Abstract:
A respiratory mask assembly for treatment of sleep disordered breathing includes a frame, a cushion which at least in part defines a cavity adapted to receive at least a patient&#39;s nose, and an air delivery connection supported by the frame and adapted to connect an air delivery conduit to supply air to the cavity. The cushion includes a face contacting portion, a non-face contacting portion, and a gusset portion between the face contacting portion and the non-face contacting portion, wherein the gusset portion includes a hanging portion that, when seen in cross-section, hangs over an adjacent exterior surface of the cushion, wherein the gusset portion includes a first point adjacent to the face contacting portion and a second point adjacent to the non-face contacting portion, and wherein the first point is offset radially outwardly from the second point.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 60/643,115, filed Jan. 12, 2005, the entirety incorporated herein by reference. 
         [0002]    Also, PCT Application No. PCT/AU2005/000850, filed Jun. 15, 2005, is expressly incorporated hereinto by reference in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0003]    The present invention relates generally to the field of masks used for respiratory therapy. In especially preferred embodiments, the present invention relates to respiratory masks having a gusseted cushion. 
       BACKGROUND OF THE INVENTION 
       [0004]    Facial masks are well known for use in continuous positive airway pressure (CPAP) treatment of various respiratory ailments and sleep disordered breathing (SDB), such as, for example, obstructive sleep apnea (OSA) and/or other ventilatory assistance treatments such as noninvasive positive pressure ventilation (NPPV). See, for example, U.S. Pat. No. 4,944,210, the entire content of which is expressly incorporated hereinto by reference. While the present invention will be described below with reference to a full facial mask for use in CPAP treatment, it will be understood that such a reference is non-limiting and is directed toward a particularly preferred embodiment of the present invention. Thus, the various characteristics and advantages of the present invention could equivalently be embodied in another type of mask, such as a nasal mask, or another type of NPPV therapy. 
         [0005]    Apparatus for the treatment of SDB generally involves a blower which delivers a supply of air at positive pressure to a patient interface via a conduit. The patient interface may take several forms, such as a nasal mask assembly and a nasal and mouth mask assembly (i.e., a full face mask). Patients typically wear a mask assembly while sleeping to receive the NPPV therapy. 
         [0006]    Mask assemblies typically include a rigid shell or frame and a soft face-contacting cushion. The cushion cushions the rigid frame from the patient&#39;s face, and provides a seal with the patient&#39;s face. The frame and cushion define a cavity which receives the nose or nose and mouth. The frame and cushion are held in position on the patient&#39;s face by a headgear assembly. The headgear assembly typically comprises an arrangement of straps which pass along both sides of the patient&#39;s face to the back or crown of the patient&#39;s head. 
         [0007]    One problem that arises with existing masks used for CPAP treatments is that over-tightening of the mask straps results in compression of the mask against the wearer&#39;s face which may therefore apply undue pressure force against certain of the wearer&#39;s facial features, such as the wearer&#39;s nose. A poorly fitting mask can leak when pressurized which encourages a patient to tighten the headgear straps excessively which, in turn leads to discomfort, marks on the face and in some cases facial sores. 
         [0008]    The cushion of a patient mask interface can play a key role in the comfort and effectiveness of therapy. The nasal bridge area of the patient&#39;s face has been identified as being particularly sensitive and thus a mask design needs to pay particular attention to such region. 
         [0009]    The issue of mask comfort and effectiveness is particularly apparent when treatment pressure varies, for example, when a patient uses an automatic positive airway pressure (APAP) device such as those commercially available from ResMed Limited under the tradename AUTOSET. When the pressure varies, patients may set the headgear tension for the highest pressure, which thereby leads to unnecessarily high tension being experienced at lower pressures. 
         [0010]    To address such problems, mask systems that vary the sealing force with treatment pressure have been developed, including a nasal mask cushion having a gusset portion, as evidenced by U.S. Published Patent Application 2002/0029780; U.S. Pat. No. 6,772,760 and U.S. Published Patent Application US 2004/0118406, the entire content of each being expressly incorporated hereinto by reference. A commercial embodiment of the inventions described in such patent publications is the ACTIVA™ mask system available from ResMed Limited. 
         [0011]    U.S. Pat. No. 5,074,297 (the entire content of which is expressly incorporated hereinto by reference) describes a respiratory mask assembly for use with intermittent positive pressure breathing treatment and is said to facilitate the formation and automatic adjustment of the seal between a patient&#39;s face and a facial unit of the respiratory mask. 
         [0012]    While the prior proposals for adjustable mask cushions may be satisfactory for their intended purposes, improvements are still needed, especially for a full face mask patient interface. 
       SUMMARY OF THE INVENTION 
       [0013]    Broadly, one embodiment of the present invention is directed to full face masks for use in respiratory therapy wherein a gusset portion is interposed between the mask cushion and the mask frame. The gusset portion thereby allows for relative movement of the mask frame to occur towards and away from a patient&#39;s face to ensure the integrity of sealing contact between the cushion and the patient&#39;s facial features and to maintain a desired comfort level. 
         [0014]    The gusset portion in accordance with the present invention provides several benefits. For example, the gusset portion utilizes the pressure in the mask acting on its increased surface area to provide a force to maintain the face-contacting portion of the cushion in sealing contact with the patient&#39;s face. Of course, the gusset may include a predetermined spring constant that can also affect the force applied to seal against the user&#39;s skin. Additionally, the gusset portion provides in effect a decoupling joint between the face-contacting portion of the cushion and the mask shell thereby allowing some relative movement to occur between the mask and the cushion contacting the patient&#39;s face. This arrangement substantially protects the seal from undue disturbance when the mask or mask shell is tilted; the facial muscles are relaxed, patient movement occurs, and/or movement of the gas supply tube occurs. This decoupling joint provided by the gusset also allows additional travel between the mask shell and the lower cushion which reduces the precision by which the strap length must be maintained. 
         [0015]    The gusset portion of the present invention is especially beneficial in the context of a full face mask since it has at least one perimetrical section which includes generally laterally projecting exterior and interior gusset sections. Both laterally extending exterior and interior gusset sections provide flexibility and increase the allowable travel of the mask frame from the cushion. The laterally projecting exterior section also provides additional sealing pressure to the cushion depending on treatment pressure. Most preferably, the incorporation of the laterally exterior projecting gusset section increases the projected surface area on the patient&#39;s face by at least about 260% compared to the projected surface area of the face-contacting portion of the cushion alone. For example, in an embodiment, the projected surface area of the face-contacting portion alone is about 50 cm 2  and the projected surface area of the gusset section alone is in the range of 30-90 cm 2 , preferably about 80 cm 2 . Thus, the gusset section adds about 80 cm 2  extra area to the cushion or about 160% (80/50) extra area compared to the cushion alone. As a result, the total projected surface area of the gusseted cushion is equal to the summation of the face-contacting portion and the gusset section which is in the range of 80-140 cm 2 , preferably about 130 cm 2  (80+50), and this total area is about 260% (130/50) of the projected surface area of the face-contacting portion alone. 
         [0016]    One aspect of the gusseted cushion according to the present invention is the greater projected area that may be achieved in a particular facial region of the patient which leads to additional sealing force per unit mask pressure that may be obtained at such region. By varying the widthwise extent that the gusset projects laterally outwardly around the perimeter of the mask, the amount of pressure-dependent additional sealing force can be varied since pressure acts upon the additional area from the sealing point of the cushion on the face to the exterior of the gusset and provides a force on the cushion. For example, according to an aspect of the present invention, the sealing force may be reduced in sensitive facial areas of the patient, such as the region of the patient&#39;s nasal bridge by reducing the widthwise extent of the gusset in this region. 
         [0017]    The amount of additional area that the laterally outwardly extending gusset is required to project is also dependent upon the treatment pressure. A relatively large area A g  (e.g. 300 cm 2  when compared to the projected area of the cushion A c  of 50 cm 2 , see  FIG. 8 ) might form a suitable seal at a low pressure of about 4 cmH 2 O, but may be excessive at about 20 cmH 2 O. The overall sealing pressure on the cushion is a combination of the strap tightness and the additional area projected outside the sealing point of the cushion. It has been found that an overall sealing pressure of about 3 kg total force on the entire cushion seal applies excessive force to the patient and hence a projected gusset area should be such that the overall sealing pressure is less than 3 kg. More specifically, the width of the gusset should have a preferred projected area A g  onto the patient&#39;s face of approximately 130 cm 2  when the invention is embodied in a full face mask. 
         [0018]    Another aspect of the gusset is the travel available in a particular patient facial region. Travel allows movement to occur between the frame contacting portion and the patient contacting portion of the cushion between which the gusset is disposed. In general, a cushion in accordance with the invention allows substantially the same amount of travel around the entirety of the cushion&#39;s perimeter so that the frame and patient contacting portions can remain generally parallel. This is achieved by varying the width of the interior projecting gusset or gussets to maintain the amount of travel regardless of the width of the exterior projecting gusset which is tailored to meet the particular sealing force requirements of the facial region. In use there may in fact be non-parallel travel movement of the frame relative to the patient&#39;s face due to the inherent flexibility of their material of construction. In this regard, the gusseted cushions of the present invention most preferably provide between about 5 mm to about 25 mm, advantageously about 16 mm (+/−1 mm), of travel distance when embodied in a full face mask. 
         [0019]    The present invention may be embodied in a cushion for a respiratory mask assembly having a frame-connecting portion, a face-contacting portion, and a gusset portion disposed between and joining the frame-connecting and face-contacting portions. The gusset portion preferably includes at least one perimetrical region which has a laterally projecting exterior gusset section and a laterally projecting interior gusset section. 
         [0020]    According to one aspect, the laterally projecting exterior and interior gusset sections are disposed about the entire perimeter to the gusset portion so as to establish a substantially constant widthwise dimension thereof about the gusset&#39;s entire perimeter. According to another aspect, the laterally projecting exterior and interior gusset sections of the gusset project only along a lower perimetrical region thereof so that the gusset portion has a widthwise dimension which varies about its perimeter. 
         [0021]    In another aspect, the gusset portion has a minimum widthwise dimension at an upper perimetrical region thereof, a maximum widthwise dimension at a lower perimetrical region thereof, and widthwise transitions joining said upper and lower perimetrical regions thereof. The widthwise transitions may be either curvilinear or linear. 
         [0022]    Another aspect of the present invention is a cushion for a respiratory mask having a frame-connecting portion, a face-contacting portion, and a gusset portion disposed between and joining the frame-connecting and face-contacting portions, wherein said gusset portion has a perimeter with a widthwise dimension which varies between at least one region and another perimetrical region thereof. In a preferred aspect, the gusset portion has a minimum widthwise dimension at an upper perimetrical region thereof, a maximum widthwise dimension at a lower perimetrical region thereof, and widthwise transitions (which may be curvilinear or linear) joining such upper and lower perimetrical regions thereof. 
         [0023]    In one specific aspect, the cushion of the present invention substantially zero widthwise dimension at said upper perimetrical region thereof. In accordance with another aspect of the invention, each of the minimum and maximum widthwise dimensions is substantially constant along the upper and lower perimetrical regions, respectively. 
         [0024]    According to another aspect, the invention has an upper perimeter region which occupies between about 15% to about 30% of the entire perimeter of the cushion, a lower perimeter region which occupies between about 50% to about 70% of the entire perimeter of the cushion, and transition regions which occupy between about 10% to about 30% of the entire perimeter of the cushion. 
         [0025]    These and other aspects and advantages will become more apparent after careful consideration is given to the following detailed description of the preferred exemplary embodiments thereof. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]    Reference will hereinafter be made to the accompanying drawings, wherein like reference numerals throughout the various FIGURES denote like structural elements, and wherein: 
           [0027]      FIGS. 1-1 to 1-4  show various views of a full facial mask assembly providing patient interface for respiratory therapy having an embodiment of a gusseted cushion according to the present invention, wherein  FIG. 1-1  is a front plan view thereof,  FIG. 1-2  is a front perspective view thereof,  FIG. 1-3  is left side elevational view thereof, and  FIG. 1-4  is a rear perspective view thereof; 
           [0028]      FIG. 2  is a schematic partial rear plan rear view (patient side) of a gusseted cushion employed in the face mask assembly depicted in  FIGS. 1-1 to 1-4 ; 
           [0029]      FIG. 2-1  is a cross-section of the cushion depicted in  FIG. 2  as taken along line A-A therein; 
           [0030]      FIGS. 2-2 to 2-4  are alternative cross-sections of the cushion depicted in  FIG. 2  as taken along line A-A therein; 
           [0031]      FIGS. 3-1 to 3-3  show various views of a full face mask assembly providing patient interface for respiratory therapy having another embodiment of a gusseted cushion according to the present invention, wherein  FIG. 3-1  is a front plan view thereof,  FIG. 3-2  is a front perspective view thereof,  FIG. 3-3  is right side elevational view thereof; 
           [0032]      FIG. 4  is a schematic partial rear plan rear view (patient side) of a gusseted cushion employed in the mask assembly depicted in  FIGS. 3-1 to 3-3 ; 
           [0033]      FIGS. 4-1 and 4-2  are cross-sections of the cushion depicted in  FIG. 4  as taken along lines A-A and B-B therein, respectively; 
           [0034]      FIGS. 4-3 to 4-5  are alternative cross-sections of the cushion depicted in  FIG. 4  as take along line A-A therein; 
           [0035]      FIGS. 5-1 to 5-3  are various views of a gusseted cushion according to another embodiment of the present invention, wherein  FIG. 5-1  is a top elevation view thereof,  FIG. 5-2  is a right side elevation view thereof, and  FIG. 5-3  is a bottom elevation view thereof; 
           [0036]      FIG. 6  is a schematic partial rear plan rear view (patient side) of the gusseted cushion depicted in  FIGS. 5-1 to 5-3 ; 
           [0037]      FIGS. 6-1 to 6-8  are various cross-sections of the cushion depicted in  FIG. 6  wherein,  FIG. 6-1  is a cross-section taken along line G-G therein;  FIG. 6-2  is a cross-section taken along line A-A therein;  FIG. 6-3  is a cross-section taken along line F-F therein;  FIG. 6-4  is a cross-section taken along line E-E therein;  FIG. 6-5  is a cross-section taken along line D-D therein;  FIG. 6-6  is a cross-section taken along line B-B therein;  FIG. 6-7  is a cross-section taken along line C-C therein; and  FIG. 6-8  is a cross-section taken along line H-H therein; 
           [0038]      FIG. 7  is a plot of sealing force (Kg) on a patient&#39;s face from the cushion versus displacement distance of the mask frame towards the patient&#39;s face (i.e., from a fully expanded state of the gusset to a fully compressed state of the gusset); 
           [0039]      FIG. 8  is a schematic view illustrating the relation between the projected area of the gusset A g  and the projected area of the face-contacting portion of the cushion A c ; and 
           [0040]      FIGS. 9A-9Y  are partial schematic views according to further cushion embodiments of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     First Cushion Embodiment 
       [0041]    An exemplary embodiment of a full facial mask assembly FMA which includes a gusseted cushion  10  according to one embodiment of the present invention is depicted in accompanying  FIGS. 1-1 to 1-4 . The mask assembly FMA includes a mask frame  20  provided with a connection port  22  to which an elbow connector  24  associated with a gas supply conduit may be coupled to allow breathable gas under pressure to be supplied to the mask assembly FMA. The cushion  10  includes distal mask-connecting portion  12 . 1  which connects the cushion  10  to the mask frame  20 , a proximal face-contacting portion  14  and an intermediate gusset portion  16  is between or joining the distal and proximal portions  12 . 1 ,  14 , respectively. The mask cushion  10  may also include a reinforcing member  12  that supports one or more sidewalls of the cushion towards the face-contacting portion  14 . 
         [0042]    Strap connectors  26  extend laterally from the mask frame  20  so as to allow attachment of straps associated with a conventional headgear assembly (not shown) and thereby permit the mask assembly FMA to be secured to a wearer&#39;s head when in use. The mask frame  20  may also be provided with a receiver  28  which is adapted to receive a slide bar associated with a forehead support assembly (not shown), for example, a forehead support assembly of the variety disclosed in commonly owned U.S. Provisional Patent Application Ser. No. 60/735,823, filed Nov. 14, 2005, the entire content of which is expressly incorporated hereinto by reference. A number of vents  30  may be provided so as to allow gas exhaled by the patient to vent to atmosphere. In addition, an auxiliary port  32  may be provided so as to allow the introduction of an auxiliary breathable gas to the mask interior as may be desired, or the port  32  may allow for the measure of pressure within the interior of the mask. 
         [0043]    Accompanying  FIG. 2  and the cross-section thereof as depicted in  FIG. 2-1  show one embodiment of the gusset portion  16  in accordance with the present invention. (Note that  FIG. 2-1  does not include reinforcement member  12 .) In this regard, the footprint area of the full face mask is generally triangular with the apex thereof at the bridge region of the patient&#39;s nose and a base region located generally between the patient&#39;s mouth and chin regions. The cushion  10  is similarly triangularly shaped. As shown in  FIG. 2 , the gusset portion  16  has a substantially constant cross-sectional configuration as depicted in  FIG. 2-1  about its entire perimeter. Stated another way, the gusset portion  16  has a substantially constant lateral dimension about the entirety of its generally triangular perimeter which thereby projects a substantially constant cross-sectional area onto the patient&#39;s face. 
         [0044]    In the embodiment depicted in  FIG. 2  and the cross-section thereof depicted in  FIG. 2-1 , the gusset portion  16  is in the form of an accordion fold having a laterally projecting exterior gusset section  40  and a laterally projecting interior gusset section  42 . The laterally projecting exterior and interior gusset sections  40 ,  42  thus establish respective widthwise dimensions W e , W i  which in use establish the amount of travel and flexibility the gusset provides. The dimension W relating to the exterior gusset section (measured from the cushion contact point to the exterior of the gusset) establishes an area projected on the patient&#39;s face A g  which is about 130 cm 2  or about 260% greater than the projected surface area (about 50 cm 2 ) of the face-contacting portion of the cushion A c  alone as shown in  FIG. 8 . For example, in an embodiment, the projected surface area of the face-contacting portion A c  alone is about 50 cm 2  and the projected surface area of the gusset section (A g -A c ) alone is in the range of 30-90 cm 2 , preferably about 80 cm 2  as shown in  FIG. 8 . Thus, the gusset section adds about 80 cm 2  extra area to the cushion or about 160% (80/50) extra area. As a result, the total projected surface area of the gusseted cushion A g  is equal to the summation of the face contacting portion and the gusset section which is in the range of 80-140 cm 2 , preferably about 130 cm 2  (80+50), and this total area is about 260% (130/50) of the projected surface area of the face-contacting portion of the cushion A c  alone. These dimensions are exemplary in nature to demonstrate the relevant projected areas. 
         [0045]    It is to be understood that the projected surface areas and associated percentage calculations described herein are merely exemplary and other sizes and percentages are possible depending on application. For example, the sizes and percentages described above may be for a medium sized gusseted cushion, and the sizes and associated percentage calculations may be applied proportionally to other sized cushions, e.g., extra small, small, and large. 
         [0046]    It will be observed that the gusset portion  16  according to the embodiment depicted in  FIG. 2  includes, in order from the mask connecting portion  12  toward the face-contacting portion  14 , the exterior gusset section  40  extending generally laterally outwardly and terminating at an exterior tip section  44 , a connecting gusset section  46  extending from the tip section  44  generally inwardly and terminating at an interior tip section  48 , and the interior gusset section  42  extending generally laterally from interior tip section  48  to the base  14 . 1  of face-contacting portion  14 . 
         [0047]    Accompanying  FIGS. 2-2 to 2-4  depict alternative cross-sections that may be provided with the gusset portion  16 . In this regard, any one cross-section or combination of cross-sections depicted in  FIGS. 2-2 to 2-4  may be employed. 
         [0048]    It will be observed in  FIG. 2-2  that the thickness of each gusset section  40 ,  42  and  46  is substantially thicker as compared to the embodiment shown in  FIG. 2-1 . Preferably, the sections  40 ,  42  and  46  of the gusset portion  16  shown in  FIG. 2-2  have a substantially uniform thickness of between about 0.5 mm to about 1.0 mm, whereas the thickness of such comparable sections shown in  FIG. 2-1  is about 0.5 mm or less. 
         [0049]    Alternatively or additionally, the extremities of the sections  40  and  42  where each joins the mask-connecting portion  12  and the face-contacting portion  14 , respectively, may be thickened as shown in  FIG. 2-3 . Again, alternatively or additionally, the inverted portion of the tip section  44  and the everted portion of the tip section  48  may include a thickened region as shown in  FIG. 2-4 . The relative thickness of the tip sections  44  and/or  48  may thus be varied as compared to the sections  40 ,  42  and  46  by the mask designer to achieve desired functions, such as the resiliency or amount of spring force inherently possessed by the gusset portion  16 . 
       Second Cushion Embodiment 
       [0050]    A full facial mask assembly FMA employing another embodiment of a gusseted cushion  10 A in accordance with the present invention is depicted in  FIGS. 3-1 to 3-3  and  FIGS. 4, 4-1 and 4-2 . In this regard, structural components that are similar to those discussed previously have been shown with the same reference numerals. Thus, a detailed discussion of such similar structural components will not be repeated. 
         [0051]    As can be seen in  FIG. 4 , the gusseted cushion  10 A has gusset section  16 A provided with a relatively narrow or constant width region  16 - 1  from a location P 1  adjacent a patient&#39;s nose and around the patient&#39;s nasal bridge region. The gusset section  16 A also has a maximal width region  16 - 2  from a location P 2  generally adjacent a patient&#39;s mouth region around the base of the cushion  10 A. In this regard, compare the width dimensions W 1  and W 2  (i.e., defining respective projected areas) shown in  FIG. 4  for each of the regions  16 - 1  and  16 - 2 , respectively. The width dimensions W 1  and W 2  are measured from the cushion contact point to the exterior of the gusset. A transition region  16 - 3  curvilinearly joins the regions  16 - 1  and  16 - 2  between points P 1  and P 2 . 
         [0052]    The non-uniform width regions W 1  and W 2  thus have the benefits of providing less visual obstruction near the eye region of the patient and less force applied at the patient&#39;s nasal bridge region due to the presence of the minimal width region W 1  thereat. In addition, the center of the applied force against the patient&#39;s face is positioned lower as compared to the substantially constant width gusseted cushion  10  as discussed previously due to the greater projected width area being located physically lower in the gusseted cushion  10 A. 
         [0053]    Thus, as depicted in  FIG. 4-1  there is little or no projected area in the gusset in the nasal bridge region, although travel of the cushion/frame is still permitted due to its generally W-shaped or concertina-type fold establishing a pair of exterior gusset sections  50 ,  52  connected to one another at a tip section  53 , and a pair of interior gusset sections  54 ,  56  connected to the gusset sections  50 ,  52  at tips  57  and  59 , respectively. However, in contrast, the gusset cross-section depicted in  FIG. 4-2  has substantially greater width W 2  due to the generally sinusoidal shape of the gusset section  16 - 2  thereof, and hence a substantially greater projected area onto a patient&#39;s face as compared to the width W 1  of gusset section  16 - 1  near the patient&#39;s nasal region. 
         [0054]    Accompanying  FIGS. 4-3 to 4-5  depict alternative cross-sections that may be provided with the gusset portion  16 A. In this regard, cross-sections depicted in  FIGS. 4-3 to 4-5  may advantageously be employed in gusset sections  16 - 1  and/or  16 - 3  so as to provide for the desired degree of relative resiliency thereof. Moreover, any one cross-section or combination of cross-sections as depicted in  FIGS. 4-3 to 4-5  may be employed as desired. 
         [0055]    In  FIG. 4-3  it will be observed that the thickness of the tip section  53  is greater as compared to the other tip sections  57  and  59 . Alternatively or additionally, the extremities of the apex of tip sections  57  and  59  may each be thickened relative to the other gusset sections as shown in  FIG. 4-4 . Again, alternatively or additionally, each gusset section  50 - 59  according to the alternative cross-section depicted in  FIG. 4-5  is substantially thicker as compared to the embodiment shown in  FIG. 4-1 . In this regard, the thickness of sections  50 - 59  depicted in  FIG. 4-5  is preferably between about 0.5 mm to about 1.0 mm, whereas the thickness of such comparable sections shown in  FIG. 4-1  is about 0.5 mm or less. 
       Third Cushion Embodiment 
       [0056]    Another embodiment of a gusset cushion  10 B in accordance with the present invention is depicted in  FIGS. 5-1 to 5-3 ,  FIG. 6  and the cross-sections thereof shown in  FIGS. 6-1 to 6-8 . In this regard, as is perhaps most clearly shown in  FIG. 6 , the gusset cushion  10 B is comprised of upper and lower arcuately shaped gusset regions  16 B- 1  and  16 B- 2  which are joined to one another by a substantially linear transition region  16 B- 3 . 
         [0057]    As is shown in  FIG. 6  and the cross-sections thereof depicted in  FIGS. 6-1 to 6-8 , the gusset  16 B in accordance with this further embodiment of the present invention has a minimal widthwise dimension around the upper (nasal bridge) region  16 B- 1 , and a substantially constant maximum width along the lower region  16 B- 2  which extends substantially from one cheek bone area of the patient to the other. Substantially linear (straight) side regions  16 B- 3  from generally the nasal bridge area to each cheek bone area of the patient provide widthwise transition sections from the minimal width thereof at upper region  16 B- 1  to the maximum width thereof at lower region  16 B- 2 . Most preferably, the upper region  16 B- 1  occupies between about 15% to about 30% of the cushion&#39;s perimeter distance, and lower region  16 B- 2  occupies between about 50% to about 70% of the cushion&#39;s perimeter distance, with side regions  16 B- 3  occupying the remainder perimeter distance. 
         [0058]    The projected area of the gusset  16 B, A g , is preferably between about 80 cm 2  to about 140 cm 2 , more preferably approximately 130 cm 2 , as measured in its natural molded state (i.e., uncompressed). Of course, the area could be higher or lower, depending on application. In this regard, since little additional sealing force is required in the nasal bridge region, the upper gusset region  16 B- 1  does not necessarily require any projected area, hence the zero or near zero width in that region. Moreover, the substantially straight side regions impart structural stability to the gusset  16 B in the upper region  16 B- 1 . Also, the gusset  16 B in the nasal bridge region has a generally w-shaped cross-sectional configuration (see  FIG. 6-1 ) which may provide spring-like characteristics in use. 
         [0059]    It will be observed in the cross-sections of  FIGS. 6-1 to 6-8  that the gusset  16 B has the same travel distance towards and away from the patient&#39;s face due to the fact that the gusset  16 B has the same effective dimension in the travel direction at any perimetrical location. However, at different perimetrical locations, the exterior and interior lateral projections thereof will vary so as to achieve the minimal width dimension along the upper region  16 B- 1  (see  FIG. 6-1 ), and the maximum width dimensions along the lower region  16 B- 2  (see  FIGS. 6-5 to 6-8 ). Widthwise transitions will however be present along the side regions  16 B- 3  (see  FIGS. 6-2 to 6-4 ). 
         [0060]      FIG. 7  is a plot of sealing force (Kg) on a patient&#39;s face due to contact with cushions in accordance with the present invention versus displacement distance of the mask frame towards the patient&#39;s face (i.e., from a fully expanded (open) travel state of the gusset to a fully compressed state (closed) travel state of the gusset. As is seen, the target travel window of 16 mm (+/−1 mm) achieved by the gussets of the present invention dramatically flatten the pressure curve so as to maintain comfort for the patient and reduce the importance of a particular strap length setting on sealing performance. 
         [0061]      FIGS. 9A-9Y  illustrate further embodiments according to the present invention.  FIG. 9Y  schematically illustrates a partial section of a mask assembly  800  having a cushion including a face contacting/interacting portion  802  that may include a membrane  804  with an optional underlying rim  806 . Cushion includes a non-face contacting portion  808  that is supported by a frame  810 . A central portion  812 , in the form of a black box, is provided between portions  806  and  808 . 
         [0062]      FIGS. 9A-9X  illustrate various central portions that can be used for control portion  812  in  FIG. 9Y . In the case of  FIGS. 9N and 9R , face-contacting interacting portion  808  and/or frame  810  ( FIG. 9Y ) would be adjusted, e.g., widened, to accommodate for illustrated offset. Various features of  FIGS. 9A-9X  are tabulated below in Table 1. 
         [0000]    
       
         
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 Drawings 
                 Comment 
               
               
                   
               
             
             
               
                 FIG. 9A 
                 Circular cross-section. Provides more travel for the same outer area. The 
               
               
                   
                 circular shape will deform less when pressurized, therefore outer area 
               
               
                   
                 remains constant. 
               
               
                 FIG. 9B 
                 Underside notch has dual purpose. On extension provides more travel 
               
               
                   
                 (longer path length), on compression acts as spring. Upperside is tapered 
               
               
                   
                 wall section. 
               
               
                 FIG. 9C 
                 Circular cross-section at end of straight gusset. Provides more travel for 
               
               
                   
                 the same outer area. The circular shape will deform less when pressurized, 
               
               
                   
                 therefore outer area remains constant. 
               
               
                 FIG. 9D 
                 Like FIG. 9C, but with tapered or thickened wall section. When 
               
               
                   
                 pressurized, the thickened wall section tends to keep the form. 
               
               
                 FIG. 9E 
                 Underside notch provides more travel on extension. This is assisted by the 
               
               
                   
                 thickened upper wall which tends to keep the form. This also allows for a 
               
               
                   
                 constant outer area (A g ). 
               
               
                 FIG. 9F 
                 In compression, a spring constant is added. In extension, no spring effect 
               
               
                   
                 (one-sided spring). This has the advantage of having a spring at low 
               
               
                   
                 pressures but not necessarily at high pressures. 
               
               
                 FIG. 9G 
                 Angled gusset provides more travel for the same outer area. 
               
               
                 FIG. 9H 
                 Internal gusset provides more travel for the same outer area. 
               
               
                 FIG. 9I 
                 Thickened section deforms only under higher pressures. At lower 
               
               
                   
                 pressures, thickened section will touch when gusset is compressed and act 
               
               
                   
                 as spring. This has the advantage of having a spring at low pressures but 
               
               
                   
                 not necessarily at high pressures. 
               
               
                 FIG. 9J 
                 Thickened section deforms only under higher pressures. This moves the 
               
               
                   
                 spring tab away from the lower section (i.e., no spring). At lower 
               
               
                   
                 pressures, spring tab will touch when gusset is compressed and act at 
               
               
                   
                 spring. This has the advantage of having a spring at low pressures but not 
               
               
                   
                 necessarily at high pressures. 
               
               
                 FIG. 9K 
                 Thickened section will not deform under pressure, maximizes outer area 
               
               
                   
                 with respect to FIG. 9G. Angled gusset also provides for more travel for 
               
               
                   
                 the same area. 
               
               
                 FIG. 9L 
                 Double gusset provides more travel for the same outer area. 
               
               
                 FIG. 9M 
                 Spring element added. 
               
               
                 FIG. 9N 
                 Attachment point moved outwards. Outer area maintained fixed. 
               
               
                   
                 Underside notch provides more travel (longer path length). 
               
               
                 FIG. 9O 
                 In compression, a spring constant is added. In extension, no spring effect 
               
               
                   
                 (one-sided spring). Note: Similar to but more spring and less expansion 
               
               
                   
                 of the gusset at high pressures. 
               
               
                 FIG. 9P 
                 Angled gusset provides more travel for the same outer area. 
               
               
                 FIG. 9Q 
                 In compression, a spring constant is added. In extension, no spring effect 
               
               
                   
                 (one-sided spring). Similar to FIG. 9F, this has the advantage of having a 
               
               
                   
                 spring at low pressures but not necessarily at high pressures. 
               
               
                 FIG. 9R 
                 Attachment point moved outwards. Outer area maintained fixed. Shape 
               
               
                   
                 of gusset provides more travel (longer path length). 
               
               
                 FIG. 9S 
                 Spring effect in extension. No spring effect in compression. Thick walls 
               
               
                   
                 provide more constant outer area under pressure. 
               
               
                 FIG. 9T 
                 Double internal gusset allows for outer area to be varied from large to 
               
               
                   
                 none while still allowing significant travel. 
               
               
                 FIG. 9U 
                 This cushion cross-section represents a direct translation of the geometry 
               
               
                   
                 of the gusset of the Activa ™ nasal mask onto a full face platform. 
               
               
                 FIG. 9V 
                 Gusset may be provided around entire perimeter of full face cushion. The 
               
               
                   
                 everted gusset does not protrude past the footprint of the cushion. 
               
               
                 FIG. 9W 
                 Starting with the cushion of FIG. 9U, an inverted gusset has been added to 
               
               
                   
                 produce two smaller everted gussets. 
               
               
                 FIG. 9X 
                 A hanging gusset is provided around entire perimeter of full face cushion. 
               
               
                   
                 Gusset molded from an open-shut tool. 
               
               
                   
               
               
                 Notes: 
               
               
                 1 Extension is taken to be movement of frame away from lower cushion 
               
               
                 2 Compression is taken to be movement of frame towards lower cushion 
               
               
                 3 Travel is taken to be amount of extension plus compression 
               
               
                 4 Outer area is taken to be the outer area of the gusset 
               
             
          
         
       
     
         [0063]    While the invention has been described in connection with what are presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the invention. Also, the various embodiments described above may be implemented in conjunction with other embodiments, e.g., aspects of one embodiment may be combined with aspects of another embodiment to realize yet other embodiments. In addition, while the invention has particular application to patients who suffer from OSA, it is to be appreciated that patients who suffer from other illnesses (e.g., congestive heart failure, diabetes, morbid obesity, stroke, barriatric surgery, etc.) can derive benefit from the above teachings. Moreover, the above teachings have applicability with patients and non-patients alike in non-medical applications.