CZ36880U1 - A system for measuring the speed of the aortic pulse wave and monitoring the change of the ABI index in a supine patient - Google Patents

Description

In the registration procedure, the Industrial Property Office does not determine whether the subject of the utility model meets the conditions of eligibility for protection according to § 1 of Act. E. 478/1992 Coll.

A system for measuring the speed of the aortic pulse wave and monitoring the change of the ABI index in a supine patient

Field of technology

The presented technical solution relates to a system that enables non-invasive monitoring of hemodynamic parameters related to the progression of atherosclerosis, and specifically relates to a system for measuring the speed of the aortic pulse wave and for monitoring changes in the ankle pressure index, i.e. ABI index, in the supine patient.

Current state of the art

In the current state of the art, there are solutions dealing with measuring the speed of the aortic pulse wave and the ABI index (from the English Ankle-Brachial index, i.e. the index of ankle pressures or the ankle-arm index), which gives a ratio of the magnitude of the arterial pressures on the wrists and ankles . In the patent literature, these are e.g. documents CN 104 970 781 B, US 2010 0 292 586 A1, TW 516 951 B, US 9 854 976 B2, EP 1 500 910 B1 or US 10 390 716 B2, while these patents are based on the modification of known methods, such as the ultrasound or oscillometric method, or on the use of photoplethysmographs.

There are also a number of professional publications that describe measurement changes depending on the physiological characteristics of a person or depending on various pathologies and which refer to the relevant measuring devices. Examples include the article A new device for automatic measurements of arterial stiffness and ankle-brachial index (Cortez-Cooper, 2003), which describes the automation of existing methods such as applanation tonometry and others, or the articles Measurement and Interpretation of the Ankle-Brachial Index (Aboyans, 2012), Pitfalls in the ankle-brachial index and brachial-ankle pulse wave velocity (Ato, 2018), Comparison of aortic pulse wave velocity measured by three techniques: Complior, SphygmoCor and Arteriograph (Rajzer, 2008) or Novel Methods for Pulse Wave Velocity Measurement (Pereira, 2015).

However, it would be advisable to come up with a solution for a new system that would be characterized by a simple design and that would allow non-invasive or even non-contact measurement of hemodynamic parameters related to the progression of atherosclerosis. Above all, it would be desirable to come up with a solution that would allow non-invasive measurement of the speed of the aortic pulse wave with respect to the patient's breathing. At the same time, the desired solution should enable the monitoring of the change in the ABI index, whereby, for example, a low value of the ABI index may indicate a narrowing or blockage of the arteries in the legs.

The essence of the technical solution

To a certain extent, the above-mentioned shortcomings are eliminated by the system for measuring the speed of the aortic pulse wave and monitoring the change in the ABI index in a lying patient. The essence of the system according to the presented technical solution is that it includes at least one first vibration sensor for placement in the lateral line in the heart region, at least one second vibration sensor for placement in the lateral line in the lumbar region, a control unit connected to at least one first vibration sensor and at least one other vibration sensor and a computing module.

The main advantage of the presented technical solution is that it enables non-invasive and also non-contact measurement of pulse wave speed. The measurement itself is comfortable and unobtrusive for the patient, as the sensors do not have to come into direct contact with his body. The system also enables monitoring of the change in the ABI index, which can be used, for example, in cases where the patient lies in bed for several days or longer.

- 1 CZ 36880 U1

The computing module is advantageously adapted for calculating the pulse wave run-off time based on data from at least one first vibration sensor and at least one second vibration sensor and for calculating the speed of the pulse wave. The rate of progression of atherosclerosis can be inferred from the values of the pulse wave speed. In addition, the pulse wave's decay time generally fluctuates with how the patient breathes, because intrathoracic pressure changes during breathing, and blood pressure also changes with this pressure change. For reliable measurement of the pulse wave speed, it is therefore determined on the basis of the data from the sensors when the patient inhaled and when he exhaled, and the calculation module is adapted to determine different pulse wave decay times during exhalation and inhalation of the patient.

The system further advantageously includes at least one analog-to-digital converter connected to at least one first vibration sensor and to at least one second vibration sensor. Thanks to the analog-to-digital converter, the analog signal from the vibration sensors can be converted into a digital signal, which can already be processed by the control unit or sent to another part of the system, e.g. via a wireless connection to a remote server.

The first vibration sensor and the second vibration sensor are preferably piezoelectric sensors. These sensors do not have to be attached to the patient, and thus enable non-contact measurements. At the same time, they are characterized by sufficient sensitivity to record the relevant vibrations.

The first vibration sensor and the second vibration sensor may be three-axis gyroscopes adapted to be attached to the patient's body. These sensors can be glued to the patient's body, for example.

The system further advantageously includes a remote server and the control unit includes a communication module, wherein the remote server is communicatively connected to the control unit by means of a communication module. A remote server (the so-called cloud) can be used not only to store or display measured data or calculated values, but also to perform all the necessary calculations, primarily to calculate the pulse wave speed.

The communication module is preferably a Wi-Fi module, and the communication connection between the control unit and the remote server is wireless. This eliminates the need for cabling to connect to a remote server.

The computing module is preferably part of the remote server. In this embodiment, it is not necessary to have a very powerful and therefore expensive control unit, because the control unit does not perform a detailed analysis of the measured signal, but sends this signal to a remote server for further processing (i.e. performing calculations). A remote server can also provide a more user-friendly and clear output.

Clarification of drawings

The essence of the technical solution is further clarified on examples of its implementation, which are described using the attached drawings, where on:

Fig. 1 is a schematic representation of the arrangement of the system according to the presented technical solution in the first exemplary embodiment with a simplified representation of the patient on the bed.

Examples of implementing a technical solution

The technical solution will be further explained on examples of implementation with reference to the relevant drawings.

The subject of the presented technical solution is a system for measuring the velocity of the pulse wave of the aorta and monitoring the change in the ABI index in a lying patient 9, while this system in the first exemplary embodiment includes at least one first vibration sensor 1 for placement in the lateral line in the region of the heart, at least one second sensor 2 vibrations for placement in the lateral line in the lumbar region, control

- 2 CZ 36880 U1 unit 3, computing module 4 and remote server 6. In the first exemplary embodiment of the system, the computing module 4 is part of the remote server 6. For greater clarity and better logical continuity of the text, the layout of the system and implementation will first be described in detail within the framework of the exemplary implementations its individual components and then the processing of data by computing module 4 will be described in more detail.

In the first exemplary embodiment, as shown schematically in Fig. 1, the system includes a group of first vibration sensors 1 and a group of second vibration sensors 2, wherein the group of first vibration sensors 1 includes one or more first vibration sensors 1 and the group of second vibration sensors 2 includes one or more second sensors 2 vibrations.

The first group of vibration sensors 1 is located in the lateral line in the region of the heart and is adapted to record a signal to determine the mechanical trigger of contraction of the heart muscle, which indicates the emergence of a pulse wave of the aorta. The aortic pulse wave corresponds to one heartbeat, during which blood is pushed from the heart into the aorta and then into individual arteries and other vessels. The ejection and transport of blood are associated with an increase in blood pressure in the vessels, which decreases in the second phase of the cardiac cycle. The peak of the pulse wave corresponds to the highest value of the pressure that is reached, while the minimum of the pulse wave corresponds to the lowest value of the blood pressure. During the heart pulse, mechanical excitations occur, i.e. vibrations that spread through the aorta and individual vessels. The group of first vibration sensors 1 is further adapted to record mechanical vibrations related to the patient's 9 breathing, whereby it can be determined from the signal obtained by the first vibration sensors 1 when the patient inhaled and when he exhaled.

The group of second sensors 2 vibrations is located in the lateral line in the lumbar region and is adapted to detect the pulse wave of the aorta, i.e. for the detection of a mechanical stimulus that arrives at the group of second sensors 2 vibrations after a certain time from the contraction of the heart muscle, more precisely from the moment, when the mechanical trigger of contraction of the heart muscle is detected using the first sensors 1 vibrations. This time is also called the pulse wave run-up time and is a time parameter that can be used to determine the speed of the pulse wave, knowing the mutual distance of the first vibration sensor group 1 and the second vibration sensor group 2. These calculations are performed by the calculation module 4, as will be explained below.

In the first exemplary embodiment of vibration sensors, the first vibration sensors 1 and the second vibration sensors 2 are piezoelectric sensors, whereby the measured mechanical excitation causes deformation of the crystal in the sensor, and thus generates an electrical voltage, i.e. an analog signal corresponding to the vibrations. In the first exemplary embodiment, the first vibration sensors 1 and the second vibration sensors 2 are integrated into the bed 8 itself, on which the patient 9 lies, e.g. they are stored under the mattress. This ensures non-contact measurement, as the first vibration sensors 1 and the second vibration sensors 2 are not in direct contact with the body of the patient 9. Alternatively, the first vibration sensors 1 and the second vibration sensors 2 can be placed on the bed 8 and the patient 9 is lying on them, but they do not have to be directly attached to the patient's body 9. Alternatively, the first vibration sensors 1 and the second vibration sensors 2 can be attached directly to the body of the lying patient 9, specifically to his back. Alternatively, the first vibration sensors 1 and the second vibration sensors 2 can be attached to another part of the patient's body, eg the first vibration sensors 1 to his chest and the second vibration sensors 2 to his abdomen. Alternatively, the first vibration sensors 1 or the second vibration sensors 2 are other types of sensors, e.g., strain gauge sensors or three-axis gyroscopes, and if three-axis gyroscopes are used, these three-axis gyroscopes must be fixed, e.g., glued, to the patient's body 9. The sensing frequency of the first sensors 1 vibration and second sensors 2 vibration is preferably at least 200 Hz.

Regardless of whether the design of the vibration sensors is any of the options described above, for the proper functioning of the system, the first group of 1 vibration sensors must be located in the lateral line in the heart area during the measurement, and the second group of 2 vibration sensors must be located in the lateral line in the lumbar area during the measurement , i.e. in the area below the hips. The lateral line is an imaginary line that passes through the lying body of the patient 9 between his feet and his head, or is parallel to this line and passes above or below the patient 9. At the same time, the vertical position of this lateral line is not essential, as well as

- 3 CZ 36880 U1 the exact vertical position of the first vibration sensors 1 and the second vibration sensors 2 relative to this lateral line is not essential, i.e. whether the first vibration sensors 1 and the second vibration sensors 2 are located under the mattress, under the patient, on his back or chest, or on the stomach. Using the lateral line, the position of individual parts of the body can be described and, for example, the area of the head, the area of the lower limbs, etc. can be defined. For the purposes of this application, the area of the heart in the lateral line and the lumbar area in the lateral line are defined in this way.

A group of first vibration sensors 1 and a group of second vibration sensors 2 is connected to a control unit 3. In its first exemplary embodiment, the control unit 3 includes an analog-to-digital converter 5 for converting the analog, typically voltage, signal from the first vibration sensors 1 and the second vibration sensors 2 to digital signal and also the communication module 7 ensuring the communication connection of the control unit 3 with the remote server 6, the so-called cloud, where the digital data is sent for further processing. The analog-to-digital converter is connected to a group of first vibration sensors 1 and to a group of second vibration sensors 2, however, alternatively, the system may also include multiple analog-to-digital converters 5 that are connected to the sensors individually. One or more analog-to-digital converters 5 also do not have to be a direct part of the control unit 3, but can be connected before the control unit 3, i.e. at the input of the control unit 3. The system can also include one or more amplifiers connected at the output of the first sensors 1 of vibrations and/ or other vibration sensors 2 and at the input of the analog-to-digital converter 5 for amplifying the measured signal. The system may also include multiple control units 3, e.g. such that each of the first vibration sensors 1 or of the second vibration sensors 2 has its own control unit 3.

In the first exemplary embodiment, the communication module 7 is realized as a Wi-Fi module, and the control unit 3 is thus connected to the remote server 6 wirelessly via Wi-Fi technology. The communication connection between the control unit 3 and the remote server 6 can alternatively also be implemented differently, e.g. using another wireless technology, possibly using a cable, e.g. using an Ethernet network cable.

In the first exemplary embodiment of the system according to the presented technical solution, the remote server 6 includes a calculation module 4 for performing the necessary calculations, especially for determining the speed of the pulse wave. To determine the speed of the pulse wave, the digital signal is sent from the control unit 3 to the remote server 6 and is processed there by the computing module 4, while the method of data processing and also the necessary calibration will be described in more detail below. The resulting information is displayed to the user, for example, on the website, computer, mobile phone or other suitable device. In an alternative exemplary embodiment, the system also includes a remote server 6, on which it is possible to store or display measured data, however, in this embodiment, the calculation module 4 is part of the control unit 3. This means that the calculations take place directly in the control unit 3 connected to the sensors, and not on the remote server 6. In another alternative embodiment, the computing module 4 is also part of the control unit 3, whereby the system instead of the remote server 6 includes a display for displaying the measured signal and the resulting parameters. This display can be arranged, for example, on the outside of the bed 8. In such an embodiment, the communication module 7 ensures communication with the display.

In the following section, data processing by the calculation module 4 will be described, which is essentially the same in all the above-mentioned exemplary embodiments, i.e. whether the calculations take place on the remote server 6 or directly in the control unit 3.

The calculation module 4 is adapted to determine the mechanical trigger of the contraction of the heart muscle, which indicates the formation of a pulse wave of the aorta, based on the signal from the first sensors 1 of vibrations. The determination of the mechanical trigger of contraction of the heart muscle is carried out by the ballistocardiography method known from the article Application of mechanical trigger for unobtrusive detection of respiratory disorders from body recoil micro-movements (Cimr, 2021), i.e. directly from the measured data, without the need to use an electrocardiograph. Specifically, the mechanical trigger of heart muscle contraction is determined as the local maximum of the so-called monitoring function, which is obtained on the basis of the Euclidean arc length, i.e. on the basis of an invariant calculated from the measured data. This is how it is intended

- 4 CZ 36880 U1 mechanical trigger of heart muscle contraction for each heartbeat, i.e. all local maxima of the monitoring function are detected. The measured data are filtered during processing using the moving average method.

The calculation module 4 is further adapted to calculate the speed of the pulse wave of the aorta, and to calculate the absolute value of the speed of the pulse wave, it is first necessary to measure the distance between the first sensors 1 of vibrations and the second sensors of 2 vibrations. Furthermore, for calculating the speed of the pulse wave, the so-called pulse wave run-up time is determined by the calculation module 4, as the time difference between the detection of the mechanical trigger of the contraction of the heart muscle by the first sensor 1 vibration and the detection of the pulse wave by the second sensor 2 vibrations. The speed of the pulse wave is subsequently obtained as the ratio of the specified time difference and the distance value of the first sensors 1 vibration and the second sensors 2 vibrations. From the value of the pulse wave velocity, it is possible to infer the rate of progression of atherosclerosis, while in practice it is generally true that a higher value of the pulse wave velocity indicates a higher risk and a higher rate of progression of atherosclerosis. However, the pulse wave decay time fluctuates with how the patient 9 breathes, because intrathoracic pressure changes during breathing, and blood pressure also changes with this pressure change. For reliable measurement of the pulse wave speed, based on the data from the first vibration sensors 1, it is therefore determined when the patient 9 inhaled and when he exhaled, and the calculation module 4 determines the different deceleration times during exhalation and during inhalation of the patient 9. Determination of inhalation and exhalation is carried out by tracking the periodic rises and falls of the moving average smoothed signal over a 1.5 s window corresponding to respiration. For the proper functioning of the system, its calibration is carried out as follows.

The calibration consists in the fact that the patient 9 first lies still for five minutes with his legs stretched out on the bed 8 and the first vibration sensors 1 and the second vibration sensors 2 perform the measurements described above. After that, patient 9's pressure is measured with a tonometer on the arm and leg. Subsequently, the legs of the patient 9 are supported by a mat (e.g. a box) with a defined height and then the patient 9 lies still for five minutes again, but this time with the legs supported by the mat. Finally, patient 9 has his blood pressure measured again with a tonometer on his arm and leg. In this way, data corresponding to four different pulse wave decays are obtained for four different cases - inhaling with unsupported legs, exhaling with unsupported legs, inhaling with supported legs and exhaling with supported legs. From the height of the feet, it is possible to determine the change in hydrostatic pressure, which is directly related to the change in intrathoracic pressure, and therefore also to the change in blood pressure in the upper and lower limbs. During calibration, the distance of the first sensor group of 1 vibration and the second sensor group of 2 vibrations is also measured, as mentioned above.

In addition to measuring the pulse wave speed, the system also enables, thanks to calibration, the monitoring of the absolute value of blood pressure at a constant position of the patient 9, as well as the monitoring of changes in the ABI index. The monitoring of the change in the ABI index is specifically performed by calculating the first value as the difference in the pulse wave deceleration in the case of inhaling with supported legs and inhaling with unsupported legs, and then the second value as the difference in the deceleration of the pulse wave in the case of exhaling with supported feet and exhaling with unsupported legs . In the event that patient 9, who may be in bed for days, is re-suppressed in the future, we can monitor whether these two values have changed. If so, it can be said that the ABI index has changed.

Claims (8)

1. A system for measuring the speed of the aortic pulse wave and monitoring the change in the index of ankle pressures, i.e. ABI index, in a lying patient (9), characterized in that it includes at least one first vibration sensor (1) for placement in the lateral line in the heart region, at least one second vibration sensor (2) for placement in the lateral line in the lumbar region, a control unit (3) connected to at least one first vibration sensor (1) and to at least one second vibration sensor (2) and a computing module (4). 2. The system according to claim 1, characterized in that the computing module (4) is adapted to calculate the pulse wave run-up time based on data from at least one first vibration sensor (1) and at least one second vibration sensor (2) and to calculate the speed pulse waves. 3. The system according to any one of the preceding claims 1 and 2, characterized in that it further comprises at least one analog-to-digital converter (5) connected to at least one first vibration sensor (1) and to at least one second vibration sensor (2). 4. The system according to any one of the preceding claims 1 to 3, characterized in that the first vibration sensor (1) and the second vibration sensor (2) are piezoelectric sensors. 5. The system according to any one of the preceding claims 1 to 3, characterized in that the first vibration sensor (1) and the second vibration sensor (2) are three-axis gyroscopes adapted to be attached to the patient's body (9). 6. The system according to any one of the preceding claims 1 to 5, characterized in that the system further comprises a remote server (6) and the control unit (3) comprises a communication module (7), wherein the remote server (6) is communicatively connected to the control unit (3) using the communication module (7). 7. The system according to claim 6, characterized in that the communication module (7) is a Wi-Fi module, while the communication connection between the control unit (3) and the remote server (6) is wireless. 8. The system according to any one of the preceding claims 6 and 7, characterized in that the computing module (4) is part of the remote server (6).