Apparatus, computer system and method for determining intrathoracic blood volume and other cardiovascular parameters

Abstract

Apparatus, and a method for determining intraratomic blood volume and other cardiovascular parameters. An apparatus, computer system, method and storage medium for determining intrathoracic blood volume (ITBV) and other cardiovascular parameters of a patient by thermodilution measurements. The apparatus comprises a) temperature influencing means 107 for causing an initial local temperature change in the vicinity of a first location 101 of a patient's vascular system 103, thereby introducing a temperature shift traveling in the bloodstream of the patient, b) a temperature sensing device (117) for measuring the local blood temperature of the patient in a second location (102) of the patient's vascular system (103) downstream of said first location (101); ) coupled to said temperature sensor device (117) and adapted to record said patient's local blood temperature measured in said second location (102) as a function of time to determine a thermodilution curve, (d) said computerized system (104) being further adapted to determine the overall final diastolic blood volume (GEDV) of the patient and the intrathoracic thermovolume (ITTV) of the patient from said thermodilution curve, e) said computer system (104) being further adapted to determine the patient's intratoracal blood volume (ITBV) according to the following formula: ITBV = f (GEDV, ITTV, P) ITBV being intrathoracic blood volume, GEDV being the overall final diastolic blood volume, ITTV being the intrathoracic thermovolume, P being a ventilation channel pressure within the patient's lungs. Determining ITBV not only from GEDV but also as a function of ITTV and P, enhanced accuracy can be obtained, especially if the patient suffers from pulmonary edema or is mechanically ventilated.

Description

"APPARATUS, COMPUTERIZED SYSTEM AND METHOD FOR DETERMINING INTRATHORAXIC BLOOD VOLUME AND OTHER CARDIOVASCULAR PARAMETERS". Field of invention The present invention relates to an apparatus, a computerized system and a method for determining intrathoracic blood volume and other cardiovascular parameters of a patient by thermodilution measurements. Background of the invention The current state of the art in implementing transpulmonary thermodilution measurement involves devices that inject a bolus of thermal indicator into a patient's superior vena cava and measure the temperature response in the patient's systemic circulation, e.g., the patient's femoral artery, to determine the thermodilution curve, i.e., the temperature response as a function of time. From the thermodilution curve, a schematic example of which is illustrated in Fig. 3, where the abscissa (time axis) 1 is linear and the ordinate (temperature difference axis) 2 is logarithmic, various cardiovascular parameters can be derived using computerized systems operating computer programs, which implement parameter calculations as disclosed in WO 93 / 2182 3, the contents of which are included here by citation, and as summarized below. Total cardiac volume (CO2) can be determined by algorithms based on the Stewart-Hamilton equation: (t)dt where Tb is the initial blood temperature, T L V is the temperature of the liquid cake, which is used as a thermal indicator. L is the volume of the thermal indicator, K x K1 and K2 are constants to account for the specific measurement preparation, and AT B (t) is the blood temperature as a function of time with respect to baseline blood temperature T B The thermal indicator can be either colder or warmer relative to blood temperature. To obtain the total cardiac volume, the area under the thermodilution curve has to be determined by mathematical integration. Other parameters that can be derived from the thermodilution curve 3, as schematically illustrated in Fig. 3, include the Exponential Decay Time or Downward Slope Time (DST), that is, the time it takes for the blood temperature difference AT B (t) takes to fall by the factor e' 1 , the Time of Appearance AT, that is, the time interval between the cake injection IT and the first appearance of a noticeable temperature difference AT B (t) and the Average Transit Time MTT. 0 Intrathoracic Thermovolume (ITTV) and intrathoracic blood volume (ITBV) can be determined as follows: ITTV = CO . MIT ITBV = a'. GEDV + b' where a' and b' are species-specific constants and GEDV is the Global End-Diastolic Volume, which can be determined as follows: GEDV = CO . (MTT - DST) An estimate of extravascular thermovolume can be determined as the difference between intrathoracic thermovolume (ITTV) and intrathoracic blood volume (ITBV). ETV = ITTV - ITBV The extravascular volume correlates closely with the degree of extravascular lung fluid, provided there are no significant perforation defects in the lungs (e.g., massive pulmonary embolism or large simple embolism). Transpulmonary thermodilution has proven to be a reliable technique for assessing total cardiac volume, cardiac preload, and extravascular lung water (EVLW), that is, for quantifying pulmonary edema. The estimation of EVLW by injection of a single thermal indicator is based on the aforementioned relationship ITBV = a' . GEDV + b'. This method has been shown to compare favorably with the double indicator dilution technique (thermostain) and with ex-vivo gravimetric methods. However, for mechanically ventilated patients and patients suffering from severe pulmonary edema, the results were not entirely satisfactory. It is therefore an objective of the present invention to provide a new apparatus, a new computerized system and a new method allowing the determination of intrathoracic blood volume by single-indicator transpulmonary thermodilution with enhanced accuracy, especially for patients suffering from severe pulmonary edema and / or mechanically ventilated patients. Summary of the invention The inventors discovered that several factors (especially pulmonary edema and ventilation duct pressure) affect the cardiac / pulmonary blood volume ratio, and therefore the estimation of EVLW by transpulmonary thermodilution. In fact, edematous areas of the lung can compress pulmonary vessels and intensify pulmonary vasoconstriction, both factors that can reduce the actual pulmonary blood volume and therefore lead to an overestimation of ITBV and an underestimation of extravascular lung water (EVLW) (when ITBV is estimated as 1.25 x GEDV). Similarly, any increase in ventilation duct pressure (related either to an increase in tidal volume [volume inspired with each breath] or to the application of a positive end-expiratory pressure) can induce a decrease in pulmonary blood volume, which can also alter the cardiac / pulmonary blood volume ratio. To achieve the aforementioned objective, the present invention provides an apparatus for determining intrathoracic blood volume (ITBV) and other cardiovascular parameters of a patient by measuring... Thermodilution comprising: temperature-influencing means to induce an initial local temperature change in the vicinity of a first location in a patient's vascular system, thereby introducing a temperature shift traveling in the patient's bloodstream; a temperature-sensing device to measure the patient's local blood temperature at a second location in the patient's vascular system downstream of said first location; a computerized system connected to said temperature-sensing device and adapted to record the patient's local blood temperature measured at said second location as a function of time to determine a thermodilution curve; said computerized system being further adapted to determine the patient's global end-diastolic blood volume (GEDV) and intrathoracic thermovolume (ITTV) from said thermodilution curve.the aforementioned computerized system being further adapted to determine the patient's intrathoracic blood volume (ITBV) according to the following formula: ITBV = f(GEDV, ITTV, P) ITBV being the intrathoracic blood volume, GEDV being the global end-diastolic blood volume, ITTV being the intrathoracic thermovolume, P being a ventilation channel pressure within the patient's lungs. To achieve the aforementioned objective, the invention also provides a computerized system comprising a first coupling means for coupling said computerized system to the temperature-influencing medium and a second coupling means for coupling said computerized system to a temperature-sensing device and optionally a third coupling means for coupling said computerized system to a ventilation duct pressure-sensing device, and evaluation means for evaluating executable instructions to make said computerized system control the A temperature-influencing medium is used to induce an initial local temperature change in the vicinity of a primary location in a patient's vascular system, thereby introducing a temperature shift in the patient's bloodstream. This local blood temperature is then recorded by a temperature sensor device. The patient's local blood temperature is measured at a secondary location in the patient's vascular system downstream of the primary location as a function of time to determine a thermodilution curve. The patient's global end-diastolic blood volume (GEDV) and intrathoracic thermovolume (ITTV) are then determined from the thermodilution curve, and the patient's intrathoracic blood volume (ITBV) is determined according to the following formula: ITBV = f(GEDV, ITTV, P), ITBV being the intrathoracic blood volume, GEDV being the global end-diastolic blood volume, ITTV being the intrathoracic thermovolume, P being a ventilation channel pressure within the patient's lungs. To achieve the aforementioned objective, the invention also provides a method for determining intrathoracic blood volume (ITBV) and other cardiovascular parameters of a patient by thermodilution measurements, comprising instructions executable by a computerized system to make said computerized system control the temperature-influencing medium to cause an initial local temperature change in the vicinity of a first location in a patient's vascular system, then introduce a temperature shift to the patient's bloodstream, to record said local blood temperature of the patient measured by a temperature sensor device to measure the local blood temperature of the patient at a second location in the patient's vascular system downstream of said first location as a function of time. To determine a thermodilution curve, to determine the patient's global end-diastolic blood volume (GEDV) and the patient's intrathoracic thermovolume (ITTV) from said thermodilution curve, to determine the patient's intrathoracic blood volume (ITBV) according to the following formula: ITBV = f(GEDV, ITTV, P), ITBV being the intrathoracic blood volume, GEDV being the global end-diastolic blood volume, ITTV being the intrathoracic thermovolume, P being a ventilation channel pressure within the patient's lungs. By determining intrathoracic blood volume not only as a function of total end-diastolic blood volume (TEBV) but also as a function of intrathoracic thermovolume, experience has shown that a better estimate of intrathoracic blood volume, and therefore also a better estimate of extravasated lung water, can be made. According to a preferred configuration of the invention, the aforementioned function f(GEDV, ITTV, P) is selected to be f(GEDV, ITTV, P) = a . GEDV + b + c . ITTV+d. P a being a species-dependent parameter, with 1 < a < 2, b being a species-dependent parameter, including zero, c being a species-dependent parameter, with ced being species-dependent parameters, including zero, with the limitation that ced cannot be zero simultaneously. The term c. ITTV provides a correction especially for high ITTV values, and the term d. P provides a correction for ITBV especially when the patient is mechanically ventilated. Once the species-specific parameters a, b, c, and d have been determined, applying the formula allows for an optimal match between the estimated values ​​of intrathoracic blood volume and extravasated lung water with values ​​precisely measured in a large patient population. In another preferred configuration of the aforementioned invention function f(GEDV, ITTV, P) is selected to be f(GED V, ITTV, P) -------------------------GEDV + b jiv ,r) (ITTV -GEDV) ! P C ^TTV norm -GEDV norm ) + P nom a, b, c and d being species-dependent parameters, with 1 < a / (c+d) < 2, where ITTV norm GEDV norm and P no rm are empirical normal values ​​of ITTV, GEDV, and P, respectively. The parameters a, b, c, and ed are determined by regression. In another preferred configuration of the invention, the aforementioned function f(GEDV, ITTV, P) is selected to be ITBV = a*GEDV (ITTV-GEDV) cl*---------------- (ITTV -GEDV) X norm norm / ^ + b + cl + 1 • J2»----+ 1 P I normal (ITTV -GEDV) „ P ------------------~—F «1 •---- (ITTV^-GEDV^) P„ om the parameters a, b, cl, dl, c2, d2 can be obtained by Nonlinear regression from dilution measures Double comparison. The parameters are dependent on species. The term a / ((c2+l)(d2+l)) is normally in range from 0.5 to 10. The first part ITBV = a* GEDV + b + cl* — (1TTV GEDV ^>— (ITTV mrm -GEDV nam ) + d\ norm describes the complete displacement of the thorax to the big circulation. Part two ITBV - a•GEDV (ITTV-GEDV c2 • +1 L UTTV norm -GEDV norm J • p 1 dZ*----+ 1 P norm describes the altered relationship between GEDV and PBV. Investigations have shown that the formula according to the ITBV of the previous technique, that is, the sum of PBV and GEDV, was underestimated at high ETV and high ventilation duct pressures. This is because a high ETV leads to lung tissue tension, which is disrupting the The normal fixed relationship between PBV and GEDV (ITBV = GEDV + PBV = a*GEDV + b). A similar result is achieved in high ventilation duct pressure (P). Thus, the effective pressure, which is pushing blood out of the lung, is the transmural pressure Ptm = ITP - Pmv. This is the difference between intrathoracic pressure and microvascular pressure. Peri-microvascular pressure could be disregarded. If the lung is very stiff, e.g., in fibrosis, even a high ventilation duct pressure has little influence – the intrathoracic pressure remains low. Most of the time, mean thoracic pressure (MTP) in the microvessels of the lung is not available. In this case, intrathoracic pressure or mean ventilation channel pressure could be used instead. Because PEEP (Positive End-Expiratory Pressure) is correlated, it could also be useful. Blood is displaced from the lungs in two ways. 1. The blood fraction is shifted from the lungs to the heart, thus altering the normal relationship between GEDV and PBV. 2. A portion of the PBV (pore-voiding bladder) is completely displaced from the thorax into the systemic circulation. Depending on the dominant factor cl, dl, or c2, d2 could be equal to zero. In a special case of humans, a = 1.48, b = 87 ml; cl = 0.18; dl = 0; c2 = 0; d2 = 0. There are also other possible formulas. In general, ITBV is a function of GEDV, ITTV, and P. It would also be advantageous to apply this to the intrathoracic blood volume index: ITBVI = ITBV / BSA, which is ITBV divided by Body Surface Area (BSA). In this case, ITBVI is a function of GEDV / BSA, TTV / BSA, and P. In another preferred embodiment of the invention, P is defined as equal to a transmural pressure Ptm of the lung, defined as Ptm = ITP - Pmv, ITP being an intrathoracic pressure and Pmv being a microvascular pressure. Since it is the transmural pressure that is... responsible for pulmonary vasoconstriction, which is the reason for an overestimation of intrathoracic blood volume and an underestimation of extravascular lung water, better results are obtained using transmural pressure to correct intrathoracic blood volume, even if the patient suffers from pulmonary fibrosis. However, transmural pressure is sometimes difficult to determine. Reasonably satisfactory results are also obtained using another configuration. using for P an average pressure measured in the ventilation channel of a mechanical ventilator or a positive end-expiratory pressure (PEEP) of a mechanical ventilator. These pressures can be easily determined. Additional advantageous configurations are described in sub-claims. The attached drawings serve to provide a better understanding of the above and other features of the invention. Brief description of the drawings Fig. 1 shows a schematic illustration explaining the dependencies between global end-diastolic volume (GEDV), lung blood volume (PBV), extra-thermal volume (ETV), ventilation channel volume (Vaw), and ventilation channel pressure (P). Fig. 2 shows a schematic sketch of both a patient's vascular system and a preferred configuration of a device according to the present invention. Fig. 3 shows a schematic example of a thermodilution curve in a diagram with the blood temperature difference as a function of time, where the abscissa is linear and the ordinate is logarithmic. Fig. 4 shows a block diagram illustrating the general hardware structure of a computerized system configuration according to the present invention, being part of the apparatus outlined in Fig. 2. Detailed description Figure 1 shows a schematic illustration explaining the dependencies between global diastolic volume (GEDV), which is roughly the blood located in the heart, pulmonary blood volume (PBV), which is the blood located in the lungs, extra thermal volume (ETV), which is roughly the water in the lungs outside the vessels, ventilation channel volume (Vaw), and ventilation channel pressure (P). Increasing the pressure (P) causes the ventilation channel volume (Vaw) to increase, which leads to a decrease in pulmonary blood volume (PBV); in other words, increasing P causes blood to flow out of the lungs into the heart and / or into the systemic circulation. Similarly, increasing ETV also causes blood to flow out of the lungs into the heart and / or into the systemic circulation. Fig. 2 illustrates the main components required to implement a configuration of an apparatus according to the invention and schematically shows the first and second locations 101, 102 of a patient's vascular system 103, where the apparatus interacts with the patient's vascular system 103. A computerized system 104, the general hardware structure of which is schematically illustrated in Fig. 4, is connected via port A 201 with a medical dosing device 105 serving together with a catheter 106 as an injection means 107 to inject into the first location 101, e.g., into the patient's superior vena cava, a bolus, e.g., 10 ml, or as a baseline, 0.15 ml / kg of the patient's body mass. The bolus, serving as a thermal indicator liquid, is substantially warmer or cooler than the patient's blood temperature.As a result, a traveling temperature deviation is introduced into the vascular system of patient 103, where it continuously changes according to boundary conditions. The temperature deviation passes through the right atrium and right ventricle 109 of patient 110's heart to . Entering the pulmonary circulation 111, where an extravascular thermovolume 112 may be present in the vicinity of the patient's vessels. The temperature deviation passes through the left atrium 113 and left ventricle 114 of the patient's heart to enter the aorta 115 into the systemic circulation 116. When the traveling temperature deviation reaches the second location 102, e.g., the patient's femoral artery, where the patient's blood temperature is continuously measured by a sensor device 117, which is connected to the computerized system 104 via port B 202, the traveling temperature deviation is recorded by the computerized system 104 as the Thermodilution Curve, i.e., temperature measured at the second location 102 as a function of time. From this Thermodilution Curve, the computerized system 104 determines an estimate of extravascular thermovolume according to the relationships explained above.Extravascular thermal volume correlates closely with the degree of extravascular lung water, provided there is no significant perforation defect in the lungs (e.g., pulmonary embolism). Figure 4 illustrates the general hardware structure of a computerized system configuration 104 according to the invention, suitable for being part of the apparatus shown in Figure 2. Via ports A and B 201, 202, which belong to an input / output subsystem, the computerized system 104 is connectable to the injection media sensor device 117 and pressure sensor 118, respectively. The input / output subsystem is controlled by a central processing unit (CPU) 204, which communicates via a data and address bus 205 with the other components of the computerized system 104, which include a timer 206 providing time signals from the timer to the CPU 204, a system memory (ROM) 207, in which the system software is permanently stored, and a data and instruction memory (RAM) 208, where both executable instructions and various data, including readings, are stored. Temperature readings for thermodilution curves and pressure readings for the ventilation channel can be stored; an input device controller 209 controlling an input device 210, such as a keyboard, a touch screen, or the like, to manually feed system parameters, operating settings, and the like; a disk subsystem 211 to read data or program instructions from a storage medium 212, such as a hard disk, floppy disk, compact disk, optical disk, or the like, and to store data to the storage medium 212; and a display subsystem 213 controlling a display 214 to display relevant information, such as the Thermodilution Curve or cardiovascular parameters determined by the computerized system 104. The pressure sensor device 118, which is adapted to measure the pressure in the patient's ventilation channel, is connected to the computerized system 104 via port 203. The apparatus described above is adapted to determine MTT, DST, CO from the thermodilution curve and to calculate parameters such as GEDV, ITBV and ETV.

Claims

CLAIMS 1. Apparatus for determining intrathoracic blood volume (ITBV) and other cardiovascular parameters of a patient by thermodilution measurements, characterized by comprising: a) temperature-influencing medium (107) to cause an initial local temperature change in the vicinity of a first place (101) in a patient's vascular system (103), thereby introducing a temperature shift traveling in the patient's bloodstream, b) a temperature sensor device (117) for measuring the local blood temperature of the patient in a second location (102) of the patient's vascular system (103) downstream of the aforementioned first location (101) c) a computerized system (104) coupled to the aforementioned temperature sensor device (117) and adapted to record the local blood temperature of the aforementioned patient measured in the aforementioned second location (102) as a function of time to determine a thermodilution curve, d) the aforementioned computerized system (104) being further adapted to determine the patient's global end-diastolic blood volume (GEDV) and intrathoracic thermovolume (ITTV) from the aforementioned thermodilution curve, (e) the aforementioned computerized system (104) being additionally adapted to determine the patient's intrathoracic blood volume (ITBV) according to the following formula: ITBV = f(GEDV, ITTV, P) ITBV being the intrathoracic blood volume, GEDV being the global end-diastolic blood volume, ITTV being the intrathoracic thermovolume, P being a ventilation channel pressure within the patient's lungs.

2. Device according to claim 1, characterized in that the cited function f(GEDV, ITTV, P) is selected to be f(GEDV, ITTV, P) = a. GEDV + b + c . ITTV+d. P a being a species-dependent parameter, with 1 < a < 2; b being a species-dependent parameter, including zero. c being a species-dependent parameter, with c < 0 d being a species-dependent parameter, including zero, with the restriction that ced cannot be zero simultaneously.

3. Device according to claim 1, characterized in that the cited function f(GEDV, ITTV, P) is selected to be / (G£Z>r, / 7Tr,P). —( / fr- - --—^-GEDV+b C (ITTV„-GEDV m ) + a, b, c, and d being species-dependent parameters, with 1 < a / (c + d) < 2, where ITTVnorm, GEDVnorm, and Pnorm are empirical normal values ​​of ITTV, GEDV, and P, respectively.

4. Device according to claim 1, characterized in that the cited function f(GEDV, ITTV, P) is selected to be ITBV = a» GEDV • ( ITTV - GEDV ) + j" (ITTV -GEDV ) L ' norm norm VJ • dl» — + 1 P _ norm , , (ITTV-GEDV) P 4- b+cl •--l- dl»----- (ITTV -GEDV) P norm norm / norm a, b, cl, c2, dl, d2 being species-dependent parameters, with 0.5 < a / (c2 + 1)(d2 + 1) < 10, where ITTVnorm, GEDVnorm and Pnorm are empirical normal values ​​of ITTV, GEDV and P, respectively.

5. Apparatus, according to any of the preceding claims, characterized in that P is defined as a transmural lung pressure Ptm, being defined as Ptm = ITP - Pmv, ITP being intrathoracic pressure and Pmv being microvascular pressure.

6. Apparatus, according to any of the preceding claims, characterized in that P 7. Apparatus, according to claim 6, characterized in that P is a positive end-expiratory pressure (PEEP).

8. Apparatus, according to claim 7, characterized in that P is a mean ventilation channel pressure.

9. Apparatus, according to any of the previous claims, characterized by the fact that it is adapted to determine at least one of the aforementioned cardiovascular parameters by transpulmonary thermodilution.

10. Apparatus, according to any of the preceding claims, characterized in that it is adapted to determine an estimate of extravascular lung water (EVLW) as EVLW = ITTV - ITBV, EVLW being extravascular lung water.

11. Apparatus, according to any of the preceding claims, characterized in that it is adapted to determine ITTV as ITTV = CO . MTT, CO being total cardiac volume and MTT being the mean transit time, indicating the time required by the aforementioned temperature deviation to travel from the aforementioned first place (101) to the aforementioned second place (102).

12. Apparatus, according to any of the preceding claims, characterized in that it is adapted to determine GEDV as GEDV = CO . (MTT - DST), CO being the total cardiac volume and MTT being the mean transit time, indicating the time required by the aforementioned temperature deviation to travel from the aforementioned first place (101) to the aforementioned second place (102) and DST being a downward slope time of the aforementioned thermodilution curve.

13. Apparatus, according to any of the preceding claims, characterized in that it further comprises a pressure sensing device (118) coupled to said computerized system (104).

14. Computerized system, characterized by comprising a first coupling means for coupling said computerized system (104) to a temperature-influencing medium (107) and a second coupling means for coupling said computerized system (104) to a temperature-sensing device (117), and access means for accessing executable instructions to operate said computerized system (104) a) controlling the temperature-influencing medium (107) to cause an initial temperature change in the vicinity of a first place (101) in a patient's vascular system (103), thereby introducing a traveling temperature shift into the patient's bloodstream, b) to record the said local blood temperature measured by a temperature sensor device (117), to measure the patient's local blood temperature at a second location (102) in the patient's vascular system (103) downstream of the said first location (101) as a function of time to determine a thermodilution curve, c) determine the patient's total end-diastolic blood volume (TEBV) and intrathoracic thermovolume (ITTV) from the aforementioned thermodilution curve, e) Determine the patient's intrathoracic blood volume (ITBV) according to the following formula: ITBV = f(GEDV, ITTV, P), ITBV being the intrathoracic blood volume, GEDV being the global end-diastolic blood volume, ITTV being the intrathoracic thermovolume, and P being a channel pressure. ventilation within the patient's lungs.

15. Computerized system, according to claim 14, characterized in that the aforementioned function f(GEDV, ITTV, P) is selected to be f(GEDV, ITTV, P) = a . GEDV + b + C . ITTV+d. P a being a species-dependent parameter, with 1 < a < 2 b being a species-dependent parameter, including zero c being a species-dependent parameter, with c < 0 d being a species-dependent parameter, including zero, with the restriction that ced cannot be zero simultaneously.

16. Computerized system, according to claim 14, characterized in that the cited function f(GEDV, ITTV, P) is selected to be f (GEDV, ITTV, P) = (ITTV-GEDV) P (ITTV norm - GED V norm P norm GEDV + b a, b, c, and d being species-dependent parameters, with 1 < a / (c + d) < 2, where ITTVnorm, GEDVnorm, and Pnorm are empirical normal values ​​of ITTV, GEDV, and P, respectively.

17. Computerized system, according to claim 14, characterized in that the aforementioned function f(GEDV, ITTV, P) is selected to be ITBV = a* GEDV (ITTV-GEDV) --1-1 (ITTV -GEDV )\norm nQrm 7 • p J2.----+ 1 P norm _ + 6 + cl» (ITTV-GEDV) * P (ITTV -GEDV ) P V norm norm V norm a, b, cl, c2, dl being species-dependent parameters, with 0.5 < a / (c2 + 1) (d2 + 1) < 10, where ITTVnorm, GEDVnorm and Pnorm are empirical normal values ​​of ITTV, GEDV and P, respectively.

18. Computerized system, according to any of the preceding claims, characterized in that To understand a port coupled to a pressure sensor arranged in the ventilation channel of a mechanical respirator.

19. A computerized system, according to any of the preceding claims, characterized in that it is prompted to determine an estimate of extravascular lung water (EVLW) as EVLW - ITTV - ITBV, EVLW being the extravascular lung water.

20. Computerized system, according to any of the preceding claims, characterized in that it is caused to determine the aforementioned ITTV as ITTV = CO . MTT, CO being the total cardiac volume and MTT being the mean transit time, indicating the time for the said temperature deviation to travel from the said first place (101) to the said second place (102).

21. Computerized system, according to any of the preceding claims, characterized in that it is prompted to determine the aforementioned GEDV as GEDV = CO . (MTT - DST), CO being the total cardiac volume and MTT being the mean transit time, indicating the time required by the aforementioned temperature deviation to travel from the aforementioned first place (101) to the aforementioned second place (102) and DST being a downward slope time of the aforementioned thermodilution curve.

22. Method for determining intrathoracic blood volume (ITBV) and other cardiovascular parameters of a patient by thermodilution measurements, characterized in that it comprises instructions executable by a computerized system (104) to make said computerized system (104) a) controlling the temperature-influencing medium (107) to cause a local temperature change in the vicinity of a first place (101) in a patient's vascular system (103), thereby introducing a temperature deviation traveling in the patient's bloodstream, b) record the said local blood temperature of the patient measured by a temperature sensor device (117) to measure the local blood temperature of the patient at a second location (102) of the patient's vascular system (103) downstream of said first location (101) as a function of time to determine a thermodilution curve, c) determine the patient's total end-diastolic blood volume (TEBV) and intrathoracic thermovolume (ITTV) from the aforementioned thermodilution curve, e) Determine the patient's intrathoracic blood volume (ITBV) according to the following formula: ITBV = f(GEDV, ITTV, P), ITBV being the intrathoracic blood volume, GEDV being the global end-diastolic blood volume, ITTV being the intrathoracic thermovolume, P being a ventilation channel pressure within the patient's lungs.

23. Method, according to claim 22, characterized in that the aforementioned function f(GEDV, ITTV, P) is selected to be f(GEDV, ITTV, P) = a . GEDV + b + c . ITTV+d. P a being a species-dependent parameter, with 1 < a < 2; b being a species-dependent parameter, including zero. c being a species-dependent parameter, with c < 0 d being a species-dependent parameter, including zero, with the restriction that ced cannot be zero. simultaneously.

24. Method according to claim 22, characterized by the fact that the aforementioned function f(GEDV, ITTV, P) is selected to be f (GEDV,ITTV, P) = (ITTV-GEDV) !d C UTTV norm -GEDV norm ) + norm GEDV + b a, b, ced being species-dependent parameters, with 1 < a / (c + d) < 2, where ITTVnorm, GEDVnorm and Pnorm are empirical normal values ​​of ITTV, GEDV and P, respectively.

25. Method, according to claim 22, characterized in that the cited function f(GEDV, ITTV, P) is selected to be ITBV = ___________g»GEDV__________ e2. (ITTV-GEDV) (ITTV -GEDV) P norm norm / J |_ norm (ITTV-GEDV) „ P + b + cl •--1 - dl •--- (ITTV -GEDV) P V norm norm r non a, b, cl, c2, dl, d2 being species-dependent parameters, with 0.5 < a / (c2 +1) (d2 +1) < 10, where ITTVnorm, GEDVnorm and Pnorm are empirical normal values ​​of ITTV, GEDV and P, respectively.

26. Method, according to any of the preceding claims, characterized in that the aforementioned computerized system (104) determines an estimate of extravascular lung water (EVLW) as EVLW = ITTV - ITBV, EVLW being the extravascular lung water.

27. Method, according to any of the preceding claims, characterized in that it makes the aforementioned computerized system (104) determine ITTV as ITTV = CO . MTT, CO being the total cardiac volume and MTT being the mean transit time, indicating the time required by the aforementioned temperature deviation to travel from the aforementioned first place (101) to the aforementioned second place (102).

28. Method, according to any of the preceding claims, characterized in that it makes the aforementioned computerized program (104) determine GEDV as GEDV = CO . (MTT - DST), CO₂ being the total cardiac volume and MTT being the mean transit time, indicating the time required by the aforementioned temperature deviation to travel from the cited first place (101) to cited second place (102) and DST being a downward slope time of the cited thermodilution curve.

29. Storage medium, characterized in that it physically stores a computer program for executing a method as claimed in any of the preceding claims.