Abstract:
Nasal cannulas for providing respiratory therapy to patients can have a curved prong section that has turbulation elements on the inside curve of the prong. A flow of breathing gas moving through the prong may incur less resistance and create less noise when flowing through such a prong due to the promotion of favorable flow dynamics.

Description:
INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS 
       [0001]    Any and all applications for which a foreign or domestic priority claim is identified in the Application Data Sheet as filed with the present application are hereby incorporated by reference under 37 CFR 1.57. 
       TECHNICAL FIELD OF THE INVENTION 
       [0002]    The present disclosure generally relates to systems and devices for providing gases to patients for respiratory therapy. More particularly, the present disclosure relates to nasal cannula interfaces for providing gases to patients via the nasal passages. 
       BACKGROUND OF THE INVENTION 
       [0003]    Medical professionals may wish to provide patients with respiratory assistance in the form of supplemental oxygen or airflow for many reasons in ICU, other hospital, or home environments. Different types of interfaces for supplying gases to patients are available. For example, various nasal masks, full face masks, oral interfaces, nasal pillows, and nasal cannula interfaces exist. Nasal cannula interfaces may include two nasal prongs that are placed in the patient&#39;s nostrils to deliver gases to the patient. 
       SUMMARY OF THE INVENTION 
       [0004]    A nasal cannula system typically comprises a cannula body defining a cavity, one or two prongs extending from the body, and gases supply tubing that extends from one or two sides of the body. In some prior art configurations, the prong may be curved rather than straight to better match the profile of the nares. However, as flow moves through a curved prong, the flow may develop turbulent eddies that may generate noise and increase resistance to flow. Thus, it is an object of the disclosure to provide patients with a nasal cannula that might be easier to use, or at least provide the public with a useful choice. 
         [0005]    In some configurations, a nasal cannula comprises a cannula body defining a cavity and at least one curved nasal prong extending from the cannula. The prong has an interior passage in communication with the cavity. A turbulation element is on an inside curve of the prong. 
         [0006]    In some configurations, the turbulation element is adapted to induce turbulence in a flow of breathing gas through the interior passage in a boundary layer at the inside curve. 
         [0007]    In some configurations, the turbulation element extends along an entire length of a curved section of the prong. 
         [0008]    In some configurations, the turbulation element extends along an entire circumferential length of the inside curve. 
         [0009]    In some configurations, the turbulation element extends beyond the inside curve in a circumferential direction. 
         [0010]    In some configurations, the turbulation element comprises a surface portion having a component that extends in a circumferential direction. 
         [0011]    In some configurations, an initial portion of the prong extending from a portion of the cannula body defining the cavity is generally straight. 
         [0012]    In some configurations, the turbulation element comprises a plurality of one or more of recesses, ridges, pits, protrusions, bumps, lumps or humps. 
         [0013]    In some configurations, the turbulation element comprises random surface texturing. 
         [0014]    In some configurations, features defining the turbulation element are elongated in a circumferential direction. 
         [0015]    In some configurations, an average amplitude of features defining the turbulation element is between 0% and 5% of a diameter of the prong. 
         [0016]    In some configurations, the prong is formed as a unitary structure with the cannula body. 
         [0017]    In some configurations, the prong is formed separately from a portion of the cannula body that defines the cavity. 
         [0018]    In some configurations, a nasal cannula system comprises a flow circuit defined by one or more of a source of breathing gas, a supply conduit and a cannula having at least one curved nasal prong. The flow circuit comprises a curved portion. At least one turbulation element is provided on an inside curve surface of the curved portion. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    Specific embodiments and modifications thereof will become apparent to those skilled in the art from the detailed description herein having reference to the figures that follow. 
           [0020]      FIG. 1  is a side cross-sectional view of a nasal prong of a nasal cannula. 
           [0021]      FIG. 2  is a side cross-sectional view of a nasal prong of a nasal cannula, wherein the prong comprises turbulation elements on the inside curve of the tube wall. 
           [0022]      FIG. 3  is a side cross-sectional view of a nasal prong of a nasal cannula, wherein the prong comprises an alternative version of the turbulation elements on the inside curve of the tube wall. 
           [0023]      FIG. 4  is a side cross-sectional view of a nasal prong of a nasal cannula, where the prong comprises yet another alternative version of the turbulation elements on the inside curve of the tube wall. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]    With reference to  FIG. 1 , a curved nasal cannula prong  100  with an initially laminar gas flow  102  moving through the prong  100  is shown. As laminar flow  102  passes through the relatively straight base  103  of the prong and into the more curved region  101 , certain phenomena related to flow dynamics of the system can be observed. In this case, the flow may come to have a relatively low pressure on the inside of the curve and a relatively high pressure on the outside of the curve. In the low pressure area on the inside of the curve, the laminar flow in the boundary layer may be prone to flow separation at some point  104  along the flow path, which can separate the flow into a turbulent flow layer  106  and a laminar flow layer  108 . An undesirable level of flow resistance and noise can arise from excessive turbulent flow like that present in the turbulent flow layer  106 . 
         [0025]    One way of mitigating the effects of the turbulent flow layer  106  is to place a turbulation element  110  on the surface of the inside curve of the prong  100 . The turbulation element  110  may be or comprise one or a plurality of, for example, a pit, protrusion, recess, ridge, bump, lump, hump, and/or other element that may create a suitable surface roughness on the inside curve of the prong  100 . 
         [0026]    With reference to  FIG. 2 , a nasal cannula system  50  includes a cannula body  52  defining a cavity  54 . The cannula body  52  can be held in place on the face of a user by any suitable arrangement, such as a headgear assembly or adhesive, for example. The cannula body  52  can be any size or shape suitable for being positioned on the face of the user and supporting one or two nasal prongs  100  for placement in the nares of the user. Similarly, the cavity  54  can be of any suitable size or shape for supplying a flow of breathing gas to the prongs  100 . The flow of breathing gas can be provided by a gases source or generated by a blower, for example, and supplied to the cavity  54  by a suitable conduit, such as a breathing gas supply tube. 
         [0027]    Each of the prongs  100  comprises a side wall  56  that defines an interior passage  58 , which communicates with the cavity  54  to deliver the flow of breathing gas from the cavity  54  to the user&#39;s nares. The side wall  56  of the prongs  100  can be formed as a unitary structure with the cannula body  52  or can be formed separately, such as by a prong insert. The prongs  100  each have an opening at a first end, which is referred to as an inlet  60 , and an opening at a second end, which is referred to as an outlet  62 . The inlet  60  allows the flow of breathing gas to enter the passage  58  of the prong  100  from the cavity  54 . The outlet  62  allows the flow of breathing gas to exit to passage  58  and the cannula system  50 . Preferably, the side wall  56  comprises a curved portion such that the axes of the inlet  60  and outlet  62  or planes in which the inlet  60  and outlet  62  lie are non-parallel or angled relative to one another. The curved portion of the side wall  56  can define an inside curve or inside portion that is closest to the radius of the curve and an outside portion that is furthest from the radius of the curve. The curved portion can comprise a portion or an entirety of the side wall  56 . In some configurations, an initial portion of the prong  100  extending from the cannula body  52  is generally straight or linear and a subsequent portion of the prong  100  is curved. Other features of the cannula system  50  can be similar to any of those disclosed in Applicant&#39;s application no. PCT/NZ2014/000040, filed Mar. 14, 2014, entitled NASAL CANNULA ASSEMBLIES AND RELATED PARTS, the entirety of which is incorporated by reference herein. 
         [0028]    In the illustrated configuration of  FIG. 2 , one possible arrangement of a turbulation element  110  comprises at least one and preferably a plurality of depressions/recesses or ridges defined between the depressions. The depressions or ridges are provided along a length of the inside of the curve of the prong  100 . The depressions or ridges can be provided along a portion of the length of the curve of the prong  100  or along a substantial entirety or an entirety of the length of the curve of the prong  100 . In some configurations, the depressions or ridges are provided along a substantial entirety or an entirety of the length of the prong  100 . 
         [0029]    The depressions or ridges can be provided on only a portion of the inside portion of the curve of the prong  100  in a circumferential direction or direction around a longitudinal axis of the passage  58  or side wall  56  of the prong  100 . In other arrangements, the depressions or ridges can be provided on an entirety of the inside portion of the curve of the prong  100 . In some arrangements, it may be desirable or at least not harmful to the performance of the cannula system  50  to provide depressions or ridges on both inside portions and outside portions of the curve of the prong  100 . Thus, in some arrangements, an entire interior surface of the side wall  56  of the prong  100  can comprise depressions or ridges. In some configurations, it may be desirable to provide depressions or ridges only on an outside portion of the curve or to omit the depressions or ridges on an inside portion of the curve while providing depressions or ridges elsewhere. 
         [0030]    The depressions or ridges of the turbulation element  110  can be of any number, size or shape suitable to induce a desirable or effective level of laminar flow in the prong  100  or to provide a desirable or effective reduction in eddy currents, such as by inducing a turbulent boundary layer at the inside curve. The depressions or ridges can be elongate and can extend in a circumferential direction (or around the longitudinal axis) of the passage  58  of the prong  100  or can be offset from a circumferential direction or a direction perpendicular to the longitudinal axis of the passage  58 . The depressions or ridges can be of a relatively short length, including round or square, and can be provided in a repeated pattern in a circumferential direction or a direction perpendicular to the longitudinal axis of the passage  58 . Preferably, the depressions or ridges have at least a surface portion having a component that extends in a circumferential direction or a direction perpendicular to the longitudinal axis of the passage  58 . 
         [0031]    The size of the turbulation element  110  (e.g., a depth of the depressions or a height of the ridges) can be related to or selected based on characteristics or dimensions of the passage  58  of the prong  100 , such as a particular proportion of the cross-sectional width or diameter, the cross-sectional area, the length or the radius of curvature of the passage  58 , for example. The size of the turbulation element  110  can be related to or selected based on the flow characteristics of the flow of breathing gas through the passage  58  of the prong  100 . The turbulation element  110  can be sized based on a combination of these factors or in view of other relevant factors, such as manufacturability or material considerations, for example, or any combination thereof. 
         [0032]    In some configurations, as incoming flow  102  moves through the prong  100 , the turbulation element  110  induces turbulence in a thin section of the boundary layer on the inside curve of the prong  100  at and/or around the point  104  where the flow encounters or runs along the element  110 . The thin turbulent flow layer  106  created is much less prone to separation from the inside curve of the prong  100  than laminar flow, and so a larger portion of the flow may remain laminar and/or a eddy currents are reduced relative to a prong  100  that does not comprise a turbulation element  110 , which may decrease the flow resistance and noise of flow moving through the prong  100  in use. 
         [0033]    There are no particular limitations as to the size, shape, number or arrangement of the individual features defining the turbulation element  110 . Some possible configurations of the turbulation elements  110  are shown in  FIGS. 3 and 4 . Features or characteristics of such turbulation elements  110  or of the cannula systems in general can be the same as or similar to those described elsewhere herein or can be of any other suitable arrangement. 
         [0034]    With reference to  FIG. 3 , the turbulation element  110  comprises at least one and preferably a plurality of raised bumps. The raised bumps can be, for example, a portion of a sphere, ovoid, cube, cuboid, cone, cylinder or other geometric shape. The number, size, shape and other characteristics can be selected as desired or as described herein. 
         [0035]    With reference to  FIG. 4 , the turbulation element  110  comprises at least one and preferably a plurality of ridges and recesses. The ridges or recesses can be, for example, a portion of a sphere, ovoid, cube, cuboid, cone, cylinder or other geometric shape. The number, size, shape and other characteristics can be selected as desired or as described herein. 
         [0036]    In some configurations, the turbulation element  110  may comprise an ordered or random surface texture/roughness along a portion or an entirety of the inside curve of the prong  100 . In a preferred configuration, the average amplitude of the surface roughness R a  of the turbulation element  110  is between about 0% and 5% of the diameter (or other cross-sectional dimension) of the prong  100 . In some configurations, the turbulation element  110  may instead be any feature that promotes a thin turbulent boundary layer on the inside curve of the prong  100 . In some configurations, the element  110  is integrally formed with the cannula prong  100 . In some configurations, the element  110  is a component separate from the cannula prong  100 . In some configurations, the element  110  may be placed on any inside curve of the prong  100 . In some configurations, the element  110  may circumscribe the internal walls of the prong  100 . Additionally, such turbulation elements  110  may be beneficially placed anywhere in which there is a curved section in the flow path of the cannula circuit, e.g., prongs, curved parts of the gases supply tube, within the flow generator/flow source, in the gases flow manifold/prong transition, et cetera. 
         [0037]    Unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise”, “comprising”, and the like, are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense, that is to say, in the sense of “including, but not limited to.” 
         [0038]    Where, in the foregoing description reference has been made to integers or components having known equivalents thereof, those integers are herein incorporated as if individually set forth. 
         [0039]    The invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, in any or all combinations of two or more of said parts, elements or features. 
         [0040]    Reference to any prior art in this specification is not, and should not be taken as, an acknowledgement or any form of suggestion that that prior art forms part of the common general knowledge in the field of endeavour in any country in the world. 
         [0041]    Certain features, aspects and advantages of an embodiment of the present invention have been described with reference to nasal cannulas. However, certain features, aspects and advantages of the nasal cannulas as described above may be advantageously used with other therapeutic or non-therapeutic breathing interfaces, such as full face masks, nasal masks, oral masks, and nasal pillows. Certain features, aspects and advantages of the method and apparatus of the present disclosure may be equally applied to other breathing devices for other conditions. 
         [0042]    Although the present invention has been described in terms of a certain embodiment, other embodiments apparent to those of ordinary skill in the art also are within the scope of this invention. Thus, various changes and modifications may be made without departing from the spirit and scope of the invention. For instance, various components may be repositioned as desired. Moreover, not all of the features, aspects and advantages are necessarily required to practice the present invention. Accordingly, the scope of the present invention is intended to be defined only by the claims that follow.