Abstract:
A respiratory mask assembly for delivering breathable gas to a patient includes a mask frame having a first cooperating interlocking structure; a mask cushion provided to the frame; a cushion clip to retain the mask cushion on the mask frame, the cushion clip having a second cooperating interlocking structure and being selectively attachable to and detachable from the mask frame, the first and second cooperating interlocking structures interlocking to secure the cushion clip on the mask frame; and an elbow joint provided to the frame and having a swivel tube adapted to connect to a gas delivery conduit. The first and second cooperating interlocking structures include a tab-recess arrangement in which a plurality of tabs are engageable within respective recesses.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 12/419,442, filed Apr. 7, 2009 (now U.S. Pat. No. 8,113,197), which is a continuation of U.S. application Ser. No. 11/322,237, filed Jan. 3, 2006, now U.S. Pat. No. 7,861,714, which is a continuation of U.S. application Ser. No. 10/164,370, filed Jun. 10, 2002, now U.S. Pat. No. 7,207,334, which is a divisional of U.S. application Ser. No. 09/498,705, filed Feb. 7, 2000, now U.S. Pat. No. 6,491,034, and related to the following applications: U.S. application Ser. No. 09/985,457, filed Nov. 2, 2001, now U.S. Pat. No. 7,185,652, and U.S. application Ser. No. 09/985,458, filed Nov. 2, 2001, now U.S. Pat. No. 7,089,939, and U.S. application Ser. No. 11/285,077, now U.S. Pat. No. 7,174,893, each incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE TECHNOLOGY 
     The present technology relates to improvements in patient gas delivery apparatus of the kind used in the analysis and treatment of respiratory disorders. The invention will be described with particular reference to patient gas delivery apparatus used in the treatment of respiratory disorders such as Obstructive Sleep Apnea (OSA) but it is not intended to be limited thereto. 
     BACKGROUND OF THE TECHNOLOGY 
     Patient gas delivery apparatus of the kind having a mask worn by a patient and a gas delivery conduit attached to the mask are commonly used in the analysis and treatment of respiratory disorders. The gas conduit delivers a gas under pressure to the patient. It is necessary that the gas conduit is detachable from the mask to facilitate cleaning. 
     Patient gas delivery apparatus typically includes at a minimum, a gas delivery conduit and a nose or full face mask. In some cases it is a clinical requirement that additional components be included, such as means for CO 2  washout, for example, vents, anti-asphyxia valves and the like. In some cases, these additional components must be assembled in between the gas delivery conduit and the mask. Problems with prior art assemblies include: (a) they may be inadvertently assembled without the additional components; (b) they may be incorrectly assembled, for example, incorrectly aligned; (c) during the course of treatment, the patient may inadvertently remove or dismantle the assembly and incorrectly reassemble it. 
     Further, known mask cushions are usually molded from a relatively soft, resilient, elastic material and they are shaped during manufacture to match the facial contours of an average intended wearer. However, a problem with the known types of masks is that, because individuals vary so much from the average, the masks must be forced against their inherent resiliency to deform and so adapt to the shapes of the users in order to avoid gas leakage. This requires that the masks be secured firmly by retaining straps or harnesses in order to prevent air leakage. 
     Flow generators are typically utilized to deliver a breathable gas (i.e., air) to a patient wearing the mask. In CPAP treatment, gas is delivered to the patient&#39;s airways at about 2-30 cm H 2 O above atmospheric pressure. The flow generator is generally connected to flexible tubing which is secured to the mask worn by the patient. If the flow generator&#39;s operation is interrupted as a result of a power outage or other mechanical or electrical failure, there may be a significant build up of carbon dioxide in the mask as the patient&#39;s exhaled air is not washed out of outlet vents which are usually contained in the mask. This may present a health problem to the patient. 
     There have been numerous patents which have addressed some sort of safety valve for gas or air delivery masks. An example of such a patent is U.S. Pat. No. 5,438,981. This patent discloses a counter balanced, rigid valve element which depending on the gas flow, either covers an opening to the ambient air or covers the gas flow airway such that the air or breathing gas is forced out into the ambient air opening However, this system suffers from being a fairly complicated and expensive system whose correct operation relies on a counter balanced moving part moving relative to its housing. Further, if any condensation from the air gets on or around the balanced valve element, the operation of this valve element can be compromised. This valve is also difficult to clean. 
     Applicant&#39;s International Application PCT/AU97/00849 discloses a valve having a single valve element. However, whilst being simpler than preceding valves of this type, the valve shown in PCT/AU97/00849 still relies on the use of a rigid valve element moving relative to its housing and biased by magnets. 
     SUMMARY OF THE INVENTION 
     One aspect of the present invention is directed towards solving or ameliorating one or more of these problems. One aspect of the invention will be described with reference to a full face mask, though other forms of mask and additional components may be used. 
     According to one example, a respiratory mask assembly for delivering breathable gas to a patient comprises a mask frame having a first cooperating interlocking structure; a mask cushion provided to the frame and adapted to form a seal on the patient&#39;s face; a cushion clip to retain the mask cushion on the mask frame, the cushion clip having a second cooperating interlocking structure and being selectively attachable to and detachable from the mask frame, the first and second cooperating interlocking structures interlocking with one another in a cooperating relationship to secure the cushion clip on the mask frame; and an elbow joint provided to the frame and having a swivel tube adapted to connect to a gas delivery conduit, wherein the first and second cooperating interlocking structures are provided to at least a bottom and left and right sides of the mask frame and cushion clip, and include a tab-recess arrangement in which a plurality of tabs are engageable within respective recesses in interlocking relation to secure the clip to the frame. 
     According to another example, a respiratory mask assembly for delivering breathable gas to a patient comprises a mask frame having a first cooperating interlocking structure; a cushion clip having a second cooperating interlocking structure and being selectively attachable to and detachable from the mask frame, the first and second cooperating interlocking structures interlocking with one another in a cooperating relationship to secure the cushion clip on the mask frame; and a mask cushion adapted to form a seal on the patient&#39;s face and having an outer peripheral portion positioned between the mask frame and the cushion clip so as to seal the mask cushion on the mask frame. 
     According to yet another example, a respiratory mask assembly for delivering breathable gas to a patient comprises a mask frame; a mask cushion adapted to form a seal with the patient&#39;s face; and a clip member engaged with the mask cushion and structured to interlock with the mask frame, wherein the mask frame and the clip member include a tab-recess arrangement in which a plurality of securing tabs engage with a corresponding one of a plurality of recesses so as to retain the mask cushion on the mask frame, the tab-recess arrangement provided to at least a bottom and left and right sides of the mask frame and clip member. 
     These and other aspects of the invention will be described in or apparent from the following detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further examples of the present technology will now be described by way of example only with reference to the accompanying drawings in which: 
         FIG. 1  is a perspective view showing the mask, anti-asphyxia valve housing and conduit connection assembly; 
         FIG. 2  is an exploded view of the anti-asphyxia valve and conduit connection assembly shown in  FIG. 1 ; and 
         FIG. 3  is an exploded view of the mask assembly shown in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     In  FIG. 1  a mask frame is shown generally at  10 . The mask is designed to be worn on a patient&#39;s face and is secured by means of straps (not shown) received by attachment points  18 . 
     A conduit end assembly is shown generally at  20 , including an elbow part  26  having at one end thereof a combined vent/connector piece  28 . The elbow and vent/connector piece together form a housing for an anti-asphyxia valve (as will be further discussed) or other internal components (not shown). At the other end of the elbow is a detachable swivel tube  29  for connection of the gas delivery conduit (not shown). 
     The mask  10  includes a circular aperture  12  sized to receive a mating portion  22  of the vent/connector piece  28 . The mating portion  22  has an annular groove  23  formed therein that receives a locking means  30  in the form of a C-shaped clip attached after mating to the mask. The clip  30  has an outside diameter greater than the width of the aperture  12  and an inner diameter adapted to ensure a snug fit within the annular groove  23 . The clip  30  is resilient and can expand sufficiently to allow the clip to be fitted into and removed from the groove  23 . As shown in  FIG. 1 , the clip  30  is located onto the mating portion  22  on the inside of the mask  10 . In this position, the clip  30  is inaccessible while the mask is being worn by a patient. Once the mating portion  22  of the vent/connector piece  28  has been inserted through the aperture  12  and the locking clip placed in the annular groove, the conduit end assembly  20  and the mask  10  cannot be separated without first removing the mask from the patient. 
     An exploded view of one embodiment of the anti-asphyxia valve and conduit connector assembly is shown in  FIG. 2 . 
     As illustrated in  FIG. 2 , the end of the elbow  26  adjacent the mask  10  is fitted with an anti-asphyxia valve arrangement that provides an air passage to the patient in the event of failure of the gas delivery apparatus, consisting of a valve membrane  27  fitted into the end of elbow  26  and vents  31  in the vent/connector piece  28 . During proper operation of the gas delivery system, the valve membrane remains in the orientation shown in  FIG. 2 , closing off the vents  31 . In the event of a drop in pressure below a predetermined level, the valve membrane  27  flips to a reverse orientation, opening the vents  31 . The construction and operation of the anti-asphyxia valve is described in more detail in the Applicant&#39;s Australian Patent Application No. 65527/99, the contents of which are incorporated herein by reference and described herein. 
     Resilient detents  42  on the elbow  26  pass through and engage behind slot-forming formations  44  in the vent/connector piece  28  to provide releasable engagement of the two parts. 
     The vent/connector piece has a collar  47  that abuts a corresponding surface of the mask  10  to limit the distance that the vent/connector piece can be inserted into the mask aperture  12  ( FIG. 1 ). The corresponding surface is an annulus  50  having a protruding rim  51  the outer circumference of which preferably engages the inner surface of the detents  42  on insertion of the mating portion  22  into the aperture  12 . This engagement prevents the detents from being pushed radially inwards sufficiently for the detents to disengage from behind the slot-forming formations  44 , thus preventing the elbow  26  and vent/connector piece  28  from separating whilst still attached to the mask frame  11 , for example during patient treatment. The result of this is that the anti-asphyxia valve arrangement cannot be disassembled without first removing the elbow and vent/connector piece assembly from the mask. However, once disconnected from the mask, the assembly may be readily separated for cleaning and then reassembled. 
     The other, distal end of elbow  26  has an enlarged diameter portion which receives the swivel tube  29 , onto which a flexible gas conduit (not shown) may be fitted. The swivel tube  29  has a pair of flanges  56  and  57  defining an annular groove  58  therebetween. The end of swivel tube  29  is inserted into the elbow  26  until the end flange  57  abuts an inner surface (not shown) within elbow  26 . In this position the annular groove  58  is at least partially aligned with an annular groove  61  in the exterior of the elbow, which receives a swivel clip  41 . 
     The swivel clip  41  has an inner diameter only slightly greater than the diameter of the groove  61 , to ensure a snug fit within the groove. The clip  41  is resilient to permit sufficient expansion for attachment and removal of the clip from the groove. The groove  61  has slots  59  which receive lugs  62  on the clip. These lugs rotatably engage in the groove  58  between flanges  56  and  57  of the swivel tube. The swivel tube arrangement thus acts as a rotatable coupling between the conduit and the elbow whilst allowing quick attachment and removal of the gas conduit from the elbow regardless of whether the assembly is attached to the mask at the time. 
     As shown in  FIG. 3 , the mask includes a mask frame  11 , cushion  13  and cushion clip  14 . The cushion is received on a rib  15  extending around the periphery of the mask frame  11 . The cushion is held to the rib by the cushion clip  14 . The mask frame includes attachment points  18  that receive straps (not shown) for attaching the mask to the patient, an aperture  16  for receiving an air vent  17 , and measurement ports  19 . 
     The mask frame  11  includes a plurality of recesses  11 . 1  that provide a first cooperating interlocking structure and the cushion clip  14  includes a plurality of tabs  14 . 1  that is equal to a number of recesses in the mask frame  11  and provides a second cooperating interlocking structure. The plurality of tabs  14 . 1  engage a respective recess  11 . 1  to secure the cushion clip  14  on the mask frame  11 . 
     The mask assembly, in the example shown in  FIG. 3 , is a full face mask. As shown in  FIG. 3 , the frame includes top and bottom recesses, two left side recesses and two right side recesses (not shown). The cushion clip  14  includes corresponding top and bottom tabs  14 . 1  as well as two right side tabs (both shown) and two left side tabs (only one shown). 
     The mask cushion includes a groove  13 . 1  extending around the periphery thereof and the groove of the cushion receives the rib  15  of frame  11 . 
     The cushion  13  includes an outwardly extending portion  13 . 2  that provides the groove  13 . 1  on one side thereof An opposite side of the outwardly engaging portion  13 . 2  provides a shoulder  13 . 3  that engages a flange  14 . 2  on the cushion clip  14  to retain the cushion  13  on frame  11 . 
     The cushion includes a rearwardly extending portion designated by reference number  13 . 4 . The cushion serves to seal the mask assembly on the patient&#39;s face, and is structured to space the mask frame  11  from the patient&#39;s face. 
     The frame  11  includes a first side  11 . 2  structured to accommodate cushion  13 , and a second side  11 . 3 . The cushion clip  14  and frame  11  are configured to cooperate with one another such that the cushion clip  14  is selectively attachable to the frame  11  in a first direction  11 . 4  defined generally from the first side  11 . 2  to the second side  11 . 3  of the frame, to thereby secure the cushion  13  between the cushion clip  14  and the frame  11 . 
     The cushion clip  14  and frame  11  are configured to cooperate with one another such that the cushion clip is selectively detachable from the frame  11  in a second direction  11 . 5 , opposite to the first direction  11 . 4 , defined generally from the second side  11 . 3  to the first side  11 . 2  of the frame  11 , to thereby allow removal of the cushion  13  from frame  11 . 
     Each tab  14 . 1  is resiliently movable in a third direction  14 . 3  that is substantially transverse to the first and second directions  11 . 4  and  11 . 5 . Tab portions  14 . 1  move in the direction indicated by arrows  14 . 3  when the tab portions are snapped or flexed into place within recesses  11 . 1 , and when they are removed therefrom. 
     While particular embodiments of this invention have been described, it will be evident to those skilled in the art that the present invention may be embodied in other specific forms without departing from the essential characteristics thereof The present embodiments and examples are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.