Abstract:
Mask ports  180  for attaching supplemental oxygen tubes  510  or measurement devices to a respiratory mask are downwardly directed and recessed into the base  110  of the mask frame  100.  The ports may comprise a pair of downwardly extending tubular spigots  185  each housed in a respective recess  190  in the base  110,  with a shallow bridging recess  290  therebetween for receiving a bridging piece  300  of a closure cap  280.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to masks suitable for the delivery of breathable gases to a patient for the treatment of sleep disordered breathing (SDB), and to mask ports for such masks. 
       BACKGROUND OF THE INVENTION 
       [0002]    Respiratory masks used in the treatment of SDB may comprise a nasal mask, designed to fit over a patient&#39;s nose, or a full face mask designed to fit over the nose and mouth of the patient. In both cases, the mask is held in position by headgear. 
         [0003]    The mask generally comprises a relatively rigid shell, termed a frame, which defines a rearwardly opening cavity covering the patient&#39;s nose and/or mouth and a soft portion, termed a cushion, which spaces the frame away from the face for comfortable contact. 
         [0004]    The air or other breathable gas is supplied by a blower and passed along a flexible conduit to the mask. The conduit is typically of relatively large bore, for example approximately 2 cm diameter, with the mask frame having a gas inlet of comparable diameter. 
         [0005]    In addition to the gas inlet, the mask may also have CO 2  washout vents and one or more small diameter ports through which supplemental oxygen may be introduced or measurements made. The ports typically comprise a pair of cylindrical connectors moulded into the mask frame, usually projecting forward from the front surface of the frame. The mask ports typically also include a cap which prevents leakage of air from the mask when the port is not in use. 
         [0006]    Depending on the part construction and the relative diameters of the port and the tubing which supplies supplemental oxygen, the port may function as a male or a female connector. 
         [0007]    The Mirage® nasal mask (ResMed Ltd.) is a generally triangular mask with a gas inlet tube extending upwards from its apex. The two ports of that mask are located in the front of the gas inlet tube just above the patient&#39;s eye level, between a pair of shield projections. A single cap of silicone rubber covers both ports, and has tabs at either end to facilitate removal by pulling on the tabs in a direction away from patient&#39;s face. 
         [0008]    There is a need for ports which are conveniently located on the mask, which are protected from accidental breakage and which do not foul tubing. There is a need for a corresponding port cap which is sufficiently large so as to be easy to handle and which is not so small as to be easily lost. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention provides a mask frame for a respiratory mask, said mask frame defining a mask cavity adapted for communication with a patient&#39;s airways and including a gas inlet adapted for connection to a supply of breathable gas, further including a recess in a lower portion of the mask frame, at least one mask port comprising a downwardly extending tubular spigot located in said recess, said spigot having a bore communicating with the mask cavity via a port aperture in the mask frame. 
         [0010]    The cap is preferably constructed from a single piece of silicone or other elastomeric material with tabs preferably to the front of the mask when positioned on the ports. Preferably the base of the cap is flush with the base of the mask. Preferably, to remove the cap, the tabs are pulled in a downwards motion, relative to the front of the mask. 
         [0011]    A further form of the invention provides a mask frame for a respiratory mask, said mask frame defining a mask cavity adapted for communication with a patient&#39;s airways including a gas inlet adapted for connection to a supply of breathable gas, further including at least one downwardly opening port located in a lower portion of the mask frame and communicating with the mask cavity. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    Further embodiments of the invention will now be described with reference to the accompanying drawings, in which: 
           [0013]      FIG. 1  shows a side perspective view of a mask frame. 
           [0014]      FIG. 2  shows a front view of the mask frame of  FIG. 1 . 
           [0015]      FIG. 3   a  shows a bottom view of the mask frame of  FIG. 1 . 
           [0016]      FIG. 3   b  shows a section B-B from  FIG. 3   a.    
           [0017]      FIG. 3   c  shows a section C-C from  FIG. 3   a.    
           [0018]      FIG. 4   a  shows a perspective view of the port cap. 
           [0019]      FIG. 4   b  shows an end view of the port cap. 
           [0020]      FIG. 4   c  shows a top view of the port cap. 
           [0021]      FIG. 4   d  shows a front view of the port cap. 
           [0022]      FIG. 4   e  shows a bottom view of the port cap. 
           [0023]      FIG. 4   f  shows a rear view of the port cap. 
           [0024]    In  FIGS. 4   a  to  4   f  approximate dimensions are indicated in mm. 
           [0025]      FIGS. 5   a  to  5   c  schematically illustrate an alternative embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0026]      FIGS. 1 and 2  illustrate a mask frame  100  for a nasal mask, formed as a moulded shell of polycarbonate or similar rigid material, which acts as a body onto which the other components of the mask are attached. A suitable material for the mask frame is Makrolon 2458 polycarbonate from Bayer. 
         [0027]    The frame  100  is generally triangular in front view, having a base  110 , a pair of inclined side walls  120  extending towards an apex and a front wall  130 . The frame defines a mask cavity covering the patient&#39;s nose, and is open at its rear. A rim  140  at the rear edge of the base  110  and side walls  120  approximates the contours of the patient&#39;s face and is adapted for attachment of a soft mask cushion (not shown) to space the frame away from the patient&#39;s face for sealing and comfort. The apex of the frame has an extension  150  for attachment of a forehead support (not shown). 
         [0028]    In the illustrated mask frame, a gas inlet aperture  160  is formed in the front wall  130 , for connection of a gas supply conduit or similar, which may include an elbow connector (not shown) pivotably connected to the frame. In other forms of mask, the gas inlet aperture may be formed at the apex of the frame. 
         [0029]    The mask frame further includes lower headgear connection points  170  for attachment to the headgear which holds the mask in place on the patient&#39;s face. Upper headgear connection points may be formed in the forehead support (not shown). 
         [0030]    With reference to  FIGS. 1 to 3   a , it can be seen that the mask frame includes two ports  180 , approximately 2.5 cm apart, located in recesses  190  in the base of the mask frame  100 . These recesses are positioned in between the lower headgear strap connection points  170 . The ports are positioned so that in use, oxygen or other breathable gas can be delivered close to the patient&#39;s nares. 
         [0031]    Each port is formed as a tubular spigot  185  with an approximate external diameter of 4 mm and an approximate length of 1 cm. The spigot  185  forms the male connector onto which small bore tubing supplying, for example, oxygen, may be attached. 
         [0032]    An elevational cross-section through the port is shown in  FIG. 3   b , and a lateral cross-section at  FIG. 3   c.    
         [0033]    As best seen in  FIGS. 3   b  and  3   c , each recess  190  is approximately rectangular in elevation ( FIG. 3   a ) and closed off from the mask cavity except for an aperture  200  extending through the recess upper wall  210  between the bore  220  of the spigot  185  and the mask cavity. The recess is bounded by the upper wall  210 , side wall portions  230 ,  240  and a rear wall portion  250 , and is open at its bottom end. A front wall  260  is formed as a continuation of the front wall  130  of the mask frame. The rear wall portion  250  and one or both side wall portions  230 ,  240  may be formed as a continuous curve. 
         [0034]    These boundary walls  230 ,  240 ,  250 ,  260  of the recess are spaced from the spigot by a sufficient distance, for example at least 1 mm, to allow a small bore oxygen tube to be pushed onto the spigot, and also to allow the closure portion  270  of a cap  280  ( FIGS. 4   a  to  4   f ) to be retained. 
         [0035]    The base  110  of the mask also includes a shallow bridging recess  290  for receiving the bridge piece  300  joining the two closures  270  of the cap  280 . 
         [0036]    The bottom edge of the frame front wall  130  includes a pair of small notches  310  through which gripping tabs  320  of the cap extend, so that the tabs extend forward of the front wall for gripping by the user. Pulling downwards on the tab will remove the respective closures  270  from its spigot  185  to allow attachment of an oxygen tube or a tube leading to a measurement device. 
         [0037]    The cap  280  is suitably formed of a relatively soft elastomeric material, such as Dow Silastic 94-595 HC silicone. 
         [0038]    As can be seen in  FIGS. 1 and 2 , the above construction results in the bottom of the cap  280  being substantially flush with the base  110  of the frame  100 , providing a compact and aesthetically pleasing arrangement. 
         [0039]    The asymmetric shape of the recessed chamber and corresponding shape of the cap  280  reduces the likelihood that the cap  280  will be incorrectly positioned back-to-front. 
         [0040]    A further advantage of recessing the ports into the mask frame is that the dead volume of the frame is reduced. A further advantage of providing access from the bottom of the mask frame is that the likelihood of fouling the gas delivery conduit is reduced where a swivel connection is used to provide air from the flow generator. 
         [0041]    Another advantage is that the loss of supplemental oxygen through the vent is reduced by positioning the port away from the main vent path. 
         [0042]    In other embodiments, there may be one port, or there may be more than two ports. Furthermore, ports may have individual caps. Ports may be connected by way of a small bore tubing or in any other suitable manner to a manometer for measuring pressure in the mask cavity during the setting up of the device or during treatment of SDB. Alternatively, one or more ports may be used in conjunction with transducers and control algorithms to control the operation of an automatically adjusting device. 
         [0043]    In an alternative embodiment, a larger diameter cylinder is used for the port, hence the cylinder will function as a female connector with respect to the supplemental oxygen tubing. 
         [0044]    In another embodiment, the spigots could extend within the mask frame to bring the oxygen supply closer to the nares. 
         [0045]      FIGS. 5   a  to  5   c  are schematic front elevational cross-sections of an alternative mask port arrangement  500  with, respectively, an oxygen delivery tube  510  being inserted into a port  520  ( FIG. 5   a ), the delivery tube in position in the port ( FIG. 5   b ), and the tube removed and a cap  530  inserted ( FIG. 5   c ). 
         [0046]    The position and orientation of the ports  520  is generally similar to that described above with reference to  FIGS. 1 to 3   c  except that the ports  520  are formed as tubes extending upwards into the mask cavity, and open at their upper ends. In common with the previously described embodiment, the base  540  of the mask frame includes a pair of these recessed mask ports, joined by a shallow bridging recess  550 . 
         [0047]    As can be seen from  FIGS. 5   a  and  5   b , the port  520  acts as a female connector for insertion from below of a corresponding oxygen supply tube  510  having a diameter chosen for substantially sealing engagement in the port. 
         [0048]    As shown in  FIG. 5   c , the configuration of the cap  530  is generally similar to that of  FIGS. 4   a  to  4   f , including a pair of closure portions  560  joined by a bridging portion  570 , except that the closure portions for sealing the ports when not in use are preferably formed as solid plugs rather than as cup-shaped closures as in  FIGS. 4   a  to  4   f.    
         [0049]    In another embodiment, the tabs  320  of the cap  280  are below the mask, rather than in front. 
         [0050]    Although the invention has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the application of the principles of the invention. Numerous modifications may be made in the illustrative embodiments of the invention and other arrangements may be devised without departing from the spirit and scope of the invention.