Arteriovenous pressure measuring device

Abstract

An arteriovenous pressure measurement device (10) is provided with a pressure detection unit (34), a capacity detection unit (42), and a calculation unit (441). The pressure detection unit (34) detects the internal pressure of the compression belt (20). The volume detection unit (42) detects the volume of the fluid present inside the compression belt (20). The calculation unit (441) calculates the blood pressure of the subject on the basis of the internal pressure of the compression band (20) detected by the pressure detection unit (34) when the fluid is discharged from the inside of the compression band (20), and the fluid volume of the compression band (20) detected by the volume detection unit (42).

Description

Related references

[0001] This application is based on and claims priority to Japanese Patent Application No. 2023-027217, filed on February 24, 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This invention relates to an arteriovenous pressure measuring device. Background Technology

[0003] To monitor conditions such as excessive or insufficient circulating blood volume, impaired cardiac function, shock, and dehydration, arterial and venous punctures, catheters, etc., are sometimes used to measure arterial and venous pressure. In the measuring device described in Patent Document 1 below, the central venous pressure of the subject is measured by inserting a catheter into the subject's blood vessel. Existing technical documents Patent documents

[0004] Patent Document 1: Japanese Patent Application Publication No. 2015-173952 Summary of the Invention

[0005] To simultaneously collect arterial and venous pressure information, invasive measurement methods are required, such as inserting a catheter into the subject's blood vessel using the measuring device described in Patent Document 1. However, this measurement requires specialized equipment, making it practically unsuitable for small-scale hospitals. Furthermore, because this measurement is invasive, there are still risks of serious complications such as vascular injury, embolism, and infection, and it also places a heavy burden on the patient.

[0006] The purpose of this invention is to provide an arteriovenous pressure measuring device that can measure blood pressure in a more convenient and safer way.

[0007] An embodiment of the present invention provides an arteriovenous pressure measuring device comprising: a fluid inflow section, a fluid outflow section, a pressure detection section, a volume detection section, and a calculation section. The fluid inflow section increases the pressure inside a compression band worn by a subject by allowing fluid to flow into the band. The fluid outflow section decreases the pressure inside the compression band by discharging fluid from the band. The pressure detection section detects the internal pressure of the compression band. The volume detection section detects the volume of fluid present inside the compression band. The calculation section calculates the subject's blood pressure based on the internal pressure of the compression band detected by the pressure detection section when fluid is discharged from the band, and the fluid volume of the compression band detected by the volume detection section.

[0008] Based on this configuration, it is possible to measure the blood pressure of a subject without inserting a catheter or other means into the subject, that is, to measure the blood pressure of a subject non-invasively. Therefore, it is possible to use a more convenient and safer method to measure blood pressure. Attached Figure Description

[0009] Figure 1 This is a schematic block diagram of the general structure of the arteriovenous pressure measuring device provided in the first embodiment. Figure 2 This is a schematic diagram illustrating the change in internal air volume relative to the internal pressure of the compression belt as air is expelled from it. Figure 3 This is a schematic diagram illustrating the change in internal air volume relative to the internal pressure of the compression belt as air is expelled from it. Figure 4 This is a schematic diagram illustrating the change of the first derivative value of air as it is expelled from the compression belt relative to the internal pressure of the compression belt. Figure 5 This is a schematic flowchart illustrating the steps of the processing performed by the control device provided in the first embodiment. Figure 6 This is a schematic diagram comparing the blood pressure measurement value obtained by the arteriovenous pressure measuring device provided in the first embodiment with the blood pressure measurement value of a reference example. Figure 7 This is a schematic diagram showing the relationship between the internal pressure of the compression belt and its second-order differential value when air is discharged from the compression belt. Figure 8 This is a schematic flowchart illustrating the steps of the processing performed by the control device provided in the second embodiment. Figure 9 This is a schematic diagram illustrating the change in internal air volume relative to the internal pressure of the compression belt as air is expelled from it. Figure 10 This is a schematic diagram comparing the change of the internal pressure of the compression belt with time as air is discharged from the compression belt, and the change of the second derivative value of the pressure belt with time as air is discharged from the compression belt. Figure 11 This is a schematic diagram comparing the change of the first derivative value of air as it is discharged from the compression zone with respect to time, and the change of the second derivative value of air as it is discharged from the compression zone with respect to time. Detailed Implementation

[0010] Hereinafter, embodiments of the arteriovenous pressure measuring device will be described with reference to the accompanying drawings. To make the description easier to understand, the same reference numerals will be used for the same components in each drawing as much as possible to avoid repetitive descriptions.

[0011] <First Implementation Method> (Composition of an arteriovenous pressure measuring device) First, the first embodiment of the arteriovenous pressure measuring device will be described. Figure 1 The arteriovenous pressure measuring device 10 shown can non-invasively measure the peripheral venous pressure of a subject. For example... Figure 1 As shown, the arteriovenous pressure measuring device 10 includes: a compression band 20, an air pump 30, a switching valve 31, a flow sensor 32, a proportional valve 33, and a pressure sensor 34.

[0012] The compression band 20 is a bag-shaped component wrapped around a part of a living organism, specifically a part of the human body. The compression band 20 is also referred to as a "cuff." Air can be supplied to the interior of the compression band 20, and when the air supply increases the internal pressure, the compression band 20 compresses the upper arm 50. When the air is expelled from the interior of the compression band 20, the pressure on the upper arm 50 is released.

[0013] Air pump 30 is connected to compression belt 20 via piping 35. Air pump 30 supplies air to compression belt 20 via piping 35. The air supplied to compression belt 20 by air pump 30 is supplied into the interior of compression belt 20, thereby increasing the internal pressure of compression belt 20. Thus, in this embodiment, air is equivalent to fluid supplied into the interior of compression belt 20. Furthermore, air pump 30 is equivalent to a fluid inlet, causing the pressure inside compression belt 20 to increase by allowing air to flow into the interior of compression belt 20.

[0014] Along the piping 35, starting from the side of the air pump 30, a switching valve 31, a flow sensor 32, and a proportional valve 33 are sequentially installed.

[0015] The switching valve 31 selectively switches between a supply state (connected to the air pump 30 via the piping 35) and a discharge state (connected to the discharge pipe 36 via the piping 35). When the switching valve 31 is in the supply state, air is supplied from the air pump 30 to the compression belt 20 through the piping 35. When the switching valve 31 is in the discharge state, air inside the compression belt 20 is discharged to the outside through the piping 35 and the discharge pipe 36. Thus, in this embodiment, the switching valve 31 acts as a fluid discharge section, thereby reducing the pressure inside the compression belt 20 by allowing air to be discharged from its interior.

[0016] Flow sensor 32 detects the flow rate of air flowing through piping 35 and outputs a signal corresponding to the detected air flow rate. When air is supplied from air pump 30 to compression belt 20 through piping 35, flow sensor 32 detects the flow rate of air supplied to the inside of compression belt 20, i.e., detects the air supply amount. When air is discharged from compression belt 20 to the outside through piping 35 and discharge pipe 36, flow sensor 32 detects the flow rate of air discharged from the inside of compression belt 20, i.e., detects the air discharge amount. In this embodiment, flow sensor 32 is equivalent to a flow detection unit.

[0017] When air is supplied from the air pump 30 to the inside of the compression belt 20 through the piping 35, the proportional valve 33 adjusts the flow rate of the air supplied to the compression belt 20. When air is discharged from the inside of the compression belt 20 through the piping 35 and the discharge pipe 36, the proportional valve 33 adjusts the flow rate of the air discharged from the compression belt 20.

[0018] A pressure sensor 34 is located on a branch pipe 37, which branches off from the middle of the proportional valve 33 and the compression belt 20 on the piping 35. The pressure sensor 34 detects the air pressure within the piping 35 at the middle section between the proportional valve 33 and the compression belt 20, i.e., it detects the internal pressure of the compression belt 20. Thus, in this embodiment, the pressure sensor 34 functions as a pressure detection unit, detecting the internal pressure of the compression belt 20.

[0019] like Figure 1 As shown, the arteriovenous pressure measuring device 10 also includes: an analog-to-digital converter 40, 41, an accumulator 42, a filter circuit 43, a control device 44, and a display device 45.

[0020] The analog-to-digital converter 40 receives the output signal from the flow sensor 32. The converter 40 converts the output signal from the flow sensor 32 from an analog signal to a digital value at predetermined intervals. The converted digital value represents the airflow detected by the flow sensor 32, that is, the value of the airflow through the piping 35. The converter 40 outputs the converted digital value of the airflow to the accumulator 42. Hereinafter, the digital value of the airflow Q converted by the converter 40 is also referred to as the "detected value of the airflow Q of the piping 35".

[0021] Analog-to-digital converter 41 receives the output signal from pressure sensor 34. Analog-to-digital converter 41 converts the output signal from pressure sensor 34 from an analog signal to a digital value at predetermined intervals. The converted digital value represents the air pressure detected by pressure sensor 34, that is, the value representing the internal pressure of the compression belt 20. Analog-to-digital converter 41 outputs the converted digital value of the internal pressure of the compression belt 20 to filter circuit 43. Hereinafter, the digital value of the internal pressure of the compression belt 20 converted by analog-to-digital converter 40 is also referred to as the "detected value of the internal pressure P of the compression belt 20".

[0022] The accumulator 42 calculates the air volume, or air capacity VA, within the compression belt 20 by accumulating the detected air flow rate Q of the piping 35 sequentially output from the analog-to-digital converter 40. For example, from the point when the air pump 30 begins supplying air to the compression belt 20 until the point when air supply to the compression belt 20 stops, the accumulator 42 calculates the air capacity VA of the compression belt 20 by accumulating the detected air flow rate Q of the piping 35 sequentially output from the analog-to-digital converter 40. For example, the point when the switching valve 31 is switched to the supply state and the air pump 30 is activated can be considered the point when air supply to the compression belt 20 begins. Similarly, the point when the air pump 30 stops operating can be considered the point when air supply to the compression belt 20 stops. The accumulator 42 maintains the air capacity VA of the compression belt 20 at the point when air supply to the compression belt 20 stops at the maximum air capacity Vmax.

[0023] On the other hand, the accumulator 42 accumulates the detected air flow rate Q of the piping 35, which is sequentially output from the analog-to-digital converter 40 starting from the point when air begins to be discharged from the compression belt 20, and subtracts the accumulated value from the maximum air capacity Vmax to calculate the estimated value of the current air capacity VA of the compression belt 20. The point at which the switching valve 31 is switched to the discharge state can be taken as the point at which air begins to be discharged from the compression belt 20.

[0024] In this way, the accumulator 42 provided in this embodiment can calculate not only the air volume VA inside the compression belt 20 when air is supplied to it, but also the air volume VA inside the compression belt 20 when air is discharged from it. The accumulator 42 outputs the calculated current air volume VA of the compression belt 20 to the control device 44. Thus, in this embodiment, the accumulator 42 is equivalent to a volume detection unit, detecting the air volume present inside the compression belt 20.

[0025] The filter circuit 43 smooths the detected value of the internal pressure P of the compression belt 20, which is sequentially output from the analog-to-digital converter 41, and outputs the smoothed detected value of the internal pressure P to the control device 44.

[0026] The control device 44 is centered around a microcomputer having a central processing unit (CPU), storage devices, etc. As a functional structure that is realized by executing programs stored in the storage devices, the control device 44 includes a pressure adjustment unit 440, a calculation unit 441, and a display unit 442.

[0027] The pressure regulating unit 440 controls the operation of the air pump 30, switching valve 31, and proportional valve 33 to change the internal pressure of the compression belt 20. For example, after the switching valve 31 is switched to the supply state, the pressure regulating unit 440 operates the air pump 30, thereby increasing the internal pressure of the compression belt 20 to a predetermined pressure. At this time, the pressure regulating unit 440 controls the proportional valve 33 to adjust the flow rate of air supplied to the compression belt 20. For example, the pressure regulating unit 440 controls the proportional valve 33 to supply a certain flow rate of air to the compression belt 20 per unit time. Afterward, after the air pump 30 is stopped, the pressure regulating unit 440 switches the switching valve 31 to the discharge state, thereby decreasing the internal pressure of the compression belt 20. At this time, the pressure regulating unit 440 controls the proportional valve 33 to adjust the flow rate of air discharged from the compression belt 20. For example, the pressure regulating unit 440 controls the proportional valve 33 to discharge a certain flow rate of air from the compression belt 20 per unit time.

[0028] The calculation unit 441 monitors the air volume VA of the compression band 20 calculated by the accumulator 42 and the internal pressure of the compression band 20 calculated by the filter circuit 43, starting from the time when air begins to be discharged from the compression band 20, specifically from the time when the switching valve 31 switches from the supply state to the discharge state. The calculation unit 441 calculates a first-order derivative value, which is the value obtained by differentiating the air volume VA of the compression band 20 with respect to the internal pressure of the compression band 20. Based on this first-order derivative value, the calculation unit 441 determines whether the blood vessel of the upper arm 50 compressed by the compression band 20 changes from a flattened state to a diastolic state. When the calculation unit 441 detects that the blood vessel of the upper arm 50 compressed by the compression band 20 changes from a flattened state to a diastolic state, the calculation unit 441 uses the internal pressure of the compression band 20 calculated by the filter circuit 43 at this time point as the venous pressure of the subject.

[0029] The display unit 442 displays information such as the venous pressure of the subject calculated by the calculation unit 441 on the display device 45. The display device 45 is a liquid crystal display, an organic EL display, or the like.

[0030] (Principles of blood pressure calculation) Next, the principle of blood pressure calculation by the calculation unit 441 will be explained.

[0031] By supplying air to the compression band 20, the internal pressure of the compression band 20 is increased. When the internal pressure of the compression band 20 is higher than the subject's blood pressure, the blood vessels become flattened by the compression band 20. Subsequently, when air is discharged from the compression band 20, for example, the changes in the internal pressure P and internal volume V of the compression band 20 are as follows... Figure 2 As shown.

[0032] like Figure 2 As indicated by the middle arrow, when air is expelled from the compression band 20, the internal pressure P and internal volume V of the compression band 20 gradually decrease. Then, when the internal pressure P of the compression band 20 is lower than the blood pressure, as... Figure 2 As shown, blood vessel B changes from a flattened state to a dilated state. During dilation, the volume of blood vessel B increases, thus generating an outward compressive force on the compression band 20, which further significantly reduces the internal volume V of the compression band 20. For example, as... Figure 2 As shown, when the internal pressure P of the compression band 20 decreases to "P10" and blood vessel B changes from a flattened state to a dilated state, the relationship between the internal pressure P and the internal volume V of the compression band 20 changes as follows: Figure 2 As shown by the solid line. The change in internal volume V relative to the internal pressure P of the compression band 20, as shown by the solid line, is greater than the change in internal volume V relative to internal pressure P, as shown by the dashed line in the figure. The dashed line represents the extrapolated relationship between the internal pressure P and internal volume V of the compression band 20 when blood vessel B is in a flattened state, i.e., when the internal pressure P of the compression band 20 is greater than "P10".

[0033] Figure 3 Enlarged display Figure 2 The double-dotted section in the diagram. When air is expelled from the compression band 20, the internal volume V of the compression band 20 decreases, and simultaneously, the internal pressure P of the compression band 20 also decreases. Then, when the internal pressure P of the compression band 20 decreases to "P10" and the blood vessels begin to dilate, the compression band 20 is compressed by the blood vessels, causing the internal volume V of the compression band 20 to decrease further significantly. On the other hand, the internal pressure P of the compression band 20 only rises momentarily. Therefore, as... Figure 3 As shown, the internal pressure P of the compression band 20 increases instantaneously from "P10" to "P11" and then decreases again. Therefore, if the change in the internal pressure P of the compression band 20 can be detected, it is possible to accurately detect whether the blood vessel has changed from a flattened state to a dilated state. However, when measuring the venous pressure of a subject, the change in the internal pressure P of the compression band 20 is very small, making it difficult to detect.

[0034] On the other hand, if the change in internal volume V is used relative to the change in internal pressure P of the compression band 20, i.e., the first derivative of internal volume V with respect to internal pressure P, dV / dP, the change in internal pressure P of the compression band 20 can be highlighted. Therefore, it is possible to more accurately detect whether the blood vessel has changed from a flattened state to a diastolic state. However, directly detecting the internal volume V of the compression band 20 is difficult. Therefore, in the arteriovenous pressure measuring device 10 provided in this embodiment, the change in air volume VA of the compression band 20 is used instead of the change in internal volume V of the compression band 20 to determine whether the blood vessel has changed from a flattened state to a diastolic state. The reason why the change in air volume VA of the compression band 20 can be used instead of the change in internal volume V of the compression band 20 is as follows.

[0035] First, the internal pressure P, internal volume V, and air mass m inside the compression belt 20 are related by the following equation f1. It should be noted that in equation f1, "R" is the gas constant, and "T" is the temperature inside the compression belt 20.

[0036] P×V=m×R×T(f1).

[0037] Differentiating both sides of equation f1 with the internal pressure P yields equation f2.

[0038] dV / dP=R×T×{(dm / dP) / Pm / P 2}(f2).

[0039] When the internal pressure P is assumed to be sufficiently small, the first differential value dV / dP can be approximated by the following equation f3.

[0040] dV / dP≒(R×T / P)(dm / dP)(f3).

[0041] As shown in equation f3, the change in internal volume V relative to the change in internal pressure P can be calculated as the change in air mass m inside the compression belt 20 relative to the change in internal pressure P. The air mass m inside the compression belt 20 is related to the air capacity VA of the compression belt 20. Therefore, the change in internal volume V relative to the change in internal pressure P can be calculated as the change in air capacity VA of the compression belt 20 relative to the change in internal pressure P.

[0042] Figure 4 Based on the first-order derivative dVA / dP of the air volume VA discharged from the compression belt 20 relative to the internal pressure P of the compression belt 20, a graph showing their relationship is plotted with this first-order derivative dVA / dP as the vertical axis and the internal pressure P as the horizontal axis. For example... Figure 4As shown, when the internal pressure P represents "P11", that is, when the blood vessel changes from a flattened state to a diastolic state, the first derivative dVA / dP represents the maximum value. Therefore, if the first derivative dVA / dP is used to represent the internal pressure P at its maximum value, the blood pressure of the subject can be detected.

[0043] (The process executed by the control device) Next, refer to Figure 5 The specific steps of the venous pressure measurement process performed by the control device 44 using the above principle will be explained. It should be noted that the control device 44 repeatedly performs this process at a predetermined cycle. Figure 5 The processing shown.

[0044] like Figure 5 As shown, the calculation unit 441 of the control device 44 first determines whether air has started to be discharged from the compression belt 20 (step S10). For example, when the switching valve 31 is in the supply state, the calculation unit 441 determines that air has not yet started to be discharged from the compression belt 20 (step S10: no), and temporarily stops the operation. Figure 5 The processing shown.

[0045] When the switching valve 31 switches to the discharge state, the calculation unit 441 determines that air has started to be discharged from the compression belt 20 (step S10: Yes). At this time, the calculation unit 441 obtains information about the current air capacity VA of the compression belt 20 from the accumulator 42 (step S11) and obtains information about the current internal pressure P of the compression belt 20 from the filter circuit 43 (step S12). Then, the calculation unit 441 calculates the first derivative value dVA / dP (step S13) and determines whether the calculated first derivative value dVA / dP represents a maximum value (step S14). If the first derivative value dVA / dP does not represent a maximum value (step S14: No), the calculation unit 441 returns to the processing in step S11, continues to obtain the air capacity VA and internal pressure P of the compression belt 20, and continues to calculate the first derivative value dVA / dP.

[0046] When the first-order derivative dVA / dP represents a maximum value (step S14: Yes), the calculation unit 441 detects the subject's blood pressure based on the internal pressure P at this time (step S15). Then, the display unit 442 displays the subject's blood pressure detected by the calculation unit 441 on the display device 45 (step S16).

[0047] (Functions and Effects) As described above, the arteriovenous pressure measuring device 10 provided in this embodiment includes: an air pump 30, a switching valve 31, a pressure sensor 34, an accumulator 42, and a calculation unit 441. The air pump 30 increases the pressure inside the compression band 20 by allowing air to flow into it. The switching valve 31 decreases the pressure inside the compression band 20 by discharging air from it. The pressure sensor 34 detects the internal pressure of the compression band 20. The accumulator 42 detects the air volume VA present inside the compression band 20. The calculation unit 441 calculates the subject's blood pressure based on the internal pressure P of the compression band 20 detected by the pressure sensor 34 when air is discharging from it, and the air volume VA of the compression band 20 detected by the accumulator 42.

[0048] Based on this configuration, it is possible to measure a subject's blood pressure without inserting a catheter or similar device, i.e., non-invasive blood pressure measurement. Furthermore, by using the above method to measure blood pressure, it is possible to measure venous pressure, which is lower than arterial pressure, thus enabling a more convenient and safer method for measuring venous pressure.

[0049] Furthermore, the blood pressure measurement of a subject using the arteriovenous pressure measuring device 10 provided in this embodiment can achieve approximately the same accuracy as when a catheter is inserted into the subject and the pressure of the venous blood vessels is directly measured using a pressure sensor. Figure 6 The relationship between the measured venous pressure of a subject detected by the arteriovenous pressure measuring device 10 provided in this embodiment and the measured venous pressure when measured directly using a catheter is shown. Figure 6 In this embodiment, the measured value of the venous pressure of the subject detected by the arteriovenous pressure measuring device 10 is recorded as "measurement value y of this embodiment" on the vertical axis, and the measured value when venous pressure is directly measured using a catheter is recorded as "measurement value x of the reference example" on the horizontal axis. Figure 6 In the figure, the measurement value y of this embodiment is represented by a point, which is the measurement value x relative to the reference example when measuring blood pressure multiple times.

[0050] exist Figure 6 In the chart shown, when the relationship between the measured value y in this embodiment and the measured value x in the reference example is consistent, that is, the function that satisfies "x = y" is represented by the solid line m10. The calculation is... Figure 6 After showing the approximate formulas for multiple points, it was found that the approximate formula is the straight line shown by the dashed line m11. Note that the dashed line m11 is approximately the same as the solid line m10. Therefore, if the arteriovenous pressure measuring device 10 provided in this embodiment is used, the blood pressure of the subject can be measured with approximately the same level of accuracy as when measuring venous pressure directly using a catheter.

[0051] The calculation unit 441 calculates the value of the air volume VA relative to the internal pressure P of the compression band 20 by taking the first derivative, that is, it calculates the first derivative value dVA / dP. The calculation unit 441 calculates the subject's blood pressure based on the first derivative value dVA / dP and the internal pressure P of the compression band 20, or more specifically, based on the internal pressure P when the first derivative value dVA / dP represents the maximum value.

[0052] Based on this configuration, it becomes easier to detect changes in the internal pressure P of the compression band 20, thus enabling more accurate detection of the subject's blood pressure.

[0053] The arteriovenous pressure measuring device 10 also includes a flow sensor 32. The flow sensor 32 detects the flow rate of air discharged from inside the compression band 20. The accumulator 42 calculates the air capacity VA of the compression band 20 based on the accumulated value of the air flow rate detected by the flow sensor 32 from the time point when air begins to be discharged from inside the compression band 20.

[0054] Based on this configuration, the air capacity VA of the compression belt 20 can be accurately calculated.

[0055] <Second Implementation Method> Next, a second embodiment of the arteriovenous pressure measuring device 10 will be described. Hereinafter, the description will focus on the differences between the arteriovenous pressure measuring device 10 provided in the first embodiment and the arteriovenous pressure measuring device 10 provided in the second embodiment.

[0056] (Composition of an arteriovenous pressure measuring device) In the arteriovenous pressure measuring device 10 provided in this embodiment, the first derivative value dVA / dP is replaced by the value obtained by second-order differentiation of the air volume VA relative to the internal pressure P of the compression band 20; that is, the second derivative value dVA / dP is used. 2 VA / dP 2 It is used to replace the first-order differential value dVA / dP to detect whether the blood vessel changes from a flattened state to a diastolic state.

[0057] Figure 7 The second derivative d of the air volume VA with respect to the internal pressure P of the pressure belt 20 when air is discharged from the pressure belt 20 is calculated. 2 VA / dP 2 Based on this, using the second-order differential value d 2 VA / dP 2 A graph showing the relationship between the two is plotted with the vertical axis as the ordinate and the internal pressure P as the horizontal axis. (Example:) Figure 7 As shown, when the internal pressure P represents "P11", that is, when the blood vessel changes from a flattened state to a diastolic state, the second derivative value d is... 2 VA / dP 2The change from a positive value to a negative value represents the zero value. In other words, the second-order differential value d... 2 VA / dP 2 It crosses zero. Therefore, if we use the second-order differential value d... 2 VA / dP 2 The internal pressure P at zero can be used to detect the subject's blood pressure.

[0058] (The process executed by the control device) Figure 8 The specific steps of the venous pressure measurement process performed by the control device 44 provided in this embodiment are shown. It should be noted that, in Figure 8 In each of the processes shown, by comparing with Figure 5 The same processes shown use the same reference numerals, thus omitting repeated descriptions.

[0059] like Figure 8 As shown, after the processing in step S12, the calculation unit 441 of the control device 44 calculates the second-order differential value d. 2 VA / dP 2 (Step S20) Determine the calculated second-order differential value d 2 VA / dP 2 Does it cross zero (step S21)? The calculation unit 441 calculates the second-order differential value d. 2 VA / dP 2 If the value does not cross zero (step S21: No), return to the processing in step S11. On the other hand, the calculation unit 441 calculates the second-order differential value d... 2 VA / dP 2 When the zero point is crossed (step S21: Yes), proceed with the processing after step S15.

[0060] (Functions and Effects) As described above, in the arteriovenous pressure measuring device 10 provided in this embodiment, the calculation unit 441 calculates the value of the air volume VA relative to the internal pressure P of the compression band 20 after taking the second derivative, that is, calculates the second derivative value d. 2 VA / dP 2 The computation unit 441 is based on the second-order differential value d. 2 VA / dP 2 And the internal pressure P of the compression belt 20, more specifically, based on the second-order differential value d 2 VA / dP 2 The internal pressure P at zero is used to calculate the subject's blood pressure.

[0061] Based on this configuration, it becomes easier to detect changes in the internal pressure P of the compression band 20, thus enabling more accurate detection of the subject's blood pressure.

[0062] (Modified Example) Factors such as the subject's vascular condition may cause the time point at which the blood vessels transition from a flattened state to a diastolic state to deviate from the second derivative value d. 2 VA / dP 2 The point in time that crosses zero. Therefore, for example, such as... Figure 7 As shown, it can also be based on the second-order differential value d. 2 VA / dP 2 This represents the internal pressure P12 at the minimum value and the second derivative d. 2 VA / dP 2 P13 represents the internal pressure at its maximum value, used to measure the blood pressure of the subject.

[0063] <Third Implementation Method> Next, a third embodiment of the arteriovenous pressure measuring device 10 will be described. Hereinafter, the description will focus on the differences between the arteriovenous pressure measuring device 10 provided in the first embodiment and the arteriovenous pressure measuring device 10 provided in the third embodiment.

[0064] (Composition of an arteriovenous pressure measuring device) The arteriovenous pressure measuring device 10 provided in this embodiment further calculates the capacity of the lumen of veins and other vessels that are flattened by the compression band 20.

[0065] Figure 9 This illustrates the change in internal volume V relative to the internal pressure P of the compression band 20 as the lumen, such as a vein, dilates due to a decrease in the internal pressure P of the compression band 20. Figure 8 In the diagram, "P20" represents the internal pressure P at the point in time when the lumen begins to expand from its flattened state, and "P21" represents the internal pressure P at the point in time when the lumen ends its expansion.

[0066] As the internal pressure P changes from P20 to P21, the relationship between the internal pressure P and the internal volume V of the compression band 20 varies depending on the expansion rate of the lumen, for example, as shown by arrow m20 or arrow m21. Specifically, when the expansion rate of the lumen is slow, the internal volume V changes relative to the internal pressure P of the compression band 20 as shown by arrow m20. On the other hand, when the expansion rate of the lumen is fast, the internal volume V changes relative to the internal pressure P of the compression band 20 as shown by arrow m21.

[0067] When the internal volume V changes relative to the internal pressure P of the compression band 20 in the manner indicated by arrow m20, the second-order differential value d is obtained when the internal pressure P begins to change from "P20". 2 VA / dP 2 This indicates a positive value. Conversely, when the internal volume V changes relative to the internal pressure P of the compression band 20 in the manner shown by arrow m21, the second-order differential value d is given when the internal pressure P begins to change from "P20".2 VA / dP 2 After temporarily representing a negative value, it changes to a positive value. Therefore, when the internal pressure P changes from "P20", if the second derivative value d 2 VA / dP 2 If the value is positive, it indicates that the dilation rate of the lumen is relatively slow. Furthermore, if the second derivative value d... 2 VA / dP 2 A negative value indicates a faster dilation rate in the lumen. This allows us to determine the rate of dilation based on the second-order differential value d when the internal pressure P begins to change from "P20". 2 VA / dP 2 The symbol determines the relaxation velocity of the lumen.

[0068] Furthermore, the smaller the difference between the internal pressure P at the beginning of lumen relaxation and the internal pressure P at the end of lumen relaxation (i.e., the smaller the difference between "P20" and "P21"), the larger the absolute value of the first derivative dVA / dP. Therefore, based on the absolute value of the first derivative dVA / dP, information such as the velocity from the beginning to the end of lumen relaxation can be obtained; in other words, information about the relaxation process of the lumen can be obtained.

[0069] Furthermore, based on the internal pressure P (P20) when the lumen begins to relax and the internal pressure P (P21) when the lumen ends to relax, and using the following formula f4, the volume VL of the lumen compressed by the compression band 20 can be calculated. It should be noted that in formula f4, "V20" represents the internal volume of the compression band 20 when the internal pressure P20 is detected, and "V21" represents the internal volume of the compression band 20 when the internal pressure P21 is detected.

[0070] VL = V20 - V21(f4)

[0071] Equation f4 can be transformed into equation f5 by using the above f1. It should be noted that in equation f5, "m20" represents the air mass inside the compression band 20 when the lumen begins to relax, and "m21" represents the air mass inside the compression band 20 when the lumen ends to relax.

[0072] VL={(m20 / P20)-(m21 / P21)}×R×T(f5)

[0073] As described above, the air mass m inside the compression belt 20 is related to the air capacity VA of the compression belt 20. Therefore, the air capacity VA20 of the compression belt 20 when the lumen begins to expand can be used instead of the air mass m20 inside the compression belt 20 when the lumen begins to expand. Furthermore, the air capacity VA20 of the compression belt 20 when the lumen ends to expand can be used instead of the air mass m21 inside the compression belt 20 when the lumen ends to expand.

[0074] On the other hand, it is possible to use the second-order differential value d 2 VA / dP 2 This is used to detect the time point at which the lumen begins to relax and the time point at which the lumen ends its relaxation. For example, the second-order differential value d 2 VA / dP 2 by Figure 7 The change is shown in the diagram. At this point, at time t10 when the lumen begins to dilate, the second derivative value d... 2 VA / dP 2 It changes significantly from zero to negative values. Therefore, it is possible to base it on the second-order differential value d. 2 VA / dP 2 The significant change from zero to negative values ​​indicates that the lumen has begun to dilate. Furthermore, in the second differential value d... 2 VA / dP 2 At time t11, after the value changes from negative to positive and then to zero, the lumen ends its dilation. Therefore, it is possible to determine the dilation point based on the second-order differential value d. 2 VA / dP 2 The case where the value is zero after crossing zero indicates the end of diastole in the lumen.

[0075] (The process executed by the control device) The control device 44 calculates the capacity VL of the lumen using the above principle.

[0076] Specifically, such as Figure 1 As shown by the dashed line, the arteriovenous pressure measuring device 10 also includes a temperature sensor 46 and an analog-to-digital converter 47. The temperature sensor 46 detects the temperature of the air flowing through the piping 35 and outputs a signal corresponding to the detected air temperature. The analog-to-digital converter 47 converts the output signal of the temperature sensor 46 from an analog signal into a digital value and sends the converted digital value to the control device 44.

[0077] The calculation unit 441 of the control device 44 obtains information about the temperature T of the air flowing through the piping 35 based on the digital value sent by the analog-to-digital converter 47.

[0078] Furthermore, the calculation unit 441 will calculate the second-order differential value d. 2 VA / dP 2The air capacity VA of the compression band 20 calculated by the accumulator 42 when the change exceeds a predetermined value in the negative direction is stored as the air capacity VA20 of the compression band 20 when the lumen begins to relax. Furthermore, the calculation unit 441 stores the air capacity VA20 of the compression band 20 when the second derivative value d... 2 VA / dP 2 The internal pressure P of the compression band 20 calculated by the filter circuit 43 when the pressure changes beyond a predetermined value in the negative direction is stored as the internal pressure P20 of the compression band 20 when the lumen begins to expand. In this embodiment, the internal pressure P20 is equivalent to the first internal pressure, and the air capacity VA20 is equivalent to the first fluid capacity.

[0079] Furthermore, the calculation unit 441 will calculate the second-order differential value d 2 VA / dP 2 The air capacity VA of the compression band 20 calculated by the accumulator 42 when it reaches zero after crossing zero is stored as the air capacity VA21 of the compression band 20 when the lumen section ends its relaxation. Furthermore, the calculation unit 441 stores the second-order differential value d... 2 VA / dP 2 The internal pressure P of the compression band 20, calculated by the filter circuit 43 when it reaches zero after crossing zero, is stored as the internal pressure P21 of the compression band 20 when the lumen ends its expansion. In this embodiment, the internal pressure P21 is equivalent to the second internal pressure, and the air capacity VA21 is equivalent to the second fluid capacity.

[0080] Then, the calculation unit 441 calculates the capacity VL of the cavity based on the calculated internal pressure P20, internal pressure P21, air capacity VA20, air capacity VA21, and air temperature T. The display unit 442 of the control device 44 displays the information of the capacity VL of the cavity calculated by the calculation unit 441 on the display device 45.

[0081] (Functions and Effects) As described above, in the arteriovenous pressure measuring device 10 provided in this embodiment, the calculation unit 441 detects the diastolic start time and diastolic end time based on the internal pressure P of the compression band 20 detected by the pressure sensor 34 when the pressure inside the compression band 20 is reduced, and the air volume VA of the compression band 20 calculated by the accumulator 42. The diastolic start time is the time when the lumen begins to diastolic from the locked state, and the diastolic end time is the time when the lumen ends to diastolic. The lumen is located at the body part of the subject wearing the compression band 20. Furthermore, the calculation unit 441 calculates the volume VL of the lumen based on the first internal pressure P20 and the first air volume VA20 of the compression band 20 detected by the pressure sensor 34 and the accumulator 42 at the diastolic start time, and the second internal pressure P21 and the second air volume VA21 of the compression band 20 detected by the pressure sensor 34 and the accumulator 42 at the diastolic end time, respectively. The lumen is located at the body part of the subject wearing the compression band 20.

[0082] Based on this configuration, information about the volume VL of the lumen in the subject can be further obtained. Furthermore, by observing the display device 45, the volume VL of the lumen can also be determined, thus further confirming information about the subject's blood volume.

[0083] <Fourth Implementation Method> Next, a fourth embodiment of the arteriovenous pressure measuring device 10 will be described. Hereinafter, the description will focus on the differences between the arteriovenous pressure measuring device 10 provided in the first embodiment and the arteriovenous pressure measuring device 10 provided in the fourth embodiment.

[0084] (Composition of an arteriovenous pressure measuring device) The arteriovenous pressure measuring device 10 provided in this embodiment further calculates compliance information representing vascular elasticity.

[0085] Specifically, vascular compliance (VC) can be calculated using the following formula f6. It should be noted that in formula f6, "ΔV" is used... "ΔP" represents the change in internal volume V of the compression band 20 when the blood vessel changes from a flattened state to a diastolic state, and "ΔP" represents the change in internal pressure P of the compression band when the blood vessel changes from a flattened state to a diastolic state.

[0086] VC = ΔV / ΔP(f6).

[0087] The internal volume V20 and internal pressure P20 of the compression band 20 when the lumen begins to dilate, as described in the third embodiment, and the internal volume V21 and internal pressure P21 of the compression band 20 when the lumen ends to dilate, as described in the third embodiment, can be used to calculate the change in internal volume ΔV and the change in internal pressure ΔP of the compression band 20 when the blood vessel changes from a flattened state to a dilated state, using the following formulas f7 and f8.

[0088] ΔV = V20 - V21(f7) ΔP = P20 - P21(f8)

[0089] The capacity VL of the lumen shown in Equation f4 can be used as the change in internal volume ΔV of the compression band 20 shown in Equation f7, that is, the change in internal volume ΔV of the compression band 20 can be calculated by Equation f5.

[0090] (The process executed by the control device) The calculation unit 441 of the control device 44 calculates the change in internal volume ΔV of the compression band 20 using the above formula f5. Furthermore, the calculation unit 441 calculates the change in internal pressure ΔP of the compression band 20 based on the internal pressure P20 detected when the lumen begins to dilate and the internal pressure P21 of the compression band 20 when the lumen ends to dilate, using the above formula f8. Then, the calculation unit 441 calculates the vascular compliance VC based on the calculated change in internal volume ΔV and internal pressure ΔP of the compression band 20, using the above formula f6. The display unit 442 of the control device 44 displays the vascular compliance VC calculated by the calculation unit 441 on the display device 45.

[0091] (Functions and Effects) As described above, in the arteriovenous pressure measuring device 10 provided in this embodiment, its calculation unit 441 calculates the vascular compliance VC based on the lumen volume VL, the first internal pressure P20 of the compression band 20, and the second internal pressure P21 of the compression band 20.

[0092] Based on this configuration, information on the compliance VC of the subject's blood vessels can be further obtained. Furthermore, the compliance VC of the subject's blood vessels can be grasped by observing the display device 45, thus enabling a more precise understanding of the state of the blood vessels.

[0093] <Fifth Implementation Method> Next, the fifth embodiment of the arteriovenous pressure measuring device 10 will be described. Hereinafter, the description will focus on the differences between the arteriovenous pressure measuring device 10 provided in the first embodiment and the arteriovenous pressure measuring device 10 provided in the fifth embodiment.

[0094] (Composition of an arteriovenous pressure measuring device) The arteriovenous pressure measuring device 10 of this embodiment further displays the subject's respiratory status on the display device 45.

[0095] According to the inventor's experiments, the above second-order differential value d was found. 2 VA / dP 2 The vibration is not caused by the pulsation of blood, but by the subject's breathing. Specifically, the vibration is caused by the experimental measurement of the second-order differential value d. 2 VA / dP 2 After considering the changes over time and the changes in the internal pressure P of the compression band 20 accompanying arterial pulsation, it is possible to obtain... Figure 10 The chart shown. Figure 10 In the diagram, the second-order differential value d is represented by a solid line. 2 VA / dP 2 The change in internal pressure P of the compression band 20 accompanying arterial pulsation over time is represented by a dashed line. Figure 10 It can be seen that the second-order differential value d 2 VA / dP 2 There is no correlation between the time-varying changes in the internal pressure P of the compression band 20 accompanying arterial pulsation and the time-varying changes in the pressure P.

[0096] On the other hand, according to the second-order differential value d 2 VA / dP 2 The periodicity of change over time reveals the second-order differential value d. 2 VA / dP 2 The changes over time are affected by the subject's breathing. This is because, for example, veins connect to the lungs via the pulmonary artery from the right atrium and right ventricle; therefore, changes in intrapulmonary pressure caused by breathing will lead to changes in pulmonary artery pressure, and also affect venous pressure. The first-order differential value dVA / dP also oscillates due to the subject's breathing.

[0097] (The process executed by the control device) The display unit 442 in this embodiment will Figure 11 The second-order differential value d is represented by a solid line in the middle. 2 VA / dP 2 The change is displayed on display device 45. Furthermore, based on the second-order differential value d... 2 VA / dP 2 When determining the subject's blood pressure based on the internal pressure P of the compression band 20, the display unit 442 visually displays the value of the internal pressure P of the compression band 20 at the time of determining the subject's blood pressure, as well as the second derivative value d. 2 VA / dP 2 The value.

[0098] It should be noted that, similarly, the display unit 442 can also... Figure 11 The change in the first derivative value dVA / dP, represented by a single-dotted line, and the internal pressure P of the compression band 20 when determining the subject's blood pressure, as well as the value of the first derivative value dVA / dP, are displayed on the display device 45.

[0099] (Functions and Effects) As described above, in the arteriovenous pressure measuring device 10 provided in this embodiment, its display unit 442 further displays the change of the first-order differential value dVA / dP, or further displays the second-order differential value d 2 VA / dP 2 The changes.

[0100] Based on this configuration, for example, medical personnel measuring the subject's blood pressure status can confirm the first-order differential value dVA / dP or the second-order differential value d displayed on the display device 45. 2 VA / dP 2 Changes in blood pressure can confirm whether it is accurately detected relative to the subject's breathing state.

[0101] It should be noted that if medical personnel determine that the timing of measuring the subject's blood pressure is inappropriate, the determined value of the internal pressure P of the compression band 20, which should be used as the subject's blood pressure, can be revised. Therefore, medical personnel can confirm either the first-order derivative dVA / dP or the second-order derivative d... 2 VA / dP 2 The actual changes in pressure P of the compression belt 20 can be arbitrarily altered, thereby enabling more accurate measurement of the subject's blood pressure.

[0102] <Other Implementation Methods> It should be noted that the above-described implementation methods can also be implemented in the following ways.

[0103] For example, the arteriovenous pressure measuring device 10 provided in various embodiments is not limited to measuring the venous pressure of a subject, but can also be used to measure the arterial pressure of a subject. Furthermore, the arteriovenous pressure measuring device 10 can simultaneously measure both venous and arterial pressure.

[0104] This embodiment is not limited to the specific examples described above. Any design modifications appropriately added by those skilled in the art in the above specific examples, as long as they possess the features of this disclosure, are also included within the scope of this disclosure. The elements, their configurations, conditions, shapes, etc., of each of the above specific examples are not limited to the illustrated content and can be appropriately modified. The combinations of the elements of each of the above specific examples can be appropriately changed as long as they do not create technical contradictions.

Claims

1. An arteriovenous pressure measuring device, comprising: The fluid inlet section increases the pressure inside the compression band worn by the subject by allowing fluid to flow into the band. The fluid discharge section reduces the pressure inside the compression belt by discharging the fluid from inside the compression belt. The pressure detection unit detects the internal pressure of the compression band; The capacity detection unit detects the capacity of the fluid present inside the compression belt; as well as The calculation unit calculates the subject's blood pressure based on the internal pressure of the compression band detected by the pressure detection unit when the fluid is discharged from the inside of the compression band, and the fluid volume of the compression band detected by the volume detection unit.

2. The arteriovenous pressure measuring device according to claim 1, wherein, The calculation unit calculates the subject's venous pressure as the subject's blood pressure.

3. The arteriovenous pressure measuring device according to claim 1, wherein, The calculation unit calculates the subject's arterial pressure as the subject's blood pressure.

4. The arteriovenous pressure measuring device according to claim 1, wherein, The calculation unit calculates a first-order differential value, which is the value obtained by differentiating the fluid volume of the compression belt with respect to the internal pressure of the compression belt. The calculation unit calculates the subject's blood pressure based on the first-order differential value and the internal pressure of the compression band.

5. The arteriovenous pressure measuring device according to claim 4, wherein, The calculation unit calculates the subject's blood pressure based on the internal pressure of the compression band when the first-order differential value represents the maximum value.

6. The arteriovenous pressure measuring device according to claim 4, wherein, The arteriovenous pressure measuring device also includes a display unit that shows the change of the first-order differential value.

7. The arteriovenous pressure measuring device according to claim 1, wherein, The calculation unit calculates a second-order differential value, which is the value obtained by differentiating the fluid capacity of the compression belt with respect to the internal pressure of the compression belt. The calculation unit calculates the subject's blood pressure based on the second-order differential value and the internal pressure of the compression band.

8. The arteriovenous pressure measuring device according to claim 7, wherein, The calculation unit calculates the subject's blood pressure based on the internal pressure of the compression band when the second derivative value crosses zero.

9. The arteriovenous pressure measuring device according to claim 7, wherein, The calculation unit calculates the subject's blood pressure based on the internal pressure of the compression band when the second-order differential value represents the minimum value.

10. The arteriovenous pressure measuring device according to claim 7, wherein, The arteriovenous pressure measuring device also includes a display unit that shows the changes in the second-order differential value.

11. The arteriovenous pressure measuring device according to claim 1, wherein, The arteriovenous pressure measuring device further includes a flow detection unit that detects the flow rate of the fluid discharged from the inside of the compression band; The capacity detection unit calculates the fluid capacity of the compression belt based on the cumulative value of the fluid flow rate detected by the flow detection unit.

12. The arteriovenous pressure measuring device according to claim 1, wherein, The calculation unit detects the diastolic start time and diastolic end time based on the internal pressure of the compression band detected by the pressure detection unit when the fluid is discharged from the inside of the compression band, and the fluid volume of the compression band detected by the volume detection unit. The diastolic start time is the time when the lumen begins to diastolic from the locked state, and the diastolic end time is the time when the lumen ends to diastolic. The lumen is located on the body part of the subject wearing the compression band. The calculation unit further calculates the capacity of the lumen portion based on the first internal pressure and first fluid volume of the compression band detected by the pressure detection unit and the volume detection unit at the start of diastole, and the second internal pressure and second fluid volume of the compression band detected by the pressure detection unit and the volume detection unit at the end of diastole, respectively. The lumen portion exists in the body part of the subject wearing the compression band.

13. The arteriovenous pressure measuring device according to claim 12, wherein, The calculation unit further calculates the compliance of the blood vessel based on the capacity of the lumen, the first internal pressure, and the second internal pressure.

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