Determining vascular compliance

Abstract

The disclosed concepts are directed to providing protocols, ideas, concepts, designs, methods and systems related to determining vascular compliance of a subject. In particular, blood pressure and arterial flow of first and second arteries (corresponding arteries on the same or contralateral limb) are measured (e.g., as a function of arterial diameter and / or velocity at which blood travels through the arteries). The pulse pressure can be determined from the blood pressure and the pulse quantity can be determined from the arterial flow. Vascular compliance can be determined from the pulse pressure and the volumetric pressure. Therefore, a direct and accurate vascular compliance estimation result can be obtained in a non-invasive manner. Also disclosed is using the determined vascular compliance in a transfer function to obtain accurate hemodynamic parameter estimates (e.g., cardiac output and stroke output) of a subject.

Description

Technical Field

[0001] This invention relates to the field of vascular compliance determination. Background Technology

[0002] Non-invasive estimations of a subject's stroke volume and cardiac output are typically achieved by applying a transfer function to physiological parameters that can be conveniently and non-invasively measured. Such non-invasive physiological parameters include blood pressure and demographic information (e.g., height, weight, age, and sex) that can be readily obtained from the subject.

[0003] Vascular compliance can be estimated using subject demographic information, indicating how measured pulse pressure relates to underlying pulse volume, which is the information needed to determine stroke volume and / or cardiac output. However, determining vascular compliance estimates based on demographics is often inaccurate because: (i) the subject's vascular age may differ from their chronological age; and (ii) vascular condition is not merely a constant function of demographics, but depends on underlying time-varying subject-specific hemodynamics.

[0004] Therefore, the inventors have recognized the need for an improved means of determining vascular compliance and thus improving the estimation of hemodynamic parameters. Summary of the Invention

[0005] This invention is defined by the claims.

[0006] According to one aspect of the invention, a system for determining the vascular compliance of an object is provided.

[0007] The system includes: A blood pressure sensor configured to measure blood pressure in the first artery of the object; An ultrasound sensor is configured to measure arterial flow in a second artery of the object, wherein the first artery and the second artery are the same artery or corresponding arteries of the contralateral limb; The controller is configured as follows: Control the blood pressure sensor to measure the blood pressure; Control the ultrasound sensor to measure the arterial flow; and The processor is configured as follows: Pulse pressure is determined based on the measured blood pressure; Pulse volume is determined based on the measured arterial flow rate; and The vascular compliance of the object is determined based on the pulse pressure and the pulse volume.

[0008] The examples in this disclosure are based on the understanding that by providing an ultrasound sensor and a blood pressure sensor, the vascular compliance of an object can be directly determined.

[0009] Arterial flow rate (i.e., the rate at which blood flows through an artery) can be determined using ultrasound sensors. This means measuring changes in arterial diameter and / or the velocity of blood flowing through an artery. Specifically, operating an ultrasound sensor in Doppler or color Doppler mode allows for the measurement of blood velocity, while operating it in M, B, or A mode allows for the measurement of diameter. Based on this arterial flow rate information, changes in volume or pulse rate within the artery due to cardiac pulse (i.e., heartbeat) can be determined in various ways.

[0010] Of course, blood pressure measurements from a blood pressure sensor (e.g., a pressure cuff) can be used to determine the pressure in the arteries caused by the heartbeat pulse (i.e., heartbeat) or pulse pressure. Typically, this is achieved by determining the difference between systolic and diastolic blood pressure.

[0011] Typically, pulse volume can be utilized according to the following formula. and pulse pressure To determine vascular compliance C: [1] It is important to note that the above content is not intended to be limiting. In fact, this disclosure provides various methods for using arterial flow and blood pressure measurements to determine pulse volume and pulse pressure, and the corresponding vascular compliance.

[0012] In any case, when the vascular compliance of an individual is known, hemodynamic parameters (e.g., cardiac output and stroke volume) can be accurately estimated. In contrast to the typical use of demographic information to help predict such hemodynamic parameters, this invention enables the direct determination of vascular compliance without considering the difference between the individual's actual age and vascular age, or hemodynamic changes over time; the vascular compliance will be accurate.

[0013] The controller can be configured to control a blood pressure sensor to measure blood pressure and an ultrasound sensor to measure arterial flow simultaneously or substantially sequentially. In practice, precisely simultaneous acquisition of blood pressure and arterial flow information is not required. In fact, such precise simultaneous acquisition may be undesirable when measuring blood pressure using a pressure cuff, as this could compress the artery size and alter the arterial flow measurement. However, to ensure accurate determination of vascular compliance, it may be desirable to perform the two measurements very close in time (i.e., substantially sequentially or one after the other).

[0014] The first artery can be the subject's first brachial artery. The second artery can be the first brachial artery or the artery in the second brachial artery of the limb opposite to the first brachial artery. The subject may find blood pressure and ultrasound measurements of the brachial arteries familiar and comfortable.

[0015] In some embodiments, the controller may be configured to control the blood pressure sensor to measure systolic and diastolic blood pressure. In this case, the processor may be configured to determine the pulse pressure based on the systolic and diastolic blood pressure. This provides the minimum requirements for determining the pulse pressure.

[0016] The ultrasound sensor can be configured to measure the velocity of blood traveling through the second artery and the diameter of the second artery. The controller can control the ultrasound sensor to measure the velocity and the diameter, and the processor can be configured to determine the pulse volume based on the velocity and the diameter.

[0017] The most accurate and reliable measurement of pulse volume (i.e., the change in arterial blood volume due to the heartbeat pulse) is based on the speed at which blood travels through the arteries during the heartbeat pulse and the diameter of the arteries during the heartbeat pulse.

[0018] In this configuration, the ultrasonic sensor can be configured to operate using pulse wave Doppler mode or color Doppler mode to measure the velocity, and can be configured to operate using M mode, B mode, or A mode to measure the diameter.

[0019] Alternatively, the ultrasound sensor can be configured to measure the diameter of the second artery. Therefore, the controller can control the ultrasound sensor to measure the diameter, and the processor can be configured to determine the pulse volume based on the diameter.

[0020] Even without velocity measurement, the diameter of an artery during a heartbeat can be used as an estimate of pulse volume. That is, the change in arterial diameter during a pulse will be correlated with the change in arterial blood volume as a result of the pulse, and this pulse volume can be derived without configuring an ultrasound sensor for velocity measurement.

[0021] As another alternative, the ultrasound sensor can be configured to measure the velocity of blood traveling through the second artery. The controller can control the ultrasound sensor to measure the velocity, and the processor can be configured to determine the pulse volume based on the velocity.

[0022] As described above, even without diameter measurement, the velocity of blood traveling through the artery during a heartbeat can be used as an estimate of pulse volume. In practice, in this case, pulse volume can be estimated using the average measured velocity of blood traveling through the artery, or the variation in the average measured velocity of blood traveling through the artery, along with an estimate of the artery diameter. Therefore, in this embodiment, pulse volume can be derived without requiring an ultrasound sensor to be configured for diameter measurement.

[0023] The controller can also be configured to control the blood pressure sensor to measure a blood pressure signal over at least one cardiac cycle. In this case, the processor can be configured to: determine a time constant for the exponential decay of the blood pressure based on the blood pressure decay after systole in the continuous blood pressure signal; determine peripheral vascular resistance based on the mean blood pressure over the at least one cardiac cycle and the mean of the measured arterial flow; and determine the vascular compliance of the subject based on the time constant and the peripheral vascular resistance.

[0024] Another approach to determining vascular compliance involves the time constant of the exponential decay of blood pressure between systole and diastole. In this case, blood pressure measurements are taken continuously throughout the cycle to determine the time constant, and peripheral vascular resistance is determined based on blood pressure and arterial flow measured by an ultrasound monitor. Therefore, vascular compliance can be determined using the obtained time constant and peripheral vascular resistance.

[0025] This is advantageous because it can be achieved through a single measurement of arterial flow, thus requiring less hardware and saving costs.

[0026] When the first artery and the second artery are the same artery, the blood pressure sensor can be configured to measure the blood pressure of the first artery of the subject at a first location, and the ultrasound sensor can be configured to measure the arterial flow of the second artery at two longitudinally separated locations. The first location is situated between the two longitudinally separated locations. In this case, the processor can be configured to further determine the vascular compliance of the subject based on the arterial flow measured at the two longitudinally separated locations.

[0027] To more accurately determine vascular compliance, arterial flow can be measured at two locations using an ultrasound sensor, with a blood pressure sensor measuring blood pressure between them.

[0028] In some embodiments, the controller may be configured to: control the blood pressure sensor to measure the blood pressure during a first time period; control the ultrasound sensor to measure the arterial flow during the first time period; control the blood pressure sensor to measure the blood pressure during a second time period; and control the ultrasound sensor to measure the arterial flow during the second time period, wherein the second time period and the first time period are sequential. In this case, the processor may be configured to: determine the pulse pressure based on the difference between the blood pressure measured during the first time period and the blood pressure measured during the second time period; and determine the pulse volume based on the difference between the arterial flow measured during the first time period and the arterial flow measured during the second time period.

[0029] It is also possible to use the difference between blood pressure and arterial flow at two subsequent periods / times to determine pressure pulse and volume pulse, and further improve the accuracy of the determined vascular compliance.

[0030] The controller can be configured to control the blood pressure sensor to measure the blood pressure over multiple cardiac cycles. The processor can be configured to determine the pulse pressure based on the average of the blood pressure measured over the multiple cardiac cycles.

[0031] The average of blood pressure over multiple cardiac cycles (e.g., the phase rectified signal average (PRSA)) can reduce noise in the measured blood pressure and improve the accuracy of pulse pressure determination.

[0032] Similarly, the controller can be configured to control the ultrasound sensor to measure the arterial flow over multiple heartbeats. The processor can be configured to determine the pulse volume based on the average of the arterial flow over the multiple heartbeats.

[0033] Regarding blood pressure, averaging over multiple cardiac cycles / heartbeats can smooth out the noise present in an individual's cardiac cycle / heartbeat. Therefore, averaging (e.g., PRSA) can reduce noise in the measured arterial flow and improve the accuracy of pulse determination.

[0034] The controller can be configured to continuously control the ultrasound sensor to measure the arterial flow. In this case, the processor can be configured to detect whether the change in the measured arterial flow over time meets predetermined conditions. Then, the controller can be configured to control the blood pressure sensor to measure the blood pressure in response to detecting the change in the arterial flow.

[0035] In other words, changes in arterial flow can trigger the system to determine vascular compliance. For patients, ultrasound measurements using ultrasound sensors are typically non-invasive and comfortable. In contrast, blood pressure measurements can be interfered with by manipulations such as pressure cuffs. Therefore, operating systems that only detect changes in arterial flow using ultrasound sensors can improve subject comfort during long-term monitoring without missing any changes in vascular compliance (reflecting changes in hemodynamic parameters).

[0036] According to another embodiment of the present invention, a method for determining the vascular compliance of an object is provided, comprising: Control the blood pressure sensor to measure the blood pressure in the first artery of the object; Control an ultrasound sensor to measure the arterial flow of the object's second artery, wherein the first artery and the second artery are the same artery or corresponding arteries of the contralateral limb; Pulse pressure is determined based on the measured blood pressure; Pulse volume is determined based on the measured arterial flow rate; and The vascular compliance of the object is determined based on the pulse pressure and the pulse volume.

[0037] According to another example of one aspect of the present invention, a method for determining hemodynamic parameters of an object is provided, comprising: Obtain the blood pressure measurement results of the subject; Determining the vascular compliance of the object according to any of the embodiments described herein; and The transfer function is used to process the vascular compliance of the object and the blood pressure measurement results to determine the hemodynamic parameters.

[0038] In some embodiments, the method for determining hemodynamic parameters may further include obtaining arterial flow measurements of the object. In this case, the processing steps may include using a transfer function to process vascular compliance, the object's blood pressure measurements, and the object's arterial flow measurements to determine the hemodynamic parameters.

[0039] According to another example of a further aspect of the invention, a computer program including computer program code units is provided, which, when run on a computer, are adapted to implement methods for determining the vascular compliance of an object and / or determining the hemodynamic parameters of the object.

[0040] These and other aspects of the invention will become apparent and elucidated from the embodiments described below. Attached Figure Description

[0041] To better understand the invention and to more clearly illustrate how the invention can be implemented, reference will now be made to the accompanying drawings by way of example only, in which: Figure 1 The graph presents the blood pressure waveform acquired over a 30-second time period and the average value of the phase rectified signal representing the blood pressure waveform. Figure 2 The graph presents the arterial velocity waveform acquired over a 30-second time period and the average value of the phase rectified signal representing the velocity waveform. Figure 3 It is a vascular model used to determine vascular compliance; Figure 4 A block diagram of a system for determining the vascular compliance of an object according to one aspect of the present invention is presented; Figure 5 A flowchart of a method for determining the vascular compliance of an object according to another aspect of the present invention is presented; Figure 6 A flowchart of a method for determining hemodynamic parameters of an object according to another aspect of the present invention is presented; and Figure 7 This is a simplified block diagram of a computer in which one or more parts of an embodiment may be employed. Detailed Implementation

[0042] The invention will be described with reference to the accompanying drawings.

[0043] It should be understood that while the detailed description and specific examples indicate exemplary embodiments of the apparatus, system, and method, they are intended for illustrative purposes only and are not intended to limit the scope of the invention. These and other features, aspects, and advantages of the apparatus, system, and method of the invention will be better understood from the following description, the appended claims, and the accompanying drawings. The mere fact that certain measures are recited in dissimilar dependent claims does not indicate that combinations of these measures cannot be advantageously used.

[0044] It should be understood that the accompanying drawings are merely schematic and not drawn to scale. It should also be understood that the same reference numerals are used in all the accompanying drawings to indicate the same or similar parts.

[0045] The proposed concepts aim to provide schemes, ideas, ideas, designs, methods, and systems related to determining the vascular compliance of a subject. Specifically, blood pressure and arterial flow are measured in a first and second artery (either the same artery or a corresponding artery on the contralateral limb) based on arterial diameter and / or the velocity of blood traveling through the artery. Pulse pressure can be determined from blood pressure, and pulse volume can be determined from arterial flow. Vascular compliance can be determined from pulse pressure and pulse volume. Therefore, direct and accurate estimates of vascular compliance can be obtained non-invasively. It is also proposed to use the determined vascular compliance in a transfer function to obtain accurate estimates of the subject's hemodynamic parameters (e.g., cardiac output and stroke volume).

[0046] In other words, this disclosure proposes using ultrasound and blood pressure measurements to directly assess a subject's vascular compliance. Vascular compliance indicates how the measured pulse pressure relates to the underlying pulse volume. Therefore, it has been recognized that a subject's vascular compliance can be assessed by measuring the pulse volume (ΔV) and pulse pressure (ΔP) in the same or contralateral artery using ultrasound and blood pressure sensors, respectively. Improved vascular compliance estimation can be achieved using the obtained measurements. The improved vascular compliance determination / estimation results can then be used in the transfer function to improve the estimation of the subject's stroke volume and cardiac output, and / or the improved vascular compliance determination / estimation results can be fed into a pulse profiling algorithm.

[0047] In this context, hemodynamic monitoring (e.g., monitoring cardiac output and stroke volume) is essential for the early detection, identification, and management of life-threatening clinical conditions such as sepsis and cardiogenic shock. Additionally, this monitoring can be used to assess the effectiveness of therapeutic / pharmacological interventions (e.g., administration of vasopressors).

[0048] The gold standard for measuring cardiac output is the thermodilution method (e.g., used in the Swan-Ganz pulmonary artery catheter). This is an invasive and intermittent method that can be used multiple times a day, but not continuously.

[0049] One method for providing continuity in hemodynamic measurements is based on pulse profile analysis. This method utilizes blood pressure measurement, typically taken from an artery using an invasive catheter. Transfer functions based on the BP waveform and the subject's demographic information (e.g., height, weight, age, and sex) are used to continuously estimate hemodynamic parameters.

[0050] Currently, the transfer function used in pulse contour analysis includes demographic information as a surrogate measure for estimating vascular compliance. This is because there is no non-invasive device available for directly measuring vascular compliance, making the measurement of vascular compliance a complex task.

[0051] However, compliance estimates based on demographic models are inaccurate because: (i) Due to lifestyle choices, chronic diseases, and genetic variations, a subject's vascular age may differ from their chronological age; and (ii) The vascular condition of the subject is not only a constant function of demographics, but also depends on patient-specific hemodynamics that change over time (e.g., medications, concentration of cardiac output, etc.).

[0052] Furthermore, the accuracy of calibrated pulse profilometry algorithms is known to decrease over time. Therefore, directly measuring vascular compliance can improve the accuracy of both calibrated and uncalibrated pulse profilometry algorithms.

[0053] Therefore, the implementation provides the use of ultrasound and blood pressure measurements to directly determine vascular compliance, and incorporates the determined vascular compliance into a transfer function used in pulse profile analysis.

[0054] Specifically, this can be achieved by using ultrasound equipment / sensors and blood pressure equipment / sensors (e.g., cuffs or arterial lines) to measure pulse volume (ΔV) and pulse pressure (ΔP) on the same or opposite artery.

[0055] Vascular compliance C can be calculated using the following formula: Here, ΔV is the change in arterial blood volume caused by heartbeat and pulse, and ΔP is the corresponding change in arterial blood pressure caused by heartbeat and pulse (e.g., the difference between systolic and diastolic blood pressure, also known as pulse pressure).

[0056] Therefore, the minimum requirement for implementing this invention is: (i) A blood pressure sensor (e.g., a pressure cuff, arterial line, or any other device that generates a blood pressure estimate) capable of determining pulse pressure using measurements from the blood pressure sensor; and (ii) An ultrasound sensor capable of measuring arterial flow. For example, an ultrasound sensor capable of measuring arterial lumen diameter and / or arterial velocity can then be used to estimate arterial flow. The pulse volume can then be determined using the measurements from the ultrasound sensor.

[0057] Preferably, blood pressure and arterial flow measurements can be performed using blood pressure sensors and ultrasound sensors that are physically very close (e.g., separated by a short distance on an arterial branch, such as the brachial artery). This ensures an accurate estimate of local compliance. Nevertheless, blood pressure and arterial flow can also be measured at different locations (e.g., in the contralateral limb of the subject).

[0058] Pulse volume and pulse pressure can be determined in many ways based on blood pressure sensor and ultrasound sensor measurements (from which vascular compliance can be derived). Some of these methods are outlined below.

[0059] Figure 1 The graph shows the arterial blood pressure waveform acquired over a 30-second period (top graph) and the average phase rectified signal (PRSA) representing the arterial blood pressure waveform used to create the overall average blood pressure waveform (bottom graph).

[0060] Pulse pressure can be measured on a single heartbeat by simply subtracting the diastolic pressure from the systolic pressure measured by the blood pressure sensor. However, this method can be noisy (e.g., due to breathing or movement). To capture a representative measure of pulse pressure and thus vascular compliance, it is possible to average the blood pressure waveforms over multiple heartbeats to create a PRSA over multiple heartbeats (e.g., using the peak value as an anchor). Figure 1 This situation is illustrated in the figure. The pulse pressure of this overall average can be used as a more robust measure of ΔP.

[0061] Figure 2 The diagram presents the arterial velocity waveform acquired over a 30-second period (top graph) and a PRSA diagram representing the velocity waveform used to create a representative velocity pulsation (bottom graph).

[0062] As shown in the figure, the overall average value of the velocity waveform (corresponding to the heartbeat) can be extracted. This velocity waveform can then be multiplied by the average arterial cross-section over that period (i.e., ) to obtain ( The estimated results of arterial flow are expressed in units of 1 / 2.

[0063] For example, diameter can be extracted using an ultrasonic sensor operating in M-mode, B-mode, or A-mode. Velocity can be extracted using an ultrasonic sensor operating in pulse wave Doppler or color Doppler.

[0064] Therefore, overall mean pulse pressure and pulse velocity can be measured and used to obtain estimates of the vascular compliance of an artery (e.g., the brachial artery) of a subject. The following steps can be taken: (i) The vascular compliance of an artery can be determined as C = ΔV / ΔP, where ΔV (e.g., as...) ΔP (in mmHg) is the change in arterial blood volume caused by heartbeats and pulses, and ΔP (in mmHg) is the corresponding change in arterial blood pressure caused by heartbeats and pulses. (ii) It is possible, for example, to calculate ΔP as Figure 1The overall average pulse pressure is measured by the difference between the systolic and diastolic blood pressure levels to determine the average pulse pressure (ΔP) over a period of time. (iii) The arterial flow volume can be calculated by multiplying the velocity by the average arterial cross-section, and the volume can be obtained by integrating the flow over time. The integration of arterial flow provides an estimate of the amount of blood flowing through the artery in the longitudinal direction. To obtain the change in arterial blood volume (i.e., pulse volume), the integration of flow over the entire pulse duration can be used, or the integration of flow from diastole to systole can be used; (iv) Even if the pulse volume determined in this way moves longitudinally within the artery, the pulse volume does indeed reflect vascular compliance caused by changes in the arterial lumen. In fact, even if the shape of the pressure wave is affected by vascular compliance, Equation 1 can be used to estimate arterial compliance; (v) Alternatively, ΔP and ΔV can be measured by measuring the relative changes over two subsequent periods, each period being, for example, 30 seconds in length, wherein ΔP can be determined as the difference between pressures (e.g., mean pressure, systolic pressure, or diastolic pressure) obtained for an individual period, and ΔV can be determined as the difference between longitudinal volumes obtained for an individual period.

[0065] As an alternative to using blood pressure and ultrasound measurements to determine vascular compliance, it is necessary to understand the radial dilation of arteries caused by cardiac pressure pulses. The simplest estimate of vascular compliance can be based on the pressure pulse ΔP and the resulting change in arterial diameter (ΔD), i.e., ,in, It is the diameter of the artery during systole, and This is the diameter of the brachial artery during diastole. In this case, the estimation result of vascular compliance can be obtained as... [mm / mmHg].

[0066] Preferably, changes in arterial diameter are not measured during cuff inflation of the blood pressure sensor, as this would alter the shape of the artery. In this embodiment, volumetric changes in arterial flow are not measured, so the ultrasound sensor can operate only in M, B, or A modes to provide a measure of arterial diameter change (i.e., as a proxy for arterial flow).

[0067] Alternatively, Figure 3 A vascular model is presented that can be used to determine vascular compliance C based on arterial pressure / blood pressure measurements and one or two arterial flow measurements. Specifically, This indicates the arterial flow rate into the artery (i.e., upstream of the blood pressure sensor). This represents the arterial flow rate out of the artery (i.e., downstream of the blood pressure sensor), and It is a measurement of blood pressure. and These represent the vascular resistance proximal to the blood pressure measurement and the vascular resistance distal to the blood pressure measurement, respectively.

[0068] essentially, Figure 3 This indicates that vascular compliance can also be assessed based on the exponential decay of blood pressure after systole. During this phase of the pressure pulse, from the moment of systole... Starting from the systolic blood pressure at that point, an exponential decay can be fitted using the following formula: in, It is the moment of contraction. systolic blood pressure, It is the moment of relaxation. diastolic blood pressure, It is an exponentially decaying time constant. It is peripheral vascular resistance, and It refers to vascular compliance. The exponential fit provides the time constant. The estimation results, time constant It is the product of peripheral vascular resistance and vascular compliance. Peripheral vascular resistance can be estimated based on arterial pressure and arterial flow. Figure 2 Arterial flow rate is obtained by multiplying the (average) arterial velocity by the average cross-sectional area of ​​the artery. The estimate of peripheral vascular resistance can be obtained as the ratio of the mean overall average pressure pulse to the mean overall average flow pulse. This can be expressed as: in, The mean pulse duration is given by MAP, mean arterial pressure by MAP, and mean arterial flow by MAF. The estimation of brachial artery compliance can then be obtained as follows: More advanced vascular compliance measurements can be based on two arterial flow measurements ( and ),like Figure 3 As shown. Typically, arterial flow rate can be obtained by multiplying the velocity by the average cross-section of the artery. In this case, the relationship between arterial pressure / blood pressure and arterial flow rate through the brachial artery can be expressed as follows: or By starting from the relaxation time At the moment of contraction By integrating the integral, we can obtain the estimate of compliance as: In this case, ΔV is the expansion of arterial volume caused by cardiac pulse pressure ΔP.

[0069] It is worth noting that blood pressure and arterial flow can be measured asynchronously in time, as long as they are measured very close in time. In this case, it is advantageous to measure arterial flow and blood pressure over multiple heartbeats. In fact, when the cuff, which is usually associated with the blood pressure sensor, is inflated and thus affects the lumen size (e.g., diameter, shape), it may be preferable not to image the arteries (i.e., determine arterial flow via an ultrasound sensor).

[0070] Figure 4 A block diagram of a system 100 for determining the vascular compliance of an object according to one aspect of the invention is presented. That is, system 100 is adapted to estimate how the pulse pressure of an object relates to the underlying pulse volume in response to a heartbeat. Specifically, a blood pressure sensor 110, an ultrasound sensor 120, a controller 130, and a processor 140 are provided. Each component may be provided in a single microcontroller or may be several physical devices with different communication links.

[0071] Blood pressure sensor 110 is configured to measure blood pressure in a subject's first artery. Blood pressure can be measured continuously by the blood pressure sensor over one heartbeat pulse (i.e., a cardiac cycle or heartbeat), or the systolic and diastolic blood pressure of the artery can be measured simply over one heartbeat pulse. In other embodiments, the blood pressure sensor can perform the above measurements over multiple heartbeat pulses and then generate an average value, such as the phase rectified signal average (PRSA), or the arithmetic mean of the measured systolic and diastolic blood pressures, or the arithmetic mean of the measured pulse pressures.

[0072] An ultrasound sensor 120 is configured to measure arterial flow in a second artery of the subject. That is, the ultrasound sensor is configured to measure the diameter of the second artery and / or the velocity of blood traveling through it. Each measurement, or both, can be used as a representative of the arterial flow in the second artery. Similar to the above, the ultrasound sensor can continuously measure arterial flow (e.g., diameter and / or velocity) over one heartbeat of the subject, or it can simply sample the arterial flow at one or more portions of the heartbeat. Alternatively, the ultrasound sensor can perform the above measurements over multiple heartbeats and then generate an average (e.g., PRSA).

[0073] In some cases, ultrasonic sensors can be configured to operate using pulse wave Doppler mode or color Doppler mode to measure velocity, and can be configured to operate using M mode, B mode, or A mode to measure diameter.

[0074] The first and second arteries are either the same artery or corresponding arteries on the opposite side of the limb. That is, the first and second arteries from which the ultrasound sensor and the blood pressure sensor measure can be a single artery or an arterial branch (e.g., the brachial artery), or they can be arteries on the opposite side of the limb (e.g., the ultrasound sensor is on one brachial artery and the blood pressure sensor is on the opposite brachial artery).

[0075] Blood pressure sensors and ultrasound sensors can be implemented in the same device. For example, an ultrasound sensor can be integrated into an existing blood pressure sensor (e.g., a pressure cuff) for seamless measurement of parameters needed to determine vascular compliance.

[0076] The controller is configured to control a blood pressure sensor to measure blood pressure. The controller is also configured to control an ultrasound sensor to measure arterial flow. In other words, the controller generates control signals to cause the blood pressure sensor and ultrasound sensor to perform their respective measurements.

[0077] Furthermore, the controller can be configured to simultaneously or substantially sequentially control the blood pressure sensor to measure blood pressure and control the ultrasound sensor to measure arterial flow. The controller can induce simultaneous or sequential measurements based on the object's environment / background and can provide different types of measurements in alternating modes.

[0078] In some cases, the controller can be configured to continuously control an ultrasound sensor to measure arterial flow. In this scenario, the processor can be configured to detect whether a change in the measured arterial flow over time meets predetermined conditions. The controller can then be configured to control a blood pressure sensor to measure blood pressure in response to the detected change in arterial flow. This can provide a system that automatically detects changes in vascular compliance (and therefore, possibly hemodynamic parameters) without causing discomfort or trauma.

[0079] The processor is configured to determine pulse pressure based on the measured blood pressure. Specifically, pulse pressure can be determined by acquiring the difference between systolic and diastolic blood pressure.

[0080] Furthermore, the processor is configured to determine pulse volume based on the measured arterial flow. Pulse volume can be determined based on arterial flow using any of the methods described above.

[0081] Specifically, pulse volume can be based on measured velocity and / or diameter. When both velocity and diameter are measured, the velocity can be multiplied by the diameter to determine arterial flow. When only one of velocity or diameter is measured by an ultrasound sensor, predicted or historical values ​​of velocity and / or diameter can be used with the actual measurements to determine arterial flow. Arterial flow can be integrated over time (providing an estimate of the amount of blood traveling through the artery in the longitudinal direction), and the change in arterial volume between systole and diastole, based on the integration, can be determined as, for example, pulse volume.

[0082] The processor is then configured to determine the object's vascular compliance based on pulse pressure and pulse volume. This can be achieved by simply dividing the pulse pressure by the pulse volume. However, various post-processing methods can be performed on the determined pulse pressure and pulse volume to obtain accurate vascular compliance determination results.

[0083] In some example implementations, the processor may (additionally or alternatively) be configured to determine the time constant of exponential decay of blood pressure based on the decay of blood pressure after systole in a continuous blood pressure signal. The processor can then determine peripheral vascular resistance based on the mean blood pressure over at least one cardiac cycle and the mean of the measured arterial flow (e.g., the mean arterial flow determined over at least one cardiac cycle). Vascular compliance of the subject can then be determined based on the time constant and peripheral vascular resistance.

[0084] Of course, System 100 may employ any publicly available methods and means for determining vascular compliance.

[0085] Figure 5 A flowchart of a method 200 for determining the vascular compliance of an object according to another aspect of the present invention is presented.

[0086] In step 210, the blood pressure sensor is controlled to measure the blood pressure of the subject's first artery.

[0087] In step 220, an ultrasound sensor is controlled to measure the arterial flow in the subject's second artery. The first and second arteries are either the same artery or corresponding arteries from the contralateral limb.

[0088] In step 230, pulse pressure is determined based on the measured blood pressure.

[0089] In step 240, pulse volume is determined based on the measured arterial flow.

[0090] In step 250, the vascular compliance of the subject is determined based on pulse pressure and pulse volume.

[0091] Figure 6A flowchart of a method 300 for determining hemodynamic parameters of a subject according to another aspect of the present invention is presented. For example, the method can be used to determine the cardiac output and / or stroke volume of a subject.

[0092] In step 310, the subject's blood pressure measurement result is obtained. The blood pressure measurement result can be obtained from a blood pressure sensor (possibly the same blood pressure sensor used in method 200 above). Alternatively, the blood pressure measurement result can be a previously acquired historical measurement result.

[0093] In (optional) step 312, an arterial flow measurement of the subject is obtained (supplementing the blood pressure measurement). The arterial flow measurement can be obtained from an ultrasound sensor (possibly the same ultrasound sensor used in method 200 above). Alternatively, the arterial flow measurement can be a previously acquired historical measurement.

[0094] In step 200, the vascular compliance value of the object is determined according to method 200. This step can be performed before or after obtaining the blood pressure measurement result in step 310, and may include obtaining the vascular compliance value from a database (e.g., the object's EMR) determined using method 200.

[0095] In step 320, a transfer function is used to process / analyze the object's vascular compliance and blood pressure measurements to determine hemodynamic parameters. This can be implemented using any known transfer function familiar to a technician that uses vascular compliance and blood pressure measurements to determine hemodynamic parameters. In fact, existing transfer functions that use demographic information as a proxy for vascular compliance can be adapted to receive vascular compliance and output hemodynamic parameters.

[0096] Alternatively, (if arterial flow measurement results have also been obtained) in step 320, a transfer function is used to process / analyze the object's vascular compliance, arterial flow measurement results, and blood pressure measurement results to determine hemodynamic parameters. This can be implemented using any known transfer function familiar to those skilled in the art that uses vascular compliance, arterial flow measurement results, and blood pressure measurement results to determine hemodynamic parameters. In fact, existing transfer functions that use demographic information as a proxy for vascular compliance can be adapted to receive vascular compliance and output hemodynamic parameters.

[0097] Figure 7An example of a computer 1000 in which one or more portions of an embodiment may be employed is illustrated. The various operations discussed above can utilize the capabilities of computer 1000. For example, one or more portions of a system for acquiring input from a user to control an interface can be incorporated into any element, module, application, and / or component discussed herein. In this regard, it should be understood that system functional blocks can operate on a single computer or can be distributed across several computers and locations (e.g., connected via the Internet).

[0098] Computer 1000 includes, but is not limited to, smartphones, PCs, workstations, laptops, PDAs, handheld devices, servers, storage devices, patient monitors, etc. In many cases, the disclosed systems and methods can be implemented in patient monitors (e.g., bedside monitors). Such monitors can be used in, for example, intensive care units (ICUs), operating rooms (ORs), or post-anesthesia care units (PACUs).

[0099] Typically, in terms of hardware architecture, computer 1000 may include one or more processors 1010, memory 1020, and one or more I / O devices 1030 communicatively coupled via a local interface (not shown). The local interface can be, for example, but not limited to, one or more buses or other wired or wireless connections as known in the art. The local interface may have additional elements (e.g., controllers, buffers (cache memory), drivers, repeaters, and receivers) to enable communication. Additionally, the local interface may include address, control, and / or data connections to enable appropriate communication between the aforementioned components.

[0100] Processor 1010 is a hardware device for executing software that can be stored in memory 1020. Processor 1010 can actually be any custom or commercially available processor, central processing unit (CPU), digital signal processor (DSP), or auxiliary processor, etc., associated with computer 1000, and processor 1010 can be a semiconductor-based microprocessor (in the form of a microchip) or microprocessor.

[0101] The memory 1020 can include any one or a combination of volatile memory elements (e.g., random access memory (RAM), such as dynamic random access memory (DRAM), static random access memory (SRAM), etc.) and non-volatile memory elements (e.g., ROM, erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), programmable read-only memory (PROM), solid-state drive (SSD), magnetic tape, compact disc read-only memory (CD-ROM), magnetic disk, floppy disk, cassette tape, etc.). Furthermore, the memory 1020 can contain electronic, magnetic, optical, and / or other types of storage media. Note that the memory 1020 can have a distributed architecture, where various components are geographically separated but accessible by the processor 1010.

[0102] The software in memory 1020 may include one or more individual programs, each of which includes an ordered list of executable instructions for implementing logical functions. According to an exemplary embodiment, the software in memory 1020 includes a suitable operating system (O / S) 1050, a compiler 1060, source code 1070, and one or more application programs 1080. As shown, application program 1080 includes numerous functional components for implementing features and operations of the exemplary embodiment. Application program 1080 of computer 1000 may represent various applications, computing units, logical units, functional units, processes, operations, virtual entities, and / or modules according to the exemplary embodiment, but application program 1080 is not intended to be limiting.

[0103] Operating system 1050 controls the execution of other computer programs and provides scheduling, input / output control, file and data management, memory management, communication control, and related services. The inventors anticipate that application program 1080 for implementing exemplary embodiments can be applied to all commercially available operating systems.

[0104] Application 1080 can be a source program, an executable program (object code), a script, or any other entity including a set of instructions to be executed. When it is a source program, it is typically translated by a compiler (e.g., compiler 1060), assembler, interpreter, etc. (which may or may not be included in memory 1020) to operate appropriately in conjunction with O / S 1050. Furthermore, application 1080 can be written in an object-oriented programming language with data classes and method classes, or a procedural programming language with routines, subroutines, and / or functions (e.g., but not limited to C, C++, C#, Pascal, Python, BASIC, API calls, HTML, XHTML, XML, ASP scripts, JavaScript, FORTRAN, COBOL, Perl, Java, ADA, .NET, functional programming, etc.).

[0105] I / O device 1030 may include input devices, such as, but not limited to, a mouse, keyboard, scanner, microphone, camera, touchscreen, etc. Furthermore, I / O device 1030 may also include output devices, such as, but not limited to, a printer, monitor, etc. Finally, I / O device 1030 may also include devices for transmitting both input and output, such as, but not limited to, a NIC or modulator / demodulator (for accessing remote devices, other files, devices, systems, or networks), radio frequency (RF) or other transceivers, telephone interfaces, bridges, routers, etc. I / O device 1030 also includes components for communication over various networks (e.g., the Internet or intranet).

[0106] If the computer 1000 is a PC, workstation, intelligent device, etc., the software in the memory 1020 may also include a Basic Input / Output System (BIOS) (omitted for simplicity). The BIOS is a set of basic software routines that initialize and test the hardware at startup, boot the O / S 1050, and support data transfer between hardware devices. The BIOS is stored in some type of read-only memory (e.g., ROM, PROM, EPROM, EEPROM, etc.) so that it can be executed when the computer 1000 is activated.

[0107] When the computer 1000 is operating, the processor 1010 is configured to execute software stored in the memory 1020, transfer data to and from the memory 1020, and typically control the operation of the computer 1000 according to the software. The application program 1080 and O / S 1050 are read, in whole or in part, by the processor 1010, possibly cached within the processor 1010, and then executed.

[0108] When application 1080 is implemented as software, it should be noted that application 1080 can be stored on virtually any computer-readable medium for use or in conjunction with any computer-related system or method. In the context of this document, a computer-readable medium can be an electronic, magnetic, optical, or other physical device or apparatus capable of containing or storing computer programs used by or in conjunction with a computer-related system or method.

[0109] Application 1080 can be embodied in any computer-readable medium for use or in connection with an instruction execution system, apparatus, or device (e.g., a computer-based system, a processor-containing system, or other system capable of fetching and executing instructions from and with an instruction execution system, apparatus, or device). In the context of this document, "computer-readable medium" can be any device capable of storing, transmitting, propagating, or transmitting a program for use or in connection with an instruction execution system, apparatus, or device. Computer-readable media can be, for example, but not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatus, devices, or propagation media.

[0110] about Figure 5 and Figure 6 The methods described and about Figure 4 The described system can be implemented in hardware, software, or a combination of both (e.g., as firmware running on a hardware device). With respect to embodiments implemented partially or entirely in software, the functional steps shown in the process flow diagram can be performed by appropriately programmed physical computing devices (e.g., one or more central processing units (CPUs) or graphics processing units (GPUs)). Each process and its individual component steps as shown in the flow diagram can be performed by the same or different computing devices. According to an embodiment, a computer-readable storage medium stores a computer program including computer program code configured to cause one or more physical computing devices to perform the encoding or decoding methods described above when the program is run on one or more physical computing devices.

[0111] Storage media can include volatile and non-volatile computer memories, such as RAM, PROM, EPROM, EEPROM, SSD, optical discs (such as CD, DVD, BD), and magnetic storage media (such as hard disks and magnetic tapes). Various storage media can be fixed within a computing device or can be portable, allowing one or more programs stored thereon to be loaded into the processor.

[0112] Regarding the implementation of the embodiments in part or in whole in hardware, Figure 4The blocks shown in the block diagram can be individual physical components or logical subdivisions of a single physical component, or they can all be implemented in an integrated manner within a single physical component. The functionality of a block shown in the figures can be divided among multiple components in an implementation, or the functionality of multiple blocks shown in the figures can be combined in a single component in an implementation. Hardware components suitable for embodiments of the invention include, but are not limited to, conventional microprocessors, application-specific integrated circuits (ASICs), and field-programmable gate arrays (FPGAs). One or more blocks can be implemented as a combination of dedicated hardware for performing some functions and one or more programmable microprocessors and associated circuitry for performing other functions.

[0113] By studying the accompanying drawings, disclosure, and appended claims, those skilled in the art can understand and implement variations of the disclosed embodiments in practicing the claimed invention. In the claims, the word "comprising" does not exclude other elements or steps, and the words "a" or "an" do not exclude multiple. A single processor or other unit can perform the functions of several items recited in the claims. The mere fact that certain measures are recited in dissimilar dependent claims does not indicate that combinations of these measures cannot be advantageously used. If a computer program has been discussed above, it can be stored / distributed on a suitable medium (e.g., an optical or solid-state storage medium provided together with or as part of other hardware), but it can also be distributed in other forms (e.g., via the Internet or other wired or wireless telecommunications systems). If the term "suitable" is used in the claims or description, it should be noted that the term "suitable" is intended to be equivalent to the term "configured as." No reference numerals in the claims should be construed as limiting the scope.

[0114] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present invention. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of instructions, including one or more executable instructions for implementing one or more specified logical functions. In some alternative embodiments, the functions marked in the blocks may occur in a non-linear order as indicated in the drawings. For example, depending on the functions involved, two blocks shown successively may actually be executed substantially simultaneously, or these blocks may sometimes be executed in reverse order. It should also be noted that each block illustrated in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, can be implemented by a dedicated hardware-based system that performs the specified function or action or executes a combination of dedicated hardware and computer instructions.

Claims

1. A system (100) for determining the vascular compliance of an object, comprising: A blood pressure sensor (110) is configured to measure the blood pressure of the object's first artery; An ultrasound sensor (120) is configured to measure arterial flow in a second artery of the object, wherein the first artery and the second artery are the same artery or corresponding arteries of the contralateral limb; The controller (130) is configured as follows: Control the blood pressure sensor to measure the blood pressure; Control the ultrasound sensor to measure the arterial flow; as well as Processor (140), which is configured as follows: Pulse pressure is determined based on the measured blood pressure; Pulse volume is determined based on the measured arterial flow rate; and The vascular compliance of the object is determined based on the pulse pressure and the pulse volume.

2. The system according to claim 1, wherein, The controller (130) is configured to control the blood pressure sensor (110) to measure systolic and diastolic blood pressure, and wherein the processor (140) is configured to determine the pulse pressure based on the systolic and diastolic blood pressure.

3. The system according to claim 1 or 2, wherein, The ultrasound sensor (120) is configured to measure the speed at which blood travels through the second artery and the diameter of the second artery, and wherein the controller (130) controls the ultrasound sensor to measure the speed and the diameter, and wherein the processor (140) is configured to determine the pulse volume based on the speed and the diameter.

4. The system according to claim 3, wherein, The ultrasonic sensor (120) is configured to operate using a pulse wave Doppler mode or a color Doppler mode to measure the velocity, and is configured to operate using an M mode, a B mode, or an A mode to measure the diameter.

5. The system according to claim 1 or 2, wherein, The ultrasound sensor (120) is configured to measure the diameter of the second artery, and wherein the controller (130) controls the ultrasound sensor to measure the diameter, and wherein the processor (140) is configured to determine the pulse volume based on the diameter.

6. The system according to claim 1 or 2, wherein, The ultrasound sensor (120) is configured to measure the speed at which blood travels through the second artery, and wherein the controller (130) controls the ultrasound sensor to measure the speed, and wherein the processor (140) is configured to determine the pulse volume based on the speed.

7. The system according to any one of claims 1-6, wherein, The controller (130) is also configured to control the blood pressure sensor to measure continuous blood pressure signals over at least one cardiac cycle; and The processor (140) is further configured to: The time constant of the exponential decay of blood pressure is determined based on the blood pressure decay after systole in the continuous blood pressure signal. Peripheral vascular resistance is determined based on the mean blood pressure and the mean measured arterial flow during the at least one kinetic cycle; and The vascular compliance of the object is determined based on the time constant and the peripheral vascular resistance.

8. The system according to any one of claims 1-7, wherein, The first artery and the second artery are the same artery, and the blood pressure sensor (110) is configured to measure the blood pressure of the object's first artery at a first location. The ultrasound sensor (120) is configured to measure the arterial flow of the second artery at two longitudinally separated locations, the first location being located between the two longitudinally separated locations, and The processor (140) is configured to further determine the vascular compliance of the object based on arterial flow measured at the two longitudinally separated locations.

9. The system according to any one of claims 1-8, wherein, The controller (130) is configured to: Control the blood pressure sensor (110) to measure the blood pressure during a first time period; The ultrasound sensor (120) is controlled to measure the arterial flow during the first time period; Control the blood pressure sensor to measure the blood pressure during a second time period; as well as The ultrasound sensor is controlled to measure the arterial flow during the second time period, wherein the second time period and the first time period are sequential, and The processor (140) is configured as follows: The pulse pressure is determined based on the difference between the blood pressure measured during the first time period and the blood pressure measured during the second time period; and Pulse volume is determined based on the difference between the arterial flow measured during the first time period and the arterial flow measured during the second time period.

10. The system according to any one of claims 1-9, wherein, The controller (130) is configured to control the blood pressure sensor to measure the blood pressure over a plurality of cardiac cycles, and wherein the processor (140) is configured to determine the pulse pressure based on the average of the blood pressure measured over the plurality of cardiac cycles.

11. The system according to any one of claims 1-10, wherein, The controller (130) is configured to control the ultrasound sensor (120) to measure the arterial flow over multiple heartbeats, and wherein the processor (140) is configured to determine the pulse volume based on the average value of the arterial flow over the multiple heartbeats.

12. The system according to any one of claims 1-11, wherein, The controller (130) is configured to continuously control the ultrasound sensor (120) to measure the arterial flow. The processor (140) is configured to detect changes in the measured arterial flow over time, and The controller is configured to control the blood pressure sensor (110) to measure the blood pressure in response to detecting the change in arterial flow.

13. A method (200) for determining the vascular compliance of an object, comprising: Control (210) the blood pressure sensor to measure the blood pressure of the object's first artery; Control (220) an ultrasound sensor to measure the arterial flow of the second artery of the object, wherein the first artery and the second artery are the same artery or corresponding arteries of the contralateral limb; The pulse pressure (230) is determined based on the measured blood pressure; The pulse volume (240) is determined based on the measured arterial flow rate; and The vascular compliance of the object is determined (250) based on the pulse pressure and the pulse volume.

14. A method (300) for determining hemodynamic parameters of an object, comprising: Obtain the blood pressure measurement result of the subject (310), and optionally obtain the arterial flow measurement result of the subject (312); The method according to claim 13 is used to determine (200) the vascular compliance of the object; and The transfer function is used to process (320) the vascular compliance and blood pressure measurements of the object to determine the hemodynamic parameters, and optionally the transfer function is used to further process the arterial flow measurements of the object to determine the hemodynamic parameters.

15. A computer program comprising computer program code units, wherein when the computer program is run on a computer, the computer program code units are adapted to implement the method according to any one of claims 13 or 14.

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