Patent Publication Number: US-2021162151-A1

Title: Respiratory flow sensor

Description:
FIELD OF INVENTION 
     The invention relates to a respiratory flow sensor according to the preamble of claim  1  or  18 . 
     BACKGROUND 
     Respiratory flow sensors, also referred to as differential pressure flow sensors, flow measuring sensors or flow sensors, are arranged between a tube, which comes from a respiratory or anesthetic device, and a tube, which is supplied to the patient. 
     A respiratory flow sensor comprising a flow pipe, comprising a cover flap and comprising connections, is known from U.S. Pat. No. 5,979,247A. The flow pipe has a cylindrical flow channel and, on the free ends thereof, hose connections for the hoses. The cover flap is arranged in the flow channel and divides the flow channel into a first flow channel section and into a second flow channel section. The cover flap further has a hinge region and a free end region located opposite the hinge region. The hinge region is formed by a first slot and by a second slot, wherein the second slot is arranged between the first slot. On both sides of the cover flap, the connections lead into the flow channel and serve for the reduction of the differential pressure created by the cover flap. 
     If air or the breath, respectively, of the patient forms the respiratory flow sensor, the deflectable cover flap forms a flow resistance. For a reliable use, a respiratory flow sensor needs to have a sufficient measurement accuracy. High differential pressures appear in the respiratory flow sensor, in particular in the case of a respiratory flow sensor for children, which has a relatively small diameter of the flow channel. Even small influences thus have a large effect on the result of a measurement, which is carried out. 
     The breathing air of the patient also includes moisture, which deposits as liquid in the flow channel of the respiratory flow sensor during the respiration. This liquid can lead to a measurement noise on the useful signal and can thus cause an inaccurate measurement. The liquid located in the respiratory flow sensor can also have the effect that the result of this measurement is greatly distorted, because the characteristic of the cover flap changes as a result of an liquid application. As a result of a high liquid level in the flow channel, the mobility or the deflectability of the cover flap can further be greatly impacted. These effects appear in particular when the liquid collects in a region of the flow channel, in which the cover flap is arranged. 
     It has now already been proposed to arrange the respiratory flow sensor between the hoses in such a way in each case that said respiratory flow sensor comes to rest in an inclined orientation and that the liquid, which is located in the respiratory flow sensor due to the force of gravity, can drain. However, the patient often moves during the duration of a respiration process or during an anesthesia. The respiratory flow sensor, which is arranged at an incline, might thus come into a position, in which a water drainage of the respiratory flow sensor does not take place any longer and a sufficient measurement accuracy is thus no longer ensured. 
     In the case of a respiratory flow sensor, it is known from US200701313279A1 to provide drainage pipes, which can in each case be closed by means of a valve and which protrudes perpendicularly to the outside, on both sides of a stationary flow resistance. 
     The construction of this type of water drainage is extensive and leads to correspondingly high production costs for the respiratory flow sensor. Such respiratory flow sensors, however, are often disposable parts, so that the production costs are to be kept as low as possible. 
     Due to the hinge region of the cover flap, which comprises to joint regions or hinges, respectively, which are spaced apart from one another, the cover flap according to U.S. Pat. No. 5,979,247A is subjected to torsional stresses only to a limited extent, in particular in the case of high respiratory flows. After a certain period of use, however, breakages, which can also lead to inaccurate measurement results, occur again and again in this hinge region. 
     A respiratory flow sensor comprising a flow pipe, comprising a cover flap and comprising connections, is known from DE19617738C1. The flow pipe has a flow channel, which has a rectangular cross section and, on the free end thereof, has hose connections for hoses. The cover flap is arranged into the flow channel and divides the flow channel into a first flow channel section and into a second flow channel section. The cover flap further has a hinge region and a free end region located opposite the hinge region. The hinge region is formed by a first slot and by a second slot, wherein the second slot is arranged between the first slot. On both sides of the cover flap, the connections lead into the flow channel and serve for the reduction of the differential pressure created by the cover flap. 
     In the case of a respiratory flow sensor according to DE19617738C1, liquid can also collect in the flow channel and breakages occur again and again in the hinge region of the cover flap after a certain period of use. 
     A respiratory flow sensor is known from U.S. Pat. No. 4,989,456A, which has a flow pipe, which has a flow channel and, on the free ends thereof, hose connections for hoses, a cover flap, which is arranged in the flow channel and which divides the flow channel into a first flow channel section and into a second flow channel section, and has connections, which lead into the flow channel on both sides of the cover flap and serve for the reduction of the differential pressure created by the cover flap. Provision is made in the flow channel for two annularly running accommodating chambers as water draining device of the respiratory flow sensor. Moisture, which accumulates in the respiratory flow sensor, is collected in these accommodating chambers. 
     It is a disadvantage of this known solution that the moisture, which accumulates during the entire measuring process, is still located in the respiratory flow sensor and distortions of the measurement results can also result caused by moisture depositions. Depending on the orientation of the respiratory flow sensor, liquid located in the accommodating chamber can also escape unintentionally. 
     The cover flap of U.S. Pat. No. 4,989,456A has hinges, which are formed by slots, which run in opposite directions. This embodiment prevents breakages in the hinge regions only to a limited extent during a longer period of use. 
     EP2275783A2 shows a respiratory flow sensor comprising a cover flap, the hinge region of which has a plurality of slots, which are arranged parallel to one another. 
     The disadvantage of this solution is that unwanted deflection movements of the cover flap can occur under pressure due to this embodiment of the hinge region in particular in the case of respiratory flow sensors with smaller dimensions, as they are used for the respiration and anesthesia of children. This can go so far that the cover flap starts to flutter. If the material thickness of the cover flap is reinforced in such a way that unwanted deflection movements of the cover flap are prevented for the most part, this makes the measurement per se more difficult. 
     SUMMARY 
     It is thus the object of the invention at hand to create a respiratory flow sensor, which does not have the above-mentioned disadvantages and which in particular ensures a sufficient measurement accuracy in response to a long period of use. 
     The object is solved by means of the features of the independent claims. Advantageous further developments are specified in the figures and in the dependent patent claims. 
     According to a first approach of the invention, a respiratory flow sensor has a flow pipe, which has a flow channel and, on the free ends thereof, hose connections for hoses, a cover flap, which is arranged in the flow channel and which divides the flow channel into a first flow channel section and into a second flow channel section, and connections, which lead into the flow channel on both sides of the cover flap and serve for the reduction of the differential pressure created by the cover flap, wherein provision is made in the flow channel for a water drainage device, which comprises at least one drainage groove. 
     Moisture, which accumulates in the flow channel, drains in the at least one drainage groove for example and/or said moisture can collect in the at least one drainage groove. As an alternative or in addition to a drainage of the liquid, the maximum level of the liquid in the respiratory flow sensor is limited in the flow channel by this type of water drainage device. The water drainage device in the flow channel, which comprises at least one drainage groove, thus ensures that the liquid, which is located in the respiratory flow sensor, does not impact the deflection or the movement, respectively, of the cover flap, and that the liquid, which is located in the respiratory flow sensor, thus does not lead to distorted measurement results. 
     Advantageously, the at least one drainage groove extends in the flow-through direction of the respiratory flow sensor or the flow channel thereof, respectively, whereby a cumulative accumulation of liquid in the respiratory flow sensor and in particular in the region of the cover flap, is prevented in a preferred manner. 
     Advantageously, the at least one drainage groove is embodied in a channel-shaped manner and has for example a rectangular, U-shaped and/or V-shaped cross section. 
     The water drainage device preferably comprises a plurality of drainage grooves, so that the wall of the flow channel is not weakened excessively in the region of the drainage grooves in spite of the provision of a sufficiently large volume for accommodating liquid. 
     Advantageously, the drainage grooves are arranged so as to be spaced apart from one another in the circumferential direction, so that they are optimally arranged for a collection or drainage, respectively, or discharge of the liquid. In response to a rotation of the respiratory flow sensor about its flow-through axis, at least one drainage groove is thus also present for the collection or for the discharge, respectively, of the liquid. 
     The plurality of drainage grooves are preferably arranged along a region of the inner circumference of the flow channel, which extends maximally across half of the entire inner circumference of the flow channel. Based on the cross section of the flow channel, the region comprising the drainage grooves extends across maximally 180° of a full circle with 360°. With this arrangement of the plurality of drainage grooves, at least one drainage groove for the collection or for the discharge, respectively, of the liquid is always present in response to a rotation of the respiratory flow sensor about its flow-through axis in the common application. 
     The distances of the plurality of drainage grooves relative to one another are preferably different along the region of the inner circumference, which provides for an advantageous collection or discharge, respectively, of the liquid in the respiratory flow sensor. 
     Advantageously, the angular range of the outermost drainage grooves to the drainage grooves adjacent thereto, is larger than from the inner drainage grooves relative to one another. During the respiration or during the anesthesia, respectively, the respiratory flow sensor typically rotates about the flow-through axis only across a small angular range. As a result of the arrangement of the inner drainage grooves closer to one another, a sufficiently large volume for accommodating or draining, respectively, the liquid is available in the case of a common application of the respiratory flow sensor and based on the force of gravity. 
     Starting at the closure cap, the at least one drainage groove preferably runs in a direction of the corresponding free end of the flow pipe along a curved line, so that an advantageous drainage or discharge of the liquid is at hand due to the force of gravity. Starting at the closure cap, in the alternative, the at least one drainage groove runs in a direction of the corresponding free end of the flow pipe along an inclined surface, which is arranged at an angle to the flow-through axis of the flow channel. 
     In the region of the water drainage device, at least one flow channel section preferably runs in a curved manner, so that an advantageous drainage or discharge of the liquid is at hand by means of the force of gravity. 
     Starting at the cover flap, the cross section of at least one flow channel section in the region of the water drainage device preferably increases in a direction of the corresponding free end of the flow pipe, so that a drainage or discharge of the liquid is at hand by means of the force of gravity. Advantageously, the flow channel section increases across its entire circumference, so that the relative position of the respiratory flow sensor with regard to the flow-through axis of the flow channel has no impact. 
     The increasing flow channel section is preferably embodied in a trumpet-shaped manner, which provides for a simple production with simultaneously advantageous drainage or discharge of the liquid. In the alternative, the increasing flow channel section is embodied conically. 
     According to a further advantageous approach, a respiratory flow sensor has a flow pipe, which has a flow channel and, on the free ends thereof, hose connections for hoses, a cover flap, which is arranged in the flow channel and which divides the flow channel into a first flow channel section and into a second flow channel section, wherein the cover flap has a hinge region and a free end region located opposite the hinge region, and connections, which lead into the flow channel on both sides of the cover flap and serve for the reduction of the differential pressure created by the cover flap, wherein provision is made in the flow channel for at least one stop section for the free end region of the cover flap for the limitation of the deflection of the cover flap. 
     The at least one stop section limits the maximum deflection of the cover flap, whereby the latter and thus the respiratory flow sensor is more suitable for use as compared to the solutions known from the relevant prior art. 
     In the case of the stop section, provision is advantageously made in the case of the stop section for a water drainage device for the liquid, which accumulates in the respiratory flow sensor, e.g. in the form of at least one drainage groove or a collection tank. 
     Provision is further preferably made in the flow channel for two stop sections located opposite one another, for defining the deflection of the cover flap in both directions, whereby the suitability for use of the respiratory flow sensor is improved additionally, because the cover flap can pivot only across the region, which is defined by the distance of the stop sections relative to one another. 
     Provision is advantageously made between the two stop sections for a water drainage device for the liquid, which accumulates in the respiratory flow sensor, e.g. in the form of a collection tank. 
     According to a further approach of the invention, a respiratory flow sensor has a flow pipe, which has a flow channel and, on the free ends thereof, hose connections for hoses, a cover flap, which is arranged in the flow channel and which divides the flow channel into a first flow channel section and into a second flow channel section, wherein the cover flap has a hinge region, which is formed by a first slot and at least a second slot, and connections, which lead into the flow channel on both sides of the cover flap and serve for the reduction of the differential pressure created by the cover flap, wherein the at least one second slot of the hinge region of the cover flap is embodied in an H-shaped manner and provision is in each case made adjacent to the at least one second slot for one lateral slot each. 
     This embodiment of the slots does not only prevent a torsional movement of the cover flap in response to high respiratory flows, but ensures a high safety against a rupturing of the cover flap in the hinge region thereof. With a high measurement accuracy, this respiratory flow sensor according to the invention thus has a long suitability for use. The cover flap advantageously has a polygonal and/or axially symmetrical cross section. 
     The ends of at least the at least one second slot preferably have inclined surfaces or radii, whereby stress peaks in response to the deflection of the cover flap in these regions of the slots is reduced and the suitability for use of the cover flap and thus of the entire respiratory flow sensor is improved. Advantageously, all ends of the slots in the cover flap are provided with inclined surfaces or radii. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further advantages, features and details of the invention follow from the description below, in which exemplary embodiments of the invention are described with reference to the drawings. 
       The list of reference numerals as well as the technical content of the patent claims and figures is part of the disclosure. The figures are described cohesively and comprehensively. Identical reference numerals mean identical components, reference numerals with different indices specify functionally identical or similar components. 
         FIG. 1  shows a respiratory flow sensor according to the invention in a perspective view, 
         FIG. 2  shows the respiratory flow sensor according to  FIG. 1  in an exploded illustration, 
         FIG. 3  shows a schematic longitudinal section through a respiratory flow sensor according to the invention, 
         FIG. 4A-D  in each case shows the respiratory flow sensor according to  FIG. 3  in cross section, 
         FIG. 5  shows a schematic longitudinal section though an alternative according to the invention of the respiratory flow sensor according to  FIG. 3 , 
         FIG. 6  shows a schematic longitudinal section through a further alternative according to the invention of the respiratory flow sensor according to  FIG. 3 , 
         FIG. 7  shows a respiratory flow sensor in a detailed section, 
         FIG. 8  shows the cover flap of a respiratory flow sensor according to the invention according to  FIG. 1  in a view, 
         FIG. 9  shows the hinge of the cover flap according to  FIG. 8  in a detailed view, 
         FIG. 10  shows a schematic longitudinal section though a further alternative according to the invention of the respiratory flow sensor according to  FIG. 3 , 
         FIG. 11  shows a schematic longitudinal section through a further alternative according to the invention of the respiratory flow sensor according to  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The respiratory flow sensor  11  illustrated in  FIGS. 1 and 2  has a flow pipe  12 , a cover flap  32  and connections  22  and  23 . The cylindrical flow pipe  12  has a flow channel  13  and, on the free ends  15  or  17  thereof, respectively, hose connections for hoses. 
     The flow pipe  12  is embodied in two parts (flow pipe section  14  and flow pipe section  16 ), wherein the cover flap  32  is arranged in the flow channel  13  between the flow pipe sections  14  and  16 . The cover flap  32  divides the flow channel  13  into a first flow channel section  18  and into a second flow channel section  19 . In the region, in which the cover flap  32  comes to rest in the joined state of the flow pipe sections  14  and  16 , the flow pipe sections  14  and  16  in each case have a larger flow-through cross section. 
     The connection  22  leads into the flow channel  13  in the first flow channel section  18  and the connection  23  leads into the flow channel  13  in the second flow channel section  19 . The connections  22  and  23  thus lead into the flow channel  13  on both sides of the cover flap  32  and serve for the reduction of the differential pressure created by the cover flap  32 . 
     A water drainage device  41  is provided in the flow channel  13 . 
     In the illustration, which is simplified schematically in  FIGS. 3 and 4A to 4D , the water drainage device  41  comprises a plurality of drainage grooves  42  or  43 , respectively, which are arranged circumferentially spaced apart from one another. The liquid  46 , which accumulates in the respiratory flow sensor  11 , is collected in the drainage grooves  42  and  43  and is drained into it, if applicable. The drainage grooves  42  and  43  are embodied in such a way that the movement of the cover flap  32  is not impacted by them. 
     The drainage grooves  42  and  43  are arranged along a region of the inner circumference of the flow channel  13 , which extends across half of the entire inner circumference of the flow channel  13  (see  FIG. 4A ; 2×α+β). The distance (angular dimension α) of the drainage grooves  42  to the drainage grooves  43  is larger than the distance (angular dimension β) of the drainage grooves  43  to one another. Such an arrangement of the drainage grooves  42  and  43  ensures that a sufficient measurement accuracy with the respiratory flow sensor  11  is also ensured by means of the water drainage device  41 , when said respiratory flow sensor is rotated about its flow-through axis  20  area by area (see  FIGS. 4A to 4D ). The flow-through axis  20  corresponds to the center axis of the flow channel  13 . 
     Starting at the cover flap  32 , individual or all drainage grooves  42  and/or  43  can run along a curved line in a direction of the corresponding free end  15  or  17 , respectively, of the flow pipe  12 . Starting at the cover flap  32 , individual or all drainage grooves  42  and/or  43  can, in the alternative, run in a direction of the corresponding free end  15  or  17 , respectively, of the flow pipe  12  along an inclined surface, which is arranged at an angle to the flow-through axis  20  of the flow channel  13 . 
     In the case of the exemplary embodiment, which is illustrated in a schematically simplified manner in  FIG. 5 , the flow channel sections  62  and  63  in each case run in a curved manner in the region of the water drainage device  61  of the respiratory flow sensor  51 . In the case of this exemplary embodiment, the flow channel  53  also runs in a curved manner. 
     In the exemplary embodiment, which is illustrated in a schematically simplified manner in  FIG. 6 , the cross sections of the flow channel sections  82  and  83  increase in the region of the water drainage device  81  of the respiratory low sensor  71 , starting at the cover flap  92  in a direction of the corresponding free end  75  or  77 , respectively, of the flow pipe  72 . The flow channel sections  82  or  83 , respectively, are in each case embodied conically. In the alternative, at least one of the flow channel sections  82  or  83  could also be embodied in a trumpet-shaped manner. 
     In the flow pipe section  104 , the respiratory flow sensor  101  shown only in sections in  FIG. 7  has a stop section  108  and, in the flow pipe section  106  a stop section  110 , against which the free end region  113  of the cover flap  112  can come to rest. The stop sections  108  and  110  in the flow channel  103 , which are located opposite one another, define the maximum deflection of the cover flap  112  in both directions. The suitability for use of the respiratory flow sensor is thus improved additionally, because the cover flap can pivot only across the region, which is defined by the distance of the stop sections relative to one another. 
     Provision is made between the stop sections  108  and  110  for a water drainage device  121 , which is embodied in a trough-shaped manner to accommodate liquid. At least one such stop section can also be provided in the respiratory flow sensor  11 ,  51  or  71 , wherein the drainage of the accumulating liquid is advantageously ensured for example by means of the arrangement of corresponding recesses or slots in the stop section. 
     Here, the cover flap  32  illustrated in  FIGS. 8 and 9  has a circular and disk-shaped base body comprising a section  38 , which is fixed in the installed state, and a movable flap section  39 . The flap section  39  is connected to the fixed section  38  via a hinge region  33  and is separated therefrom by means of a first slot  34 . The flap section  39  has a free end region  40 , which is located opposite the hinge region  33 . The hinge region  33  is formed by the first slot  34  and a second slot  36 . The second slot  36  is embodied in an H-shaped manner, wherein provision is in each case also made spaced apart in parallel to the flanges  37  of the second slot  36  for a lateral slot  35 , into which the first slot  34  leads on both sides. All ends of the second slot  36  and of the lateral slots  35  have radii (see  FIG. 9 ). In the alternative, these ends can also have inclined surfaces 
     In the case of another exemplary embodiment of the respiratory flow sensor of  FIG. 1  to  FIG. 4D , is illustrated in a schematically simplified manner in  FIG. 10 , the flow channel sections  162  and  163  in each case run in a curved manner in the region of the water drainage device  161  of the respiratory flow sensor  151 . In the case of this exemplary embodiment, the flow channel  153  also runs in a curved manner. The first flow channel section  162  and the second flow channel section  163  are configured that no water accumulates in the region of the cover flap  154 . 
     In the case of another exemplary embodiment of the respiratory flow sensor of  FIG. 1  to  FIG. 4D , is illustrated in a schematically simplified manner in  FIG. 11 , the cross sections of the flow channel sections  182  and  183  increase in the region of the water drainage device  181  of the respiratory low sensor  171 , starting at the cover flap  192  in a direction of the corresponding free end  175  or  177 , respectively, of the flow pipe  172 . The flow channel sections  182  or  183 , respectively, are in each case embodied conically. In the alternative, at least one of the flow channel sections  182  or  183  could also be embodied in a trumpet-shaped manner. The first flow channel section  182  and the second flow channel section  183  are configured that no water accumulates in the region of the cover flap  192 . 
     
       
         
           
               
             
               
                   
               
               
                 List of Reference Numerals 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                 11 
                 respiratory flow sensor 
               
               
                 12 
                 flow pipe 
               
               
                 13 
                 flow channel 
               
               
                 14 
                 flow pipe section 
               
               
                 15 
                 free end of 14 
               
               
                 16 
                 flow pipe section 
               
               
                 17 
                 free end of 16 
               
               
                 18 
                 1. flow channel section 
               
               
                 19 
                 2. flow channel section 
               
               
                 20 
                 flow-through axis 
               
               
                 22 
                 connection 
               
               
                 23 
                 connection 
               
               
                 32 
                 cover flap 
               
               
                 33 
                 hinge region 
               
               
                 34 
                 1. slot 
               
               
                 35 
                 lateral slot 
               
               
                 36 
                 2. slot 
               
               
                 37 
                 flange of 36 
               
               
                 38 
                 fixed section of 32 
               
               
                 39 
                 flap section of 32 
               
               
                 40 
                 free end region of 39 
               
               
                 41 
                 water drainage device 
               
               
                 42 
                 drainage groove 
               
               
                 43 
                 drainage groove 
               
               
                 46 
                 liquid 
               
               
                 α 
                 angle between 42 and 43 
               
               
                 β 
                 angle between 43 and 43 
               
               
                 51 
                 respiratory flow sensor 
               
               
                 53 
                 flow channel 
               
               
                 61 
                 water drainage device 
               
               
                 62 
                 flow channel section 
               
               
                 63 
                 flow channel section 
               
               
                 71 
                 respiratory flow sensor 
               
               
                 72 
                 flow pipe 
               
               
                 75 
                 free end 
               
               
                 77 
                 free end 
               
               
                 81 
                 water drainage device 
               
               
                 82 
                 flow channel section 
               
               
                 83 
                 flow channel section 
               
               
                 92 
                 cover flap 
               
               
                 101 
                 respiratory flow sensor 
               
               
                 103 
                 flow channel 
               
               
                 104 
                 flow pipe section 
               
               
                 106 
                 flow pipe section 
               
               
                 108 
                 stop section 
               
               
                 110 
                 stop section 
               
               
                 112 
                 cover flap 
               
               
                 113 
                 free end region of 112 
               
               
                 121 
                 water drainage device 
               
               
                 151 
                 respiratory flow sensor 
               
               
                 153 
                 flow channel 
               
               
                 154 
                 cover flap 
               
               
                 161 
                 water drainage device 
               
               
                 162 
                 flow channel section 
               
               
                 163 
                 flow channel section 
               
               
                 171 
                 respiratory flow sensor 
               
               
                 172 
                 flow pipe 
               
               
                 175 
                 free end 
               
               
                 177 
                 free end 
               
               
                 181 
                 water drainage device 
               
               
                 182 
                 flow channel section 
               
               
                 183 
                 flow channel section 
               
               
                 192 
                 cover flap