JP2011045450A - Blood viscosity estimation method, blood viscosity ratio estimation method, blood viscosity monitoring device, and blood viscosity ratio monitoring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a blood viscosity estimation method for continuously measuring blood viscosity, a blood viscosity ratio estimation method for measuring a blood viscosity ratio, a blood viscosity monitoring device, and a blood viscosity ratio monitoring device. <P>SOLUTION: The blood viscosity estimation method includes: a process of measuring the entrance pressure and exit pressure of an artificial lung; a process of measuring the flow rate of blood flowing through the artificial lung; and a process of calculating the blood viscosity from the entrance pressure, the exit pressure and the flow rate of the blood. In addition to the respective processes, the blood viscosity ratio estimation method includes: a process of measuring the hematocrit value of the blood and a blood temperature; a process of calculating normal blood viscosity from the hematocrit value and the blood temperature; and a process of calculating the viscosity ratio of the blood viscosity and the normal blood viscosity. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for estimating blood viscosity in extracorporeal circulation, a method for estimating blood viscosity ratio, a blood viscosity monitoring device, and a blood viscosity ratio monitoring device.

  Extracorporeal circulation is performed to perform open heart surgery on lesions inside the heart. Extracorporeal circulation is a method in which a part of venous blood that returns to the heart is guided outside the body, and artificial blood is artificially converted from the pulmonary blood outside the body using an artificial lung. In this operation, the physiological homeostasis including the hemodynamics of the living body of the patient who is interrupting cardiac blood flow is maintained, and oxygen is continuously supplied.

  In the blood circulation circuit used for extracorporeal circulation, there is a possibility that the activated whole blood clotting time (ACT (Activated Whole Blood Clotting Time)) varies depending on the administration or temperature change of the anticoagulant, infusion, or transfusion during circulation. is there. If ACT cannot be maintained at an appropriate value, a thrombus may be formed.

  For this reason, in the extracorporeal circulation, it is required to control the blood so that it does not solidify, and measurement of ACT is indispensable as monitoring the optimum amount of heparin that is an anticoagulant administered during surgery.

  ACT is obtained by activating a coagulation reaction by activating a contact phase of intrinsic coagulation with an activator of whole blood and measuring the time required for fibrin formation. During the operation, an ACT measuring device is installed in the operating room, and the ACT is regularly measured.

  In addition, Patent Document 1 includes a pressure measuring unit at two locations upstream of the blood pump and downstream of the dialyzer for the blood circuit for artificial dialysis. From the sum and difference of the pressures of both pressure measuring units, An apparatus for continuously measuring the blood pressure and blood viscosity of an arterial shunt is disclosed.

Japanese Patent Laid-Open No. 3-193059

  The measurement by the ACT measurement device is sample measurement. A general method is to measure the time from blood collection until it solidifies. In extracorporeal circulation, heparin is administered to make blood harder, so generally it takes about 5 minutes for blood to harden. Thus, since it takes a certain time until ACT is measured, there is a problem that ACT cannot be continuously monitored.

  The device disclosed in Patent Document 1 is used for artificial dialysis, and cannot be directly applied to extracorporeal circulation using an artificial lung.

  The present invention has been made in view of the above-mentioned matters, and the object thereof is a blood viscosity estimation method capable of continuously estimating blood viscosity, a blood viscosity ratio estimation method capable of continuously estimating blood viscosity ratio, and blood viscosity monitoring. An object of the present invention is to provide a device and a blood viscosity ratio monitoring device.

（式中、ΔＰは出口圧力と入口圧力との差、Ｑは血液の流量、Ｒ（η）、及びα（η）はそれぞれ血液粘度に基づく人工肺固有の関数を示す。） The blood viscosity estimation method according to the first aspect of the present invention includes:
Measuring the inlet pressure and outlet pressure of the oxygenator;
Measuring the flow rate of blood flowing through the oxygenator;
Calculating the blood viscosity from the inlet pressure, the outlet pressure, and the blood flow rate based on the following equation 1;
It is characterized by including.

(In the formula, ΔP is the difference between the outlet pressure and the inlet pressure, Q is the blood flow rate, and R (η) and α (η) are functions inherent to the artificial lung based on the blood viscosity.)

（式中、ΔＰは出口圧力と入口圧力との差、ηは血液粘度、Ｃ_０〜Ｃ_ｎ、Ｋ及びａ_０〜ａ_ｍはそれぞれ人工肺の固有定数、Ｑは血液の流量を示す。） The blood viscosity estimation method according to the second aspect of the present invention includes:
Measuring the inlet pressure and outlet pressure of the oxygenator;
Measuring the flow rate of blood flowing through the oxygenator;
Calculating the blood viscosity from the inlet pressure, the outlet pressure, and the blood flow rate based on the following equation 2;
It is characterized by including.

(The difference in the formula, [Delta] P is the outlet pressure and the inlet pressure, eta blood _{viscosity, C} 0 _{~C n,} K and _a 0 ~a _m unique constant for each artificial lung, Q is shows the flow of blood.)

The method for estimating the blood viscosity ratio according to the present invention comprises:
Measuring the inlet pressure and outlet pressure of the oxygenator;
Measuring the flow rate of blood flowing through the oxygenator;
Calculating blood viscosity from the inlet pressure, the outlet pressure, and the blood flow rate;
Measuring the hematocrit value and blood temperature of the blood;
Calculating a normal blood viscosity from the hematocrit value and the blood temperature;
Calculating a blood viscosity ratio between the blood viscosity and the normal blood viscosity,
The blood viscosity is obtained using the blood viscosity estimation method described above.

（式中、η_{０（Ｈｔ（ｘ），Ｔｂ（ｙ））}はヘマトクリット値ｘ％（Ｈｔ（ｘ））、血液温度ｙ℃（Ｔｂ（ｙ））における正常血液粘度、η_{０（Ｈｔ（ａ），Ｔｂ（ｙ））}は、所定ヘマトクリット値ａ％（Ｈｔ（ａ））、血液温度ｙ℃（Ｔｂ（ｙ））における正常血液粘度、η_{０（Ｈｔ（ｘ），Ｔｂ（ｂ）}／η_{０（Ｈｔ（ａ），Ｔｂ（ｂ））}は、所定血液温度ｂ℃（Ｔｂ（ｂ））におけるヘマトクリット値ｘ％（Ｈｔ（ｘ））の正常血液粘度と所定ヘマトクリット値ａ％（Ｈｔ（ａ））の正常血液粘度との比を示す。） Further, the normal blood viscosity may be calculated based on the following equation 4.

( _Where η _{0 (Ht (x), Tb (y))} is the normal blood viscosity at hematocrit value x% (Ht (x)), blood temperature y ° C. (Tb (y)), η _{0 (Ht (a ), Tb (y))} is a predetermined hematocrit value a% (Ht (a)), normal blood viscosity at a blood temperature y ° C. (Tb (y)), η _{0 (Ht (x), Tb (b)} / η _{0 (Ht (a), Tb (b))} is a normal blood viscosity of a hematocrit value x% (Ht (x)) and a predetermined hematocrit value a% (Ht (a ₎ at a predetermined blood temperature b ° C. (Tb (b)). )) Normal blood viscosity ratio.)

The blood viscosity monitoring apparatus according to the present invention is:
An inlet pressure measuring device for measuring the inlet pressure of blood flowing into the oxygenator;
An outlet pressure measuring device for measuring an outlet pressure of blood discharged from the oxygenator;
A flow rate measuring device for measuring a flow rate of blood flowing through the oxygenator;
And an arithmetic unit that calculates blood viscosity from the inlet pressure, the outlet pressure, and the blood flow rate.

  Further, a display device for displaying the blood viscosity and a recording device for recording the blood viscosity may be provided.

The blood viscosity ratio monitoring apparatus according to the present invention is:
An inlet pressure measuring device for measuring the inlet pressure of blood flowing into the oxygenator;
An outlet pressure measuring device for measuring an outlet pressure of blood discharged from the oxygenator;
A flow rate measuring device for measuring a flow rate of blood flowing through the oxygenator;
A hematocrit value measuring device for measuring a hematocrit value of blood flowing through the oxygenator;
A blood temperature measuring device for measuring the blood temperature of blood flowing through the oxygenator;
The blood viscosity is calculated from the inlet pressure, the outlet pressure, and the blood flow rate, the normal blood viscosity is calculated from the hematocrit value and the blood temperature, and the blood viscosity between the blood viscosity and the normal blood viscosity And an arithmetic unit for calculating the ratio.

  Further, a display device for displaying the blood viscosity ratio and a recording device for recording the blood viscosity ratio may be provided.

  The blood viscosity estimation method according to the present invention can continuously estimate the blood viscosity that can be used as a blood coagulation judgment index by measuring the inlet pressure, outlet pressure, and blood flow rate of the artificial lung in extracorporeal circulation. There are advantages.

  In addition, in the blood viscosity ratio estimation method according to the present invention, in addition to the above blood viscosity, a normal blood viscosity can be continuously measured by measuring a hematocrit value and a blood temperature. There is an advantage that the ratio between the blood viscosity that can be used and the normal blood viscosity can be continuously estimated.

  In addition, the blood viscosity monitoring device and the blood viscosity ratio monitoring device according to the present invention can continuously monitor the blood viscosity and blood viscosity ratio, which can be used as blood coagulation indicators, respectively. Thus, it is possible to perform an appropriate treatment such as determination of the optimal dose so that the blood does not clot.

It is process drawing of the estimation method of blood viscosity. It is a schematic block diagram of the blood viscosity monitoring apparatus used for the blood viscosity estimation method. It is an experimental result of the flow rate and pressure difference of the liquid circulated through the oxygenator. It is a graph which shows the relationship between (eta) and Cr (eta). It is a graph which shows the relationship between (eta) and exp (Ca (eta)). This is an estimated viscosity when a liquid having an actual viscosity of 1.13 cP is circulated through the oxygenator. It is an estimated viscosity when a liquid having an actual viscosity of 1.43 cP is circulated through the artificial lung. This is an estimated viscosity when a liquid having an actual viscosity of 1.84 cP is circulated through the artificial lung. This is an estimated viscosity when a liquid having an actual viscosity of 2.42 cP is circulated through the oxygenator. This is an estimated viscosity when a liquid having an actual viscosity of 3.03 cP is circulated through the artificial lung. It is an experimental result of the flow rate and pressure difference of the liquid when gas is circulated through the oxygenator. It is process drawing of the estimation method of a blood viscosity ratio. It is a schematic block diagram of the blood viscosity ratio monitoring apparatus used for the blood viscosity ratio estimation method. It is a graph which shows the relationship between blood temperature, hematocrit value, and normal blood viscosity.

(Blood viscosity estimation method and blood viscosity monitoring device)
First, a method for estimating blood viscosity will be described. As shown in the process diagram of FIG. 1, the blood viscosity estimation method includes the steps of measuring the inlet pressure (P _in ) and the outlet pressure (P _out ) of the oxygenator and the flow rate (Q) of blood flowing through the oxygenator. It comprises a step of measuring, and a step of calculating blood viscosity (η) from the measured inlet pressure, outlet pressure and blood flow rate.

  This blood viscosity estimation method is realized by the blood viscosity monitoring apparatus 1 shown in FIG. The artificial lung 12 is connected to a blood inflow path 11 through which blood from the vena cava flows and a blood outflow path 13 through which blood flows out to the aorta. An inlet pressure measuring device 14 for measuring the inlet pressure of the artificial lung 12 is arranged in the blood inflow passage 11, and an outlet pressure measuring device 15 for measuring the outlet pressure of the artificial lung 12 in the blood outflow passage 13, and the artificial lung 12. A flow rate measuring device 16 for measuring the flow rate of the blood flowing through is disposed. Then, the measured values of the inlet pressure, the outlet pressure, and the flow rate are sent, the calculation device 21 for calculating the blood viscosity from these, the display device 22 for continuously displaying the blood viscosity, and the blood viscosity are continuously recorded. A recording device 23 is provided.

  Below, each process is demonstrated.

(Step of measuring the inlet pressure and outlet pressure of the oxygenator)
The inlet pressure of the oxygenator 12 is measured. The inlet pressure may be measured by the inlet pressure measuring device 14 disposed in the blood inflow path 11. In addition, the outlet pressure of the artificial lung 12 is measured. The outlet pressure may be measured by the outlet pressure measuring device 15 arranged in the blood outflow path 13. As the inlet pressure measuring device 14 and the outlet pressure measuring device 15, various known pressure gauges may be used.

(Process to measure blood flow)
The flow rate of blood flowing through the artificial lung 12 is measured. The blood flow rate may be measured by the flow rate measuring device 16 disposed in the blood outflow path 13. The flow measuring device 16 may use various known flow meters.

(Step of calculating blood viscosity)
The inlet pressure P _in , the outlet pressure P _out , and the blood flow rate Q measured as described above are transmitted to the computing device 21, and the viscosity of blood flowing through the artificial lung 12 is calculated by the computing device 21.

The computing device 21 calculates the blood viscosity η based on the following formula 1. In Equation 1, ΔP is the difference between the outlet pressure and the inlet pressure, Q is the blood flow rate, and R (η) and α (η) are functions inherent to the artificial lung based on blood viscosity. Then, the blood viscosity η satisfying Equation 1 is calculated by an implicit method described later by simulation in the arithmetic unit 21.

Here, Formula 1 will be described. Formula 1 is a formula derived from experimental results of inlet pressure, outlet pressure, and flow rate of an artificial lung by flowing liquids of various viscosities through the oxygenator. More specifically, it can be expressed as the following formula 2.

In the formula 2, C ₀ -C _n is intrinsic constants defining the amount of pressure loss of the various artificial lung which depends on the flow rate Q of the blood viscosity η and blood, K and a ₀ ~a _m the blood flow It is an eigen constant that defines the rate of participation of the viscous force and the inertial force of the pressure loss that varies depending on Q. Note that n and m are positive integers, which may be singular or plural, and the number of each term may be the same or different. When the number of terms is large, an approximate value of blood viscosity can be derived with higher accuracy.

  In the following, an example of how to derive Equation 1, that is, Equation 2, will be described together with experimental results.

  First, glycerin was added to 2 L of water every 200 mL to prepare a plurality of liquids having different viscosities (1.13 cP, 1.43 cP, 1.84 cP, 2.42 cP, 3.03 cP).

  Each viscosity liquid was circulated through an artificial lung made by Izumi Kogyo Medical Co., Ltd.

When the liquid of each viscosity is flowing, the rotational speed of the centrifugal pump that circulates the liquid is increased, and the liquid flow rate Q (L / min), inlet pressure P _in (mmHg), outlet pressure for each rotational speed. The average value of P _out (mmHg) was determined.

Then, calculates a pressure difference ΔP between the inlet pressure P _in the outlet pressure P _out, it was plotted relationship between the flow rate Q and pressure difference ΔP as shown in FIG.

From FIG. 3, a relational expression between the flow rate Q and the pressure difference ΔP in each viscosity liquid was derived. Each relational expression and correlation coefficient are as shown in Table 1. Since the correlation coefficients are all close to 1, each can be said to be an appropriate relational expression.

  Then, formula 2 can be defined by deriving a general formula that can satisfy the respective relational expressions in Table 1.

For example, n, m, and k in Formula 2 are each set to 1, C ₀ and a ₀ are set to 0, and constants (2.9951, 3.358, 4.6257,. 2272, 5.9751) is defined as Crη, and exponents (1.7158, 1.7021, 1.609, 1.6161, 1.6137) are defined as exp (Caη) +1, respectively, the following equation 3 can be derived. . Cr and Ca are intrinsic constants of the artificial lung, respectively.

Further, from the relational expressions in Table 1, Crη, exp (Caη) +1, and exp (Caη) at each viscosity are as shown in Table 2.

  Then, as shown in FIG. 4, the viscosity shown in Table 2 was plotted with the horizontal axis and Crη as the vertical axis. Then, by the least square method, a straight line (general formula: y = aη) having the smallest residual with each plot is drawn, and its slope (a in the general formula) corresponds to Cr, so Cr = 2.1888. Can be requested.

Moreover, as shown in FIG. 5, the viscosity shown in Table 2 is plotted with the horizontal axis and exp (Caη) as the vertical axis. In hydrodynamics, in the case of turbulent flow, it is considered that ΔP is proportional to the square of Q when the viscosity is 0, and is proportional to the first power of Q when the viscosity is infinite. Therefore, the residual with each plot is obtained by the least square method so that exp (Caη) becomes 1 when the viscosity is 0 and exp (Caη) converges to 0 when the viscosity is infinite. A logarithmic curve (general formula: y = e ^aη ) that ^minimizes is derived. Since a in this general formula corresponds to Ca, Ca = −0.2055 can be obtained.

Through the above steps, the following expression 3 ′ can be derived.

  In the expression 3 'obtained by calculating each intrinsic constant of the expression 3, if the values of the inlet pressure, the outlet pressure, and the flow rate can be measured, the unknown is only the viscosity η. However, the expression 3 'is an implicit function expression for η. For this reason, η is estimated from Equation 3 ′ using a numerical solution such as the known Newton-Lapson method. Thereby, η can be calculated.

とし、ｆ（η）の一次微分であるｆ’（η）を、

として計算し、ηの推定値をη_ｎとしたときの近似解η_ｎ＋１を、

とする。そして、式３ｄに示す、式３ｂと式３ｃの残差ε

が要求される測定精度以内に収束するまで反復する。このようにして、粘度ηを算出することができる。 Specifically, how to estimate η by numerical solution is described with respect to Equation 3,

And f ′ (η), which is the first derivative of f (η),

An approximate solution eta _{n + 1} when calculated, the estimated value of eta was eta _n as,

And And the residual ε of Equation 3b and Equation 3c shown in Equation 3d

Iterate until it converges within the required measurement accuracy. In this way, the viscosity η can be calculated.

  In order to examine the validity of Equation 3 ′ derived as described above, liquids having different viscosities (actual viscosities of 1.13 cP, 1.43 cP, 1.84 cP, 2.42 cP, and 3.03 cP, respectively) Circulated to the lungs. The rotational speed of the centrifugal pump was gradually increased, the inlet pressure, the outlet pressure, and the flow rate were measured at each rotational speed, and the viscosity of the circulating liquid was estimated using Equation 3 '.

  The estimation results of the viscosity are shown in FIGS. 6, 7, 8, 9, and 10, respectively. 6 is an estimated viscosity when a liquid having an actual viscosity of 1.13 cP is circulated, FIG. 7 is an estimated viscosity when a liquid having an actual viscosity of 1.43 cP is circulated, and FIG. 8 is a circulation of a liquid having an actual viscosity of 1.84 cP. FIG. 9 shows the estimated viscosity when the liquid having the actual viscosity of 2.42 cP is circulated, and FIG. 10 shows the estimated viscosity when the liquid having the actual viscosity of 3.03 cP is circulated.

  The range between the broken lines in FIGS. 6 to 10 indicates the range of 5% error in actual viscosity. When the flow rate is small due to the circulated liquid, there are some that are out of the error range of 5%. However, the flow rate of blood circulating in the extracorporeal circulation is approximately 4 to 5 L / min although it depends on the physique of the patient. It can be seen that when the flow rate is in the range of 4 to 5 L / min, a liquid with any viscosity is flowed and the actual viscosity is within a 5% error range.

  In addition, in a device such as a pressure measuring device or a flow rate measuring device, a measurement error of about 5% can usually occur. Therefore, this error is also considered as a measurement error. From the above, it can be seen that an approximate value close to the actual viscosity can be estimated in the practical range.

  Moreover, since oxygen gas was supplied to the artificial lung and carbon dioxide gas was exhausted, it was verified whether or not it was related to the approximate expression derived from the influence of gas circulation.

  Glycerin was added to water to prepare three types of liquids having different viscosities, and each was circulated through the artificial lung. The liquid flow rate and the gas flow rate are 1: 1.

  FIG. 11 shows the measurement results of the flow rate of the circulated liquid and the pressure difference ΔP. Referring to FIG. 11, it can be seen that even when a liquid of any viscosity is flowed, there is almost no difference between the presence of gas circulation and the absence of gas circulation. Therefore, even if oxygen gas is supplied to the oxygenator and carbon dioxide gas is exhausted from the oxygenator, the relationship between the blood flow rate Q and the pressure difference ΔP does not change. It can be seen that the approximate expression has validity.

  As described above, an approximate expression for calculating blood viscosity corresponding to each artificial lung can be derived. Then, by continuously measuring the inlet pressure, the outlet pressure, and the blood flow rate, and using the approximate expression, the blood viscosity can be continuously estimated. By continuously displaying the blood viscosity calculated by the computing device 21 on a display device 22 such as a monitor, the operator can recognize it as an indicator of blood coagulation during the operation, and blood does not coagulate such as administration of heparin. As a result, it is possible to perform an appropriate treatment. Further, a threshold value may be provided for blood viscosity, and the operator may be notified when the threshold value is exceeded. Furthermore, the blood viscosity calculated by the calculation device 21 may be continuously recorded by the recording device 23. By recording the blood viscosity during the operation, it can be used as a surgical evaluation or study model.

  If the extracorporeal circulation device is provided with an operation recording function capable of measuring and recording the inlet pressure, the outlet pressure of the artificial lung, and the blood flow rate, this operation recording function may be used. For example, a data signal such as the inlet pressure obtained by the operation recording function may be sent to the arithmetic device via the receiving device to estimate the blood viscosity.

  Further, in the above, as an example, Equation 3 is defined using the two artificial constants of the artificial lung from the respective relational expressions shown in Table 1. However, by increasing the intrinsic constant shown in Equation 2, Each characteristic constant may be obtained by the above method, and an approximate expression that more closely approximates the experimental result may be derived. Then, the blood viscosity may be calculated based on the approximate expression.

(Blood viscosity ratio estimation method and blood viscosity ratio monitoring device)
Next, a method for estimating the blood viscosity ratio will be described. As shown in FIG. 12, the blood viscosity ratio is estimated by measuring the inlet pressure (P _in ) and the outlet pressure (P _out ) of the oxygenator and the flow rate (Q) of blood flowing through the oxygenator. A step of calculating a blood viscosity (η) from the measured inlet pressure, outlet pressure and blood flow rate, a step of measuring a hematocrit value (Ht) and a blood temperature (Tb), and a normal blood viscosity (η ₀ ) and a step of calculating a viscosity ratio (η / η ₀ ) between the blood viscosity (η) and the normal blood viscosity (η ₀ ).

  Here, the normal blood viscosity means the viscosity of blood flowing through the human body at normal time, that is, the blood viscosity flowing through the human body in a state where heparin or the like is not administered, and the normal blood viscosity is The viscosity depends on the hematocrit value in blood and blood temperature. The hematocrit value is a blood cell concentration (%) in blood.

  The blood viscosity ratio estimation method is realized by the blood viscosity ratio monitoring apparatus 2 shown in the schematic configuration diagram of FIG. A blood viscosity ratio monitoring device 2 shown in FIG. 13 is obtained by adding a hematocrit value measuring device 17 and a blood temperature measuring device 18 to the blood viscosity monitoring device 1 shown in FIG.

  The step of measuring the inlet pressure and the outlet pressure of the oxygenator, the step of measuring the flow rate of blood flowing through the oxygenator, the step of calculating the blood viscosity from the measured inlet pressure, outlet pressure, and blood flow rate are described above. Since it is the same as the blood viscosity estimation method, the description thereof is omitted.

(Process to measure hematocrit value)
The hematocrit value measuring device 17 continuously measures the hematocrit value in the blood. The hematocrit value measuring device 17 may be any of various known devices, or may be measured by providing a device capable of measuring the hematocrit value on an artificial lung.

(Process for measuring blood temperature)
The blood temperature measurement device 18 continuously measures the blood temperature. As the blood temperature measuring device 18, various known devices may be used. Since the blood temperature is continuously measured during normal surgery, the blood temperature may be used.

(Step of calculating normal blood viscosity)
The computing device 21 calculates the normal blood viscosity η ₀ from the measured hematocrit value and blood temperature based on the following equation 4.

In Equation 4, η _{0 (Ht (x), Tb (y))} is a normal blood viscosity at a hematocrit value x% (Ht (x)) and a blood temperature y ° C. (Tb (y)), η _{0 (Ht ( a), Tb (y))} is a predetermined hematocrit value a% (Ht (a)), normal blood viscosity at a blood temperature y ° C. (Tb (y)), η _{0 (Ht (x), Tb (b))} / Η _{0 (Ht (a), Tb (b))} is a normal blood viscosity of a hematocrit value x% (Ht (x)) at a predetermined blood temperature b ° C. (Tb (b)) and a predetermined hematocrit value a% (Ht The ratio with the normal blood viscosity of (a)) is shown.

  Here, Formula 4 will be described. As described above, normal blood viscosity refers to the viscosity of blood flowing through a human body at normal time, and the normal blood viscosity depends on the hematocrit value and the blood temperature. These relationships are known to be in the relationship shown in FIG. 14 from the research results of Swan and Reemtsma. Expression 4 is an expression derived from a general expression that satisfies the relationship shown in FIG.

Below, an example is given and demonstrated about how to derive Formula 4. When the predetermined hematocrit value a% in Expression 4 is 50% (Ht (50)), Expression 4 can be expressed as Expression 4 ′.

First, a relational expression between blood temperature and blood viscosity, specifically, a relational expression between blood temperature and normal blood viscosity at a hematocrit value of 50% shown in FIG. 14 is derived. Assuming that the blood temperature is Tb (y), the blood viscosity η _{0 (Ht (50), Tb (y))} with a hematocrit value of 50%, that is, the approximate curve of Ht: 50% in FIG. It can be expressed as an approximate expression shown.

In FIG. 14, the normal blood viscosities at hematocrit values of 72%, 50%, 32%, and 7% at a certain blood temperature are represented by η _{0 (Ht (72))} , η _{0 (Ht (50))} , and η, respectively. _{0 (Ht (32))} , η0 _{(Ht (7))} , η0 _{(Ht (72))} : η0 _{(Ht (50))} : η0 _{(Ht (32))} : η0 _{(Ht It} can be seen that ₍₇₎₎ has a substantially constant relationship regardless of the blood temperature. That is, if the standard blood viscosity with a hematocrit value of 50% at a specific blood temperature is known, the standard blood viscosity with another hematocrit value at the same blood temperature can be calculated from the viscosity ratio. Therefore, the normal blood viscosity at a hematocrit value x%, a predetermined blood temperature b ° C. is η _{0 (Ht (X), Tb (b)),} and the normal blood viscosity at the same blood temperature is 50%, η _{0 (Ht (50), Tb (b))} , the standard blood viscosity ratio η _{0 (Ht (x), Tb (b))} / η _{0 (Ht (50), Tb (b))} is given by Can be expressed by an approximate expression of only the hematocrit value.

₀ eta derived by Equation _{5 (Ht (50), Tb} (y)) to ₀ eta guided by Formula _{6 (Ht (X), Tb} (b)) / η 0 (Ht (50), Tb (b) ₎ To derive equation 4 ′. Therefore, if the blood temperature and the hematocrit value are known, the normal blood viscosity can be obtained based on Equation 4 ′.

  In addition, as an example of Expression 4, the description has been given above of how to derive when the predetermined hematocrit value is 50%, but as described above, the ratio of the normal blood viscosity between different hematocrit values is not dependent on the blood temperature. Since it is substantially constant, the predetermined hematocrit value may be set to a different value to derive Equation 4.

(Step of calculating blood viscosity ratio)
From the blood viscosity η and the normal blood viscosity η ₀ calculated as described above, the arithmetic unit 21 calculates the blood viscosity ratio η / η ₀ . Then, this blood viscosity ratio is displayed on the display device 22.

  As described above, the blood viscosity ratio can be continuously estimated by continuously measuring the inlet pressure, outlet pressure, blood flow rate, blood temperature, and hematocrit value of the artificial lung. By continuously displaying the blood viscosity ratio calculated by the computing device 21 on a display device 22 such as a monitor, the operator can recognize it as an indicator of blood coagulation during the operation, and blood coagulation such as administration of heparin. It is possible to take an appropriate measure so as not to. Further, a threshold value may be provided for the blood viscosity, and the operator may be notified by sound or the like when the threshold value is exceeded. Furthermore, the blood viscosity ratio calculated by the calculation device 21 may be continuously recorded by the recording device 23. By recording the blood viscosity ratio during surgery, it can be used as an evaluation and study model for surgery.

  In addition, when the extracorporeal circulation device is provided with an operation recording function capable of measuring and recording the inlet pressure, the outlet pressure, the blood flow rate, the hematocrit value, and the blood temperature of the oxygenator, this operation recording function may be used. . For example, a data signal such as the inlet pressure obtained by the operation recording function may be sent to the arithmetic device via the receiving device to estimate the blood viscosity ratio.

  As described above, the blood viscosity and the blood viscosity ratio can be continuously estimated. The surgeon should take appropriate measures to prevent medical accidents caused by blood coagulation in extracorporeal circulation using an artificial lung by continuously displaying these on a display device etc. Is possible. Thus, the use in the medical device field is expected.

DESCRIPTION OF SYMBOLS 1 Blood viscosity monitoring apparatus 2 Blood viscosity ratio monitoring apparatus 11 Blood inflow path 12 Artificial lung 13 Blood outflow path 14 Inlet pressure measuring apparatus 15 Outlet pressure measuring apparatus 16 Flow measuring apparatus 17 Hematocrit value measuring apparatus 18 Blood temperature measuring apparatus 21 Arithmetic apparatus 22 Display device 23 Recording device

Claims (8)

Measuring the inlet pressure and outlet pressure of the oxygenator;
Measuring the flow rate of blood flowing through the oxygenator;
Calculating the blood viscosity from the inlet pressure, the outlet pressure, and the blood flow rate based on the following equation 1;
A method for estimating blood viscosity, comprising:

(In the formula, ΔP is the difference between the outlet pressure and the inlet pressure, Q is the blood flow rate, and R (η) and α (η) are functions inherent to the artificial lung based on the blood viscosity.) Measuring the inlet pressure and outlet pressure of the oxygenator;
Measuring the flow rate of blood flowing through the oxygenator;
Calculating the blood viscosity from the inlet pressure, the outlet pressure, and the blood flow rate based on the following equation 2;
A method for estimating blood viscosity, comprising:

(The difference in the formula, [Delta] P is the outlet pressure and the inlet pressure, eta blood _{viscosity, C} 0 _{~C n,} K and _a 0 ~a _m unique constant for each artificial lung, Q is shows the flow of blood.) Measuring the inlet pressure and outlet pressure of the oxygenator;
Measuring the flow rate of blood flowing through the oxygenator;
Calculating blood viscosity from the inlet pressure, the outlet pressure, and the blood flow rate;
Measuring the hematocrit value and blood temperature of the blood;
Calculating a normal blood viscosity from the hematocrit value and the blood temperature;
Calculating a blood viscosity ratio between the blood viscosity and the normal blood viscosity,
A method for estimating a blood viscosity ratio, wherein the blood viscosity is determined using the blood viscosity estimating method according to claim 1. The blood viscosity ratio estimation method according to claim 3, wherein the normal blood viscosity is calculated based on the following expression 4.

( _Where η _{0 (Ht (x), Tb (y))} is the normal blood viscosity at hematocrit value x% (Ht (x)), blood temperature y ° C. (Tb (y)), η _{0 (Ht (a ), Tb (y))} is a predetermined hematocrit value a% (Ht (a)), normal blood viscosity at a blood temperature y ° C. (Tb (y)), η _{0 (Ht (x), Tb (b)} / η _{0 (Ht (a), Tb (b))} is a normal blood viscosity of a hematocrit value x% (Ht (x)) and a predetermined hematocrit value a% (Ht (a ₎ at a predetermined blood temperature b ° C. (Tb (b)). )) Normal blood viscosity ratio.) An inlet pressure measuring device for measuring the inlet pressure of blood flowing into the oxygenator;
An outlet pressure measuring device for measuring an outlet pressure of blood discharged from the oxygenator;
A flow rate measuring device for measuring a flow rate of blood flowing through the oxygenator;
An arithmetic unit for calculating blood viscosity from the inlet pressure, the outlet pressure, and the blood flow rate;
A blood viscosity monitoring apparatus comprising:   The blood viscosity monitoring apparatus according to claim 5, further comprising a display device that displays the blood viscosity and a recording device that records the blood viscosity. An inlet pressure measuring device for measuring the inlet pressure of blood flowing into the oxygenator;
An outlet pressure measuring device for measuring an outlet pressure of blood discharged from the oxygenator;
A flow rate measuring device for measuring a flow rate of blood flowing through the oxygenator;
A hematocrit value measuring device for measuring a hematocrit value of blood flowing through the oxygenator;
A blood temperature measuring device for measuring the blood temperature of blood flowing through the oxygenator;
The blood viscosity is calculated from the inlet pressure, the outlet pressure, and the blood flow rate, the normal blood viscosity is calculated from the hematocrit value and the blood temperature, and the blood viscosity between the blood viscosity and the normal blood viscosity An arithmetic unit for calculating the ratio;
A blood viscosity ratio monitoring device comprising:   The blood viscosity ratio monitoring device according to claim 7, further comprising a display device that displays the blood viscosity ratio and a recording device that records the blood viscosity ratio.

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