US20090143691A1

US20090143691A1 - System for, and method of, monitoring heartbeats of a patient

Info

Publication number: US20090143691A1
Application number: US12/165,560
Authority: US
Inventors: Budimir Drakulic
Original assignee: Signalife Inc
Current assignee: Signalife Inc
Priority date: 2004-12-09
Filing date: 2008-06-30
Publication date: 2009-06-04
Also published as: WO2006063341A2; US20060129052A1; WO2006063341A3; US7395109B2

Abstract

Heart monitor signals indicating a patient's heart characteristics are amplified without affecting the signal characteristics. The amplified heart monitor signals with atypical characteristics are transmitted to a pattern recognition platform which stores the patient's previously provided signals with atypical characteristics. The patient's present and the previously provided signals with atypical characteristics are compared to select the previously provided signals with characteristics closest to those of the presently provided signals. Database signals identifying different types of heart problems in third parties and having characteristics closest to the patient's selected atypical signals are chosen. Dependent upon the severity of the patient's heart problems identified by the chosen database signals, the monitor transmits the chosen database signals to an individual one of the patient's doctor, the patient's hospital and an emergency facility.

Description

This invention relates to a heart monitor for indicating characteristics of a patient's heart. More particularly, the invention relates to heart monitors which identify the specific problems, if any, of a patient's heart.

BACKGROUND OF A PREFERRED EMBODIMENT OF THE INVENTION

Measurements are provided in a patient of the functioning of various organs in a patient's body. For example, measurements are made of the functioning of the patient's heart and the patient's brain. These measurements are generally made by applying an electrode or electrodes to the skin of the patient at the appropriate position or positions on the patient's body.
The measurements of the functioning of different organs in the patient's body involve the acquisition of signals in different frequency ranges. For example, measurements of the patient's heart occur in a range of DC to approximately two hundred and fifty hertz (250 Hz) and measurements of the patient's brain occur in a range of DC to approximately one hundred and fifty hertz (150 Hz).
The measurement of the functioning of different organs in the patient's body involves signals of miniscule amplitude. For example, the range of voltages produced at an electrode attached to the patient's skin for a measurement of the patient's heart is approximately one half of a millivolt (0.5 mV) to approximately four millivolts (4 mV). The range of the voltages produced at an electrode attached to the patient's skin for a measurement of the patient's brain is approximately five microvolts (5 μV) to approximately three hundred microvolts (300 μV).
When an electrode is attached to the patient's skin to measure the function of an organ such as the patient's heart or brain, the signal generated from the organ has to penetrate from the patient's organ through the body and the patient's skin to the electrode.
Monitors have been provided for many years to measure the characteristics of a patient's heart. The monitors in the other class are disposed on belts which are wrapped around the patient's waist and attached at their opposite ends by a buckle or clasp so as to be retained on the patient's body at the patient's waist. A cable connects electrodes on the patient's body to the monitor. This is called an “ambulatory monitor”
The patient then engages in the normal activities for a period of approximately twenty four (24) hours. After the recording session, the patient returns the monitor to the doctor's office. The signals required for the monitor are then analyzed, either by the doctor or by someone knowledgeable with respect to heart signals, to determine if the patient's heart presents any problems.
There are at least two (2) major problems with the ambulatory heart monitors now in use. One problem is that the ambulatory heart monitor does not faithfully record the patient's heartbeat signals. This results in part from ambulatory movements of the patient during the twenty four (24) hour recording period. When the patient moves during the recording period, artifacts and noise signals are produced which cloud the heartbeat signals. Furthermore, the heartbeat signal is not faithfully reproduced when it is amplified.
Another problem is that the signals cannot be analyzed until the ambulatory monitor is returned to the doctor at the end of the twenty four (24) hour recording period. This is undesirable. It would be better if the heartbeat signals produced by the patient during the recording period could be instantaneously analyzed by experts to identify the problems, if any, in the patient's heart while the problems are occurring. This would be especially critical if the patient was suffering a heart attack during the testing period. Furthermore, it would be better if the signals could be instantaneously analyzed to determine the existence of the patient's heart problems and to determine the severity, if any, of the patient's heart problems and the steps, if any, that should or could be immediately taken, based upon the analysis, to ameliorate the patient's heart problems.

BRIEF DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

A heart monitor acquires signals representing a patient's heart characteristics. The signals are amplified without affecting the original signal characteristics. The heartbeat signals with unusual characteristics are then transmitted to a processing station. The station also contains, in a pattern recognition platform, the patient's previously generated heartbeat signals. The station compares the signals with unusual characteristics and the patient's previously generated signals and selects the previously generated signals closest in characteristics to the signals with the unusual characteristics. A comparator then compares the selected signals and database signals indicating different types of heart problems in third parties and selects the database signals closest in characteristics to the selected signals previously generated by the patient. Dependent upon the patient's heart problem severity indicated by the characteristics of the selected database signals), the monitor transmits the selected database signals to (a) the patient's doctor, (b) the patient's hospital or (c) an emergency number (e.g. 911).

DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a schematic diagram of one embodiment of a system of the invention for monitoring heartbeats of a patient;

FIG. 2 is a schematic diagram of another embodiment of a system of the invention for monitoring heartbeats of a patient;

FIG. 3 is a schematic diagram in additional detail of a preferred system of the invention for monitoring heartbeats of a patient;

FIG. 4 a is a schematic diagram illustrating the signals produced in each heartbeat of a patient;

FIG. 4 b is an enlarged schematic diagram illustrating one of the heartbeats of a patient;

FIG. 5 is a circuit diagram, substantially in block form, of an amplifier system, including a pair of amplifiers and a pair of electrodes, for amplifying low-amplitude signals produced by the patient's heart without affecting the characteristics of the signal and without introducing noise into the signal;

FIG. 6 is a circuit diagram in additional detail of each of the amplifiers included in the amplifier system shown in FIG. 5;

FIG. 7 is a schematic perspective view of the different layers in a patient's skin;

FIG. 8 is a simplified elevational view of an electrode, a patient's skin (on a simplified basis) and a gel for facilitating the coupling between the electrode and the patient's skin and also shows the impedance network formed by the electrode, the gel and the patient's skin.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

In a preferred embodiment of the invention, a patient 10 produces signals indicating heart characteristics of the patient. The signals may be recorded by a heart monitor 12 (FIG. 1) which is disposed on a belt 14 wrapped around the patient. An arrangement of a heart monitor disposed on a belt is well known in the art. The heart monitor may include electrodes attached to the patient's body at strategic positions on the patient's body to indicate the characteristics of the patient's heart at these strategic positions.
The signals may also be provided by a vest 16 (FIG. 2) which is worn by the patient and on which electrodes 18 are disposed for attachment to selected positions on the patient's body. An advanced embodiment of a vest 16 is disclosed and claimed in application Ser. No. 10/664,711 (attorney file RECOM-64412) field in the USPTO on Sep. 17, 2003 in the name of Budimir S. Drakulic as a sole inventor and assigned of record to the assignee of record in this application.
The signals representing heart characteristics of the patient are amplified in an amplifier 20 (FIG. 3) which retains the characteristics of the signals produced by the patient's heart and does not produce noise. A suitable amplifier providing these advantages is disclosed and claimed in application Ser. No. 10/611,696 (attomey's file RECOM-64414) filed in the USPTO on Jul. 1, 2003 in the name of Budimir S. Drakulic as a sole inventor, and assigned of record to the assignee of record of this application. This amplifier will be disclosed in additional detail subsequently in this application since applicant wishes to include a recitation of this amplifier as an element in some of the claims.
The signals from the amplifier 20 are transmitted by a Bluetooth stage 22 to a personal digital assistant (PDA) 24. Bluetooth stages are well known in the art to transmit signals through relatively short distances. PDAs are also well known in the art and may be considered to be a form of a pocket personal computer (PC).
A signal generally indicated at 25 in FIG. 4 is produced in each heartbeat of the patient 10. The signal 25 includes a first signal portion 26 having a positive portion rising to a positive peak P and a negative portion falling to a negative peak Q. The signal 25 also includes a second portion 27 having a positive portion rising to a positive peak R and a negative portion falling to a negative peak S. It additionally includes a third portion 28 having a positive portion rising to a positive peak T and then trailing downwardly, while still positive, from the positive peak T.
The durations of the portions 26, 27 and 28 of the patient's heart signals 25 are useful in determining whether there are any problems with the patient's heart and, if so, what these problems are. The peak amplitudes P, Q, R, S and T in each heartbeat signal are additionally useful in determining whether there are any problems with the patient's heart and, if so, what these problems are. The relative times of occurrence of the successive signal portions 26, 27 and 28 in each heartbeat also have some utility in determining whether there are any problems with the patient's heart and, if so, what these problems are.
The heartbeat signals 25 from the patient 10 are provided to a storage unit 29 to enable subsequent analysis if such an analysis should be desired. The atypical ones of the heartbeat signals are transmitted by a wide area network 31 (WAN) on a wireless basis to a server 30. Wide area networks are well known in the prior art. The atypical signals are those which are different from the signals which are typically generated by a patient. The server 30 is connected to a processing station 34.
The signal database in the processing station 30 contains signals which have been previously generated by the patient's heart when the patient's heart has been connected to the heart monitor 12. These signals may include signals which were generated when the patient was first connected to the heartbeat monitor. In addition, every time that the patient's heartbeat changes by more than a particular parameter, another sample of the patient's heartbeat is recorded in the processing station 34. In this way, a record is accumulated in the processing station 34 of progressive changes in the patient's heartbeat characteristics.
The processing station 34 selects the signals having characteristics which correspond most closely to the atypical signals transmitted to the server 30 through the wide area network 31. As previously indicated, the comparison is based upon various characteristics in the signals including the durations of the signal portions 26, 27 and 28, the wave shapes of the signal portions, the peak amplitudes P, Q, R, S and T of the signal portions and the relative times of occurrence of the signal portions 26, 27 and 28.
The signals selected by the processing station 34 are introduced to a pattern recognition platform 32 and then to a comparator 36 that also receives signals from a database 38. The database 38 stores signals generated by the patient and by third parties (other than the patient 10) and having characteristics indicating different types of heart problems. Each of the different signals in the database 38 provides heartbeat signals having characteristics which indicate an individual type of heart problem different from the heart problems indicated by the other signals in the database.
The comparator 36 compares the signals introduced to the comparator from the pattern recognition platform 32 and from the database 38 and selects, from the database, the signals having characteristics closest to the signals introduced to the comparator 36 from the pattern recognition platform. The comparison is made on the same basis as that discussed at paragraph 28.
A detector 40 is associated with the database 38. The detector 40 indicates where each of the signals selected from the database 38 is to be transmitted by a transmitter 42. If the signals selected from the database 38 indicate a heart problem, but not a serious heart problem, of the patient, the detector 40 instructs the transmitter 42 to transmit the selected database signals to the server 30. In this way, the patient's doctor can consult the server 30 and can analyze the signals and instruct the patient what to do to ameliorate any heart problems that the patient may have. Alternatively, the signals can be transmitted to a personal digital assistant (PDA) 44 of the patient's docket.
At the same time the patient's doctor is informed that an evaluation has to be made of the patient's atypical heartbeat. The doctors can access over the internet the patient's heartbeat in question, together with signals that are obtained from the database 38 and that are close in characteristics to the heartbeat signals obtained from a computer connected to the server 30. If the doctor is not in the office, the evaluation can be made by a personal digital assistant (PDA) 44 in a server client mode using the wireless internet.
When the selected database signals indicate heart problems in the patient of a moderate severity, the selected database signals may be transmitted to a monitor at a hospital 46. The signals may then be analyzed at the hospital 46 to determine the course of action that should be recommended to the patient 10. When the selected database signals are of real severity, the database signals may be transmitted on an urgency basis such as provided by the telephone number 911. This is indicated at 48 in FIG. 3. While the patient is on the way to the hospital, the ambulance can access the server 30 and obtain all of the relevant data by connecting the ambulance computer over a wireless interface to the server 30.
FIG. 7 is a schematic perspective view of the different layers in a patient's skin. As will be seen, there are a number of layers in the patient's skin. The bracketed indications on the left of FIG. 7 represent groupings of layers. These groupings of layers are respectively designated as epidermis, dermis and subcutaneous. They include layers designated as stratum comeum, barrier, stratum granulosum, stratum germinativum and papillae.
Each of the layers in FIG. 7 has an impedance. This is shown on a schematic basis in FIG. 8, which shows an electrode, a gel, the epidermis layer and a combination of the dermis and subcutaneous layers. In FIG. 8, the gel is shown as being disposed between the electrode and the epidermis to facilitate the coupling of the electrode to the epidermis layer with a minimal impedance.
FIG. 5 is a schematic view showing the attachment of an electrode 112 in FIG. 5 to a patient's skin 111 to provide signals for introduction to the amplifier system also shown in FIG. 5. A gel 113 in FIG. 8 may be disposed between the electrode 112 and the patient's epidermis layer to facilitate the attachment of the electrode to the patient's epidermis layer and to reduce impedance. Since each of the layers in the patient's skin has an impedance, the collective impedance of the patient's skin is progressively reduced when the successive layers are removed. With all of the layers in place in the patient's skin, the impedance of the patient's skin may be in the order of several kilohms to megohms. However, the amplifier system in FIG. 5 is constructed to operate satisfactorily even when successive layers are not removed from the patient's skin 111 and the electrode 112 is attached to the epidermis layer.
FIG. 5 is a circuit diagram, primarily in block form, of an amplifier system, generally indicated at 110, constituting a preferred embodiment of the invention disclosed an claimed in application Ser. No. 10/611,696. The amplifier system 110 includes a pair of electrodes 112 and 114 each of which is suitably attached to the patient's skin at a selective position on the patient's body. The electrodes 112 and 114 preferably have an identical construction. The electrode 112 is positioned at a selective position on the skin of the patient's body to produce signals related to the functioning characteristics of an organ in the patient's body. The organ may illustratively be the patient's heart, brain, stomach or intestines. The electrode 114 is positioned on the skin of the patient's body at a position displaced from the selective position to provide reference signals. The difference between the signals at the electrodes 112 and 114 represents the functioning characteristics of the selected one of the patient's organs such as the patient's heart.
The signals on the electrode 112 are introduced to an input terminal of an amplifier generally indicated at 116. The amplifier 116 also has a second input terminal which is connected to the output of the amplifier. In this way, the amplifier acts as a unity gain. The amplifier 116 may be purchased as an OPA 129 amplifier from the Burr-Brown Company which is now a part of Texas Instruments. In like manner, the signals from the electrode 114 are introduced to an input terminal of an amplifier, generally indicated at 118, which may be identical to the amplifier 116. The amplifier 118 has an input terminal which is connected to the output terminal of the amplifier to have the amplifier act as a unity gain.
Resistors 120 and 122 respectively extend from the output terminals of the amplifiers 116 and 118. The resistor 120 is connected to first terminals of capacitors 124 and 126. The second terminal of the capacitor 124 receives a reference potential such as ground. A connection is made from the resistor 122 to the second terminal of the capacitor 126 and to a first terminal of a capacitor 130, the second terminal of which is provided with the reference potential such as ground. The resistors 120 and 122 may have equal values and the capacitors 124 and 130 may also have equal values.
One terminal of a resistor 132 is connected to the terminal common to the capacitors 124 and 126. The other terminal of the resistor 132 has a common connection with a first input terminal of an amplifier 134. In like manner, a resistor 136 having a value equal to that of the resistor 132 is connected at one end to the terminal common to the capacitors 126 and 130 and at the other end to a second input terminal of the amplifier 134.
Since the amplifiers 116 and 118 have identical constructions, they operate to provide signals which represent the difference between the signals on the electrodes 112 and 114. This indicates the functioning of the patient's organ which is being determined by the amplifier system 110. Although the electrodes 112 and 114 are displaced from each other on the skin of the patient's body, they tend to receive the same noise signals. As a result, the difference between the signals on the output terminals of the amplifiers 116 and 118 does not include any noise.
The electrodes 112 and 114 respectively provide an impedance of approximately 10⁶ohms to the amplifiers 116 and 118. Each of the amplifiers 16 and 18 respectively provides an input impedance of approximately 10¹⁵ohms. This impedance is so large that it may be considered to approach infinity. This causes each of the amplifiers 116 and 118 to operate as if it has an open circuit at its input. The output impedance of each of the amplifiers 116 and 118 is approximately 50 ohms to 75 ohms.
Because of the effective open circuit at the input of each of the amplifiers 116 and 118, the output signal from each of the amplifiers 116 and 118 corresponds to the input signal to the amplifiers and does not have any less magnitude compared to the amplitude of the input signal to the amplifier. This is important in view of the production of signals in the microvolt or millivolt region in the electrodes 112 and 114.
The capacitors 124, 126 and 130 and the resistors 120 and 122 provide a low-pass filter and a differential circuit and operate to eliminate the noise on the electrodes 112 and 114. The capacitors 124, 126 and 130 also operate to provide signals which eliminate the commonality between the signals in the electrodes 112 and 114 so that only the signals individual to the functionality being determined relative to the selected organ in the patient's body remain. The capacitors 124, 126 and 130 operate as a low pass filter and pass signals in a range to approximately one kilohertz (1 KHz). The signals having a frequency above approximately one kilohertz (1 KHz) are attenuated.
The amplifiers 116 and 118 are identical. Because of this, a description of the construction and operation of the amplifier 116 will apply equally as well to the amplifier 118. The amplifier 116 is shown in detail in FIG. 6. It is manufactured and sold by Burr-Brown in Phoenix, Ariz. and is designated by Burr-Brown as the OPA 129 amplifier.
As shown in FIG. 6, the amplifier 116 includes an input terminal 150 which receives the signals at the electrode 112 and introduces these signals to the gate of a transistor 152. The source of the transistor 152 receives a positive voltage from a terminal 156 through a resistor 154. The emitter of the transistor 152 is common with an input terminal in a noise free cascode 158.
Another terminal 160 receives the signals on the electrode 114 and introduces these signals to a gate of a transistor 164. A connection is made from the source of the transistor 164 to one terminal of a resistor 166, the other terminal of which receives the voltage from the terminal 156. The emitter of the transistor 164 is common with an input terminal in the noise-free cascode 158. The resistor 166 has a value equal to that of the resistor 154 and the transistors 152 and 164 have identical characteristics.
First terminals of resistors 168 and 170 having equal values are respectively connected to output terminals in the noise-free cascode 158 and input terminals of an amplifier 174. The amplifier 74 provides an output at a terminal 176. The output from the terminal 176 is introduced to the input terminal 160. The amplifier 174 receives the positive voltage on the terminal 156 and a negative voltage on a terminal 178. Connections are made to the terminal 178 from the second terminals of the resistors 168 and 170.
The transistors 152 and 164 operate on a differential basis to provide an input impedance of approximately 10¹⁵ohms between the gates of the transistors. The output impedance from the amplifier 116 is approximately fifty (50) ohms to seventy-five (75) ohms. Because of the high input impedance of approximately 10¹⁵ohms, the amplifier 116 provides an input impedance approaching infinity. This causes the amplifier 116 to provide the equivalent of an open circuit at its input. This causes substantially all of the voltage applied to the input terminal 150 to be provided at the output of the amplifier 116. This is facilitated by the low impedance of approximately fifty ohms (50 ohms) to seventy-five (75) ohms at the output of the amplifier 116. This voltage has characteristics corresponding to the characteristics of the voltage at the electrode 112.
The output signals from the amplifiers 116 and 118 are respectively introduced to the terminal common to the capacitors 124 and 126 and to the terminal common to the capacitors 126 and 130. The capacitors 124, 126 and 130 operate as a low-pass filter to remove noise and to provide an output signal representing the difference between the signals on the electrodes 112 and 114.
The capacitors 124, 126 and 130 correspond to the capacitors C2, C1 and C3 in a low pass filter 176 in application Ser. No. 10/293,105 (attorney's file RECOM-61830) filed on Nov. 13, 2002 in the USPTO and assigned of record to the assignee of record in this application. The capacitors C2, C1 and C3 in application Ser. No. 10/293,105 are included in the low pass filter 76 in FIG. 8-1 (also shown in FIG. 4) of such application. The low pass filter 76 eliminates noise and passes signals through a frequency range to approximately one kilohertz (1 KHz). If any further information may be needed concerning the construction and operation of the low pass filter, reference may be made to co-pending application Ser. No. 10/293,105 to obtain this information.
Although this invention has been disclosed and illustrated with reference to particular embodiments, the principles involved are susceptible for use in numerous other embodiments which will be apparent to persons of ordinary skill in the art. The invention is, therefore, to be limited only as indicated by the scope of the appended claims.

Claims

1-29. (canceled)

30. In combination for determining characteristics of a patient's heart,

a monitor constructed to be applied to the patient's heart to produce signals representing characteristics of the patient's heart,

an amplifier operatively coupled to the monitor to amplify the signals from the monitor without introducing noise to the signals and without changing the characteristics of the signals,

a transmitter for transmitting the amplified signals to the comparator,

a database for holding a plurality of signals provided by third parties, each of the signals being operative to indicate an individual one of a plurality of different heart problems, and

a comparator responsive to the amplified signals and the signals from the database for selecting an individual one of the signals from the database closest in characteristics to the amplified signals.

31. In a combination as set forth in claim 30,

a processing station for providing signals previously provided by the patient to represent characteristics of the patient's heart, and

a pattern recognition platform responsive to the amplified signals and the signals from the processing station to select the signals from the processing station closest in characteristics to the characteristics of the amplified signals,

the comparator being responsive to the selected signals from the pattern recognition platform and the signals from the database for selecting an individual one of the signals from the database closest in characteristics to the selected signals from the pattern recognition platform.

32. In a combination as set forth in claim 30,

depending upon the characteristics of the signals selected from the database, the transmitter being operative to transmit the signals to (a) the patient's doctor, (b) the patient's hospital and (c) an emergency location to obtain a determination of the problems, if any, with the patient's heart.

33. In a combination as set forth in claim 30,

providing successive signals with similar characteristics from the patient's heart and providing atypical signals among the successive signals with similar characteristics and selecting the atypical signals from the successive signals of similar characteristics to provide for the introduction of the atypical signals to the amplifier.

34. In a combination as set forth in claim 30,

depending upon the characteristics of the signals selected from the database, the transmitter being operative to transmit the selected signals to (a) the patient's doctor, (b) the patient's hospital and (c) an emergency location to obtain a determination of the problems, if any, with the patient's heart, and

the monitor providing successive signals with similar characteristics from the patient's heart and providing atypical signals from the successive signals of similar characteristics to provide for the introduction of the atypical signals to the amplifier.

35-46. (canceled)