Patent Publication Number: US-2022233801-A1

Title: Nasal cannula with a better-secured connection to a supply line

Description:
The present invention concerns a patient therapeutic gas supply system, comprising a nasal cannula for the nasal supply of a patient with therapeutic gas, wherein the nasal cannula comprises: A cannula connector, and a therapeutic gas dispensing aperture for dispensing the therapeutic gas to the patient, wherein the nasal cannula defines a fluid conduit between the therapeutic gas dispensing aperture and the cannula connector; a therapeutic gas supply line for feeding therapeutic gas to the nasal cannula, wherein the therapeutic gas supply line exhibits a line connector which is set up so as to form a separable therapeutic gas-carrying connection in a connecting region with the cannula connector, wherein once the therapeutic gas-carrying connection has been established, the cannula connector and the line connector overlap along a section of a flow path proceeding through the connecting region; and a locking module, wherein the locking module is movable between a locked position and a released position, wherein when the locking module is in the locked position, a force needed for separating the connection between the cannula connector and the line connector is quantitatively larger than when the locking module is in the released position. 
     A flow path which is always a virtual flow path can be defined in this application through the path which connects the geometric centers of gravity of the cross-sections of the therapeutic gas-carrying regions, e.g. of the inner volume of a hose section and/or of the nasal cannula, of the patient therapeutic gas supply system along the flow movement. In particular, in case of doubt the flow path can be conceived as penetrating centrally through the therapeutic gas-carrying fluid conduits of the patient therapeutic gas supply system. 
     Patient therapeutic gas supply systems are described in this application in a state in which the therapeutic gas-carrying connection is formed, unless expressly described otherwise. 
     In addition, describing the directions relies on using the flow path for a flow path direction as a reference wherein a flow path direction proceeds in parallel or antiparallel to a direction vector describing a tangent of the flow path. A radial direction relative to the flow path should be understood as a direction which proceeds perpendicularly to a tangent of the flow path at a point of the flow path and points away from this point. A circumferential direction denotes a direction encircling the flow path or an axis. In the case of a curved flow path, this leads to a change in the flow path&#39;s direction, the radial direction, and the circumferential direction in a Cartesian coordinate system fixed relative to patient therapeutic gas supply system. 
     A patient therapeutic gas supply system as described above is known for example from the publication WO 2014/142681, there an embodiment of  FIGS. 15E to 15G . In this state of the art, the locking module is configured in the form of two tongues, each provided with a projection, which are configured at the line connector. If the line connector is plugged into the cannula connector, the projections engage behind an annular shoulder and impede the separating of the therapeutic gas-carrying connection. Due to the proximity of the annular shoulder to the projections carrying the therapeutic gas-dispensing aperture, however, it is cumbersome to separate the connection between the cannula connector and the line connector, since the user, e.g. the patient or the patient&#39;s caregiver, has to position his or her finger accurately on the nasal cannula in order to press the projections of both tongues inward while at the same time pulling the line connector away from the nasal cannula. This can, moreover, result in the tongues not being pressed inward deeply enough and the released position thereby inadvertently not reached. If an attempt is then made to separate the therapeutic gas-carrying connection, the nasal cannula can be unintentionally removed which can be very uncomfortable for the patient. 
     It is, therefore, the task of the present invention to provide a patient therapeutic gas supply system in which a separable and secure therapeutic gas-carrying connection can be configured. 
     This task is solved according to the invention by means of a patient therapeutic gas supply system of the type mentioned at the beginning, in which once the therapeutic gas-carrying connection has been made, the locking module is displaceable between the locked position and the released position relative to the cannula connector and to the line connector in such a way that it exhibits in the locked position a greater overlap with the connecting region than in the released position. Due to the greater overlap of the locking module with the connecting region, freedom of movement of the cannula connector and/or of the line connector is more strongly restricted in the connecting region in the locked position than in the released position, such that deformation of the cannula connector and/or of the line connector, which can lead to separating of the therapeutic gas-carrying connection, is counteracted such that the security of the therapeutic gas-carrying connection is enhanced. 
     Preferably, the locking module is located further out in the radial direction relative to the flow path than the cannula connector and the line connector. The overlap of the locking module with the connecting region then serves for the user as an indicator for the presence or absence of the locked position, whereby the frequency of misjudgments as to whether the locking module is in the locked position is decreased, which in turn simplifies separating the therapeutic gas-carrying connection. Furthermore, changing between the locked position and the released position by displacing the locking module allows the user to change over easily between the two positions. If the locking module is in the locked position, then due to the described forces needed for separating the therapeutic gas-carrying connection, an especially secure therapeutic gas-carrying connection is formed. 
     The connecting region can extend in the flow path direction beyond the region defined by the overlapping of the cannula connector and line connector. Preferably, the connecting region is only that region in which the cannula connector and line connector extend over a common flow path section, i.e. overlap. 
     In order to form the tightest possible therapeutic gas-carrying connection, both the line connector and the cannula connector each exhibit coupling sections completely encircling the flow path. This applies in particular to those connection sections of the line connector and cannula connector which overlap when forming the therapeutic gas-carrying connection. 
     In order to facilitate the making of a permanently tight therapeutic gas-carrying connection, preferably one connector out of the line connector and cannula connector is configured as a deformation connector with at least in the connection section lower stiffness against expansion in the radial direction than the respective other connector. The respective other connector consequently exhibits as a supporting connector, at least in its connection section, higher stiffness against deformation orthogonally to the flow path. 
     Preferably, the different stiffnesses are achieved by using materials with different modules of elasticity for the cannula connector and the line connector. In order to make the overlapping connection, the deformation connector can under radial expansion be pushed or pulled against its material elasticity over the supporting connector. When back in its relaxed shape under the pre-tensioning effected by its expansion deformation, the deformation connector then abuts on the supporting connector with a sealing effect. 
     Since the locking module is preferably arranged radially outside the line connector and cannula connector to facilitate actuation, the locking module arranged radially outside in this way can in addition act on the deformation connector located nearer to it radially so as to advantageously enhance the sealing effect and/or the connection strength between the line connector and cannula connector in the connecting region, for instance by exerting a mechanical force on the deformation connector that is thus directly accessible to the locking module. 
     Since the nasal cannula is or can come almost constantly in contact with the skin of the patient during therapeutic gas supply, preferably the cannula connector is the aforementioned deformation connector. 
     At this point let it be made clear that for configuring the separable therapeutic gas-carrying connection, a friction coupling and/or a positive-locking coupling and/or a firmly bonded coupling contributes to and/or is the connection. 
     In order to transmit forces across as large an area as possible to the connecting region, thus contributing to secure configuration of the therapeutic gas-carrying connection, the locking module surrounds the flow path at least section-wise in a circumferential direction, preferably completely in the circumferential direction. 
     In a preferred embodiment, the locking module is configured as separate from (i.e. not integral with) the cannula connector and the line connector. As a result, the material or materials of the locking module can be chosen independently from the materials of the cannula connector and of the line connector. In order to ensure proper operation of the patient therapeutic gas supply system, the locking module is installed misplacement-proof on the cannula connector or the line connector in at least one, preferably in both positions out of the locked position and released position. 
     In an especially preferred embodiment, when the locking module is in the locked position the locking module pre-tensions at least section-wise a connector out of the cannula connector and the line connector in the direction of the other connector out of the cannula connector and the line connector more strongly than when the locking module is in the released position. As a result, in the locked position there can act in the overlap region, in particular also due to the greater overlap of the locking module with the connecting region in the locked position of the locking module compared with the state of the locking module in the released position, a quantitatively greater force between two mutually abutting surfaces of the cannula connector and of the line connector than when the locking module is in the released position. A frictional force resulting from same between these two surfaces or a force resulting from same and counteracting a deformation of a connector out of the cannula connector or line connector has to be overcome when separating the therapeutic gas-carrying connection, which in a simple manner increases the force needed for separating the connection between the cannula connector and the line connector compared with the state in which the locking module is in the released position. 
     The locking module comprises a locking section, which when the locking module is in the locked position overlaps with the connecting region. The locking section can be the locking module. It is, however, preferable for the locking module in addition to the locking section to comprise a carrier section, which when the locking module is in the locked position does not overlap with the connecting region. Preferably the locking section and the carrier section are configured integrally. 
     The locking section can comprise a plurality of part-sections arranged around an axis penetrating through the connecting region, which are arranged in the circumferential direction around the axis spaced from one another and with preferably equal angles between neighboring part-sections around the axis. The axis preferably coincides with the flow path or one of its tangents or is at least configured parallel to one of these tangents. As a result, the weight of the locking module can be reduced. It is, however, preferable for the locking section to be configured as continuous in the circumferential direction. 
     The locking section can comprise a component U-shaped at least in one aspect, and/or a partly or completely closed reversibly deformable band and/or an essentially rigid annular element, such that a locking section matched to the constraints such as flexibility of the cannula section and/or of the duct section, spatial restrictions for the movement of the locking section etc. can be provided. 
     In order to contribute to the forming of a securely and safely manageable therapeutic gas-carrying connection, the patient therapeutic gas supply system can further comprise at least one positive-locking arrangement which exhibits a positive-locking formation configured at the line connector and a positive-locking counter-formation configured at the cannula connector, wherein the positive-locking formation at least contributes to the configuration of the separable therapeutic gas-carrying connection by forming positive locking between the positive-locking formation and the positive-locking counter-formation. As a result, in contrast to the presence of a therapeutic gas-carrying connection relying solely on friction coupling, a connection type can be provided which provides the user with tactile and/or acoustic feedback when forming or separating the positive locking, when for example the positive-locking formation interacts with the positive-locking counter-formation or is separated from the latter, such that the user can determine with enhanced certainty whether a therapeutic gas-carrying connection is made or separated. The positive-locking arrangement is preferably configured in the connecting region. 
     In the released position of the locking module there is preferably no overlap of the locking module and/or of the locking section with the connecting region and/or the positive-locking arrangement. 
     In order to secure the therapeutic gas-carrying connection more strongly against unintentional separating, the positive-locking arrangement can surround the flow path at least in part, preferably completely. 
     A pair of a positive-locking formation and a positive-locking counter-formation, which are at least part of the positive-locking arrangement or form the latter, can be a pair consisting of a groove and a spring, and/or a pair consisting of a projection and a recess, and/or a pair consisting of a claw and an edge which is engaged from behind by the claw, and/or a pair consisting of tooth systems engaging with one another, and/or a pair consisting of a pawl and a surface provided with retaining teeth, or a similar pair. 
     Preferably the positive-locking arrangement is so configured that when the locking module is in the released position, a displacement movement of a displacement section of the positive-locking formation or of the positive-locking counter-formation along a displacement path contributes to the separating of the positive locking. It is possible for the displacement movement of the displacement section to be accompanied by a deformation of the displacement section or its surroundings, which defines a displacement deformation. Impeding the displacement movement is understood to be any quantitative increase in a force needed for performing the displacement movement compared with performing the displacement movement without the conditions or features constituting the impeding. An at least partial prevention of the displacement movement is a special case of a greatest possible impeding of the displacement movement. Because of the facilitated deformability, the displacement section is preferably configured at the deformation connector. 
     In a preferred embodiment, at least one formation out of the positive-locking formation and the positive-locking counter-formation proceeds at least section-wise non-parallel to a normal plane of the flow path which normal plane intersects the one formation out of the positive-locking formation and the positive-locking counter-formation. This makes it possible for only one or a predetermined plurality of predetermined relative positions to be taken up between the cannula connector and the line connector when the therapeutic gas-carrying connection is made, and consequently the patient therapeutic gas supply system can in a straightforward manner by means of a thus configured indexing mechanism take up one or a plurality of predetermined arrangements comfortable for the patient. 
     In an especially preferred embodiment, the patient therapeutic gas supply system for securing the therapeutic gas-carrying connection further comprises a position-securing device, wherein in the locked position the locking module can be secured by means of a position-securing device against movement in the direction of the released position. Any impeding of a movement of the locking module from the locked position in the direction of the released position counts as securing. What has been said above about impeding the displacement movement, applies correspondingly to impeding the aforementioned movement of the locking module. Here it should be allowed for the locking module to exhibit backlash in the locked position, although backlash-free securing is preferred. 
     According to an advantageous further development, the position-securing device can be moveable between a secured position and a released position. Preferably when the locking module is in the locked position and the position-securing device is in the secured position, with the assistance of the position-securing device a physical barrier is formed which prevents movement of the locking module from the locked position to the released position. Moreover when the position-securing device is in the released position, the physical barrier formed with the assistance of the position-securing device impedes the movement of the locking module from the locked position to the released position less strongly than when the locking module is in the locked position and the position-securing device is in the secured position. Such a position-securing device in combination with the locking module reduces the likelihood of unintentional separating of the therapeutic gas-carrying connection more strongly than a patient therapeutic gas supply system with only a locking module since due to the impeding described above, in the secured position the position-securing device reduces the likelihood that the locking module is unintentionally moved from the locked position to the released position. 
     For straightforward, preferably self-activating securing of the locking module in the locked position, the position-securing device can comprise a snap-in arrangement with a snap-in projection which is pre-tensioned in the direction of a snap-in seat of the snap-in arrangement. 
     An extreme case of strong impeding when the locking module is in the locked position and the position-securing device is in the secured position, is the forming by means of the physical barrier of a barrier that cannot be overcome non-destructively. 
     A snap-in seat can be configured as a concave section of a surface, in particular as a material recess, an indentation, or a concave spatial section bounded by projections. 
     The physical barrier is preferably a barrier that can be overcome non-destructively. 
     In an especially simple configuration, the position-securing device comprises a snap-in arrangement with a snap-in element and a mating snap-in element. Again it is preferable that the snap-in arrangement forms a latching mechanism that can be overcome non-destructively. The snap-in arrangement can contribute to the forming of the physical barrier or form it. 
     In order to reduce the error-proneness of the effect of the snap-in arrangement, the snap-in element is arranged at a component out of the locking module and either the line connector or the cannula connector by means of an integral flexural hinge, wherein the mating snap-in element is arranged at the other component out of the locking module and either the line connector or the cannula connector, such that at least one element of the snap-in arrangement is arranged at the locking module and thus at the part to be secured. 
     The use of a integral flexural hinge for the arrangement of the snap-in element allows, due to the plurality of the degrees of freedom of motion provided by the integral flexural hinge, the forming of a coupling between the snap-in element and the mating snap-in element even when the parts carrying the integral flexural hinge and the mating snap-in element are situation in a position different from a required position for forming the coupling. 
     In an especially preferred embodiment, the integral flexural hinge, preferably the integral flexural hinge and the snap-in element, is configured as part of the locking module integrally with the locking module. This allows the locking module to be manufactured cost-effectively together with the integral flexural hinge and for example also with the snap-in element in a single step, for example in an injection-molding process. The integral flexural hinge can be configured as a flexible springy tongue with a material bridge to the rest of the locking module. The tongue can in particular be configured through the provision of at least one, preferably two, pass-through slots located in the circumferential direction on both sides of the tongue and proceeding in the flow path direction in a section of the locking module. 
     In order to further facilitate the handling of the patient therapeutic gas supply system, the patient therapeutic gas supply system can further comprise a pivot lever coupled with the locking module in such a way that by pivoting the pivot lever between a first pivoting region and a second pivoting region the locking module is moved between the locked position and the released position. The use of a pivot lever for effecting the movement of the locking module between the locked position and the released position simplifies, for one thing, the handling of the patient therapeutic gas supply system, and furthermore allows the user to recognize unambiguously whether the locking module is in the locked position or in the released position, depending on whether the pivot lever is in the first pivoting region or the second pivoting region. 
     The pivot lever can exhibit a dual function, in that additionally to the function just described as an actuation element it also exhibits a function as part of the position-securing device, in that e.g. the snap-in element is arranged at the pivot lever, wherein preferably the mating snap-in element is arranged at the locking module or a connector out of the line connector and the cannula connector. 
     In order to prevent possible tilting of the locking module during a movement between the locked position and the released position, or at least to reduce the likelihood of same, the patient therapeutic gas supply system comprises a guiding device fixed in place relative to a connector out of the line connector and the cannula connector, which is adapted to guide a movement of the locking module between the locked position and the released position and in particular to restrict it essentially to a translation. 
     In an especially preferred embodiment, the locking module comprises a closed annular element. As a result, due to the annular form, forces induced in the locking module in the locked position can be distributed symmetrically in the locking module which increases the stability of the locking module. The annular element can comprise or form the locking section. 
     In addition, it is possible for an annular sleeve of the annular element to exhibit at the front side, i.e. at the end side in the flow path direction, annular element end surfaces, preferably at least one or two annular element end planes, which in particular are each penetrated through by the flow path, and wherein at least one of the annular element end surfaces proceeds at least section-wise non-parallel to a normal plane of the flow path which normal plane intersects the at least one annular element end surface. Such construction allows in particular to match the annular element with the smallest possible material cost to the shape of a positive-locking formation proceeding non-parallel to a normal plane of the flow path between cannula connector or line connector as described above. Preferred are an inclination of the positive-locking formation towards the normal plane of the flow path and a inclination equal as regards magnitude and orientation of the at least one annular element end surface towards the same normal plane of the flow path. Preferably the two annular element end surfaces are parallel to one another. 
     It is further envisaged that an annular sleeve of the annular element exhibits at the front side, i.e. at the end side in the flow path direction, annular element end surfaces, preferably at least one or two annular element end planes, which in particular are each penetrated through by the flow path, and wherein the annular element end surfaces proceed at least section-wise non-parallel to one another. 
     Such construction allows, as described above, to guide the annular element along the positive-locking formation, and further allows to provide in the flow path direction a sufficiently large extension of the annular sleeve, at least section-wise with respect to the circumferential direction, in order to accommodate at least parts of functional groups, such as part of the position-securing device, in particular the integral flexural hinge or part of the snap-in device, without increasing the weight of the annular element unnecessarily. Each of these described functional groups can be arranged in a region of a maximum extension of the annular sleeve in the flow path direction, wherein a maximum extension of the annular sleeve in the flow path direction is preferably a genuine maximum extension of the annular sleeve in the flow path direction, such that at another place in the annular sleeve there also exists an extension of the annular sleeve in the flow path direction which is smaller than the maximum extension of the annular sleeve. 
    
    
     
       The invention will be elucidated below by reference to embodiments, with the help of the attached drawings. They show: 
         FIG. 1  An exploded view of a first embodiment of the present invention; 
         FIG. 2 a    A side-view of the first embodiment of the present invention from  FIG. 1 , wherein the locking module is in the released position and wherein parts of the therapeutic gas supply line have been omitted; 
         FIG. 2 b    A top view of the first embodiment of the present invention from  FIG. 1 , wherein the locking module is in the released position shown in  FIG. 2 a    and wherein parts of the therapeutic gas supply line have been omitted; 
         FIG. 2 c    The AA cross-section from  FIG. 2   b;    
         FIG. 3 a    A side-view of the first embodiment of the present invention from  FIG. 1 , wherein the locking module is in the locked position and wherein parts of the therapeutic gas supply line have been omitted; 
         FIG. 3 b    A top view of the second embodiment of the present invention from  FIG. 1 , wherein the locking module is in the in the locked position shown in  FIG. 3 a    and wherein parts of the therapeutic gas supply line have been omitted; 
         FIG. 3 c    The AA cross-section from  FIG. 3   b;    
         FIG. 4  An exploded view of a second embodiment of the present invention; 
         FIG. 5 a    A side-view of the second embodiment of the present invention from  FIG. 4 , wherein the locking module is in the released position and wherein parts of the therapeutic gas supply line have been omitted; 
         FIG. 5 b    A top view of the second embodiment of the present invention from  FIG. 4 , wherein the locking module is in the released position and wherein parts of the therapeutic gas supply line have been omitted; 
         FIG. 5 c    The AA cross-section from  FIG. 5   b;    
         FIG. 6 a    A side-view of the first embodiment of the present invention from  FIG. 4 , wherein the locking module is in the locked position and wherein parts of the therapeutic gas supply line have been omitted; 
         FIG. 6 b    A top view of the second embodiment of the present invention from  FIG. 4 , wherein the locking module is in the locked position and wherein parts of the therapeutic gas supply line have been omitted; and 
         FIG. 6 c    The AA cross-section from  FIG. 6   b.    
     
    
    
       FIG. 1  shows an embodiment according to the invention of a patient therapeutic gas supply system  20  in an exploded view. The patient therapeutic gas supply system  20  comprises a nasal cannula  22 , by means of which a patient is supplied with therapeutic gas, for example with air under pressure or with oxygen-enriched air under pressure. The nasal cannula  22  comprises a first cannula connector  24  and a first therapeutic gas-dispensing aperture  26 , which can be configured at a first projection  28  of the nasal cannula  22  and via which therapeutic gas is dispensed to the patient. The nasal cannula  22  is preferably configured mirror-symmetrically relative to a plane of symmetry  30  and preferably comprises accordingly due to the mirror symmetry a second cannula connector  32  and a second therapeutic gas-dispensing aperture  34  which can be configured at a second projection  36  of the nasal cannula  22 . In addition there can be provided at the nasal cannula  22  a patient-linking arrangement  38  for linking the nasal cannula  22  by means of a strap or a harness to the patient, comprising a first linking arm  40  and a second linking arm  42  and preferably configured mirror-symmetrically relative to the plane of symmetry  30 . Due to the mirror symmetry relative to the plane of symmetry  30 , in the following only one side R of the nasal cannula  22  will be described and the description should be applied analogously to the side L of the nasal cannula  22  configured mirror-symmetrically relative to the plane  30 . 
     Via a line connector  44  that will be described in detail later on of a therapeutic gas supply line  46  depicted in part by a dotted line of the patient therapeutic gas supply system  20 , therapeutic gas can be fed to the nasal cannula  22  via the first cannula connector  24 . In order to prevent the therapeutic gas escaping in an unregulated manner through the second cannula connector  32 , the latter is closed off with a plug  48 ; the plug  48  exhibits a gas-guiding surface in order to guide the therapeutic gas flow in the second projection  36  to the second therapeutic gas-dispensing aperture  34 , as described in more detail in German patent application DE 10 2018 122 516.4 which had not been released for publication at the filing date. Between the first cannula connector  24  and the two therapeutic gas apertures  26 ,  34  there is configured a branched fluid conduit  50 , wherein in  FIG. 2 c    a flow direction of the therapeutic gas is indicated by arrows SRl, SRr. 
     The therapeutic gas supply line  46  comprises preferably a hose  52 , which is connected to a source of the therapeutic gas at an end not shown, and which at its other end  54  is connected to the line connector  44  preferably via a threaded connector. At the line connector  44  there is arranged a moveable locking module  56  of the patient therapeutic gas supply system  20  formed separately from the former and from the nasal cannula  22  at two guiding projections  58 ,  60 , which engage with grooves  62 ,  64  configured as complementary in the locking module  56 . The guiding projections  58 ,  60  and the grooves  62 ,  64  form a guiding device, which guides the movement of the locking module  56  essentially linearly. 
     The line connector  44  comprises a supporting section  66 , at which a groove  68  completely encircling a therapeutic gas-carrying internal space section is configured. At the center of the therapeutic gas-carrying internal space, the therapeutic gas flows from the therapeutic gas source in the direction of the nasal cannula  22  along a flow path sub-path SP 1 , which in the depicted embodiment can be described inside the line connector  44  by a straight line. The groove  68  does not proceed in a plane which is arranged perpendicularly to the flow path sub-path SP 1 , but instead its part-regions proceed along a plurality of surfaces F 1  to F 3 , preferably planes F 1  to F 3 , each of which is indicated in  FIG. 1 . The surfaces F 1  and F 2  and the surfaces F 2  and F 3  each intersect and none of the surfaces F 1  to F 3  proceeds in a plane or parallel to a plane which is arranged perpendicularly to the sub-path SP 1  (normal plane to SP 1 ). 
     At the first cannula connector  24  there is configured a projection  70  protruding inward, which completely encircles a therapeutic gas-carrying internal space section of the first cannula connector  24 , in particular a sub-path SP 2  in this internal space section, which in the depicted embodiment can be described by a straight line. With the therapeutic gas-carrying connection  74  made, the sub-path SP 2  overlays the sub-path SP 1  in an overlap region  76  of the cannula connector  22  and the line connector  44 . As shown in  FIG. 3 c   , through this overlaying a flow path SP is defined which consists of the sub-path SP 2  and the sub-path SP 1 . The projection  70  is preferably configured as complementary to the groove  68 . 
     The nasal cannula  22  is preferably made from a soft elastic silicone material, whose module of elasticity is smaller than that of the synthetic material from which preferably the line connector  44  is made. 
       FIGS. 2 a -2 c  and 3 a -3 c    show the patient therapeutic gas supply system  20  in a state in which a therapeutic gas-carrying connection  74  between the first cannula connector  24  and the line connector  44  has been made. In order to make the therapeutic gas-carrying connection  74 , the supporting section  66  is inserted into the first cannula connector  24  until the projection  70  as a positive-locking formation snaps into the groove  68  as a positive-locking counter-formation, whereby positive locking of a positive-locking arrangement  78  comprising the groove  68  and the projection  70  is produced. 
     With a suitable choice of the surfaces F 1  to F 3 , there can be configured at the line connector  44  in a marginal section of the groove  68  a nose  79  protruding outwards beyond the supporting section  66  in a radial direction relative to the sub-path SP 1 , which when the therapeutic gas-carrying connection  74  has been made protrudes in a direction parallel to the flow path SP into a recess  80  formed complementarily in cannula connector  24 . Both the choice of the surfaces F 1 -F 3  and the configuration of the nose  79  and of the recess  80  define an orientation of the nasal cannula  22  relative to the line connector  44 , thus forming at least part of an indexing device. 
     With the therapeutic gas-carrying connection  74  made, the cannula connector  24  and the line connector  44  overlap in a connecting region  82 . This region is depicted schematically in  FIG. 3 c    bounded by a dashed line. 
       FIG. 2 c    shows that in a released position, the locking module  56  preferably exhibits no overlap with the connecting region  82 , whereas in a locked position shown in  FIG. 3 c    the locking module  56  exhibits an overlap with the connecting region  82 , which in particular is greater than a possible overlap with the connecting region  82  which can exist when the locking module  56  is in the released position. The flow path SP can be defined also outside the connecting region  82 . 
     If the therapeutic gas-carrying connection  74  is made, then as described above the flow path sub-paths SP 1  and SP 2  coincide in their overlap region and define in the connecting region  82  in particular the flow path SP, along which the cannula connector  24  and the line connector  44  overlap in the connecting region  82 . The statements made about each of the flow path sub-paths SP 1  and SP 2  apply correspondingly to the flow path SP. 
     It is preferred especially that in the locked position of the locking module  56  a locking section  84  of the locking module  56  overlaps the positive-locking arrangement  78 , this region is depicted schematically in  FIG. 3 a    bounded by a dashed line. Adjacent to the locking section  84 , the locking module  56  comprises a carrier section  85 , which when the locking module  56  is in the locked position does not overlap with the connecting region. 
     The locking module  56  can be moved through a relocation, preferably a translation, in a direction X defined by an orientation of the projections  58 ,  60  from the released position shown in  FIG. 2 c    into the locked position shown in  FIG. 3 c    and can be moved through a relocation, preferably a translation, in an opposite direction −X, which again is defined by the orientation of the projections  58 ,  60  from the locked position shown in  FIG. 3 c    into the released position. 
     If the locking module  56  is in the released position and if the nasal cannula  22  is pulled in the direction X and the duct section  44  is pulled in the direction −X, the positive locking formed by the positive-locking arrangement  78  is separated as soon as due to the stretchability of the cannula connector  24  a displacement movement V and/or displacement deformation respectively along a displacement path VP of the projection  70  has moved the projection  70  so far out of the groove  68  that the cannula connector  24  can be separated from the line connector  44 , wherein a section of the projection  70  relocated by the displacement movement V forms a displacement section. Consequently, the force needed for separating the cannula connector  24  from the line connector  44  has to overcome the frictional force acting between these two connectors and furthermore provide a force which is induced in the positive-locking arrangement  78  in order to effect the aforementioned displacement movement and/or displacement deformation respectively of the projection  70 . In particular, during the displacement movement material of the cannula connector  24  can escape radially outward relative to the flow path SP into a displacement space  86  when the locking module  56  is in the released position. 
     If the locking module  56  is in the locked position and if the nasal cannula  22  is pulled in the direction X and the duct section  44  is pulled in the direction −X, then at least part of the displacement space  86  is occupied by the locking section  84 . Furthermore, the locking section  84  can be configured in the direction of the flow path SP, tapering away from the nasal cannula  22  or with a projection facing radially inwards, such that in the locked position the locking section  84  pre-tensions material of the cannula connector  24  abutting on the line connector  44  in the direction towards the line connector  44  and thus, compared with the released position, contributes to the presence of a quantitatively greater frictional force between the cannula connector  24  and the line connector  44 . If the therapeutic gas-carrying connection  74  is separated when the locking module  56  thus configured is in the locked position, then due to the presence of this increased frictional force, the force required for same is greater than when the locking module  56  is in the released position. 
     Furthermore, material of the cannula connector  24 , which when the locking module  56  is in the released position moves into the displacement space  86  during the separating of the therapeutic gas-carrying connection  74 , can perform this displacement movement only at least incompletely, since the displacement space  86  is occupied at least in part by the locking section  84 . For separating the therapeutic gas-carrying connection  74 , the material of the positive-locking arrangement  78  and/or of the locking section  84  has to be deformed more strongly by stretching until the projection  70  has moved so far out of the groove  68  that the positive-locking arrangement  78  is separated. If this stretching is effected by a force which is effected by pulling the nasal cannula  22  in the direction X and pulling the line connector  44  in the direction −X, then due to the chosen geometry and the chosen materials this force is quantitatively greater than in the case where the locking module  56  is in the released position. 
     If the locking module  56  is situated in the locked position, this constitutes stronger impeding of the displacement movement compared with the case where the locking module  56  is in the released position, since either an additional force has to be exerted in order to deform the material of the locking section  84 , in case the displacement movement is carried out completely, or the displacement movement is not carried out completely, which is a special form of impeding the displacement movement. 
     In order to prevent the locking module  56  exiting the locked position unintentionally, the patient therapeutic gas supply system  20  preferably comprises a position-securing device  88 , which comprises a snap-in element configured as a projection  90 , which preferably is arranged at a springy tongue  92  forming an integral flexural hinge, and a mating snap-in element configured as a snap-in seat  94 . The snap-in element and the mating snap-in element are each part of a snap-in arrangement of the position-securing device  88 . 
     The tongue  92  is configured together with the projection  90  integrally with the locking module  56 , wherein in the locking module  56  two pass-through slots  96 ,  98  are configured in order to allow a bending movement of the tongue  92  and to define its contour at least in part. The snap-in seat  94  is preferably arranged at the line connector  44  and can be configured as a recess, facing radially inward relative to the flow path SP, between two projections  100 ,  102  spaced apart from each other and arranged at the line connector  44 . Each of the projections  100 ,  102  exhibits a flank  100   a ,  102   a  facing towards the other projection and arranged respectively in a normal plane to the flow path SP and a flank  100   b ,  102   b  facing away from the other projection which meet an outer surface of the line connector  44  at an angle different from 90°. 
     The position-securing device  88  is movable between a secured position and a released position. If the locking module  56  is in the locked position and the projection  90  is situated in the snap-in seat  94  between the two projections  100 ,  102 , the position-securing device  88  is in the secured position, whereby the projection  90  is pre-tensioned by the tongue  92  in the position in which the tip of the projection  90  is situated radially further inward relative to the flow path SP than the tip of the projection  100 , preferably than the tips of both projections  100 ,  102 . In the secured position, the projection  100  forms for the projection  90 , which is configured integrally with the locking module  56 , a physical barrier which can be overcome through a movement of the locking module  56  in the direction −X accompanied by deformation of the tongue  92 , when a bevel  90   a  of the projection  90  slides up the projection  100 . Once the projection  90  has reached with its tip the tip of the projection  100  during a further movement of the locking module  56  in the direction −X, then the projection  90  slides down the flank  100   b . If the projection  90  is situated beyond the flank  100   b  in the direction −X, in the region  104 , then given appropriately chosen dimensioning of the projection  90 , optionally only a frictional force acting through the aforementioned pre-tensioning counteracts a movement of the locking module  56  in the direction −X, wherein due the choice of the pre-tensioning and of the module of elasticity of the tongue  92  this frictional force is smaller than the force needed in order to let the bevel  90   a  of the projection  90  slide up the projection  100 . The released position of the position-securing device  88  is reached when the projection  90  has been displaced by a user radially outward relative to the flow path SP so far that neither of the projections  100 ,  102  interferes in a movement path of the projection  90  in the direction X or −X, such that the elements which form the physical barrier described above in the secured position of the position-securing device  88  do not impact, in particular do not impede, the movement of the locking module  56 . In particular, the released position of the locking module  56  is reached when the end  106  of the tongue  92  pointing in the direction −X has reached an end of the region  104  facing away from the snap-in seat  94 . 
     If the projection  90  is situated in the snap-in seat  94 , the locking module  56  cannot without an excessive force action separate itself from the patient therapeutic gas supply system  20 . If the projection  90  is situated to the right of the projection  100  as shown in  FIG. 2 c    in this view, then an abutting on the flank  102   b  of a section  108  of the locking module  56  protruding inwards in the radial direction vis-à-vis the positioning of the lug  92  relative to the flow path SP prevents further movement of the locking module  56  in the direction −X. The arrangement of projections thus chosen allows loss-proof arrangement of the locking module  56  at the duct section  44 . 
     The locking module  56  is configured in the embodiment example as a closed annular element surrounding the flow path SP with an annular sleeve  112  which comprises two end-face annular sleeve end planes  114  and  116 , which are each penetrated through by the flow path SP. The annular sleeve end planes  114 ,  116  are not aligned parallel to one another and the annular sleeve end plane  114  is not arranged perpendicular to the flow path SP, such that the annular sleeve end plane  114  cannot be arranged parallel to an arbitrary normal plane of the straight-line-configured flow path SP. The lug  92  is preferably arranged in an extension region  110  of the annular sleeve  112 , which exhibits a maximum extension of the annular sleeve  112  in a flow path direction. 
     A second embodiment of the present invention is described below by reference to  FIGS. 4 to 6   c , wherein only the differences relative to the first embodiment are discussed. 
     Parts, sections, regions, directions, etc. which in the second embodiment correspond to those in first embodiment, are labelled with a reference number increased by 1000 and an explicit reference is made to the associated description of the first embodiment, which should also be used for describing the second embodiment as regards the corresponding parts, sections, regions, directions, etc. The reference numbers SP, SP 1 , and SP 2  are also used in the description of the second embodiment and denote paths corresponding to those in the first embodiment, with the same applying to the directions X, −X, the directional information L, R, the arrows SRl, SRr, the displacement path VP, and the displacement movement V. New reference numbers of the second embodiment start at  1200 . 
     The main differences in second embodiment relative to the first embodiment are the provision of a pivot lever  1200 , the configuration of the position-securing device  1202  and the resulting dissimilarities in the design of the line connector  1204 , and the locking module  1206 . 
     The line connector  1204  exhibits two preferably parallel lugs  1210   a ,  1210   b  each provided with an aperture  1208   a ,  1208   b , wherein the apertures  1208   a ,  1208   b  are preferably oriented in alignment. At each of the lugs  1210   a ,  1210   b  there is preferably provided respectively a lead-in chamfer  1212   a ,  1212   b  leading to the associated aperture  1208   a ,  1208   b . The pivot lever  1200  is mounted pivotably in the apertures  1208   a ,  1208   b  on an axis  1216  preferably formed by two pin sections  1214   a ,  1214   b . The locking module  1206  is preferably configured as a closed annular element surrounding the flow path SP, whose annular sleeve  1112  extends between the end-face annular sleeve end planes  1114  and  1116 . In an extension region  1110  which exhibits a maximum extension of the annular sleeve  1112  in the flow path direction, there is arranged a bridge  1218 . A contour of the bridge  1218  is preferably defined by two pass-through slots  1220 ,  1222  in the circumferential direction relative to the flow path SP. In the bridge there is provided a pass-through slot  1224  along an extension direction of the bridge  1218  preferably parallel to the flow path SP, in which an actuation bridge  1226  and a latching bridge  1228  are arranged movement-proof relative to the bridge  1218 . The actuation bridge  1226  and the latching bridge  1228  both extend preferably in a direction transverse to the extension direction of the bridge  1218 . Between the actuation bridge  1226  and a blind end  1230  of the pass-through slot  1224  there is provided an accommodating space  1232 . 
     The pivot lever  1200  preferably exhibits an engagement section  1234  for operating by the user and an actuation section  1236 , wherein the axis  1216  preferably proceeds through a boundary between the engagement section  1234  and the actuation section  1236 . In order to connect the line connector  1204  with the locking module  1206  and the pivot lever  1200 , first the locking module  1206  is pushed onto the line connector  1204  starting from the side of the supporting section  1066 , such that the bridge  1218  comes to lie between the lugs  1210   a ,  1210   b . Then the pin sections  1214   a ,  1214   b  of the pivot lever  1200  are placed at assigned lead-in chamfers  1212   a ,  1212   b , wherein the actuation section  1236  points in the direction towards the nasal cannula  1022 . The pivot lever  1200  is moved relative to the flow path SP in a direction oriented radially inward, until the pin sections  1214   a ,  1214   b  slide into the assigned apertures  1208   a ,  1208   b  at assigned lead-in chamfers  1212   a ,  1212   b , wherein preferably the actuation section  1236  engages in the accommodating space  1232 , as shown in  FIG. 5   c.    
     For the following angular details, a reference plane  1240  proceeding in parallel to the underside  1238  of the pivot lever  1200  and intersecting the axis  1216  can be used, which in the drawings is indicated by a line. If the reference plane  1240  is in a first pivoting region defined by the angular region α 1 , as depicted in  FIG. 5 a   , then no or only a small overlap of the locking section  1084  and the positive-locking arrangement  1078  is present, as can be discerned in the depiction in  FIG. 5 c   . If the pivot lever  1200  is pivoted in the pivoting direction  1242  until the reference plane  1240  is situated in the angular region α 2  and thus in a second pivoting region, then first during this pivoting a flank  1244  of the actuation section  1236  facing towards the nasal cannula  1022  in  FIG. 5 b    engages with an inner surface of the blind end  1230  and displaces the locking module  1206  from the released position shown in  FIG. 5 c    in the direction of the locked position shown in  FIG. 6 c   , and a first projection  1246  protruding at the pivot lever  1200  engages with the actuation bridge  1226  and pushes over the latter in the further course of the pivoting movement, during which the reference plane  1240  is pivoted into the angular region α 2 , the locking module  1206  into the locked position show in  FIG. 6 c   . If the pivot lever  1200  is pivoted from the position shown in  FIG. 6 c    and defined by the position of the reference plane  1240  in the angular region α 2  against the pivoting direction  1242 , then a flank  1248  of the actuation section  1236  facing away from the nasal cannula  1022  engages at the actuation bridge  1226  and displaces the locking module  1206  in the direction of the released position shown in  FIG. 5 c   , which preferably is not reached before the reference plane  1240  is situated in the angular region α 1 . Through the described interaction of the actuation section  1236  with the actuation bridge  1226  and the inner surface of the blind end  1230 , a coupling of the pivot lever  1200  with the locking module  1206  is described. The locked position of the locking module  1206  is preferably not reached before the reference plane  1240  is situated in the angular region α 2 . 
     Each of the angular regions α 1  and α 2  exhibits preferably an angular width of 15° or less. 
     The position-securing device  1202  comprises the latching bridge  1228  as a snap-in element of a snap-in arrangement, the first projection  1246 , and a second projection  1250  protruding at the pivot lever  1200  in the same direction as the first projection  1246 , which together form a mating snap-in element of the snap-in arrangement of the position-securing device  1202  assigned to the snap-in element. Preferably, the latching bridge  1228  can only enter the interspace configured between the projections  1246  and  1250  on deformation of one of these projections  1246  and  1250 . It is further preferable that as soon as the latching bridge  1228  has entered the interspace between the projections  1246  and  1250 , each of the projections  1246  and  1250  takes up again its original position, such that the latching bridge  1228  snaps in or latches in between the projections  1246  and  1250 . Accordingly, the pivot lever  1200  is secured in the position shown in  FIG. 6 c    through the described latching mechanism against unintentional rotation opposite to the pivoting direction  1242 , which in turn secures the locking module  1206  in the locked position against movement in the direction of the released position due to the engagement of the pivot lever with the line connector  1204  and with the locking module  1206 . The position-securing device  1202  further comprises the pivot lever  1200 . In the position of the pivot lever  1200  shown in  FIG. 6 c   , the position-securing device  1202  is in the secured position, since via the engagement with the apertures  1208   a ,  1208   b  and the engagement with the latching bridge  1228 , the pivot lever  1200  forms a physical barrier between the locking module  1206  and the line connector  1206  which cannot be overcome without pivoting or destruction of the pivot lever  1200  or its engagement points with the latching bridge  1228  or the apertures  1208   a ,  1208   b , such that the locking module  1206  cannot be moved into the released position. This is an extreme case of strong impairment of the movement of the locking module  1206  from the locked position to the released position. 
     If the pivot lever  1200  is pivoted opposite to the pivoting direction  1242  when overcoming the securing force provided by the latching mechanism of the projections  1246  and  1250  at the latching bridge  1228  and the latching mechanism of the projections  1246  and  1250  at the latching bridge  1228  is released, the pivot lever  1200  impedes the movement of the locking module  1206  in the direction of the released position less strongly, since essentially other than a negligible frictional force induced by the rotation of the pin sections  1214   a ,  1214   b  in the apertures  1208   a ,  1208   b  which has to be overcome during the movement of the locking module  1206  in the direction of the released position of the locking module  1206 , the position-securing device  1202  does not create a force acting against movement of the locking module  1206  in the direction of the released position. The force acting on the locking module  1206  that is needed for overcoming the frictional force described here is quantitatively smaller than the force needed for destructive overcoming of the physical barrier provided by the pivot lever  1200  via the engagement with the apertures  1208   a ,  1208   b  and the engagement with the latching bridge  1228 . In order to determine the forces acting on the locking module  1206 , in an adequately good approximation, the pivot lever  1200  can be removed from the apertures  1208   a ,  1208   b  and the forces can be measured sufficiently accurately at a thus modified locking module  1206 . 
     Via the latching of the latching bridge  1228  at the projections  1246  and  1250  and the arrangement of the actuation section  1236  in the accommodating space  1232 , which optionally cannot be present at the same time, the locking module  1206  is arranged loss-proof at the line connector  1206 .