Patent Abstract:
A device for detecting the condition of flow in a respiration system combines the function of a nonreturn valve with the function of flow measurement in a common device. The device includes a valve arrangement ( 1 ) with a valve disk ( 9 ) and with a valve body ( 8 ), wherein the position of a valve disk ( 9 ) in relation to a valve seat ( 11 ) is detected. An indicator for a flow and a direction of flow ( 5 ), ( 6 ) is determined from the position of the valve disk ( 9 ). The position of the valve disk ( 9 ) can be determined inductively, electrically, electromechanically or optically. The flow and direction of flow ( 5 ), ( 6 ) determined can be used to control the respiration in a medical device.

Full Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of priority under 35 U.S.C. § 119 of German Patent Application DE 10 2008 028 733.4 filed Jun. 17, 2008, the entire contents of which are incorporated herein by reference. 
       FIELD OF THE INVENTION 
       [0002]    The present invention pertains to a device for recognizing oncoming flow effects at passively acting nonreturn valves. Determination of the volume flow, which is introduced into the patient, and of the quantity of breathing gas, which the patient again breathes out, is of considerable significance in the area of medical anesthesiology apparatus. For example, the absolute quantity of an anesthetic administered to a patient during anesthesia can be deduced from this. The absolute quantity of an anesthetic introduced is in turn a critical parameter in anesthesia, which should be known as exactly as possible. It is therefore important precisely in medical engineering to determine this variable as exactly as possible. It is just as decisive for this to be able to distinguish the phases of inspiration and expiration as precisely as possible. 
       BACKGROUND OF THE INVENTION 
       [0003]    To avoid rebreathing by the patient, a nonreturn valve is inserted into the branch of the respirator that delivers the breathing gas to the patient. Breathing gas flows through this so-called inspiration branch in the rhythm of respiration during the phase of inspiration, and the nonreturn valve is opened during inspiration. The nonreturn valve closes the flow path during the phase of expiration. To determine the volume flows of inspiration and expiration, for example, flow sensors in the form of hot wire anemometers are known from the state of the art, which operate in such a way that the resistance of a hot wire, which is arranged in the breathing gas flow, is determined. The hot wire is made of a material that has a temperature-dependent resistance. The extent to which the hot wire is cooled by the gas flow depends on the volume flow and hence on the velocity of flow, so that the resistance of the hot wire is an indicator of the velocity of flow. One drawback of this process is, however, the fact that these hot wire sensors require a defined flow situation, which requires a certain section for homogenizing the flow and hence a certain overall length. 
         [0004]    Both the flow sensors and the nonreturn valves are integrated with additional components, for example, a respiration drive and pressure sensors, in a respirator or anesthesia apparatus in a respiration system. This respiration system is designed such that it can be removed from the anesthesia apparatus for cleaning purposes. Due to the nonreturn valve and the flow sensor being arranged in series, a space requirement that essentially predefines the size of the entire respiration system is obtained in the respiration system. This makes it difficult to construct a compact respiration system. 
       SUMMARY OF THE INVENTION 
       [0005]    The object of the present invention is to improve the functions of flow measurement and of the nonreturn valve in a compact embodiment. The essential advantage that the space requirement for the flow measurement and nonreturn valve can be reduced is obtained by the combination of the nonreturn valve and the flow sensor. Another advantage arises from the reduction of the number of elements in the respiration system, which reduces the susceptibility to error and improves maintenance friendliness. 
         [0006]    The combination of flow measurement and nonreturn valve arises from the use of an element of the nonreturn valve to recognize the flow. In a passive nonreturn valve according to the state of the art, a disk is mounted on a number of holding elements or supports and seals the flow opening in case of planar contact in the valve seat. If only a flow from the side of the holding elements acts against the disk or there is a pressure gradient between the side of the holding elements and the opposite side of the disk, the disk is moved, so that the flow can pass through the valve. This is the direction of flow of the nonreturn valve. If the flow acts on the disk from the opposite side of the disk, the holding elements prevent a motion of the disk and no flow passes through the valve. This is the blocking direction of the nonreturn valve. 
         [0007]    The motion of the disk is used in the present invention to recognize the flow of a gas. 
         [0008]    A wound coil, which forms an electric oscillatory circuit together with a capacitor, is arranged as an inductance around the flow opening in a first embodiment according to the present invention. The oscillatory circuit has a natural frequency determined by the inductance and capacitance. The valve disk, which lies on the passage opening of the valve in the valve seat and seals same by contact and consists of a nondeformable material, for example, ceramic, is designed in this first embodiment according to the present invention such that an electrically conductive element with a relative magnetic permeability of about one is arranged as a valve element at or in the disk. The electrically conductive element determines, by its position in relation to the coil, an effect on the magnetic field by an eddy current being induced in the electrically conductive element. 
         [0009]    The eddy current represents a load for the oscillatory circuit, which extracts energy from the oscillatory circuit. The value of the load depends on the position of the disk in relation to the coil. If the disk is moved away from the coil by the flow and hence also by the electrically conductive element, the eddy current losses in the magnetic-electric circuit of the device become lower. If the oscillatory circuit is excited from the outside by an electric a.c. voltage in the proximity of the natural frequency, the resulting amplitude of the oscillatory circuit can be analyzed as an indicator of the distance of the electrically conductive element from the coil and hence as an indicator of the amount of the motion of the disk by the flow. Thus, it is possible to distinguish phases of inspiration from phases of expiration as well as to quantitatively analyze the flow rate by means of a characteristic, which is plotted as a function of the change in amplitude per unit quantity passing through. The analysis of the position of the valve disk makes it possible to recognize the flow and the direction of flow. The flow and the direction of flow can be used to control the respiration in a medical device, for example, in a respirator or in an anesthesia apparatus. 
         [0010]    An alternative variant of the first embodiment according to the present invention differs from this in that the valve disk is designed such that instead of an electrically conductive element, a magnetically conductive element with a relative magnetic permeability of &gt;&gt;1 is arranged as a valve element at or in the disk. As it were, an arrangement of a coil with a metal core and an air gap is thus obtained. The dimensions of the air gap are varied by the motion of the valve disk in the second embodiment according to the present invention. 
         [0011]    The overall inductance of the array and hence, in cooperation with the capacitance, the natural frequency of the oscillatory circuit thus change due to the motion of the valve disk brought about by the flow in the direction of passage. If the oscillatory circuit is excited from the outside by an electrical a.c. voltage in the vicinity of the natural frequency, the resulting change in the Q factor of the oscillatory circuit is an indicator of the change in the air gap in the magnetic circuit and hence an indicator of the distance between the magnetically conductive element and the coil and can finally be analyzed as an indicator of the amount of motion of the disk by the flow. 
         [0012]    The oscillatory circuit is preferably designed for the first embodiment such that the natural frequency is above the human hearing range of approx. 20 kHz; a value of 500 kHz is suitable as the upper limit value for the natural frequency to attain a sufficient depth of penetration of the magnetic field and to obtain a sufficient measuring effect. 
         [0013]    In one variant of the first embodiment according to the present invention, the valve disk is held in an inoperative position by a prestressed mechanical spring element. The characteristic of the spring is selected to be such that the valve disk is raised by the flow against the spring force. The valve can be used in any desired installation position in such an arrangement, because the spring characteristic essentially determines the path and the position of the valve disk as a function of the flow. 
         [0014]    In a preferred embodiment of the first embodiment according to the present invention, a disk made of a flexible material is fastened in the center of the passage opening on a holding structure. The holding structure is preferably of a star-shaped design and is fastened to the edge of the passage opening. The flexible valve disk is fastened in the center of the holding structure. The mode of operation arises from an elastic deformation and bending of the disk in the marginal area, as a result of which the air can pass through the valve from a direction of passage, the elastic deformation is restored into the original state without flow and again closes the valve by the contact surface of the valve disk not allowing any space for deformation in the valve seat, This arrangement with a valve disk made of a flexible material according to this preferred embodiment offers the advantage that the valve can operate in any desired installation position without an additional spring element, because the gravity acting on the valve disk is not utilized for sealing. The holding structure and the flexible valve disk are preferably designed such that the valve disk can be replaced by the user during cleaning and maintenance operations. A plurality of flexible plastics, elastomers or films, for example, neoprene or silicone, are available as the material for the valve disk for such a replacement part, because no specific requirements are imposed by single-time use on hygienic processing. 
         [0015]    The closing of the valve is detected by a contact in a second embodiment according to the present invention. A flexible valve disk is fastened here eccentrically to a holding structure in the passage opening by means of at least one fastening point. A contact pair, which detects the closing of the valve, is arranged on the side located opposite the fastening side. 
         [0016]    A valve seat is formed as a sealing closing surface for the valve in the outer contour of the passage opening. 
         [0017]    The contact pair is designed as an electrical make contact pair in a preferred embodiment of the second embodiment according to the present invention. A contact bridge is arranged as a contacting element at or in the valve disk. At least one pair of electric contact elements, which is provided with electric feed lines, is arranged in the closing surface. With the valve closed, the pair of contact elements is electrically connected via the contact bridge and the resulting electrical connection can be detected by an electrical volume resistance or resistance measurement. 
         [0018]    In an alternative variant of the embodiment according to the present invention, the contact pair is designed as an electromagnetic contact pair. An element made of a magnetic material is arranged here at or in the valve disk. An electromagnetic contact, preferably in the form of a Hall sensor or a Reed relay, which is provided with electrical feed lines, is arranged in the closing surface of the valve. With the valve closed, the electromagnetic element is actuated by the magnet in the valve disk, and the resulting electrical connection can be measured by an electrical volume resistance or resistance measurement. 
         [0019]    In another embodiment variant, the contact pair is implemented by a contactless contact pair to detect the motion of the valve. A contactless contact pair can be implemented in the form of a photoelectric cell, where an array comprising a light source and a light receiver is arranged at the closing surface of the valve. For example, a light-emitting diode may be used as a light source, and photosensitive resistors, phototransistors or photodiodes may be used as light receivers. 
         [0020]    With the valve closed, the optical path of the photoelectric cell is interrupted in a preferred embodiment by the valve disk and the signal of the light receiver is analyzed. 
         [0021]    A preferred embodiment is designed such that the valve disk is introduced into the holding structure via at least two fastening points, the at least two fastening points being arranged asymmetrically and the shape of the valve disk being selected to be such that only an unambiguous possibility is available for fastening the valve disk in the holding structure. Incorrect installation position of the valve disk is thus ruled out. 
         [0022]    A combination of the first embodiment with the second embodiment is provided in a third embodiment according to the present invention. A flexible valve disk is fastened here eccentrically at a holding structure in the passage opening by means of at least one fastening point. The valve disk is provided with a magnetically or electrically conductive material, whose approach to the valve seat can be detected via an arrangement in an oscillatory circuit according to the first exemplary embodiment. The analysis of the contact pair is used to determine a valve motion, which represents a final point in time of the phase of inspiration when the contact is closed and makes it possible to recognize breathing cycles, and the analysis of the change in the field is used for an additional quantitative evaluation of the flow rate over the determined opening path of the valve. 
         [0023]    Exemplary embodiments of the present invention will be explained in more detail below on the basis of the drawings. The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]    In the drawings: 
           [0025]      FIG. 1  is a schematic sectional view of a valve arrangement according to the invention with a nondeformable valve disk and a coil array; 
           [0026]      FIG. 2  is a schematic sectional view of the first valve arrangement according to  FIG. 1  shown with a drawing of the lines of magnetic flux, in the closed state; 
           [0027]      FIG. 3  is a schematic sectional view of the first valve arrangement according to  FIG. 1  shown with a drawing of the lines of magnetic flux, in the opened state; 
           [0028]      FIG. 4  is a schematic sectional view of an arrangement for the electrical analysis of the motions of the valve disk for the valves shown in  FIGS. 1 ,  2  and  3 ; 
           [0029]      FIG. 5  is a schematic sectional view of a second valve arrangement with an elastic valve disk and a coil array, in the closed state; 
           [0030]      FIG. 6  is a schematic sectional view of the second valve arrangement according to  FIG. 5 , in the opened state; 
           [0031]      FIG. 7  is a schematic individual component exploded view of the elastic valve disk and of the holding structure of the second valve arrangement; 
           [0032]      FIG. 8  is a schematic sectional side view of the holding structure of the second valve arrangement according to  FIGS. 5 through 7 ; 
           [0033]      FIG. 9  is a schematic sectional view of a third valve arrangement with a valve disk and with a contact arrangement in the opened state; 
           [0034]      FIG. 10  is a schematic sectional view of the third valve arrangement according to  FIG. 9 , in the closed state; 
           [0035]      FIG. 11  is a schematic individual component exploded view of the third valve disk and of the valve body of the third valve arrangement; 
           [0036]      FIG. 12  is a schematic sectional view of a variant of the first valve arrangement; 
           [0037]      FIG. 13  is a schematic sectional view of a variant of the third valve arrangement; 
           [0038]      FIG. 14  is a sectional view of a spring element for holing the valve disk in an inoperative position with a spring bias; 
           [0039]      FIG. 15   a  is a schematic view of a detector including a photoelectric cell with LED and receiver for the optical detection of the position of a valve disk, with the valve disk shown seated; 
           [0040]      FIG. 15   b  is a schematic view of the detector of  FIG. 15   a , with the valve disk shown unseated; 
           [0041]      FIG. 15   c  is a schematic top view of the detector of  FIG. 15   a ; and 
           [0042]      FIG. 16  is a schematic view of a respiration system with a valve arrangement according to the invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0043]    Referring to the drawings in particular,  FIG. 1  shows a schematic design of a first valve arrangement  1  according to the present invention in a half section along the horizontal axis  25  symmetrically to the central axis  13 , which contains a round first valve disk  9  with a first valve element  10 , designed as an embedded magnetic element, with a relative magnetic permeability substantially greater than one, a valve seat and a cylindrical valve body  8  with a coil  12  arranged thereon. 
         [0044]      FIG. 2  shows the first valve arrangement  1  according to  FIG. 1 , wherein the first valve disk  9  with an embedded element  10  is sealingly seated on a first valve seat  11 . The same reference numbers are used for identical components as in  FIG. 1 . 
         [0045]    In addition, a first magnetic field line curve  14  is shown in the closed state of the first valve arrangement  1 . The flow from the second direction of flow  6  cannot flow through the valve. 
         [0046]      FIG. 3  shows the first valve disk  9  raised by the flow from the first direction of flow  5  and a second magnetic field line curve  15  in the opened state of the valve arrangement  1  according to  FIG. 1 . The same reference numbers are used for identical elements as in  FIG. 1 . 
         [0047]    The different routing of the magnetic field lines  14 ,  15  with the opened and closed valve disk  9  can be seen in  FIGS. 2 and 3 . 
         [0048]      FIG. 4  shows how the valve arrangement  1  according to the present invention as shown in  FIGS. 1 ,  2  and  3  is integrated into an electronic circuit via a terminal contact pair  31 . The same reference numbers are used for identical elements as in  FIG. 1 . The first valve disk  9  lies on a first valve seat  11 . A first valve element  10  is embedded in the first valve disk  9 . An operating electronic unit  30  contains an arrangement of a capacitor  32 , which forms an electrical oscillatory circuit with a typical natural frequency together with the coil  12  located at the valve body  8 . The parallel resistor  36  is designed suitably for setting the damping of the oscillatory circuit. The oscillatory circuit is excited to oscillate in the vicinity of its natural frequency by means of an a.c. voltage source  34  with a protective resistor  33 . The first valve element  10  brings about damping of the amplitude of the oscillatory circuit, which is given by a proportional relationship with the distance between the first valve element  10  and coil  12 . The amplitude of oscillation can be measured via a voltage-measuring device  35 . 
         [0049]      FIG. 5  shows a second valve arrangement  2  with the peculiarity of an elastic second embodiment valve disk  16  and with a holding structure  19  for fastening the second embodiment valve disk  16 . 
         [0050]    The view shows the second embodiment valve disk  16  with a second embodiment valve element  23 , designed as an embedded magnetic element with a relative magnetic permeability substantially greater than one, a second embodiment valve seat  18  and a cylindrical valve body  8  with a coil  12  arranged thereon. The second embodiment valve arrangement  2  is shown in the closed state. The second embodiment valve disk  16  with the second embodiment valve element  23  being fastened to the holding structure  19  is sealingly seated on the second embodiment valve seat  18 , and flow according to the second direction of flow  6  is blocked in this manner. 
         [0051]      FIG. 6  shows the second embodiment valve disk  16  raised by the flow from the first direction of flow in the opened state of the second embodiment valve arrangement  2  according to  FIG. 5 . The second embodiment valve disk  16  is raised by the flow at the edge from the second embodiment valve seat  18  because of the flexible design, the flow opening  7  ( FIG. 7 ) is thus released, and the air can flow through the second embodiment valve arrangement  2  according to the first direction of flow  5 . 
         [0052]      FIG. 7  shows a view of the second embodiment valve arrangement  2  according to  FIGS. 5 and 6  comprising a second embodiment valve disk  16  and a holding structure  19  before joining together in a top view. The same reference numbers are used for identical elements as in  FIG. 5 . The holding structure  19  with a fastening point  20  receives the fastening hole  17  of the second embodiment valve disk  16 .  FIG. 7  also shows that the holding structure  19  leaves open a flow opening  7 . The holding structure  20  is formed in this example in a cross-shaped pattern from three support struts  24  with central fastening point  20 . Other shapes of the holding structure  19  can likewise be implemented. 
         [0053]      FIG. 8  shows a side view of the holding structure  19  and the fastening point  20  in detail. The ratios of the dimensions of the fastening point  20  and the second embodiment valve disk  16  are decisive for the function of the second embodiment valve arrangement  16 . The diameter of the fastening hole  17  of the second embodiment valve disk  16  is smaller than a cap  21  of the fastening point  20 . The fastening diameter  22  of fastening point  20  is smaller than the diameter of fastening hole  17  ( FIG. 7 ) of the second embodiment valve disk  16 . The consequence of these dimension ratios is that the second embodiment valve disk  16  can be joined together with the fastening point  20  via cap  21  because of the elastic material, but it cannot be separated by the flow from the fastening point  20  any more beyond the cap  21  after joining. The second embodiment valve disk  16  is held with a sufficient tolerance at the fastening diameter  22  of fastening point  20  in order to be able to elastically follow the flow. This means for the application that before the use of the second embodiment valve arrangement  2 , the second embodiment valve disk  16  is inserted into the holding structure  19  and can easily be removed after use, so that separate processing and disposal of the second embodiment valve disk  16  and of the valve body  8  is possible. 
         [0054]      FIG. 9  shows a third valve arrangement  3  in a half section along the horizontal axis  25  symmetrically to the central axis  15  with a third valve disk  28  and with a contact arrangement. The contact arrangement comprises electrical contact elements  26 , which are electrically connected to one another in the inoperative state by an electrical contact bridge  27 . The electrical contact is interrupted in the opened state shown of the third valve arrangement  3 . The air flows through the third valve arrangement  3  according to the first direction of passage  5 . The contact interruption can be contacted via the terminal contacts  31  and detected by an analysis circuit, not shown, for example, by means of a flow test or resistance measurement. The signal thus detected can be used as a trigger signal for controlling the respiration. The third valve disk  28  is connected by a mount  40  to the valve body  8 . Fastening points  20  with a cap  21  keep the third valve disk  28  fixed laterally at the valve body  8 . The third valve disk  28  is made thicker at the position of mount  40 . A groove  41  is prepared in the third valve disk directly next to the mount  40 , as a result of which the third valve disk  28  is mounted movably and elastically at the valve body  8  and can follow the flow motion. 
         [0055]      FIG. 10  shows the third embodiment valve arrangement  3  according to  FIG. 9  in the closed state. The same reference numbers are used for identical elements as in  FIG. 9 . Flow according to the second direction of flow  6  is blocked by the position of the third embodiment valve disk  28 . The contact connection can be contacted via the terminal contacts  31  and detected by an analyzing circuit, not shown, for example, by means of a flow test or resistance measurement. The signal detected in the process can be used as a trigger signal for controlling respiration in a respirator. 
         [0056]      FIG. 11  shows a view of the third embodiment valve arrangement  3  comprising the third embodiment valve disk  28  and a cylindrical valve body symmetrical to the central axis according to  FIGS. 9 and 10  before joining together in a three-dimensional view. The same reference numbers are used for identical elements as in  FIGS. 10 and 11 . The fastening points  26  in mount  40  at the valve body receive the fastening holes  17  of valve disk  28 . 
         [0057]    The ratios of the dimensions of the fastening points  20  and the third embodiment valve disk  28  are decisive for the function of the third embodiment valve arrangement  3 . The diameter of the fastening holes  17  of the third embodiment valve disk  28  is smaller than the caps  21  of the fastening points  20 . The fastening diameter  22  of the fastening points  20  is made smaller than the diameters of the fastening holes  17  of the third embodiment valve disk  28 . The consequence of these ratios of the dimensions is that the third embodiment valve disk  28  can be joined together with the fastening points via the caps  21  because of the elastic material, but it cannot be separated from the fastening points any more by the flow beyond the cap  21  after joining. The third embodiment valve disk  28  is held with sufficient tolerance at the fastening diameters  22  of the fastening points  20  in order to be able to elastically follow the flow. For use in the application, this means that the third embodiment valve disk  28  is inserted into the valve body  8  before the third embodiment valve arrangement  3  is used and it can be easily removed after use, so that separate processing or disposal of the third embodiment valve disk  28  and of the valve body  8  is possible. 
         [0058]    The third embodiment valve disk  28  is introduced into mount  40  via two fastening points  20 , wherein fastening points  20  are arranged in the valve body  8  asymmetrically on two fastening axes  29  offset at right angles, and the shape of the third embodiment valve disk  28  is selected to be such that only an ambiguous possibility is possible for fastening the valve disk  28  at the valve body  8 . Incorrect assembly is thus ruled out. Unambiguity is additionally predetermined by the asymmetry of the fastening points  20  in conjunction with mount  40 , combined with the shape of the valve disk  28 , which is half-round on one side and rectangular. 
         [0059]      FIG. 12  shows a first valve arrangement  1  according to  FIG. 1  comprising a valve disk  9  with an embedded valve element  10  and a coil  12  with a metal element arranged additionally at the valve body  8 . The same reference numbers are used for identical elements as in  FIG. 1 . The metal element  39  brings about guiding of the magnetic field lines and thus intensifies the measuring effect, which is caused by the motion of the first valve disk  9 . 
         [0060]      FIG. 13  shows a variant of the third arrangement according to  FIG. 9 . The same reference numbers are used for identical elements as in  FIG. 9  and  FIG. 1 . 
         [0061]    A coil  12  and a valve element  10  with a contact arrangement, comprising electrical contact elements  26  and an electrical contact bridge  27 , are arranged at the valve body  8  in this variant. Analysis of the contact connection can be used in this variant to recognize the phase of breathing, for example, to trigger a respirator. The position of valve element  10  in or at the third embodiment valve disk  28  in relation to the coil arranged around the coil form does affect the properties of the magnetic field. 
         [0062]    The change in the magnetic field properties is analyzed by means of an operating electronic unit ( FIG. 4 ) and it yields a quantitative indicator of flow as an additional measured variable besides the recognition of the phase of breathing. 
         [0063]    In a variant of the first embodiment according to the present invention, the valve disk is held in an inoperative position by a prestressed mechanical spring element  60  as shown in  FIG. 14 . The characteristic of the spring  60  is selected to be such that the valve disk is raised by the flow against the spring force. The valve can be used in any desired installation position in such an arrangement, because the spring characteristic essentially determines the path and the position of the valve disk as a function of the flow. 
         [0064]      FIGS. 15   a ,  15   b  and  15   c  shows features in which the detector comprises a photoelectric cell with LED  70  and receiver  72  for the optical detection of the position of a valve disk  90  in relation to the valve seat  110 . With the valve closed ( FIG. 15   a ), the optical path of the photoelectric cell is uninterrupted by the valve disk  90 . With valve open ( FIG. 15   b ), the optical path of the photoelectric cell is interrupted by the valve disk and the signal of the light receiver is analyzed. The situation may be reversed such that with the valve closed the optical path of the photoelectric cell is interrupted. As shown in  FIG. 15   c , the detector preferably provides two directions of measurement with photoelectric cells to provide two LEDs  70  and two receivers  72 . 
         [0065]      FIG. 16  shows a respiration system  120  with a respiration breathing gas flow passage  121  including an inspiration branch  122  and an expiration branch  124  with a patient connection  126 . The device  1 ,  2 ,  3  is provided for determining a flow condition in the breathing gas flow passage  121  of the respiration system. The respiration system  120  may include a blower/compressor  128  and may be a closed loop as shown with buffer volume  130  and CO 2  absorber  132  and directional valve  134 . Other respiration system arrangements are also possible including respirator/ventilator systems which dispense anesthetic. 
         [0066]    While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles. 
       APPENDIX 
     List of Reference Numbers 
       [0000]    
       
           1  First valve arrangement  21  Cap 
           2  Second valve arrangement  22  Fastening diameter 
           3  Third valve arrangement  23  Second valve element 
           4  Fourth valve arrangement  24  Support strut 
           5  First direction of flow  25  Horizontal axis 
           6  Second direction of flow  26  Contact elements 
           7  Passage opening  27  Contact bridge 
           8  Valve body  28  Third valve disk 
           9  First valve disk  29  Fastening axis 
           10  First valve element  30  Operating electronic unit 
           11  First valve seat  31  Terminal contact pair 
           12  Coil  32  Capacitor 
           13  Central axis  33  Protective resistor 
           14  First magnetic field line curve  34  A.c. voltage source 
           15  Second magnetic field line curve  35  Voltage measuring device 
           16  Second valve disk  36  Parallel resistor 
           17  Fastening hole  39  Metal element 
           18  Second valve seat  40  Mount 
           19  Holding structure  41  Groove 
           20  Fastening point 
           21  Cap 
           22  Fastening diameter 
           23  Second valve element 
           24  Support strut 
           25  Horizontal axis 
           26  Contact elements 
           27  Contact bridge 
           28  Third valve disk 
           29  Fastening axis 
           30  Operating electronic unit 
           31  Terminal contact pair 
           32  Capacitor 
           33  Protective resistor 
           34  A.c. voltage source 
           35  Voltage measuring device 
           36  Parallel resistor 
           39  Metal element 
           40  Mount 
           41  Groove

Technology Classification (CPC): 0