright or mask work) protection. The (copyright or mask work) owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all (copyright or mask work) rights whatsoever
Not Applicable.
1. Technical Field
The present invention relates to a medical diagnostic device for monitoring biophysiological measurements and the transmission thereof. The present invention provides a self-contained macro-electrode with onboard amplifier, filter, and signal processor and wireless transmitter and more specifically the apparatus described herein utilizes spatially resolved potential profiles from a macro-electrode comprising cluster of sensorial sub-electrodes.
2. Background
Interacting cardiac electric fields result in cardiac potentials that may be sensed through the body surface of a subject with metallic or gel electrodes. An electrode is essentially a transducer transforming the charges in electrolytes i.e., anions and cations into electrons and vise-versa for metals in electronic circuits. Anions and cations move with the aid of a perpetual sodium pump that energizes the cell and creates an electrochemical gradient in the intra and extra cellular spaces. This anion and cation movement in the intra and extra cellular spaces along with the conduction system of the myocardium allows for an action potential to travel. Conduction, displacement current flow or capacitive currents flow from one cell to another cell eventually activates and contracts the ventricle pump. Electric fields from the activated myocardium project from within the body outward where subtending electrodes acquire and record the bio-potential on the body surface.
For over a century, there have been recognized benefits of electrocardiogram recordings. However, the diagnostic benefits of electrocardiogram recordings are often left unrealized due to lack of full clinical exploitation. One possible reason for this lack of clinical exploitation may be due to relative difficulties in electrocardiogram administration. In general, electrocardiogram administration requires manipulating a bulky apparatus. Due to this inherent bulkiness, electrocardiogram administration is restricted mainly to clinics, hospitals, and emergency rooms. The efficiency in acquiring an electrocardiogram recording becomes more important when a critical event is timely detected and reported.
Perhaps complexities and perceived problems have been bolstered in association with affixing the recognized standard 12 leads to subjects. To properly utilize the standard 12 leads, subjects must be affixed with all 10 electrodes in the proper anatomical position. Affixing a subject with 12 leads may arguably be justified but not warranted in every case, and certainly should not be generalized such that it needlessly limits the benefit. The benefits garnered from a timely electrocardiogram transmission and interpretation potentially may lead to a subsequent preemption or subsequent intervention measure.
It can be expected that an easy to use macro-electrode will encourage widespread use. Such use is especially compelling when the macro-electrode incorporates such a wide range of technology and includes a foolproof protocol for affixation to a subject. For example, an easily affixed macro-electrode gives one the ability to monitor intervals of the cardiac cycle in real time. This real time monitoring is extremely beneficial in that intercepting cardiac events will enhance the overall healthcare. Additionally, early detection of otherwise undetected cases may lead to a reduction of the growing financial burden seen in the healthcare industry.
Currently, electrocardiogram recordings are widely used in clinical medical practice to detect electrical disturbances that are characteristic of cardiac abnormalities. However, the utility of such devices has several limitations. For example, most devices are bulky. These bulky devices relying on multiple electrodes joined by leads for acquisition. The standard example includes 12 leads that require 10 electrodes for acquisition. Even in the case of fewer electrodes, the acquisition devices require leads connected separate electrodes. The necessary connectivity between the lead and the electrode remains a major and fundamental obstacle for realizing the full benefit from such devices.
Electrocardiogram recordings are based on measuring the potential difference from at least a pair of electrodes. These electrodes are distinctly separated and must be connected with leads that terminate in the amplified stage. A standard example includes 10 electrodes connected to 12 leads or the Frank set which is a three lead set in an orthogonal arrangement. In each case, the electrodes are connected with wires (leads) to the recording device.
The angle formed between the myocardium muscle fibers and the set of miniature electrodes influence the orientation and the grouping constituent clusters. With respect to the sequence of activation, the spread of the activation stimulus moves from endocrinal sites outward to the transmural space. This space is heavily affected by the anisotropic properties of the ventricular muscle. It is intuitive that excitation of the wavefront will spread more rapidly along the long axes of the cardiac cell than in the transverse direction. In ventricular walls, fibers are oriented roughly parallel to both endocardial and epicardial surfaces, however there are some transverse connections between cells. Therefore the spread from one endocardial point may be viewed as oblique. This means that there is a predominant axial movement along the length of the fiber with minimum movement perpendicular or transverse through the fiber. The cumulative effects of cardiac field results in variations in potential profiles.
To further complicate the situation, physiological and pathological variations across the human population also contribute to potential profile variations on body surface. It is common knowledge that a healthy heart may vary in its electrical axes. This is known as a normal variant. In some pathological cases, significant deviations exist such as myocardial hypertrophy. As a consequence to account for the significant variations that may exist across a population, the criterion in forming the sets and subsets of the sub-electrodes or miniature electrodes is that these sets are not necessarily adjacent. A maximum of three groups of electrode subsets form as the potential variations dictate the subset formation. Perhaps, the subsets form toward the direction of a maximum local sensed gradient from the cardiac area under study. Forming the subset of electrodes is somewhat like how sunflowers track the sun and how sunflowers align perpendicular to the sun.
As described above, the spatial potential spread and variations in the iso-potential lines continuum which may be spatially divergent or even highly restricted in certain areas on body surface influences the selection of the subset of electrodes. The intrinsic variation in cardiac potential maps across a population coupled with the difficulty in using biophysiological sensing technology drives the development of a diagnostic device comprising a cluster of sub-electrodes or miniature electrodes. It is understood that bipolar electrodes may diminish the contributions from remote potentials. However, bipolar measurements when confined to relatively small areas can accentuate and reveal contributions from remote potentials.
Several electrode arrangements namely, patches, have been proposed and described. However, for utmost ease of usage, the underpinning principal or challenge remains that the electrodes be adjacent, sufficiently and spatially separated. To avoid this fundamental necessity, others have demonstrated embedded wires in the lamination in several arrangements within patches. However, the obstacle remains that these electrodes are contained within a larger patch whose electrodes must be connected by wires with relatively large straddling separations. Furthermore, no prior art has shown a full acquisition of ECG with memory, full duplex transmitter and a receiver onboard or a single electrode with signal processing and a battery on area spanning less than the area of a typical electrode or an electrode autonomously contained on the same macro electrode of any shape limited to that area.
Nowhere does the prior art describe an iterative process for optimizing a diagnostic signal from a subset of electrodes contained within a cluster of electrodes. Additionally, the prior art does not describe how to obtain the necessary orientation of the sub-electrodes necessary to obtain the optimal biophysiological signal. There is a need to optimize a clinically diagnostic potential gradient from a single electrode comprising clusters of sub-electrodes within an one-inch by one-inch area.
Nowhere does the prior art describe formulating a system that delineates the logical steps needed to determine an algorithm that methodically identifies a structured approach to obtain a measurable bio-potential that is confined to a small area from a cluster of highly localized miniature electrodes. Secondly, the invention includes a design comprising a single small electrode. Ideally, this should be a miniature electrode that is autonomous, easily affixable, and contains a sensory system with detection and transmission capabilities. Thirdly, the prior art lacks an algorithm describing how to collectively measure, obtain, and optimize the end-to-end processes to achieve a diagnostic quality potential in a confined area. And fourthly, the prior art is deficient in demonstrating the specific intricacies of end to end design and ease of implementation to include the analog front end (AFE), digital signal processor (DSP) and real time joint adaptive capabilities of hardware, method for transmissions, power supply, circuit components and within an area of a single typical electrode. And finally, the prior art is deficient in recognizing the value in measuring potential contained to highly localized area and the ability to relate the resulting constellation to measures of muscle and tissue deterioration.
As set out in the inventor's prior pending application, the present invention provides a device and methods of sensing a biophysiological signal of diagnostic quality. In particular embodiments, the invention concerns acquiring a biophysiological signal from a subject using a wireless macro-electrode. In specific embodiments the invention is useful in detecting signals from skeletal muscle tissue, brain tissue, the eye, neurological tissue, nerve tissue, heart muscle, exposed brain tissue and epithelium tissue. In specific embodiments, the subject is a human.
In particular embodiments of the present invention, there is a macro-electrode device for remote sensing of a biophysiological signal comprises a substrate, said substrate comprising a plurality of sub-electrodes, said substrate forming one end of said macro-electrode, a power source, said power source is removably coupled to said substrate, and a processing unit, said processing unit removably coupled to said power source wherein said substrate, power source and processing unit form an integrated, unitary device. In specific embodiments, at least one sub-electrode is a receiver and at least one sub-electrode is an explorer. In other embodiments, at least one sub-electrode is a ground sub-electrode. In certain embodiments, each sub-electrode is connected to the power source. In some examples of the present invention, the power source is a battery. In additional embodiments, the battery is rechargeable.
In certain embodiments of the present invention, the power source has a power connection to the processing unit and a data transfer connection from each sub-electrode to the processing unit. In particular embodiments of the present invention, the processing unit comprises a means for acquiring data, a means for optimizing the biophysiological signal, a means for detecting an anomaly in the biophysiological signal, a means for transmitting the biophysiological signal, a means for storing data. In some embodiments, the processing unit further comprises means for transmitting and receiving speech.
In one embodiment of the present invention, at least two macro-electrode acquire a biophysiological signal and one macro-electrode is the master-electrode and the remaining macro-electrodes are slave-electrodes. In additional embodiments, the biophysiological signals acquired are synchronized and the slave-electrode transmits data to the master-electrode and the master-electrode transmits the synchronized signal. In particular embodiments, the biophysiological source is selected from the group consisting of skeletal muscle tissue, brain tissue, the eye, neurological tissue, nerve tissue, heart muscle, exposed brain tissue and epithelium tissue. In an alternate embodiment, the substrate comprises a circuit board containing an amplifier.
In one embodiment of the present invention, there is a method for remote sensing of a biophysiological signal with a macro-electrode comprising the steps of acquiring the biophysiological signal, filtering the biophysiological signal, selecting the permutation of sub-electrodes that optimizes the filtered biophysiological signal wherein the optimized signal results in a baseline signal, and wirelessly transmitting the baseline signal to a receiver. In some embodiments, the biophysiological signal is acquired from the group consisting of skeletal muscle tissue, brain tissue, the eye, neurological tissue, nerve tissue, heart muscle, exposed brain tissue and epithelium tissue. In specific embodiments, the biophysiological signal is acquired at a rate of per 1/300 second. In certain embodiments, the biophysiological signal is acquired between 0.5 Hz and 10,000 Hz. In some embodiments, the biophysiological signal is filtered to obtain a signal between 0.5 Hz to 10,000 Hz. In specific embodiments, the biophysiological signal is filtered to obtain a signal between 0.5 Hz to 60 Hz. In additional specific embodiments, the biophysiological signal is filtered to obtain a signal between 0.5 Hz to 50 Hz. In other embodiments, optimizing the biophysiological signal is achieved by minimizing the noise and maximizing the signal. In further specific embodiments, anomalies in the baseline signal are detected by interpreting the deviations from the pattern created by the baseline signal.
Additional disclosure and figures are being provided to highlight various improvements to the subject matter set out in copending application Ser. No. 12/192,607, pertaining to: In-situ Real-Time Auto-Regressive Predictive ECG Analysis; Real-Time Patient-Event Reporting; Dynamic Multi-function External Interface; Device Charging; Capacitive Touch UI; A Priori Signal Integrity Verification; Inductive Mode Charging; Electrode/Enclosure Interface; Application of Predictive Analysis to Power Efficiency and Run-time Optimization; and Master-Slave Network Synchronization via Out-of-Band AC-coupled Potential.
For example, in one embodiment the macro-electrode further comprising a dynamic, multi-function external interface for charging the rechargeable battery conductively. In this embodiment, the macro-electrode further comprises a plurality of macro-electrode conductive/magnetic contacts on the substrate connected to the rechargeable battery. The interface further comprises a housing capable of receiving a portion of the macro-electrode containing the macro-electrode contacts, an interface battery within the housing, and a plurality of interface conductive/magnetic contacts located within the interface housing and connected to said interface battery. The plurality of interface contacts is capable of aligning with the macro-electrode contacts and transmitting power to the rechargeable battery when the portion of the macro-electrode is received within the interface housing.
In another embodiment, the macro-electrode further comprises a dynamic, multi-function external interface for charging the rechargeable battery inductively. In this embodiment, that macro-electrode further comprises a first inductive charging coil on the substrate connected to said rechargeable battery. The interface further comprises a housing capable of receiving a portion of the macro-electrode containing the first inductive charging coil, an interface battery within the housing, and a second inductive charging coil located within the interface housing and connected to the interface battery. The second inductive charging coil is capable of aligning with the first inductive charging coil and transmitting power to the rechargeable battery when the portion of the macro-electrode is received within the interface housing.
In another embodiment, the macro-electrode substrate further comprises a capacitive touch user interface.
In another embodiment, the macro-electrode substrate further comprises: a substrate interface structure and a processing unit interface structure. The substrate interface structure comprises a substrate plate having outer and inner faces, wherein the plurality of sub-electrodes are mounted through the plate, the plurality of sub-electrodes further comprising posts extending out from the plate inner face. A plurality of magnets is located on the substrate plate inner face. The processing unit interface structure comprises a processing unit plate having outer and inner faces, a plurality of sub-electrode docking receptacles on the processing unit outer face for receiving the respective plurality of sub-electrode posts, each respective sub-electrode docking receptacle being capable of receiving a signal output from said respective sub-electrode, circuitry connecting each of the sub-electrode docking receptacles to a circuit board within said device, and a plurality of magnets located on the processing unit plate outer face for magnetic attraction to the corresponding plurality of magnets on the substrate inner face.
The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other methods for carrying out the same purpose of the present invention. It should be also realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages will be better understood form the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present invention.
For a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:
As used herein, “a” or “an” means one or more than one.
As used herein, the term “constituent sets” refer to either the 2 set model or the 3 set model compromising the mini electrodes and constituting the an exploring set, a reference set, and a ground set.
As used herein, the term “model” refers to either the sets of 2 or 3 clusters.
As used herein, the term “critical session” refers to a phase wherein an event of significance has been detected, stored and needs to be transmitted or transmission is underway. It is possible that a sight waiting delay is imposed due to a wireless network delay etc.
As used herein, the term “IP” refers to internet protocol which is a protocol used for communicating data across a packet-switched internetwork using the TCP/IP suite of protocols. The Internet Protocol suite, TCP/IP, is the set of communications protocols used for the Internet and other similar networks. It is named from two of the most important protocols in it: the Transmission Control Protocol (TCP) and the Internet Protocol (IP).
As used herein, the term “RF” refers to radio frequency which is a frequency or rate of oscillation within the range of about 3 Hz to 300 GHz. This range corresponds to frequency of alternating current electrical signals used to produce and detect radio waves.
As used herein, the term “measurable” refers to a detectable potential of any diagnostic value from waveform excursions.
As used herein, the term “FIR filter” is a type of digital filter. The impulse response, the filter's response to a Kronecker delta input, is “finite” because it settles to zero in a finite number of sample intervals. The FIR filter as used herein is exemplary, other electronic filters may be used as well.
As used herein, the term “macro-electrode”, refers to a group of two or more sub-electrodes.
As used herein, the term “master-electrode”, refers to a macro-electrode that controls and regulates the activity of other macro-electrodes which are referred to as “slave-electrodes”.
As used herein the term “slave-electrode”, refers to macro-electrodes that are controlled and regulated by a master-electrode.
As used herein, the term “idio-” is a prefix that refers to personal, private, distinct and/or separate.
As used herein, the “common mode rejection ratio” of a differential amplifier (or other device) measures the tendency of the device to reject input signals common to both input leads. A high common mode rejection ratio is important in applications where the signal if interest is represented by a small voltage fluctuation superimposed on a (possibly large) voltage offset, or when relevant information is contained in the voltage difference between two signals.
As used herein, the term “gateway” describes a communications network or a network node equipped for interfacing with another network that uses different protocols. A gateway may contain devices such as protocol translators, impedance matching devices, rate converters, fault isolators, or signal translators as necessary to provide system interoperability. It also requires the establishment of mutually acceptable administrative procedures between both networks. A protocol translation/mapping gateway interconnects networks with different network protocol technologies by performing the required protocol conversions. In some cases, a macro-electrode is configured to perform the tasks of a gateway. In specific examples, a master-electrode is configured to perform the tasks of a gateway.
As used herein, the term “idio-electrode”, “mini-electrode” and “sub-electrode” may be used interchangeably. The term “constellation” as used herein describes the cooperation between two or more sub-electrodes.
As used herein, the term “CSD” refers to “circuit switched data” which is the original form of data transmission developed for the time division multiple access TDMA-based mobile phone systems like Global System for Mobile Communications (GSM). CSD uses a single radio time slot to deliver 9.6 kbit/s data transmission to the GSM network and switching subsystem where it could be connected through the equivalent of a normal modem to the Public Switched Telephone Network (PSTN) allowing direct calls to any dial-up service.
As used herein, the term “SMS” refers to “short message service” which is a communications protocol allowing the interchange of short text messages between mobile telephone devices. Since its inception SMS has expanded from the transmission of text messages to include a number of other types of broadcast messaging.
Patches and electrode clusters for clinical electrocardiography have been described in the prior art. However, the prior art does not describe the three principals necessary for sensing a bio-potential signal. These principles include sensitivity, spatial resolution, and orientation of sub-electrodes wherein the sub-electrodes are located within clusters confined to a relatively small zone or a macro-electrode. Several principals are required to develop a macro-electrode for acquiring a biophysiological signal. First, a sensorial array is required to spatially resolve highly localized gradient profiles from a cluster of mini electrodes to form constituent sets comprising sub-electrodes under a specific decision rule. These clusters will provide at least two constituent sets from various members of the cluster to discern a measurable potential difference. Secondly, a procedure that minimizes the noise and maximizes the signal allows for bio-potential sensory acquisition through a virtual digital steering, selecting, grouping, and hence recording and monitoring from permutations of a plurality of small electrodes or sub-electrodes confined to the size of the typical ECG electrode. Thirdly, potential contributions from all possible permutations of the cluster of sub electrodes are combined and parsed into two or three macro constituent sets. Fourthly, the rotational invariance property is achieved by virtually steering of the miniature electrodes within cluster to obtain measurable potential difference. Another principal needed for developing a macro-electrode is a battery structure that provides power to the body of the electrode, its sensorial mini-electrodes and the onboard processing device. A wireless topology network model is also essential where a remote monitor can interrogate the portable idio-electrode. This combination of distinct principals and essential elements provides a distinct single electrode that is autonomous and lead-free which comprises an onboard DSP with arrhythmia detection capabilities, source encoding, and passive and active wireless transmission. In addition to detection capabilities, the macro-electrode is functional in a Holter mode.
The idio-electrode method partially combines elements of (1) bio-potential interface with a mini-sensorial cluster system to obtain a gradient from a highly localized potential; (2) a procedure that minimizes the noise and maximizes the signal obtained from two or more electrodes to form mini-electrodes constellation(s). These constellations are formed to at least attain a measurable divergence of cardiac field force vector with respect to a source vector, for example: additional elements include, (3) a sample of a subjects electrophysiological activity for arrhythmia monitoring and tracking and (4) a wireless network methodology to maintain connectivity and aid interrogation during critical sessions.
Also as shown in
In some examples of the present invention, the components of the macro-electrode are removable. In this example, the components of the macro-electrode are connected through male/female type connections. Additionally, these male/female type connections may serve as connections to transfer and receive data and power to each component.
A. Acquisition of Bio-Potential Sensory Measurements
The sensory element of the present invention provides for the acquisition of a biophysiological signal such as the cardiac potential. Other measureable biophysiological sources include but are not limited to signals acquired from skeletal muscle tissue, brain tissue, contact lens electrode, neurological sources, nerve tissue, heart muscle, retina, exposed brain surface, and/or sleep apnea. The biophysiological activity is acquired through bipolar measurement which is the measure of the difference between two electrodes. These electrodes are referred to as the reference and the explorer. A third electrode referred to as the ground is used to measure the common mode rejection ratio. This third electrode eliminates the signals below 60 Hz that are common to the reference and explorer electrodes. The electrodes are grouped to form a cluster of electrodes. At least three electrodes are needed to form a cluster. The resulting cluster of sub-electrodes or miniature electrodes form the sensory element of the apparatus. In some situations, not all of the electrodes contribute to the biophysiological signal.
In some situations, the present invention utilizes temporal and spatial-resolved detection of bio-physiological potential to obtain discernable waveforms for diagnostic purposes. The resulting waveform is obtained from highly localized clusters of single or multiple electrodes from a body surface or from organs. In some cases, a minimum of one single electrode may be used to detect the cardiac electrical disturbance. Drawing upon and recognizing the fundamentals of electrochemical processes, inferences can be made with a great degree of certainty in discerning the spatial and temporal gradient divergence based upon the resulting spectra. Selection and the formation of the constellations during the cardiac cycle is dictated by those-electrodes coincident and subjacent to iso-potential contours of high divergence contributing the most to a measurable differential waveform.
The ground electrode in bipolar measurements can only introduce an inconsequential bias in highly localized bio-potential measurements. By correlating and analyzing the spectra of potential contours, a user may determine the placement of the electrodes as well as the minimum number of macro-electrodes needed to attain the desired signal. It is therefore conceivable that fewer than the 10 standard electrodes may be used to predict subjacent lesions or injuries.
The fundamental requirement of attaining a discernable gradient from a single electrode comprising clusters mini-electrodes, in a highly localized potential requires flexible and robust adjustment. Iso-potential lines or contours dictate that a specific orientation of the sub electrodes. It is not necessary for the sub electrodes to be adjacent or uniform. Additionally, not all of the sub-electrodes or miniature electrodes are required to detect the potential variability during the cardiac cycle. In addition, joint adaptive capabilities are required at the circuit level. The sub electrodes connect to a differential amplifier and the amplifier is powered by a battery on board the macro-electrode. The joint adaptive capabilities include but are not limited to capacitors, resistors as well as digital processing abilities.
B. Selecting the Permutation of Sub-Electrodes that Provides the Maximum Potential Gradient
All sub electrodes terminate into an addressable multiplexer and are controlled by instructions from a microprocessor, digital signal processor (DSP), or any other digital processor. Various miniature electrodes or sub-electrodes are combined into their prospective sets to form the minimum 2 or 3 constituent sets. These sets represent the potential points to obtain spatio-temporal waveform excursions, reflective of the cardiac generator that is least noisy. The sets of clusters, comprising the sub-electrodes, are arranged to discern or maximize the signal gradient with the least interference noise.
The selection of the two or three sub-electrodes within the electrode cluster may not necessarily form a adjacent set of sub-electrodes. This condition provides a resource for optimizing the maximum potential gradient. In some situations, the optimal mode is to combine miniature electrodes or sub-electrodes to contribute to a stable gradient preferably of some visually desired display that is free or indiscernibly tolerable, for example AC, alternating current, interference. On board the macro-electrode module is a set of amplifiers along with the addressable multiplexer which communicates all potential permutations of the sub-electrodes to a signal processing unit on board the macro-electrode unit. A set of amplifiers may be used to accommodate the selection of candidate clusters comprising the localized sub-electrodes. The macro-electrode can also be used as a hub to other electrodes forming a single or perhaps any standard electrode arrangement such as the standard 12 leads and/or the Frank set. In this situation one macro-electrode functions as the master-electrode and the remaining macro-electrodes function as slave-electrodes. The orientation selection process from sub-electrodes may be iterative until a desired bipolar potential is attained. The orientation selection process is performed over all possible subsets of the sub-electrodes of the cluster in the 1″.times.1″ area or less. In some cases, the orientation selection process may occur within the size of single electrode or within commercially available electrodes used in ECG recording.
All of the sub-electrodes will be parsed and optimized according to set of criteria to form sets of either two or three electrodes. The resulting set of electrodes may or may not be adjacent. In the situation where there are three electrodes in a set, the set comprises a explorer, a reference, and a ground electrode. In the situation where the desired biophysiological signal results in a ECG, the criterion is maximum ECG excursions falling in the ECG band and void of AC interference. In certain examples, the ground electrode may not be necessary. In this situation, two electrode form a set and each set contains at least one miniature electrode wherein one miniature electrode is sufficient for obtaining a diagnostic signal.
The two sub-electrodes that give the minimum noise and maximum signal provide one criterion for selecting the sub-set of electrodes. While it is desirable, this arrangement is not critical insofar as a sufficiently discernable measurement of any diagnostic value is obtained. The process in selecting the two sub-electrodes begins first by obtaining a differentially sampled electrical gradient. In some cases, the sampling may be digital. It is understood by those of skill in the art that other sampling methods may be used and are within the scope and spirit of the present invention. After sampling, the electrical gradient for every possible permutation of sub-electrode by sub-electrode is computed. The sub-electrode by sub-electrode that gives the minimum noise and the maximum signal is selected. In some examples of the present invention, all remaining sub-electrodes may be used to return current such so that the diagnostic measurements are obtained over the electrode reference with least interference from AC power lines and/or any other interfering source. In some examples of the present invention, at least one sub-electrode may be used to return current. In some situations, the third reference is not needed. In other examples, a FIR notch filter is applied to reduce the AC magnification. The signal may be magnified following the notch at 60 or 50 Hz.
In some examples of the present invention the macro-electrode acquires a biophysiological signal between 0.25 Hz and 10,000 Hz, 0.25 Hz and 9,500 Hz, 0.25 Hz and 9,000 Hz, 0.25 Hz and 8,750 Hz, 0.25 Hz and 8,500 Hz, 0.25 Hz and 8,000 Hz, 0.25 Hz and 7,750 Hz, 0.25 Hz and 7,500 Hz, 0.25 Hz and 7,250 Hz, 0.25 Hz and 7,000 Hz, 0.25 Hz and 6,750 Hz, 0.25 Hz and 6,500 Hz, 0.25 Hz and 6,250 Hz, 0.25 Hz and 6,000 Hz, 0.25 Hz and 5,750 Hz, 0.25 Hz and 5,500 Hz, 0.25 Hz and 5,250 Hz, 0.25 Hz and 5,000 Hz, 0.25 Hz and 4,750 Hz, 0.25 Hz and 4,500 Hz, 0.25 Hz and 4,250 Hz, 0.25 Hz and 4,000 Hz, 0.25 Hz and 3,750 Hz, 0.25 Hz and 3,500 Hz, 0.25 Hz and 3,250 Hz, 0.25 Hz and 3,000 Hz, 0.25 Hz and 2,750 Hz, 0.25 Hz and 2,500 Hz, 0.25 Hz and 2,250 Hz, 0.25 Hz and 2,000 Hz, 0.25 Hz and 1,750 Hz, 0.25 Hz and 1,500 Hz, 0.25 Hz and 1,250 Hz, 0.25 Hz and 1,000 Hz, 0.25 Hz and 750 Hz, 0.25 Hz and 500 Hz, 0.25 Hz and 250 Hz, 0.25 Hz and 100 Hz, 0.25 Hz and 75 Hz, 0.25 Hz and 50 Hz, 0.25 Hz and 25 Hz, 0.25 Hz and 10 Hz, 0.25 Hz and 10,000 Hz, 25 Hz and 10,000 Hz, 50 Hz and 10,000 Hz, 60 Hz and 10,000 Hz, 75 Hz and 10,000 Hz, 100 Hz and 10,000 Hz, 150 Hz and 10,000 Hz, 200 Hz and 10,000 Hz, 225 Hz and 10,000 Hz, 250 Hz and 10,000 Hz, 275 Hz and 10,000 Hz, 300 Hz and 10,000 Hz, 325 Hz and 10,000 Hz, 350 Hz and 10,000 Hz, 375 Hz and 10,000 Hz, 400 Hz and 10,000 Hz, 425 Hz and 10,000 Hz, 450 Hz and 10,000 Hz, 475 Hz and 10,000 Hz, 500 Hz and 10,000 Hz, 525 Hz and 10,000 Hz, 550 Hz and 10,000 Hz, 575 Hz and 10,000 Hz, 600 Hz and 10,000 Hz, 625 Hz and 10,000 Hz, 650 Hz and 10,000 Hz, 675 Hz and 10,000 Hz, 700 Hz and 10,000 Hz, 725 Hz and 10,000 Hz, 750 Hz and 10,000 Hz, 775 Hz and 10,000 Hz, 1000 Hz and 10,000 Hz, 2000 Hz and 10,000 Hz, 3000 Hz and 10,000 Hz, 4000 Hz and 10,000 Hz, 5000 Hz and 10,000 Hz, 6000 Hz and 10,000 Hz, 7000 Hz and 10,000 Hz, 8000 Hz and 10,000 Hz, 9000 Hz and 10,000 Hz, 2.25 Hz and 100 Hz, 10 Hz and 90 Hz, 20 Hz and 80 Hz, 30 Hz and 70 Hz, 40 Hz and 60 Hz, 50 Hz and 60 Hz, 35 Hz and 75 Hz, 45 Hz and 65 Hz, and/or any combination thereof.
In some examples of the present invention the macro-electrode filters the acquired biophysiological to obtain a signal between 0.25 Hz and 10,000 Hz, 0.25 Hz and 9,500 Hz, 0.25 Hz and 9,000 Hz, 0.25 Hz and 8,750 Hz, 0.25 Hz and 8,500 Hz, 0.25 Hz and 8,000 Hz, 0.25 Hz and 7,750 Hz, 0.25 Hz and 7,500 Hz, 0.25 Hz and 7,250 Hz, 0.25 Hz and 7,000 Hz, 0.25 Hz and 6,750 Hz, 0.25 Hz and 6,500 Hz, 0.25 Hz and 6,250 Hz, 0.25 Hz and 6,000 Hz, 0.25 Hz and 5,750 Hz, 0.25 Hz and 5,500 Hz, 0.25 Hz and 5,250 Hz, 0.25 Hz and 5,000 Hz, 0.25 Hz and 4,750 Hz, 0.25 Hz and 4,500 Hz, 0.25 Hz and 4,250 Hz, 0.25 Hz and 4,000 Hz, 0.25 Hz and 3,750 Hz, 0.25 Hz and 3,500 Hz, 0.25 Hz and 3,250 Hz, 0.25 Hz and 3,000 Hz, 0.25 Hz and 2,750 Hz, 0.25 Hz and 2,500 Hz, 0.25 Hz and 2,250 Hz, 0.25 Hz and 2,000 Hz, 0.25 Hz and 1,750 Hz, 0.25 Hz and 1,500 Hz, 0.25 Hz and 1,250 Hz, 0.25 Hz and 1,000 Hz, 0.25 Hz and 750 Hz, 0.25 Hz and 500 Hz, 0.25 Hz and 250 Hz, 0.25 Hz and 100 Hz, 0.25 Hz and 75 Hz, 0.25 Hz and 50 Hz, 0.25 Hz and 25 Hz, 0.25 Hz and 10 Hz, 0.25 Hz and 10,000 Hz, 25 Hz and 10,000 Hz, 50 Hz and 10,000 Hz, 60 Hz and 10,000 Hz, 75 Hz and 10,000 Hz, 100 Hz and 10,000 Hz, 150 Hz and 10,000 Hz, 200 Hz and 10,000 Hz, 225 Hz and 10,000 Hz, 250 Hz and 10,000 Hz, 275 Hz and 10,000 Hz, 300 Hz and 10,000 Hz, 325 Hz and 10,000 Hz, 350 Hz and 10,000 Hz, 375 Hz and 10,000 Hz, 400 Hz and 10,000 Hz, 425 Hz and 10,000 Hz, 450 Hz and 10,000 Hz, 475 Hz and 10,000 Hz, 500 Hz and 10,000 Hz, 525 Hz and 10,000 Hz, 550 Hz and 10,000 Hz, 575 Hz and 10,000 Hz, 600 Hz and 10,000 Hz, 625 Hz and 10,000 Hz, 650 Hz and 10,000 Hz, 675 Hz and 10,000 Hz, 700 Hz and 10,000 Hz, 725 Hz and 10,000 Hz, 750 Hz and 10,000 Hz, 775 Hz and 10,000 Hz, 1000 Hz and 10,000 Hz, 2000 Hz and 10,000 Hz, 3000 Hz and 10,000 Hz, 4000 Hz and 10,000 Hz, 5000 Hz and 10,000 Hz, 6000 Hz and 10,000 Hz, 7000 Hz and 10,000 Hz, 8000 Hz and 10,000 Hz, 9000 Hz and 10,000 Hz, 2.25 Hz and 100 Hz, 10 Hz and 90 Hz, 20 Hz and 80 Hz, 30 Hz and 70 Hz, 40 Hz and 60 Hz, 50 Hz and 60 Hz, 35 Hz and 75 Hz, 45 Hz and 65 Hz, and/or any combination thereof.
In some cases, local potentials are resolved by their sum and difference measurements. Therefore, any permutations of standard ECG recordings can be identified as Lead I, II, II, AVR, V1-V6 or any other known recordings and any linear combination to form standard or derived potential measurements.
At each macro-electrode, there are several stages of amplification with a proper gain to accommodate any classical arrangement such as the standard 12 leads, Frank set and/or any other derived cluster used for monitoring.
C. Detecting Anomalies in the Baseline Signal
In one method of detecting an anomaly in the baseline signal, arrhythmia detection is used. It should be understood by one skilled in the art, that arrhythmia detection is exemplary and that other examples may fall within the scope of the present invention without deviating from the nature and spirit of the present invention. The algorithm for arrhythmia detection is preferably specific for any individual, relying on patient base line wherein a remote operator marks fiducial points automatically. The automatic or “blind mode” of deciding based upon the constituent sets of fiducial points relies on detecting which is initially done by trending, and convergence which is achieved through stepped correlation of matching, classifying and validating the resulting complex. This algorithm assumes pseudo-repeatable, relative regularity, convergent or semi-periodic complexes. In the case when the complex fails to converge, the event signals a potential emergency since convergence of some sort is highly likely with repeatable and successive complexes. The lack of convergence over the preliminary phase of training and acquisition may indicate chaotic electrical activity in the heart. This is also indicative of multi-morphic complexes, which, in relative terms, should not be the case under non-emergency situation.
In the case of supervised or directed provisioning by a remote operator, a paramedic or a nurse, these fiducial points are picked interactively from for example, a display screen and inserted as part of the algorithm firmware. Intrinsic excursion from incoming data is compared to the baseline. If an alternating rhythm is present such as the case when a patient reverts from atrial fibrillation and back to normal and so on, the algorithm will store both rhythm as admissible base lines. In this common situation both rhythms are deemed admissible, albeit different, but do not warrant an emergency. It is not uncommon for a subject to have multiple variations in cardiac rhythms. In this situation, when an additional rhythm is deemed admissible, the algorithm will allow the macro-electrode to store this rhythm as a baseline. It is not likely that a subject will have a plurality of admissible irregular rhythms and even more unlikely that these irregular rhythms will not warrant a medical emergency. The algorithm will maintain and report increases in admissible baseline switching and the rate from one base line to another.
D. Transmission
One aspect of the present invention is the network; namely, the remote receiver and the networking segment that maintains connectivity and enables robust wireless communications through interrogation of the portable electrode. The reduction of the data and elastic signaling during critical sessions enables maintenance of connectivity between the mobile patient and the cellular tower or other communication point. A mobile subject may be interrogated by any of the two prevailing modes such as legacy of circuit switching CSD or the currently emerging packet switching over IP. In the case of CSD, the remote patient's data may be analyzed by using a number assigned to a mobile phone. The case for data over IP is somehow slightly different in that a mobile patient is not seen and is only seen by a local network cluster, as an IP entity over the internet backbone if the remote interrogator sends an SMS burst to activate him/her. By using SMS from a server to reach a remote patient, a full duplex session is established where the mobile patient is a wakened to start transmitting upon the SMS interrogation command. It should be noted that a remote mobile IP user, albeit connected to the network, is “out of sight” in the sense that he/she can not be seen as an autonomously addressable IP entity except by a local router.
Power conservation is a central issue for the viability of the mobile single electrode The data source encoder on board the macro-electrode extracts duplications inherent in the biophysiological waveform. The processor builds correlation functions that measure the “degree of sameness”, within the raw waveform, to extract and “concentrate” representative signal. This representative signal may now be stored or transmitted. Power may be conserved in this “concentration” process through concentrated bits. At the receiver decision space, the decision of whether a bit is one or zero is the amount of energy associated with received bit. The measured effective energy in the decision space is more important than the instantaneous power that is generally required for high data rates. As noted the energy of a contended bit more important in the decision space. Energy is the product of power and time (E=PT). Longer bits resulting from lower data rates (T=1/R, where R is data rate in bits per seconds), can have more energy simply because longer bits remain in the decision space longer which gives the receiver ample time to make a decision. Therefore it can be ascertained that longer bits will consume more energy without increasing the power. This rationale allows for the reduction of the power requirements. The effective power reduction is achieved by “well concentrating”, i.e., source coding, the representative bits and casts each over a longer time period through the RF link or Infrared. An alternative method of preserving power is by providing a the macro-electrode that needs only to be in close vicinity of a local receiving and more powerful gateway. In this case the electrode may or may not have a operational cellular module and the gateway module may optionally provide wireless access to a circuit switched network or an opening to the internet.
E. Power Source
The macro-electrode may be powered through an external power source or through an internal power source on board the macro-electrode. In the situation where the macro-electrode is powered using an external power source, the external power source may be a battery, a solar cell, an electrical outlet or a combination thereof. In the case, where an electrical outlet is used to power the macro-electrode, power may be received through a AC or a DC, direct current, source. Some typical examples of an AC or DC source may include the standard household outlet or an outlet commonly found in a vehicle. The power source may contain any standard type of connection for receiving power such as a USB, universal serial bus, port. The power source is connected to the processing unit, substrate and/or electrodes through any variety of common male/female type connections.
In some cases, the power source is a battery onboard the macro-electrode. In this situation the macro-electrode contains a customized compartment for housing the desired battery type. This compartment is customized with leads, direct connections, or any variation of connections for supplying power to both the processing unit and to the electrodes. The batteries that may be using in the present invention include but are not limited to SR521, AGO, 379, SR41, AG3, LR41, D384/392, LR41 (alkaline), SR41 (silver oxide), 1135SO, silver oxide), 1134SO (silver oxide), 32 (alkaline), 42 (silver oxide), 1.50 (alkaline), 1.55 (silver oxide), SR43, AG12, LR43, D301/386, LR43 (alkaline), SR43 (silver oxide), 1133SO (silver oxide) 1132SO (silver oxide), 80 (alkaline), 120 (silver oxide), 1.50 (alkaline), 1.55 (silver oxide), SR44, AG13, LR44, D303/357, LR44 (alkaline), SR44 (silver oxide), 1166A (alkaline), 1107SO (silver oxide), 1131SOP (silver oxide), 150 (alkaline), 200 (silver oxide), 1.50 (alkaline), 1.55 (silver oxide), SR48, AG8, D309/393, SR48 (silver oxide), 1136SO (silver oxide), 1137SO (silver oxide), 70 (silver oxide), 1.55 (silver oxide), SR54, AG10, LR54, 3875/D389/390, LR54 (alkaline), SR54 (silver oxide), 1138SO (silver oxide), 100 (alkaline), 70 (silver oxide), 1.50 (alkaline), 1.55 (silver oxide), SR55, AGB, D381/391, SR55 (silver oxide), 1160SO (silver oxide), 40 (silver oxide), 1.55 (silver oxide), SR57, SR927W, AG7, D395/399, LR57 (alkaline), SR57 (silver oxide), 116550 (silver oxide), 55 (silver oxide), 1.55 (silver oxide), SR58, AG11, D361/362, SR58 (silver oxide), 1158SO (silver oxide), 24 (silver oxide), 1.55 (silver oxide), SR59, AG2, D396/397, SR59 (silver oxide), 1163SO (silver oxide), 30 (silver oxide), 1.55 (silver oxide), SR60, AG1, D364, SR60 (silver oxide), 1175SO (silver oxide), 20 (silver oxide), 1.55 (silver oxide), SR66, AG4, D377, SR626SW, SR66 (silver oxide), 1176SO (silver oxide), 26 (silver oxide), 1.55 (silver oxide), SR69, AG6, R371, SR69 (silver oxide) or a combination thereof.
In some examples, the electrodes are connected to a circuit board containing an amplifier. In this situation the circuit board is connected to the power source through wires. This arrangement is ideal when there is a fair amount of rotational movement in the electrodes. When the subject moves it causes the macro-electrode to move and the movement of the macro-electrode (battery) lead to rotational movement of the electrodes that cause gaps between the electrode and the body surface of the subject. These gaps result in fluctuations in the half cell potential which lead to distorted signals.
F. Processing Unit
The macro-electrode also comprises a processing unit. This processing unit has a number of functions including, but not limited to, processing and filtering the biophysiological signal, finding the permutation of sub-electrodes that minimize the noise and maximize the signal, wirelessly transmitting and receive data, synchronizing the signal acquired from additional macro-electrodes where necessary and/or storing data. The processing unit is removably coupled to the power source through any common male/female type connection. The processing unit is electrically coupled to the battery and the substrate. The electrical connections may be of any type commonly used in the art to transfer power and/or data.
The processing unit may also transmit and receive speech through the cellular communications module used to transmit the biophysiological signal. This feature allows a subject to identify symptoms by voice. This voice message is time stamped which allows a doctor or nurse to correlate the voice message with a specific moment in the biophysiological data graph. Such processing units are known to those of skill in the art.
G. Multiple Master-Electrodes
The following example is included to demonstrate preferred embodiments of the invention. It should be appreciated by those of skill in the art that the techniques disclosed in the examples that follow represent techniques discovered by the inventors to function well in the practice of the invention, and thus can be considered to constitute preferred modes for its practice. However, those of skill in the art should, in light of the present disclosure, appreciate that many changes can be made in the specific embodiments which are disclosed and still obtain a like or similar result without departing from the spirit and scope of the invention.
In some situations, multiple macro-electrodes may be used to acquire, process and transmit a biophysiological signal. Each macro-electrode is equipped with a RF transreceiver which may communicate individually (single or plurality) in synchronized or unsynchronized mode. In some examples, the macro-electrode communicates to a gateway. This communication may be cellular based or based upon any RF modality. Examples of RF modalities include but are not limited to WiMAX, ZigBee, Bluetooth and Wi-Fi. In some examples, at least two macro-electrodes are preset wherein one macro-electrode is a master-electrode and the remaining macro-electrodes are slave-electrodes. The individual macro-electrodes are further synchronized to multiplex all channels at the receiver. In some cases, the receiver is the master-electrode. The receiver is the gateway that contains the cell for any RF transmitter receiver. The receiver also may be worn as a watch, necklace, article of clothing or in a holster.
For example, in measuring the EKG, the master-electrode may be worn as a watch. Each macro-electrode in this case would measure sub-adjacent potential from the local electrode wherein the subadjacent potential is sampled and transmitted to the gateway. In this example the gateway is a watch. However, the gateway may also be a necklace, holster, etc.
In another example of the present invention, the macro-electrodes are used to measure ST-segment. The ST-segment is usually measured with 12 leads. In this example, the macro-electrodes are in constellation just as with the standard case which uses 12 leads (10 electrodes). It is understood by one skilled in the art that other arrangements are possible. Each sub-adjacent cardiac potential is sampled and transformed into RF bytes that are transmitted to the remote gateway that is portable such as a watch or necklace. These electrodes must be synchronized to one clock for their combination to be meaningful. Although each potential obtained can certainly be used alone for monitoring purposes for arrhythmia but may have (individually) limited ST diagnostic value since the subadjacent potential reveal the same portion of the myocardium (local) and injury currents may well be suppressed at best or vanish completely. Averaging of localized potential is representative of local potential such as right arm or any other standard electrode position. These local potentials are combined by transmitting them to another processing unit, such as a master electrode. This master-electrode can be worn as a watch wherein the multiplexed RF links from various slave-electrodes are synchronized in time so that a meaningful signal is obtained.
In situations wherein more than one macro-electrode is used, one electrode is a master-electrode and the signals of remaining slave-electrodes are synchronized and transmitted to the master-electrode. Echoing is the basis for synchronization. In the synchronization mode the slave-electrodes are initially in a listening mode. The slave-electrodes receive a burst of data packets from the master-electrode. This burst of data packets initiates counting. Travel time is minimum and the main significant differential comes from local processing. All counters must align with the master-electrode. The master-electrode and the slave-electrodes should count within a small differential. The small differential ensured that the slave-electrodes are synchronized with the master-electrode. Synchronization is obtained as long as the counting differential is smaller than the sampling interval of ( 1/300) second.
In some examples of the present invention, multiple electrodes may be self synchronized. In the alternate example, a master-electrode begins a transmission and awaits an acknowledgement from the slave-electrode. Upon receiving acknowledgement, a counter begins on all of the involved slave-electrodes. The master-electrode shall compare his clock (t=0) and received edges of slave's a crude time stamp is established. Assuming the transmission delay is negligible and the processing time is kept to a minimum such as 10.sup.-6 sec. The master electrode retransmits until all slave-electrodes acknowledge then and only then the synchronization process begins. In the case of a large delay i.e., more than a sampling time is observed, each unit knows of other unit clocks especially the master. Counters of the respective modules being to count up or down until the delay spread is minimized. The initial transmission is similar to wake up call to begin counting and to associate each counting with the number of sample or the time of the sample. The counting begins at the time of the master transmitting. Each macro-electrode begins to acknowledge each other's timing and predicts the current local sample number with respect to the virtual clock. Each slave-electrode reports its content to the master-electrode and each macro-electrode acknowledges its delay or equivalently early/late epochs. Each macro-electrode will adjust accordingly as they receive other clicks.
New Disclosure
Additional disclosure and figures are being provided to highlight various improvements to the subject matter set out above and in copending application Ser. No. 12/192,607, pertaining to: In-situ Real-Time Auto-Regressive Predictive ECG Analysis; Real-Time Patient-Event Reporting; Dynamic Multi-function External Interface; Device Charging; Capacitive Touch UI; A Priori Signal Integrity Verification; Inductive Mode Charging; Electrode/Enclosure Interface; Application of Predictive Analysis to Power Efficiency and Run-time Optimization; and Master-Slave Network Synchronization via Out-of-Band AC-coupled Potential. This new disclosure is discussed below.
In-Situ Real-Time Auto-Regressive Predictive ECG Analysis.
Real-Time Patient-Event Reporting.
Discussed are three independent concepts that may have numerous applications as a method in a respective field of study. An ECG device and monitoring of the devices was selected as one embodiment. Although the underlining principals such as Markov chains, late potential chopping are well known to those who are skilled in the subject matter, the formulation of each independent concept using said concept is considered a novel technique.
The following includes information about first concept of early and localized ST-segment detection as well as enhancement of analog to digital converter (“ADC”). The remaining sections are dedicated to the third concept of tracking which ultimately translates into power saving by waking the processor according to the prediction of the Markov sequence of perhaps a hidden Markovian process.
Early and Localized ST-Segment Detection by High Resolution and Late Potential.
This part of the disclosure pertains to assessing local and early stages of Ischemic onset wherein ST-segment is assessed by two independent methods to establish a decision rule and boundary thereof:
1. Computed by any pairwise of electrodes within the cluster of subelectrodes by local energy current.
2. By computing local late potential over (N) cardiac cycles through a combination of high resolution bits corresponding to high frequency spatial and temporal integration of multiple cardiac cycles.
3. By a hybrid combination of 1 and 2 above to enhance (further enhance) said decision boundaries.
4. The above establishes measurably more significant precursors for early detection through localized damage in early stages.
Enhancement of General Purpose Analog to Digital Converters to Attain High Resolution ECG Recordings for Localized Cluster of Electrodes and Standard ECGs.
Standard ADCs for one embodiment such as cellular ADCs that come as built into the cell OEM module tend to have low resolution. This disclosure provides a method to overcome or whiten the flicker noise and hence allow for hi-res recording.
1. Software program to measure spectral noise in the respective band of interest and by reshaping the noise spectrum through finite impulse response (FIR) tap delay line for one embodiment wherein for example the 1/f flicker noise is compensated for by the method of spectral factorization wherein the poles and zeros of the compensating FIR filter are estimated by a method of mmse wherein coefficients of the filter are optimized by this mmse rule as for one example.
2. Another method wherein the ADCs are all sampled sequentially wherein high sampling frequency of tcc signal is taken from various ADCs of the “same” sample thereby decorrelating the flicker noise as done in chopping.
Modelling the ECG Cardiac Complexes as a Sequence of a Markov Chain.
Parameters involved:
More specifically, one can assume the variability of RR—wave intervals of states we assume a specific model for but is extendable to several models (hidden).
Referring now to
Each RRi is a state. For example, take equation 1 where:
A
state transition matrix=p[ak,l] [1.]
The question then becomes, what is the probability of the next N intervals?
More clearly, there is an observation sequence, (O) where:
O={S
3
,S
2
,S
3
,S
3
,S
1
,S
3
,S
2, . . . } [2.]
These Si are the RRi for a Markov chain with 3 states as shown in
Now, given a model (i.e. given by the state transitions of a Finite State Machine) in the present case we have three (S1, S2, S3).
P(O|Model)=P({RRi}N|M) [3.]
O={RR
i
,i=1,3; in any order} [4.]
predicts the next N durations.
In general one may be interested in the next occurrence of an RR as one embodiment of the invention.
To formulate more rigorously we have:
P(O|M)=P({Si}|M) [5.]
where {Si} is a sequence desired or predictable.
In other words, it is desired to predict the next RR interval to occur at so many seconds later having presumed a transition matrix A=[ai,j] for a particular FSM (finite state machine) or more explicitly a “model”. Therefore,
In this case if the initial state is known (i.e. the current interval), then Πk=1 where k corresponds to the index of the S1, S2, S3.
The initial transition probabilities (often referred to as the posterior) are obtained from observing for a long time, e.g., 10 minutes or longer (long enough to establish stationarity), i.e.,
f
x,τ
=f
x [7.]
at least in the wide sense.
The algorithm will then choose the most likely projection given that patient has been stationary without new interfering factors that could alter stationarity.
Dynamic Multi-Function External Interface.
Referring to
The scheme illustrated in
Device Charging.
It will be understood that the battery (power source) and charging circuitry are embedded within the charging sleeve and are not shown here.
DC Mode:
Intrinsic safety and proper alignment of the device is insured by arranging the magnetic polarities of the contacts such that they are configured in an asymmetrical configuration. One such arrangement is shown in
Four(+) inputs are necessary for charging as modern high energy-density batteries mandate the necessity for communication between charger and device(battery). An example of one particular implementation is shown in (
Additional plating of the magnets with a highly stable (non-reactive) and conductive metal (Au, ideally) ensures efficient charge transfer and resistance to corrosion from various environmental conditions.
Smart detection hardware and software within the device ensures that the charging interface is only active when the charging device is attached and a handshake has been verified between the charger and host system over the communication bus thus preventing accidental discharge and short-circuit potential. Thus the charging pathway is physically disconnected from the external outputs unless the charging unit is detected. This intelligent switching behavior allows for the device to dynamically re-configure into various user-interface modes depending on the types of inputs detected. Two modes are outlined below.
Capacitive Touch UI.
In this mode, the magnetic contacts 12 serve as a multi-input capacitive touch user-interface allowing patients and doctors to quickly interact with the module 10 with minimal effort.
A Priori Signal Integrity Verification.
If selected via the capacitive touch interface, these magnetic contacts can be automatically reconfigured for a simple dual input (plus right leg drive output) ECG measurement. In this case, the inputs are routed through an analog multiplexer to the ADC inputs which can provide device administrators (doctors/nurses) with confirmation and verification of the signal integrity, which may be critical during emergency situations. These inputs are by nature very high impedance (just as the primary electrodes on the reverse side of the device) and thus may be considered passive such that there is no danger presented to the patient (e.g. short-circuit potential). Signal integrity verification can be accomplished by placing two fingers from the right hand onto designated contacts for Right-Arm and Right-Leg Drive, and one finger from the left hand onto the designated contact for Left-Arm. The resulting ECG waveform is akin to Lead I. This mode can be selected/entered into the device via the capacitive touch interface described above.
Inductive Mode Charging.
A completely sealed device confers a number of favorable factors including intrinsic safety, greater stability, and elimination of environmental restrictions (e.g. wet conditions, bio-fouling, etc.) yielding a highly robust device. In this implementation the monitoring device 10 utilizes an inductive charging scheme or set-up 40 in which a charging coil 41 is integrated into the device. The charging coil 41 is embedded into the exterior 10a of the enclosure 10, as generally depicted in
In this case, the magnetic contacts 12a on the charging sleeve (
This implementation allows the user to recharge the device while in use and without the need for attachment to an external power source. The higher-capacity of the charger side lithium-polymer battery ensures that the device-side battery can be fully charged. When charging is complete, the battery on the charging sleeve may be re-charged via standard DC-charging methods. An initial prototype is shown in
Electrode/Enclosure Interface.
The interface between the enclosure and the disposable mono-triode is specially designed to provide seamless integration between the analog front-end circuitry and the electrode inputs.
Referring now to
Referring to
Referring now to
As will be understood by those having the benefit of the present disclosure, the outer shape of the macro-electrode 10 could be any desired shape, such as, circular, oval, rectangular, or square. It will also be understood that the charging sleeves 20 could be of a similar but complementary shape with that of the macro-electrode 10. Also, where the macro-electrode is outfitted with a charging coil 41 such as described above, it will also be well understood by those having the benefit of the present disclosure that a corresponding charging coil could take any shape or form. For example, the patient could be wearing the device 10 and come into the presence of the charging field generated by an external charging coil.
Application of Predictive Analysis to Power Efficiency and Run-Time Optimization.
Utilizing highly accurate (over relatively short time-scales) tuned RC oscillators for sleep/low-power mode timers between data-acquisition intervals will result in tremendous power savings and battery-life enhancement. Modern RC oscillators embedded on-chip feature extremely fast stabilization times compared with conventional crystals (of course a crystal will be used for time-sensitive/critical requirements i.e. an RTC running on a low frequency crystal will always be running in the background). A key necessity for taking advantage of this relies on knowledge of when to wake up and look for significant indicators in the user's cardiac rhythm. Utilizing the predictive analysis method described above, once a level of confidence in predictions has been established, precise timing intervals can be programmed to the timer to specify when the device can go into a low power mode and when data-acquisition should occur. During active mode, the acquired data is compared to the algorithms predictions. Disagreement between predictions and acquired data will result in an extended active mode during which data acquisition occurs continuously until the algorithm's confidence criteria are satisfied.
Master-Slave Network Synchronization Via Out-of-Band AC-Coupled Potential.
Further monitoring applications include configurations of multiple sensors (differential voltage inputs) spaced at various locations around the body. A potential application may be monitoring the fetal cardiac activity in conjunction with the mother's, or monitoring fetal contractions while referencing against the mother's electrocardiogram. For these types of applications to be made wireless several forms of synchronization and referencing are required.
A master-slave model is proposed to enable synchronization between the separately located sensors. In this model, one sensor serves the role of master while the remaining sensors act as slaves and are synchronized to the master. In order to make the monitoring as un-obstructive as possible, the slaves can contain substantially less hardware than the master (and hence be of much smaller size). Their role is to collect sensor input data and wirelessly relay it back to the master where the data can be combined, filtered, and analyzed on the master's processor. Hence, slaves may contain only a minimal amount of hardware—analog front-end circuitry, analog to digital converter, a simple microcontroller for managing wireless communication and mode-control, etc.
Synchronization is of paramount importance when making differential voltage measurements. In most ECG applications it may be implicitly assumed that the voltage measurements taken to represent, for example, Lead I were taken at precisely the same time*. Lead I is a differential measurement that is comprised of the voltage measured at the left arm (LA) with respect to the voltage measured at the right arm (RA), i.e.
Lead I=LA−RA. [8.]
A measurement of Lead I where the RA is sampled a second after LA is meaningless. A measurement where RA is sampled a few milliseconds after LA could result in waveform with severe distortion.
*To understand better what is meant by “exactly the same time” it is best to define the relevant time scales. The human heart operates on a time-scale that for the purpose of monitoring ECGs is much slower than modern operating frequencies of digital circuits. While it is composed of smaller components (e.g. cells, atoms, etc.) that operate on much faster time-scales, for the purposes of ECG we need not concern ourselves with those timescales. Our criteria for synchronization is that the period of our operating frequency be <<than the period of any heart activity of interest to physicians when analyzing an ECG.
In standard ECG applications electrode measurements, though possibly spaced far apart, are made at a singular location. That is, the electrodes are connected to conductive elements that are routed to a central ADC (or set of ADCs, which share a common clock, reference potential, etc. on the same PCB or adjoined by electrical wiring). Hence, with respect to the relevant time scale for ECG applications, the measurements are made simultaneously, forming a bipotential measurement.
In order to perform bi-potential measurements between distal points on the body wirelessly, a method for synchronizing data collection is critical. Two such methods are discussed. Given that wireless communication between the distally located sensors is present, one method might be to send a synchronization frame utilizing the existing master-slave network previously discussed. For low power operation, the use of highly stable crystal oscillators to generate a clocking signal is costly, and accumulated drift between the different clocks is inevitable and will need to be corrected. Use of precision trimmed RC oscillators is more attractive for an energy consumption standpoint; however, these come with a tradeoff in clock accuracy and frequency drift will be more severe. A wireless synchronization frame issued periodically from the master to the slave network could be used to correct the accumulated time lag between the sensors; however, this method still suffers complications that are intrinsic to asynchronous communication (asynchronous communication implying different clocks).
Instead, a unified synchronous clocking system between a master-slave network is proposed. In this scheme, the clock signal is coupled to the patient allowing all the sensors to synchronize directly to this signal. The master device generates a stable low-frequency AC signal lying outside the frequency bandwidth of interest for measurement and drives this current into the patient's body via an output electrode. This output might also double as the right-leg drive output. The current output to the patient is of low enough frequency and magnitude to be completely benign to the patient (e.g. similar to transmission line coupling, or the RLD). This signal is thus accessible to all of the sensors in the network and servers as a unified reference clock input amongst devices. In order to generate the high clock rates needed for data-capture, processing, and wireless transmission (wireless transmission may require its own dedicated clock for practical purposes), the reference clock is used as the input to a phase locked loop multiplier onboard each sensor to generate high frequency clock signals within each device. Once each slave on the network is synchronized to the master-issued clock signal coupled onto the patient frequency drift between devices is eliminated. Measurements of the signals of interest are unaffected by the presence of this signal as it will appear as a common-mode signal on differential input amplifiers or alternatively may be removed via a low pass filter. Further synchronization of data-sampling events may be enabled through modulations of the master-output clock signal which may serve as interrupts to cue data acquisition.
To produce bipotential measurements in this configuration, the inputs on each sensor may be configured as single ended inputs such that the measurements are made relative to identical high precision reference voltages on each device. Data from the ADCs are loaded into registers on the microcontroller (or other processor) in sequential order. Additional reference frames may be inserted into the data at periodic intervals to facilitate the combination of the single-ended inputs at the master prior to streaming wirelessly. The master device then polls each device in the slave network to gather the data and combine the potential measurements to produce a bipotential measurement across distal pairs of sensors.
Referring now to
MUX Switch and setting time<<2MS (millisecond) (500 Sps) [9.]
The MUX switch is a high quality analog signal switch. It is possible to enable manual configuration of any pair combination for differential sampling to allow for refinement of signal/spatial region of interest. Though it is possible that maximum potential could be obtained from any arbitrary pair of electrodes, the general rule is that the more distal electrodes will provide the highest possible difference in potential.
Referring now to
Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.
This application claims the benefit of the filing date, and priority to, U.S. Provisional Patent Application Ser. No. 61/926,373 filed Jan. 12, 2014, which is incorporated herein in its entirety. This application is also a divisional and continuation in part of and claims the benefit of the filing date, and priority to, U.S. Nonprovisional patent application Ser. No. 12/192,607 filed Aug. 15, 2008, which is incorporated herein in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61926373 | Jan 2014 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 12192607 | Aug 2008 | US |
| Child | 12192607 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 12192607 | Aug 2008 | US |
| Child | 14595168 | US |
