A method, system and device for evaluating hemodynamics using electrical impedance measurement

Abstract

Disclosed herein are systems, non-transitory computer-readable media, and methods for performing hemodynamic assessments using an electrical impedance-based device in a clinical setting. The system may include: a plurality of electrodes; and a controller coupled to the plurality of electrodes. The controller may receive a sequence of impedance data sets. The controller may generate corresponding impedance images. The controller may determine pre-action hemodynamic measurements based on a first region of interest (ROI) from at least one impedance image before an action. The controller may determine post-action hemodynamic measurements based on the first ROI from at least one impedance image after the action. The controller may receive at least one parameter associated with the action. The controller may determine a hemodynamic quality factor based at least on the pre-action hemodynamic measurements, the post-action hemodynamic measurements, and the at least one parameter associated with the action.

Description

[0001] Priority declaration

[0002] This application claims the benefit of the filing date of U.S. Provisional Patent Application Serial No. 62 / 954,885, filed on December 30, 2019, “ASSESSING HEMODYNAMICS USING ELECTRICAL IMPEDANCE MEASUREMENTS.” Background Art

[0003] This section is intended to introduce the reader to various aspects of the art that may be relevant to various aspects of the embodiments described or claimed below. This discussion is provided as background information to facilitate understanding of various aspects of the embodiments of the present disclosure. Therefore, although these statements include useful background, these statements should not be interpreted as admitting prior art.

[0004] Electrical impedance tomography (EIT) is a non-invasive imaging method that can be used to generate images or physiological measurements associated with a portion of a subject (e.g., a patient or object) by collecting data using electrodes disposed along the periphery of the subject. Potential applications of EIT include medical applications where real-time tomographic images or human physiological measurements may be useful. For example, EIT can be used to perform non-invasive monitoring of the cardiopulmonary system, which may be particularly useful for patients being treated in an intensive care unit (ICU) environment.

[0005] In an EIT system, an electrical signal (e.g., an electric current) may be injected into the periphery of a subject being imaged (e.g., a patient's torso). Electrical properties (e.g., voltage, potential) caused by the injected electrical signal may be collected at the periphery of the subject. Based on the collected data, an electrical impedance estimation map in each portion (e.g., pixel, voxel) of the subject may be generated or reconstructed. This process may be repeated over time, and a sequence of tomographic images may form a "video." This video may be used to provide physiological information to a physician or other clinical practitioner. Processing and / or quantification based on the EIT data may also be performed and / or used to calculate physiological parameters and / or quality factors, which may be used by a physician or other clinical practitioner. Summary of the invention

[0006] Embodiments of the present disclosure may include a method for performing hemodynamic assessment using an impedance-based device. The method may include determining a first impedance quantification associated with a first region of interest (ROI) in a first impedance image. The first impedance image may be associated with a first state of the patient before an action. The method may also include determining a second impedance quantification associated with the first region of interest in a second impedance image. The second impedance image may be associated with a second state of the patient after the action. The method may also include receiving at least one parameter associated with the action. The method may also include determining an intrathoracic pressure change or a simulated displacement volume or both in response to the at least one parameter associated with the action. The method may also include determining at least one hemodynamic parameter taking into account a difference between the first impedance quantification and the second impedance quantification, and at least one of the intrathoracic pressure change or the simulated displacement volume.

[0007] Other embodiments of the present disclosure may include a non-transitory computer-readable medium on which instructions are stored. When executed by a processor, the instruction may cause the processor to receive a sequence of impedance data sets. Each impedance data set in the sequence of impedance data sets may be associated with a corresponding time point. The instruction may also cause the processor to determine a pre-action hemodynamic measurement result based on a first impedance data set associated with a time point before the action. The instruction may also cause the processor to determine a post-action hemodynamic measurement result based on a second impedance data set associated with a second time point after the action. The instruction may also cause the processor to receive at least one parameter associated with the action. The instruction may also cause the processor to determine a hemodynamic quality factor using the pre-action hemodynamic measurement result, the post-action hemodynamic measurement result, and the at least one parameter associated with the action.

[0008] Other embodiments of the present disclosure may include a system. The system may include an electrical impedance tomography (EIT) system. The EIT system may include: a plurality of electrodes; and a controller coupled to the plurality of electrodes. The controller may include an interface module configured to collect EIT data from the plurality of electrodes. The controller may also include: at least one processor; and at least one non-transitory computer-readable storage medium having instructions stored thereon. When executed by the at least one processor, the instructions may cause the controller to receive a sequence of impedance data sets. The instructions may also cause the controller to generate a corresponding impedance image based on each impedance data set. The instructions may also cause the controller to determine a pre-action hemodynamic measurement based on a first region of interest (ROI) from at least one impedance image before the action. The instructions may also cause the controller to determine a post-action hemodynamic measurement based on the first ROI from at least one impedance image after the action. The instructions may also cause the controller to receive at least one parameter associated with the action. The instructions may also cause the controller to determine a hemodynamic figure of merit based at least on the pre-maneuver hemodynamic measurement, the post-maneuver hemodynamic measurement, and the at least one parameter associated with the maneuver. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Aspects of the present disclosure may be better understood by following the detailed description and referring to the accompanying drawings, in which:

[0010] Figure 1 is a schematic diagram of a method that may be used to assess hemodynamics using electrical impedance data according to one or more embodiments of the present disclosure;

[0011] Figure 2 is a schematic diagram of an electrical impedance tomography (EIT) system that can be used to assess hemodynamics according to one or more embodiments of the present disclosure;

[0012] Figure 3 is a schematic diagram of a method of obtaining electrical impedance data using an EIT system according to one or more embodiments of the present disclosure;

[0013] Figure 4 is a flow chart of a method for quantifying or assessing hemodynamics using EIT reconstruction data according to one or more embodiments of the present disclosure;

[0014] Figure 5 is a diagram of a user interface system that may be used to facilitate and / or review calculation of hemodynamic data from EIT reconstruction data according to one or more embodiments of the present disclosure;

[0015] Figure 6is a graph showing an example of quantifying a hemodynamic figure of merit based on electrical impedance data that may be used to assess hemodynamics according to one or more embodiments of the present disclosure;

[0016] Figure 7 is a flow chart of a method for quantifying a hemodynamic figure of merit based on hemodynamic data according to one or more embodiments of the present disclosure;

[0017] Figure 8 is a diagram illustrating a user interface that can facilitate determining a patient's hemodynamic response using the methods described herein, according to one or more embodiments of the present disclosure;

[0018] Fig. 9 is a comparative chart illustrating the performance of a method of determining hemodynamics from electrical impedance data according to one or more embodiments of the present disclosure; and

[0019] Fig.10 is a flow chart of a method of quantifying a hemodynamic figure of merit based on hemodynamic data according to one or more embodiments of the present disclosure. DETAILED DESCRIPTION

[0020] The illustrations presented herein are not actual views of any EIT system or any components thereof, but are merely idealized representations used to describe embodiments of the present disclosure.

[0021] As used herein, the singular forms following “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0022] As used herein, the term "may" with respect to a material, structure, feature, or method action indicates that this is intended for use in implementing an embodiment of the present disclosure, and such term is used in preference to the more restrictive term "is" to avoid any implication that other compatible materials, structures, features, and methods that may be used in combination therewith should or must be excluded.

[0023] As used herein, any relational terms such as “first”, “second”, etc. are used for clarity and convenient understanding of the present disclosure and the drawings, and do not imply or rely on any particular preference or order, unless the context clearly indicates otherwise.

[0024] As used herein, the term "substantially" with respect to a given parameter, property, or condition means and includes to the extent that a person skilled in the art would understand that the given parameter, property, or condition is met with a small degree of variance (such as within an acceptable manufacturing tolerance). By way of example, depending on the particular parameter, property, or condition being substantially met, the parameter, property, or condition may be at least 90.0% met, at least 95.0% met, at least 99.0% met, or even at least 99.9% met.

[0025] As used herein, the term "about" used with reference to a given parameter is inclusive of the stated value and has the meaning dictated by the context (e.g., it includes the degree of error associated with the measurement of the given parameter, as well as variations due to manufacturing tolerances, etc.).

[0026] The present disclosure relates to electronic impedance tomography (EIT) methods and systems, and more particularly to an EIT system capable of providing non-invasive hemodynamic measurements in real time or near real time based on impedance measurements.

[0027] One or more embodiments of the present disclosure are described below. In order to provide a concise description of these embodiments, certain features of the actual implementation may be omitted. It should be understood that in the actual implementation of the embodiments, as in any engineering or design project, several implementation-specific decisions will be made to achieve the developer's specific goals, and therefore, the implementations may differ from each other. In addition, although the development work may be complex and time-consuming, for ordinary technicians who benefit from the present disclosure, some developments will be routine tasks of design, processing and manufacturing.

[0028] When introducing elements of various embodiments of the present disclosure, the articles "a," "an," and "the" are intended to indicate that there are one or more elements. The terms "comprising," "including," and "having" are intended to be inclusive, and indicate that there may be additional elements in addition to the listed elements. Furthermore, reference to "one embodiment" or "an embodiment" of the present disclosure is not intended to be interpreted as excluding the existence of additional embodiments that also include the described features. Furthermore, the phrase A "based on" B is intended to indicate that A is based at least in part on B.

[0029] As discussed herein, reference may be made to "electrical impedance data". As described herein, electrical impedance data refers to data obtained from an electrical impedance tomography (EIT) system or an electrical impedance measurement device, or any other data related to the electrical properties (e.g., impedance, resistivity, capacitance, inductance, dielectric constant, etc.) of a measured subject (e.g., a patient, an object). Electrical impedance data refers to raw (i.e., unprocessed) data, filtered data, and / or tomographically reconstructed data. A tomographic reconstruction obtained from electrical impedance data may be specifically referred to herein as an "electrical impedance image" or "electrical impedance video".

[0030] The electrical impedance image may be further described as an "absolute impedance image," a "differential impedance image," and a "volume image" of the subject. As discussed herein, an absolute impedance image relates to an image in which the representation (e.g., value) of each pixel or voxel is associated with the impedance of the corresponding portion of the subject being imaged. As discussed herein, a differential impedance image relates to an image in which the representation (e.g., value) of each pixel or voxel is associated with the change in impedance of the corresponding portion of the subject relative to a baseline image. As discussed herein, a volumetric image relates to an image in which the representation (e.g., value) of each pixel or voxel is associated with the volume of a biological fluid (e.g., air, blood, water, tissue type). In addition, it should be understood that, as mentioned herein, an impedance image or video may be: a tomographic image, which may be two-dimensional (2-D) or three-dimensional (3-D); and a tomographic movie, which has a time dimension.

[0031] As discussed above, due to the nature of the measurements and the speed of data acquisition and processing, electrical impedance-based systems such as EIT can be used to generate high-frequency, real-time physiological data that can be helpful to physicians during certain diagnostic and / or clinical procedures. In addition, because impedance-based systems are generally non-invasive, they can be used for a wider range of patient populations under a variety of conditions. The present disclosure relates to EIT systems and methods of operating the same that can calculate physiological parameters associated with cardiovascular activity for hemodynamic assessment of a patient.

[0032] Hemodynamic assessment can be used to identify patients who may benefit from certain types of treatment or intervention. For example, volume replacement (i.e., fluid substitution) is often used for patients undergoing cardiac surgery to improve their surgical outcomes. However, only a subset of patients respond to fluids and benefit from increases in systolic volume (SV) and / or cardiac output (CO) in response to volume replacement. Patients who do not respond to fluids may not benefit from volume replacement and may be susceptible to potential side effects of such interventions. Therefore, hemodynamic assessment can be used to prevent the ineffective or potentially harmful use of volume replacement in these patients. More generally, hemodynamic assessment can be a powerful diagnostic tool in a variety of clinical applications.

[0033] Conventional methods for hemodynamic assessment may employ invasive techniques. As an example of such techniques, certain systems employ catheters applied to peripheral arteries to obtain invasive measurements of blood pressure signals. As described in detail below, the invasive blood pressure signal can be monitored during some external maneuvers, and the response of the blood pressure signal to the maneuvers can be quantified. The use of invasive techniques and methods to measure cardiac parameters may present some complications for certain patients, thereby limiting their application. Therefore, as discussed above, the use of non-invasive impedance-based devices and systems (such as EIT systems) can increase the application of hemodynamic assessment.

[0034] In view of the foregoing, the present disclosure relates to the use of an impedance-based system (such as an EIT system) to calculate physiological parameters related to hemodynamic assessment, as discussed above. In some embodiments, the impedance-based system may employ filtering and / or reconstruction processing of impedance data to quantify physiological parameters in a region of interest (ROI) of an image. The hemodynamic parameters discussed herein may include pulse wave impedance variation (PIV), systolic volume (SV), systolic volume variation (SVV), cardiac output (CO), associated indexes, and / or other hemodynamic quality factors, as described in detail below. In some embodiments, the impedance-based system may be connected to other medical equipment (such as a mechanical ventilation system and / or an electrocardiogram monitor) to receive additional clinical data in order to improve the hemodynamic assessment and / or provide the calculated data. In some embodiments, the impedance-based system may include a user interface (UI) that can guide clinical practitioners during the hemodynamic assessment.

[0035] Figure 1 A schematic diagram of a method 10 for performing a hemodynamic assessment of a patient 12 is shown. In the hemodynamic assessment 10, the patient 12 may receive an intervention 14 that may cause a hemodynamic change in the patient. The patient 12 may be monitored using an impedance-based device that collects electrical impedance data 16. The electrical impedance data 16 may include data from before the intervention 14, during the intervention 14, and / or after the intervention 14. The electrical impedance data 16 may be processed to obtain one or more hemodynamic-related metrics 18. The hemodynamic metrics may be displayed to a medical practitioner, or the hemodynamic metrics may be compared to a threshold value to generate an alarm signal or other type of display, as described in detail below.

[0036] The intervention 14 can be any controlled intervention that may generate hemodynamic changes in the patient 12. In some cases, a cardiac preload simulation action 22 can be used (e.g., a change in patient posture, a change in limb position). In some embodiments, the impedance-based system can be configured to provide instructions to the practitioner using the preload simulation action 22 during the hemodynamic assessment process. For example, the impedance-based system can provide instructions associated with the timing of initiation and / or termination of the preload simulation action 22 and / or specific instructions for the procedure (e.g., "lift the leg 45 degrees"). The electrical impedance data 16 can be recorded according to the instructions provided and may include metadata associated with the instructions provided.

[0037] In the case where the patient 12 is connected to a mechanical ventilator, a ventilator action 26 may be used. For example, temporarily changing the positive end-expiratory pressure (PEEP) parameter of the ventilator (PEEP action 24) can be used to increase intrathoracic pressure in a controlled manner. In some embodiments, the impedance-based system may be configured to provide instructions to the practitioner to perform the ventilator action 26 during the hemodynamic assessment process. For example, the impedance-based system may provide instructions associated with the timing of initiation and / or termination of the ventilator action 26 and / or specific instructions for the procedure (e.g., for the ventilator action 24, "increase PEEP by 5cmH2O"). In some embodiments, the impedance-based system may be connected to a mechanical ventilator to receive respiratory data from the ventilator, which may be included as metadata of the electrical impedance data 16. In some embodiments, the impedance-based system may include a flow sensor and / or a pressure sensor, which may provide respiratory data associated with ventilation, which may be included as metadata of the electrical impedance data 16. In some embodiments, the impedance-based system may be configured to control a mechanical ventilator to perform a hemodynamic assessment. Electrical impedance data 16 may be recorded according to ventilator action 26 during a hemodynamic assessment and may include respiratory data and / or ventilator control as associated metadata.

[0038] The electrical impedance data 16 that can be used for hemodynamic assessment can include relative impedance 32, absolute impedance 34, absolute tomographic images 36, relative tomographic images 38, and other such images. In some embodiments, the hemodynamic metrics 18 can be calculated separately in different regions of interest (ROIs) of the subject. In those embodiments, the tomographic images 34, 36 can be used as described in detail below.

[0039] Figure 2 A schematic diagram of a system 110 is provided that includes an EIT device 112 that is used in conjunction with a mechanical ventilator 162 to perform a hemodynamic assessment. It should be understood that, as discussed above, the hemodynamic assessment can be performed in the absence of mechanical ventilation (such as ventilation provided by the mechanical ventilator 162). The EIT device 112 can be coupled to an electrode belt 116 via an electrical lead 114, which can be placed on the patient 12. The electrode belt 116 can have one or more rows of electrodes that are disposed along the periphery of the electrode belt 16. The electrodes of the electrode belt 16 can be spatially distributed along the periphery of the torso of the patient 12. The EIT device 112 can inject current through the electrodes of the electrode belt 116 and can collect the resulting voltage. Based on the collected data, the EIT device 112 can calculate one or more hemodynamic metrics (e.g., Figure 1 hemodynamic measures of 18).

[0040] The EIT device 112 may execute filtering algorithms, reconstruction algorithms, and / or quantification algorithms, as described in detail below. To this end, the computing device may include one or more processors 132 and one or more processing memory devices 134 (e.g., cache memory, random access memory (RAM)) to facilitate the execution of the algorithms. The memory device 134 may also include one or more protocols for performing hemodynamic assessments. These protocols may include instructions to be provided to the practitioner and instructions for creating metadata or associating metadata with impedance data. The memory device 134 may also include one or more segmentation algorithms to automatically determine the ROI used in the hemodynamic assessment. In some embodiments, the segmentation algorithm may include principal component analysis (PCA).

[0041] In some embodiments, some or all of the algorithms described herein may be performed by a coprocessor 142, which may be a second processor, a dedicated processor such as a graphics processing unit (GPU), an application specific integrated circuit (ASIC) (designed to execute the algorithms), a field programmable gate array (FPGA) (containing a configuration program to execute the algorithms), or any other special-purpose electronic device.

[0042] The EIT device 112 may also include an interface module 136 to control the current injected into the electrical leads 114 and to measure the voltage between the electrical leads 114. The interface module 136 may include, among other things, an analog signal generator, an analog-to-digital converter, a digital-to-analog converter, a digital signal processor, filters, and impedance matching circuits to improve the signal-to-noise ratio and reduce crosstalk.

[0043] In some embodiments, the EIT device 112 may include a display 138 that can be used to provide reconstructed images, hemodynamic charts and / or hemodynamic indices, and diagnostic parameters that can be calculated based on the EIT images. The display 138 can also be used to provide instructions to practitioners performing hemodynamic assessments, as discussed above. In some embodiments, the display 138 may include or be connected to a speaker or similar sound generating device to provide an auditory alarm or auditory command associated with the hemodynamic assessment. In some embodiments, the EIT device 112 may include a sensor 139, which may include one or more of a pressure sensor, a flow sensor and a flow sensor, a carbon dioxide sensor, and / or any combination thereof. The sensor 139 may be configured to measure data, such as respiratory data from the EIT device 112 and / or an associated ventilator 162. The respiratory data obtained from the sensor 139 can be used to facilitate the hemodynamic assessment process, as discussed above.

[0044] In some embodiments, the EIT device 112 may include an input / output interface 140, such as a network interface, a hard disk interface, and / or a peripheral interface, to send or receive data that may facilitate the operation of the EIT, as discussed herein. For example, the EIT device 112 may be connected to a ventilator device 162 via an interface 150 that is coupled to the input / output interface 140. The interface 150 may be used to carry control commands and / or data that may be used to facilitate the hemodynamic assessment process, as discussed above.

[0045] In addition, the input / output interface 140 may also be connected to a position sensor 169, which may be in contact with the patient or may be placed on the automatic bed where the patient is located. For example, if a preload cardiac simulation maneuver (e.g., preload cardiac simulation maneuver 22) is used by repositioning the patient or the patient's limbs, the position sensor 169 may measure the actual position and provide it to the EIT device 112 through the input / output interface. In some embodiments, the position sensor 169 may be a video recording device that records the patient, and the video recording device is accompanied by an image processing system that can quantify the relative position of the limbs based on the recorded video. The measurement results can be incorporated as metadata for the electrical impedance data.

[0046] In certain configurations of system 110 (such as Figure 2 ), the patient 12 may be connected to a mechanical ventilator 162. The ventilator 162 may include a controller 164 (e.g., a processor, a microcontroller), which may be combined with one or more memory devices 166 to control the operation of the ventilator 162. In some embodiments, the memory device 166 may include a protocol for executing a ventilator action (e.g., ventilator action 26) to facilitate hemodynamic assessment. The mechanical ventilator device 162 may include a sensor 168, which may be a pressure sensor, a flow sensor, and a flow sensor, a carbon dioxide sensor. The ventilator device 162 may also include a pump 17, which may be a pressure-controlled or volume-controlled pump to provide respiratory support for the patient 12. The sensor 168 and the pump 170 may be controlled and / or monitored by the controller 164.

[0047] In some embodiments, ventilator device 162 may include an input / output interface 172, such as a network interface, a hard disk interface, and / or a peripheral interface, to send or receive data that may facilitate respiratory support operations. Input / output interface 172 may be used to connect ventilator 162 to EIT device 112 via interface 150, as discussed above. Interface 150 may be used to carry control commands or instructions from EIT device 112 and provide respiratory data from sensor 168 to EIT device 112 to facilitate the hemodynamic assessment process, as discussed above.

[0048] In some embodiments, the ventilator device 162 may include a display 174 that can be used to provide respiratory graphs, indices, and other physiological parameters associated with the respiratory support provided to the patient. In certain embodiments, the ventilator device 162 may be configured to facilitate hemodynamic assessment. In such devices, the display 174 may be configured to provide instructions to a practitioner performing a hemodynamic assessment, as discussed above. In some embodiments, the display 174 may include or be connected to a speaker or similar sound generating device to provide an audible alarm or audible command associated with the hemodynamic assessment.

[0049] Figure 3 A schematic diagram 200 for performing impedance measurements is shown. Electrical signals 202 may be injected into pairs of electrodes 204 disposed along electrode strips 116 around the patient 12. The electrical signals 202 may be injected in a preprogrammed sequence, and the resulting electrical potentials 206 may be read between the electrode pairs 204. The collection of electrical potentials 206 may form raw impedance data that may be used for the hemodynamic assessments discussed herein.

[0050] Figure 4 The use of EIT system (such as Figure 3 Flowchart of a method 210 for calculating hemodynamic parameters using a system 110 of the invention. The collected potentials 206 may be used to perform a tomographic reconstruction (block 212) to obtain a series of impedance images 214. The tomographic reconstruction (block 212) may employ an algorithm that provides an absolute impedance image or a relative impedance image. The reconstruction algorithm of block 212 may include filters or other signal processing tools to mitigate noise and other artifacts. The reconstruction algorithm may be a model-based algorithm.

[0051] The series of impedance images 214 may be further filtered (block 216) to separate individual component contributions. For example, a respiratory component 218 and / or a cardiac component 220 may be extracted from the impedance image 214. Since the respiratory frequency is typically lower than the cardiac frequency, the filtering algorithm of block 216 may employ frequency-based filtering in the temporal dimension of the impedance video 214. Examples of frequency-based filtering include high-pass filtering, low-pass filtering, band-pass filtering, Fourier-based filtering, moving average filters, autoregressive filters, autoregressive moving average (ARMA) filters, wavelet filters, state-space filters, or any other filter capable of separating components based on their frequencies. In addition, since disturbances from cardiac events and respiratory events are concentrated in different regions, the filtering algorithm of block 216 may employ ROIs to facilitate extraction of the cardiac component 220. It should be understood that block 216 may employ any filtering algorithm capable of providing a quantifiable cardiac component 220 or separating the quantifiable cardiac component from the respiratory component 218, which may be predominant.

[0052] The cardiac components of the impedance image 214 may be quantified 220 in separate ROI regions (block 222). For example, pixels associated with cardiac tissue and pixels associated with lung tissue may be placed in separate ROIs. In some embodiments, this process may be accomplished using a principal component analysis (PCA) approach. This spatial separation may improve the quality of impedance data used for hemodynamic assessment by reducing crosstalk between tissues that respond incoherently to cardiac events, such as in Figure 5 Quantification may provide one or more physiological parameters 224 that may be used to perform a hemodynamic assessment.

[0053] Fig.10 shows a computational impedance system such as Figure 3 Flowchart of a method 230 for calculating hemodynamics of EIT system 110 of FIG. 230 . Method 230 can be used to calculate hemodynamic parameters without performing image reconstruction. In method 230 , potential 206 can be used directly, which can be formed or arranged as a data matrix (e.g., a time series of a matrix, where each element of the matrix is ​​a potential associated with an electrode pair). In the method, filtering (box 236) can include filters or other signal processing tools to mitigate noise or other artifacts. In addition, filtering in box 236 can be used to separate separate component contributions. For example, respiratory component 238 and / or cardiac component 240 can be extracted from potential 206. Since the respiratory frequency is generally lower than the cardiac frequency, the filtering algorithm of box 236 can use frequency-based filtering on the time dimension of potential 206. Examples of frequency-based filtering include high-pass filtering, low-pass filtering, band-pass filtering, Fourier-based filtering, moving average filters, autoregressive filters, autoregressive moving average (ARMA) filters, wavelet filters, state-space filters, or any other filter capable of separating components based on the frequency of the components. It should be appreciated that block 236 may employ any filtering algorithm capable of providing a quantifiable cardiac component 240 or separating the quantifiable cardiac component from the respiratory component 238, which may be predominant.

[0054] The cardiac component 240 of the readout signal 206 may be further filtered (block 242) to improve the performance of the hemodynamic quantification. For example, certain elements (e.g., signals from a particular electrode pair) may be more sensitive to cardiac changes, while other elements may be more sensitive to respiratory changes. In some embodiments, a principal component analysis (PCA) approach may be used to implement this process. This further filtering may improve the quality of the hemodynamic assessment by reducing crosstalk between data elements that respond incoherently to cardiac events. Quantification may provide one or more physiological parameters 244 that may be used to perform the hemodynamic assessment.

[0055] In some embodiments, a heartbeat marker can facilitate quantification of the cardiac component 220, which can provide a synchronization signal associated with a cardiac cycle event. For example, the heartbeat marker can be associated with an atrial systolic peak or a diastolic peak, an aortic pressure peak, or any of the P peak, Q peak, R peak, S peak, or T peak of an electrocardiogram signal (ECG). The heartbeat marker can be extracted from a cardiac electrical signal, which can be acquired using a separate patient monitor. In some embodiments, the heartbeat marker can be obtained using electrodes of an EIT device (e.g., electrodes in an electrode belt 116 of an EIT device 112).

[0056] As discussed above, the impedance data may be accompanied by metadata obtained, for example, by position sensors, video images, mechanical ventilators, practitioner input, and / or flow / pressure sensors. The metadata may facilitate quantification of physiological parameters 224. For example, the metadata may provide time information (e.g., initiation time of the action, termination time of the action, duration of the action), action-specific information (e.g., action type, simulated volume, volume change, tidal volume), ventilator-specific information (e.g., respiratory rate, respiratory flow, respiratory pressure, inspiratory time, expiratory time, spontaneous expiratory events, tidal volume), and / or other physiological information (e.g., pulse, oxygen concentration, heartbeat markers). For example, the metadata may be used to perform cardiac component extraction (e.g., heartbeat synchronization), automatic segmentation of ROIs, filtering and / or extraction of cardiac components 222, and / or calculation of hemodynamic quality factors.

[0057] Figure 5 1 shows user interface elements of an EIT device (e.g., EIT device 112) that may be provided in a display (e.g., display 138). Specifically, Figure 5 An ROI map 250 is shown. The illustrated ROI map 250 includes a lung ROI 252 that includes pixels where lung tissue is the predominant tissue. The illustrated ROI map 250 also includes a heart ROI 254 that includes pixels where heart tissue is the predominant tissue. Figure 5 Also included is an impedance plethysmogram graph 260. The plethysmogram graph 260 includes a lung plethysmogram 262 that displays impedance changes in the lung ROI 252 and a cardioplethysmogram 264 that displays impedance changes in the cardio ROI 254. The plethysmogram graph 260 shows changes in impedance along a time axis 266.

[0058] The plethysmogram graph 260 is shown to display cardiac components (e.g., Figure 4 of the cardiac component 220), and the respiratory component (e.g., Figure 4218) is filtered out. That is, the plethysmogram 262 shows the impedance change in the lung ROI 252 due to a cardiovascular event, while the plethysmogram 264 shows the impedance change in the heart ROI 254 due to the same cardiovascular event. For example, at time 270, the heart plethysmogram 264 presents a valley, which indicates that an increase in tissue fluid causes a decrease in impedance. At the same time 270, the lung plethysmogram 262 presents a peak, which indicates that an increase in air is associated with a decrease in lung perfusion. This behavior may be associated with diastole. In contrast, at time 272, the lung plethysmogram 262 presents a value, which may be associated with lung perfusion, while the heart plethysmogram presents a peak, which may be associated with a decrease in tissue fluid. This behavior may be associated with systole. Therefore, using different ROIs can allow for improved ability of the EIT system 112 to distinguish between different cardiovascular events, which can improve the calculation of the quality factor of the hemodynamic.

[0059] Figure 6 A graphical representation of a hemodynamic quality factor, pulse wave impedance variation (PIV), which can be calculated using the systems and methods discussed herein is provided. Graph 280 shows an impedance plethysmogram 281 of a cardiac component, which can be obtained over time from pixels in a lung ROI (e.g., lung ROI 252). It should be understood that the cardiac component can be obtained from pixels in lung ROI 252 or heart ROI 254 as well as from non-segmented pixels. Impedance plethysmogram 281 shows the variation of a cardiac component (e.g., cardiac component 222) over multiple respiratory cycles (e.g., respiratory component 220). During exhalation (represented at time 282), the intrathoracic pressure is lower, so the oscillations of plethysmogram 281 are higher than those of the plethysmogram 281. MAX During inspiration (represented at time 284), the amplitude PP of the plethysmogram 281 is MIN The graph also shows the average pressure PP MEAN Based on these measurements extracted from the EIT system plethysmogram, the EIT system can automatically calculate the Pulse Impedance Variation (PIV) Index using the following expression:

[0060]

[0061] The PIV index indicates the patient's fluid responsiveness. In some embodiments, the EIT system may store standardized thresholds for PIV and may automatically provide an indication if the patient's PIV index is above or below the standardized thresholds.

[0062] Figure 7A flow chart of a method 300 for calculating the PIV discussed above is provided. Based on the hemodynamic data 302 (e.g., a plethysmogram of a cardiac ROI), the EIT system may calculate one or more metrics (block 304). The EIT system may employ the metadata described above to facilitate the calculation of the metrics. For example, the respiratory data may be used to determine the moment of inspiration or the moment of expiration to collect the PIV, respectively. MIN or PP MAX In block 304, the EIT system may derive an index 306, such as a PIV index, based on one or more metrics. The index 306 may be associated with the patient's fluid responsiveness. Figure 7 A quality factor based on amplitude is shown, but it should be understood that other signal characteristics may be used, such as baseline, phase lag or delay between heartbeats (e.g., heartbeat markers discussed above) and delay between oscillations (i.e., propagation time).

[0063] Figure 8 A user interface 320 is shown that can be used to provide hemodynamic information to a medical practitioner. The user interface 320 can include a plethysmogram chart 322 and a stroke volume chart 324. The data for the plethysmogram chart 322 and the stroke volume chart 324 can be calculated based on impedance data calculated from the EIT system. The stroke volume chart 324 can be calculated based on cardiac components measured in the cardiac ROI or the lung ROI. The stroke volume chart 324 can be a chart of absolute stroke volume, or a chart of percentage change relative to a reference stroke volume. The user interface also includes: a physiological parameter display 326, which shows the current stroke volume; a parameter display 328, which shows the heart rate; and a parameter display 330, which shows the current cardiac output. These parameter displays can provide quantitative information to assist the medical practitioner.

[0064] Figure 8 Also shown is the performance of the EIT system during maneuvers. During the period between time events 332 and 334, PEEP was changed from 8 cmH2O to 13 cmH2O and back to 8 cmH2O. At time 336, the patient's legs were raised and lowered. The stroke volume graph 324 shows that the patient appears to be fluid responsive. At time 338, the patient receives a volume replacement protocol and exhibits an increase in systolic volume, as expected for a fluid responsive patient.

[0065] Fig. 9350 is a diagram comparing an embodiment of a method in the methods presented herein with an invasive method for assessing patient hemodynamics. The diagram 350 presents impedance changes of a cardiac ROI 362 estimated using an EIT system (EIT data set 352) and compares it with a systolic volume 360 ​​obtained using a VolumeView (Edwards, Inc.) device. The collected VolumeView data is uncalibrated (VolumeView uncalibrated data set 354) and calibrated (VolumeView calibrated data set 356). The diagram 350 also initially shows a basal level 364. After the basal level 364, a PEEP action 366 is initiated. After the PEEP action 366, the patient returns to the basal level 368. A cardiac preload simulation action 370 is also shown, which is performed by lifting the patient's legs. After the action 370, the patient returns to the basal level 372. Finally, the patient receives volume displacement therapy 374.

[0066] Non-limiting exemplary embodiments of the present disclosure may include:

[0067] Embodiment 1: A method for performing hemodynamic assessment using an impedance-based device, the method comprising: determining a first impedance quantification associated with a first region of interest (ROI) in a first impedance image, wherein the first impedance image is associated with a first state of a patient before an action; determining a second impedance quantification associated with the first region of interest in a second impedance image, wherein the second impedance image is associated with a second state of the patient after the action; receiving at least one parameter associated with the action; determining an intrathoracic pressure change or a simulated displacement volume or both in response to the at least one parameter associated with the action; and determining at least one hemodynamic parameter taking into account a difference between the first impedance quantification and the second impedance quantification, and at least one of the intrathoracic pressure change or the simulated displacement volume.

[0068] Embodiment 2: A method according to embodiment 1, wherein the at least one parameter associated with the action includes one or more of a positive end-expiratory pressure (PEEP) value, a PEEP change, an inspiratory time, an expiratory time, a respiratory cycle, a tidal volume value, a tidal volume change, or a position change.

[0069] Embodiment 3: A method according to embodiment 2, wherein the at least one parameter associated with the action is received from one or more of a mechanical ventilation device, a pressure sensor configured to measure the patient's respiratory system, a flow sensor configured to measure the patient's respiratory system, or a carbon dioxide sensor configured to measure the patient's respiratory system.

[0070] Embodiment 4: A method according to any one of embodiments 1 to 3, wherein the at least one parameter associated with the action is received via an input device of the impedance-based device, from an external device, from a sensor disposed within the impedance-based device, or from both.

[0071] Embodiment 5: A method according to any one of embodiments 1 to 4, wherein the method further comprises: determining respiratory composition data based on impedance data generated by the impedance-based device; and generating at least one parameter associated with the action based on the respiratory composition data.

[0072] Embodiment 6: The method according to any one of embodiments 1 to 5, wherein the first ROI is associated with the heart region or the lung region or both.

[0073] Embodiment 7: A method according to any one of embodiments 1 to 6, wherein the action comprises a cardiac preload simulation action, and the cardiac preload simulation action comprises one or more of a posture change or a position change of at least one limb of the patient.

[0074] Embodiment 8: The method according to any one of embodiments 1 to 7, wherein the action comprises a mechanical ventilation action.

[0075] Embodiment 9: According to the method described in any one of Embodiments 1 to 8, the method further includes: acquiring a first plurality of electrical impedance signals; reconstructing the first impedance image based on the first plurality of electrical impedance signals; acquiring a second plurality of electrical impedance signals; and reconstructing the second impedance image based on the second plurality of electrical impedance signals.

[0076] Embodiment 10: A method according to any one of embodiments 1 to 9, wherein the at least one hemodynamic parameter includes one or more of pulse wave impedance variation (PIV), cardiac output (CO), systolic volume (SV), PIV variation, CO variation or SV variation.

[0077] Embodiment 11: A non-transitory computer-readable medium having instructions stored thereon, which, when executed by a processor, causes the processor to perform steps including: receiving a sequence of impedance data sets, wherein each impedance data set in the sequence of impedance data sets is associated with a corresponding time point; determining a pre-action hemodynamic measurement result based on a first impedance data set associated with a time point before the action; determining a post-action hemodynamic measurement result based on a second impedance data set associated with a second time point after the action; receiving at least one parameter associated with the action; and determining a hemodynamic quality factor using the pre-action hemodynamic measurement result, the post-action hemodynamic measurement result, and the at least one parameter associated with the action.

[0078] Embodiment 12: A non-transitory computer-readable medium according to embodiment 11, wherein the non-transitory computer-readable medium is configured to be executed by an electrical impedance tomography (EIT) device processor or by a general-purpose computer processor connected to the EIT device, and wherein the instructions cause the EIT device processor to: reconstruct a first impedance image based on the first impedance data set; determine the pre-action hemodynamic measurement results based on a first region of interest (ROI) in the first impedance image; and before the determination of the post-action hemodynamic measurement results, reconstruct a second impedance image based on the second impedance data set; and determine the post-action impedance image based on the first ROI in the second impedance image.

[0079] Embodiment 13: A non-transitory computer-readable medium according to any one of Embodiments 11 or 12, wherein the action includes a mechanical ventilator action, and wherein the instruction causes the processor to request the mechanical ventilator to automatically perform the mechanical ventilator action before the determination of the hemodynamic measurement result after the action and after the determination of the hemodynamic measurement result before the action.

[0080] Embodiment 14: A non-transitory computer readable medium according to any one of embodiments 11 to 13, wherein the instructions cause the processor to determine the intrathoracic pressure change or simulated displacement volume based at least in part on the at least one parameter associated with the action.

[0081] Embodiment 15: A non-transitory computer-readable medium according to any one of embodiments 11 to 14, wherein the at least one parameter associated with the action is received from a mechanical ventilator, a flow sensor, a pressure sensor, a volume sensor, an electrical impedance measurement device, or an electrical impedance tomography (EIT) device.

[0082] Embodiment 16: A non-transitory computer-readable medium according to any one of embodiments 11 to 15, wherein the pre-action hemodynamic measurement results and the post-action hemodynamic measurement results include pulse wave impedance change (PIV), cardiac output (CO) or systolic volume (SV) or any combination thereof.

[0083] Embodiment 17: A non-transitory computer readable medium according to any one of embodiments 11 to 16, wherein the hemodynamic quality factor comprises a difference between the pre-action hemodynamic measurement result and the post-action hemodynamic measurement result.

[0084] Embodiment 18: The non-transitory computer readable medium of Embodiment 17, wherein the computer readable medium comprises instructions causing the processor to compare the hemodynamic figure of merit to a threshold level to determine fluid responsiveness.

[0085] Embodiment 19: A system, the system comprising: an electrical impedance tomography (EIT) system, the EIT system comprising: a plurality of electrodes; and a controller, the controller being connected to the plurality of electrodes, the controller comprising: an interface module, the interface module being configured to collect EIT data from the plurality of electrodes; at least one processor; and at least one non-transitory computer-readable storage medium, on which instructions are stored, which, when executed by the at least one processor, cause the controller to: receive a sequence of impedance data sets; generate a corresponding impedance image based on each impedance data set; determine a pre-action hemodynamic measurement result based on a first region of interest (ROI) from at least one impedance image before the action; determine a post-action hemodynamic measurement result based on the first ROI from at least one impedance image after the action; receive at least one parameter associated with the action; and determine a hemodynamic quality factor based at least on the pre-action hemodynamic measurement result, the post-action hemodynamic measurement result, and the at least one parameter associated with the action.

[0086] Embodiment 20: According to the system described in embodiment 19, the system includes a mechanical ventilator, the mechanical ventilator includes an input / output interface, the input / output interface is connected to the input / output interface of the EIT system, wherein the mechanical ventilator includes a computing device, and the computing device is configured to transmit at least one parameter associated with the action to the EIT system.

[0087] Embodiment 21: A system according to embodiment 20, wherein the at least one parameter associated with the action includes a positive end-expiratory pressure (PEEP) value, a PEEP change, an inspiratory time, an expiratory time, a respiratory cycle, a tidal volume, or any combination thereof.

[0088] Embodiment 22: The system of any one of Embodiments 20 or 21, wherein the instructions cause the controller to transmit at least one control command to the mechanical ventilator associated with an action.

[0089] Embodiment 23: According to the system described in any one of Embodiments 19 to 22, the system also includes an automatic bed, the automatic bed includes an input / output interface, and the input / output interface is connected to the input / output interface of the EIT system, wherein the automatic bed is configured into multiple bed positions, and wherein the automatic bed is configured to transmit bed position data to the EIT system, and wherein receiving the at least one parameter associated with the action includes receiving the bed position data.

[0090] Embodiment 24: A system according to any one of embodiments 19 to 23, the system comprising a position sensor configured to measure position data of a patient connected to the EIT system, and wherein receiving the at least one parameter associated with the action comprises receiving the position data from the position sensor.

[0091] Embodiment 25: A system according to embodiment 24, wherein the position sensor includes a video sensor or a contact sensor.

[0092] Embodiment 26: A system according to any one of Embodiments 19 to 25, wherein the EIT system includes a breathing sensor configured to provide the at least one parameter associated with the action.

[0093] Embodiment 27: A system according to any one of embodiments 19 to 26, the system comprising a respiratory sensing device configured to provide the at least one parameter associated with the action. The embodiments described in the present disclosure may be susceptible to various modifications and alternative forms, and specific embodiments have been shown by way of example in the accompanying drawings and have been described in detail herein. However, it should be understood that the present disclosure is not intended to be limited to the specific embodiments disclosed, and the present disclosure covers all modifications, combinations, equivalents and substitutes that fall within the spirit and scope of the embodiments, as defined by the appended claims and their legal equivalents. In addition, the techniques and systems claimed herein refer to practical and useful embodiments and can be applied to specific examples that significantly improve the practical nature of the present technical field, and are therefore not abstract, intangible or purely theoretical. In addition, in claims attached to the end of this specification and containing one or more elements designated as "means for [performing function]" or "steps for [performing function]", such elements should be interpreted in accordance with Section 112(f) of Title 35 of the United States Code. However, with respect to any claim containing elements specified in any other manner, such elements are not to be construed under 35 U.S.C. § 112(f).

Claims

1. A method for performing hemodynamic assessment using an impedance-based device prior to introducing a displacement volume, the method comprising: determining a first impedance quantification associated with a first region of interest (ROI) in a first impedance image, wherein the first impedance image is associated with a first state of the patient prior to an external maneuver, wherein the external maneuver comprises a cardiac preload simulation maneuver or a ventilation maneuver configured to induce a change in intrathoracic pressure, simulate displacement volume, or both; executing the external action; determining a second impedance quantification associated with the first region of interest in a second impedance image, wherein the second impedance image is associated with a second state of the patient after the external action; receiving at least one parameter associated with the external action; determining the intrathoracic pressure change or the simulated displacement volume or both in response to a change in the at least one parameter associated with the external action; and At least one hemodynamic parameter is determined taking into account a difference between the first impedance quantification and the second impedance quantification.

2. The method of claim 1 , wherein the at least one parameter associated with the action comprises one or more of a positive end expiratory pressure (PEEP) value, a PEEP change, an inspiratory time, an expiratory time, a respiratory cycle, a tidal volume value, a tidal volume change, or a position change.

3. The method of claim 2, wherein the at least one parameter associated with the action is received from one or more of a mechanical ventilation device, a pressure sensor configured to measure the patient's respiratory system, a flow sensor configured to measure the patient's respiratory system, or a carbon dioxide sensor configured to measure the patient's respiratory system.

4. The method of claim 1, wherein the at least one parameter associated with the action is received via an input device of the impedance-based device, from an external device, from a sensor disposed within the impedance-based device, or from both.

5. The method according to claim 1, wherein the method further comprises: determining respiratory composition data based on impedance data generated by the impedance-based device; as well as The at least one parameter associated with the motion is generated based on the respiratory composition data. The method of claim 1 , wherein the first ROI is associated with a heart region or a lung region or both.

7. The method of claim 1, wherein the motion comprises a cardiac preload simulation motion comprising one or more of a posture change or a position change of at least one limb of the patient.

8. The method of claim 1, wherein the action comprises a mechanical ventilation action.

9. The method according to claim 1, further comprising: acquiring a first plurality of electrical impedance signals; reconstructing the first impedance image based on the first plurality of electrical impedance signals; acquiring a second plurality of electrical impedance signals; as well as The second impedance image is reconstructed based on the second plurality of electrical impedance signals.

10. The method of claim 1, wherein the at least one hemodynamic parameter comprises one or more of pulse wave impedance variation, cardiac output, systolic volume, pulse wave impedance variation, cardiac output variation, or systolic volume variation.

11. A system for assessing hemodynamics, the system comprising: An electrical impedance tomography (EIT) system, the EIT system comprising: a plurality of electrodes; and a controller coupled to the plurality of electrodes, the controller comprising: an interface module configured to collect EIT data from the plurality of electrodes; at least one processor; and at least one non-transitory computer-readable storage medium having stored thereon instructions that, when executed by the at least one processor, cause the controller to: receiving a sequence of impedance data sets prior to introducing a displacement volume; generating a corresponding impedance image according to each impedance data set; determining a pre-maneuver hemodynamic measurement based on a first region of interest (ROI) from at least one impedance image prior to an external maneuver, wherein the external maneuver comprises a cardiac preload simulation maneuver or a ventilation maneuver, The external action is configured to cause a change in intrathoracic pressure, simulate a displacement volume, or both; determining a post-maneuver hemodynamic measurement based on the first ROI from at least one impedance image after the external maneuver; receiving at least one parameter associated with the external action; and A hemodynamic factor is determined based on at least the pre-maneuver hemodynamic measurement and the post-maneuver hemodynamic measurement.

12. A system according to claim 11, wherein the system includes a mechanical ventilator, the mechanical ventilator includes an input / output interface, the input / output interface is connected to the input / output interface of the EIT system, wherein the mechanical ventilator includes a computing device, and the computing device is configured to transmit the at least one parameter associated with the action to the EIT system.

13. The system of claim 12, wherein the at least one parameter associated with the action comprises a positive end-expiratory pressure (PEEP) value, a PEEP variation, an inspiratory time, an expiratory time, a respiratory cycle period, a tidal volume, or any combination thereof.

14. The system of claim 12, wherein the instructions cause the controller to transmit at least one control command to the mechanical ventilator associated with an action.

15. The system of claim 11, further comprising an automatic bed, the automatic bed comprising an input / output interface coupled to an input / output interface of the EIT system, wherein the automatic bed is configured into a plurality of bed positions, and wherein the automatic bed is configured to transmit bed position data to the EIT system, and wherein receiving the at least one parameter associated with the action comprises receiving the bed position data.

16. The system of claim 11, comprising a position sensor configured to measure position data of a patient connected to the EIT system, and wherein receiving the at least one parameter associated with the motion comprises receiving the position data from the position sensor.

17. The system of claim 16, wherein the position sensor comprises a video sensor or a contact sensor.

18. The system of claim 11, wherein the EIT system comprises a breathing sensor configured to provide the at least one parameter associated with the motion.

19. The system of claim 11, comprising a breathing sensing device configured to provide the at least one parameter associated with the motion.

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