Device for measuring the blood pressure of a subject

Abstract

The present invention relates to determining a blood pressure of a subject based on a pressure signal measured by using a measurement device having a) a shell that wraps a site through which blood of the subject flows, b) a pressurizing unit that applies pressure to the shell, thereby applying pressure to the wrapped site of the subject, and c) a pressure sensor that measures a pressure signal on the skin of the wrapped site of the subject. For several pressure pulses of the pressure signal, respective features characterizing each pressure pulse are determined, and based on each feature, respective blood pressure determination values are determined, thereby forming a blood pressure determination curve used to determine the blood pressure. This enables determination of the blood pressure with a relatively low computational effort.

Description

Technical Field

[0001] The present invention relates to an apparatus, a method, and a computer program for determining a subject's blood pressure.

Background Art

[0002] EP 3 818 929 A1 discloses a control device for controlling a blood pressure measurement system. The pressurizing unit applies an increasing pressure to a subject's site during a measurement period, while the pressure on the skin of the subject's site having a plurality of pressure pulses is measured. For each of at least some of these plurality of pressure pulses, several characteristics characterizing each pressure pulse are determined, and based on these characteristics, an end measurement time point at which the measurement period is stopped at that time or thereafter is determined. When reaching or after reaching this end measurement time point, that is, when the measurement period stops, the applied pressure decreases and a period after a subsequent blood pressure measurement is started.

[0003] DE 10 2017 110 770 B3 discloses a method for non-invasively determining at least one blood pressure value from a tissue pressure signal using a pressure cuff attached to a person, and this tissue pressure signal has a sequence of tissue pressure pulse curves. At least two individual tissue pressure pulse curves are identified in this tissue pressure signal, and for each of these identified tissue pressure pulse curves, at least one amplitude parameter and one area parameter are determined. The amplitude parameter indicates the amplitude of the identified tissue pressure pulse curve, and the area parameter indicates at least one partial area surrounded by the tissue pressure pulse curve. For each of the identified tissue pressure pulse curves, a pulsation force parameter indicating the shape of the tissue pressure pulse curve is determined based on at least the amplitude parameter and the area parameter. A parameter function indicating the functional relationship between the determined pulsation force parameter of the tissue pressure pulse curve and the corresponding clamp pressure or measurement time in the pressure cuff is generated. Based on this parameter function, a parameter function for determining at least one blood pressure value is determined.

[0004] EP 3 430 992 A1 discloses a blood pressure measurement system configured to surround a body part of a subject, the blood pressure measurement system having pressurizing means for applying pressure to the body part and a kinking-proof shell. When the blood pressure measurement system surrounds the body part, the kinking-proof shell is arranged to be positioned between the pressurizing means and the body part. The blood pressure measurement system is capable of measuring blood pressure by continuously increasing the clamping pressure and stopping the increase above the systolic blood pressure. SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0005] It is an object of the present invention to provide an improved apparatus, method and computer program for determining blood pressure that enables, for example, more accurate determination of blood pressure and / or reduction of computational effort. MEANS FOR SOLVING THE PROBLEMS

[0006] In a first aspect of the present invention, there is provided an apparatus for determining the blood pressure of a subject, the apparatus comprising a pressure signal supply unit configured to provide a measured pressure signal of the subject over a period of time, the pressure signal being a) a shell configured to enclose a site through which blood of the subject flows, b) preferably, a pressurizing part configured to apply pressure to the shell from the outside of the shell, thereby applying pressure to the enclosed part of the subject, and c) a pressure sensor configured to measure a pressure signal on the skin of the enclosed part of the subject measured by using a measurement device having, the pressurizing part increasing or decreasing the applied pressure while the pressure signal is being measured, the measured pressure signal indicating the pulsation of blood and having a plurality of pressure pulses, a pressure signal supply unit, and For each of the plurality of pressure pulses, determine at least one feature characterizing each of these pressure pulses, and based on the at least one determined feature, determine blood pressure determination values for some of the pressure pulses such that several blood pressure determination values are determined for some of the pressure pulses existing at different times, where the several blood pressure determination values determined for the some of the pressure pulses and thus determined for several times form a blood pressure determination curve, and a processor configured to determine blood pressure based on the blood pressure determination curve and has.

[0007] It has been found that blood pressure can be accurately determined even when a single feature is considered for determining the blood pressure determination value. Therefore, it is possible to accurately determine blood pressure with a relatively low computational effort.

[0008] The at least one feature can directly characterize each pressure pulse or can indirectly characterize each pressure pulse. In the latter case, each pressure pulse is processed to determine a feature determination pulse, and at least one feature is determined based on the determined feature determination pulse. This will be described in more detail below. The processor is configured to determine at least one feature characterizing each pressure pulse for all or only some of the plurality of pressure pulses, for example, for at least 5 or at least 10 pressure pulses each.

[0009] The pressure signal supply unit can be, for example, a receiving unit configured to receive a pressure signal from a measuring device and supply the received pressure signal. However, the pressure signal supply unit may also be a storage device in which previously measured pressure signals are stored and can be retrieved to supply the stored pressure signals. The pressure signal supply unit may be or may have a measuring device that measures the pressure signal.

[0010] The processor is adapted to process several blood pressure determination values obtained for several blood pressure pulses in order to obtain a continuous blood pressure determination curve. For example, interpolation can be applied, and optionally, smoothing can also be applied.

[0011] In certain embodiments, the processor is configured to supply a feature determination pulse based on each pressure pulse in order to determine at least one feature for each pressure pulse, and to determine at least one of the following features. The following features are: i) the difference (TPP) between the maximum systolic pressure (TPsys) of the feature determination pulse and the pressure (TPdia) of the feature determination pulse at the end diastolic point, ii) the area (TPA+.top) enclosed by the first upper part of the feature determination pulse, where a) the upper end of the first upper part is at the maximum systolic pressure (TPsys) of the feature determination pulse, and b) the lower end of the first upper part is between the maximum systolic pressure (TPsys) of the feature determination pulse and the pressure value corresponding to the average (TPcl) of the measured pressure (TP), iii) the duration (t(pulse)) of each feature determination pulse, iv) the area (TPA / TPA.norm) of each feature determination pulse, v) the half-width (W50) of each feature determination pulse, and vi) the area (TPA.top) enclosed by the second upper part of the feature determination pulse, where a) the upper end of the second upper part is at the maximum systolic pressure (TPsys) of the feature determination pulse, and b) the lower end of the second upper part is between the pressure value corresponding to the average (TPcl) of the measured pressure (TP) and the pressure (TPdia) of the feature determination pulse at the end diastolic point. It has been found that the determination of blood pressure is further improved by using at least one of these features.

[0012] The characteristic determination pulse for each pressure pulse can be obtained, for example, by subtracting the average measured pressure (TPcl) from each pressure pulse. However, the characteristic determination pulse for each pressure pulse can also be determined in another way. The characteristic determination pulse can also be each measured pressure pulse, where the characteristic determination pulse is directly each pressure pulse. When the characteristic determination pulse for each pressure pulse is obtained by subtracting the average measured pressure (TPcl) from each pressure pulse to determine the area TPA+.top, the pressure value corresponding to the average (TPcl) of the measured pressure (TP) becomes zero.

[0013] The difference (TPP) between the maximum systolic pressure of the characteristic determination pulse and the pressure of the characteristic determination pulse at the end-diastolic point is preferably the difference between the measured pressure of the maximum value and the measured pressure of the minimum value of each pressure pulse, that is, the tissue pressure (TP) of each pressure pulse at the maximum systolic point, that is, the pressure measured on the skin, and the tissue pressure (TP) of each pressure pulse at the end-diastolic point. The duration t(pulse) of each characteristic determination pulse preferably corresponds to the time difference between the end-diastolic point for each pressure pulse and the next end-diastolic point. Further, the area TPA is preferably the area under the curve of each characteristic determination pulse from the end-diastolic point to the next end-diastolic point. This area can be a normalized area and is named "TPA.norm". For example, the area TPA can be normalized by scaling this area by the difference between the maximum pressure and the minimum pressure of each characteristic determination pulse to determine TPA.norm. The half-width W50 corresponds to the width at 50% of the difference between the maximum pressure and the minimum pressure of each characteristic determination pulse. Therefore, it is the width at 50% of the difference between the pressure of the characteristic determination pulse at the maximum systolic point and the pressure of the characteristic determination pulse at the end-diastolic point.

[0014] In a preferred embodiment, the processor is configured to determine the area (TPA+.top) enclosed by the first upper part of the feature determination pulse such that the lower end of the first upper part corresponds to a pressure value that is half of the pressure distance (TPP+) between the maximum systolic pressure (TPsys) of the feature determination pulse and the pressure value corresponding to the average (TPcl) of the measured pressure (TP). In this case, the area enclosed by the first upper part is named TPA+.top50.

[0015] Furthermore, in a preferred embodiment, the processor is configured to determine a blood pressure determination value (TPWP_M) and thus form a blood pressure determination curve (TPW_M-curve) based only on the feature that is the difference (TPP) between the maximum systolic pressure (TPsys) of the feature determination pulse and the pressure of the feature determination pulse at the end-diastolic point (TPdia). Thus, in this embodiment, no other features among the above-described features are used to determine the blood pressure determination value in addition to TPP. It has been found that this makes it possible to further increase the accuracy of determining blood pressure with a relatively low computational effort.

[0016] Furthermore, in a preferred embodiment, the processor is configured to determine a blood pressure determination value (TPWP_M) and thus, based on only one of the following list of features: i) the area (TPA / TPA.norm) of each feature determination pulse, ii) the area (TPA+.top) enclosed by the first upper part of the feature determination pulse, and iii) the area (TPA.top) enclosed by the second upper part of the feature determination pulse form a blood pressure determination curve (TPW_M curve). Thus, in this embodiment, no other features among the above-described features are used to determine the blood pressure determination value in addition to TPA, TPA.norm, TPA+.top, and TPA.top. It has been found that this makes it possible to further increase the accuracy of determining blood pressure and still keep the computational effort relatively low.

[0017] In a further improved embodiment, the processor determines a blood pressure determination value (TPWP_M) and thus forms a blood pressure determination curve (TPW_M-curve) based only on: a) a feature that is the difference TPP between the maximum systolic pressure (TPsys) of the feature determination pulse and the pressure of the feature determination pulse at the end-diastolic point (TPdia), and b) a feature that is the area TPA+.top enclosed by the first upper part of the feature determination pulse. Thus, in this embodiment, no other features among the above-described features are used to determine the blood pressure determination value, in addition to TPP and TPA+.top. In particular, in addition to TPP and TPA+.top50. This has been found to make it possible to further increase the accuracy of determining blood pressure while still keeping the computational effort relatively low.

[0018] In a further improved embodiment, the processor determines a blood pressure determination value (TPWP_M) and thus forms a blood pressure determination curve (TPW_M-curve) based only on: a) a feature that is the difference TPP between the maximum systolic pressure (TPsys) of the feature determination pulse and the pressure of the feature determination pulse at the end-diastolic point (TPdia), and b) a feature that is the area TPA.top enclosed by the second upper part of the feature determination pulse. Thus, in this embodiment, no other features among the above-described features are used to determine the blood pressure determination value, in addition to TPP and TPA.top. This has been found to make it possible to further increase the accuracy of determining blood pressure while still keeping the computational effort relatively low.

[0019] Preferably, the processor is configured to determine the position of the maximum value of the blood pressure determination curve (TPW_M-curve) and determine the blood pressure based on this determined position and the measured pressure (TP). In particular, the processor is configured to determine the blood pressure based on the average (TPcl) of the measured pressure (TP) at the determined position of the maximum value. Determining the blood pressure based on the determined maximum value of the blood pressure determination curve and depending on the pressure on the measured skin, i.e., depending on the tissue pressure, makes it possible to further increase the accuracy of determining the blood pressure.

[0020] The maximum value of the blood pressure determination curve, i.e., instead of or in addition to the curve itself, the maximum value of the derivative of the blood pressure determination curve can also be used. That is, the processor is configured to determine the first position of the maximum value of the blood pressure determination curve and / or the second position of the derivative of the blood pressure determination curve, and determine the blood pressure based on each of the determined first position and / or second position and the measured pressure (TP). In particular, the processor is configured to determine the blood pressure based on the average (TPcl) of the measured pressure (TP) at the determined first and / or second positions.

[0021] In one example, the processor is configured to determine the first peak of the blood pressure determination curve having a peak value greater than a predetermined percentage of one of the peak values of the overall peak of the blood pressure determination curve, and determine the position of the maximum value of the derivative of the blood pressure determination curve by determining the position of the maximum value of the derivative of the blood pressure determination curve before the determined first peak. The predetermined percentage of the overall peak can be determined in advance by calibration. In a preferred embodiment, the predetermined percentage is 90%. The determination of the first peak of the blood pressure determination curve having a peak value greater than a predetermined percentage of one of the peak values of the overall maximum peak of the blood pressure determination curve can be implemented by normalizing the blood pressure determination curve to one of the peak values of the overall maximum peak such that this peak value becomes 1 after normalization. The predetermined percentage is a fixed absolute number between 0 and 1, preferably 0.9. It has been found that restricting the region where the maximum value of the derivative of the blood pressure determination curve is determined can thus further improve the accuracy of determining the blood pressure.

[0022] The maximum value of the derivative preferably points in the direction from the low applied pressure to the high applied pressure. In other words, preferably, the derivative is considered in the direction from the low applied pressure to the high applied pressure regardless of whether the applied pressure is increased or decreased while measuring the pressure signal used to determine the blood pressure.

[0023] Here, it should be noted that the term "before" refers to the direction from a low applied pressure to a high applied pressure. Therefore, when the pressure applied while measuring the pressure signal used to determine blood pressure increases, the term "before" also means earlier in time, and when the pressure applied while measuring the pressure signal used to determine blood pressure decreases, the term "before" means later in time.

[0024] If the blood pressure determination curve has only a single peak, this single peak is the overall maximum peak and is also the first peak having a peak value greater than a predetermined percentage of one of the peak values of this overall maximum peak.

[0025] Preferably, the applied pressure increases while measuring the pressure signal used to determine blood pressure. This is advantageous compared to decreasing the applied pressure while measuring the pressure signal used to determine blood pressure.

[0026] Preferably, the processor receives at least one characteristic of each pressure pulse as input and provides a function that outputs each blood pressure determination value that forms a blood pressure determination curve, along with the blood pressure determination values determined for other pressure pulses. This function has at least one parameter determined by calibration, where the reference blood pressure value is determined very precisely by invasive means and at least one parameter is determined such that the device provides blood pressure values that are measured invasively with high statistical accuracy and precision. In particular, for calibration measurements, pairs of simultaneously recorded invasive and non-invasive blood pressure values from a suitable number of humans with different hemodynamic states are used. Note that the calibration is preferably only performed during the development stage, i.e., not during the actual blood measurement procedure. Calibration can be performed separately for different shell sizes, i.e., preferably for different sizes of blood pressure cuff, or for different groups of shell sizes. For example, different parameters of the function can be determined by calibration for different shell sizes, or for different groups of shell sizes, i.e., at least one parameter for each can be determined for each shell size or for each group of shell sizes.

[0027] For example, the processor is configured to determine a blood pressure determination value (TPWP_M) based on at least one determined feature by raising at least one feature for each pressure pulse to a predetermined exponent. The predetermined exponent can be predefined by calibration as described in the previous paragraph. Thus, the predetermined exponent can be a parameter of the function described in the previous paragraph, and the parameter, i.e., the predetermined exponent in this example, is predefined by calibration. This function can have the following structure. a) Multiply a predetermined coefficient by b) the result of the first power obtained by raising the first feature characterizing each pressure pulse to the first predetermined exponent. Optionally, c) further multiply by the result of the second power obtained by raising the second feature characterizing each pressure pulse to the second predetermined exponent. Optionally, d) further multiply by the result of the third power obtained by raising the third feature characterizing each pressure pulse to the third predetermined exponent, and so on. Here, in a preferred embodiment, the function has only a) and b), or only a), b) and c). Also, the predetermined coefficient can be predefined by calibration. In one example, the predetermined coefficient is 1.

[0028] In one embodiment, a pressure sensor is disposed inside the shell and configured to measure the pressure on the skin of the wrapped site of the subject. However, this pressure sensor can also be arranged in another way to measure the pressure on the skin of the wrapped site of the subject. For example, a pressure sensor pad filled with fluid can be disposed inside the shell and connected via a fluid path, i.e., via a tube filled with fluid, to a pressure sensor outside the shell to measure the pressure on the skin of the wrapped site of the subject.

[0029] In one embodiment, the processor is configured to control the measurement device such that the applied pressure is increased during a measurement period that extends until an end measurement time point, and the applied pressure is decreased during a period following the next subsequent blood pressure measurement. The pressure sensor measures the pressure (TP) on the skin at least during the measurement period. The processor determines an end measurement time point at which or after which the measurement period is stopped based on at least one characteristic determined for at least some of the plurality of pressure pulses, and when or after reaching the end measurement time point, the processor is configured to control the pressurizing unit to decrease the applied pressure and start a period following the next subsequent blood pressure measurement. In particular, at least one characteristic determined for each pressure pulse can be used to determine the end measurement time point such that sufficient pressure data for an accurate determination of blood pressure is measured despite the relatively short measurement period. This enables a reduction in blood pressure measurement time and tissue pressure, i.e., the clamping pressure applied to the skin of the body part during measurement remains substantially below the systolic arterial pressure and ends.

[0030] Preferably, the processor is configured to: a) determine an end decision value for each pressure pulse based on at least one characteristic determined for each pressure pulse such that several end decision values are determined for several pressure pulses existing at different times, where the several end decision values determined for several pressure pulses, and thus for several times, form an end decision curve; and b) determine the end measurement time point based on the end decision curve. By using the end decision curve, the accuracy of determining the end measurement time point can be further enhanced. The processor is adapted to process several end decision values obtained for several pressure pulses in order to obtain a continuous end decision curve. Known mathematical techniques can be used to obtain the continuous curve based on the individual end decision values. For example, interpolation, a fitting procedure, a filtering method, etc. can be applied.

[0031] The processor preferably meets the following conditions a) The maximum value of the end determination curve occurs earlier in time than the maximum value of the blood pressure determination curve. b) The maximum value of the end determination curve occurs at or after the maximum value of the blood pressure determination curve in time, and the decrease after the maximum value of the end determination curve is steeper than the decrease after the maximum value of the blood pressure determination curve, and c) The end determination curve coincides with the blood pressure determination curve. The end determination curve is configured to be determined so as to satisfy one of the above. It has been found that when the end determination curve and the blood pressure determination curve have one of these relationships with each other, the end measurement time point can be determined more accurately.

[0032] In a preferred embodiment, the processor is configured to determine the end measurement time point further based on the blood pressure determination curve. Also, it has been found that when not only the end determination curve but also the blood pressure determination curve is used for determining the end measurement time point, the measurement time can be further shortened.

[0033] Preferably, the processor determines the end measurement time point by determining a) when the end determination curve drops to a value equal to or less than a predetermined percentage of this maximum value after passing through the maximum value, and b) when the blood pressure determination curve reaches or passes through the maximum value. It is more preferable that the predetermined percentage of the maximum value is in the range of 40% to 95%. In particular, when both curves use this method to determine the end measurement time point, it has been found that this time point can be determined very accurately so that the blood pressure is measured very accurately despite the relatively short blood pressure measurement time.

[0034] In one embodiment, the processor is configured to control the pressurizing unit such that the pressurizing unit increases the applied pressure at a first rate during a period before measurement and then increases the applied pressure at a second rate during a subsequent measurement period, where the first rate is greater than the second rate. Accordingly, it is possible to reach the applied pressure at which the measurement period should start relatively quickly, thereby further reducing the overall time required to measure blood pressure.

[0035] In one embodiment, the processor is configured to control the pressurizing unit such that at the end of the period before measurement, the measured pressure is within the range of 15 to 30 mmHg. This ensures that during the measurement period, the pressure on the skin, i.e., the tissue pressure, is measured over a sufficiently wide pressure range, which enables an accurate and precise measurement of blood pressure.

[0036] If the previous diastolic arterial pressure obtained from a previous blood pressure measurement of the same subject is not used by the processor to control the pressurizing unit, a range of 15 to 30 mmHg is preferably applied. If the previous diastolic arterial pressure is used for controlling the pressurizing unit, the measured pressure at the end of the period before measurement may be higher. The control of the pressurizing unit depending on the previously obtained diastolic arterial pressure is described below.

[0037] Note that the pressure at the end of the period before measurement is not the pressure applied between two subsequent blood pressure measurements, particularly the pressure applied before the start of this period before measurement. This pressure is named the "attachment pressure" and should not exceed 15 mmHg.

[0038] In one embodiment, the processor is configured to a) store or receive the previous diastolic arterial pressure obtained from a previous blood pressure measurement, b) determine a first end - of - period measured pressure that should exist at the end of the period before measurement and can thus be regarded as the target pressure, depending on the previous diastolic arterial pressure such that the first end - of - period measured pressure is less than the previous diastolic arterial pressure, and c) control the pressurizing unit such that the measured pressure at the end of the period before measurement is less than or equal to the determined first end - of - period measured pressure. The processor is preferably configured to determine the first end - of - period measured pressure such that its pressure is 90% or less of the previous diastolic arterial pressure. Additionally, this ensures that during the measurement period, the pressure on the skin, i.e., the tissue pressure, is measured over a range wide enough to accurately and precisely determine blood pressure.

[0039] In one embodiment, the processor further stores or receives the time at which the previous diastolic arterial blood pressure was measured, and is configured to determine a first end measurement pressure depending on i) the previous diastolic arterial pressure and ii) the temporal distance to the blood pressure measurement at which the previous diastolic arterial pressure was measured, indicated by the stored time. The diastolic arterial pressure can vary over time, where the first end measurement pressure can still be determined relatively accurately considering the temporal distance to the blood pressure measurement at which the previous diastolic arterial blood was measured. Thus, although there is this uncertainty regarding the change in diastolic arterial pressure over time, the end of the pre-measurement period can be determined such that during the subsequent measurement period, the pressure on the skin, i.e., the tissue pressure, is measured over a range wide enough to accurately and precisely determine the blood pressure.

[0040] The processor can further be configured to a) store or receive the previous pressure measured by the pressure sensor during the period from the end of the previous measurement period of the previous blood pressure measurement to the start of the pre-measurement period, and b) control the pressurizing unit such that the measured pressure at the start of the pre-measurement period is below a predetermined pressure value, based on the stored or received previous measurement. The predetermined pressure value is preferably 15 mmHg or less, more preferably 10 mmHg or less.

[0041] The pressure measured at the start of the period before the measurement can be regarded as the mounting pressure that exists during the measurement pause between two subsequent blood pressure measurements, i.e., the mounting pressure that exists before the start of each blood pressure measurement. This mounting pressure is preferably controlled to achieve a given or pre-set value, i.e., a predefined pressure value. This control is preferably carried out so as to adapt to changes in the volume of the body part, for example, an increase caused by tissue edema (such as capillary leakage in sepsis, increased circulating blood volume), or a decrease due to reduction of tissue edema or decreased circulating blood volume. This should in particular prevent venous congestion caused by venous reflux insufficiency due to compression of the veins at a tissue pressure higher than the venous pressure in each body part during the measurement pause, i.e., between two subsequent blood pressure measurements. In a preferred embodiment, the pressure on the skin, which is also regarded as the tissue pressure, is continuously measured throughout the procedure of performing one or several blood pressure measurements, and the pressurizing part is controlled to prevent venous congestion during the measurement pause.

[0042] The shell is preferably an anti-kink shell. This anti-kink shell is preferably arranged (or sandwiched) between the pressurizing part, i.e., for example, a fluid bag and the part of the subject to be wrapped. A relatively rigid anti-kink shell prevents, or at least significantly reduces, the occurrence of wrinkles or kinks on the surface that compresses the pressurizing part, especially the fluid bag. As a result, there are no wrinkles that adversely affect the amplitude, shape, and reproducibility of the measurement signal, so the measurement accuracy can be improved.

[0043] The anti-kink shell preferably exhibits a rigidity that is significantly greater than the rigidity of the wall of the fluid bag when the pressurizing part has the above-mentioned fluid bag. Preferably, the rigidity of the anti-kink shell is selected to ensure that no buckling of the anti-kink shell occurs when pressure is applied to the wrapped part of the subject for measuring the blood pressure of the subject. At the same time, the anti-kink shell should be flexible enough so that, for example, when the pressure is applied by the pressurizing part by expanding the fluid bag of the pressurizing part, the anti-kink shell can reduce its inner diameter.

[0044] The kink prevention shell is a reinforcing component configured to ensure the rigidity of a measurement device for blood pressure measurement. The kink prevention shell may be the only reinforcing component of the measurement device, and this reinforcing component exhibits structural robustness or strength and is configured to provide rigidity against compressive forces during blood pressure measurement. In particular, the reinforcing kink prevention shell may be pressed against the enclosed part of the subject without any additional intervening reinforcing elements, i.e., there is preferably no additional element between the reinforcing kink prevention shell and the enclosed part of the subject that provides any reinforcing function.

[0045] Preferably, the kink prevention shell is a monolithic reinforcing shell. Such a design makes it possible to provide sufficient rigidity in a direct way.

[0046] Preferably, the kink prevention shell is dimensioned to overlap when surrounding the subject's part. In other words, the kink prevention shell preferably completely surrounds the subject's body part at least from when pressure is applied by the pressurizing part. Thus, along the entire circumference of the measurement device, kinking or wrinkling can be prevented or at least significantly reduced.

[0047] Due to the adaptation of the kink prevention shell, kinking or wrinkling is prevented or at least significantly reduced, so that when the inner diameter of the shell decreases, for example, by supplying pressurized fluid, preferably air, to a fluid bag of a pressurizing element, the overlapping parts of the shell, i.e., the outer ends of the shell, should be able to move or slide relative to each other. Thus, the measurement device, in particular the kink prevention shell, is preferably designed such that the overlapping parts can slide easily relative to each other. For example, the surface parts of the shell that slide in direct contact with each other can exhibit a relatively low coefficient of friction, for example, by selecting the material and / or surface structure accordingly. The term "low coefficient of friction" in the present invention refers to the coefficient of friction between two flat surfaces that is less than 0.5, preferably less than 0.3, more preferably less than 0.2, and even more preferably less than 0.1.

[0048] In one example, the shell, especially the kink prevention shell, is made of metal and / or plastic, especially fiber reinforced plastic. For example, this shell is made of a thermoplastic material, preferably polyurethane or polyolefin, more preferably made of polyethylene and / or polytetrafluoroethylene (PTFE), or made of or coated with a thermoplastic material coated with PTFE. For example, this shell may be made of a thermoplastic material that provides a surface on which an adhesive can be permanently adhered. When this shell has a fiber reinforced plastic material, the fibers are natural fibers, organic fibers, or inorganic fibers.

[0049] In particular, when the shell is made of a plastic material, in one example, the shell exhibits a thickness within the range of 0.25 mm to 6 mm, more preferably within the range of 1 mm to 3 mm, and even more preferably within the range of 1.0 mm to 2.0 mm. For example, the shell can have a thickness of 1.5 mm, especially for adults. Or, the shell can have a thickness of 0.5 mm, especially for infants and young children. In a preferred embodiment, the shell is made of polyethylene (PE) with a thickness of 1.5 mm.

[0050] In one example, in order to prevent torsion on the one hand and allow a reduction in the inner diameter on the other hand, the kink prevention shell exhibits an elastic modulus exceeding 50 MPa, more preferably within the range of 100 MPa to 10 GPa, and even more preferably within the range of 200 MPa to 1 GPa.

[0051] In another aspect of the present invention, a method for determining the blood pressure of a subject is presented, and this method A step of supplying a measured pressure signal (TP) of a subject over a period of time by a pressure signal supply unit, wherein the pressure signal (TP) comprises: a) a shell configured to enclose a site through which the subject's blood flows; b) a pressurizing unit preferably configured to apply pressure from the outside of the shell to the shell, thereby applying pressure to the enclosed site of the subject; and c) a pressure sensor configured to measure a pressure signal on the skin of the enclosed site of the subject, wherein the pressurizing unit increases or decreases the applied pressure while the pressure signal is being measured, and the measured pressure signal indicates the pulsation of blood and is measured using a measuring device having a plurality of pressure pulses. For each of the plurality of pressure pulses, a step of determining, by a processor, at least one characteristic that characterizes each pressure pulse. A step of determining, for some of the pressure pulses present at different times, a blood pressure determination value (TPWP_M) for each pressure pulse based on at least one characteristic determined by the processor, such that several blood pressure determination values (TPWP_M) are determined for some of the pressure pulses and, thus, for some times, and the several blood pressure determination values (TPWP_M) form a blood pressure determination curve (TPW_M-curve), and A step of determining blood pressure by the processor based on the blood pressure determination curve (TPW_M-curve). It has.

[0052] In a further aspect of the invention, a computer program for determining blood pressure is presented, the computer program having program code means for causing an apparatus for determining blood pressure to execute the steps of the method for determining blood pressure.

[0053] The device, method, and computer program can be adapted to continuously determine blood pressure, i.e., such that several subsequent blood pressure measurements are performed, or to discontinuously determine blood pressure, i.e., for example, to determine it once.

[0054] It should be understood that the processor according to claim 1, the method according to claim 13, and the computer program according to claim 14 have similar and / or identical preferred embodiments, in particular as defined in the dependent claims.

[0055] It should be understood that the preferred embodiments of the present invention can be any combination of the dependent claims or the above embodiments with the respective independent claims.

[0056] These and other aspects of the present invention will become apparent from and be elucidated with reference to the embodiments described hereinafter.

Brief Description of the Drawings

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DETAILED DESCRIPTION OF THE INVENTION

[0058] FIG. 1 schematically and illustratively shows an apparatus 1 for determining the blood pressure of a subject. The apparatus 1 has a shell 4 as seen in FIG. 2, and this shell is configured to enclose a site 5 through which the subject's blood flows. In this embodiment, the site 5 of the subject is the subject's arm, and in FIG. 2, the brachial artery 11 is shown within this arm 5, and the arrow within the brachial artery 11 indicates the direction of blood flow away from the heart. The apparatus 1 further has a pressure sensor 7 disposed inside the shell 4 and configured to measure the pressure on the outer skin of the enclosed arm 5 of the subject. The measured pressure can also be regarded as the tissue pressure (TP). As shown in FIG. 2, the pulse wave in the brachial artery 11 generates a pressure wave 12 that is transmitted to the pressure sensor 7 through the tissue of the arm 5. For clarity, the shell 4 is not shown in FIG. 1.

[0059] The device 1 further has a cuff 6 that can be inflated by using a pump 8 that surrounds the shell 4 and applies pressure to the shell 4 from the outside thereof, thereby applying pressure to the arm 5 of the subject wrapped thereby. Since the cuff 6 and the pump 8 enable the application of pressure to the shell 4 and thereby to the arm 5 of the subject wrapped thereby, the cuff 6 and the pump 8 can be regarded as forming the pressurizing parts 6, 8. Further, the shell 4, the pressurizing parts 6, 8, and the pressure sensor 7 can be regarded as components of a measuring device controlled by the processor 3. The shell 4 provided with the cuff 6 is preferably a kink-preventing shell cuff as described in WO 2014 / 121945 A1.

[0060] The processor 3 is configured to control the measuring device such that the pressurizing parts 6, 8 increase the pressure applied during a measurement period that extends until the end measurement time point and then decrease the pressure applied during the period after the next blood pressure measurement, and such that the pressure sensor 7 measures the pressure on the skin, i.e., the tissue pressure TP, at least during said measurement period. Further, the processor 3 is configured to control the pressurizing parts 6, 8 such that the pressurizing parts 6, 8 increase the pressure applied at a first rate during the period before measurement and then increase the pressure applied at a second rate during the subsequent measurement period, where the first rate is greater than the second rate. The control of the measuring device such that the cuff 6 expands and thus the applied pressure increases is shown in FIG. 1, i.e., the thick arrow indicates the situation of expansion.

[0061] The device 1 has a valve 20, and when the valve 20 is opened, the compressed air in the system is released from this system into the ambient atmosphere, making it possible to contract the cuff. In FIG. 3, the situation of contraction in which the pump 8 is switched off is indicated by the thick arrow.

[0062] Processor 3 can be regarded as having a control unit 10 for controlling pump 8 and valve 20, and a processing unit 11 specifically configured to execute several calculations further described below. The apparatus 1 can also have, for example, a display 22 for displaying the measured blood pressure value.

[0063] During a pre-measurement period that can also be regarded as a high-speed inflation period, the processor 3 controls the apparatus 1 such that the valve 20 is closed and the pump 8 inflates the cuff 6 at a larger first rate. In the subsequent measurement period, the processor 3 again controls the apparatus 1 such that the valve 20 is closed, but the pump 8 is controlled so that the inflation of the cuff 6 continues at a lower second rate. Thus, the measurement period can also be regarded as a low-speed inflation period.

[0064] FIG. 4 schematically and illustratively shows the measured pressure TP with respect to time t. The first inflation in the pre-measurement period starts from the tissue pressure TP which is the attachment pressure Patt measured in the non-inflated cuff 6. This attachment pressure Patt is, for example, in the range of 0 to 15 mmHg. It has been found that an attachment pressure Patt of 15 mmHg or less does not cause venous congestion for 12 hours or more, and as a result, the assembly of the cuff 6 and the shell 4 is suitable for longer-term monitoring. For this reason, the attachment pressure Patt is preferably 15 mmHg or less. In FIG. 4, the arrow 30 indicates the start of the pre-measurement period, that is, the start of the high-speed inflation period. During this pre-measurement period, the part of the overall tissue pressure range where there is no or almost no information for determining blood pressure should be passed through as quickly as possible. Thus, during the pre-measurement period, the inflation rate is preferably as large as possible. For example, the inflation rate with respect to the tissue pressure TP is 8 mmHg / s or more. This pre-measurement period with a high inflation rate ends at the tissue pressure value indicated by "TPlow" in FIG. 4.

[0065] The tissue pressure value TPlow also indicates the start of the measurement period at a slower second inflation rate. In FIG. 4, the start of this measurement period, which can also be regarded as the low-speed inflation period, is indicated by arrow 31. In one embodiment, the processor 3 is configured to control the pump 8 such that the measured pressure TPlow is within the range of 15 to 30 mmHg at the end of the period before measurement. Thus, in one embodiment, the tissue pressure TPlow can be predefined such that its pressure is a value of 15 to 30 mmHg. However, in a situation where the diastolic arterial pressure determined in the previous measurement (DAPprev) is available, the tissue pressure TPlow may depend on this diastolic arterial pressure, and the tissue pressure TPlow may be larger. This larger TPlow is schematically shown in FIG. 4. For example, the processor 3 can be configured to store (or access a memory storage device having it) the previous diastolic arterial pressure DAPprev. The previous diastolic arterial pressure DAPprev is obtained by a previous blood pressure measurement and can be used to determine the tissue pressure TPlow. The tissue pressure TPlow should exist at the end of the period before measurement, that is, at the end of the first inflation period, and thus can also be regarded as the first end measurement pressure. The tissue pressure TPlow is determined depending on the previous diastolic arterial pressure DAPprev such that this tissue pressure TPlow is smaller than the previous diastolic arterial pressure DAPprev. Preferably, the processor is configured to control the pump 8 such that the measured pressure at the end of the period before measurement is equal to the determined first end measurement pressure TPlow. In one embodiment, the processor 3 determines the tissue pressure TPlow at the end of the period before measurement such that the tissue pressure TPlow does not exceed a predetermined percentage of the previous diastolic arterial pressure DAPprev. This enables accurate calculation of blood pressure and ensures that all necessary tissue pressure pulse curves can be recorded. The calculation of blood pressure based on the measured tissue pressure will be further described below. The predetermined percentage is preferably 90%.

[0066] Blood pressure can vary from measurement to measurement, for example, for clinically relevant events to occur in a subject. Diastolic arterial pressure (DAP) has been found to be able to drop by about 30% within one minute in the most severe situations of acute blood loss during surgery. To cope with these possible blood pressure changes, the processor 3 can be adapted to determine the tissue pressure TPlow depending on the previous diastolic arterial pressure DAPprev and the duration of the rest time between measurements. Thus, the processor 3 further stores (or accesses a memory storage device having it) the time at which the previous diastolic arterial pressure DAPprev was measured, and is configured to determine the first end measurement pressure TPlow depending on i) the previous diastolic arterial pressure DAPprev and ii) the time distance to the blood pressure measurement at which the previous diastolic arterial pressure DAPprev was measured indicated by the stored time. An exemplary specific equation for determining this first end measurement pressure TPlow is further shown below.

[0067] The second inflation rate applied during the measurement period is preferably in the range of 1 mmHg / s to 6 mmHg / s, the lowest inflation rate is preferably 1.5 mmHg / s, and most preferably 2.5 mmHg / s. It has been found that the second inflation rate within this range enables accurate blood pressure determination. It should be noted that these rates refer to the change in the tissue pressure TP measured by the pressure sensor 7.

[0068] In one embodiment, the slow second inflation rate depends on the heart rate (HR) and / or the pulse pressure (PP) which is the difference between the systolic blood pressure and the diastolic blood pressure. For example, the second inflation rate can increase with an increase in the heart rate and an increase in the pulse pressure PP. This increase may be linear or may be represented by another functional relationship. In one embodiment, this functional relationship is such that the inflation rate of the tissue pressure when the heart rate HR is 40 beats per minute and the pulse pressure PP is 20 mmHg is 1 mmHg / s, and the inflation rate of the tissue pressure, i.e., the second slow inflation rate, when the heart rate HR is 80 beats per minute and the pressure pulse PP is 100 mmHg is 10 mmHg / s. The measurement period ends at the end measurement time point 32, and thereafter, since it is not necessary to collect tissue pressure data after this end measurement time point 32, preferably, immediate rapid contraction continues at the maximum possible reduction rate.

[0069] In FIG. 4, the time interval 40 indicates the inflation - contraction period from the start 30 of the high - speed inflation until the tissue pressure TP falls below 20 mmHg during the high - speed contraction to enable venous return. The period 41 indicates the cycle time which is the time from the start of the measurement to the start of the next measurement, and the period 42 indicates the rest time which is the difference between the inflation - contraction period 40 and the cycle time 41.

[0070] FIG. 4 shows the average pressure TPcl which can be regarded as the tissue clamping pressure applied to the tissue when the cuff 6 is attached to the arm 5 of the subject, for example, the upper arm. The average pressure TPcl can be calculated by applying a low - pass filter to the tissue pressure TP, and this low - pass filter can be arranged within the processor 3. The low - pass filter is preferably set such that the average pressure TPcl includes only frequencies below the predicted minimum pulse rate (PRni). A preferred low - pass filter will be further described below. The processor 3 is preferably configured to determine the alternating component TPac of the tissue pressure by subtracting the average pressure TPcl from the measured tissue pressure TP (i.e., TPac = TP - TPcl). In FIG. 4, the TPac curve is shown enlarged by a factor of 2 for clarity.

[0071] During the low-speed inflation period, i.e., during the measurement period, the TP pulse curve and / or the TPac pulse curve are recorded, and these are analyzed simultaneously, i.e., online. The TP pulse curve and / or the TPac pulse curve have a tissue pressure waveform (TPW) that has information enabling the accurate determination of blood pressure. Since blood pressure is measured non-invasively (although with an accuracy comparable to that of invasively measured blood pressure), it can be abbreviated as niBP, meaning "non-invasive blood pressure". In FIGS. 5 to 8, the TPac pulse curve is shown schematically and illustratively.

[0072] In the following, the TPac pulse curve is used to determine the characteristics for the pressure pulse 9. Thus, the TPac pulse curve can be regarded as a characteristic determination pulse curve or a characteristic determination pulse. Therefore, FIGS. 5 to 8 show the characteristic determination pulse curve or the characteristic determination pulse 29 that is the TPac pulse. In another embodiment, the characteristic determination pulse may be directly the TP pulse curve, i.e., the pressure pulse 9 can be directly used to determine the characteristics. The processor 3 is configured to determine at least one characteristic characterizing each of the plurality of pressure pulses 9 for each of the pressure pulses.

[0073] In one embodiment, the processor 3 is configured to determine, as a characteristic for each pressure pulse, the difference TPP between the measured pressure of the maximum value and the measured pressure of the minimum value of each characteristic determination pulse 29. This characteristic is described below with reference to FIG. 5.

[0074] The difference TPP is the difference between the maximum systolic pressure (TPsys) of the characteristic determination pulse and the pressure of the characteristic determination pulse at the end-diastolic point, which is preferably the minimum pressure of each characteristic determination pulse (TPdia). In FIG. 5, as well as in FIGS. 6 to 8, the terms "t.start" and "t.stop" respectively indicate the start and end of each of the pulses 29.

[0075] The processor 3 is also configured to determine a pulse duration (t(Pulse)), which is the time difference between the end point of the expansion of the feature determination pulse 29 and the next end point of the expansion. This feature can also be defined as the time difference between the start (t.start) and the end (t.stop) of each pulse. This feature is shown in FIG. 6.

[0076] The processor 3 can be adapted to determine a pulse area (TPA) of each pulse 29, which is the area under each pulse curve within the time defined by t.start to t.stop and has a range from the pressure (TPdia) of the feature determination pulse at the end point of the expansion to the maximum systolic pressure (TPsys) of the feature determination pulse. Preferably, as shown in FIG. 6, the pulse area TPA is scaled to TPP = 1. This scaled pressure pulse area is called "TPA.norm".

[0077] The processor 3 is also adapted to determine a half-value pulse width (W50) of each pulse 29, as shown in FIG. 7.

[0078] Furthermore, as schematically shown in FIG. 8, the processor 3 is adapted to determine an area TPA+.top50 enclosed by the first upper part of the feature determination pulse 29. The upper end of the area TPA+.top50 enclosed by this first upper part is at the maximum systolic pressure TPsys of the feature determination pulse 29, and the lower end of the area TPA+.top50 of this first upper part is between the maximum systolic pressure TPsys of the feature determination pulse 29 and the pressure value corresponding to the average TPcl of the measured pressure TP. Since the feature determination pulse 29 is determined by subtracting the average TPcl from the measured pressure TP, the pressure value corresponding to the average TPcl of this measured pressure TP is zero. Preferably, the processor 3 is such that the lower end of the first upper part is at a pressure value corresponding to half of the pressure distance TPP+ between the maximum systolic pressure TPsys of the feature determination pulse and the pressure value corresponding to the average TPcl of the measured pressure TP, configured to determine the area TPA+.top50 enclosed by the first upper part of the feature determination pulse. At this time, the corresponding area is named TPA+.top50.

[0079] FIGS. 5 to 8 show the TPac pulse curve, such that in this example, features are also defined based on the TPac pulse curve. However, as described above, it is also possible to define these or other features based on the TP pulse curve.

[0080] Processor 3 is further configured to determine a blood pressure determination value TPWP_M for each of several pressure pulses, based on at least one determined feature, such that several blood pressure determination values TPWP_M are determined for several pressure pulses existing at different times, and thus, for several times, and these several blood pressure determination values TPWP_M determined for several pressure pulses form a blood pressure determination curve TPW_M-curve. Processor 3 is configured to determine blood pressure based on the blood pressure determination curve TPW_M-curve, as described, for example, in WO 2018 / 210931 A1. In particular, processor 3 is configured to determine the position of the maximum value (TPW_M-curve.max) of the blood pressure determination curve TPW_M-curve and to determine blood pressure based on the determined position and the measured pressure TP. For example, processor 3 is configured to use the following formula SAPni = α · (TPcl@TPW_M-curve.max) (1) to determine the systolic arterial blood pressure (SAPni) based on the average TPcl of the measured pressure TP at the determined position of the maximum value (TPW_M-curve.max). Here, the parameter α can be determined in advance by calibration.

[0081] In fact, processor 3 is configured to determine the position of the maximum value of the blood pressure determination curve TPW_M-curve and / or, for example, the position of the derivative of the blood pressure determination curve TPW_M-curve, for example, the first derivative, and to determine blood pressure based on one or both of the determined position and the measured pressure TP. For example, processor 3 is configured to use the following formula SAPni = α' · (TPcl@TPW_M-curve.max) + β' · (TPcl@TPW_M-curve'.max) It can be configured to determine the systolic arterial pressure based on the average TPcl of the measured pressure TP at one or both of the determined positions, where TPW_M-curve' refers to the derivative of the TPW_M-curve, and the parameters α' and β' can be determined in advance by calibration.

[0082] Preferably, the processor is configured to receive at least one feature of each pressure pulse as an input and provide a function that outputs each blood pressure determination value that forms a blood pressure determination curve, together with the blood pressure determination values determined for other pressure pulses. This function has at least one parameter determined by calibration, where the reference blood pressure value is determined very accurately by invasive means, and at least one parameter is determined so that the device provides blood pressure values that are very accurately measured invasively with high statistical accuracy and precision.

[0083] In a preferred embodiment, the processor 3 is configured to form a blood pressure determination curve TPW_M-curve based on a blood pressure determination value TPWP_M that depends only on the feature that is the difference TPP between the maximum systolic pressure TPsys of the feature determination pulse and the pressure TPdia of the feature determination pulse at the end-diastolic point. Thus, in one embodiment, the function used to determine the blood pressure determination value TPWP_M depends on TPP but not on any other feature of the pressure pulse. In particular, the blood pressure determination value TPWP_M is given by the following formula TPWP_M = d1·TPP exp1 (2) and can be determined according to. Here, d1 and exp1 are predetermined constants. For example, d1 and exp1 can be determined in advance by calibration. However, it has been found that d1 and exp1 can be selected to be equal to 1, i.e., d1 = 1 = exp1, such that, for example, TPWP_M = TPP.

[0084] Furthermore, in a preferred embodiment, the processor 3 is configured to form a blood pressure determination curve TPW_M-curve based on a blood pressure determination value TPWP_M that depends only on a) a feature that is the difference TPP between the maximum systolic pressure TPsys of the feature determination pulse and the pressure TPdia of the feature determination pulse at the end diastolic point, and b) a feature that is the area TP A+.top50 enclosed by the first upper part of the feature determination pulse. Thus, in one embodiment, the function used to determine the blood pressure determination value TPWP_M depends on TPP and TP A+.top50, but does not depend on further features of the pressure pulse. In particular, the blood pressure determination curve TPW_M-curve is given by the following mathematical formula TPWP_M = d2·TP A+.top50 exp2 ·TPP exp3 (3) and can be determined accordingly. Here, d2, exp2, and exp3 are predetermined constants. For example, d2 can be made equal to 1, i.e., d2 = 1, and exp2 and exp3 can be determined in advance by calibration. However, it is also possible for the constant d2 to be determined by calibration. In a preferred embodiment, both d2 and exp3 are equal to 1 (d2 = 1, exp3 = 1), and exp2 is equal to 0.7 (exp2 = 0.7).

[0085] The processor 3 is preferably further configured to determine an end measurement time point 32 at which or after which the measurement period is stopped, based on at least one feature determined for a plurality of pressure pulses 9. In particular, the processor 3 can be configured to determine an end determination value TPWP_E for each pressure pulse, based on at least one feature determined for each pressure pulse.

[0086] Preferably, the processor is also configured to provide a function that receives at least one feature of each pressure pulse as input and outputs each end determination value TPWP_E that forms an end determination curve together with the end determination values determined for other pressure pulses. Further, this function has at least one parameter that can be determined by calibration. In particular, the end determination value TPWP_E is given by the following formula, TPWP_E = d3·TPP exp4 (4) or according to the following formula TPWP_E = d4·TPA +.top50 exp5 ·TPP exp6 (5) where d3, d4, exp5 and exp6 are predetermined constants. For example, making d3 and / or d4 equal to 1, i.e., d3 = 1 and d4 = 1, while exp4, exp5 and exp6 are determined in advance by calibration. In one embodiment, the constant d3 and / or the constant d4 can also be determined by calibration and can in particular be other than 1.

[0087] It should be noted that the end determination value TPWP_E can also be determined as follows.

[0088] Specifically, the processor 3 is configured to multiply a) the power of the determined pulse area TPA.norm at a predetermined seventh exponent (exp7) by b) the power of the determined difference TPP at a predetermined eighth exponent (exp8). Accordingly, the end determination value TPWP_E can be calculated according to the following formula using predetermined exp7≠0, exp8≠0 TPWP_E = TPA.norm exp7 ·TPP exp8 (6)

[0089] ​Processor 3 is configured to determine the end determination value TPWP_E by: a) raising the determined pulse area TPA.norm to a predetermined ninth exponent (exp9); b) dividing the result by the determined pulse duration t(pulse) raised to a predetermined tenth exponent (exp10); and c) multiplying the resulting quotient by the determined difference TPP raised to a predetermined eleventh exponent (exp11). This can be represented by the following equation using predetermined exp9≠0, exp10≠0, and exp11≠0: TPWP_E = TPA.norm exp9 / t(pulse) exp10 · TPP exp11 (7) which can be expressed as.

[0090] Processor 3 is also configured to determine the end determination value for each pressure pulse based on multiplying the calculation result obtained by using, for example, Equation (6) or Equation (7) by the determined pulse area TPA.norm raised to a further predetermined exponent of the half-width (W50). For example, when Equation (7) is multiplied by the half-width W50, Equation (8) is as follows using predetermined exp12≠0, exp13≠0, exp14≠0, and exp15≠0: TPWE_E = TPA.norm exp12 / t(pulse) exp13 · TPP exp14 · W50 exp15 (8) results.

[0091] Therefore, in this embodiment, by combining and weighting the amplitude parameter and the area parameter based on at least TPP and TPA.norm for each pulse curve, TPWP_E reflecting the characteristic value for each pulse curve can be calculated, and any of TPWP_E can be extended by multiplying by the determined exponent of W50.

[0092] As described above, the exponents of different mathematical expressions are determined in advance by calibration. For example, in a preferred embodiment, Equation (7) is used with exponents exp9 = 1.1, exp10 = 0.4, and exp11 = 0.5.

[0093] Processor 3 preferably meets the following conditions a) The maximum value of the end determination curve (TPW_E-curve.max) occurs earlier in time than the maximum value of the blood pressure determination curve (TPW_M-curve.max), b) The maximum value of the end determination curve (TPW_E-curve.max) occurs when or after the maximum value of the blood pressure determination curve (TPW_M-curve.max), and the decrease after the maximum value of the end determination curve TPW_E-curve is steeper than the decrease after the maximum value of the blood pressure determination curve TPW_M-curve, and c) The end determination curve TPW_E-curve coincides with the blood pressure determination curve TPW_M-curve is configured to determine the end determination curve TPW_E curve so as to satisfy one of the above. Therefore, the parameters of the function are preferably a) TPW_E-curve.max occurs earlier in time than TPW_M-curve.max, or b) TPW_E-curve.max occurs at or after TPW_M-curve.max in time, but the TPW_E-curve has a negative derivative with an absolute derivative value greater than the absolute derivative value of the negative derivative of the blood pressure determination curve TPW_M-curve after reaching the maximum value, or c) TPW_E-curve coincides with TPW_M-curve, that is, the end determination curve and the blood pressure determination curve coincide are defined in advance as follows.

[0094] In FIG. 9, the blood pressure determination curve TPW_M-curve and the end determination curve TPW_E-curve are exemplarily shown, where these curves are normalized so that their respective maximum values correspond to 100%.

[0095] To minimize the stress on the subject, it is desirable to complete each blood pressure measurement as quickly as possible. Since the maximum value of the blood pressure determination curve TPW_M-curve is used for non-invasive blood pressure determination in blood pressure measurement, as soon as the maximum value of the blood pressure determination curve TPW_M-curve is formed and thus can be fully determined, the blood pressure measurement can be terminated. Therefore, during the measurement period, it is investigated when the end criterion that defines the end measurement time point is reached, and in order to determine when this end criterion is reached and thus to determine the end measurement time point, preferably, the end determination curve TPW_E-curve and the blood pressure determination curve TPW_M-curve are used. For example, when the end determination curve TPW_E-curve forms a maximum value, for each newly measured TP pulse curve, that is, for each newly measured TP pulse, a) whether the end determination curve TPW_E-curve has decreased until it falls below a certain percentage of the maximum value of the end determination curve TPW_E-curve, where the percentage is preferably in the range of 40% to 95%, and b) whether the blood pressure determination curve TPW_M-curve has formed a maximum value, that is, whether it has reached its maximum value or passed its maximum value can be examined. The processor 3 can be configured to determine the end determination time point 32 as the time point when both conditions a) and b) are satisfied.

[0096] To determine whether the blood pressure determination curve TPW_M-curve has successfully reached or passed its maximum value, it can be detected whether the blood pressure determination curve TPW_M-curve has dropped after the maximum value.

[0097] In one embodiment, the blood pressure determination curve TPW_M-curve can be a smoothed curve such that the maximum value of this blood pressure determination curve is also smoothed. The smoothing procedure used to smooth the blood pressure determination curve can include, for example, filtering and / or fitting. Further, after the smoothed maximum value, several pressure pulses are considered to clearly detect this smoothed maximum value, where the number of these several pulses can be determined in advance or can depend on the heart rate of the subject. For example, this number increases with an increase in heart rate. In one embodiment, this number is 3 for a heart rate of 60 beats per minute and 10 for a heart rate of 200 beats per minute.

[0098] To smooth the blood pressure determination curve TPW_M-curve, a moving average filter, particularly a variable moving average filter, can be used, which is applied to the blood pressure determination value TPWP_M determined for the pressure pulse. The window used for averaging can be fixed or variable. In the latter case, the window preferably has a maximum duration of, for example, 8 seconds. The use of this filter causes a filter delay, and the minimum filter delay is the same length as the total duration of several pulses. Having a filter delay of the length of several pulses is sufficient to safely determine the descending smoothed blood pressure determination curve TPW_M-curve and thus the maximum value of this blood pressure determination curve TPW_M-curve. This means that as soon as a decrease in the smoothed blood pressure determination curve TPW_M-curve is detected, the measurement period can be ended without the need to collect more pressure pulses. This is possible in this example because, for example, by smoothing the blood pressure determination curve TPW_M-curve twice using at least 3 pressure pulses of TP and a relatively large variable moving average filtering window of up to 8 seconds (2×8 second filter), the disturbing cardiorespiratory interaction can be removed at an estimated 95% of the measurement. These smoothing filtering windows can each be adapted to the respiratory rate and tidal volume, thereby making it possible to improve the exclusion of unwanted disturbances of the TPW_M-curve caused by cardiorespiratory interaction.

[0099] In FIG. 9, when the end determination curve TPW_E-curve falls below 90% of the maximum value of this end determination curve TPW_E-curve, both of the above-described conditions a) and b) are satisfied. Due to the filter delay, after both conditions a) and b) are satisfied, the measurement ends with several tissue pressure pulses.

[0100] The continuous TPW_E-curve and continuous TPW_M-curve shown in FIG. 9 were obtained by filtering the values TPWP_E and TPWP_M determined for different pressure pulses, respectively. This filtering leading to the filter delay will be further described below. In FIG. 9, the filter delay results in two additional pressure pulses such that a rapid contraction of cuff 6 starts two pressure pulses after both conditions a) and b) are satisfied.

[0101] The end determination curve TPW_E-curve having a maximum value occurring several seconds before the maximum value of the blood pressure determination curve TPW_M-curve in time can shorten the measurement period, that is, shorten the slow inflation time and reduce the amount of pressure applied to the subject. After reaching t(a_end), that is, after the end determination curve TPW_E-curve reaches a point where it falls below a predetermined percentage of the maximum value of this TPW_E-curve, if the TPW_M-curve has several maximum values, the largest maximum value of the blood pressure determination curve TPW_M-curve found so far is the absolute maximum value (TPW_M-curve.max) of the blood pressure determination curve TPW_M-curve when the blood pressure determination curve TPW_M-curve is decreasing at time point t(a_end). Otherwise, in one embodiment, the measurement continues until the next maximum value of the TPW_M-curve and the maximum value of the blood pressure determination curve (TPW_M-curve.max) are determined thereafter.

[0102] When not using the end determination curve TPW_E-curve having a maximum value that occurs before the maximum value of the blood pressure determination curve TPW_M-curve in terms of time, it is necessary to continue the low-speed inflation until the blood pressure determination curve TPW_M-curve falls below a specific percentage of its maximum value. On average, by using the end point determination curve TPW_E-curve having a maximum value that occurs before the maximum value of the blood pressure determination curve TPW_M-curve in terms of time, blood pressure measurement can end approximately 20 to 60 seconds later at TPcl within the range of 70 to 95% of the systolic arterial pressure (SAP). This is significantly lower than the end pressure level of conventional oscillometric niBP measurement. Therefore, blood pressure measurement ends when the clamp pressure reaches approximately SAP + 20 mmHg. In the case of using the device 1 described above with reference to FIG. 1, when the measurement ends, the tissue pressure TP drops to Patt as quickly as possible and remains there for a certain period of time, preferably for about 20% of the inflation-contraction period 40 shown in FIG. 4, before another measurement is started.

[0103] The processor 3 is configured to determine blood pressure based on the blood pressure determination curve TPW_M-curve and / or its derivative, particularly based on the maximum value of the blood pressure determination curve TPW_M-curve and / or its derivative. The processor 3 is adapted to perform this determination of blood pressure, which is non-invasive blood pressure, as described in WO 2018 / 210931 A1.

[0104] In one embodiment, the processor 3 is configured to determine the TPcl value at the time point t when the blood pressure determination curve TPW_M-curve has a maximum value (TPW_M-curve.max), where, in FIG. 10, the TPcl value at the time point when this maximum value is reached is indicated as “TPcl@TPW_M-curve.max”. The processor 3 is further configured to determine the lower envelope of the tissue pressure TP by applying a filter to the end-diastolic point of the tissue pressure TP. The filter can be, for example, the same as the filter used to determine the blood pressure determination curve TPW_M-curve. The resulting curve is named “TPdia-curve” in FIG. 10. Further, the processor 3 can be configured to determine the upper envelope of the tissue pressure TP by applying a filter to the maximum of the systolic phase of the tissue pressure TP. Additionally, this filter can be, for example, the same as the filter used to generate the blood pressure determination curve TPW_M-curve. This curve is named “TPsys-curve” in FIG. 10.

[0105] Next, the processor 3 can be configured to determine the systolic arterial pressure value as a predetermined percentage (TPcl.s%) of TPcl@TPW_M-curve.max. This predetermined percentage is preferably in the range of 100 to 150%, more preferably in the range of 110 to 150%. In FIG. 10, the non-invasive systolic arterial pressure is named “SAPni”, and the predetermined percentage is named “TPcl.s%(TPcl@TPW_M-curve.max)”. In FIG. 10, the non-invasive systolic arterial pressure SAPni is about 134 mmHg.

[0106] The processor 3 can also be adapted to determine the non-invasive systolic arterial pressure SAPni as a predetermined percentage (TPsys.s%) of the TPsys curve at the time position when the blood pressure determination curve TPW_M-curve has a maximum value. This predetermined percentage is preferably in the range of 100 to 140%.

[0107] The processor 3 can also be adapted to determine the non-invasive mean arterial pressure (MAPni) as the value of the TPsys-curve at the time point t(bx) when the TPcl value, or alternatively the value of the TPdia-curve, or alternatively the blood pressure determination curve TPW_M-curve has a value bx representing a predetermined ratio to its maximum value. The processor 3 can also alternatively determine the non-invasive mean arterial pressure MAPni as a predetermined ratio (TPcl.m%) of TPcl at TPW_M-curve.max, where the predetermined ratio is preferably in the range of 80 to 110%.

[0108] The processor 3 can also be adapted to determine the non-invasive diastolic arterial pressure DAPni as the value of the TPsys-curve at the time point t(cx) when the TPdia-curve value, or alternatively the blood pressure determination curve TPW_M-curve has a value cx representing a predetermined ratio to its maximum value. The processor 3 can also alternatively determine DAPni as a predetermined ratio (TPcl.d%) of TPcl@TPW_M-curve.max, where this predetermined ratio is preferably 60 to 80%.

[0109] As described above, the parameters of the functions used to determine the end determination curve TPW_E-curve and to determine the blood pressure determination curve TPW_M-curve are determined by calibration. The ratio used to determine the blood pressure determination value is also determined by calibration. Therefore, these parameters and ratios are determined in advance during the calibration phase so that the deviation between the invasively measured blood pressure value measured very accurately and the blood pressure value obtained by the device is minimized and the time required for blood pressure measurement is relatively reduced. Preferably, thereby, one or some of the parameters of the function used to determine the blood pressure determination curve TPW_M-curve are regarded as the first set of one or some of the parameters, and on the one hand, a good balance is achieved between high-precision non-invasive blood pressure and, on the other hand, a low TP level at the end of the measurement, and thus a low measurement time. When one or some of the parameters are selected such that the TPW_M-curve having a maximum value relatively early is created, the TP level and the measurement time at the end of the measurement are relatively reduced. However, at this time, the accuracy and position of the finally determined non-invasive blood pressure value also decrease. Therefore, the first set of one or some of the parameters is preferably selected so that a desired balance is achieved between the measurement time and the accuracy of the non-invasive blood pressure value.

[0110] One or some of the parameters of the function used to determine the end determination curve TPW_E-curve are regarded as forming a second set of one or some of the parameters, and preferably, are selected such that the maximum value of the end determination curve TPW_E-curve comes relatively early. In one embodiment, the first set of one or some of the parameters and the second set of one or some of the parameters may be the same so that the end determination curve TPW_E-curve and the blood pressure determination curve TPW_M-curve are also the same.

[0111] The values TPcl.s%, TPsys.s%, TPcl.m%, TPcl.d%, bx, and cx are preferably calibrated, as described in WO 2018 / 210931 A1, by statistical evaluation of a calibration set consisting of pairs of measured values of invasive and non-invasive blood pressure values recorded simultaneously from an appropriate number of humans with different hemodynamic states. The non-invasive blood pressure value is determined by the device 1 as described above, and parameters such as the values TPcl.s%, TPsys.s%, TPcl.m%, TPcl.d% are optimized such that the deviation between the invasive blood pressure value and the non-invasive blood pressure value is minimized.

[0112] The processor 3 can be adapted to estimate the type of blood pressure value based on the other two types of blood pressure values already measured. In particular, one of the blood pressure values MAPni, SAPni, and DAPni can be estimated based on the other blood pressure values. This can be done using the following mathematical formulas with cl=(0.2..0.7), c2=(2..6), c3=(-5..5), c4=(0.8..1.3), c5=(0.25..0.5), c6=(-5..5), c7=(0.6..1.1), c8=(0.15..0.4), and c9=(-5..5). SAPni = cl·MAPni + c2·(MAPni - DAPni) - c3 mmHg (9) MAPni = c4·DAPni + c5·(SAPni - DAPni) - c6 mmHg (10) DAPni = c7·MAPni - c8·(SAPni - MAPni) - c9 mmHg (11) Therefore, it can be done.

[0113] The coefficients and constants of equations (9), (10) and (11) are determined in advance by calibration based on the statistical evaluation of a set of clinical invasive blood pressure data that is as large as possible and further spreads over a sufficiently wide range. Therefore, very accurate invasive blood pressure values SAPi (invasive systolic arterial pressure), MAPi (invasive mean arterial pressure) and DAPi (invasive diastolic arterial pressure) are used, and when these very accurate invasive blood pressure values are given, the coefficients and constants of equations 9, 10 and 11 are changed so that these equations are valid.

[0114] Blood pressure measurement is intended to be used quickly and continuously in a series of measurements to enable effective semi - continuous blood pressure monitoring so that the stress of the individual being monitored, i.e., the subject being monitored, is minimized. This series of high - speed blood pressure measurements can also be regarded as non - invasive high - speed mode cycle (FMC) measurements of blood pressure.

[0115] In one embodiment, the first blood pressure measurement starts a low - speed inflation, i.e., the measurement period, at a predetermined tissue pressure TPlow within the range of 15 - 30 mmHg, since there is no information about the previous diastolic arterial pressure (DAP). Further, during this measurement period, the inflation rate is set to a medium value. This inflation rate can be defined as the rate at which TPcl increases over time, and this inflation rate can be selected, for example, to have a value of 1.9 mmHg / s. This corresponds to the measured value of a "normal" blood pressure value. At the end of the systolic phase, when TPcl reaches Patt, the blood pressure measurement preferably pauses for at least 2 seconds to enable reperfusion of the body part of the subject enclosed by shell 4. This pause time 42 preferably has a length within the range from more than 0% to about 50% of the preceding inflation - contraction period 40 that gives rise to cycle 41. The next blood pressure measurement starts a low - speed inflation, i.e., the measurement period, at a higher TPlow, using the information on the diastolic arterial pressure (DAP) determined in the previous measurement (DAPprev) respectively, as shown in FIG. 11.

[0116] The TPlow value should not exceed 90% of the diastolic arterial pressure in order to ensure that all pulses necessary for blood pressure calculation are recorded. Furthermore, as described above, blood pressure may change during the time interval (t_inter) between the start of contraction and the start of the next slow dilation. Therefore, preferably, a function that models the blood pressure drop depending on this time interval t_inter is applied. In clinical data from high-risk surgeries, it has been observed that the diastolic arterial pressure decreases by more than 28% within one minute. Therefore, TPlow is the following function TPlow = 90%DAPprev - 28%DAPprev·t_inter / 60 seconds (11) and can be calculated by using a linear function such as this. Here, "90%DAPprev" and "28%DAPprev" represent 90% and 28% of the previously measured diastolic arterial pressure DAPprev, respectively.

[0117] TPlow can be determined by using a linear function that depends on the previous time interval between the start of contraction and the start of the next slow dilation, and this linear function has a negative slope such that TPlow decreases over time. The slope of the linear function and the positive constant of the linear function can be determined in advance by calibration. In Equation 12, the positive constant is 90%DAPprev and the negative slope is -28%DAPprev. The positive constant and the negative slope can also have other values. For example, the negative slope can be -30%DAPprev.

[0118] In FIG. 12, according to Equation 12, it can be seen how TPlow adapts depending on t_inter. In particular, Measurements #2a and #2b are found to have different TPlow values, where the time interval t_inter of Measurement #2b is larger than that of Measurement #2a, so the TPlow value of Measurement #2b is smaller than that of Measurement #2a. In FIG. 11, since PP is increasing before Measurement #2a, it can also be seen that the inflation rate of Measurement #3 is increasing. Furthermore, the TPlow of Measurement #3 is large compared to the previous measurement because the diastolic arterial pressure DAP is increasing before Measurement #2a. Note that in FIG. 11, interval 44 is the cycle period of the second Measurement #2a, interval 43 is the inflation - deflation period of the second Measurement #2a, and interval 45 is the rest time of the second Measurement #2a. Furthermore, it should be noted that the third Measurement #3 refers to the second Measurement #2a, and the additional second Measurement #2b is shown only to indicate an alternative to the second Measurement #2a.

[0119] FIG. 12 shows a further example for adapting the TPlow value depending on the time interval t_inter according to Equation 12. In this example, the inflation rate during the measurement period is decreasing at Measurement #3 due to the decrease in PP before Measurement #2a and the low TPlow value due to the decrease in DAP before Measurement #2a, compared to the previous measurement.

[0120] As described above, a filter is used to determine the end determination curve TPW_E-curve, the blood pressure determination curve TPW_M-curve, and the envelope curves TPsys-curve and TPdia-curve. Further, a filter is also used to determine TPcl based on TP. Preferably, a low-pass filter is used as the filter. This low-pass filter can be, for example, a cascaded moving average filter with a variable window length up to 8 seconds, where the window lengths at the start and end of the filtering can be shortened to minimize the filter settling time. For example, the filtering can include averaging the signals of at least three pressure pulse curves of TP twice within a moving window of up to 8 seconds (2×8 second filter). Optionally, signal padding can be applied before and / or after the signal to completely fill the filter window before filtering. For example, padding using the first pressure pulse value before the start and the last pressure pulse value at the end can be applied.

[0121] Due to filter delay, TPcl is extrapolated from previous values and becomes available for the last part of the measured signal.

[0122] The filter is applied, for example, to extract TPcl from TP, form smooth TPW_E-curves and smooth TPW_M-curves without fluctuations due to blood pressure pulsations, and generate envelope functions over the systolic peak of TP (TPsys-curve) and the minimum at the end of diastole (TPdia-curve).

[0123] In the following, embodiments of a method for determining blood pressure are exemplarily described with reference to the flowchart shown in FIG. 13.

[0124] After initializing and starting the device in step 101, TPlow is determined in step 102. In the first measurement, TPlow can have a value of 15 mmHg to 30 mmHg. If blood pressure measurement has already been performed, in order to determine TPlow, for example, the previous systolic arterial pressure value can be used according to formula 12.

[0125] In step 103, the cuff during the pre - measurement period is inflated at a relatively large first inflation rate until it reaches TPlow. Then, in step 104, the measurement period, i.e., the slow inflation period, starts, and during this measurement period, the blood pressure determination curve TPW_M - curve and the end determination curve TPW_E - curve are determined. Further, these curves are used to determine the end measurement time point, and when this end measurement time point is reached or passed, the slow inflation period is stopped, and in step 105, the cuff is deflated. After contraction and rest to enable venous return in step 106, the method continues with step 102. Therefore, this method can be implemented in a loop for continuously monitoring blood pressure over time in several measurement cycles. While steps 102 - 105 are being executed, the processor calculates the blood pressure value in parallel. The loop can be executed until an abort criterion is met. For example, when a physician inputs a command corresponding to the device via an input unit such as a keyboard, computer mouse, touch pad, etc., the blood pressure monitoring is interrupted.

[0126] This device preferably enables non-invasive FMC measurement of blood pressure based on non-invasive high-fidelity tissue pressure TP recordings, preferably using a kink prevention shell system, as described in WO 2014 / 121945 A1. This device preferably enables a statistical average maximum pressure inflation of about 85% or less of the systolic arterial pressure. A single blood pressure measurement using this device 1 takes about 20 to 60 seconds depending on the height of the arterial blood pressure and pulse pressure, and the reciprocal of the heart rate. This device is preferably configured to provide non-invasive systolic arterial pressure SAPni, non-invasive mean arterial pressure MAPni, and non-invasive diastolic arterial pressure DAPni. The measurements are preferably performed with short pauses during which the cuff is not pressurized between consecutive measurements to allow venous return. These short pauses are preferably in the range of 5 to 10 seconds. Since the clamp pressure preferably always remains below the SAP, arterial perfusion of the site wrapped by a shell such as the upper arm or wrist of the subject is preferably not completely interrupted during the measurement. Thus, compared to conventional oscillometric measurements, the measurement is less stressful for the subject.

[0127] For example, the device 1 described above with reference to FIG. 1 provides a reliable method for quickly determining blood pressure using a clamp pressure that does not exceed the SAP. Due to the relatively short measurement time and relatively low maximum cuff pressure, this blood pressure measurement is very convenient for people and can reduce the likelihood of predicted complications such as thrombophlebitis, pain, petechial hemorrhage, limb edema, peripheral neuropathy, etc.

[0128] In one embodiment, TPlow can be at or above the DAP. TPlow defines the tissue pressure at the start of the measurement period, i.e., at the start of the low-speed inflation period, and the low-speed inflation can end when a specific end criterion is reached. This end criterion has been described above.

[0129] In the above-described embodiments, the features are determined by using the TPac pulse, but these features can also be determined by directly using the measured pressure pulse, i.e., the TP pulse. It is also possible to process the TP pulse in another way, i.e., without subtracting the average TP value for determining the TPac pulse. For example, for each measured pressure pulse, the pressure values at t.start and t.stop are connected by a straight line, and this straight line can be drawn from each measured pressure pulse to determine the feature-determining pulse.

[0130] In the above-described embodiments, the TPW_M-curve and the TPW_E-curve are determined, but it is also possible that the TPW_M-curve is determined while the TPW_E-curve is not determined, where the TPW_M-curve is used to determine blood pressure.

[0131] In the above-described embodiment, the processor 3 is configured to form a blood pressure determination curve TPW_M-curve based on a blood pressure determination value TPWP_M that depends only on a feature that is the difference TPP between the maximum systolic pressure TPsys of the feature determination pulse and the pressure of the feature determination pulse at the end-diastolic point TPdia. However, in another embodiment, the blood pressure determination curve TPW_M-curve can be formed based on a blood pressure determination value TPWP_M that depends only on another feature. For example, the blood pressure determination curve TPW_M-curve depends only on the area TPA or TPA.norm of each feature determination pulse, or depends only on the area TPA+.top surrounded by the first upper part of the feature determination pulse, particularly the area TPA+.top50, or depends only on the area TPA.top surrounded by the second upper part of the feature determination pulse. Here, a) the upper end of the second upper part is at the maximum systolic pressure TPsys of the feature determination pulse, and b) the lower end of the second upper part is between the pressure value corresponding to the average TPcl of the measured pressure TP and the pressure TPdia of the feature determination pulse at the end-diastolic point. Thus, in one embodiment, the function used to determine the blood pressure determination value TPWP_M depends on the area TPA or TPA.norm of each feature determination pulse, or depends on the area TPA+.top surrounded by the first upper part of the feature determination pulse, particularly TPA+.top50, or depends on the area TPA.top surrounded by the second upper part of the feature determination pulse, but does not depend on any other arbitrary feature of the pressure pulse. For example, the blood pressure determination value TPWP_M is given by the following mathematical formula TPWP_M = d5·TPA exp16 (13) TPWP_M = d6·TPA+.top exp17 (14) TPWP_M = d7·TPA.top exp18 (15) determined according to one of them, where d5, d6, d7, exp16, exp17, and exp18 are predetermined constants. For example, they can be determined in advance by calibration. In one embodiment, d5 = 1, d6 = 1, d7 = 1, where the exponents are determined when calibrating the device.

[0132] In a more preferred embodiment, the processor 3 is configured to form a blood pressure determination curve TPW_M-curve based on a blood pressure determination value TPWP_M that depends only on a) a feature that is the difference TPP between the maximum systolic pressure TPsys of the feature determination pulse and the pressure TPdia of the feature determination pulse at the end of diastole, and b) an area (TPA.top) enclosed by the second upper part of the feature determination pulse, or an area (TPA / TPA.norm) of each feature determination pulse. Thus, in one embodiment, the function used to determine the blood pressure determination value TPWP_M depends on a) TPP and b) TPA.top or TPA or TPA.norm, but does not depend on further features of the pressure pulse. In particular, the blood pressure determination value TPWP_M is given by the following equations TPWP_M = d8 · TPA.top exp19 · TPP exp20 (16) TPWP_M = d9 · TPA exp21 · TPP exp22 (17) TPWP_M = d10 · TPA.norm exp18 · TPP exp24 (18) It can be determined according to one of them, where d8, d9, d10, exp19, exp20, exp21, exp22, exp23, and exp24 are predetermined constants. For example, they can be determined in advance by calibration. In one embodiment, d8 = 1, d9 = 1, d10 = 1, where the exponents are determined when calibrating the device. The mathematical formula described above for TPWP_M can also be used for TPWP_E correspondingly. The structure of the mathematical formula is the same, and only other constants determined by calibration are used.

[0133] Other variations to the disclosed embodiments can be understood and implemented by those skilled in the art when practicing the claimed invention, upon examination of the drawings, the disclosure, and the appended claims.

[0134] In the claims, the term "comprising" does not exclude other elements or steps, and does not exclude the possibility that there may be a plurality even if it does not state that there are a plurality.

[0135] A single unit or device may perform the functions of several items recited in the claims. The mere fact that certain means are recited in mutually different dependent claims does not indicate that a combination of these means cannot be used advantageously.

[0136] The determination of the end measurement time point, the characteristics of the pulse, the calculation of specific curves and blood pressure values, etc., performed by one or several units or devices can be performed by any other number of units or devices. The calculations and determinations according to the method, and / or the control of the device can be implemented as computer program code means and / or as dedicated hardware.

[0137] The computer program may be stored / distributed on a suitable medium, such as an optical storage medium or a solid-state medium, supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunications systems.

[0138] Any reference signs in the claims shall not be construed as limiting its scope. In particular, letters such as TPP and TPA used within parentheses in the claims shall not be construed as limiting its scope. For example, other features than those represented by the reference signs can also be used in accordance with the claims.

[0139] The present invention relates to determining a blood pressure of a subject based on a pressure signal measured by using a measuring device including a) a shell surrounding a site through which the subject's blood flows, b) a pressurizing unit applying pressure to the shell, thereby applying pressure to the surrounded site of the subject, and c) a pressure sensor measuring a pressure signal on the skin of the surrounded site of the subject. For several pressure pulses of the pressure signal, respective features characterizing each pressure pulse are determined, where based on each feature, a respective blood pressure determination value is determined, thereby forming a blood pressure determination curve used for determining the blood pressure. This enables the determination of the blood pressure with a relatively low computational effort.

Claims

1. A device for measuring the blood pressure of a subject, wherein the device is A pressure signal supply unit configured to supply a measured pressure signal of a subject over a period of time, wherein the pressure signal is a) A shell configured to enclose the area through which the subject's blood flows, b) A pressurizing unit configured to apply pressure to the shell, thereby applying pressure to the wrapped portion of the subject, and c) A pressure sensor configured to measure pressure signals on the skin of the wrapped area of ​​the subject. A pressure signal supply unit is provided, which is measured by using a measuring device having a pressure unit that increases or decreases the applied pressure while the pressure signal is being measured, and the measured pressure signal indicates the pulsation of blood and has multiple pressure pulses. A processor is configured to determine, for each of the plurality of pressure pulses, at least one feature characterizing each pressure pulse, and to determine a blood pressure determination value for each of the pressure pulses based on the determined at least one feature, such that a number of blood pressure determination values ​​are determined for several pressure pulses that exist at different times, and the number of blood pressure determination values ​​determined for several of the pressure pulses and therefore for several of the times form a blood pressure determination curve, and to determine blood pressure based on the blood pressure determination curve. It has, The processor is configured to supply a feature determination pulse based on each pressure pulse in order to determine the at least one feature for each pressure pulse. The processor determines the blood pressure determination value, and therefore has the following features: Only one feature from the aforementioned feature determination pulses, a) A feature which is the difference between the maximum systolic pressure of the feature determination pulse and the pressure of the feature determination pulse at the end of expansion, and b) A feature which is an area enclosed by the upper part of the first feature determination pulse or an area enclosed by the upper part of the second feature determination pulse, wherein i) the upper end of the first upper part is at the maximum systolic pressure of the feature determination pulse, ii) the lower end of the first upper part is between the maximum systolic pressure of the feature determination pulse and a pressure value corresponding to the average of the measured pressures, and i) the upper end of the second upper part is at the maximum systolic pressure of the feature determination pulse, ii) the lower end of the second upper part is between the pressure value corresponding to the average of the measured pressures and the pressure of the feature determination pulse at the end of expansion. One or more features comprising an area enclosed by the first upper part of the feature determination pulse, wherein the lower end of the first upper part is at a pressure corresponding to half the pressure distance between the maximum systolic pressure of the feature determination pulse and the pressure value corresponding to the average of the measured pressures. A device configured to form the blood pressure determination value based on at least one of the following.

2. The aforementioned processor has the following characteristics for each pressure pulse: The difference between the maximum systolic pressure of the feature determination pulse and the pressure of the feature determination pulse at the end of diastole, The area enclosed by the first upper part of the feature determination pulse, wherein a) the upper end of the first upper part is at the maximum systolic pressure of the feature determination pulse, and b) the lower end of the first upper part is between the maximum systolic pressure of the feature determination pulse and the pressure value corresponding to the average of the measured pressures. The duration of each of the aforementioned feature determination pulses, The area of ​​each of the aforementioned feature determination pulses, The full width at half maximum of each of the aforementioned feature determination pulses, and The area enclosed by the second upper part of the feature determination pulse, wherein a) the upper end of the second upper part is at the maximum systolic pressure of the feature determination pulse, and b) the lower end of the second upper part is between the pressure value corresponding to the average of the measured pressures and the pressure of the feature determination pulse at the end of expansion. The apparatus according to claim 1, configured to determine at least one of the features.

3. The processor determines the blood pressure determination value, and therefore has the following characteristics: The difference between the maximum systolic pressure of the feature determination pulse and the pressure of the feature determination pulse at the end of diastole, The area of ​​each of the aforementioned feature determination pulses, The area enclosed by the first upper part of the feature determination pulse, and Area enclosed by the second upper part of the feature determination pulse The apparatus according to claim 1 or 2, configured to form the blood pressure determination curve based on only one of the following.

4. The apparatus according to claim 1 or 2, wherein the processor is configured to determine the position of the maximum value of the blood pressure determination curve and to determine blood pressure based on the determined position and the measured pressure.

5. The apparatus according to claim 4, wherein the processor is configured to determine blood pressure based on the average of the measured pressures at the location of the determined maximum value.

6. The apparatus according to claim 1, wherein the processor is configured to control the measuring device such that the applied pressure increases during a measurement period extending to a termination measurement point, and decreases during a subsequent post-blood pressure measurement period, the pressure sensor measures the pressure on the skin for at least the duration of the measurement period, and the processor is configured to determine a termination measurement point based on at least one characteristic determined for at least some of the plurality of pressure pulses, the measurement period is stopped at or after the termination measurement point, and the pressurizing unit is configured to control the pressurizing unit to decrease the applied pressure in order to start a subsequent post-blood pressure measurement period when the termination measurement time is reached or after it is reached.

7. The aforementioned processor, To determine several termination decision values ​​for several pressure pulses existing at different times, based on at least one feature determined for each of the pressure pulses, the termination decision values ​​for each of the pressure pulses, which are determined for several of the pressure pulses and therefore for several of the time periods, form a termination decision curve, and Termination measurement point based on the aforementioned termination decision curve The apparatus according to claim 6, configured to determine the following.

8. The aforementioned processor is subject to the following conditions: The maximum value of the termination decision curve occurs before the maximum value of the blood pressure decision curve in terms of time. The maximum value of the termination decision curve occurs at or after the maximum value of the blood pressure decision curve, and the decrease after the maximum value of the termination decision curve is steeper than the decrease after the maximum value of the blood pressure decision curve, and The end-determination curve coincides with the blood pressure determination curve. The apparatus according to claim 7, configured to determine the termination decision curve such that one of the following conditions is met.

9. The apparatus according to claim 7 or 8, wherein the processor is configured to determine the end measurement time based further on the blood pressure determination curve.

10. The aforementioned processor, a) When the termination decision curve passes the maximum value of the termination decision curve and then decreases to a value less than or equal to a predetermined percentage of the maximum value, and b) When the blood pressure determination curve reaches or passes the maximum value of the blood pressure determination curve. The apparatus according to claim 9, configured to determine the end measurement time by determining the end measurement time.

11. A method for measuring the blood pressure of a subject, wherein the method is A pressure signal supply unit supplies a measured pressure signal of a subject over a period of time, wherein the pressure signal is: a) A shell configured to enclose the area through which the subject's blood flows, b) A pressurizing unit configured to apply pressure to the shell, thereby applying pressure to the wrapped portion of the subject, and c) A pressure sensor configured to measure pressure signals on the skin of the wrapped area of ​​the subject. The measurement is performed using a measuring device having a pressurizing section which increases or decreases the applied pressure while the pressure signal is being measured, and the measured pressure signal indicates the pulsation of blood and has multiple pressure pulses, in steps, The processor determines, for each of the plurality of pressure pulses, at least one feature that characterizes each of the pressure pulses, A step of determining a blood pressure determination value for each of several pressure pulses present at different times, by the processor, based on at least one determined feature, wherein the several blood pressure determination values ​​determined for several pressure pulses and therefore for several times form a blood pressure determination curve. The processor performs the steps of determining blood pressure based on the blood pressure determination curve and Includes, The processor supplies a feature determination pulse based on each pressure pulse in order to determine the at least one feature for each pressure pulse. The processor determines the blood pressure determination value, and therefore has the following features: Only one feature from the aforementioned feature determination pulses, a) A feature which is the difference between the maximum systolic pressure of the feature determination pulse and the pressure of the feature determination pulse at the end of expansion, and b) A feature which is an area enclosed by the upper part of the first feature determination pulse or an area enclosed by the upper part of the second feature determination pulse, wherein i) the upper end of the first upper part is at the maximum systolic pressure of the feature determination pulse, ii) the lower end of the first upper part is between the maximum systolic pressure of the feature determination pulse and a pressure value corresponding to the average of the measured pressures, and i) the upper end of the second upper part is at the maximum systolic pressure of the feature determination pulse, ii) the lower end of the second upper part is between the pressure value corresponding to the average of the measured pressures and the pressure of the feature determination pulse at the end of expansion. One or more features comprising an area enclosed by the first upper part of the feature determination pulse, wherein the lower end of the first upper part is at a pressure corresponding to half the pressure distance between the maximum systolic pressure of the feature determination pulse and the pressure value corresponding to the average of the measured pressures. A method for forming the blood pressure determination value based on the above.

12. A computer program for determining blood pressure, comprising program code for causing a device for determining blood pressure according to claim 1 or 2 to perform the steps described in claim 11.

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