Patent Publication Number: US-7219670-B2

Title: Method for securing a nasal mask

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   Applicants claim priority to U.S. Provisional Patent Application Ser. No. 60/451,113 filed Feb. 28, 2003. 

   STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
   Not Applicable. 
   TECHNICAL FIELD 
   This invention relates to respiratory masks and more particularly to a nasal mask of the type used for applying a continuous or an intermittent positive pressure to a patient&#39;s respiratory system for treating illnesses, particularly sleep disorders such as obstructive sleep apnea. 
   BACKGROUND OF THE INVENTION 
   Obstructive sleep apnea (OSA) is common sleep disorder suffered by a large number of people. When a person who suffers from OSA has an event, the airway collapses and is blocked, primarily during inspiration. The airway may remain blocked for a few seconds to more than one minute while the person struggles to breath. The person may wake or may move to change his or her sleep position to until the blockage is opened. Severe snoring is frequently a precursor to OSA. During severe snoring, the airflow to the patient&#39;s lungs may be restricted, but not totally blocked. One treatment for OSA is the application of a continuous positive airway pressure (CPAP) to the patient&#39;s respiratory system. This is most frequently accomplished by the patient wearing a nasal mask during sleep which is connected to a source of pressurized air. When a sufficient air pressure is applied to the nasal mask, the patient&#39;s airways become sufficiently inflated and remain open for unrestricted breathing. While evaluating a patient for CPAP treatment, a clinician determines the lowest effective pressure needed for keeping the patient&#39;s airway open during sleep. 
   Various types of CPAP apparatus are well known in the art. The basic CPAP apparatus has a blower which is connected through a pressurized air hose to a nasal mask. The CPAP apparatus is adjusted to provide the lowest effective pressure to the patient for preventing abnormal sleep events. More sophisticated CPAP apparatus includes features such as a ramp delay which applies a reduced pressure to the nasal mask for a period while the patient falls asleep, and then gradually increases the pressure to a programmed level. The CPAP apparatus also may vary the applied pressure to gradually increase the applied pressure in response to sensed sleep events, and to gradually decrease the applied pressure when no sleep events are sensed. In a bi-level form of CPAP apparatus, an effective therapeutic pressure is applied to the nasal mask when the patient begins to inhale and the pressure is reduced when the patient begins to exhale. Bi-level apparatus can increase the comfort of CPAP therapy by reducing the work of exhaling against the therapeutic pressure, particularly for patients who require a high therapeutic pressure. 
   Some patients do not comply with the prescribed CPAP treatment due to mask discomfort where it contacts the face, especially at the bridge of the nose. There has been significant work by CPAP equipment manufacturers to improve mask comfort, since the mask must be worn whenever the patient is sleeping. To be effective, the mask requires a comfortable seal which will adjust to a wide differences in facial configurations of different patients. The seal also must adjust to facial changes when a user changes sleep positions. A number of different seal configurations have been used in the past. These include flexible membranes which can conform to the face and the bridge of the nose, foam filled seals, inflated seals, and seals filled with a gel type material. Each type of seal has positive and negative features. 
   The mask is secured to the patient with headgear which typically is in the form of straps which extend around the head. Preferably, the headgear is designed so that it is easily adjusted by the patient and is easily attached to the patient. The patient should be able to remove the mask during the night and to easily reattach the mask, for example, if the patient needs to go to the toilet. However, many mask/headgear configurations are not easy for the patient to attach and remove. 
   BRIEF SUMMARY OF THE INVENTION 
   The invention is directed to an improved nasal mask and to an improved headgear arrangement for securing the mask to a patient. Although the nasal mask is described herein for use in CPAP therapy for preventing OSA, it will be appreciated that the mask may be used for other therapy and treatments which require a nasal mask for applying a positive gas pressure to a patient&#39;s respiratory system. 
   One feature of the mask is an inflatable seal having a chamber which is at least partially filled with a soft, open cell foam. The seal includes a manually operated pump and a manually operated, normally closed pressure release valve which are mounted on a mask body and are connected to the seal chamber for adjusting the pressure within the seal. By inflating or deflating the seal, the seal is easily customized for patient comfort and for preventing air leaks between the seal and the patient&#39;s face. 
   Another feature of the mask is an adjustable brow bar or forehead support which can be pivoted relative to the mask shell to limit pressure on the bridge of the patient&#39;s nose. An adjustable bridge connects the brow bar to a mask body. The bridge has a pivotal connection to the brow bar. Headgear which attaches the mask to the patient is attached to the brow bar for securing the upper portion of the mask to the patient. The bridge is designed to be easily detached from the brow bar to facilitate removal of the mask from the patient while the brow bar remains attached to the patient. The headgear also includes a lower strap which fits into a recess or over one or more flanges or prongs on a lower portion of the mask shell. If the patient needs to temporarily remove the mask, for example, to go to the toilet or to answer the telephone, the strap is lifted from the recesses or prongs on the lower portion of the mask shell and the adjustable bridge is detached from the brow bar. The headgear and brow bar remain on the patient so that the mask is easily reattached to the patient without requiring reattachment or adjustment of the headgear. It can be difficult for a patient to talk while wearing the mask, since there is a tendency for the pressurized air applied to the nose to flow out the mouth. The patient also may easily lift the strap from the recess and tilt the mask away from the nose, for example, to allow the patient to talk. The lower portion of the mask is easily reattached to continue with the CPAP therapy. 
   Accordingly, it is an object of the invention to provide an improved nasal mask for applying a positive pressure to a mask user&#39;s airway. 
   Other objects and advantages of the invention will become apparent from the following detailed description of the invention and the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a mask according to the invention as seen from the right front side; 
       FIG. 2  is a perspective view of the mask of  FIG. 1  as seen from the back right side; 
       FIG. 3  is a front elevational view of the mask of  FIG. 1 ; 
       FIG. 4  is a right side elevational view of the mask of  FIG. 1 ; 
       FIG. 5  is a left front perspective view of the mask body; 
       FIG. 6  is a right front rear perspective view of the mask body of  FIG. 5 ; 
       FIG. 7  is a left side elevational view of an adjustable bridge for mounting a brow bar on the mask body; 
       FIG. 8  is a right rear perspective view of the adjustable bridge of  FIG. 7 ; 
       FIG. 9  is an enlarged fragmentary view showing details of the adjustable connection between the adjustable bridge and the mask body; 
       FIG. 10  is a right front perspective view of the brow bar; 
       FIG. 11  is a front elevational view of a seal assembly for the mask of  FIG. 1 ; 
       FIG. 12  is rear elevational view of the seal assembly of  FIG. 11 ; 
       FIG. 13  is lower front perspective view of the seal assembly of  FIG. 11 , with the pump and release valve shown in position for engaging the mask body; 
       FIG. 14  is a fragmentary cross sectional view as taken along line  14 — 14  of  FIG. 11  showing details of the cushion pump; 
       FIG. 15  is a fragmentary cress sectional view as taken along line  15 — 15  of  FIG. 11  showing details of the cushion release valve; 
       FIG. 16  is an enlarged perspective view of the elbow lock; 
       FIG. 17  is a fragmentary perspective view of the mask showing the elbow lock securing the elbow to extend towards the top of the mask; 
       FIG. 18  is a fragmentary perspective view showing the mask of  FIG. 1  attached to a patient with headgear; 
       FIG. 19  is a fragmentary perspective view of the patient of  FIG. 14  showing the headgear and brow bar attached to the patient, but with the mask removed; 
       FIG. 20  is a rear elevational view of a modified cushion assembly for a mask according to the invention; 
       FIG. 21  is a front elevational view of the seal assembly of  FIG. 20 ; 
       FIG. 22  is a left side elevational view of the cushion assembly of  FIG. 20 ; 
       FIG. 23  is a right side elevational view of the cushion assembly of  FIG. 20 ; 
       FIG. 24  is a cross sectional view as taken along line  24 — 24  of  FIG. 20 ; 
       FIG. 25  is a cross sectional view through the pump and the pressure release valve as taken along line  25 — 25  of  FIG. 21 ; 
       FIG. 26  is an enlarged cross sectional view through the pressure release valve; 
       FIG. 27  is an enlarged fragmentary bottom elevational view through a modified bridge for a mask according to the invention showing details of the end which attaches to the brow bar; 
       FIG. 28  is an enlarged bottom view of the bridge of  FIG. 27 ; 
       FIG. 29  is a fragmentary top plan view showing details of the connection of the bridge of  FIG. 27  to the mask shell; 
       FIG. 30  is a side elevational view of the mask showing details of the connection of between the bridge and the mask shell, with the bridge shown in its uppermost position; and 
       FIG. 31  is a side elevational view similar to  FIG. 30 , but with the bridge shown in its lowermost position. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to the drawings,  FIGS. 1–4  show a nasal mask  10  according to a first embodiment of the invention for applying a positive gas pressure to a patient&#39;s respiratory system. The mask  10  is of a type which may be worn by a patient during sleep for treating sleep disorders, such as sleep apnea. The mask  10  is used for applying either a continuous or an intermediate positive air pressure from CPAP apparatus to the patient&#39;s respiratory system to prevent soft tissues from collapsing and blocking the passages during breathing, for example, for preventing OSA. However, it will be appreciated that the nasal mask  10  may be used for applying a positive gas pressure to a patient&#39;s airway for other medical purposes. 
   The mask  10  includes a body  11  and a cushion  12  which has a central opening  13  for receiving the patient&#39;s nose. Preferably, the cushion  12  is removable from the mask body  11  to facilitate cleaning and replacement. The cushion  12  has a contour which generally conforms to the contour of an average person&#39;s face around the nose. A collar  14  is shown for securing the cushion  12  to the mask body  11 . However, it should be appreciated that other known mask cushion attachment methods also may be used. An elbow  15  is attached to a front of the body  11  to rotate about an axis  16 . A swivel connector  17  is connected to an end  18  of the elbow  15  for attachment to an air hose (not shown) which delivers pressurized air to the patient from conventional CPAP apparatus (not shown). 
   A vent  19  is shown mounted on the elbow  15 . The illustrated vent  19  is of the type described in U.S. Pat. No. 6,435,181. However, the vent  19  does not form a part of the invention and other known types of CPAP mask vents also may be used with the mask  10 . It should be understood that the vent  19  may be attached to or may be an integral part of the mask body  11  rather than on the elbow  15 , as illustrated. 
   Many users of CPAP masks have discomfort where the mask presses on the bridge of the user&#39;s nose. The headgear which attaches the mask to the patient frequently has a point of attachment to the mask at or adjacent the bridge of the nose. This is necessary to keep the mask sufficiently tight to form a seal between the cushion and the irregular facial surfaces at the bridge of the nose. Excessive pressure on the bridge of the nose can be painful for the user. The discomfort is aggravated by the fact that the mask is typically worn at night for 6 to 8 or more hours. One method for reducing the pressure on the bridge of the nose has been to mount a pad on an extension from the top of the mask body. The pad rests against the patient&#39;s forehead to limit the pressure on the bridge of the nose, to help maintain a constant mask seal position relative to the face, and to provide support for the upper portion of the mask  10 . However, such a mask requires different configurations for fitting different patients. Masks of this type have been adapted for different patients by using different thickness pads or by providing some form of adjustment in a mounting assembly for the pads. This allows setting the angle of the mask body relative to the bridge of the nose. 
   According to one feature of the invention, the mask  10  is provided with one or more pads  20  mounted on a brow bar  21 . The pads  20  are adapted to rest against the patient&#39;s forehead. An adjustable bridge  22  connects between the mask body  11  and the brow bar  21 . The illustrated bridge  22  is mounted to rotate on the mask body  11  and is designed to lock in a number of different rotational positions for adjusting to different user facial configurations. The user presses on tabs or buttons  23  on the bridge  22  for releasing the lock between the bridge  22  and the body  11  during adjustment of the angular position of the bridge  22  relative to the body  11 . The brow bar  21  is mounted to pivot on the bridge  22  so as to self align with foreheads of different users. The bridge  22  also includes release tabs or buttons  24  which, when squeezed, allows the bridge  22  to be separated from the brow bar  21 . The upper portion of the mask  10  can be adjusted for a specific user relative to the user&#39;s forehead by positioning the mask over the user&#39;s nose in a position wherein the cushion  12  forms a seal around the nose, pressing on the buttons  23  to unlock the bridge  22 , rotating the bridge  22  until the brow bar  21  rests against the user&#39;s forehead, and releasing the buttons  23  to lock the bridge position. 
   According to another feature of the invention, the mask  10  is provided with a novel cushion  12  for forming a comfortable seal between the mask  10  and a user&#39;s face. The cushion  12  is in the form of a highly flexible tube  25  which is secured to the mask body  11  with the collar  14 . The tube  25  may be secured to the collar  14  which in turn is secured to the mask body  11 . A pump  26  is attached to the tube  25  for inflating the tube  25 , and a pressure release valve  27  is attached to the tube  25  for deflating the tube  25 . The pump  26  and the valve  27  are mounted to extend through openings on opposite sides of the mask body  11 . Preferably, the tube  25  is at least partially filled with a soft open cell foam which helps press the cushion  12  against the facial surfaces of a mask user when the cushion is uninflated or partially inflated. 
   Referring to  FIGS. 5 and 6 , details of the mask body or shell  11  are shown. The body  11  has an opening  32  surrounded by a rim  33  which is shaped to substantially conform to an average user&#39;s facial configuration surrounding the nose. The cushion  12  accommodates facial variations. Optionally, the mask manufacturer may offer two or more mask shells  11  and cushions  12  of different sizes and shapes to further accommodate different facial configurations. A lower portion  33   a  of the edge  33  is designed to extend below the user&#39;s nose across the upper lip. Side portions  33   b  and  33   c  extend generally along the sides of the nose and an upper portion  33   d  extends over the bridge of the user&#39;s nose. 
   The cushion  12  is designed to be positioned against and to be secured to the rim  33  by the collar  14  which snaps over or otherwise engages the rim  33 , as is well known in the art. Opposite the opening  32 , the body  11  forms a circular opening  34  in which the elbow  15  is mounted to rotate about the axis  16 . An opening  35  is formed through one side of the body  11  for receiving the pump  26  which inflates the cushion  12 , and an opening  36  is formed through the opposite side of the body  11  for receiving the release valve  27 . The pump  26  may consist of a resilient, semi-spherical bulb which frictionally engages the opening  35  and the release valve  27  may have a generally tubular exterior which frictionally engages the opening  36 . The bases of the pump  26  and the release valve  27  may form groves which retain the pump  26  and the release valve  27  on the body  11 . 
   One or more flanges or prongs  37  (two shown) are formed on the body  11  to extends away from the lower portion  33   a . A groove or recess  38  is formed between the flanges  37  and the body  11 . An elastic lower headgear strap is positioned in the recess  38  for holding the lower end of the mask  11  against the patient&#39;s upper lip, as will be discussed in greater detail below. 
   Referring to  FIGS. 5–9 , the mask body  11  also includes a bracket  39  to which the adjustable bridge  22  is attached. The bracket  39  includes a block  40  in which a hole  41  is formed. The bridge  22  has two spaced, parallel extensions  42  and  43 . The extensions are resilient and include aligned, inwardly directed pins  44  which are adapted to engage the opening  41  on the block  40 . This provides a pivotal connection securing the adjustable bridge  22  to the body  11 . At an upper end, the bracket  39  has two spaced, parallel ribs  45  and  46 . The ribs  45  and  46  have notched opposing inner surfaces  47  and  48 , respectively. 
   As best seen in  FIG. 8 , the bridge  22  has two generally parallel, resilient, cantilevered arms  49  and  50  adjacent the extensions  43  and  44 , respectively. Preferably, ends of the arms  49  and  50  are shaped to define the buttons  23 . The ends of the arms  49  and  50  also have spaced tabs  51  and  52 , respectively. When the bridge  22  is attached to the body  11 , the tab  51  engages the notched surface  47  and the tab  52  engages the notched surface  48  to prevent rotation of the bridge  22  relative to the body  11 . The angular position of the bridge  22  relative to the body  11  is adjusted by squeezing together the buttons  23  the move the tabs  51  and  52  out of engagement with the notched surfaces  47  and  48 . Once the bridge  22  is in a desired position, the buttons  23  are released and the tabs  51  and  52  engage the notched surfaces  47  and  48  on the bracket  39  to lock the angular position of the bridge  22  relative to the body  11 . 
     FIGS. 7 ,  8  and  10  show details of the brow bar  21  and of the connection between the brow bar  21  and the bridge  22 . The bridge  22  also includes two generally parallel resilient cantilevered arms  53  and  43  which extend towards a brow bar mounting end  55  and which are shaped to define the tabs  24 . Axially aligned outwardly directed pins  56  are formed on the arms  53  and  54 . The brow bar  21  has a surface  57  on which the pads  20  are mounted, for example, with a suitable adhesive, or with other known methods. The pads  20  are formed from a material which will readily conform to the user&#39;s forehead and will be comfortable when the mask  10  is worn for a long period of time. For example, the pads  20  may be gel filled or fluid filled pockets, or of a suitable resilient foam material. If the pad or pads  20  are of a foam material, the surface of the pads  20  which contacts the mask user&#39;s forehead may be covered with a soft, comfortable fabric. 
   The brow bar  21  has two generally parallel spaced flanges  58  and  59  extending above a surface  60 . Aligned openings  61  are formed in the flanges  58  and  59  for receiving the pins  56  on the bridge  22 . The tabs  24  on the bridge  22  may be squeezed together to permit insertion of the pins  56  into the openings  61  and released to connect the brow bar  21  to the bridge  22 , while permitting the brow bar  21  limited rotation relative to the bridge  22 . Preferably, ends  56 ′ of the pins  56  are angled inwardly towards the bridge end  55 . The angled ends  56 ′ act as cams to deflect the pins  56  towards each other to allow the bridge end  55  to be easily pushed into the space between the flanges  58  and  59  until the pins  56  engage the openings  61  without having to depress the tabs  24 . Thus the bridge  22  is easily attached to the brow bar  21  after the brow bar  21  and the headgear are secured to the user. The brow bar  21  also has opposed upturned ends  62 , each of which has a slot  63  for attachment to headgear, as will be discussed in greater detail below. 
     FIGS. 11–15  show details of the cushion  12  with the integral pump  26  and pressure release valve  27 . The cushion  12  is mainly formed from two sheets  66  and  67  of a suitable plastic material which can be vacuum formed or otherwise shaped to provide a desired shape. The sheet  66  is sufficiently thin and flexible to readily conform to the mask user&#39;s facial surfaces around the nose. The sheet  66  is formed to define a continuous recess  68  which defines a central opening  69  which receives the user&#39;s nose. A similarly shaped piece of soft, open cell foam  70  at least partially fills the recess  68 . The sheet  67  is positioned over the sheet  66  and the sheets  66  and  67  are sealed together around both sides of the recess  68  to form the inflatable facial seal tube  25 . The foam  70  is resilient and helps press the surface of the sheet  66  into facial crevices to maintain a seal between the mask  10  and the user&#39;s face when the seal tube  25  is deflated or only partially inflated. The foam  70  provides a baseline support and facial seal, while the inflation provides the extra or “topping” seal effect to customize the seal to the user&#39;s face. Without the foam  70 , a partially inflated seal could develop deflated areas which do not adequately seal to the user&#39;s face. The sheet  67  may be generally flat and heavier than the sheet  66  to provide a surface which abuts the mask body  11  when the seal  12  is attached with the collar  14 . 
   The pump  26  is formed between the sheets  66  and  67  to extend into the seal nose opening  69 . The pump  26  includes a bulbous portion  71  formed in the sheet  67 . The sheet  66  forms a generally flat bottom  72  to the pump  26 . The bulbous portion  71  may be reinforced with a sufficiently resilient material to help the bulbous portion  71  to regain its original shape after it is pressed and released. The space between the bulbous portion  71  and the sheet  66  forms a pump chamber  73 . A reinforced air inlet port  74  is formed through the bottom  72 . A generally flat resilient valve member  75  is positioned over the port  74 . The pump chamber  73  is filled with a resilient open cell material  76  which urges the bulbous portion  71  to its normal shape and also urges the valve member  75  to close the port  74 , forming an inlet check valve. The sheets  66  and  67  include an extended portion  77  which forms a passageway  78  connecting the pump chamber  73  to the tube  25 . A check valve  79  is located in the passageway  78  to limit air flow only to the direction from the pump chamber  73  to the tube  25 . Consequently, when the bulbous portion  71  is depressed, air is forced from the chamber  73  through the passageway  78  and the check valve  79  into the tube  25 . When the bulbous portion  71  is subsequently released, air is drawn through the port  74 , past the valve member  75  and into the pump chamber  73  as the bulbous portion  71  returns to its normal position. When the cushion  12  is attached to the mask body  11 , the extended portion  77  is bent to allow insertion of the bulbous portion  71  of the pump  26  into the mask body opening  35 . 
   The pressure release valve  27  also is connected to an extended portion  80  of the sheets  66  and  67  which extends into the seal nose opening  69 . When the cushion  12  is attached to the mask body  11 , the extended portion  80  is bent to allow insertion of the release valve  27  into the mask body opening  36 . The release valve  27  generally includes a tubular body  81 , a valve seat  82  formed within the body  81 , a valve member  83  and a spring  84 . The valve member  83  has a shank  85  which extends through an opening  86  in the valve seat  82 , an enlarged end  87  on the stem  85  which normally closes the opening  86 , and an enlarged end which forms a valve operating button  88 . The button  88  is adapted to be pushed to open the release valve  27 . The spring  84  is compressed between the valve operating button  88  and the valve seat  82  to normally urge the valve member end  87  against the seat  82  to cover the opening  86 . The portion  80  of the sheets  66  and  67  forms a passage  89  which connects the tube  25  with a chamber  90  in the release valve  27 . When the valve operating button  88  is manually pushed, the end  87  separates from the seat  82 , allowing air to vent from the tube  25  through the passage  80 , the chamber  90  between the valve stem  85  and the opening  86  and between the valve operating button  88  and the valve body  81 . 
   As previously indicated, pressurized air flows from a supply hose (not shown) through the swivel connector  17  and the elbow  15  into the mask body  11 . Normally, the elbow  15  is free to rotate on the mask body  11  about an axis  16 . For some applications, it is desirable to use headgear for attaching the mask  10  to the patient which holds the air supply hose to extend above the mask  10  and over the top of the user&#39;s head. In this application, it may be desirable to lock the elbow  15  in a position where it is directed upwardly generally parallel to the bridge  22 . 
   As best seen in  FIGS. 1 ,  3 ,  16  and  17 , an elbow lock  95  is mounted on the body  11  to rotate between an unlocked position as shown in  FIGS. 1 ,  3  and  4 , and a locked position as shown in  FIG. 17 . The lock  95  has an elongated cross member  96  with perpendicular extensions  97  and  98  from opposite ends. Aligned holes  99  and  100  are formed in the extensions  97  and  98 , respectively. The extensions are spaced apart for fitting between the extensions  42  and  43  on the bridge  22  and the holes  99  and  100  are sized to pass the pins  44 . The pins  44  secure the lock  95  to the mask body  11  while permitting the lock  95  to rotate on the pins  44 . The cross member  96  has a curved upper surface  101  which is adapted to engaged the curved exterior of the elbow  15  when the elbow  15  is locked in the position shown in  FIG. 17 . When the elbow lock  95  is in the unlocked position, the cross member  95  will be located in a recess  102  ( FIG. 5 ) in the body bracket  39  and the elbow  15  is free to rotate relative to the mask body  11  about the axis  16 . The elbow  15  is locked by moving to the upward position as shown in  FIG. 17  and rotating the lock  95  to the position shown in  FIG. 17 . A raised boss  103  on the elbow  15  retains the lock  95  in the locked position. 
     FIGS. 18 and 19  illustrate securing the mask  10  to a user with headgear  108 . The headgear  108  includes an upper strap  109  having two ends  110  and  111  which are attached to the brow bar  21 . As is known in the art, the headgear ends  110  and  111  may be provided with hoop and look fasteners, such as Velcro fasteners. The ends  110  and  111  are passed through the slots  63  ( FIG. 10 ) on the brow bar  21 , adjusted for the size of the user&#39;s head, and secured with the hook and loop fasteners. The headgear  108  also includes a lower strap  112  which also has a length which can be adjusted with hook and loop fasteners. The lower strap  112  is positioned in the recess  38  between the flanges or prongs  37  and the mask body  11  to attach the lower end of the mask  10  to the user. The straps  109  and  112  are elastic to provide sufficient tension to maintain a seal between the mask  10  and the user. 
   The mask  10  can be removed from a user while leaving the headgear  108  attached by lifting the lower strap  112  out of the recess  38  and squeezing the release tabs  24  to separate the bridge  22  from the brow bar  21 .  FIG. 19  shows the headgear  108  and the brow bar  21  attached to the user&#39;s head with the mask  10  removed. This leaves the user disconnected from the CPAP apparatus and free to get out of bed. When the user returns to bed, it is a simple matter to reattach the bridge  22  to the brow bar  21  and to lift the lower headgear strap  112  into the recess  38 . No other mask or headgear adjustments are required when reattaching the mask  10 . Since the mask  10  can be removed from the user without removing or changing the position of the headgear  108  on the user, a facial seal is obtained when the mask is reattached to the headgear without having to reposition the headgear. 
   Referring now to  FIGS. 1 ,  3 ,  5  and  9 , the mask  10  also may include an auxiliary gas inlet  113  ( FIG. 9 ) which, when needed, can be connected to a source of supplemental oxygen. The auxiliary gas inlet  113  is connected to a conventional nipple (not shown) which is located in a recess  114  ( FIG. 5 ) in the bracket  39 . When the auxiliary gas inlet  113  is not needed, the recess  114  is closed by a cap  115 , as shown in  FIGS. 1 and 3 . Since the gas inlet  113  communicated directly with the interior of the mask body  11 , it will be appreciated that the gas inlet  113  also may be connected to a pressure sensor for monitoring mask pressure during use. 
     FIGS. 20–26  show details of a modified embodiment of a cushion  118  for the mask  10 . The cushion includes a soft flexible sheet  119  of plastic material which is vacuum formed or otherwise shaped to define a recess  120  which extends around a nose receiving opening  121 . The recess  120  is closed by a second sheet  122  of plastic material to form an inflatable and deflatable tube  123 . The sheet  122  may be somewhat heavier than the sheet  119 . Alternately, the sheets  119  and  122  may be replaced with a single sheet of soft flexible plastic material in which the tube  123  is formed and the sheet is folded over to close the tube  123 . Preferably, the portions of the cushion which contact a mask user&#39;s face are made from plastic materials of a type which are commonly used in nasal masks. These materials are soft, flexible, resistant to facial oil faces and non-allergenic. 
   Before securing the sheet  122  to the sheet  119 , a ring of open cell resilient foam  124  is placed in the recess  120 . The sheet  122  is then secured to a collar  125 . The collar  125  is releasably attached to the above described mask shell or body  11  via a groove  126  which frictionally engages the shell rim  33  around the opening  32  ( FIG. 6 .). The groove  126  may have an enlarged portion  127  which receives the mask body rim  33  to retain the cushion  118  on the mask body  11 . It will be appreciated that other techniques may be used for attaching the inflatable tube  123  to extend around the mask shell rim  33 . 
   The sheets  119  and  122  have an extended portion  128  which extends into the nose opening  121  and forms a passage  129  which communicates with the interior of the tube  123 . A pump  130  for inflating the tube  123  and a pressure release valve  131  for deflating the tube  123  are formed as a unit  133  ( FIG. 25 ) which is connected to the extended portion  128 . The unit  133  includes two sheets of flexible plastic  134  and  135  which are connected together along their edges  136 , except at an end  137 , to form a chamber  138 . The end  137  is attached to the extension  128  so that the passage  129  communicates with the chamber  138 . The unit  133  is configured and is attached to the extension  128  so that the release valve  131  and the pump  130  can be inserted into openings  36  and  35  ( FIG. 6 ), respectively, in the mask body  11 . 
   As shown in  FIG. 25 , the pump  130  includes a resilient dome  140  which is filled with a resilient, open cell foam  141 . The dome  140  has an air inlet opening  142 . The foam  141  presses a resilient disk  143  over an interior side of the opening  142  to form an air inlet check valve  144 . When the dome  140  is released after being depressed, air is drawn through the opening  142  and past the disk  143  into an interior  145  of the dome  140  as the dome  140  expands to its original shape. The dome  140  has a perimeter  146  which is attached to the sheet  134 . An annular groove  147  is formed in the dome  140  adjacent to the perimeter  146  for engaging the mask body  11  when the dome  140  is inserted into the mask body opening  35  ( FIG. 6 ). An air outlet opening  148  connects the dome interior  145  with the chamber  138 . A resilient disk  149  located in the chamber  138  is pressed over the opening  148  to form an outlet check valve  150 . When the dome  240  is depressed, air in the interior  145  is forced through the opening  148 , past the check valve  150 , through the chamber  138  and the passage  129  into the inflatable tube  123 . 
     FIGS. 25 and 26  show details of the release valve  131  which vents air from the inflatable tube  123 . The valve  131  has a housing  153  which is formed from a resilient material, such as a resilient rubber or plastic material. The housing  153  has a flange  154  which is bonded or fused to the sheet  134 . An annular groove  155  is formed to extend around the housing  153  adjacent the flange  154 . When the release valve  131  is inserted into the mask body opening  36  ( FIG. 5 ), the perimeter of the opening  36  extends into the groove  155  to retain the release valve  131  in the opening  36 . 
   The valve housing  153  has an interior portion  156  which is located in the chamber  138  and a tubular exterior portion  157  which is open to atmosphere. A web  158  separates the interior portion  157  from the exterior portion  158 . An opening  159  extends through the center of the web  158 . A valve member  160  is positioned in the housing  153 . The valve member  160  has a shank  161  which extends through the opening  159 . The shank  161  has a smaller diameter than the opening  159  so that air can flow between the shank  161  and the wall of the opening  159 . The valve member  160  has a valve operating button  162  located on an exterior end of the shanks  161 . A gap  163  is formed between the button  162  and the valve housing  153 . The shank  161  has a bulbous portion  164  which is located on an interior side of the web  158 . The bulbous portion  164  is sized and shaped to block the opening  159  when in contact with the web  158 . A compression spring  165  is positioned between the valve operating button  162  and the web  158  to urge the bulbous portion  164  against the web  158  to close the valve  131 . When the button  162  is pushed, air from the inflatable tube  123  is vented through the passage  129 , the chamber  138  and the valve  131  to atmosphere. 
   When the mask is first used by a patient, the pump  130  and the pressure release valve  131  are used to increase and decrease the inflation of the tube  123  until the patient finds the most comfortable and effective facial seal. The inflation of the tube  123  may not need future adjustment, unless the patient experiences some discomfort from the mask pressure. 
     FIGS. 27–31  show a modified structure for connecting the brow bar  21  to a mask body  168 . The structure includes a modified bridge  169  which has an end  170  which is releasably connected to the brow bar  21  and an end  171  which is attached to the mask body  168 . The bridge  169  is molded from a resilient plastic material. The bridge  169  has a pair of spaced resilient arms  172  which project towards the end  170 . Axially aligned pins  173  project outwardly from adjacent free ends of the arms  172  for engaging the aligned openings  61  ( FIG. 10 ) on the brow bar  21 . Each arm  172  has a knob or tab  174  for use in disengaging the bridge  169  from the brow bar  21  by squeezing the tabs  174  together. Preferably, ends  175  of the pins  173  are angled or curved towards the bridge end  170  to act as cam surfaces which will push the pins  173  towards each other as shown in  FIG. 27 , bending the arms  170 , as the bridge  169  is pushed into the brow bar  21 . This allows easy attachment of the mask to the brow bar without the need to squeeze the tabs  174 . The connection between the bridge end  170  and the brow bar  21  permits limited rotational movement of the brow bar  21  relative to the bridge  169 . This allows the brow bar  21  to self align with a mask user&#39;s forehead for different forehead shapes. 
   It will be appreciated that the bridge end  170  may be modified so that the aligned pins  173  project inwardly towards each other and that the brow bar can be provided with a single opening (not shown) having opposed ends which are engaged by the pins to releasably connect the bridge to the brow bar while permitting the brow bar to rotate on the pins to align with a mask user&#39;s forehead. 
   The bridge  169  has a pair of spaced parallel resilient arms  176  extending to the end  171 . A pair of aligned pins  177  project from free ends of the arms  176  towards one another adjacent the bridge end  171 . A second pair of aligned pins  178  project towards one another from an intermediate location on the arms  176 . A lock member  179  is mounted on the bridge  169  for locking the position of the bridge  169  relative to the mask body  168 . The lock member  179  is mounted on the bridge  169  for limited movement in a generally longitudinal direction along the bridge  169 . Two resilient fingers  180  on the lock member  179  engage tabs  181  on the bridge  169 . The tabs  181  act as springs urging an end  182  of the lock member  179  towards the bridge end  171 . The lock member  179  also included opposed knobs  183 . The knobs  183  can be grasped by a mask user to manually move the lock member  179  a short distance towards the bridge end  170  against the force of the resilient fingers  180 , moving the lock member end  182  away from the bridge end  171 . 
     FIGS. 30 and 31  show the bridge  169  attached to the modified mask body  168 . The pairs of pins  177  engaging laterally spaced parallel slots  184  in the mask body  168  and the pins  178  laterally engaging spaced parallel slots  185  in the mask body  168 . The slots  184  and  185  are arranged at an angle relative to each other, preferably with the slots  184  generally perpendicular to the face of a mask user and the slots  185  generally parallel to the face of a mask user. As a consequence of having an angular relationship between the slots  184  and  185 , the angle of the bridge  169  is adjustable relative to the mask body  168 . 
   The bridge  169  is shown in its furthest upper position in  FIG. 30  and in its furthest lower position in  FIG. 31 . When the bridge  169  is moved from the position of  FIG. 30  to the position of  FIG. 31 , the pins  177  move down in the slots  185  and the pins  178  move to the left in the slots  185 . Alternately, when the bridge  169  is moved from the position of  FIG. 31  to the position of  FIG. 30 , the pins  177  move up in the slots  184  and the pins  178  move to the right in the slots  185 . Thus, the bridge  169  does not pivot about an axis as it is adjusted. The position of the bridge  169  is adjusted to accommodate the configuration of a mask user&#39;s nose bridge and forehead in order to obtain the best facial seal at the nose bridge without placing excess pressure on the nose bridge. By allowing the brow bar to pivot on the bridge pins  173 , the brow bar will self align with the adjacent angle of the mask user&#39;s forehead. 
   The mask body  168  is provided with a plurality of notches  186  which are arranged in a row extending generally parallel to the slot  184 . The notches  186  may be spaced in a plane or along a slightly curved surface. The end  182  of the lock member  179  normally engages one of the notches  186  to lock the orientation of the bridge  169  relative to the mask body  168 . When the knobs  183  are moved towards the bridge end  170 , the lock member end  182  disengages the notches  186  to permit adjustment of the position of the bridge  169 . The mask body  168  is shown with four notches  186  to allow four positions for the bridge  169 . It will be appreciated that fewer or more notches  186  may be provided. 
   A pressurized gas inlet elbow  189  is mounted on the mask body  168  for rotation about an axis  190 . Preferably, the axis  190  is generally perpendicular to a mask user&#39;s face, although the actual angle will vary with different mask users. The elbow  189  is connected to a pressurized gas hose (not shown) connected, for example, to the blower of conventional CPAP apparatus. The elbow  189  is free to rotate as the mask user changes positions, for example, during sleep. For some applications, it is desirable to route the gas hose to extend over the mask user&#39;s forehead. The gas hose may be connected in a known manner to the headgear which secures the mask to the user. An elbow lock  191  is mounted between the bridge arms  176  and the mask body  168  to pivot on the pins  177 . When the elbow  189  is oriented to be directed towards the mask user&#39;s forehead, the elbow lock  191  may be pivoted to engage a notch  192  on the elbow to lock the position of the elbow  189 . A plurality of notches  192  may be provided to accommodate different locations of the pins  177  for different bridge orientations. 
   It will be appreciated that various modifications and changes may be made to the above described preferred embodiments of a nasal mask without departing from the scope of the following claims.