Arterial pressure estimation device, arterial pressure estimation system, and arterial pressure estimation method

Abstract

This arterial pressure estimation device is provided with a control unit that, when at least one site of a blood vessel downstream of the aorta is compressed in such a manner as to gradually decrease the pressure, acquires, for each heartbeat, sensor data indicating a timing at which blood flow that has occurred at the at least one site is detected as a blood flow timing, records the value of the pressure corresponding to each blood flow timing, corrects the value of the pressure corresponding to a blood flow timing included in an inhalation period of a respiratory cycle, and estimates a change over time in the arterial pressure by referring to the sensor data acquired and the pressure value recorded and corrected.

Description

[Technical Field]

[0001] The present disclosure relates to an arterial pressure estimation device, an arterial pressure estimation system, and an arterial pressure estimation method. [Background technology]

[0002] Patent Document 1 discloses a technique for estimating left intracardiac pressure from heart sounds, brachial cuff pressure, and K sounds. "K" is an abbreviation for Korotkoff. Patent Document 2 discloses a technique for calculating a pressure equivalent value of respiratory fluctuations. Patent Document 3 discloses a technique for determining the relationship between the average value of the amplitude of multiple arterial pulse waves obtained within a time period equal to or longer than the respiratory cycle and the actual blood pressure value. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] US Patent Application Publication No. 2015 / 0265163 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-137087 [Patent Document 3] Japanese Patent Application Publication No. 1-214338 Summary of the Invention [Problem to be solved by the invention]

[0004] In the treatment of heart failure, left intracardiac pressure is an important observation item. However, directly measuring left intracardiac pressure requires inserting a sensor or other device into the heart, which is highly invasive.

[0005] It is generally known that blood pressure fluctuates with respiration. In the technology disclosed in Patent Document 1, data is collected over multiple beats, so the data includes the influence of such respiratory fluctuations, and the arterial pressure waveform estimated using the data cannot be obtained with sufficient accuracy. In the technology disclosed in Patent Document 2 or Patent Document 3, it is difficult to improve the accuracy of estimating the arterial pressure waveform.

[0006] An object of the present disclosure is to non-invasively and highly accurately estimate changes in arterial blood pressure over time. [Means for solving the problem]

[0007] An arterial pressure estimation device according to one aspect of the present disclosure includes a control unit that acquires sensor data indicating, for each heartbeat, the timing at which blood flow occurring at at least one location in a blood vessel downstream of the aorta is detected while gradually reducing pressure, records the pressure values ​​corresponding to each blood flow timing, corrects the pressure values ​​corresponding to blood flow timings included in the inhalation period of a respiratory cycle, and estimates changes in arterial pressure over time by referring to the acquired sensor data and the recorded and corrected pressure values.

[0008] In one embodiment, the control unit corrects the pressure value corresponding to the blood flow timing included in the inspiration period by weighting the pressure value according to the elapsed time in the inspiration period.

[0009] In one embodiment, the control unit sets the weighting coefficients based on waveform data indicating a blood pressure waveform obtained by performing an invasive test.

[0010] In one embodiment, the sensor data includes data indicating the timing at which the at least one location is compressed multiple times while reducing the pressure at different speeds each time, and the timing at which the blood flow is detected for each heartbeat during each of the multiple compressions as the blood flow timing, and the control unit controls the timing at which the pressure starts to be reduced to match the respiratory cycle.

[0011] In one embodiment, the sensor data includes data indicating the timing at which the blood flow is detected for each heartbeat during compression of the at least one location, with the pressure being reduced at a different rate each time and then reduced at a common rate after the heartbeat at which the blood flow is detected, as the blood flow timing, and the control unit controls the timing at which the pressure reduction begins to coincide with the respiratory cycle.

[0012] In one embodiment, the sensor data includes data indicating the timing at which ejection is detected for each heartbeat as the ejection timing, and the control unit estimates the change in the arterial pressure over time based on the time difference between the ejection timing and the blood flow timing indicated by the sensor data and the pressure value.

[0013] In one embodiment, the control unit estimates the LVEDP based on the estimated change in the arterial blood pressure over time.

[0014] In one embodiment, the control unit estimates an arterial pressure waveform as a change in the arterial pressure over time, estimates a left ventricular pressure waveform based on the estimated arterial pressure waveform, and obtains an estimated value of the LVEDP from the estimated left ventricular pressure waveform.

[0015] In one embodiment, the control unit inputs the estimated result of the change in arterial blood pressure over time into a trained model and obtains the estimated value of the LVEDP from the trained model.

[0016] In one embodiment, the control unit generates a trained model for obtaining the estimated value of the LVEDP by performing machine learning using at least a portion of the estimated result of the change in arterial blood pressure over time.

[0017] In one embodiment, the controller presents the estimated LVEDP to a user.

[0018] In one embodiment, the control unit estimates a parameter related to intracardiac hemodynamics based on the estimated result of the change in arterial pressure over time.

[0019] In one embodiment, the parameter comprises pulmonary artery pressure or pulmonary artery wedge pressure.

[0020] An arterial blood pressure estimation system according to one aspect of the present disclosure includes the arterial blood pressure estimation device and a sensor that detects the blood flow.

[0021] In one embodiment, the arterial blood pressure estimation system further comprises an expansion portion that compresses the at least one location.

[0022] In one aspect of the arterial pressure estimation method of the present disclosure, an expansion section compresses at least one location of a blood vessel downstream of the aorta while gradually reducing the pressure, a sensor detects blood flow occurring at the at least one location with each heartbeat, a control section acquires sensor data indicating the timing at which the blood flow is detected with each heartbeat while the at least one location is compressed as blood flow timing, the control section records the pressure values ​​corresponding to each blood flow timing, the control section corrects the pressure values ​​corresponding to blood flow timings included in the inhalation period of a respiratory cycle, and the control section estimates changes in arterial pressure over time by referring to the acquired sensor data and the recorded and corrected pressure values. [Effects of the Invention]

[0023] According to the present disclosure, it is possible to estimate changes in arterial blood pressure over time non-invasively and with high accuracy. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a block diagram showing a configuration of an arterial blood pressure estimation system according to an embodiment of the present disclosure. FIG. [Figure 2] 1 is a block diagram showing a configuration of an arterial blood pressure estimation device according to an embodiment of the present disclosure. FIG. [Figure 3] 1 is a graph showing an example of respiratory fluctuations in blood pressure. [Figure 4] 1A to 1C are diagrams illustrating examples of a respiratory cycle, cuff pressure, blood pressure waveform, K sound waveform, and electrocardiogram waveform according to an embodiment of the present disclosure. [Figure 5] 1 is a graph showing an example of plotted points and estimated curves in an embodiment of the present disclosure. [Figure 6] 1 is a flowchart illustrating the operation of an arterial blood pressure estimation system according to an embodiment of the present disclosure. [Figure 7] 7 is a flowchart showing the procedure of the measurement process shown in FIG. 6. [Figure 8] 10 is a graph showing an example of plotted points in a variation of an embodiment of the present disclosure. [Figure 9] 10 is a flowchart illustrating the operation of an arterial blood pressure estimation system according to a modified example of an embodiment of the present disclosure. [Figure 10A] 10A and 10B are diagrams showing waveforms of arterial pressure, left ventricular pressure, and heart sounds near the aortic valve according to a comparative example. [Figure 10B] FIG. 10B is a diagram showing the blood flow corresponding to FIG. 10A. [Figure 11A] 10A and 10B are diagrams showing an arterial pressure waveform near the aortic valve, a left ventricular pressure waveform, a heart sound waveform, and an arterial pressure waveform in the upper arm according to a comparative example. [Figure 11B] FIG. 11B is a diagram showing the blood flow corresponding to FIG. 11A. [Figure 12A] 10A and 10B are diagrams showing an arterial pressure waveform near the aortic valve, a left ventricular pressure waveform, a heart sound waveform, and an arterial pressure waveform in the upper arm according to a comparative example. [Figure 12B] FIG. 12B is a diagram showing the blood flow corresponding to FIG. 12A. [Figure 13A] 10A and 10B are diagrams showing an arterial pressure waveform near the aortic valve, a left ventricular pressure waveform, a cardiac sound waveform, an arterial pressure waveform in the upper arm, an electrocardiogram waveform, and a first K sound waveform in the upper arm according to a comparative example. [Figure 13B] FIG. 13B is a diagram showing the blood flow corresponding to FIG. 13A. [Figure 14] 10A and 10B are diagrams showing an arterial pressure waveform near the aortic valve, a left ventricular pressure waveform, a cardiac sound waveform, an arterial pressure waveform in the upper arm, an electrocardiogram waveform, and a first K sound waveform in the upper arm according to a comparative example. [Figure 15]FIG. 10 shows an arterial pressure waveform near the aortic valve, a left ventricular pressure waveform, a cardiac sound waveform, an upper arm arterial pressure waveform, an electrocardiogram waveform, an upper arm first K sound waveform, an estimated arterial pressure waveform, and a fitted curve in a comparative example. [Figure 16] FIG. 10 shows an arterial pressure waveform near the aortic valve, a left ventricular pressure waveform, a cardiac sound waveform, an upper arm arterial pressure waveform, an electrocardiogram waveform, an upper arm first K sound waveform, an estimated arterial pressure waveform, a fitted curve, and an estimated LVEDP in a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0025] As a comparative example, a method for estimating left intracardiac pressure from an arterial pressure waveform, similar to the technique disclosed in Patent Document 1, will be described below with reference to the drawings.

[0026] As shown in Figures 10A and 10B, as the pressure in the left ventricle 16 rises, the aortic valve 17 opens and blood flows into the aorta 18. As shown in Figures 11A and 11B, the blood flow that has passed through the aortic valve 17 reaches the upper arm, or arm 13, with a delay. The arterial pressure waveform in the arm 13 is a curve that is obtained by shifting the arterial pressure waveform near the aortic valve 17 by the amount of delay.

[0027] As shown in FIGS. 12A and 12B, when the cuff pressure is high, blood does not flow to the arm 13. The cuff pressure is the pressure of a cuff 90 attached to the arm 13. The cuff 90 incorporates a first K-sound microphone 91, a second K-sound microphone 92, and a pressure sensor 93. As shown in FIGS. 13A and 13B, as the cuff pressure is reduced while recording an electrocardiogram waveform and waiting for a K-sound, blood begins to flow to the arm 13. When the K-sound generated by blood flow is captured by the first K-sound microphone 91, the time interval from the Q wave to the K-sound and the cuff pressure measured by the pressure sensor 93 are recorded. Instead of the time interval from the Q wave to the K-sound, the time interval from the heart sound to the K-sound may be recorded. The distance between the first K-sound microphone 91 and the second K-sound microphone 92 is known, and is, for example, approximately 3 cm to 5 cm. The delay between the aortic valve 17 and the first K sound microphone 91 is calculated based on the difference in timing at which signals enter the first K sound microphone 91 and the second K sound microphone 92 and the distance between the aortic valve 17 and the first K sound microphone 91.

[0028] As shown in Figure 14, further decreasing the cuff pressure advances the onset timing of the K sound in subsequent heartbeats. For each heartbeat, when the K sound is captured by the first K sound microphone 91, the time interval from the Q wave to the K sound and the cuff pressure measured by the pressure sensor 93 are recorded. Instead of the time interval from the Q wave to the K sound, the time interval from the heart sound to the K sound may be recorded. As shown in Figure 15, a curve, such as a polynomial or cosine curve, is fitted to the record of the time interval and cuff pressure. Ideally, this curve would have the same waveform as the left ventricular pressure waveform, but this is difficult in reality. As shown in Figure 16, the pressure value at a delay from the timing of the Q wave is the estimated LVEDP. "LVEDP" is an abbreviation for left ventricular end-diastolic pressure.

[0029] As described above, in the method of gradually decreasing the cuff pressure for each heartbeat and completing the acquisition of information on arterial pressure over multiple heartbeats, the reproducibility of the estimated arterial pressure waveform cannot be sufficiently obtained due to the influence of respiratory variation. Therefore, in the present disclosure, the reproducibility of the estimated arterial pressure waveform is improved by correcting the cuff pressure value obtained for each heartbeat in accordance with the respiratory cycle.

[0030] Hereinafter, several embodiments of the present disclosure will be described with reference to the drawings.

[0031] In each drawing, the same or corresponding parts are denoted by the same reference numerals. In the description of each embodiment, the description of the same or corresponding parts will be omitted or simplified as appropriate.

[0032] An embodiment of the present disclosure will be described.

[0033] The outline of this embodiment will be described with reference to FIGS.

[0034] In the arterial pressure estimation system 10 according to this embodiment, the expansion section compresses at least one location of the blood vessel 12 downstream of the aorta 18 while gradually reducing the pressure. The blood flow sensor 42 detects blood flow occurring at the at least one location with each heartbeat. The control unit 21 acquires sensor data 44 indicating the timing at which blood flow is detected with each heartbeat while the at least one location is compressed, as blood flow timing. The control unit 21 records pressure values ​​corresponding to each blood flow timing. The control unit 21 corrects pressure values ​​corresponding to blood flow timings included in the inhalation period of a respiratory cycle. The control unit 21 estimates changes in arterial pressure over time by referring to the acquired sensor data 44 and the recorded and corrected pressure values.

[0035] According to this embodiment, the influence of respiratory variation can be suppressed, and therefore, the change in arterial pressure over time can be estimated non-invasively and with high accuracy.

[0036] In this embodiment, a cuff 31 is used as the inflation unit. The cuff 31 is attached to the arm 13 and compresses one location on the blood vessel 12. The control unit 21 estimates an arterial pressure waveform 15 as a change in arterial pressure over time. According to this embodiment, the reproducibility of the estimated arterial pressure waveform 15 can be improved by correcting the value of the cuff pressure obtained for each beat in accordance with the respiratory cycle. In a variation of this embodiment, the inflation unit may be an airbag instead of the cuff 31.

[0037] The configuration of an arterial blood pressure estimation system 10 according to this embodiment will be described with reference to FIG.

[0038] The arterial blood pressure estimation system 10 includes an arterial blood pressure estimation device 20, a cuff control device 30, a cuff 31, a pulse output sensor 40, a cuff pressure sensor 41, and a blood flow sensor .

[0039] The arterial blood pressure estimation device 20 is a computer. The arterial blood pressure estimation device 20 is, for example, a dedicated device, a general-purpose device such as a PC, or a server device belonging to a cloud computing system or other computing system. "PC" is an abbreviation for personal computer.

[0040] The cuff control device 30 is a device that controls the cuff 31. The cuff control device 30 can communicate with the arterial blood pressure estimation device 20 directly or via a network such as a LAN or the Internet. "LAN" is an abbreviation for local area network.

[0041] The ejection sensor 40 is a sensor that detects the ejection of the heart 11. In this embodiment, the ejection sensor 40 is an ECG sensor, but it may also be a sound sensor that detects the closure sound of the mitral valve. "ECG" is an abbreviation for electrocardiogram. The ejection sensor 40 can communicate with the arterial blood pressure estimation device 20 directly or via a network such as a LAN or the Internet.

[0042] The cuff pressure sensor 41 detects the pressure of the cuff 31, i.e., the cuff pressure. The cuff pressure sensor 41 can communicate with the arterial blood pressure estimation device 20 directly or via a network such as a LAN or the Internet. In a modification of this embodiment, the cuff pressure sensor 41 may be integrated with the cuff 31.

[0043] The blood flow sensor 42 detects blood flow occurring at the portion of the blood vessel 12 compressed by the cuff 31. In this embodiment, the blood flow sensor 42 is attached to the arm 13 downstream of the cuff 31 and is a sound sensor that detects sound generated by blood flowing downstream of the cuff 31. However, the blood flow sensor 42 may be a PPG sensor or an ultrasonic sensor that measures blood flow using the ultrasonic Doppler method. "PPG" is an abbreviation for photoplethysmogram. The blood flow sensor 42 can communicate with the arterial blood pressure estimation device 20 directly or via a network such as a LAN or the Internet. In one variation of this embodiment, the blood flow sensor 42 may be integrated with the cuff 31.

[0044] The arterial blood pressure estimation device 20 acquires, as sensor data 44, signals output from the pumping sensor 40, the cuff pressure sensor 41, and the blood flow sensor 42 when the cuff 31 compresses a location on the blood vessel 12 while gradually decreasing the cuff pressure under control of the cuff control device 30. The sensor data 44 is data indicating the pumping timing Ti, the pressure Pi, and the blood flow timing Fi for each heartbeat i, where i=1, 2, . . . , n, where n is an integer equal to or greater than 2, such as 10. The pumping timing Ti is the timing at which the pumping is detected by the pumping sensor 40. The pumping timing Ti is treated as the reference timing of the heart 11. The reference timing is a timing that can be identified for each heartbeat i. The pressure Pi is the cuff pressure detected by the cuff pressure sensor 41. The blood flow timing Fi is the timing at which the blood flow is detected by the blood flow sensor 42.

[0045] The arterial blood pressure estimation device 20 refers to the sensor data 44, calculates the time difference Di from the pumping timing Ti to the blood flow timing Fi, and records the value of the pressure Pi corresponding to the blood flow timing Fi. As shown in FIG. 3, during the inhalation period of the respiratory cycle, fluctuations occur in the blood pressure waveform in the direction of decreasing blood pressure. As a result, as shown in FIG. 4, a delay due to the fluctuation occurs in the blood flow timing included in the inhalation period. Therefore, the arterial blood pressure estimation device 20 corrects the value of the cuff pressure corresponding to the blood flow timing included in the inhalation period, as shown in FIG. 5.

[0046] The arterial pressure estimation device 20 estimates an arterial pressure waveform 15 from the time differences D1, D2, . . . , Dn and the corresponding pressure values ​​P1, P2, . . . , Pn. Of the pressure values ​​P1, P2, . . . , Pn, corrected values ​​are used as values ​​corresponding to the blood flow timing included in the inspiration period. The estimated arterial pressure waveform 15 corresponds to the arterial pressure waveform of the aorta 18. Therefore, the arterial pressure estimation device 20 estimates the LVEDP from the estimated arterial pressure waveform 15.

[0047] According to this embodiment, the LVEDP value estimated by the arterial blood pressure estimation device 20 can be used to provide an important judgment index in the treatment of heart failure. Based on this index, it is possible to make decisions regarding prescription changes for diuretics and the like, as well as decisions regarding hospitalization, outpatient care, or discharge. Regarding prescription changes, a prescription can be issued and medication instructions can be given to the patient based on a doctor's confirmation and judgment of the data remotely or during an outpatient visit. Regarding decisions regarding hospitalization, outpatient care, or discharge, a certain threshold may be set, and a display suggesting hospitalization or outpatient care may be displayed if the LVEDP value is abnormal, or suggesting discharge if the value is normal. If the LVEDP value is abnormal, an alert may be sent to the user or the doctor. The arterial blood pressure estimation device 20 can also be used for remote medical care.

[0048] The configuration of the arterial blood pressure estimation device 20 according to this embodiment will be described with reference to FIG.

[0049] The arterial blood pressure estimation device 20 includes a control unit 21, a storage unit 22, a communication unit 23, an input unit 24, and an output unit 25.

[0050] The control unit 21 includes at least one processor, at least one programmable circuit, at least one dedicated circuit, or any combination thereof. The processor is a general-purpose processor such as a CPU or GPU, or a dedicated processor specialized for specific processing. "CPU" is an abbreviation for central processing unit. "GPU" is an abbreviation for graphics processing unit. An example of the programmable circuit is an FPGA. "FPGA" is an abbreviation for field-programmable gate array. An example of the dedicated circuit is an ASIC. "ASIC" is an abbreviation for application specific integrated circuit. The control unit 21 controls each part of the arterial blood pressure estimation device 20 and executes processing related to the operation of the arterial blood pressure estimation device 20.

[0051] The storage unit 22 includes at least one semiconductor memory, at least one magnetic memory, at least one optical memory, or any combination thereof. The semiconductor memory is, for example, RAM or ROM. "RAM" is an abbreviation for random access memory. "ROM" is an abbreviation for read only memory. RAM is, for example, SRAM or DRAM. "SRAM" is an abbreviation for static random access memory. "DRAM" is an abbreviation for dynamic random access memory. ROM is, for example, EEPROM. "EEPROM" is an abbreviation for electrically erasable programmable read only memory. The storage unit 22 functions as, for example, a main storage device, an auxiliary storage device, or a cache memory. The storage unit 22 stores data used in the operation of the arterial blood pressure estimation device 20 and data obtained by the operation of the arterial blood pressure estimation device 20.

[0052] The communication unit 23 includes at least one communication interface. The communication interface is, for example, a LAN interface, an interface compatible with a mobile communication standard such as LTE, the 4G standard, or the 5G standard, or an interface compatible with a short-range wireless communication standard such as Bluetooth (registered trademark). "LTE" is an abbreviation for Long Term Evolution. "4G" is an abbreviation for 4th generation. "5G" is an abbreviation for 5th generation. The communication unit 23 receives data used in the operation of the arterial blood pressure estimation device 20 and transmits data obtained by the operation of the arterial blood pressure estimation device 20.

[0053] The input unit 24 includes at least one input interface. The input interface may be, for example, a physical key, a capacitance key, a pointing device, a touch screen integrated with a display, an imaging device such as a camera, or a microphone. The input unit 24 accepts an operation to input data used for the operation of the arterial blood pressure estimation device 20. The input unit 24 may be connected to the arterial blood pressure estimation device 20 as an external input device, instead of being provided in the arterial blood pressure estimation device 20. The connection interface may be, for example, an interface compatible with standards such as USB, HDMI (registered trademark), or Bluetooth (registered trademark). "USB" is an abbreviation for Universal Serial Bus. "HDMI (registered trademark)" is an abbreviation for High-Definition Multimedia Interface.

[0054] The output unit 25 includes at least one output interface. The output interface is, for example, a display or a speaker. The display is, for example, an LCD or an organic EL display. "LCD" is an abbreviation for liquid crystal display. "EL" is an abbreviation for electroluminescence. The output unit 25 outputs data obtained by the operation of the arterial blood pressure estimation device 20. The output unit 25 may be connected to the arterial blood pressure estimation device 20 as an external output device instead of being provided in the arterial blood pressure estimation device 20. The connection interface may be, for example, an interface compatible with standards such as USB, HDMI (registered trademark), or Bluetooth (registered trademark).

[0055] The functions of the arterial blood pressure estimation device 20 are realized by executing a program according to this embodiment on a processor serving as the control unit 21. That is, the functions of the arterial blood pressure estimation device 20 are realized by software. The program causes a computer to execute the operations of the arterial blood pressure estimation device 20, thereby causing the computer to function as the arterial blood pressure estimation device 20. That is, the computer functions as the arterial blood pressure estimation device 20 by executing the operations of the arterial blood pressure estimation device 20 in accordance with the program.

[0056] The program can be stored on a non-transitory computer-readable medium. Examples of non-transitory computer-readable media include flash memory, magnetic recording devices, optical disks, magneto-optical recording media, and ROMs. The program can be distributed by selling, transferring, or lending portable media such as SD cards, DVDs, or CD-ROMs that store the program. "SD" is an abbreviation for Secure Digital. "DVD" is an abbreviation for digital versatile disc. "CD-ROM" is an abbreviation for compact disc read only memory. The program can also be distributed by storing it in the storage of a server and transferring it from the server to another computer. The program can also be provided as a program product.

[0057] A computer temporarily stores a program stored on a portable medium or transferred from a server in its main storage device. The computer then reads the program stored in the main storage device using a processor and executes processing in accordance with the read program. The computer may also read the program directly from a portable medium and execute processing in accordance with the program. The computer may also execute processing in accordance with the received program each time a program is transferred from a server to the computer. Processing may also be executed through a so-called ASP-type service that achieves its functions by issuing execution instructions and obtaining results without transferring the program from the server to the computer. "ASP" is an abbreviation for application service provider. A program is information used for processing by a computer and includes something equivalent to a program. For example, data that is not a direct instruction to a computer but has properties that specify computer processing falls under the category of "something equivalent to a program."

[0058] Some or all of the functions of the arterial blood pressure estimation device 20 may be realized by a programmable circuit or a dedicated circuit as the control unit 21. In other words, some or all of the functions of the arterial blood pressure estimation device 20 may be realized by hardware.

[0059] The operation of the arterial blood pressure estimation system 10 according to this embodiment will be described with reference to Fig. 6. This operation corresponds to the arterial blood pressure estimation method according to this embodiment.

[0060] In step S101, the cuff control device 30 inflates the cuff 31 to an initial pressure. The initial pressure may be approximately the same as the initial pressure in general non-invasive blood pressure measurement. The process of step S101 may be triggered by a command from the arterial blood pressure estimation device 20 to the cuff control device 30.

[0061] In step S102, the cuff control device 30 starts depressurizing the cuff 31. The cuff control device 30 gradually reduces the cuff pressure at a constant depressurization rate V. The depressurization rate V may be any rate, but is 3 mmHg / second in this embodiment. The processing of step S102 may be triggered by a command from the arterial blood pressure estimation device 20 to the cuff control device 30.

[0062] In step S103, the measurement process shown in FIG. 7 is executed.

[0063] In step S111, the pumping sensor 40 detects the pumping of the heart 11. Specifically, the pumping sensor 40 measures an electrocardiogram waveform. The pumping sensor 40 outputs a signal indicating the measured electrocardiogram waveform.

[0064] In step S112, the blood flow sensor 42 detects blood flow occurring in a portion of the blood vessel 12 downstream of the aorta 18 that is compressed by the cuff 31. Specifically, the blood flow sensor 42 detects a K sound that occurs when blood flow breaks through the cuff 31. The blood flow sensor 42 outputs a signal indicating the waveform of the K sound.

[0065] In step S113, the cuff pressure sensor 41 detects the cuff pressure as a pressure Pi and outputs a signal indicating the pressure Pi.

[0066] In step S114, the control unit 21 of the arterial blood pressure estimation device 20 acquires sensor data 44. The sensor data 44 includes data indicating, for heartbeat i, the timing at which pumping was detected in step S111 as pumping timing Ti. Specifically, the sensor data 44 includes, as such data, data indicating an electrocardiogram waveform measured by the pumping sensor 40. The sensor data 44 further includes, for heartbeat i, data indicating, for heartbeat i, the timing at which blood flow was detected in step S112 as blood flow timing Fi. Specifically, the sensor data 44 includes, as such data, data indicating the waveform of the K sound detected by the blood flow sensor 42. The sensor data 44 further includes, for heartbeat i, the value of pressure Pi detected in step S113. The control unit 21 stores the sensor data 44 in the memory unit 22, thereby recording the value of pressure Pi in association with the blood flow timing Fi. The control unit 21 determines whether the pressure Pi is equal to or lower than the diastolic blood pressure. The diastolic blood pressure may be determined by any method, but in this embodiment, it is determined by a method commonly used in sphygmomanometers, such as the oscillometric method or the Liber-Rocchi-Korotkoff method. For example, the diastolic blood pressure can be determined by detecting the timing at which the K sound generated during decompression disappears. If the pressure Pi is equal to or less than the diastolic blood pressure, the processes of steps S115 to S117 are executed. If the pressure Pi is not equal to or less than the diastolic blood pressure, the processes of steps S111 to S114 are executed again.

[0067] In step S115, the control unit 21 of the arterial blood pressure estimation device 20 calculates the time difference Di between the pumping timing Ti and the blood flow timing Fi indicated by the sensor data 44. Specifically, the control unit 21 identifies the pumping timing Ti from the electrocardiogram waveform measured by the pumping sensor 40. The control unit 21 identifies the timing at which blood breaks through the cuff 31 as the blood flow timing Fi from the waveform of the K sound detected by the blood flow sensor 42. The control unit 21 calculates the difference between the identified timings as the time difference Di.

[0068] The ejection timing Ti may be determined from heart sounds instead of electrocardiogram waveforms. In this case, in step S111, the ejection sensor 40 detects heart sounds including mitral valve closure sounds. The ejection sensor 40 outputs a signal indicating the detected heart sounds. In step S114, the sensor data 44 includes data indicating the heart sounds detected by the ejection sensor 40. The control unit 21 of the arterial blood pressure estimation device 20 determines the ejection timing Ti from the heart sounds detected by the ejection sensor 40.

[0069] In step S116, the control unit 21 of the arterial blood pressure estimation device 20 estimates the respiratory cycle. Specifically, the control unit 21 estimates the respiratory cycle from the electrocardiogram waveform measured by the ejection sensor 40 in step S111 using the method disclosed in Japanese Patent Application Laid-Open No. 2018-011753 or any other method. Alternatively, the control unit 21 may estimate the respiratory cycle from heart sounds using the method disclosed in Japanese Patent Application Laid-Open No. 2012-249730 or any other method. Alternatively, the control unit 21 may estimate the respiratory cycle from pulse pressure or using PPG or millimeter-wave radar.

[0070] In step S117, the control unit 21 of the arterial blood pressure estimation device 20 corrects, from among the pressure values ​​P1, P2, . . . , Pn recorded in step S114, the pressure values ​​corresponding to the blood flow timings included in the inhalation period of the respiratory cycle estimated in step S116. Specifically, the control unit 21 corrects the pressure values ​​corresponding to the blood flow timings included in the inhalation period by weighting them according to the elapsed time in the inhalation period. That is, the control unit 21 corrects the blood pressure values ​​measured during inhalation with a value calculated using a weighting coefficient tailored to the respiratory waveform. In this embodiment, the control unit 21 corrects the cuff pressure value during inhalation by adding a correction value y calculated using the following equation to the cuff pressure value during inhalation. y=A·sin(2πft)

[0071] The weighting coefficient A corresponds to the correction value range. The weighting coefficient A is set to, for example, 10 mmHg. The control unit 21 may set the weighting coefficient based on waveform data indicating a blood pressure waveform obtained by an invasive test. That is, the correction value range may be determined based on the blood pressure waveform obtained by an invasive test. In this case, the input unit 24 of the arterial blood pressure estimation device 20 may be used as an interface for inputting the blood pressure waveform. The weighting may be optimized by machine learning. That is, a trained model may be constructed that receives input of a blood pressure waveform and a respiratory cycle and outputs a weighting coefficient A, and the weighting coefficient A may be determined using this trained model. The frequency f corresponds to the reciprocal of the respiratory cycle. The time t is the elapsed time from the start of inspiration to the blood flow timing. For example, if A = 10 mmHg, f = 0.2 Hz, and t = 0.5 seconds, then y = 10 sin(2π × 0.2 × 0.5) ≒ 5.9 mmHg.

[0072] In step S104, the control unit 21 of the arterial blood pressure estimation device 20 generates plot data by referring to the sensor data 44 acquired in step S103 and the pressure values ​​recorded and corrected in step S103. Specifically, for each heartbeat i, the control unit 21 plots the time difference Di calculated in step S115 and the corrected pressure Pi value if the pressure Pi value was corrected in step S117, or the uncorrected pressure Pi value if no correction was made, i.e., the pressure Pi value recorded in step S114. The control unit 21 stores the obtained plot data in the storage unit 22.

[0073] In step S105, the control unit 21 of the arterial blood pressure estimation device 20 estimates the change in arterial pressure over time based on the plot data obtained in step S104. That is, the control unit 21 estimates the change in arterial pressure over time according to the time difference Di between the ejection timing Ti and the blood flow timing Fi indicated by the sensor data 44 and the value of the pressure Pi. Specifically, the control unit 21 performs spline interpolation on the plotted points to estimate the curve of the arterial pressure waveform 15.

[0074] In step S106, the control unit 21 of the arterial blood pressure estimation device 20 estimates the LVEDP based on the estimated result of the time-dependent change in arterial pressure obtained in step S105. Specifically, the control unit 21 estimates a left ventricular pressure waveform in accordance with the arterial pressure waveform 15 estimated in step S105. The method for estimating the left ventricular pressure waveform can be, for example, the same method as in the comparative example. The control unit 21 obtains an estimated value of the LVEDP from the estimated left ventricular pressure waveform.

[0075] In step S107, the control unit 21 of the arterial blood pressure estimation device 20 presents the estimated LVEDP acquired in step S106 to the user. Specifically, the control unit 21 displays the estimated LVEDP on a display serving as the output unit 25. Alternatively, the control unit 21 may output the estimated LVEDP as sound from a speaker serving as the output unit 25. Alternatively, the control unit 21 may cause the communication unit 23 to transmit the estimated LVEDP to a user's terminal device, such as a mobile device such as a mobile phone, smartphone, or tablet, or a PC, directly or via a network such as a LAN or the Internet, and cause the terminal device to present the estimated LVEDP.

[0076] As described above, in this embodiment, the control unit 21 of the arterial blood pressure estimation device 20 acquires sensor data 44 indicating the timing at which blood flow is detected at at least one location downstream of the aorta 18 for each heartbeat while gradually reducing the pressure at that location, and records the pressure value corresponding to each blood flow timing. The control unit 21 corrects the pressure value corresponding to the blood flow timing included in the inspiration period of the respiratory cycle. The control unit 21 estimates the change in arterial pressure over time by referring to the acquired sensor data 44 and the recorded and corrected pressure values.

[0077] According to this embodiment, the influence of respiratory variation can be suppressed, and therefore, the change in arterial pressure over time can be estimated non-invasively and with high accuracy.

[0078] As shown in FIG. 1, the arterial pressure estimation system 10 includes at least one cuff 31, a cuff control device 30, a blood flow sensor 42 such as a K sound sensor, a pulse pressure sensor, a PPG sensor, or an ultrasonic Doppler sensor, a cuff pressure sensor 41, an output sensor 40 such as an ECG sensor or a heart sound sensor, and an arterial pressure estimation device 20.

[0079] The cuff 31 compresses the blood vessel 12 to block blood flow. The cuff control device 30 inflates the cuff 31 to an initial pressure and then depressurizes it. The blood flow sensor 42 detects the timing when blood flow occurs while the cuff 31 is being depressurized. The cuff pressure sensor 41 detects the cuff pressure at the timing when blood flow occurs. The ejection sensor 40 detects the ejection timing of the heart 11.

[0080] The arterial pressure estimation device 20 estimates the respiratory cycle from an ECG or heart sounds. The arterial pressure estimation device 20 corrects the cuff pressure value obtained for each beat according to the respiratory cycle. The arterial pressure estimation device 20 calculates the time difference between the pumping timing of the heart 11 and the timing when blood flow occurs. The arterial pressure estimation device 20 estimates at least a part of the arterial pressure waveform 15 based on the time difference and the corrected cuff pressure value.

[0081] According to this embodiment, the reproducibility of the estimated arterial pressure waveform 15 can be improved.

[0082] As a modification of this embodiment, the control unit 21 of the arterial blood pressure estimation device 20 may detect the respiratory cycle by measuring the respiratory flow or by using a belt-type respiratory sensor worn around the chest or abdomen, instead of estimating the respiratory cycle. Alternatively, the control unit 21 may instruct the timing of breathing during the measurement process, or may forcibly control breathing in conjunction with a CPAP device or a ventilator. "CPAP" is an abbreviation for continuous positive airway pressure. If there is no need to estimate or detect the respiratory cycle, the measurement process can be sped up.

[0083] As a modified example of this embodiment, the control unit 21 of the arterial blood pressure estimation device 20 may input the plot data obtained in step S104 into a trained model and estimate the LVEDP using the trained model, instead of estimating the curve of the arterial pressure waveform 15. That is, the control unit 21 may input the estimated result of the change in arterial pressure over time into the trained model and obtain an estimated value of the LVEDP from the trained model.

[0084] As a modified example of this embodiment, the control unit 21 of the arterial blood pressure estimation device 20 may construct a trained model for estimating LVEDP using at least a portion of the arterial pressure waveform 15. For example, the control unit 21 may construct a trained model that uses the maximum slope of the rising edge of the arterial pressure waveform 15 as one of the explanatory variables. The control unit 21 may estimate the LVEDP using this trained model from the next time onwards. That is, the control unit 21 may generate a trained model for obtaining an estimated value of LVEDP by performing machine learning using at least a portion of the estimation results of the change in arterial pressure over time. The control unit 21 may store the generated trained model in the storage unit 22 so that it can be used in the future.

[0085] As a modification of this embodiment, the measurement process may be performed multiple times in order to efficiently collect plot data. Such a modification will now be described.

[0086] In this modified example, the decompression start timing is synchronized with the respiratory cycle, and remeasurements are continuously repeated, changing the decompression speed each time, thereby increasing the number of plots that make up the waveform, as shown in FIG.

[0087] The operation of the arterial blood pressure estimation system 10 according to this modification will be described with reference to Fig. 9. This operation corresponds to the arterial blood pressure estimation method according to this modification.

[0088] In step S201, the ejection sensor 40 starts detecting the ejection of the heart 11, and thereafter repeatedly detects the ejection of the heart 11. Specifically, the ejection sensor 40 repeatedly measures an electrocardiogram waveform. Each time the ejection sensor 40 measures an electrocardiogram waveform, it outputs a signal indicating the electrocardiogram waveform.

[0089] The process in step S202 is the same as the process in step S101, and therefore a description thereof will be omitted.

[0090] In step S203, the control unit 21 of the arterial blood pressure estimation device 20 estimates the respiratory cycle. Specifically, the control unit 21 estimates the respiratory cycle from the electrocardiogram waveform measured by the ejection sensor 40 in step S201 using the same method as in step S116. Alternatively, the control unit 21 may estimate the respiratory cycle from heart sounds or pulse pressure, or by using PPG or millimeter-wave radar.

[0091] In step S204, the cuff control device 30 starts depressurizing the cuff 31. The cuff control device 30 gradually reduces the cuff pressure at a constant depressurization rate V. The depressurization rate V may be any rate, but is set to 3 mmHg / second in this modification. In this modification, the processing of step S204 is triggered by a command from the arterial blood pressure estimation device 20 to the cuff control device 30. Specifically, the control unit 21 of the arterial blood pressure estimation device 20 causes the cuff control device 30 to start depressurization in synchronization with the exhalation timing of the respiratory cycle estimated in step S203.

[0092] The processing in steps S205 and S206 is the same as the processing in steps S103 and S104, and therefore a description thereof will be omitted.

[0093] In step S207, the control unit 21 of the arterial blood pressure estimation device 20 determines whether the number of times the measurement process has been executed has reached a specified number. The specified number may be any number equal to or greater than two, but is three in this modified example. If the number of times the measurement process has been executed has reached the specified number, the processes of steps S209 to S211 are executed. If the number of times the measurement process has been executed has not reached the specified number, the process of step S208 is executed.

[0094] In step S208, the cuff control device 30 inflates the cuff 31 again to the initial pressure and then starts depressurizing the cuff 31. As in step S202, the cuff control device 30 gradually reduces the cuff pressure at a constant depressurization rate V. However, the depressurization rate V is faster than the rate when the measurement process was last performed. In this modification, the depressurization rate V is 1 mmHg / sec faster than the previous rate. That is, the depressurization rate V is 4 mmHg / sec when the measurement process is performed for the second time and 5 mmHg / sec when the measurement process is performed for the third time. Like the process in step S202, the process in step S208 is triggered by a command from the arterial blood pressure estimation device 20 to the cuff control device 30. Specifically, the control unit 21 of the arterial blood pressure estimation device 20 causes the cuff control device 30 to start depressurization in synchronization with the exhalation timing of the most recently estimated respiratory cycle. After step S208, the processes in steps S205 to S207 are executed again.

[0095] The processing from step S209 to step S211 is the same as the processing from step S105 to step S107, and therefore a description thereof will be omitted.

[0096] As described above, in this modification, the cuff 31 compresses one location on the blood vessel 12 multiple times while reducing the cuff pressure at different speeds each time under the control of the cuff control device 30. The sensor data 44 includes data indicating, as blood flow timing, the timing at which blood flow is detected for each heartbeat during each of the multiple compressions. The control unit 21 of the arterial blood pressure estimation device 20 controls the timing at which the pressure starts to be reduced to coincide with the respiratory cycle.

[0097] According to this modification, by increasing the number of samples, it is possible to estimate the change in arterial blood pressure over time with higher accuracy.

[0098] As a further modification of this modification, a different depressurization rate may be applied each time remeasurement is performed until blood flow is first detected, and the same depressurization rate may be applied each time after blood flow is detected. That is, in the process of step S205 executed after the process of step S208, the depressurization rate set in the process of the immediately preceding step S208 may be applied until blood flow timing F1, and the depressurization rate set in the process of step S204 may be applied after blood flow timing F1. For example, in step S208, the cuff control device 30 may again inflate the cuff 31 to the initial pressure and then begin depressurizing the cuff 31 at a rate 1 mmHg / sec faster than the previous rate. Then, in step S205, after the first step S112, i.e., once blood flow is detected, the cuff control device 30 gradually reduces the cuff pressure at the same rate as the initial rate.

[0099] As described above, the cuff 31 may compress one point of the blood vessel 12 multiple times by starting to lower the cuff pressure at different rates each time under the control of the cuff control device 30, and then lowering the cuff pressure at a common rate after the heartbeat at which blood flow is detected.

[0100] The present disclosure is not limited to the above-described embodiments. For example, two or more blocks shown in the block diagrams may be integrated, or one block may be divided. Two or more steps shown in the flowcharts may be executed in parallel or in a different order, instead of being executed in chronological order as described, depending on the processing capabilities of the device executing each step, or as needed. Other modifications are possible within the scope of the present disclosure.

[0101] For example, the control unit 21 of the arterial pressure estimation device 20 may estimate hemodynamic parameters other than LVEDP based on the estimated results of changes in arterial pressure over time. Hemodynamic parameters refer to parameters related to intracardiac hemodynamics, such as LVEDP, pulmonary artery pressure, or pulmonary artery wedge pressure. Pulmonary artery pressure is also abbreviated as "PAP." Pulmonary artery wedge pressure is also abbreviated as "PWP," and is also referred to as pulmonary arterial wedge pressure or abbreviated as "PAWP," pulmonary capillary wedge pressure or abbreviated as "PCWP," or pulmonary artery occlusion pressure or abbreviated as "PAOP." The control unit 21 may generate a trained model for obtaining estimated values ​​of hemodynamic parameters other than LVEDP by performing machine learning using at least a portion of the estimated results of changes in arterial pressure over time. The control unit 21 may present estimated values ​​of hemodynamic parameters other than LVEDP to a user.

[0102] In a specific example in which pulmonary artery pressure is estimated as a hemodynamic parameter, control unit 21 of arterial pressure estimation device 20 estimates an arterial pressure waveform as a change in arterial pressure over time. Control unit 21 estimates a pulmonary artery pressure waveform according to the estimated arterial pressure waveform. Control unit 21 obtains an estimated value of pulmonary artery pressure from the estimated pulmonary artery pressure waveform. Alternatively, instead of estimating a pulmonary artery pressure waveform, control unit 21 may input the estimated result of the change in arterial pressure over time into a trained model and obtain an estimated value of pulmonary artery pressure from the trained model.

[0103] In a specific example in which pulmonary artery wedge pressure is estimated as a hemodynamic parameter, control unit 21 of arterial pressure estimation device 20 estimates an arterial pressure waveform as a change in arterial pressure over time. Control unit 21 estimates a pulmonary artery wedge pressure waveform, a right atrial pressure waveform, or a right ventricular pressure waveform according to the estimated arterial pressure waveform. Control unit 21 obtains an estimated value of pulmonary artery wedge pressure from the estimated pulmonary artery wedge pressure waveform, right atrial pressure waveform, or right ventricular pressure waveform. Alternatively, instead of estimating a pulmonary artery wedge pressure waveform, right atrial pressure waveform, or right ventricular pressure waveform, control unit 21 may input the estimated result of the change in arterial pressure over time into a trained model and obtain an estimated value of pulmonary artery wedge pressure from the trained model. [Explanation of symbols]

[0104] 10 Arterial Pressure Estimation System 11 Heart 12 Blood vessels 13 Arms 15 Arterial pressure waveform 16 Left ventricle 17 Aortic valve 18 aorta 20 Arterial pressure estimation device 21 Control section 22 Memory section 23 Communications Department 24 Input section 25 Output section 30 Cuff control device 31 Cuff 40 Pumping Sensor 41 Cuff pressure sensor 42 Blood flow sensor 44 Sensor Data 90 Cuff 91 1st K sound microphone 92 2nd K sound microphone 93 Pressure Sensor

Claims

1. An arterial pressure estimation device comprising: a control unit that acquires sensor data indicating the timing at which blood flow occurring at at least one location downstream of the aorta is detected for each heartbeat while compressing the at least one location while gradually reducing the pressure; records the pressure values ​​corresponding to each blood flow timing; corrects the pressure values ​​corresponding to blood flow timings included in the inhalation period of a respiratory cycle; and estimates changes in arterial pressure over time by referring to the acquired sensor data and the recorded and corrected pressure values.

2. The arterial blood pressure estimation device according to claim 1 , wherein the control unit corrects the pressure value corresponding to the blood flow timing included in the inspiration period by weighting the pressure value according to the elapsed time in the inspiration period.

3. The arterial blood pressure estimation device according to claim 2 , wherein the control unit sets the weighting coefficients based on waveform data representing a blood pressure waveform obtained by performing an invasive blood test.

4. the sensor data includes data indicating, as the blood flow timing, timings at which the blood flow is detected for each heartbeat during each of the multiple compressions of the at least one location while the pressure is reduced at different speeds; The arterial blood pressure estimation device according to claim 1 , wherein the control unit performs control to synchronize the timing at which the pressure starts to be reduced with the respiratory cycle.

5. the sensor data includes data indicating, as the blood flow timing, timings at which the blood flow is detected for each heartbeat in each of the plurality of compressions, the timing at which the blood flow is detected for each heartbeat, by compressing the at least one location a plurality of times while starting to reduce the pressure at different speeds for each compression and reducing the pressure at a common speed from the heartbeat at which the blood flow is detected; The arterial blood pressure estimation device according to claim 1 , wherein the control unit performs control to synchronize the timing at which the pressure starts to be reduced with the respiratory cycle.

6. the sensor data includes data indicating a timing at which ejection is detected for each heartbeat as an ejection timing; The arterial blood pressure estimation device according to claim 1 , wherein the control unit estimates the change in the arterial pressure over time based on the time difference between the pumping timing and the blood flow timing indicated by the sensor data and the pressure value.

7. The arterial blood pressure estimation device according to claim 1 , wherein the control unit estimates LVEDP based on an estimation result of the change in arterial blood pressure over time.

8. The arterial pressure estimation device according to claim 7, wherein the control unit estimates an arterial pressure waveform as a change in the arterial pressure over time, estimates a left ventricular pressure waveform based on the estimated arterial pressure waveform, and obtains an estimated value of the LVEDP from the estimated left ventricular pressure waveform.

9. The arterial blood pressure estimation device according to claim 7 , wherein the control unit inputs the estimated result of the change in arterial blood pressure over time into a trained model and obtains the estimated value of the LVEDP from the trained model.

10. The arterial blood pressure estimation device according to any one of claims 7 to 9, wherein the control unit generates a trained model for obtaining an estimated value of the LVEDP by performing machine learning using at least a portion of the estimated results of the change in arterial blood pressure over time.

11. The arterial blood pressure estimation device according to claim 7 , wherein the control unit presents the estimated value of the LVEDP to a user.

12. The arterial blood pressure estimation device according to claim 1 , wherein the control unit estimates a parameter related to intracardiac hemodynamics based on the estimated result of the change in arterial blood pressure over time.

13. The arterial blood pressure estimation device according to claim 12 , wherein the parameter includes pulmonary artery pressure or pulmonary artery wedge pressure.

14. The arterial blood pressure estimation device according to any one of claims 1 to 13; a sensor for detecting the blood flow; An arterial pressure estimation system comprising:

15. The arterial blood pressure estimation system according to claim 14 , further comprising an expansion portion that compresses the at least one location.

16. the expansion portion compresses at least one portion of the blood vessel downstream of the aorta while gradually reducing the pressure; a sensor for detecting blood flow occurring at the at least one location for each heartbeat; a control unit that acquires sensor data indicating, as a blood flow timing, a timing at which the blood flow is detected for each heartbeat when the at least one location is compressed; The control unit records the pressure value corresponding to each blood flow timing, the control unit corrects the pressure value corresponding to the blood flow timing included in the inspiration period of the respiratory cycle; An arterial pressure estimation method in which the control unit estimates changes in arterial pressure over time by referring to acquired sensor data and the recorded and corrected pressure values.

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