Control system and method for controlling a fresh gas dosing system for an anesthesia machine

Abstract

Control system and method for controlling a fresh gas dosing system for an anesthesia machine. The invention relates to a control system (100) for controlling a fresh gas dosing system for an anesthesia machine (110), comprising at least one patient gas measuring unit (120), an anesthetic agent dosing unit (130), a user interface (140), a fresh gas adjustment unit (150), and a processing unit (160). The processing unit (160) is designed to receive a measurement signal (122), a fresh gas signal (152), and an assistance signal (142), and, in the event of a transition from the deactivated assistance mode to the activated mode, to calculate and store a probable future evolution of the anesthetic agent concentration at the end of expiration. The processing unit (160) is further designed to emit a fresh gas correction signal (162) as soon as the concentration of anesthetic agent falls outside a defined range.Figure to be published with the abbreviation: Fig. 1.

Description

Title of the invention: Control system and method for controlling a fresh gas dosage for an anesthesia machine

[0001] The invention relates to a control system for controlling a fresh gas dosage for an anesthesia machine, as well as to a corresponding anesthesia machine. Furthermore, the invention relates to a method for controlling the fresh gas dosage for an anesthesia machine.

[0002] The dosing of anesthetic agents within a respiratory gas circuit of an anesthesia machine is typically carried out by controlling a volume flow rate of a fresh gas supplied to the respiratory gas circuit and by dosing a concentration of anesthetic agent within this fresh gas.

[0003] In this case, it is usual to reduce the volume flow rate of the fresh gas when the concentration of anesthetic agent at the end of the patient's expiration approaches a desired target concentration of anesthetic agent.

[0004] To carry out such an order, it is known, according to the document EP 2 808 049 A1, depending on a respective input by a user in relation to a target end-tidal anesthetic agent concentration and a desired control profile of fresh gas supply to achieve the target end-tidal concentration, to carry out a correspondingly fully automatic control of the fresh gas dosage and the anesthetic agent concentration.

[0005] In the case of such fully automatic controls, it is further known to graphically indicate a probable future development as a function of current measured values ​​of the anesthetic agent concentration at the end of expiration for a user of the anesthesia device.

[0006] The aim of the present invention is to provide improved control of the fresh gas dosage of an anesthesia machine, in particular control with a reliably predictable future course of the anesthetic agent concentration.

[0007] According to a first aspect of the invention, to achieve this objective, there is provided a control system for controlling a fresh gas dosage for an anesthesia apparatus, comprising at least one patient gas measuring unit, one anesthetic agent dosage unit, a user interface, a fresh gas adjustment unit and a processing unit.

[0008] The at least one patient gas measuring unit referred to above according to the invention is arranged in a respiratory gas circuit of the anesthesia apparatus and is designed to determine an anesthetic agent concentration at the end of expiration in the respiratory gas circuit and to provide a measurement signal corresponding to regular time intervals. Preferably, the concentration of anesthetic agent in the breathing gas circuit is determined continuously, i.e. practically without interruption over a certain time interval.

[0009] The above-mentioned anesthetic agent dosing unit according to the invention is designed to allow dosing of an anesthetic agent in a fresh gas supplied to the respiratory gas circuit.

[0010] The aforementioned user interface according to the invention is implemented in such a way as to activate or deactivate, in the presence of a corresponding user input, an assistance mode of the control system and to provide a corresponding assistance signal.

[0011] The above-mentioned fresh gas control unit according to the invention is arranged and designed to receive the assistance signal and, in the case of activation of the assistance mode, to adjust a reduction in a volume flow rate of the continuously supplied fresh gas over time as a function of a predetermined volume flow rate development. It is further designed to output a fresh gas signal at regular time intervals, which indicates the current volume flow rate of the continuously supplied fresh gas.

[0012] The aforementioned processing unit according to the invention is designed to receive the measurement signal and the fresh gas signal and to determine, from these, the current volume flow rate of the supplied fresh gas and the current end-tidal anesthetic concentration in the respiratory gas circuit. Furthermore, the processing unit is designed to receive the assistance signal and, in the presence of a transition from the deactivated assistance mode to the activated assistance mode, on the basis of the current volume flow rate, the predetermined volume flow rate development and the current end-tidal anesthetic concentration, to calculate a foreseeable future time-dependent development of the end-tidal anesthetic concentration, to provide or output it as a predefined development value and to store it.In this case, the aforementioned processing unit is further designed to provide a fresh gas correction signal to the fresh gas control unit as soon as the currently determined end-exhalation anesthetic concentration in the breathing gas circuit leaves a surrounding range of the predefined value of the course existing around the predefined value of the course. In this case, the fresh gas control unit is further designed to receive the fresh gas correction signal and, depending on the fresh gas correction signal, to change the predetermined volume flow course, whereby the continuously supplied fresh gas volume flow rate, in the case where the surrounding range is not reached, is increased compared to the initially predetermined volume flow course and is reduced in the case where the surrounding range is exceeded.

[0013] The invention is based on the knowledge that it is important in clinical routine to be able to rely on an indicated future course of the end-tidal anesthetic agent concentration for a user of the anesthesia machine. Furthermore, it has been recognized within the scope of the invention that an automated correction of the volume flow rate of the supplied fresh gas can help to maintain an indicated future course of the end-tidal anesthetic agent concentration. This is achieved according to the invention by taking a surrounding region around the predefined value of the calculated course as a basis and in case current measurement values ​​depart from this surrounding range, by providing the fresh gas correction signal to correct the supplied fresh gas quantity.

[0014] The control system according to the invention advantageously allows a reliable prediction of the future development of the concentration of anesthetic agent at the end of expiration, since any deviation from this development is corrected. As a result, the work of an anesthetist is simplified and planning safety is ensured for the development of the concentration of anesthetic agent at the end of expiration during anesthesia.

[0015] Furthermore, the control system according to the invention advantageously allows automated control which is possible without automated actuation of the anesthetic agent dosing unit. For the use of the anesthesia machine, this is advantageous because direct control of the supplied anesthetic agent concentration is possible without departing from an automated control system. Since too high an anesthetic agent concentration can be detrimental to the health of a person to be treated, the safety of this person is thus increased. Furthermore, the validation process of the control system according to the invention for use in hospitals can therefore be advantageously simplified.

[0016] Activation of the assistance mode can be done explicitly by a corresponding manual input, or implicitly by the selection of a particular functionality which also triggers the presence of the assistance mode.

[0017] In the context of the present invention, regular time intervals mean the presence of predetermined time intervals.

[0018] The predefined value of the development is calculated according to the invention only if the assistance signal indicates a transition to the activated assistance mode. After deactivation of the assistance mode, in the case of a new activation, a new future development is calculated in such a way that a predefined value of the development always relates to the currently activated assistance mode.

[0019] The variation of the predetermined volume flow rate development in the event of an exit from the surrounding range is carried out in such a way as to avoid oscillating behavior of the measured anesthetic agent concentration. This can, for example, be achieved by the the fact that variations are made based on empirical experiences, avoiding excessively large jumps within the evolution of the volume flow rate.

[0020] The modified predetermined volume flow rate development replaces, according to the invention, the predetermined volume flow rate development and is again considered as the predetermined volume flow rate development within the meaning of the invention for subsequent correction.

[0021] The individual devices within the control system can each be arranged at a distance from each other or in a common device, for example controlled by a common processor. The control system according to the invention can be an integral part of an anesthesia device or can be connected at least in part to a known anesthesia device in terms of the control of individual components.

[0022] Preferred embodiments of the control system according to the invention will be described below.

[0023] According to one embodiment, the control system according to the invention further comprises a transmission unit which is connected by signaling technology to the processing unit. The transmission unit is in this case (preferably) designed to provide the predefined value of the development with the calculated future development of the anesthetic agent concentration at the end of expiration as a function of time. Such a transmission is advantageously carried out, in a variant of this embodiment, in the form of a graphical representation, for example by means of a display of the transmission unit. This embodiment is particularly advantageous because the development over time of the anesthetic agent concentration at the end of expiration can thus be transmitted directly to a user of the control system.In order to be able to detect the development over the foreseeable time period particularly quickly in the clinical environment, a graphical representation is particularly advantageous. According to an alternative or supplementary embodiment, the predefined development value is transmitted via an interface of the processing unit and is displayed by an external device.

[0024] According to a particularly preferred embodiment of the control system according to the invention, the anesthetic agent dosing unit is designed in such a way that it allows for exclusively manually controlled dosing of the anesthetic agent. As a result, it can be ensured that defective components within the automated control process cannot lead to an excessive concentration of the supplied anesthetic agent. This can reduce the risk of damage to the health of a person to be treated. Furthermore, by manually controlling the anesthetic agent dosing unit, the control system according to the invention is simplified, since the anesthetic agent dosing unit does not need to communicate with other components of the dosing system. This preferred embodiment further allows the use of a known and already established anesthetic agent dosing unit on the market for the control system according to the invention.

[0025] According to another particularly preferred embodiment, the predetermined volume flow rate evolution comprises a continuous decreasing reduction of the volume flow rate over time. Such a decreasing reduction of the volume flow rate advantageously saves the amount of fresh gas to be used, since a continuous increase in the concentration of anesthetic arrangement at the end of expiration without accidentally exceeding a predetermined concentration of anesthetic agent can be achieved particularly easily.

[0026] According to the invention, the predetermined volume flow rate development of this embodiment is supplemented by each fresh gas correction signal with an incremental increase or an incremental reduction of the volume flow rate. As a result, a fresh gas correction signal always generates a new determination of an adapted predetermined volume flow rate development.

[0027] According to an advantageous embodiment of the control system, the user interface is further designed to receive a fresh gas input value and provide a corresponding fresh gas control signal, the fresh gas input value comprising information regarding a minimum volume flow rate to be provided by the fresh gas control unit, for the fresh gas to be supplied to the breathing gas circuit. Advantageously, this embodiment makes it possible to avoid volume flow rates that are so small that a desired target concentration of anesthetic agent at the end of expiration cannot be maintained sustainably.In particular, a user of the anesthesia machine, within the scope of the present embodiment, can adjust the course of the volume flow rate according to his own experience, so that he also has confidence in the functionality of the control system and does not have to fear the premature awakening of a patient after a successful anesthesia. Typically, the volume flow rate of fresh gas used, for example for Sevoflurane, is in a range of 300 ml / min to 8 L / min. The individually adjusted minimum volume flow rate will thus be in a range of 300 ml / min to 1 L / min. Preferably, the control system is designed in such a way that it does not allow an input value of a minimum volume flow rate lower than 250 ml / min. The value of 250 ml / min corresponds to the physiological minimum of the fresh gas to be supplied.

[0028] According to a preferred variant of the previous embodiment, the fresh gas control unit is further designed to receive the fresh gas control signal and to select the predetermined volume flow rate evolution from a number of predetermined volume flow rate evolutions on the basis of the fresh gas control signal. fresh gas control. In this variant, the predetermined volume flow rate is advantageously adapted to the requirements of a user of the control system. Furthermore, the selection of the predetermined volume flow rate advantageously makes it possible, for each conceivable fresh gas input value, to determine at the user interface a particularly suitable volume flow rate. The different predetermined volume flow rates are preferably stored in a memory module of the fresh gas control unit. According to an alternative variant of this embodiment, the processing unit is further designed to receive the fresh gas control signal, to select the predetermined volume flow rate from a number of predetermined volume flow rates on the basis of the fresh gas control signal and to send it to the fresh gas control unit.

[0029] According to a further advantageous embodiment of the control system according to the invention, the user interface is further designed to receive a limit concentration input value and to provide a corresponding limit concentration signal to the processing unit, the limit concentration input value comprising information concerning an anesthetic agent concentration at the end of expiration to be provided at most to the person to be anesthetized with the anesthesia device. In this embodiment, it is advantageously provided that the anesthetic agent concentration in the exhaled air of the person to be anesthetized does not exceed a predetermined limit value. This can be done, for example, by means of a corresponding control, by means of a corresponding warning signal or by means of a separate transmission of information concerning such a limit value exceeding.This prevents, in particular, the person to be anesthetized from suffering health damage due to an excessively high dosage of the anesthetic agent. Typically, the desired concentration of anesthetic agent, for example for Sevoflurane, is in a range of 3% by volume to 8% by volume. The maximum end-tidal anesthetic agent concentration that can be delivered will therefore, depending on the personal preferences of the user of the control system, be approximately in a range of 8% by volume to 12% by volume.

[0030] According to a particularly preferred variant of the previous embodiment, the processing unit is furthermore designed to provide an additional fresh gas correction signal to the fresh gas control unit as soon as the current end-tidal anesthetic concentration determined in the respiratory gas circuit exceeds the maximum end-tidal anesthetic concentration that can be supplied, and the fresh gas control unit is further designed to reduce the evolution of the original predetermined volume flow rate in response to this additional fresh gas correction signal. In this variant, it is advantageously ensured that the maximum end-tidal anesthetic agent concentration to be supplied cannot be exceeded. As a result, the user of the control system can leave the anesthesia machine unattended for a certain period of time without the risk of harmful anesthetic agent dosing occurring. The additional fresh gas correction signal can in this case be sent independently of the fresh gas correction signal to the fresh gas control unit.According to a further alternative or complementary embodiment, the fresh gas control unit is designed to receive the limit concentration signal and to select the predetermined volume flow rate course from a number of predetermined volume flow rate courses based on the limit concentration signal. In this case, a predetermined volume flow rate course is advantageously chosen which does not exceed the maximum input end-expiration anesthetic agent concentration that can be supplied.

[0031] According to another embodiment, the processing unit is designed to calculate, on the basis of the predefined value of the course, a probable target duration, the target duration implying the duration after which a target end-tidal anesthetic concentration is reached from the point of view of the calculated future course. As a result, a user of the control system can already assess, at the beginning of an anesthesia, after what time the target end-tidal anesthetic concentration will be reached. This allows a reliable assessment of how often in the next few minutes the control system should be controlled by the user of the control system. Preferably, in addition to the probable target duration, the duration until the determined predefined intermediate values ​​of the end-tidal anesthetic concentration are reached is provided.As a result, precise time planning of the entire anesthesia process can be carried out already at the beginning of the anesthesia, i.e. after activation of the assistance mode according to the invention.

[0032] According to a further embodiment, the processing unit is further designed to determine the surrounding range of the future development in such a way that it comprises the anesthetic agent concentrations which deviate from the calculated future development by less than 10%, preferably by less than 5%. Such a surrounding range is particularly advantageous since a constant correction by means of the fresh gas correction signal is avoided and, however, relatively precise adherence to the predefined value of the development is ensured. According to an alternative embodiment, the surrounding range of the future development is determined in such a way that it comprises the anesthetic agent concentrations which deviate from the calculated future development by less than 0.5% by volume, preferably by less than 0.2% by volume.

[0033] Preferably, the control unit according to the invention is further designed to maintain a proportion of oxygen in the fresh gas to be supplied to a person to be anesthetized within a predetermined oxygen range. Typically, this oxygen range is in a range from 60% by volume to 80% by volume. The control of the proportion of oxygen is carried out in a known manner by means of controlling a quantity of air within the fresh gas. Preferably, the fresh gas consists of a mixture of air and pure oxygen so that with a reduction of the air an increase in the proportion of oxygen in the fresh gas can also be achieved. Such control of the proportion of oxygen for anesthesia devices is known and will not be explained in detail below.

[0034] According to a second aspect of the invention, in order to achieve the objective according to the invention, there is provided an anesthesia apparatus comprising a control system according to at least one of the preceding embodiments.

[0035] The anesthesia apparatus according to the invention comprises, together with the control system according to the invention, also all the advantages of this control system. In particular, a particularly reliable prediction of the probable future development of the anesthetic agent concentration at the end of expiration can be guaranteed.

[0036] Advantageously, such an anesthesia device further allows automated control of the fresh gas dosage for adjusting the anesthetic agent concentration at the end of expiration without the anesthetic agent dosage unit having to be controlled automatically. Thus, manual adjustment of the supplied anesthetic agent dosage is possible, so that health risks caused by too high anesthetic agent dosage, for example due to incorrect handling of the control system, are avoided.

[0037] According to a third aspect of the invention, to achieve the objective according to the invention, there is provided a method for controlling a dosage of fresh gas for an anesthesia device which has the steps described below: - providing a patient gas measuring unit, an anesthetic agent dosing unit, a user interface, a fresh gas adjustment unit and a processing unit, the patient gas measuring unit to be arranged in a breathing gas circuit of the anesthesia machine; - entering a user input value via the user interface and issuing a corresponding assistance signal, in the case of activation of an assistance mode; - continuous determination of an anesthetic agent concentration at the end of expiration in the respiratory gas circuit by the gas measuring unit of patient and emission or sending of a corresponding measurement signal at regular time intervals; - receiving the assistance signal by the fresh gas control unit, adjusting a reduction in a volume flow rate of a fresh gas continuously supplied to the breathing gas circuit as a function of time in a manner corresponding to a predetermined volume flow rate development in the case of activation of the assistance mode indicated by the assistance signal, and outputting a fresh gas signal which indicates the current volume flow rate of the fresh gas continuously supplied; - reception of the assistance signal, the measurement signal and the fresh gas signal by the processing unit and determination of the current volume flow rate and the corresponding currently measured end-tidal anesthetic agent concentration; - calculation of a probable future course of the end-tidal anesthetic agent concentration as a function of time based on the current volume flow rate and the currently measured end-tidal anesthetic agent concentration, if a transition from the deactivated support mode to the activated support mode takes place; and - emission and storage of the future or time evolution as a predefined value of the evolution; - emission of a fresh gas correction signal as soon as the current determined concentration of anesthetic agent at the end of expiration in the respiratory gas circuit leaves a surrounding range realized around the predefined value of the evolution; and - modification of the predetermined volume flow rate development as a function of the fresh gas correction signal, the volume flow rate of the continuously supplied fresh gas being increased in comparison with the initial predetermined volume flow rate development in the case where the surrounding range is not reached and being reduced in the case where the surrounding range is exceeded.

[0038] These last two steps are always carried out during anesthesia when the concentration of anesthetic agent leaves the surrounding range. The other steps are carried out once each time within the framework of the method according to the invention. In the event that, in the meantime, the assistance mode is deactivated, the method according to the invention starts again to activate the assistance mode via the user input.

[0039] Preferred embodiments of the method according to the invention will be described below.

[0040] According to a particularly preferred embodiment, the method according to the invention further comprises the following steps: - receiving a fresh gas input value and outputting a corresponding fresh gas adjustment signal, the fresh gas input value comprising information regarding a minimum volume flow rate to be provided by the fresh gas adjustment unit, for the fresh gas to be supplied to the breathing gas circuit; - receiving the fresh gas adjustment signal and selecting the predetermined volume flow rate evolution from a plurality of predetermined volume flow rate evolutions based on the fresh gas adjustment signal.

[0041] In the context of this embodiment, it is advantageously ensured that when using an anesthesia device according to the invention, individual experience and preferences regarding the development of the desired volume flow rate can be taken into account. In this case, the minimum fresh gas volume flow rate constitutes a parameter in relation to which the user of the anesthesia device typically has an empirically based opinion regarding the ideal value thereof based on his daily work. The adjustability of an individual value is therefore particularly advantageous.

[0042] According to another embodiment, the method according to the invention further comprises the following steps: - receiving a limit concentration input value and transmitting a corresponding limit concentration signal to the processing unit, the limit concentration input value comprising information concerning an end-expiration concentration of anesthetic agent to be provided at most to the patient to be anesthetized with the anesthesia machine. - issuing an additional fresh gas correction signal as soon as the current end-tidal anesthetic agent concentration determined in the breathing gas circuit exceeds the maximum end-tidal anesthetic agent concentration that can be supplied, the original predetermined volume flow rate being reduced accordingly in response to this additional fresh gas correction signal.

[0043] In this embodiment, it is advantageously ensured that the concentration of anesthetic agent at the end of expiration cannot exceed a predetermined limit value. As a result, damage to health due to an excessively high dosage of the anesthetic agent can be avoided. Thus, the method according to the invention constitutes, according to this embodiment, a particularly safe method for controlling a dosage of fresh gas.

[0044] The invention will now be explained in more detail with the aid of advantageous embodiments illustrated schematically in the figures. In these figures, in detail:

[0045] [Fig. 1] illustrates a schematic representation of a first exemplary embodiment of the control system according to the invention according to the first aspect of the invention;

[0046] [Fig.2] illustrates a schematic representation of a second exemplary embodiment of the control system according to the invention according to the first aspect of the invention;

[0047] [Fig.3] is an illustration of a graphical representation of a predefined value of the evolution of a control system according to the first aspect of the invention;

[0048] [Fig.4] is an illustration of the predetermined evolution of the processed volume flow rate in a control system according to the invention according to the first aspect of the invention; and

[0049] [Fig.5] illustrates a flow diagram of a first example of implementation of the method according to the invention according to the third aspect of the invention.

[0050] [Fig.l] illustrates a schematic representation of a first exemplary embodiment of the control system 100 according to the invention according to the first aspect of the invention.

[0051] The control system 100 is implemented for controlling a fresh gas dosage for an anesthesia machine 110 and comprises at least one patient gas measuring unit 120, one anesthetic agent dosing unit 130, one user interface 140, one fresh gas adjustment unit 150 and one processing unit 160.

[0052] The at least one patient gas measuring unit 120 is arranged in a respiratory gas circuit 112 of the anesthesia device 110. In the present case, the patient gas measuring unit 120 is arranged in the region of a Y-shaped part 114 of the respiratory gas circuit 112 and therefore in the vicinity of the person 115 to be anesthetized with the anesthetic agent. An inlet 116 for fresh gas 117 is, on the other hand, arranged spaced apart or remote from the person 115 in the respiratory gas circuit 112. Furthermore, the respiratory gas circuit 112 has, on its exhalation end side, a valve 118 for adjusting the gas volume inside the respiratory gas circuit 112 and a CO2 absorber 119 for reducing the proportion of carbon dioxide in the inspiration air supplied by the anesthesia machine 110.

[0053] The patient gas measuring unit according to the invention is designed to determine an anesthetic agent concentration at the end of expiration in the respiratory gas circuit and to provide a corresponding measuring signal at regular time intervals. The measuring signal 122 is in this case sent to the processing unit 160 by cable or via a radio connection.

[0054] The anesthetic agent dosing unit 130 is designed to enable dosing of an anesthetic agent into a fresh gas 117 supplied to the respiratory gas circuit 112. The anesthetic agent dosing unit 130 is in this case connected directly via a first fresh gas line 132 to the fresh gas control unit 150. In addition to the first fresh gas line 132, a second fresh gas line 134 which bypasses the anesthetic agent dosing unit 130 leads directly to the fresh gas inlet 116 117. In the illustrated embodiment, the anesthetic agent dosing unit 130 is designed to enable dosing of the anesthetic agent with exclusively manual control. This is achieved in this case by means of a control element 136 which must be operated manually.

[0055] The user interface 140 is designed to activate or deactivate, in the presence of a corresponding user input, an assistance mode of the control system and to provide a corresponding assistance signal 142. The user input is carried out in the illustrated embodiment by pressing a corresponding key on the user interface 140. After activation, by pressing this key again, the assistance mode can be deactivated, which again leads to the output of a corresponding assistance signal 142. In the illustrated embodiment, the user interface 140 is part of a general input unit 144 of the anesthesia device 110 in question.

[0056] The fresh gas control unit 150 is arranged and designed to receive the assistance signal 142 and, in the case of activation of the assistance mode, to set a reduction in a volume flow rate of the continuously supplied fresh gas 117 over time as a function of a predetermined volume flow rate development. The fresh gas control unit 150 is further designed to provide a fresh gas signal 152 at regular time intervals, which indicates the current volume flow rate of the continuously supplied fresh gas. In the present case, the fresh gas control unit 150 is directly integrated into a fresh gas supply 154, namely into an O2 supply and an air supply. In an exemplary embodiment not shown, the supplied fresh gas is also N2O.In the case of the predetermined volume flow rate development, this is a development that includes a continuously decreasing reduction of the fresh gas volume flow rate over time. The predetermined volume flow rate development is in this case chosen in such a way that it begins in a range of the currently supplied volume flow rate such that no variation in the form of a volume flow jump takes place when the assistance mode is activated.

[0057] The processing unit 160 is designed to receive the measurement signal 122 and the fresh gas signal 152 and to determine, from these, the volume flow rate of the supplied fresh gas and the current end-tidal anesthetic concentration in the respiratory gas circuit. Furthermore, the processing unit 160 is designed to receive the assistance signal 142 and, in the presence of a transition from the deactivated assistance mode to the activated assistance mode, on the basis of the current volume flow rate, the predetermined volume flow rate course and the current end-tidal anesthetic concentration, to calculate a foreseeable future time-dependent end-tidal anesthetic concentration course, to provide it as a predefined course value and to store it. The predetermined volume flow rate course is in this case transmitted via the fresh gas signal 152 or is presented to the processing unit 160 via an internal memory.In this case, the processing unit is further designed to provide a fresh gas correction signal 162 to the fresh gas control unit as soon as the currently determined end-exhalation anesthetic concentration in the breathing gas circuit 112 deviates from a surrounding range of the predefined value of the actual course around the predefined value of the course. In the illustrated embodiment, the surrounding range is formed such that it comprises the anesthetic concentrations which deviate from the calculated future course by less than 10%, preferably by less than 5%. According to a non-illustrated embodiment, the surrounding range is selected such that it comprises the anesthetic concentrations which deviate from the calculated future course by less than 0.5%, preferably by less than 0.2%.

[0058] Furthermore, the fresh gas adjustment unit 150 is designed to receive the fresh gas correction signal 162 and, depending on the fresh gas correction signal 162, to change the predetermined volume flow rate course, the continuously supplied fresh gas volume flow rate 117, in the case where the surrounding range is not reached, being increased compared to the initially predetermined volume flow rate course and being reduced in the case where the surrounding range is exceeded.

[0059] Sevoflurane is currently used as an anesthetic agent, however, the control system according to the invention can be used with any type of anesthetic agent.

[0060] [Fig.l] does not illustrate all the elements of a typical respiratory gas circuit as usually present when using an anesthesia machine. Such typical elements are generally known and are not essential to the control system according to the invention so that details with respect to them will not be entered into.

[0061] According to an exemplary embodiment not illustrated, the control system according to the invention comprises two patient gas measuring units which determine the concentration of anesthetic agent at the end of expiration in parallel. This means that a fault in the patient gas measuring unit can be detected particularly quickly and automatically.

[0062] [Fig.2] illustrates a schematic representation of a second example of embodiment of the control system 200 according to the invention according to the first aspect of the invention.

[0063] The control system 200 is distinguished from the control system 100 illustrated in [Fig.l] by the fact that it further has a transmission unit 270.

[0064] The transmitter unit 270 is connected to the processing unit 260 by means of signaling technology and is designed to provide the predefined value of the development with the calculated future development of the end-exhalation anesthetic agent concentration as a function of time in the form of a graphical representation. The graphical representation is carried out in this case on a display 272 of the transmitter unit 270. In the illustrated embodiment, in addition to the graphical representation, the probable time after which a target end-exhalation anesthetic agent concentration is reached from the point of view of the calculated future development is provided.

[0065] According to an exemplary embodiment not illustrated, the emission of the future evolution is carried out by means of the emission of predetermined characteristic values ​​of this future evolution.

[0066] Furthermore, the control system 200 differs from the control system 100 in that the user interface 240 is designed to receive a fresh gas input and output a corresponding fresh gas adjustment signal 244. The gas input in this case comprises information regarding a minimum volume flow rate to be provided by the fresh gas adjustment unit, for the fresh gas 117 to be supplied to the breathing gas circuit 112. Typically, the volume flow rate of fresh gas used, for example for Sevoflurane, is in a range of 300 ml / min to 8 L / min. The individually adjusted minimum volume flow will thus be in the range of 300 ml / min to 1 L / min. In this case, the control system is designed in such a way that it does not allow an input value of a minimum volume flow lower than 250 ml / min. The value of 250 ml / min corresponds to the physiological minimum of the fresh gas to be supplied, regardless of the anesthetic agent used.

[0067] The fresh gas adjustment unit 250 is in turn designed to receive the fresh gas adjustment signal 244 and to select the predetermined volume flow rate evolution from a number of predetermined volume flow rate evolutions based on the fresh gas adjustment signal 244. The plurality of predetermined volume flow rate evolutions is stored in a memory unit 254 integrated in the respiratory gas adjustment unit 250.

[0068] According to an exemplary embodiment not illustrated, the processing unit is designed to receive a fresh gas adjustment signal, and to emit a warning signal as soon as the minimum volume flow rate entered is obtained.

[0069] Finally, the user interface 240 is further designed to receive a limit concentration input value and to send a corresponding limit concentration signal 246 to the processing unit. The limit concentration input value indicates in this case what the maximum permissible concentration of anesthetic agent is at the end of expiration. Typically, the concentration of anesthetic agent in the context of anesthesia is maintained in a range of 3% by volume to 8% by volume. The limit concentration input value should therefore preferably be located in a range of between 8% by volume and 12% by volume depending on the range in which a user of the control system according to the invention would prefer to work.

[0070] The processing unit 260 is further designed to provide a corresponding additional fresh gas correction signal 262 to the fresh gas control unit 250 as soon as the currently determined end-tidal anesthetic concentration in the breathing gas circuit exceeds the maximum end-tidal anesthetic concentration that can be supplied in the breathing gas circuit. In response to this additional fresh gas correction signal 262, the initial predetermined volume flow rate is reduced accordingly by the fresh gas control unit 250. Initial predetermined volume flow rate is understood to mean the predetermined volume flow rate that has adjusted after the last fresh gas correction signal 162, 262, or in the case where no fresh gas correction signal 162, 262 has yet been sent, that has been established after activation of the support mode.

[0071] [Fig. 3] is an illustration of a graphical representation 300 of a predefined value of the evolution 310 of a control system according to the first aspect of the invention.

[0072] The graphical representation 300 illustrates a diagram whose y-axis 320 indicates the concentration of anesthetic agent at the end of expiration in % by volume. In addition, the limit concentration 325, i.e. the predetermined or manually adjusted maximum concentration of anesthetic agent at the end of expiration is also indicated on the y-axis.

[0073] The abscissa axis 330 of the graphical representation 300 indicates the time from the start of the anesthesia process in min. In an exemplary embodiment different not shown, the graphic representation indicates the time from the start of the activation of the assistance mode.

[0074] In the illustrated example of the predefined value of the progression 310, the assistance mode has already been activated at the beginning of the anesthesia process. The typical progression of such a predefined value of the progression 310 comprises in this case an initial range 312 with a strong increase in the end-expiration anesthetic concentration, which corresponds to a high volume flow of fresh gas at the beginning (see for this purpose [Fig. 4]). After the initial range 312, a target range 314 is established in which the end-expiration anesthetic concentration is located in the range of a desired target end-expiration anesthetic concentration 316.

[0075] The surrounding range 318 which includes the concentrations of anesthetic agent which deviate from the predefined value of the evolution 310 by less than 0.5% by volume is carried out around the predefined value of the evolution 310.

[0076] According to an exemplary embodiment not shown, the actual measured development of the anesthetic agent concentration is further indicated, which cannot be located outside the surrounding range due to the automated control by means of the fresh gas correction according to the invention.

[0077] [Fig.4] is an illustration of a predetermined volume flow evolution 400 processed in a control system according to the invention.

[0078] [Fig.4] illustrates in this case a diagram in which a volume flow rate in L / min is plotted on the ordinate axis 420 and the time is plotted in min on the abscissa axis 430.

[0079] The volume flow rate evolution 400 begins with an initial volume flow rate 405 which exists at the activation of the assistance mode. From there, the predetermined volume flow rate evolution 400 is predefined by the fresh gas control unit. In this case, the predetermined volume flow rate evolution 400 was determined in the present case on the basis of a minimum volume flow rate 408 entered by the user of the control system for the fresh gas supplied to the breathing gas circuit.

[0080] [Fig. 4] also illustrates in dotted lines a modified predetermined volume flow rate evolution 440 which is obtained by a reduction 445 of the initial predetermined volume flow rate evolution 400. The step caused by the fresh gas correction signal can be recognized in the modified predetermined volume flow rate evolution 440. Such a reduction 445 will have occurred for example if the current anesthetic agent concentration at the end of expiration exceeds the surrounding range. In addition, the continuous decreasing reduction, carried out elsewhere, of the volume flow rate 400, 440 as a function of time can be recognized.

[0081] The illustrated reduction 445 and the corresponding modified volume flow rate evolution 440 are provided only as examples. In additional embodiments not illustrated, the extent of the variation and / or the modified volume flow rate evolution are realized differently.

[0082] [Fig.5] illustrates a flow diagram 500 of a first exemplary embodiment of the method according to the invention according to the third aspect of the invention.

[0083] The method 500 according to the invention for controlling a dosage of fresh gas for an anesthesia device has the steps 510, 520, 530, 540, 550, 560, 570, 580, 590, explained below.

[0084] A first step 510 comprises providing a patient gas measuring unit, an anesthetic agent dosing unit, a user interface, a fresh gas adjustment unit and a processing unit, the patient gas measuring unit to be arranged in a breathing gas circuit of the anesthesia machine.

[0085] A further step 520 comprises inputting a user input value via the user interface and outputting a corresponding assistance signal, in the case of activation of an assistance mode.

[0086] An additional step 530 comprises a continuous determination of an anesthetic agent concentration at the end of expiration in the respiratory gas circuit by the patient gas measuring unit and outputting a corresponding measurement signal at regular time intervals.

[0087] A subsequent step 540 comprises receiving the assistance signal by the fresh gas adjustment unit, adjusting a reduction of a volume flow rate of a fresh gas continuously supplied to the respiratory gas circuit as a function of time in a manner corresponding to a predetermined volume flow rate evolution in the case of activation of the assistance mode indicated by the assistance signal, and outputting a fresh gas signal which indicates the current volume flow rate of the continuously supplied fresh gas.

[0088] An additional step 550 comprises receiving the assistance signal, the measurement signal and the fresh gas signal by the processing unit and determining the current volume flow rate and the corresponding currently measured end-tidal anesthetic agent concentration.

[0089] A subsequent step 560 comprises a calculation of a probable future evolution of the end-tidal anesthetic agent concentration as a function of time based on the current volume flow rate and the currently measured end-tidal anesthetic agent concentration, if a transition from the deactivated assist mode to the activated assist mode takes place.

[0090] In a step 570 connected thereto, the future evolution is provided and is stored in the form of a predefined value of the evolution.

[0091] An additional step 580 comprises an emission of a fresh gas correction signal as soon as the current determined concentration of anesthetic agent at the end of expiration in the respiratory gas circuit leaves a surrounding range realized around the predefined value of the evolution.

[0092] A final step 590 comprises a modification of the predetermined volume flow rate evolution as a function of the fresh gas correction signal, the volume flow rate of the continuously supplied fresh gas being increased in comparison with the initial predetermined volume flow rate evolution in the case where the surrounding range is not reached and being reduced in the case where the surrounding range is exceeded.

[0093] Step 510 is typically performed before a first anesthesia process and is then retained unchanged during a plurality of anesthesia processes.

[0094] Steps 580 and 590 take place in case the surrounding range is departed from and, according to the invention, a corresponding control of the fresh gas volume by the fresh gas correction signal is necessary. Therefore, these steps can also take place several times within the same anesthesia process.

[0095] It is particularly advantageous that the method according to the invention can be carried out without control of the anesthetic agent dosing unit, since the anesthetic agent concentration no longer needs to be changed after an initial adjustment, for example manually, since the control according to the invention already operates with an exclusively fresh air control.

[0096] The following parts, elements, components, pieces and means of the invention are referenced as follows in the accompanying drawings:

[0097] 100, 200 Control system

[0098] 110 Anesthesia machine

[0099] 112 Respiratory gas circuit

[0100] 114 Y-piece

[0101] 115 Person

[0102] 116 Entry

[0103] 117 Fresh gas

[0104] 118 Valve

[0105] 119 CO2 absorber

[0106] 120 Patient gas measuring unit

[0107] 122 Measurement signal

[0108] 130 Anesthetic agent dosage unit

[0109] 132 First fresh gas line

[0110] 134 Second fresh gas line

[0111] 136 Manually operated control element

[0112] 140, 240 User interface

[0113] 142 Activation signal

[0114] 144 General Input Unit

[0115] 150, 250 Fresh gas control unit

[0116] 152 Fresh gas signal

[0117] 154 Fresh gas supply

[0118] 160, 260 Processing Unit

[0119] 162 Fresh gas correction signal

[0120] 244 Fresh gas adjustment signal

[0121] 246 Limit concentration signal

[0122] 254 Built-in memory unit

[0123] 262 Additional fresh gas correction signal

[0124] 270 Emission unit

[0125] 272 Display

[0126] 300 Graphical representation

[0127] 310 Predefined value of evolution

[0128] 312 Initial range

[0129] 314 Target range

[0130] 316 Target concentration of anesthetic agent at end-expiration

[0131] 318 Surrounding beach

[0132] 320, 420 Y axis

[0133] 325 Limit concentration

[0134] 330, 430 Abscissa axis

[0135] 400 Evolution of the predetermined volume flow rate

[0136] 405 Initial volume flow rate

[0137] 408 Minimum volume flow rate entered

[0138] 440 Changed predetermined volume flow rate evolution

[0139] 445 Reduction

[0140] 500 Method

[0141] 510, 520, 530, 540, 550 Process steps

[0142] 560, 570, 580, 590

[0143] Of course, the invention is not limited to the embodiments described and shown in the attached drawings. Modifications remain possible, in particular from the point of view of the constitution of the various elements or by substitution of technical equivalents, without departing from the scope of protection of the invention.

Claims

1. Claims A control system (100) for controlling a fresh gas dosage for an anesthesia machine (110), comprising - at least one patient gas measuring unit (120) which is arranged in a breathing gas circuit (112) of the anesthesia device (110) and which is designed to determine an anesthetic agent concentration at the end of expiration in the breathing gas circuit (112) and to provide a corresponding measuring signal (122) at regular time intervals; - an anesthetic agent dosing unit (130) which is designed to allow dosing of an anesthetic agent into a fresh gas (117) supplied to the respiratory gas circuit (112); - a user interface (140) which is designed to activate or deactivate, in the presence of a corresponding user input, an assistance mode of the control system (100) and to provide a corresponding assistance signal (142); - a fresh gas control unit (150) which is arranged and designed to receive the assistance signal (142), and in the case of activation of the assistance mode, to set a reduction of a volume flow rate of the continuously supplied fresh gas (117) over time depending on a predetermined volume flow rate development (400), and which is further designed to output at regular time intervals a fresh gas signal (152) which indicates the current volume flow rate of the continuously supplied fresh gas (117); and - a processing unit (160) which is designed to receive the measuring signal (122) and the fresh gas signal (152) and to determine from these the current volume flow rate of the supplied fresh gas (117) and the current concentration of anesthetic agent at the end of expiration in the breathing gas circuit (112), and the processing unit (160) is further designed to receive the assistance signal (142) and, in the case of a transition from the mode assistance mode deactivated to the assistance mode activated, on the basis of the current volume flow, the predetermined volume flow course (400) and the current end-tidal anesthetic concentration, to calculate a foreseeable future end-tidal anesthetic concentration course as a function of time, to output it as a predefined course value (310) and to store it, - the continuously supplied fresh gas volume flow, in the case of not reaching the surrounding range, being increased in comparison with the initially predetermined volume flow course and being reduced in the case of exceeding the surrounding range (445) control system (10) characterized in that the fresh gas control unit (150) is further designed to receive the fresh gas correction signal (162) and, depending on the fresh gas correction signal (162),to modify (440) the predetermined volume flow rate course (400), and in that the processing unit (160) is further designed to provide a fresh gas correction signal (162) to the fresh gas control unit (150) as soon as the current end-expiration anesthetic agent concentration determined in the respiratory gas circuit (112) leaves a surrounding range (318) of the predefined course value existing around the predefined course value (310).,

2. Control system (200) according to claim 1, further having a transmission unit (270) which is connected to the processing unit (260) by signaling technology and which is designed to provide the predefined value of the course (310) with the calculated future course of the anesthetic agent concentration at the end of expiration as a function of time in the form of a graphical representation (300).

3. Control system (100) according to claim 1 or 2, wherein the anesthetic agent dosing unit (130) is designed to allow dosing of the anesthetic agent with exclusively manual control.

4. A control system (100) according to at least one of the preceding claims, wherein the predetermined volume flow rate evolution (400) comprises a continuous decreasing reduction in the volume flow rate over time.

5. Control system (200) according to at least one of the preceding claims, wherein the user interface (240) is further designed to receive a fresh gas input value and to output a corresponding fresh gas adjustment signal (244), the fresh gas input value comprising information regarding a minimum volume flow rate (408) to be provided by the fresh gas adjustment unit (250), for the fresh gas (117) to be supplied to the breathing gas circuit (112).

6. A control system (200) according to claim 5, wherein the fresh gas adjustment unit (250) is in turn configured to receive the fresh gas adjustment signal (244) and to select the predetermined volume flow rate course (400) from a number of predetermined volume flow rate courses based on the fresh gas adjustment signal (244).

7. Control system (200) according to at least one of the preceding claims, wherein the user interface (240) is further configured to receive a limit concentration input value and to provide a corresponding limit concentration signal (246) to the processing unit (260), the limit concentration input value comprising information regarding a maximum end-tidal anesthetic agent concentration (325) that can be provided to the patient to be anesthetized with the anesthesia machine (110).

8. The control system (200) of claim 7, wherein the processing unit (260) is further configured to provide an additional fresh gas correction signal (262) to the fresh gas adjustment unit (250) as soon as the current end-tidal anesthetic agent concentration determined in the breathing gas circuit (112) exceeds the maximum end-tidal anesthetic agent concentration (325) that can be provided, and wherein the fresh gas adjustment unit (250) is further configured to accordingly reduce the original predetermined volume flow rate course (400) in response to this additional fresh gas correction signal (262).

9. Control system (200) according to at least one of the preceding claims, wherein the processing unit (260) is designed to calculate, on the basis of the predefined value of the course (310), a probable target duration, the target duration implying the duration after which a target end-tidal anesthetic agent concentration is reached from the point of view of the calculated future course.

10. Control system (100) according to at least one of the preceding claims, wherein the processing unit (160) is further configured to determine the surrounding range (318) of the future course such that it comprises the anesthetic agent concentrations which deviate from the calculated future course by less than 10%, preferably by less than 5%.

11. An anesthesia apparatus (110) comprising a control system (100, 200) according to at least one of the preceding claims.

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