DE102020129899A1 - Medical system for determining a cardiac output-dependent parameter - Google Patents

Abstract

The invention relates to a medical system (100) for determining a cardiac output-dependent parameter (107) of a patient (102) to be treated, having a respiratory gas analysis unit (110), a first and second sensor unit (120, 130) and an evaluation unit (140). The respiratory gas analysis unit is designed to determine and provide a respiratory gas analysis variable (142) indicative of the oxygen uptake from a respiratory gas signal (112), which indicates at least one measured variable relating to the respiratory gas of the patient. The first sensor unit is designed to measure and output a first measured variable (144) indicative of arterial oxygen saturation, and the second sensor unit is designed to measure and output a second measured variable (146) indicative of venous oxygen saturation. Finally, the evaluation unit is designed to calculate and output an output value (148) for the cardiac output-dependent parameter based on the respiratory gas analysis variable, on the first measured variable and on the second measured variable.

Description

The invention relates to a medical system for determining a cardiac output-dependent parameter of a patient to be treated. Furthermore, the invention relates to a ventilation system for ventilation of a patient to be treated and a method for determining a cardiac output-dependent parameter of a patient to be treated.

Cardiac output is a central hemodynamic parameter for recording a patient's condition in intensive care. The cardiac output includes the entire blood volume flow of the patient. By recording the cardiac output, states of shock, for example, can be correctly classified quickly and appropriate therapy can then be initiated. Furthermore, by taking this parameter into account, the anesthesia and the intensive ventilation of a patient can be improved, as is known. In principle, the clinical detection of the global blood volume flow is used, as is known, to monitor adequate blood flow through the brain and the internal organs of the patient and thus their adequate supply.

A widely used reference method for measuring cardiac output is thermodilution measurement with a pulmonary artery catheter, which has to be invasively inserted into the patient.

It is also known that the cardiac output or parameters corresponding thereto can be continuously estimated based on an invasive or non-invasive course of the arterial blood pressure. In this case, for example, a time interval defined by the systole of a blood pressure pulse is used as a central parameter in order to obtain the most reliable possible estimate of the cardiac output from the properties of the pressure profile within this time interval.

The object of the present invention is to provide an improved medical system, in particular a medical system with a continuous and particularly precise determination of a cardiac output-dependent parameter.

According to a first aspect of the invention, a medical system for determining a cardiac output-dependent parameter of a patient to be treated is proposed for solving this problem, with a respiratory gas analysis unit, a first sensor unit, a second sensor unit and an evaluation unit.

The respiratory gas analysis unit is designed to determine and provide a respiratory gas analysis variable indicative of the oxygen uptake, in particular a respiratory gas analysis variable indicative of the oxygen concentration and/or a carbon dioxide concentration, from a respiratory gas signal that indicates at least one measured variable relating to the respiratory gas of the patient.

The first sensor unit is designed to measure a first measured variable indicative of the arterial oxygen saturation, in particular to measure the arterial oxygen saturation, and to output a corresponding first sensor signal.

The second sensor unit is designed to measure a second measured variable indicative of the venous oxygen saturation, in particular to measure the mixed venous oxygen saturation, and to output a corresponding second sensor signal.

The evaluation unit is designed to receive the first and second sensor signals and to calculate and output an output value for the cardiac output-dependent parameter based on the respiratory gas analysis variable, the first measured variable and the second measured variable.

As part of the invention, it was recognized that fundamentally known individual components, such as a unit for determining oxygen uptake, a sensor for determining arterial oxygen saturation and a sensor for determining venous oxygen saturation, can be used to clinically relevant variables such as cardiac output -dependent parameters to determine. For this purpose, a networking of these known individual components to form the medical system according to the invention is proposed, which enables the proposed offsetting of the variables determined.

As a result, a particularly current output value for the cardiac output-dependent parameter can advantageously be output, since this parameter results from continuously measurable variables. As a result, the medical system according to the invention enables clinical staff to record the current condition of a patient with particular precision. In particular, according to the invention, it is not necessary to resort to individually estimated and/or globally specified values in order to determine the cardiac output-dependent parameter.

Furthermore, the medical system according to the invention can be integrated particularly easily into existing treatment systems for treating patients, since there is no new type of hardware components are required for the implementation of this medical system.

The medical system according to the invention also advantageously allows the cardiac output-dependent parameter to be calculated and output particularly quickly, since after receiving both measured variables and the respiratory gas analysis variable, only one calculation must be carried out in accordance with a predetermined calculation rule in order to determine the cardiac output-dependent parameter . The calculation rule is preferably based on the well-known Fick's principle. Since the sensor units can measure and output the corresponding variables to the evaluation unit in real time or essentially in real time, the processing carried out by the medical system according to the invention can also be carried out in real time or essentially in real time. In particular, there can be a time of less than 10 seconds, in particular less than 5 seconds, preferably less than 2 seconds, between the acquisition of the corresponding measured variables and the output of the cardiac output-dependent parameter.

The respiratory gas analysis unit can be integrated into a medical device, such as a respirator, an anesthetic device and/or a medical analysis device, or it can be present as a separate device.

The cardiac output-dependent parameter can be, for example, the stroke index, the cardiac index, the stroke volume and/or the cardiac output of the patient or a cerebral part of such a parameter. These cardiac output-dependent parameters are particularly relevant parameters for evaluating the current condition of the patient. These parameters are common medical parameters whose medical relevance is immediately apparent to a person skilled in the art. The beat index of the heart is the stroke volume per square meter of the patient's body surface. Furthermore, the cardiac index is the cardiac output per square meter of the patient's body area. Cardiac output is the amount of blood that the heart pumps into the patient's body in a given amount of time, such as one minute. Stroke volume is the amount of blood that the heart pumps into the patient's body in one heartbeat. To this extent, these variables are correlated with the cardiac output and are therefore cardiac output-dependent parameters.

In order to determine the cerebral blood flow, ie a cerebral portion of an examined blood volume flow, the arterial oxygen saturation is determined according to the invention in the area of the cerebral supply. A corresponding measurement is possible, for example, via an invasive blood pressure measurement in the carotid artery or via an optical measurement on the neck and/or above the neck on the patient's head. In this respect, the medical system according to the invention also allows the advantageous measurement of the cerebral blood flow in addition to the continuous measurement of the cardiac output.

The various units of the medical system according to the invention can be arranged in a common housing or can be arranged at least partially at a distance from one another. Several units, such as the respiratory gas analysis unit and the evaluation unit, can be controlled by a common processor. The units of the medical system are separated from one another at least at the software level.

The medical system according to the invention can be at least partially a component of a medical device to be used in intensive care, such as a ventilator. Within the scope of this invention, an anesthetic device and a breath analysis device are also ventilators, since they relate to the ventilation of a patient.

Preferred embodiments of the medical system according to the invention are described below.

In a particularly preferred embodiment, the at least one measured variable relating to the patient's breathing gas relates to an oxygen concentration of the expiratory gas flow. The corresponding measured variable is preferably the oxygen concentration of the expiratory gas flow. This variable is typically determined by a ventilator and/or an anesthesia machine in order to implement device-internal controls, such as a gas flow. The use of such a variable within the scope of the medical system according to the invention is advantageous because no additional sensors are required to measure this measured variable. In an alternative or supplementary embodiment to this, the at least one measured variable relating to the patient's breathing gas relates to a carbon dioxide concentration, in particular a carbon dioxide concentration of the expiratory gas flow. The corresponding measured variable is preferably the carbon dioxide concentration of the expiratory gas flow. It is known that carbon dioxide release and oxygen uptake in a patient are closely linked as long as there is no physical exertion. The oxygen uptake can therefore advantageously be estimated on the basis of a carbon dioxide release. The required measurement of a Koh lendioxid concentration can be done, for example, via capnometry.

In a further advantageous embodiment, the evaluation unit is designed to calculate the arterial oxygen content from the first measured variable, to calculate the mixed venous oxygen content from the second measured variable and to determine the output value based on the arterial oxygen content and the mixed venous oxygen content. The conversion between the corresponding oxygen saturation and the present oxygen content preferably takes into account an offset between the oxygen saturation at the location where the corresponding sensor unit measures the respective measured variable, such as on the patient's neck, and the corresponding oxygen saturation in the region of the heart. Such a conversion is advantageous since the cardiac output or another cardiac output-dependent parameter can be calculated directly from the difference between the mixed venous oxygen content and the arterial oxygen content via the oxygen uptake. For example, a quotient of oxygen uptake and this difference gives the cardiac output.

In a particularly preferred embodiment, the first sensor unit and/or the second sensor unit is designed to non-invasively determine the corresponding measured variable via an optical measurement. Such an optical measurement can be carried out, for example, using a plethysmographic or pulse oximetry method and/or using near-infrared spectroscopy. Such a measurement of the arterial blood oxygen saturation is already known in the clinical environment. In this embodiment, the cardiac output-dependent parameter is particularly advantageously determined non-invasively. As a result, a particularly low level of physical stress on the patient to be treated is possible. Furthermore, a continuous monitoring of the patient to be treated is thereby possible, without a complex treatment of the patient being necessary for arranging the components of the measuring system.

In a further advantageous embodiment, at least the respiratory gas analysis unit and the evaluation unit are arranged in a common housing. As a result, the medical system according to the invention can be designed to be particularly robust. The common housing can, for example, protect the components contained therein from external influences and environmental influences. In an advantageous variant of this embodiment, the two sensor units are at least partially disposable products that are no longer used after they have been used on the patient once. In particular, the parts of the sensor unit that are in contact with the patient are preferably disposable components that are replaced after a single use. At least those parts of the two sensor units that are not single-use components are preferably also contained in the common housing of the respiratory gas analysis unit and evaluation unit. In this preferred example, the medical system according to the invention is particularly easy to transport and can therefore be used quickly to treat a patient.

In a further embodiment, the respiratory gas analysis unit, the first and second sensor unit and the evaluation unit for providing a mobile transport state of the medical system can be arranged in and/or on a common housing of the medical system. In this embodiment, the entire medical system can be transferred to the mobile transport state and can therefore be transported in a particularly simple and robust manner. The common housing preferably has a handle area, by means of which the medical system can be carried, pushed, pulled or moved in a similar manner.

In a further advantageous embodiment, the first sensor unit and/or the second sensor unit is formed by a sensor patch that communicates wirelessly with the evaluation unit. In this embodiment, at least one of the two transmitter units can be arranged on the patient in a particularly simple manner and allows for a particularly high level of wearing comfort, since one does not have to watch out for possibly interfering cables. Such sensor patches for measuring arterial and/or venous oxygen saturation are known and are therefore not described in detail below. Such a sensor patch can consist at least partially of a single-use component that has to be replaced after it has been used once on a patient. Such wireless communication can take place, for example, by means of BLE, Bluetooth, WLAN or ZigBee communication.

According to a second aspect of the invention, a ventilation system for the ventilation of a patient to be treated is proposed to solve the above-mentioned problem. The ventilator system comprises a ventilator, in particular an anesthesia machine, and a medical system according to at least one of the preceding embodiments, the ventilator being designed to provide the respiratory gas signal for the respiratory gas analysis unit.

The ventilation system according to the invention includes the medical system according to the first aspect of the invention and thus also has all the advantages of this medical system. Also allowed the combined provision of respiratory gas signal and medical system that the respiratory gas signal is provided for the corresponding interface of the respiratory gas analysis unit and is adapted for reception by this interface.

A ventilator within the meaning of this invention is also to be understood as meaning an anesthesia machine and also a breath analysis machine, since these are used in the context of ventilating a patient.

The respiratory gas analysis unit of the medical system according to the invention is preferably arranged in a housing of the ventilator. As a result, the respiratory gas analysis variable that indicates the oxygen uptake can be arranged directly in spatial proximity to the sensor system relevant for this. In this way, for example, a parameter set-up can additionally be sent with the respiratory gas signal, which is used for reading out the oxygen uptake or the respiratory gas analysis variable indicating the oxygen uptake by the respiratory gas analysis unit. In addition, the oxygen uptake or the corresponding respiratory gas analysis variable can also be used for other clinically relevant analysis methods that take place outside of the described medical system according to the invention. In this sense, the respiratory gas analysis unit can also be connected to other external devices in addition to the evaluation unit.

In a particularly advantageous embodiment, a control unit of the ventilation system, in particular a control unit of the ventilator, is designed to receive the output value for the cardiac output-dependent parameter and, based on this output value, to control a medication dosage for dispensing a medicament into a respiratory gas circuit of the ventilator. The release control can be based on a pharmacodynamic and/or a pharmacokinetic model for the effect of this drug. In this embodiment, the medical system according to the invention enables the medication treatment of the patient to be automated in a particularly advantageous manner. Here, current changes in the corresponding patient condition can be taken into account particularly quickly, so that the medication delivery is improved compared to a manual setting.

In a further particularly advantageous embodiment, a control unit of the ventilation system, in particular of the ventilator, is designed to receive the output value for the cardiac output-dependent parameter and, based on this output value, a ventilation parameter, in particular the positive end-expiratory pressure, for the ventilation of the currently adapt to the patient being treated. In this embodiment, the output value is used particularly advantageously in order to automatically influence the treatment of the patient. In particular, the adaptation of the ventilation parameter based on the current output value allows the current patient condition to be taken into account particularly quickly when the ventilation parameter is set. As a result, fewer manual device settings and physician decisions are required for the treatment of the patient. The rapid adjustment of the ventilation parameters based on current measured values also ensures that a sudden change in the patient's condition is taken into account when the patient is ventilated.

• - Empfangen eines Atemgas-Signals, das mindestens eine das Atemgas des Patienten betreffende Messgröße indiziert;
• - Bestimmen und Bereitstellen einer die Sauerstoffaufnahme indizierende Atemgas-Analysegröße basierend auf dem Atemgas-Signal;
• - Messen einer die arterielle Sauerstoffsättigung indizierenden ersten Messgröße und Ausgeben eines entsprechenden ersten Sensorsignals;
• - Messen einer die venöse Sauerstoffsättigung indizierenden zweiten Messgröße und Ausgeben eines entsprechenden zweiten Sensorsignals;
• - Empfangen des ersten und zweiten Sensorsignals;
• - Berechnen und Ausgeben eines Ausgabewerts für den Herzzeitvolumen-abhängigen Parameter basierend auf der Atemgas-Analysegröße, auf der ersten Messgröße und auf der zweiten Messgröße.

According to a third aspect of the invention, a method for determining a cardiac output-dependent parameter of a patient to be treated is proposed to solve the above-mentioned problem, having the steps:

• - Receiving a respiratory gas signal which indicates at least one measured variable relating to the patient's respiratory gas;
• - Determining and providing an oxygen uptake indicative respiratory gas analysis variable based on the respiratory gas signal;
• - measuring a first measured variable indicative of the arterial oxygen saturation and outputting a corresponding first sensor signal;
• - measuring a second measured variable indicative of the venous oxygen saturation and outputting a corresponding second sensor signal;
• - receiving the first and second sensor signals;
• - Calculating and outputting an output value for the cardiac output-dependent parameter based on the respiratory gas analysis variable, on the first measured variable and on the second measured variable.

The method according to the invention is carried out by the medical system according to the first aspect of the invention and has all the advantages of this medical system. In particular, the combined evaluation of the respiratory gas analysis variable and the two measured variables allows the cardiac output or another cardiac output-dependent parameter to be determined continuously and particularly quickly within the scope of this method.

The steps of the procedure can be carried out in different orders. Thus, the measurement of the two measured variables and the determination of the respiratory gas analysis variable can take place in any order. Only the calculation and output of the output value preferably takes place as the last step of the method according to the invention.

All steps of the method according to the invention are preferably carried out in real time or essentially in real time. Preferably less than 10 seconds, in particular less than 5 seconds, particularly preferably less than 2 seconds elapse between the receipt of the respiratory gas signal and the output of the output value for the cardiac output-dependent parameter.

In a particularly preferred embodiment, the method according to the invention additionally includes using the output value for further treatment of the patient, such as for adjusting a ventilation parameter and/or for controlling a drug dosage for dispensing a drug to a breathing circuit for ventilation of the patient. Such further use of the output value is particularly advantageous if the method steps are carried out in real time or essentially in real time, at least preferably in less than 10 seconds, in particular in less than 5 seconds, particularly preferably in less than 2 seconds.

• 1 eine schematische Darstellung eines ersten Ausführungsbeispiels eines Medizinsystems gemäß einem ersten Aspekt der Erfindung;
• 2 eine schematische Darstellung eines zweiten Ausführungsbeispiels des Medizinsystems gemäß dem ersten Aspekt der Erfindung;
• 3 eine schematische Darstellung eines dritten Ausführungsbeispiels des Medizinsystems gemäß dem ersten Aspekt der Erfindung;
• 4 eine schematische Darstellung eines ersten Ausführungsbeispiels eines Beatmungssystems gemäß einem zweiten Aspekt der Erfindung;
• 5 eine schematische Darstellung eines zweiten Ausführungsbeispiels des Beatmungssystems gemäß dem zweiten Aspekt der Erfindung;
• 6 eine schematische Darstellung eines dritten Ausführungsbeispiels des Beatmungssystems gemäß dem zweiten Aspekt der Erfindung;
• 7 ein Flussdiagramm eines Ausführungsbeispiels eines Verfahrens gemäß einem dritten Aspekt der Erfindung.

The invention will now be explained in more detail with reference to advantageous exemplary embodiments that are shown schematically in the figures. Of these show in detail:

• 1 a schematic representation of a first embodiment of a medical system according to a first aspect of the invention;
• 2 a schematic representation of a second embodiment of the medical system according to the first aspect of the invention;
• 3 a schematic representation of a third embodiment of the medical system according to the first aspect of the invention;
• 4 a schematic representation of a first embodiment of a ventilation system according to a second aspect of the invention;
• 5 a schematic representation of a second embodiment of the ventilation system according to the second aspect of the invention;
• 6 a schematic representation of a third embodiment of the ventilation system according to the second aspect of the invention;
• 7 a flow chart of an embodiment of a method according to a third aspect of the invention.

1 shows a schematic representation of a first embodiment of a medical system 100 according to a first aspect of the invention.

The medical system 100 is designed to determine a cardiac output-dependent parameter 107 of a patient 102 to be treated. For this purpose it has a respiratory gas analysis unit 110 , a first sensor unit 120 , a second sensor unit 130 and an evaluation unit 140 .

The respiratory gas analysis unit 110 is designed to determine and provide a respiratory gas analysis variable 142 indicative of the oxygen uptake from a respiratory gas signal 112 that indicates at least one measured variable relating to the respiratory gas of the patient 102 . In the exemplary embodiment shown, respiratory gas analysis variable 142 is output to evaluation unit 140 via an analysis signal 114 . The output takes place via communication with the evaluation unit 140, which in the present case takes place on a cable basis. In an exemplary embodiment that is not shown, this communication takes place wirelessly. The respiratory gas analysis variable 142 that indicates the oxygen uptake is the oxygen uptake in the present case. This is measured by measuring the oxygen concentration of the expiratory gas flow while the patient 102 is being ventilated. In the present case, this oxygen concentration is the measured variable relating to the respiratory gas of the patient 102 . The measurement of the oxygen uptake during ventilation of a patient is known, so that the physiological background and a possible procedure are not explained in detail below. In the present case, the respiratory gas analysis unit 110 is arranged in an external medical device 115 . In this case, this external medical device is a ventilator. In an exemplary embodiment that is not shown, the respiratory gas analysis unit is a separate unit that has a separate housing. In a further exemplary embodiment, the respiratory gas analysis unit is in a common housing with at least one further component of the medical system according to the invention.

The first sensor unit 120 is designed to measure a first measured variable 144 indicative of the arterial oxygen saturation and to output a corresponding first sensor signal 122 . The second sensor unit 130 is formed, the to measure venous oxygen saturation indicative second measured variable 146 and to output a corresponding second sensor signal 132. In the present case, the second measured variable 146 is the venous oxygen saturation. This is preferably measured using the blood in the so-called vena jugularis, which is located on the neck of the patient 102 . The first measured variable 144 is preferably the arterial oxygen saturation, which can be measured, for example, in the area of an extremity of the patient 102, such as on the wrist. The communication of the two sensor signals 122, 132 is cable-based in the illustrated embodiment. As shown in the further exemplary embodiment, this communication can also take place wirelessly.

Evaluation unit 140 is designed to receive first and second sensor signals 122, 132 and to calculate and output an output value 148 for cardiac output-dependent parameter 107 based on respiratory gas analysis variable 142, first measured variable 144 and second measured variable 146 . The output takes place via the output signal 149.

The output value 148 is calculated using a predetermined calculation rule 147, which is stored in the evaluation unit 140, in particular is stored permanently.

In the present case, the cardiac output-dependent parameter 107 is the cardiac output of the patient 102. Alternatively or additionally, the cardiac output-dependent parameter 107 can be the stroke index, the cardiac index and/or the stroke volume of the patient 102.

In the present case, the calculation rule 147 is a multi-step calculation rule in which, in a first step, the arterial oxygen content is calculated from the first measured variable 144 and the mixed venous oxygen content is calculated from the second measured variable 146 . In the context of this invention, the mixed venous oxygen content and the mixed venous oxygen saturation are also a venous oxygen content and a venous oxygen saturation, since the mixed venous variables result physiologically from a combination of different venous variables. For example, the mixed-venous variables in the arteria pulmonalis are measured, in particular measured via a pulmonary artery catheter. If the measurement is carried out via a blood gas analysis, it is preferably measured in the vena cava, preferably via a venous catheter, which also allows a continuous measurement according to the invention, for example via a fiber optic. In this case one speaks of a central venous measurement. In a variant of the exemplary embodiment described, the mixed venous oxygen content C _vO is calculated _{2 ,est} depends on the mixed venous oxygen saturation S _vjO measured via the second sensor unit 130 ₂ as follows: $$C_{v{O}_2,est}=S_{vj{O}_2}\cdot \left(1+\mathrm{\Delta }\right)\cdot 1.34\cdot \text{hb}$$

Here it is assumed that the mixed venous oxygen content in front of the right heart is lower by a specific factor than the venous oxygen content measured in the neck. For example, a clinically used value for Δ is 0.39. The physically dissolved oxygen is usually neglected for the calculation, since it has only an insignificant effect on the level of the oxygen content. In addition, this calculation takes into account the hemoglobin concentration Hb, which is also made available to the evaluation unit. Alternatively, it can be assumed, for example, that the conversion described takes place as follows: $$C_{v{O}_2,est}=\left(S_{vj{O}_2}+\mathrm{\Delta }\right)\cdot 1.34\cdot \text{hb}$$

Here it is assumed that the mixed venous oxygen saturation is shifted by a fixed value compared to the venous oxygen saturation measured at the neck.

The factor in front of the hemoglobin concentration is preferably 1.36 in the case of a mixed venous measurement.

Analogously to the calculation described, the arterial oxygen saturation is converted into the arterial oxygen content.

The conversion of oxygen uptake according to the respiratory gas analysis variable 142, arterial oxygen content and mixed-venous oxygen content to the output value 148 for the cardiac output-dependent parameter 107 is carried out using the known relation that the cardiac output is approximately the quotient of oxygen uptake and the difference between arterial and mixed-venous oxygen content is equivalent to.

This results in the second step of the calculation rule 140 corresponding to the exemplary embodiment shown.

In other exemplary embodiments, the measured variables and the respiratory gas analysis variable are evaluated differently in order to calculate the output value sought. In this sense, the calculation method shown is not restrictive for the implementation of the solution according to the invention.

In an exemplary embodiment that is not shown, the medical system also includes a third sensor unit that is designed to measure and provide the current value for the hemoglobin concentration Hb. Alternatively, a permanently specified value can be stored in the medical system as the hemoglobin concentration. Finally, the hemoglobin concentration can be determined using an external device and output to the medical system. In a further exemplary embodiment, the calculation of the cardiac output-dependent parameter is not dependent on the hemoglobin concentration.

The various units of the medical system 100 according to the invention can be arranged in a common housing or at least partially arranged separately from one another. The various units can communicate with each other via cables or wirelessly. A cable-based communication can take place, for example, via a BUS system, an Ethernet interface, a USB interface or the like. Wireless communication can take place, for example, via a Bluetooth interface, a WLAN interface, a BLE interface, a ZigBee interface or the like.

2 shows a schematic representation of a second exemplary embodiment of the medical system 200 according to the first aspect of the invention.

The medical system 200 differs from that in 1 illustrated medical system 100, the evaluation unit 240 is arranged together with the respiratory gas analysis unit 210 in a common housing 216. The device with the housing 216 has both a respiratory gas signal interface 217, via which it receives the respiratory gas signal 112, and a measurement signal interface 218, via which it receives the two measurement signals 122, 132. In the exemplary embodiment shown, the output value 148 is output via the output signal 149 in a cable-based manner to an external device (not shown). The external device can be, for example, an output device with an optical output, for example a display, via which a progression and/or a current value of the cardiac output-dependent parameter is shown.

Furthermore, in the exemplary embodiment shown, the first sensor unit 220 and the second sensor unit 230 are in the form of sensor patches which are connected wirelessly to the evaluation unit 240 . The sensor patches 220, 230 each have a disposable part 224, 234 to be attached to the patient and a respective sensor part 226, 236 attached thereto. The sensory part has the interface for wireless communication with the evaluation unit 240 in each case.

The two sensor units 220, 230 are designed for the non-invasive determination of the measured variable indicative of the respective oxygen saturation. In particular, both are designed to optically measure the respective measured variable. This can be done, for example, using a known plethysmographic or pulse oximetry method.

3 shows a schematic representation of a third exemplary embodiment of the medical system 300 according to the first aspect of the invention.

The medical system 300 differs from that in 2 illustrated medical system 200 that the housing 316 is designed such that the respiratory gas analysis unit 210, the first and the second sensor unit 220, 230 and the evaluation unit 240 can be arranged in or on this housing 316. For this purpose, the housing 316 has a first receptacle 328 for the first sensor unit 220 and a second receptacle 338 for the second sensor unit 230. Due to the wireless connection of the two sensor units to the evaluation unit 240, a system for cable management can be dispensed with. Finally, the housing 316 has a handle 318 for carrying the medical system 300 . This allows the medical system according to the invention to be transported particularly easily.

In an exemplary embodiment that is not shown, at least one of the two sensor units is connected to the evaluation unit via a cable. In this exemplary embodiment, a cable receptacle for inserting the corresponding cable between the evaluation unit and the corresponding sensor unit is provided on the housing.

4 shows a schematic representation of a first embodiment of a ventilation system 405 according to a second aspect of the invention.

The ventilator system 405 has the medical system 400 according to the first aspect of the invention and an additional ventilator 450 . The ventilator 450 is designed to output the respiratory gas signal 112 to the respiratory gas analysis unit 410 . In addition, the ventilator 450 has a tube system 460 which is connected to the patient 102 via a Y-piece 462 .

The only difference between the medical system 400 and the in 1 illustrated medical system 100 that breath gas analysis unit 410 is not arranged in an external device, but is present as a separate device from the ventilator 450 .

The measured variable provided via the respiratory gas signal 112 is the oxygen concentration of the expiratory gas flow, which is preferably measured in the expiratory gas branch of the tube system 460 via a corresponding sensor system of the ventilator 450 .

5 shows a schematic representation of a second embodiment of the ventilation system 505 according to the second aspect of the invention.

The medical system 400 shown essentially corresponds to that in 1 illustrated medical system 100. The respiratory gas analysis unit 110 is arranged within the ventilator 550.

In contrast to the ventilation system 505, the output is output via the output signal 149 to a control unit 570 of the ventilation system 505. The control unit 570 is connected to a dosing unit 580 and is designed to output a control signal 572 to the dosing unit 580 that indicates a medicament dosage for dispensing a medicament into the respiratory gas circuit of the ventilator 550 . The control unit 570 determines this release based on the output value 148 of the evaluation unit 140. In the exemplary embodiment shown, the dosing unit is not part of the ventilation system 505. In an alternative exemplary embodiment, not shown, the dosing unit is part of the ventilation system according to the invention.

The exemplary embodiment shown allows the dosage of a medication for ventilation to be set as a function of the current cardiac output or another parameter 107 dependent on cardiac output. As a result, short-term changes in the condition of the patient 102 can be taken into account when dosing the medication. For example, a pharmacokinetic and/or pharmacodynamic model stored in the control unit or provided to the control unit can be used for such a setting of the dosage, in order to thereby take into account the effect of the drug when setting the dosage.

In the present case, the control unit 470 is connected to the evaluation unit 140 via a cable. In an alternative exemplary embodiment, the communication between these two units can take place wirelessly. Finally, the control unit can be present as a separate unit that is spatially separated from other units, or in a common housing with at least one other unit of the ventilation system, as is shown in 6 is shown.

6 shows a schematic representation of a third embodiment of the ventilation system 605 according to the second aspect of the invention.

The ventilation system 605 differs from that in 5 Ventilation system 505 shown that the control unit 670 is arranged within the ventilator 650. The control unit 670 is also not designed to set the dosage of medication, but to adjust a ventilation parameter, in particular the positive end-expiratory pressure, for the ventilation of the patient 102 by the ventilator 650. This adjustment is based on the output value 148, the the cardiac output or another cardiac output-dependent parameter 107 is indicated. In this way, the ventilation can be quickly adapted to the current condition of the patient 102 .

Alternatively or additionally, the control unit 670 can be used to adjust the oxygen supply based on the received output value 148 .

In addition to the recorded output value, patient-specific information can be collected via external devices and taken into account when adjusting the ventilation parameters. For example, the weight of the patient can be determined using scales located at the patient's bed. Alternatively or additionally, an activity level of the patient can be determined via an optical monitoring device, based on which the cardiac output-dependent parameter is to be evaluated.

In a further exemplary embodiment that is not shown, the control unit is designed to adjust, initiate or cancel a ventilation maneuver based on the cardiac output-dependent parameter 107 as an alternative or in addition to adjusting a ventilation parameter according to the exemplary embodiment shown. In this way, it is possible to react particularly advantageously to a current development of the cardiac output or a corresponding parameter dependent thereon when the patient is being ventilated.

The adaptation of the respiration parameters according to this exemplary embodiment is combined in a particularly advantageous exemplary embodiment ned with the discontinuation of the delivery of the drug according to the in 5 illustrated embodiment.

7 FIG. 7 shows a flow chart of an embodiment of a method 700 according to a third aspect of the invention.

The method 700 according to the invention is designed to determine a cardiac output-dependent parameter of a patient to be treated. The method has the steps described below.

A first step 710 includes receiving a respiratory gas signal that indicates at least one measured variable relating to the patient's respiratory gas.

A subsequent step 720 includes determining and providing a respiratory gas analysis variable indicative of the oxygen uptake based on the respiratory gas signal.

A next step 730 includes measuring a first measured variable indicative of the arterial oxygen saturation and outputting a corresponding first sensor signal.

A further step 740 includes measuring a second measured variable indicative of the venous oxygen saturation and outputting a corresponding second sensor signal.

A subsequent step 750 includes receiving the first and second sensor signals.

A final step 760 includes calculating and outputting an output value for the cardiac output-dependent parameter based on the respiratory gas analysis variable, on the first measured variable and on the second measured variable.

Step 710 is always carried out before step 720, since the respiratory gas signal must be received before the respiratory gas analysis variable can be determined based thereon. Furthermore, steps 730 and 740 are always carried out before step 750, since the two sensor signals can only be received after the measured variables have been determined and the corresponding signals have been output. However, the order of steps 730 and 740 is arbitrary. Furthermore, the order between the provision of the respiratory gas analysis variable and the measured variables is arbitrary and therefore not fixed to the specified order. Only step 760 is always the final step for the method according to the invention according to this exemplary embodiment.

Time intervals at which the measurements relating to the patient's breathing gas are received via the breathing gas signal can differ from the time intervals at which the first and second measurements are measured.

The current condition of the patient is preferably taken into account in real time or at least essentially in real time. The measured variable relating to the respiratory gas of the patient is output to the respiratory gas analysis unit according to step 710, preferably at intervals of less than 30 seconds, preferably less than 10 seconds, particularly preferably less than 5 seconds.

Preferably, the first measured variable and/or the second measured variable is output via the respective sensor signal at intervals of less than 10 seconds, preferably less than 5 seconds, particularly preferably less than 2 seconds.

In an advantageous exemplary embodiment, the method according to the invention also includes receiving a value of the currently present hemoglobin concentration.

In a further advantageous exemplary embodiment, the method according to the invention is supplemented by an additional final method step, which includes controlling delivery of a medication into a respiratory gas circuit based on the output value for the cardiac output-dependent parameter.

In a further exemplary embodiment, not shown, the method according to the invention is supplemented by an additional final method step, which includes adjusting a ventilation parameter, in particular the positive end-expiratory pressure, based on the output value for the cardiac output-dependent parameter.

Reference List

100,200,300,400

medical system

102

patient

107

Cardiac Output Dependent Parameter

110, 210, 410

breath analysis unit

112

breathing gas signal

114

analysis signal

115

external medical device

120, 220

first sensor unit

122

first sensor signal

130, 230

second sensor unit

132

second sensor signal

140, 240

evaluation unit

142

Respiratory Gas Analysis Size

144

first metric

146

second metric

147

calculation rule

148

output value

149

output signal

216, 316

Housing

217

Respiratory Gas Signal Interface

218

measurement signal interface

224

Disposable part of the first sensor unit

226

Sensor part of the first sensor unit

234

Disposable part of the second sensor unit

236

Sensor part of the second sensor unit

318

Handle

328

first shot

338

second shot

405, 505, 605

ventilation system

450, 550, 650

ventilator

460

hose system

462

Y piece

570, 670

control unit

572

control signal

580

dosing unit

700

procedure

710, 720, 730, 740, 750, 760

process steps

Claims (13)

Medical system (100) for determining a cardiac output-dependent parameter (107) of a patient (102) to be treated - a respiratory gas analysis unit (110) which is designed to determine and provide a respiratory gas analysis variable (142) indicative of the oxygen uptake from a respiratory gas signal (112) which indicates at least one measured variable relating to the respiratory gas of the patient (102), - a first sensor unit (120), which is designed to measure a first measured variable (144) indicative of the arterial oxygen saturation and to output a corresponding first sensor signal (122), - a second sensor unit (130) which is designed to measure a second measured variable (146) indicative of the venous oxygen saturation and to output a corresponding second sensor signal (132), and - an evaluation unit (140) which is designed to receive the first and second sensor signals (122, 132) and based on the respiratory gas analysis variable (142), on the first measured variable (144) and on the second measured variable (146). To calculate and output the output value (148) for the cardiac output-dependent parameter (107). Medical system (100) according to claim 1 wherein the at least one measured variable relating to the patient's breathing gas relates to an oxygen concentration and/or a carbon dioxide concentration of the expiratory gas flow. Medical system (100) according to claim 1 or 2 , wherein the evaluation unit (140) is designed to calculate the arterial oxygen content from the first measured variable (144), to calculate the mixed-venous oxygen content from the second measured variable (146) and to calculate the output value (148) based on the arterial oxygen content and on the mixed-venous to determine the oxygen content. Medical system (100) according to at least one of the preceding claims, wherein the cardiac output-dependent parameter (107) is the stroke index, the heart index, the stroke volume and/or the cardiac output of the patient (102) or a cerebral part of such a parameter. Medical system (200) according to at least one of the preceding claims, wherein the first sensor unit (220) and/or the second sensor unit (230) is designed to determine the corresponding measured variable (144, 146) non-invasively via an optical measurement. Medical system (200) according to at least one of the preceding claims, wherein at least the respiratory gas analysis unit (210) and the evaluation unit (240) are arranged in a common housing (216). Medical system (200) according to at least one of the preceding claims, wherein the first sensor unit (220) and/or the second sensor unit (230) is formed by a sensor patch which communicates wirelessly with the evaluation unit (240). Medical system (300) according to at least one of the preceding claims, wherein the respiratory gas analysis unit (210), the first and second sensor units (220, 230) and the evaluation unit (240) for providing a mobile transport state of the medical system (300) in and/or on a common housing (316) of the medical system (300) can be arranged. Ventilation system (405) for ventilating a patient (102) to be treated, with - A respirator (450), in particular an anesthetic machine, and - A medical system (100) according to at least one of the preceding claims, wherein the ventilator (450) is designed to provide the respiratory gas signal (112) for the respiratory gas analysis unit (110). Ventilation system (505) according to claim 9 , wherein the respiratory gas analysis unit (110) is arranged in a housing of the ventilator (550). Ventilation system (505) according to claim 9 or 10 , wherein a control unit (570) of the ventilation system (505) is designed to receive the output value (148) for the cardiac output-dependent parameter (107) and, based on this output value (148), a drug dosage for dispensing a drug into a respiratory gas circuit of to control the ventilator (550). Ventilation system (605) according to at least one of claims 9 until 11 , wherein a control unit (670) of the ventilation system (605) is designed to receive the output value (148) for the cardiac output-dependent parameter (107) and based on this output value (148) a ventilation parameter, in particular the positive end-expiratory pressure, to be adapted for the ventilation of the patient (102) currently to be treated. Method (700) for determining a cardiac output-dependent parameter (107) of a patient (102) to be treated, having the steps: - Receiving a breathing gas signal (112) which indicates at least one measured variable relating to the breathing gas of the patient (102); - Determining and providing a breathing gas analysis variable (142) indicative of the oxygen uptake based on the breathing gas signal (112); - measuring a first measured variable (144) indicative of the arterial oxygen saturation and outputting a corresponding first sensor signal (122); - measuring a second measured variable (146) indicative of the venous oxygen saturation and outputting a corresponding second sensor signal (132); - receiving the first and second sensor signals (122, 132); - Calculating and outputting an output value (148) for the cardiac output-dependent parameter (107) based on the respiratory gas analysis variable (142), on the first measured variable (144) and on the second measured variable (146).

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