ES2550695B2 - ELECTROCARDIOGRAPHY DEVICE - Google Patents

Abstract

Electrocardiography apparatus # Electrocardiogram apparatus (ECG), which obtains in parallel the bipolar leads I, II and III of the ECG, comprising only three or four electrodes: two manual electrodes (101, 102) in size and shape to fit fully in each hand and two electrodes for the feet: a left electrode (100) and an optional right electrode (105), with a surface and shape inferior to the sole of the user's foot. # Manual electrodes (101, 102) and electrode left (100) comprise two voltage followers (110, 111, 112) in their connection with the electronic system (200) for obtaining and processing the ECG, while the right electrode (105) can be connected to the mass of the electronic system ( 200). The manual electrodes (101, 102) can be conductive spheres and the foot electrodes, disks, so that they have their corresponding voltage followers (110, 111, 112) within the corresponding electrodes.

Description

Technical sector The present invention relates to an electrocardiography apparatus.

which allows to obtain the three standard bipolar leads of the electrocardiogram (ECG) quickly and comfortably for the patient, which require simultaneously measuring the electrical potential in at least three extremities to know the electrical activity of the

heart.

It is applicable in the hospital and health industry.

State of the known art.

The electrocardiogram (ECG or EKG) offers information about the electrical activity of the heart. In routine cardiological examinations, the ECG is obtained through ten electrodes: four in a respective flat area of each of the four extremities, and another six electrodes on the thorax, in the vicinity of the heart. These electrodes are held by adhesive tape, or are self-adhesive, or incorporate a suction element that guarantees a good contact between the skin and the metal. To reduce the duration of the scan, the electrodes of the extremities may be a clamp that includes at least one conductive surface on one of its two internal faces and that exerts sufficient pressure for said conductive surface to establish firm contact with the skin. In any case, in conventional electrocardiographs, the electrodes are applied to the body of the lying patient, so that he participates in the measurement passively and the electrodes are placed by another person.

This whole procedure takes several minutes because the subject must

5 barefoot and lie on a stretcher, and the electrodes must be placed and held at the appropriate points. In addition, it is an uncomfortable process for many people, particularly those who, due to their advanced age or their state of health, would rather not have to lie down, and also for those whose cultural tradition

10 would rather not have to expose certain parts of their skin, such

as required by the placement of adhesive or clamp electrodes, nor that

someone else touches them.

One way to overcome these inconveniences of slowness,

The discomfort and need of another person to properly apply the electrodes is to obtain the ECG by means of electrodes whose contact with the body is established by the subject rather than serially placed on their skin, where they are subject to pressure or adhesion. To solve this problem, multiple solutions have been proposed.

20 Some solutions consist of a manual device with several electrodes that the user puts in contact with specific points of his body, while touching other electrodes incorporated in the same device. So you can register

25 successively, but not simultaneously, different ECG leads, for example as described in US 2010/0204552, "Apparatus for monitoring biological information", Yamamoto et al., US 2010/0042008, "ECG data acquisition device", Amital and Amital, US 7647093B2 "Apparatus and method for cordless

30 recording and telecommunication transmission of three special ECG leads and their processing ", Bojovic et al. But these devices do not obtain the signals corresponding to the standard leads, they cannot always simultaneously measure all the leads they offer and their use is relatively slow when some of its electrodes must establish contact with the skin of the chest.In addition, the user needs a previous training to identify the contact points and handle the device with his hands.

One way to get rapid ECG measurements is to have the electrodes come into contact with normally exposed parts of the body because that way you don't have to take off any garment and not even unbutton it. Thus, in US Patent 7751872 "Portable

electrocardiogram ", Claymanl describes an extensible element, as an accordion, equipped with two handles at its ends, each of

which includes a metal electrode. By measuring between them a bipolar shunt can be obtained. To get two other leads,

instead of an electrode for the left leg, which is not easy to incorporate into a portable element, as recognized in said document, a clamp electrode for the left ear is proposed, together with an analogue processing of the voltages measured with it

Note that the polarity of these voltages is inverse to that obtained when the electrode is in contact with the left leg. But these last two leads that include the left ear are not standard.

In US 2007/0021815 "Apparatus and method for obtaining cardiac data", Kaise and Findel, it is proposed to obtain the ECG using a platform with at least two metal electrodes, such as a scale used to estimate the composition

body measuring plantar bioimpedance. It is a quick method, which does not

You need no help to put electrodes on your legs because the electrical contact is established with the soles of your feet, which is the usual way of using such scales, but the signal obtained is extremely loud, to the point that the ECG waves are completely masked by the mains interference, as shown in Figure 2 of that document. By digitally processing the signal, a single non-standard branch of the ECG can be achieved.

EP 1583019 A2 (Samsung Electronics Ca. Ltd.) describes how to obtain the three bipolar leads of the ECG using two handle electrodes, one for each hand, and an electrode for the sole of each foot. These four electrodes are arranged on an electronic weighing scale. All electronic scales capable of estimating body composition from the measurement of electrical impedance between the feet have said foot electrodes, and those with the capacity to measure the electrical impedance of various body segments also have handle electrodes. or handlebars. EP 1583019 A2 does not show ECG records obtained with the system described, but it is explained that the ECG, together with the weight and impedance, is used to automatically identify the user of the scale and that the electrodes used to obtain The ECG are the same as those used to measure the electrical impedance of body segments. It is not mentioned whether ECG signals are used for any cardiac diagnosis, nor is any particular geometric characteristic of the electrodes described.

The electrodes used in all the documents mentioned above are called "dry" because they do not require the use of any conductive gel that reduces the impedance of the contact between the metal electrode and the skin. Consequently, the impedance of the dry electrodes depends very much on the contact area, the state of sweat of the skin and the pressure that the body exerts on them. But excessive pressure increases the noise due to the electromyogram (the electrical signal that accompanies muscle contraction). In conventional clamp electrodes, it is the metallic clamp that exerts pressure on the skin, so that there is hardly any noise due to the electromyogram. On commercial scales capable of measuring bioimpedance, to ensure good electrical contact regardless of the exact position of the feet

or of the hands, the area of the surfaces that act as electrodes is many times greater than the effective area of contact with the feet or hands.

A contact impedance that is too high can lead to an attenuation of the ECG signals and a significant increase in electrical interference due to the electrical distribution network or other nearby electrical equipment, to the point of saturating the amplifiers, particularly in uncontrolled electromagnetic environments. , such as a private address. The usual solution to avoid unwanted attenuation of the ECG is to connect a voltage follow-up amplifier (voltage buffer) to the electrode, while to reduce electrical interference, said electrode can be screened by means of an electrical shield connected to a constant potential (the signal mass ), for example, as described by A. Lopez and PC Richardson in "Capacitive electrocardiographic and bioelectric electrodes", IEEE Transactions on Biomedical Engineering, vol. BME-ll, p. 99, 1969, in the case of electrodes placed on the body

In systems for measuring bioimpedance, since this is measured by injecting a frequency signal normally higher than 10 kHz, and therefore much greater than 50/60 Hz of the power grid, possible interference from it can be easily eliminated by A high pass filter. This solution is not valid for the ECG because it has significant components in the band from 0.05 Hz to 100 Hz.

In the proposals described in documents US 2007/0021815 and EP 1583019 A2 cited, and based on an electrode for the sole of each foot and handles or handlebars, the connection of a voltage follower to each electrode would not present greater technical difficulties, but having an electric shield connected to a constant potential on each electrode and without such a shield making it difficult for the hands or feet to establish contact would not be easy.

The present invention describes how to obtain the three bipolar leads of the ECG by overcoming all these limitations identified in the previous systems, and in particular the susceptibility to electrical interference, and without losing the advantages of speed, ease of use and comfort, which are important in both clinical and non-clinical settings.

Brief explanation of the invention.

The invention consists of an apparatus for obtaining electrocardiograms as defined in the claims.

The electrode for each foot is a respective conductive surface on which a foot can be supported such that the conductive area is completely covered by the foot. Therefore it will be of different size and shape according to the intended user, especially separating the case of adults or children.

This device allows you to quickly and conveniently obtain the three standard bipolar leads 1, II and 111 of the electrocardiogram (ECG) of a person standing or sitting, and whose hands, in either case, make contact with two electrodes of such so that these are totally enclosed or covered by the hands, and the electrode of each foot is completely covered by the respective foot. In this way, high immunity to electrical interference due to the electrical distribution network or other electrical equipment in the environment is achieved.

The object of this invention is an apparatus for obtaining simultaneously and quickly, conveniently and easily, the three standard leads to the extremities of the ECG, also called bipolar leads, with high immunity to electrical interference due to the electrical distribution network or other electrical equipment in the environment and without the patient having to expose their arms to place in each of them an adhesive or clamp electrode, electrodes that are necessary to measure the difference in electrical potential between them and also between each arm and a third electrode connected to the left leg, which normally requires exposure of an area of the skin of said leg or foot.

The innovative solution proposed by the present invention is the use of conductive electrodes that are completely covered by each foot or by each hand, or that are enclosed within them.

We have found that the apparatus of the present invention reduces electrical interference and significantly increases the quality of the ECG signal by acquiring it by means of three or four dry conductive electrodes with two of which contact the sole of each foot so that each electrode remains totally covered by the respective foot (one of them optional), and with the other two electrodes they establish respective contact each of the hands, either grabbing them, holding them, touching them or leaning on them, so that the hands completely enclose or cover the conductive surface of each electrode.

The specific design of the device is that, in addition to each electrode being covered or enclosed by a foot or a hand, there is an immediate voltage follower to each of the three measuring electrodes (hands and left foot), that is, connected to it by a very short metallic conductor, which preferably should be covered in turn by the conductive surface of the electrode, so that there can be no capacitive coupling between this conductor and the electrical network or other conductor that has a non-zero electrical potential . It will then be enough to connect the outputs of each voltage follower to a multichannel differential amplifier to simultaneously obtain the three bipolar leads of the ECG. The use of a voltage follower on the electrode under the left foot allows the ECG to be obtained even if socks are worn.

The present invention allows simultaneous registration of the three standard bipolar leads of the ECG with high immunity to electrical interference and to do so in a quick, convenient and easy way for a person who does not have a specific training, for which it is enough to use only your hands and feet to establish contact with two electrodes, by grasping, holding, touching or leaning on them, without exposing any other part of your body and without removing your socks. The electrodes can be adapted to any flat or curved surface, provided they are covered by the respective limb when making contact with them. For added comfort, the person can be seated and the electrodes arranged in the armrests and footrests. To save time and obtain the ECG while a person is being weighed, the foot electrodes can be placed on the scale being used, even if it is not electronic, and the hand electrodes can be held one by each hand.

The electrocardiography apparatus, to obtain electrocardiograms (ECG), as indicated, is of the type that obtains in parallel the bipolar leads 1, 11 and 111 of the ECG. Specifically it comprises only three or four electrodes. Two will be manual electrodes, of size and shape to fit fully in each hand of the intended user, while the other two will be electrodes for the feet, surface and shape inferior to the sole of a foot to be able to contact the entire surface with the corresponding user foot. The first (third in the global computation) will be a left electrode, for that foot, and the second (fourth in the global computation) an optional right electrode, for the other. Conductive spheres are cited as an example of manual electrodes, and as an example of foot electrodes, conductive discs with or without a non-slip base.

The electrodes for the feet may change sides, if necessary, but this nomenclature is maintained because the medical practice performs the electrocardiograms taking as a reference the right leg and therefore is the one that will be connected to mass if necessary. However, the invention is not limited to that single orientation, and may be alternated if the practice is modified in the future OR in the case of patients with amputations, malformations, open wounds, plaster casts or any other reason that excessively prevents or hinders use The left foot for measurement.

The connection with the electronic system for obtaining and processing the ECG will be, from the manual electrodes and the left electrode, by means of two voltage followers, which will preferably be inside the corresponding electrode to protect it from interference. Instead, the optional right electrode will be connected to the ground of the electronic system.

The need to connect the right foot or leg to ground is determined by the design of the front stage of the differential amplifier used in the electronic system for obtaining and processing the ECG, as is known in the prior art.

The electronic system may comprise a multichannel differential amplifier and a digitizer, which may be placed in a first physical unit, and a digital processor, and means for the simultaneous storage and presentation of at least three analog signals, which may be placed in a second unit. Physics like a computer. If available in two physical units, a connection between them will be required, which may be wireless, or follow any of the available USB standards.

Description of the drawings. For a better understanding of the invention / the

following figures: Figure 1 is a diagram with the blocks of the proposed measurement method.

Figure 2A is a diagram of the manual lead electrodes, Figure 2B is a diagram of the left electrode, and Figure 2C is a diagram of the right electrode.

Figure 3 shows the bipolar leads 1, II and III of the ECG obtained for a standing person using the invention.

Figure 4 shows the voltage spectrum of branch 1 of the register shown in Figure 3, where the absence of significant peaks related to electrical interference caused by the power grid (at 50 Hz) or by fluorescent tubes ( at 100 Hz).

Figure 5 is a diagram with the blocks described in the preferred embodiment of the present invention.

Embodiments of the invention.

Next, an embodiment of the invention will be briefly described as an illustrative and non-limiting example thereof.

The constituent elements of the apparatus of the invention represented in the figures are:

A left conductor electrode 100, with which the subject establishes contact by the left foot, and another optional conductive right electrode 105, with which the right foot contacts.

A voltage follower amplifier 110 connected to the left electrode 100, whose output is connected by a cable 120 to one of the inputs of the multichannel differential amplifier 201 that is part of an electronic system 200.

A pair of manual electrodes 101 and 102 conductors with which the subject establishes simultaneous contact by touching each electrode with a different hand, either by supporting one hand on each electrode, either by grasping, or by holding each electrode with a different hand, such so that each electrode is completely enclosed or covered by the respective hand.

A pair of voltage followers 111 and 112, respectively connected to manual electrodes 101 and 102 and whose outputs are connected by respective cables 121 and 122 to one of the inputs of the multichannel differential amplifier 201 that is part of an electronic system 200.

Three cables 120, 121 and 122, one for each measuring electrode, which include conductors for the respective output voltages of the voltage followers, which are connected to the multichannel differential amplifier 210, and which can also include conductors for the supply voltages of these tension followers.

A cable of the right foot 123 that connects the right electrode 105 to the signal ground of the differential amplifier 201, if by design it requires said connection to function properly. Otherwise, a good ground connection of the other elements would be sufficient and the right electrode (105) and its wiring could be ignored.

An electronic system 200 for obtaining and processing the ECG that accepts signals from the three voltage followers 110, 111 and 112 connected to the measuring electrodes. To this end, in addition to the differential amplifier 201, this electronic system 200 includes the other necessary functions in a conventional electrocardiograph, such as a digitizer 202, a digital processor 203, and means for storage 204 and simultaneous presentation 205 of at least three signals. analog Said electronic system 200 can be constituted by a single physical unit or by several physical units electrically interconnected with or without wires.

In a preferred embodiment, the left and right electrodes 100 and 105 of Figure 2 can be two 5 cm diameter metal discs adhered to two discs of non-slip material that is deposited on a flat surface, such as the floor. The subject puts the left foot on the corresponding metal disk and the right foot on the other, so that it rests on each one with the front or with the back of the foot and completely covers it. It is not necessary that the feet are bare but may be covered with a breathable sock.

The metal disk in contact with the left foot is connected to a voltage follower 110 based on an operational amplifier housed inside the non-slip material and connected to a cable 120 that includes four conductors: the positive supply voltages

5 and negative for the voltage follower, the signal mass to which a polarization resistor of the voltage follower input is connected, and the output signal of this voltage follower. The initial section of the cable is housed inside the disc of non-slip material so that it can rest on the ground. The metal disk in

10 contact with the right foot is directly connected to the signal ground of the electronic system 200.

In this preferred embodiment, the manual electrodes 101 and 102 shown in Figure 2 are 4 cm hollow metal spheres

15 in diameter, which is a suitable size for said spheres

they are locked by the hands when an adult takes them. In case of

if the application is required in a child, the sphere will be smaller.

Within each sphere the respective tension followers 111 and 112 are housed, with their polarization resistance, and the cable 121 and 122

20 respectively emerges from a small opening made in the surface of the sphere. These cables 121 and 122 have a diameter of 3 mm, so that it passes well in the space between two fingers, having the same four conductors as the cable 120.

The electronic system 200 may consist of two physical units, 300 and 400. A first unit 300 includes the multichannel differential amplifier 201 and the digitizer 202, and is connected via a connection 210, with or without wires, to the second unit 400

which includes digital processor 203, storage media 30 204 and presentation media 205.

In one embodiment, connection 210 meets the USB standard, in any of its variants (USB 1.0, USB 2.0, USB 3.0, etc.). so that both the first unit 300 and the voltage followers 110, 111 and 112 receive power from two of the wires of said connection 210. The second unit 400 can be powered by batteries or from the power grid. This preferred embodiment has the advantage that the first unit 300 receives the power through the same connection 210 by means of which it communicates its signals and that it has been chosen for 2 m. Thus, the first unit 300 can be arranged on the same table where the second unit 400 is located, which in this preferred embodiment is a portable computer.

Figure 3 shows the bipolar leads 1, II and III of the ECG obtained in a person who was standing in an environment full of electronic devices, using this preferred embodiment with a laptop as a second unit 400, fed from the power grid. The absence of the most common electrical interference is shown in Figure 4, where no peaks are seen in the 50 Hz frequency or in their harmonics.

Figure 5 shows the block diagram of this preferred embodiment.

Once the invention has been sufficiently described, as well as a preferred embodiment, it should only be added that it is possible to make modifications in its constitution and materials used without departing from the scope of the invention, defined in the following

claims.

Claims (1)

1-Electrocardiography apparatus, of the type that obtains in parallel the bipolar leads 1, II and III of the electrocardiogram (ECG), which It comprises only three or four electrodes and characterized in that the tension followers (110,111,112) are located within the corresponding electrodes, so that they are covered by the conductive surface of the electrode.