Abstract:
A method and system for the controlled admixing of at least one gas or gas mixture to a gas (mixture) flow, so that, after the admixing to the gas (mixture) flow, the gas or gas mixture has a preadjusted and/or preadjustable concentration in this gas (mixture) flow by use of a pressure controller.

Description:
BACKGROUND AND SUMMARY OF THE INVENTION  
       [0001]     This application claims the priority of German Patent No. 103 214 48.8, filed 13 May 2003, the disclosure of which is expressly incorporated by reference herein.  
         [0002]     The invention relates to a method for the controlled admixing of at least one gas or gas mixture to a gas (mixture) flow, so that, after the admixing to the gas (mixture) flow, the gas or gas mixture has a preadjusted and/or preadjustable concentration in this gas (mixture) flow, wherein 
        a) the volume flow rate and/or pressure of the gas (mixture) flow is determined,     b) the actual value of the volume flow rate and/or of the pressure of the gas or gas mixture to be admixed is determined,     c) as a function of the determined volume flow rate and/or pressure of the gas (mixture) flow, the desired value of the volume flow rate and/or of the pressure of the gas or gas mixture to be admixed is calculated and is compared with the current actual value, and,     d) as a function of the difference between the desired value and the actual value, the actual value is adapted to the desired value.        
 
         [0007]     Alternatively, the invention relates to a method for the controlled admixing of a preadjusted and/or preadjustable quantity (desired value) of a gas or gas mixture to a gas (mixture) flow, wherein 
        a′) the volume flow rate and/or the pressure of the gas (mixture) flow is determined,     b′) the actual value of the gas or gas mixture to be admixed is compared with the desired value, and,     c′) as a function of the difference between the desired value and the actual value, the actual value is adapted to the desired value.        
 
         [0011]     Methods as well as systems of the above-mentioned type are used, for example, in the mechanical respiration of persons or patients, in the case of spontaneously breathing patients, during anaesthesia as well as in many different respiratory therapies, in which a gas or a gas mixture is supplied to the patent for therapeutic purposes.  
         [0012]     The controlled metered addition of NO to a respiratory gas is an example of this type of gas mixture mentioned. Nitric oxide or NO has become known as a drug treating pulmonary hypertension, i.e. a vasodilator. It is an advantage of the treatment by means of the already frequently described NO mixtures that NO is effective only locally, i.e. in the pulmonary circulation, and not systemically. The NO or the NO gas mixture is applied to the patient per inhalations. This means that the therapeutically effective gas is admixed to the respiratory gas supplied to the patient.  
         [0013]     When admixing gases or gas mixtures—in the following, now called “gas”—to a gas (mixture) flow—in the following, called “respiratory gas flow”, generally, the concentration of the gas to be added occurring in the respiratory gas flow after the admixing of the gas represents the parameter to be adjusted by the physician. The concentration parameter, should or must be kept constant during the treatment or therapy.  
         [0014]     If the volume flow rate of the respiratory gas now changes, a change of the gas flow to be admixed should also take place since otherwise the desired and adjusted concentration in the respiratory gas flow would not remain constant. The quantity or the volume of the gas to be admixed can now be changed either by a variation of the flow rate or the duration of the admixing or metering.  
         [0015]     As an alternative to the above-described method of operation, there is a large number of application cases in which a defined dosage of a gas is to be admixed to the respiratory gas flow for the patients. In these cases, the process according to the alternative of the initially mentioned method takes place.  
         [0016]     When treating patients, it should also be taken into account that, as a rule, gas is admixed to the respiratory gas flow, if possible, only during the inspiratory phase. In the case of a constant and continuous respiratory gas flow—as a function of the desired or adjusted concentration or dosage—only the flow rate of the gas to be admixed can be varied, because the admixing also has to take place continuously. If a change of the continuous respiratory gas flow takes place,—in order to be able to maintain the adjusted concentration—the flow rate of the gas to be admixed has to be correspondingly increased or decreased.  
         [0017]     Thus far, the adaptation of the actual value to the desired value has taken place by varying the flow rate of the gas or gas mixture to be admixed by means of a valve.  
         [0018]     It is a disadvantage that admission pressure fluctuations influence the actual flow rate. As a result, during each admission pressure fluctuation, the actual flow rate also has to be changed and therefore has to be readjusted by adjusting the valve.  
         [0019]     It is an object of the present invention to provide methods of the initially mentioned type as well as systems of the initially mentioned type for the controlled admixing of at least one gas or gas mixture to a gas (mixture) flow or respiratory gas flow which—independently of the above-mentioned desired application purposes—permits the providing of the gas quantity to be admixed, which is required during a treatment or therapy, at any point in time or the adapting of this gas quantity to the respective prevailing conditions, particularly to the volume flow rate and/or the pressure of the gas (mixture) flow or respiratory gas flow to be supplied to the patient.  
         [0020]     With respect to the method, this object is achieved in that the adaptation of the actual value to the desired value takes place by means of a pressure controller influencing the pressure of the gas or gas mixture to be admixed.  
         [0021]     The system alternatives according to the invention for the controlled admixing of at least one gas or one gas mixture to a gas (mixture) flow or respiratory gas flow are characterized in that the control device is a pressure controller.  
         [0022]     Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawing. 
     
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0023]     The sole FIGURE is a schematic view of an embodiment of the system according to the invention by which the alternatives of the method of the invention can be implemented. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0024]     The FIGURE shows a first measuring unit  10  which is used for the detection of a volume flow rate and/or of the pressure of the gas (mixture) flow or of the respiratory gas flow which is supplied, for example, to a patient for therapeutic purposes. The FIGURE does not show the conduit by way of which the respiratory gas flow is supplied to the patient.  
         [0025]     The measuring unit  10  is connected by way of a data line a with an analyzing unit  20 . The measuring unit  10  may be constructed as a flow rate or volume flow rate measuring unit. As an alternative or in addition, it may also be constructed as a pressure sensor which, for example, detects the vacuum which is created during the inspiratory phase.  
         [0026]     Furthermore, a measuring unit  40  is provided which is used for the detecting of the volume flow rate and/or of the pressure of the gas or gas mixture, which is to be admixed, in the conduit  1 . The measuring unit  40  is also connected by way of a data line  14  with the above-mentioned analyzing unit B.  
         [0027]     The gas or gas mixture to be admixed to the respiratory gas flow originates from a correspondingly suitable “gas source”  50 , for example, a gas cylinder or gas cartridge, and is admixed by way of the conduits  1 ,  2 ,  3  and  4  to the respiratory gas flow to be supplied to the patient.  
         [0028]     According to the invention, a pressure controller V is now provided in the conduit  1 . This pressure controller V is controlled, for example, by way of an electric servo motor or step motor  30 . The electric motor  30  is also connected by way of a data line  12  with the analyzing unit  20 .  
         [0029]     In the analyzing unit  20 , the desired value of the volume flow rate and/or of the pressure of the gas or gas mixture to be admixed is calculated as a function of the volume flow rate and/or pressure of the gas (mixture) flow determined by means of the measuring unit  10 , and is compared with the current actual value of the volume flow rate and/or pressure of the gas or gas mixture to be admixed determined by means of the measuring unit  40 . As a function of the difference between the desired value and the actual value, an adaptation then takes place of the actual value to the desired value in that, by means of the controller device V, which is assigned to the gas flow or gas mixture flow to be admixed and can be controlled by the analyzing unit  40 , the volume flow rate and/or pressure of the gas or gas mixture to be admixed is correspondingly changed.  
         [0030]     If—corresponding to another further development of the method of the invention—the pressure controller V is driven by a servo motor or step motor  30  and, by means of the respective position of the servo motor or step motor  30 , the preadjusted pressure of the pressure controller V is known, an additional detection of the actual flow rate value and/or actual pressure value of the gas or gas mixture to be admixed will not be necessary, because a conclusion can be drawn from the preadjusted pressure and the known geometry of the pressure controller V with respect to the flow rate of the gas or gas mixture to be admixed.  
         [0031]     Furthermore, a valve V 1  is provided in the conduit  2 , which valve V 1  is also in an operative connection with the analyzing unit  20  by way of a data line x or is controlled by the analyzing unit  20 . The valve V 1  is used for interrupting or (again) releasing at any time the gas flow to be admixed.  
         [0032]     In the case of a non-continuous respiratory gas flow, the patient&#39;s inspiratory and expiratory phases are detected by means of the measuring unit  10 . Corresponding to these phases, the gas flow to be admixed to the respiratory gas flow by way of the conduits  1 ,  2 ,  3  and  4  will then be interrupted or released by means of the valve V 1 . As a function of the respectively desired metering mode, the valve V 1  can be released only during the inspiratory phase, only during the expiratory phase or in arbitrary combinations of the above-mentioned operating modes. Thus, by means of the method of the invention, for example, an inspiration-synchronized respiration of a patient can be implemented.  
         [0033]     In addition—corresponding to another advantageous further development of the invention—a nozzle E 1  connected behind the valve V 1  can be provided in the conduit  3 . Because of the known geometry of the nozzle E 1 , the flow rate can be precisely calculated when an admission pressure is known. By way of the conduit  4 , the gas to be admixed is supplied to the respiratory gas flow conduit not illustrated in the FIGURE and is then supplied directly to the patient.  
         [0034]     As illustrated in the FIGURE, several conduits  2 ′ and  3 ′ or  2 ″ and  3 ″, which are arranged parallel to the conduits  2  and  3 , can also be arranged—behind the measuring unit  40 —, these conduits  2 ′ and  3 ′ or  2 ″ and  3 ″ also each having valves V 2  and V 3  respectively as well as nozzles E 2  and E 3  respectively. The controlling of the valves V 2  and V 3  by the analyzing unit  20  takes place by way of the data lines y and z respectively.  
         [0035]     Particularly when nozzles of different nozzles geometries are used, this embodiment of the invention permits the implementation of larger metering ranges. In addition, several of the valves V 1 , V 2  and V 3  respectively can be opened isochronously, whereby the volume flows are added up by the individual valves V 1 , V 2  and V 3  respectively or conduits  2 ′ and  3 ′, or  2 ″ and  3 ″ respectively.  
         [0036]     In addition, by means of this operating mode, the pressure drop, which necessarily occurs during the opening of a valve V 1 , V 2  and V 3  respectively and thus leads to a reduction of the flow rate, can be compensated in that, before the opening of the corresponding valve V 1 , V 2  and V 3  respectively, the pressure is increased in order to obtain the desired flow rate in this manner after the opening of the valve V 1 , V 2  and V 3  respectively. In order to achieve this, for example, also the opening time of the valve V 1 , V 2  and V 3  respectively can be lengthened correspondingly.  
         [0037]     As initially mentioned, the method alternatives as well as system alternatives according to the invention are suitable for the mechanical respiration of patients, for spontaneously breathing patients, for anaesthesia as well as for many different respiratory therapies, in which a gas or a gas mixture is supplied to the patent for therapeutic purposes.  
         [0038]     Besides the also above-mentioned metered addition of NO to the respiratory gas,—NO acting as a medication against pulmonary hypertension—, the gas or gas mixture to be admixed may be air, perfluorocarbon, O 2 , Xe, an Xe mixture, an NO mixture, CO, a CO mixture, a CO 2  mixture for respiratory stimulation, an H 2  mixture, N 2 O, an N 2 O mixture, an SF 6?  mixture, nitroso ethanol or an anaesthetic gas. The gas (mixture) flow or respiratory gas flow to be supplied to the patient preferably is air, O 2 , N 2 , Ar, Xe, He, SF 6?  and/or an anaesthetic gas, a mixture of these gases or another therapeutically effective or therapeutically ineffective gas or gas mixture.  
         [0039]     The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.