EE05881B1 - Method and device for determining physiological parameters of a body organ located in a body part with a convex surface - Google Patents

Abstract

The subject of the invention is a method and apparatus for determining physiological parameters of a body organ within a convex shaped body part placed into a coil with toroidal core that follows the convex shape of the body from 1/10 to 1/1 of the full extent of the convex, inducing alternating current response signal and determining the physiological parameters of the body organ from the response signal.

Description

 Technical field

The invention belongs to the field of medical technology, more specifically to technical means for monitoring and diagnosing the quality of blood circulation and the supply of oxygen-rich blood to living tissues and related organs, in particular the heart, lungs and blood vessels, and the entire cardiovascular and pulmonary system as a whole. The information is obtained using methods of electrical and magnetic induction.

State of the art

The interest in measuring and assessing health indicators related to the functioning of the cardiovascular system is justified due to their prevalent role in the volume and cost of treatment procedures. At the same time, the importance of monitoring breathing and the functioning of the entire pulmonary system is growing, especially due to the global spread of the coronavirus (SARS-CoV, Severe Acute Respiratory Syndrome Corona Virus). Lung problems have become a serious challenge both during the acute period of the disease and due to the development of problematic complications during follow-up treatment. The joint approach to the cardiovascular and pulmonary systems (cardiopulmonary system) is justified both based on the needs of practical medicine and physiologically - the meaning and essence of the existence of both systems lies in ensuring the oxygen supply of tissues for metabolism, which is the mechanism for ensuring the energetic need of life processes.

The use of electrical bioimpedance in medical diagnostics is well known (Bioimpedance and Bioelectricity Basics by Orjan G. Martinsen and Sverre Grimnes, 3rd ed., 2014). The use of electrical bioimpedance in invasive pacemakers is known, see Min et al., US patent 6975903 (patent date 13.12.2005) and Min et al., US patent 6885892 (patent date 26.04.2005), Kink et al., US patent 7894900B2 (patent date 22.02.2011) for the assessment of lung function (respiratory rate and volume and ensuring blood oxygen content) and cardiac function (stroke rate and volume, blood filling rate and the heart's own energy balance) and for rhythm control. The impedance is determined by contact measurement inside the body and/or in the heart (invasive measurement).

Invasive measurement is accurate, but it is cumbersome and expensive, and far from always feasible. Complications occur (bleeding, inflammation, infections) and technical failures are possible that are difficult to eliminate, since the equipment is located either partially or completely inside the body.

Electromagnetic fields have also been used for similar purposes in the past, for example in electrical and magnetic impedance tomography (EIT and MIT). In the case of MIT, solenoidal and planar coils (poles) have been used to create the magnetic field, see Lu Ma and M. Soleimani, “Magnetic induction tomography methods and applications: a review“, Meas. Sci. Technol. 28 (2017) 072001 and Dan Yang et al, "Cardiopulmonary Signal Detection Based on Magnetic Induction", Journal of Sensors, vol. 2017, Article ID 1752560, 9 pages, 2017. https://doi.org/10.1155/2017/1752560. However, these methods do not allow generating an electromagnetic field of a suitable shape to induce a directed electric current in an organ inside the body or a body part, e.g. an electric current passing through a blood vessel.

It is known from the state of the art that, for example, the highest density of the electromagnetic field generated by a solenoid placed around a finger or arm is precisely on the surface of the finger or arm (Sun J et al. “An experimental study of pulse wave measurements with magnetic induction phase shift method. Technol Health Care. 2018;26(S1):157-167. doi: 10.3233/THC-174526 and D Teichmann et al. “MonitoRing – Magnetic induction measurement at your fingertip”, 2013 J. Phys.: Conf. Ser. 434 012084), whereas the electromagnetic field generated in the organ inside the finger or arm – the blood vessel – is local and marginal. This does not allow for the induction of an electric current with the intensity and direction required for vascular diagnostics.

It is known from the state of the art that in the case of a planar coil, the magnetic flux inside the body is strongest below the planar coil (on the surface of the body) and decreases exponentially with increasing depth. A circular electric current, or eddy current, is induced by this magnetic flux in the material below the planar coil. The current density is strongest directly below the coil. This current can be used to measure the electrical impedance of the material below the planar coil (R. Robaina et al., “Planar coil-based differential electromagnetic sensor with null-offset”, Sensors and Actuators A: Physical, Vol.164, Issues 1–2, 2010, pp.15-21, https://doi.org/10.1016/j.sna.2010.09.008), but not the impedance of the electric current flowing through the blood vessel.

The essence of the invention

The present invention provides a solution for obtaining important physiological indicators in a non-invasive way, using an extracorporeal technique for measuring the transfer function expressed through the relationship between electrical voltage and current inside the body. The electric current required for measurement is generated by the induced electromotive force (emf) at a desired location in the human body under the influence of an alternating electromagnetic field. In this case, both components of the electromagnetic field – both the electric and magnetic fields – can be used either together or separately.

An electromotive force is induced in the living tissues of organs through an electromagnetic field, and the electric currents and voltages generated by this force are measured, through the relationships between which transfer functions are expressed, which characterize the objects being measured (organs, their components and tissues, including individual cells and the structures composed of them). The best-known transfer functions are the quotients of electric voltages and currents, which are expressed either in the form of electrical bioimpedance (with a physical dimension of Ohm), or its inverse, electrical bio-admittance (with a physical dimension of Siemens). At the same time, informative relationships between currents or certain voltages without physical dimensions are used.

The main applications of the invention are related to the recording of parameters (volume, rhythm and velocity and specific time points and corresponding levels and their relationships) related to the blood flow and blood pressure curves of the arterial system and its parts, including the aorta, arteries, arterioles and capillaries. This also includes noting the characteristics and movement indicators (location, volume and velocity and their variation) of the pulse wave generated by the heart and highlighting the indicators of lung function efficiency (respiratory frequency and tidal volume, mean minute volume of respiration, oxygen transfer efficiency). The invention relates to both a method based on the measurement of electrical bioimpedance and admittance and an apparatus for performing/implementing this method.

The inventive method for determining the physiological parameters of a body organ located on a body part with a curved surface includes the following steps: an electromagnet with a toroidal core is placed on the body part, the shape of which follows the curved surface of the body part by 1/10 to 1/1 of the full extent of the curved surface, an alternating electric current is induced along the body part with the curved surface by the electromagnet, and the voltage caused by the alternating electric current is measured.

response signal and the physiological parameters of the body organ are determined from the response signal. Physiological parameters can be parameters of the lung and cardiovascular system. Known solutions are used to generate the electromagnet current (excitation signal) and measure the parameters of the response signal. Known methods are also used to find physiological parameters from the measurement results.

According to one embodiment, the method is characterized in that two electrically connected capacitive or galvanic electrodes are used to close the internal circuit of the body, placed on either side of an electromagnet with a toroidal core. For example, two electrically connected electrodes are used to disconnect anatomical parts from the closed circuit. For example, two electrodes are electrically connected through a shorting ammeter or an equivalent electronic circuit, e.g. a current-to-voltage converter, to measure the current strength of the response signal.

Preferably, the current strength of the response signal is measured with a toroidal core current transformer.

According to one embodiment, the circuit is closed through an electrically conductive belt placed around the body. According to another embodiment, the circuit inside the body is closed through an electrically conductive aid. Such an aid can be a sports tool, e.g. a bicycle or motorcycle handlebar, exercise and rehabilitation equipment handles, a steering wheel of a car or other means of transport. According to another embodiment, the circuit inside the body is closed through an electrically conductive element integrated into an article of clothing.

According to another embodiment, the circuit is closed by a connection device, through which the hands are connected to each other capacitively, magnetically, optically or via electromagnetic near-field communication. The device according to the invention for determining the physiological parameters of a body organ located on a body part with a curved surface comprises an electromagnet with a toroidal core, the shape of which follows the curved surface of the body part to an extent of 1/10 to 1/1 of the curved surface, an alternating electric current generator and a means for measuring and processing the response signal.

According to one embodiment, a toroidal core electromagnet has a coil spirally wound around the core and is connected to an alternating current generator.

In one embodiment, the device further comprises means for blocking the electric current induced by the electromagnet and passing through the body. For example, the means is an electrically conductive component connecting the two hands together, such as a metal object. The means may be an electrically conductive component connecting the hand and the body. The means may be a belt placed around the body or a circular part of the body.

According to one embodiment, the measuring and processing means comprises a current transformer for measuring the response signal.

Preferably, the device includes an ammeter for measuring the response signal in the form of an electric current. The device may include a voltmeter for measuring the response signal in the form of an electric voltage.

The response signal measuring and processing means comprises an electronic device for obtaining physiological parameters from the results of the measurement of the induced current and the response signal. The corresponding relationships between the electrical response signal and the physiological parameters are known.

List of drawings

Figure 1A is a schematic diagram of a sensor with a toroidal core according to one embodiment of the invention, and Figure 1B is the same sensor.

Figures 2A and 2B show toroidal core sensors according to second and third embodiments of the invention.

Figure 3A shows the shape and direction of the magnetic field and the direction of the induced current in the case of a toroidal core of the invention placed on the wrist, and Figure 3B demonstrates the generation of a magnetic field by the toroidal core and its induced current in a conductive material, e.g. a blood vessel.

Figure 4A demonstrates a measurement with a current loop closed to the body via a belt connected galvanically or capacitively.

Figure 4B demonstrates a measurement with a current loop closed through the connected hands galvanically and through the capacitance between the hands.

Fig. 4C demonstrates a measurement with a current loop closed by an electrically conductive means between the hands.

Fig. 4D demonstrates a measurement with a current loop closed by a coupling device placed between the hands, through which electrical connection occurs through electrical conductivity, capacitive or inductive coupling, and electromagnetic field.

Figure 5 shows a measured signal curve containing both pulmonary and cardiac components. The curve demonstrates the measurement result obtained with the applications shown in Figures 4A, 4B, 4C and 4D.

Figure 6A shows a sensor with a toroidal core placed on the wrist together with a measuring device, whereby electrodes placed on both sides of the sensor are used to close the current loop. Figure 6B shows a photograph of a test solution of the sensor diagram shown in Figure 6A.

Figure 7 shows a measured heart rate curve, the slow change in amplitude of which is due to breathing.

Examples of carrying out the invention

A sensor according to the invention according to a first embodiment is shown in Figure 1A. The sensor is mounted around a body part, e.g. an arm 1, wherein the sensor comprises a toroidal core 2, on which a wound coil 3 is connected to an alternating current generator 4. Figure 1B is a photograph of the same device, showing the toroidal core 2, coil 3 and alternating current generator 4.

Figures 2A and 2B show alternative examples of sensors with an open magnetic circuit. The toroidal core 2 does not have to be magnetically closed, but can be only a certain part of the toroid, e.g. 1/2 to 1/8 of the toroid.

Figure 3A shows the shape and direction of the magnetic field and the direction of the induced current in the case of a toroidal core according to the invention placed on the wrist. In the core 2, the magnetizing current im passing through the coil 3 creates a magnetic flux 5, which induces an electric current ii, the magnitude of which depends on the electrical resistance in the direction of the arm. The induced electric current ii is directed mainly through the blood vessels, both due to the corresponding direction of the magnetic field and because the electrical conductivity of the blood is several times higher than that of the surrounding living tissues.

Figure 3B shows the creation of a magnetic field in a toroidal core and its induced current in a conductive material, e.g. a blood vessel. The physical principle of electromagnetic induction is derived from Faraday's law. An electric current in a coil 3 with a number of turns N creates a magnetic flux density B in the toroidal core 5, which in a closed electrical circuit

induces an electric current of N times the strength in the direction through the opening of the toroidal core, as the electric wire 6 is placed, which can be e.g. a blood vessel. The process is reversible, the same circuit is suitable for measuring the current through the opening of the toroidal core, e.g. the current flowing in a blood vessel. A current transformer is formed, which can be used in the body, e.g. for measuring the strength of the electric current induced in the arm and flowing along the blood vessel.

Electric current can only flow in a closed circuit. Although the human circulatory system is a closed system with arterial and venous vasculature, it is difficult to induce a current uniformly throughout the body. One solution is to artificially close the circulatory system in the section of interest, for example with additional electrodes, see Figures 6A and 6B. The additional electrodes are preferably superficial and non-invasive, for example by galvanic or capacitive connection to the skin surface. Figure 7 shows a curve showing the pulsation of blood flow due to cardiac activity and its volume and character, measured with the prototype device shown in Figures 6A and 6B, respectively. The slow undulation of the curve shows the effect of pulmonary respiration on cardiac activity. However, in principle, invasive electrodes, for example thin needle electrodes (micrometer-sized) inserted into the skin to a depth of less than a millimeter, can also be used. In certain cases, it may be appropriate to use invasive methods, in which microelectrodes are inserted into a blood vessel at a selected location.

An alternative way of closing the circuit is shown in Figure 4A. The induced current ii is closed by the belt 7 connecting the hand and the body through the electrical conductivity and electrical capacitance between the hand and the belt body. In this case, a closed circuit is obtained, which includes the heart-lung-blood vessels.

Another alternative way of closing the circuit is shown in Figure 4B, where the circuit is closed through the electrical conductivity and capacitance between the connected arms 8.

A third alternative circuit closure option is shown in Figure 4C, where the circuit is closed via an electrically conductive means 9 connecting the hand, which is a tube, bar, lever, steering wheel or other means made of electrically conductive material, e.g. a sports equipment, e.g. ski or walking poles, a bicycle or motorcycle handlebar, handles of training and rehabilitation equipment, a steering wheel of a car or other means of transport.

A fourth alternative circuit closure option is shown in Figure 4D, where the induced current loop is galvanically or capacitively connected to the closed arms

by means 10 and 11, which are interconnected by a connecting device 12, through which the circuit is closed. The closing is carried out galvanically (via a wire, conductor, cable, tape, braid or other electrically conductive means), capacitively (via a capacitor or other structure having electrical capacitance), magnetically (via a transformer or other structure enabling inductive coupling) or by means of a high-frequency electromagnetic near field, including via a radio transceiver (transmitterreceiver) through air or other dielectric material, and also through optical coupling.

Figure 5 shows the curve corresponding to lung respiration (large amplitude slow wave) and the pulsation caused by cardiac activity (small amplitude fast spiking) on top of it. The curve is obtained from the applications presented in Figures 4A, 4B, 4C and 4D. The component corresponding to respiration prevails, but the amplitude of the component corresponding to cardiac activity depends largely on the specific solution (largest in the case of Figure 4D).

Figure 6A shows a solution where the circuit is closed locally in the wrist area by means of two additional electrodes 13 and 14 made of conductive material, the induced current ii is closed through their mutual electrical connection 15, whereby the electrodes have contact with the body through galvanic electrical conductivity and electrical capacitance between the electrodes and the body.

This method of closing the circuit provides the possibility of electrically connecting the forearm, upper arm, and shoulder and their parts to each other (for example, the part of the arm from the wrist to a designated point, which can extend from a few centimeters to the elbow, see Fig. 6B) and also connecting other parts of the body for the purpose of closing the electrical current.

Figure 6B is a photograph of an example of use, which is shown in Figure 6A. A toroidal sensor coil 3 is attached to the wrist, which induces an electric current along the arm. Two gold electrodes 13 and 14 are added, between which an electrical wire connection 15 closes the circuit. With the help of an electronic circuit 16 containing an alternating current generator and a detector, we can measure the volume and nature of the blood flow pulsation in the wrist between the electrodes 14 and 15.

Electrically connected electrodes may also be used to disconnect anatomical parts from a closed circuit by shorting the electrodes.

Claims (20)

1. A method for determining the physiological parameters of a body organ located on a body part with a curved surface, according to which an electromagnetic field is induced in the body organ with an alternating current excitation electromagnet, and the response signal corresponding to the electromagnetic field on the body organ is measured with a measuring instrument, and the physiological parameters of the body organ are determined from the response signal, characterized in that an electromagnet with a toroidal core is placed on the body part, the shape of which follows the curved surface of the body part by 1/10 to 1/1 of the full extent of the curved surface, whereby an alternating electric current is induced in a closed circuit along the body part with a curved surface by the electromagnet. 2. The method according to claim 1, characterized in that two electrically connected capacitive or galvanic electrodes placed on either side of an electromagnet with a toroidal core are used to close the circuit within the body part. 3. The method according to claim 2, characterized in that the anatomical parts of the body part are separated from the closed circuit by means of two electrically connected electrodes. 4. The method according to claims 2 to 3, characterized in that the two electrodes are electrically connected through a short-circuiting ammeter or an equivalent electronic circuit for measuring the current strength of the response signal. 5. The method according to claim 4, characterized in that the two electrodes are electrically connected through a short-circuiting current-voltage converter. 6. The method according to claims 1 to 5, characterized in that the current strength of the response signal is measured with a current transformer with a toroidal core. 7. The method according to claims 1 to 6, characterized in that the circuit within the body part is closed by means of an electrically conductive belt placed around the body. 8. The method according to claims 1 to 6, characterized in that the internal body circuit is closed through an electrically conductive means. 9. The method according to claim 8, characterized in that the device is a sports device, a bicycle or motorcycle handlebar, handles of training and rehabilitation equipment, a steering wheel of a car or other means of transportation. 10. The method according to claim 8, characterized in that the internal body circuit is closed through an electrically conductive element integrated into the garment. 11. The method according to claims 1 and 2, characterized in that the circuit is closed by a connection device through which the connection of the hands is carried out capacitively, magnetically, optically or via electromagnetic near-field communication. 12. A device for determining the physiological parameters of a body organ located in a body part with a curved surface by the method presented in point 1, comprising an electromagnet with alternating current excitation connected to an alternating current generator for inducing an electromagnetic field in the body organ and a measuring device for measuring the response signal corresponding to the electromagnetic field on the body organ and for determining the physiological parameters of the body organ from the response signal, characterized in that the electromagnet is an electromagnet with a toroidal core, the shape of which follows the curved surface of the body part by 1/10 to 1/1 of the full extent of the curved surface, and a coil is spirally wound on the core of the electromagnet, which is connected to an alternating current generator and a means for closing the electric current induced by the electromagnet and passing through the body. 13. The device according to claim 12, characterized in that the body part is a hand. 14. The device according to claim 13, characterized in that the means for closing the electric current passing through the body is an electrically conductive component connecting the two hands together. 15. The device according to claim 14, characterized in that the means is a metal object. 16. The device according to claim 13, characterized in that the means for closing the electrical current passing through the body is an electrically conductive component connecting the hand and the body. 17. A device according to claim 16, characterized in that the means is a belt placed around the body or a rounded body part. 18. The device according to claims 12 to 17, characterized in that the means for measuring and processing the response signal comprises a current transformer for measuring the response signal. 19. Device according to claims 12 to 18, characterized in that the means for measuring the response signal is an ammeter. 20. The device according to claims 12 to 18, characterized in that the means for measuring the response signal is a voltmeter.