Abstract:
A nasal mask of the type for delivering gas for example to ease or assist the breathing process includes a shell and a cushion connected with the shell. The shell has a side wall and a retaining ring disposed inside the side wall. The side wall and the retaining ring define a gap extending around the shell. The cushion has a side wall with an outer peripheral edge portion including a tongue extending around the cushion. The tongue of the cushion is received in the gap in the shell to secure the cushion to the shell. Various straps assemblies and forehead adjusters for nasal masks are also shown.

Description:
RELATED APPLICATION 
     This application is a continuation in part of U.S. application Ser. No. 10/394,731 filed on Mar. 22, 2003, now U.S. Pat. No. 7,290,546 entitled “Nasal Mask”, having the same assignee as this application, the entire disclosure of which is fully incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention pertains to a nasal mask. Nasal masks may be used to deliver gases of controlled composition, at a controlled pressure, and at a controlled flow rate, to a person&#39;s nasal passages, for inhalation. Gas composition typically is controlled to achieve a particular medical goal, such as anesthesiology or medication or oxygenation. Gas pressure typically is controlled to ease or assist the breathing process, made difficult for example due to high altitude or a medical condition afflicting the user. 
     The nasal mask described here is particularly useful with continuous positive airway pressure (“CPAP”) treatment for sleep disorders, such as obstructive sleep apnea. Pursuant to this treatment the user wears a nasal mask while sleeping. Gas is delivered to the nasal mask at a pressure above atmospheric pressure. This helps the user to breathe more normally during sleep. Further descriptions of CPAP treatments and devices can be found in U.S. Pat. Nos. 5,199,424 and 5,433,193, which are hereby fully incorporated by reference. The mask may be used in the home as well as in institutional settings, such as long term care facilities. 
     The nasal mask described here also is particularly useful in a bi-level or non-invasive ventilator. It may be used to treat chronic obstructive pulmonary disease (COPD), congested heart failure (CHF), and/or gastro esophageal reflux disorder (GERD)). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other features of the present invention will become apparent to one skilled in the art to which the present invention relates upon consideration of the following description of the invention with reference to the accompanying drawings, in which: 
         FIG. 1  is a side elevational view of a nasal mask constructed in accordance with a first embodiment of the invention, shown in use on a user&#39;s head; 
         FIG. 2  is a front elevational view of the mask of  FIG. 1   
         FIG. 2A  is an enlarged schematic view of a portion of the mask of  FIG. 2 ; 
         FIG. 3  is an exploded perspective view of portions of the mask of  FIG. 1  including the shell and the cushion; 
         FIG. 4  is another exploded perspective view of portions of the mask of  FIG. 1  including the shell and the cushion; 
         FIG. 5  is an exploded perspective schematic view showing assembly of the cushion to the shell; 
         FIG. 6  is schematic view showing the cushion assembled to the shell; 
         FIG. 7  is an enlarged sectional view showing portions of the cushion and shell assembled to each other; 
         FIG. 8  is an inside elevational view of the cushion; 
         FIG. 9  is a schematic enlarged view of a side strap connector that forms part of the mask of  FIG. 1 ; 
         FIG. 10  is an elevational view showing the strap connector of  FIG. 9  in a connected condition; 
         FIG. 11  is a view similar to  FIG. 10  showing the strap connector in an unconnected condition; 
         FIG. 12  is a front perspective view of the shell including a fixed part of the forehead support assembly; 
         FIG. 13  is a perspective view of an adjuster that forms a movable part of the forehead support assembly; 
         FIG. 14  is a schematic side elevational view of the portions of the forehead support assembly; 
         FIG. 15  is a sectional view of portions of the forehead support assembly; 
         FIG. 16  is a side elevational view, similar to  FIG. 1 , of a mask including a forehead support in accordance with a second embodiment of the invention; 
         FIG. 17  is a schematic enlarged view of a portion of the forehead support of the mask of  FIG. 16 ; 
         FIG. 18  is a schematic front elevational view of the forehead support portion shown in  FIG. 17 ; 
         FIG. 19  is a front elevational view of a portion of an adjuster portion of a forehead support assembly in accordance with a further embodiment of the invention; 
         FIG. 20  is a sectional view of the adjuster taken along line  20 - 20  of  FIG. 19 ; 
         FIG. 21  is a view similar to  FIG. 20  of a further forehead adjuster and forehead support assembly; 
         FIG. 22  is a view similar to  FIG. 14  of another forehead adjuster; and 
         FIG. 23  is a sectional view of an exhalation opening portion of the mask of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     The present invention relates to a nasal mask. The invention is applicable to masks of differing constructions. As representative of the invention,  FIGS. 1 and 2  illustrate a nasal mask  10  constructed in accordance with a first embodiment of the invention. 
     The mask  10  includes a shell  20 . A forehead support assembly  30  extends upward from the shell  20 . A face cushion  40  is supported on the shell  20 . The mask  10  also includes headgear  80  connected with the forehead support assembly  30  and with the shell  20 , for helping to hold the mask on the user&#39;s head. 
     The shell  20  is preferably made of a rigid plastic material, which is preferably optically transparent and impermeable to gas or air. The shell  20  has a rounded triangular configuration when viewed from the front, being narrower on top by the nasal bridge region and wider by the base of the nose. The shell  20  includes a front wall  22  ( FIG. 4 ) and a side wall  24 . The forehead support assembly  30  extends upward from the side wall  24  of the shell  20 . 
     The front wall  22  and the side wall  24  of the shell  20  define a central chamber  32  in the mask  10 . A circular inlet aperture  34  in the front wall  22  of the shell  20  permits gas to enter the central chamber  32 . A gas inlet tube  36  is rotatably attached to the front wall  22  of the shell  20  so that it covers the inlet aperture  32 . Gas to be delivered to the patient flows into the shell  20  through the gas inlet tube  36 , and into the central chamber  32  in the shell. The cushion  40  covers the wearer&#39;s nose and directs the gas from the central chamber  32  into the user&#39;s nasal passages, while blocking flow of gas out of the sides of the mask  10 . 
     The shell  20  has a plurality of molded-in ribs  42  ( FIGS. 5-7 ) on the inner side surface of the side wall  24 . The ribs  42  are spaced apart around the side wall  24 . Each one of the ribs  42  has an end portion  44  that projects inwardly from the side wall  24  of the shell  20  to form a post. 
     The shell  20  includes a retaining ring  50  for retaining the cushion  40  on the shell. The retaining ring  50  is a one piece molded plastic member that is fixed inside the shell  20 . The retaining ring  50  could be formed in another manner, or made from more than one piece. 
     The retaining ring  50  has a non-planar configuration that closely follows the configuration of the outer peripheral edge of the shell side wall  24 . The ring  50  has a plurality of sleeves  52  spaced apart along the ring at locations that align with the posts  44  on the shell  20 , when the ring is mounted on the shell. 
     To secure the ring  50  to the shell  20 , the sleeves  52  on the ring are heat staked on the posts  44  of the shell. When the ring  50  is secured to the shell  20 , a gap  54  is formed outward of the ring and inward of the side wall  24  of the shell. The gap  54  extends completely around the ring  50  and inside the side wall  24  of the shell  20 . The retaining ring  50  in cross-section has a notch  56  ( FIG. 7 ) presented away from the outer peripheral edge of the sidewall  24  of the shell  20  and toward the side wall of the shell, in a direction along the length of the ribs  42 . 
     The cushion  40  serves two basic functions: user comfort and sealing. Thus the cushion  40  is preferably made from a bio-friendly elastomeric material which is both substantially gas impermeable and elastic enough to conform comfortably to the contours of a person&#39;s face. A preferred material is silicone. The cushion  40  may take any appropriate shape; the shape shown in the drawings is preferred. The cushion  40  is preferably molded as one piece, as shown in the illustrated embodiment. 
     The cushion  40  has a side wall  60 , an inner wall  62 , and an outer wall  64 . The side wall  60  of the cushion  40  extends completely around the cushion. 
     The outer wall  64 , which is the portion of the cushion  40  that contacts the user&#39;s face, extends laterally inward from the side wall  60 . The outer wall  64  has a generally triangular central opening  66 , which receives the user&#39;s nose, for enabling passage of gas from the central chamber  32  of the mask  10  into the user&#39;s nasal passages. The outer wall  64  of the cushion  40  extends completely around the cushion. Thus, when the mask  10  is used, there is complete sealing contact between the outer wall  64  of the cushion  40  and the user&#39;s face. 
     The inner wall  62  of the cushion  40 , like the outer wall  64 , extends laterally inward from the side wall  60 . The inner wall  62  is thicker than the outer wall  64 . As a result, the inner wall  62  is stiffer and stronger than the outer wall  64 . 
     The inner wall  62  of the cushion  40  extends for most, but not all, of the extent of the outer wall  64 . The inner wall  62  is discontinuous (not present) in the region of the nasal bridge. A gap  68  ( FIG. 8 ) is formed between two ends  70  of the inner wall  62 , in the region of the nasal bridge. This gap  68  enables the mask  10  to conform more closely to the user&#39;s face, at the region of the nasal bridge. This also reduces the possibility of irritation by rubbing of the relatively stiff inner wall  62  on the nose, thus providing a more comfortable mask. Although the inner wall  62  does help the sealing function by supporting the outer wall  64 , it is not needed everywhere, and this region is selected to maximize comfort. 
     The side wall  60  of the cushion  40  terminates in an outer peripheral tongue  72  ( FIGS. 5-7 ) of the cushion, for mounting to the shell  20 . The tongue  72  is of a reduced material thickness as compared to the side wall  60 . For example, the thickness of the tongue  72  may be from one quarter to one half the thickness of the side wall  60 . The tongue  72  extends from the side wall  60  by a distance long enough for it to mount releasably in the gap  54  of the shell. 
     The tongue  72  terminates in a retaining flange  74 . The retaining flange  74  extends for the entire extent of the tongue  72 , in a direction transverse to the tongue. In the illustrated embodiment, the retaining flange  74  extends at substantially a right angle to the tongue  72 . The retaining flange  74  may be of the same or substantially the same material thickness as the tongue  72 . 
     The tongue  72  of the cushion  40  is inserted into the gap  54  between the retaining ring  50  and the shell side wall  24  to secure the cushion to the shell  20 . The tongue  72  is inserted far enough into the gap  54  so that the flange  74  on the tongue engages in the notch  56  of the retaining ring  50 . The flange  74  and the tongue  72  are captured between the retaining ring  50  and the side wall  24  of the shell  20 . This engagement holds the cushion  40  on the shell  20 . Because the retaining ring  50  and the gap  54  extend completely around the shell  20 , and the tongue  72  extends completely around the cushion  40 , the cushion is held securely on the shell around its entire extent. 
     The cushion  40  is removable from the shell for cleaning or replacement purposes. The user can pull with enough force to remove the tongue  72  and the retaining flange  74  from the gap  54  between the ring  50  and the shell side wall  24 . In this manner, the cushion  40  is disengaged from the shell  20 . After this is done, the same cushion  40  or another cushion  40  can be inserted and attached to the shell  20 . 
     The headgear  80  of the mask  10  includes two side straps  82  ( FIGS. 1-2  and  9 - 11 ). The side straps  82  are attached to opposite left and right sides of the mask shell  20  in identical manners. The attachment of one strap  82  will be described in detail. 
     The mask shell  20  includes a shell connector  84  ( FIG. 11 ) for receiving the side strap  82 . The shell connector  84  is in the form of a projection from the side wall  24  of the shell  20 . 
     The shell connector  84  includes two side arms  85  that extend outward from the side wall  24  of the shell  20 . The arms  85  are spaced apart from each other. A cross-arm  86  extends between the two arms  85 , at a predetermined distance from the side wall  24 . The cross arm  86  and the arms  85  are substantially co-planar and together define an opening  88  in the shell connector  84 . 
     The shell connector  84  also includes a tab  90 . The tab  90  is a portion of the shell connector  84  that extends from the cross arm  86 , in a direction generally toward the side wall  24  of the shell  20 . The tab  90  also extends out of the plane of the side arms  84 , in a direction away from the user&#39;s face. The tab  90  has an end portion  92  that is spaced apart from the cross arm  86  by a predetermined distance. 
     The headgear  80  includes a strap connector  94  for engagement with the shell connector  84 . The strap connector  94  includes a generally rectangular plastic loop  96  having four legs  98 ,  100 ,  102  and  104 . The inner leg  98  of the loop  96  is secured on the end of the side strap  82  by folding over and connecting with a hook and loop fastener for adjustability. 
     The four legs  98 - 104  of the loop  96  define an opening  108  in the strap connector  94 . The dimensions of the opening  108  are selected so that the shell connector  84  can fit inside and through the opening in the strap connector  94 . 
     The strap connector  94  also includes a tab  110 . The tab  110  of the strap connector  94  extends from the inner leg  98  of the strap connector loop  96 , in a direction into the opening  108 , for a predetermined distance. The tab  110  does not extend completely to the opposite (outer) leg  102  of the loop  96 . Rather, the tab  110  has an end portion  112  that is spaced apart from the outer leg  102  of the loop  96 , defining a gap  114 . The tab  110  of the loop  96  is resiliently bendable relative to the legs  98 - 104  of the loop. 
     The strap connector  94  is engageable with the shell connector  84  to connect the side strap  82  to the shell  20  in a releasable manner. The strap connector  94  is moved into a position adjacent to the shell connector  84  as shown in  FIG. 11 . 
     The tab  90  of the shell connector  84  is then inserted into the opening  108  in the strap connector  94 , with the parts at a substantial angle to each other. The tab  90  of the shell connector  84  is, specifically, inserted into the gap  114  between the tab  110  and the outer leg  102  of the strap connector  94 . 
     The outer leg  102  of the loop  96  engages the side arms  85  of the shell connector  84 . The strap connector  94  is then pivoted downward relative to the shell connector  84 , pivoting generally about the outer leg  102  of the loop  96 . 
     The tab  110  of the strap connector  94  passes under the cross arm  86  of the shell connector  84 . The cross arm  86  and the tab  90  of the shell connector  84  move through the gap  114  between the end portion  112  of the tab  110  on the strap connector  94 , and the outer leg  102  of the loop  96 . 
     The size of this gap  114 , that is, the distance between the end portion  112  of the tab  10  on the strap connector  94 , and the outer leg  102  of the loop  96 , is slightly less than the combined length of the cross arm  86  and the tab  90  on the shell connector  84 . Therefore, the tab  110  on the strap connector  94  must bend or flex by a small amount in order to enlarge this gap so that the tab on the shell connector  84  can pass through the gap. 
     The tab  110  on the strap connector  94  bends, then snaps back to its free position as it passes under the cross arm  86 . This snapping movement is both audible and tactile, and indicates to the user that the side strap  82  is connected to the shell  20 . 
     When the parts are thus connected, the end portion  112  of the tab  110  on the strap connector  94  is disposed in the opening  88  in the shell connector  84 . At the same time, the outer leg  102  of the loop  96  on the strap connector  94  is on the opposite side of the arms  85  of the shell connector  84 . 
     As a result, the shell connector  84  is captured in the loop  96  of the strap connector  94 . This joining of the shell connector  84  with the strap connector  94  secures the side strap  82  to the mask shell  20 . 
     This connection is loose enough so that when the side strap  82  is secured to the mask shell  20 , the loop  96  of the strap connector  94  is pivotable relative to the shell connector  84 . This freedom of movement enables the side straps  82  to be fitted more comfortably to the user&#39;s head. 
     To release the side straps  82 , the user lifts the strap connector  94 , pivoting it upward in a movement generally opposite the pivoting movement used to connect the two pieces. As this pivoting movement occurs, the tab  110  of the strap connector  94  deforms, bending or flexing a small amount as needed to enable it to pass under the cross arm  86  of the shell connector  84 . As it passes, it snaps back to its starting or free position, with an audible and tactile snap. This snap indicates to the user that the side strap  82  is disconnected from the shell  20 . The configuration of the shell connector  84  and the strap connector  94  permits the side strap  82  easily to be attached to and detached from the shell  20 , with a minimal risk that the strap will be accidentally detached during use, for example, as the user moves around during sleep. 
     The forehead support assembly  30  ( FIGS. 12-15 ) of the mask  10  is adjustable. The forehead support assembly  30  includes a support bar  120  and an adjuster  140 . 
     The support bar  120  is a portion of the shell  20  that is fixed to the other parts of the shell including the shell side wall  24 . The support bar  120  includes two spaced apart side walls  122  that define between them a slot  124 . The side walls  122  have an arcuate configuration extending upward and inward from the side wall  24  of the shell  20 . The side walls  122  have respective flanges  126  that extend inwardly toward each other. The center of curvature (or axis)  125  ( FIG. 14 ) of the side walls  124  is spaced apart from the support bar  120  and other parts of the mask shell  20 , rather than being located on the mask. The center of curvature in the illustrated embodiment would be within the user&#39;s head when the mask is in use. 
     The support bar  120  includes a flexible member  130  that extends upward from the shell side wall  24  into the slot  124  between the support bar side walls  122 . The flexible arm  130  is formed as one piece with the shell  20  and the support bar  120 . The flexible arm  130  has an outer end portion  132  that includes two pawls  134  on either side of a button  136 . The button  136  is a portion of the support bar  120  that is manually engageable to effect flexing movement of the flexible arm  130  and thereby movement of the pawls  134  relative to the side walls  122  of the support bar  120 . The pawls  134  are movable with the button  136  upon flexing of the flexible arm  130  in response to application of force to the button. 
     The adjuster  140  is a portion of the forehead support assembly  30  that is supported on the support bar  120  for movement relative to the support bar and the other parts of the shell  20 . The adjuster  140  includes an arcuate engagement portion  142  that has the same center of curvature as the side walls  122  of the support bar  120 . The engagement portion  142  has a laterally extending central wall  144  and two side walls  146  extending from the central wall. The lower portion of the central wall  144  includes an opening  148  for receiving the button  136 . 
     Each one of the side walls  146  has a groove or slot  149  that receives a respective flange  126  of one of the side walls  122  of the support bar  120 . This engagement, and only this engagement, supports the adjuster  140  on the support bar  120  for arcuate sliding movement about the center of curvature  125 . Because the center of curvature  125  is spaced apart from the mask  10  including the shell  20  and the support bar  120 , the adjuster moves in a wide arc. This provides more horizontal movement without much vertical movement, than would an adjuster pivoting about a pivot axis on the shell itself. 
     Each one of the side walls  146  of the engagement portion  142  of the adjuster  140  has a set of inwardly extending (toward the center of curvature) locking teeth  150 . The locking teeth  150  extend from the side walls  146  and are disposed in the slot  124  of the support bar  120 , between the side walls  122  of the support bar. The locking teeth  150  are presented toward and engageable by the pawls  134  of the support bar  120 . 
     The adjuster  140  has an upper end portion  152  that extends upward from the engagement portion  142 . The adjuster  140  has a strip-like or bar-like configuration and, as a result, the upper end portion  152  is not substantially wider than the engagement portion  142 . Thus, the adjuster  140  when viewed from the front (as in  FIG. 2 ) has an I-shaped configuration, rather than a T-shaped configuration. 
     The adjuster  140  ( FIG. 13 ) has left and right slots  154  and  156  in its upper end portion  152 . The slots  154  and  156  extend parallel to each other, through the material of the adjuster  140 , from the front side surface to the back side surface. 
     The headgear  80  of the mask  10  includes a forehead strap assembly  160  ( FIG. 2 ) that, in the embodiment shown in  FIGS. 1 and 2 , includes left and right forehead straps  162  and  164 . The forehead straps  162  and  164  extend outward from a central location, above the shell  20 , wrapping around the user&#39;s forehead, to help secure the mask  10  to the user&#39;s face. The two straps  162  and  164  are identical to each other. The straps  162  and  164  are made from a fairly thick, resilient material, so as to provide a cushioning effect when worn by a user. The two straps  162  and  164  may be joined to each other as one piece, on the side or back of the head. 
     Each one of the slots  154  and  156  in the upper end portion  152  of the adjuster  140  is dimensioned to accept one of the forehead straps  162  and  164 . The left forehead strap  162  is passed through the left slot  154  ( FIG. 2A ) in the forehead adjuster  140 . In a similar manner, the right forehead strap  164  is passed through the right slot  156  in the forehead adjuster  140 . The left strap  162  is brought back on itself to form a loop  166 . An end portion  161  of the left strap  162  is secured to another portion  163  of the left strap  162  with a suitable securing, such as a hook and loop fastener  165 . Use of a hook and loop fastener  165 , as illustrated, provides adjustability for the length of the left forehead strap  162 . The right strap  164  is brought back on itself to form a loop. An end portion  161  of the right strap  164  is secured to another portion  168  of the right strap with a suitable securing, such as a hook and loop fastener  169 . Use of a hook and loop fastener  169 , as illustrated, provides adjustability for the length of the right forehead strap  164 . 
     When the left and right straps  162  and  164  are connected with the forehead adjuster  140  in this manner, a relatively large amount of strap material is present between the forehead adjuster  140  and the user&#39;s forehead. This strap material, as mentioned above, is resilient. Therefore, a substantial cushion is present between the forehead support assembly  30  and the user&#39;s forehead. This cushion provides a very comfortable strap attachment, without the necessity for separate cushion members or cushioning pieces on the adjuster  140 . 
     The engagement of the pawls  134  of the support bar  120 , with the teeth  150  of the adjuster  140 , ( FIGS. 13-15 ) locks the adjuster in position relative to the support bar. To move the adjuster  140  relative to the support bar  120 , the button  136 , which is fixed to the support bar and thereby the shell  20 , is depressed (pushed in, toward the forehead of the user). The flexible arm  130  bends. This bending movement causes the pawls  134  to move inward, out of engagement with the arcuate tooth sets  150  on the adjuster  140 . The adjuster  140  is then free to move relative to the support bar  120 . The user can move (slide) the adjuster  146  to any position within its range of motion, to accommodate varying head configurations including differing front to back distances between the nose and the forehead of the user. Releasing the button  136  allows the pawls  134  to move into engagement with the teeth  150 , thereby locking the adjuster  140  in any selected one of its plurality of possible positions relative to the support bar  120  and the shell  20 . 
     Because the button  136  is mounted on the shell  20 , it can be pushed with one hand or finger that stays in place during the adjustment of the forehead support assembly  30 . There is no need to simultaneously depress the button  136  and move it, which can be a more difficult operation, especially if the user can not directly see the parts, which is the case if the user is trying to adjust the mask  10  while wearing the mask. 
       FIGS. 16-18  illustrate an alternative forehead support assembly  30   a  of a mask  10   a . In the forehead support assembly  30   a , the upper end portion  142   a  of the forehead adjuster  140   a  includes a snap hook  170 . 
     The snap hook  170  has a multiply curved configuration including a body portion  172  and an end portion  174  that curves back toward the body portion. The end portion  174  is spaced apart from the body portion  172  by a predetermined distance to define a gap  178 . The hook  170  is slightly resilient, so that the end portion  174  of the hook is resiliently movable away from the body portion  172 . 
     Associated with the forehead support assembly  30   a  is a forehead strap assembly  80   a  that includes a forehead strap  190  and a stiffener or other type of reinforcing member  180 . A clevis  182  is fixed to the reinforcing member  180 . The clevis  182  has a base  184  and two ends  186 , spaced apart in a forked configuration. A cylindrical pin  188  extends between the ends  186  of the clevis  182 , in a direction parallel to the length of the forehead strap  190 . The pin  188  and the base  184  of the clevis  182  define a passage  192 . The thickness (diameter) of the pin  188  is slightly greater than the width of the gap  178  in the snap hook  170 . 
     To attach the shell  20  to the forehead strap  190 , the user places the snap hook  170  adjacent the pin  188 . The end portion  174  of the hook  170  is moved through the passage  192  in the clevis  182 ; the pin  188  moves through the gap  178  in the hook. As this movement occurs, the snap hook  170  resiliently deforms, with its end portion  174  bending slightly outward, to fit over the pin  188 . After the pin  188  passes through the gap  178  in the hook  170 , the hook resiliently returns to its free state. 
     The snap fit engagement of the hook  170  with the pin  188  secures the forehead support assembly  30   a  to the forehead strap  190 . This helps to hold the mask  10  in place on the user&#39;s face. In addition, the clevis and pin combination supports the hook  170  on the pin  188  for pivotal movement relative to the forehead strap  190 . As a result, the forehead support assembly  30   a  and the forehead strap  80   a  are adjustable relative to each other by pivoting. This pivoting movement can accommodate wearers&#39; foreheads of differing slopes or sizes. 
       FIGS. 19-20  illustrate a second alternative forehead support assembly  30   b  for a mask  10   b . The forehead support assembly  30   b  includes a movable member or adjuster  200  having a T-shaped configuration when viewed from the front, as for example in  FIG. 19 . 
     The T-shaped configuration of the movable member  200  includes a base  202  and two arms  204  that extend laterally from the base. The arms  204  are mirror images of each other. Each arm  204  has a main body portion  206  that has a non-planar configuration (as can be seen in  FIG. 20 ) adapted to a typical forehead curvature. 
     The main body portion  206  of each arm  204  has an inner slot  208  and an outer slot  210 . The inner slot  208  is located closer to the base  202  of the adjuster  200 , and the outer slot  210  is located farther from the base, near the outer end portion  211  of the arm  204 . The slots  208  and  210  extend vertically in the arms  204 . 
     The movable member  200  is made from a relatively hard material so that it can bear the load of the forehead straps. This relatively hard material can be uncomfortable to the user if the movable member  200  rides against the user&#39;s forehead. 
     Located between the slots  208  and  210 , on each arm  204 , is a spacer  212 . The spacer  212  is a portion of the arm  204  that projects, or protrudes, in a direction toward the forehead of the user, from the main body portion  206  of the arm. Thus, the spacer  212  projects toward the center of curvature of the arms  204 . The purpose of the spacer  212  is to keep the forehead adjuster  200 , and specifically the main body portion  206  of the arm  204 , spaced apart from the user&#39;s forehead, to prevent rubbing, irritation, etc. 
     In the embodiment illustrated in  FIGS. 19 and 20 , the spacer  212  is molded as one piece with the main body portion  206 , as a rectangular box-shaped projection. The spacer  212  has an outer end wall  214  that is spaced apart from the plane of the main body portion  206 : The outer end wall  214  is connected with the main body portion of the arm by four side walls  216 , to form the box-shaped configuration. The outer end wall  214  of the spacer  212  is the portion of the arm  204  that is closest to the forehead of the user, closer than the end portion  211  of the arm, even taking into account the overall curved configuration of the arm. 
     The headgear of the mask includes a forehead strap assembly  220  that includes two forehead straps  222 . The forehead straps  222  extend outward from a central location, wrapping around the forehead, to help secure the mask to the user&#39;s face. The two straps  222  are identical to each other. The straps  222  are made from a fairly thick, resilient material, so as to provide a cushioning effect when worn by a user. 
     Each strap  222  is passed through the inner and outer slots  208  and  210  and is brought back on itself to form a loop  224 . The looped strap  222  extends around the spacer  212 , overlying the outer end wall  214  of the spacer. The loop  224  is disposed between the spacer  212  and the forehead of the user. The combination of the spacer  212  and the loop  224  maintains the member  200  in a position spaced apart from (not in contact with) the forehead of the user, even taking into account the overall curved configuration of the arms  204 . 
     In other embodiments, the spacers  212  need not be formed as one piece with the arms  204 . For example, the spacers  212  could be separate elements that are connected with the arms  204  to provide the spacing function. The spacers  212  could also be adjustable in thickness, either within themselves, or by providing separate spacers of differing thicknesses. 
       FIG. 21  illustrates a third alternative forehead support assembly  30   c  of a mask  10   c . In the forehead support assembly, the movable member  230  has a T-shaped configuration when viewed from the front, similar to  FIG. 19 . The T-shaped configuration includes a base and two arms  232  each having an outer end portion  234  with a vertically extending slot  236  that is dimensioned to accept one of the forehead straps  238 . 
     The left forehead strap  238  is passed through the slot  236  in the left arm  232  and is brought back on itself to form a loop  240 . In a similar manner, the right forehead strap  238  is secured to the right arm  232  to form a loop  240  in the right strap. 
     A separate cushioning strap  242  extends between the left and right forehead straps  238 . The cushioning strap  242  may be made from the same material as the left and right forehead straps  238 . The cushioning strap  242  has first and second slots  244  located at opposite ends of the cushioning strap. The loops  240  of the forehead straps  238  extend through the slots  244 . As a result, the cushioning strap  242  is located inward of the forehead adjuster  230 , between the forehead adjuster and the user&#39;s forehead. 
     The cushioning strap  242  is slightly longer than the distance between the two slots  236  at the outer ends  234  of the arms  232  of the forehead piece  230 . The length of the cushioning strap  242  is selected so that when the mask  10   c  is in place, the cushioning strap self-adjusts to a position snug against the user&#39;s forehead and also snug against the arms  232  of the forehead piece  230 . Thus, the cushioning strap  242  provides a cushioning effect for the forehead piece  230 , increasing the comfort level of the wearer of the mask  10   c.    
       FIG. 22  illustrates a forehead adjuster  140   a  that is constructed in accordance with a further embodiment of the invention. The adjuster  140   a  is similar to the adjuster  140  ( FIG. 13 ) and is adjustable in the same manner. The upper end portion  152   a  of the adjuster  140   a , rather than having a planar, bar-shaped configuration like the upper end portion of the adjuster  140 , has a three-dimensional, cut-out configuration. 
     The upper end portion  152   a  of the adjuster  140   a  ( FIG. 22 ) includes three generally vertically extending posts  250 ,  252  and  254  that are spaced apart from each other. The central post  250  is an extension of the central wall  144   a  of the adjuster  140   a  in a vertical direction rather than continuing the arcuate shape of the central wall. The side posts  252  and  254  are vertical extensions of the side walls  146   a  of the adjuster  140   a . The side posts  252  and  254  curve up and forward to meet the central post  250 . 
     A pair of slots are formed in the upper end portion  152   a  of the adjuster  140   a . A right slot  156   a  is defined between the right side post  252  and the central post  250 . A left slot  154   a  is defined between the left side post  254  and the central post  250 . 
     A forehead strap assembly (not shown) can be connected with the adjuster  140   a . A right strap would pass through the right slot  156   a , wrapping around the right side post  252 . A left strap would pass through the left slot  154   a , wrapping around the left side post  254 . Alternatively, a single strap could pass through both slots  154   a  and  156   a , in front of the left and right side posts  252  and  254  and behind the central post  250 . 
       FIGS. 4 and 23  illustrate an exhalation vent portion  260  of the mask  10 . The vent portion  260  includes a thickened wall area  262  in the lower part of the side wall  24  of the shell  20 . Five circular exhalation openings  264  are formed at equally spaced intervals in the thickened area  262 . The exhalation openings  264  extend from the exterior of the mask  10  to the central chamber  32  of the shell  20 . The exhalation openings  264  enable exhaled air to flow out of the mask  10 . 
     The exhalation openings  264  are located below (when the mask is in use) the gas inlet aperture  34 . This location is selected to enable efficient venting of the mask  10 , as it is substantially in line with the nasal passages. It is also an area chosen to minimize annoyance from the exhaled air, either to the user or to a bed partner. 
     The exhalation openings  264  are configured to vent air at a thirty-five degree angle from vertical (thirty five degrees up from straight down, if the user is standing). This angle is 55 degrees from the axis of the gas inlet. This angle is selected to minimize irritation from exhaled air hitting the user&#39;s chest, while also minimizing irritation to someone close by, for example a bed partner. 
     The circular openings  264  provide less noise than a slot. The total flow area of the five openings  264  is selected to optimize venting and pressures in the mask while minimizing noise. 
     From the above description of the invention, those skilled in the art will perceive improvements, changes, and modifications in the invention. For example, the present invention is shown as being incorporated in a nasal mask only. The invention may be incorporated into a combined nasal/mouth mask (a mask with a central cavity  16  and face cushion  14  large enough to encompass the user&#39;s nose and mouth), or in a mouth mask only. Such improvements, changes, and modifications within the skill of the art are intended to be included within the scope of the appended claims.