Abstract:
A method of adjusting the fit of a patient interface device having a nasal cushion rotatably coupled to frame member includes providing resistance to rotation of the nasal cushion assembly in a first direction toward a face of a patient using a rotational resistance mechanism provided between the nasal cushion and the frame member, and responsive to a force being applied to the nasal cushion by a nose of the patient, allowing the nasal cushion to rotate relative to the frame member in the first direction against the resistance to a tilted position, wherein in the tilted position the rotational resistance mechanism biases the cushion assembly in favor of rotation in a second direction opposite the first direction.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This patent application claims the priority benefit under 35 U.S.C. §119(e) of U.S. Provisional Application No. 61/537,737 filed on Sep. 22, 2011, the contents of which are herein incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to patient interface devices for communicating a flow of gas with an airway of a user, and, in particular, to a patient interface device including a nasal cushion structured to tilt to automatically to adjust to different patient facial geometries. 
         [0004]    2. Description of the Related Art 
         [0005]    There are numerous situations where it is necessary or desirable to deliver a flow of breathing gas non-invasively to the airway of a patient, i.e., without intubating the patient or surgically inserting a tracheal tube in their esophagus. For example, it is known to ventilate a patient using a technique known as non-invasive ventilation. It is also known to deliver continuous positive airway pressure (CPAP) or variable airway pressure, which varies with the patient&#39;s respiratory cycle, to treat a medical disorder, such as sleep apnea syndrome, in particular, obstructive sleep apnea (OSA), or congestive heart failure. 
         [0006]    Non-invasive ventilation and pressure support therapies involve the placement of a patient interface device including a mask component on the face of a patient. The mask component may be, without limitation, a nasal mask that covers the patient&#39;s nose, a nasal cushion having nasal prongs that are received within the patient&#39;s nares, a nasal/oral mask that covers the nose and mouth, or a full face mask that covers the patient&#39;s face. The patient interface device interfaces the ventilator or pressure support device with the airway of the patient, so that a flow of breathing gas can be delivered from the pressure/flow generating device to the airway of the patient. It is known to maintain such devices on the face of a wearer by a headgear having one or more straps adapted to fit over/around the patient&#39;s head. 
         [0007]    For such patient interface devices, a key engineering challenge is to balance patient comfort against mask stability and mask to face seal. This is particularly true in the case of treatment of OSA, where such patient interface devices are typically worn for an extended period of time. As a patient changes sleeping positions through the course of the night, masks tend to become dislodged, and the seal can be broken. A dislodged mask can be stabilized by increasing strapping force, but increased strapping force tends to reduce patient comfort. This design conflict is further complicated by the widely varying facial geometries that a given mask design needs to accommodate. One area where facial geometries vary a great deal is the angle of the base of the nose (known as the nasolabial angle). Because this angle varies so greatly, the optimum cushion tilt varies from patient to patient. As a result, the ability to accommodate a wide range of patient nose geometries is important in terms of seal and comfort of a nasal cushion type patient interface device. 
         [0008]    One way to account for such different nose geometries is to include a manual tilt adjustment mechanism in the patient interface device wherein the angle of tilt of the mask component can be adjusted manually to different positions. A manual adjustment method, however, has the potential to cause confusion for the patient, which can lead to frustration and possibly reduce the effectiveness of the patient interface device. 
       SUMMARY OF THE INVENTION 
       [0009]    Accordingly, it is an object of the present invention to provide a patient interface device that overcomes the shortcomings of conventional patient interface devices. This object is achieved according to one embodiment of the present invention by providing a system that includes a patient interface device having a mechanism to allow the cushion assembly of the device to be automatically tilted to accommodate different patient nose geometries. 
         [0010]    In one embodiment, a patient interface device is provided that includes a cushion assembly including a nasal cushion, a first post member extending from a first side of the cushion assembly and a second post member extending from a second side of the cushion assembly, and a frame member having a first arm and a second arm, wherein the first post member is rotatably coupled to the first arm and the second post member is rotatably coupled to the second arm such that the cushion assembly is rotatable with respect to the frame member about an axis extending through the first post member and the second post member. The patient interface device also includes a rotational resistance mechanism coupled to the cushion assembly and the frame member, the rotational resistance mechanism providing resistance to rotation of the cushion assembly in a first direction toward a face of a patient when the patient interface device is donned by the patient and tending to bias rotation of the cushion assembly in a second direction opposite the first direction responsive to the cushion assembly being rotated in the first direction. 
         [0011]    In another embodiment, a patient interface device is provided that includes a nasal cushion, a frame member having a central portion positioned below the nasal cushion, a first arm extending from a first side of the central portion and a second arm extending from a second side of the central portion, and one or more spring members coupled to and extending from a surface of the nasal cushion. A distal end of each of the one or more spring members is coupled to the central portion of the frame member, the one or more spring members providing resistance to rotation of the nasal cushion in a first direction toward a face of a patient when the patient interface device is donned by the patient and tending to bias rotation of the cushion assembly in a second direction opposite the first direction responsive to the cushion assembly being rotated in the first direction. 
         [0012]    In still another embodiment, a method of adjusting a fit of a patient interface device having a nasal cushion rotatably coupled to frame member is provided that includes providing resistance to rotation of the nasal cushion assembly in a first direction toward a face of a patient using a rotational resistance mechanism provided between the nasal cushion and the frame member, and responsive to a force being applied to the nasal cushion by a nose of the patient, allowing the nasal cushion to rotate relative to the frame member in the first direction against the resistance to a tilted position, wherein in the tilted position the rotational resistance mechanism biases the cushion assembly in favor of rotation in a second direction opposite the first direction. 
         [0013]    These and other objects, features, and characteristics of the present invention, as well as the methods of operation and functions of the related elements of structure and the combination of parts and economies of manufacture, will become more apparent upon consideration of the following description and the appended claims with reference to the accompanying drawings, all of which form a part of this specification, wherein like reference numerals designate corresponding parts in the various figures. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended as a definition of the limits of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIGS. 1 and 2  are schematic diagrams of a patient interface device adapted to provide a regimen of respiratory therapy to a patient according to one exemplary embodiment of the present invention; 
           [0015]      FIG. 3  is a schematic diagram of a patient interface device adapted to provide a regimen of respiratory therapy to a patient according to another exemplary embodiment of the present invention; 
           [0016]      FIGS. 4A and 4B  are cross-sectional views of the patient interface device of  FIG. 3  illustrating the operation thereof; 
           [0017]      FIG. 5  is a schematic diagram of a patient interface device adapted to provide a regimen of respiratory therapy to a patient according to another alternative exemplary embodiment of the present invention; 
           [0018]      FIGS. 6A ,  6 B and  6 C are cross-sectional views of the patient interface device of  FIG. 5  illustrating the operation thereof; 
           [0019]      FIG. 7  is a schematic diagram of a patient interface device adapted to provide a regimen of respiratory therapy to a patient according to a further alternative exemplary embodiment of the present invention; 
           [0020]      FIGS. 8A ,  8 B and  8 C are cross-sectional views of the patient interface device of  FIG. 7  illustrating the operation thereof; 
           [0021]      FIG. 9  is a schematic diagram of a patient interface device adapted to provide a regimen of respiratory therapy to a patient according to still a further alternative exemplary embodiment of the present invention; 
           [0022]      FIGS. 10A and 10B  are cross-sectional views of the patient interface device of  FIG. 9  illustrating the operation thereof; 
           [0023]      FIG. 11  is a schematic diagram of a patient interface device adapted to provide a regimen of respiratory therapy to a patient according to yet another alternative exemplary embodiment of the present invention; and 
           [0024]      FIGS. 12A and 12B  are cross-sectional views of the patient interface device of  FIG. 11  illustrating the operation thereof. 
       
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0025]    As used herein, the singular form of “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise. As used herein, the statement that two or more parts or components are “coupled” shall mean that the parts are joined or operate together either directly or indirectly, i.e., through one or more intermediate parts or components, so long as a link occurs. As used herein, “directly coupled” means that two elements are directly in contact with each other. As used herein, “fixedly coupled” or “fixed” means that two components are coupled so as to move as one while maintaining a constant orientation relative to each other. 
         [0026]    As used herein, the word “unitary” means a component is created as a single piece or unit. That is, a component that includes pieces that are created separately and then coupled together as a unit is not a “unitary” component or body. As employed herein, the statement that two or more parts or components “engage” one another shall mean that the parts exert a force against one another either directly or through one or more intermediate parts or components. As employed herein, the term “number” shall mean one or an integer greater than one (i.e., a plurality). 
         [0027]    Directional phrases used herein, such as, for example and without limitation, top, bottom, left, right, upper, lower, front, back, and derivatives thereof, relate to the orientation of the elements shown in the drawings and are not limiting upon the claims unless expressly recited therein. 
         [0028]    A system  2  adapted to provide a regimen of respiratory therapy to a patient according to one exemplary embodiment is generally shown in  FIGS. 1 and 2 . System  2  includes a pressure generating device  4 , a delivery conduit  6 , and a patient interface device  8  having a fluid coupling conduit  10  (patient interface device  8  is shown in isometric view in  FIG. 1  and in front elevational view in  FIG. 2 ). Pressure generating device  4  is structured to generate a flow of breathing gas and may include, without limitation, ventilators, constant pressure support devices (such as a continuous positive airway pressure device, or CPAP device), variable pressure devices (e.g., BiPAP®, Bi-Flex®, or C-Flex™ devices manufactured and distributed by Philips Respironics of Murrysville, Pa.), and auto-titration pressure support devices. Delivery conduit  6  is structured to communicate the flow of breathing gas from pressure generating device  4  to patient interface device  8  through fluid coupling conduit  10 , which in the illustrated embodiment is an elbow connector. Delivery conduit  6  and patient interface device  8  are often collectively referred to as a patient circuit. 
         [0029]    As seen in  FIGS. 1 and 2 , patient interface device  8  includes a patient sealing assembly  12  that facilitates the delivery of the flow of breathing gas to the airway of a patient. Patient sealing assembly  12  includes a frame member  14  having a cushion assembly  16  rotatably coupled thereto in the manner described in greater detail below. 
         [0030]    In the illustrated embodiment, frame member  14  is made of a rigid or semi-rigid material, such as, without limitation, an injection molded thermoplastic or silicone. Frame member  14  includes a generally flat central portion  18  positioned beneath cushion assembly  16 . Frame member  14  further includes arms  20 A and  20 B positioned on opposite sides of central portion  18 . More specifically, arms  20 A and  20 B each include a respective mounting portions  22 A,  22 B extending in a direction that is substantially normal to the top surface of central portion  18  on either side thereof, and extension portions  24 A,  24 B which extend form the distal end of mounting portions  22 A,  22 B. Each mounting portion  22 A,  22 B includes a pivot opening  23 A,  23 B extending therethough. The purpose of the pivot openings  23 A,  23 B is described elsewhere herein. In addition, each extension portion  24 A,  24 B includes a looped connector  26 A,  26 B structured to enable a headgear strap (not shown) to be attached to frame ember  14  in a known manner. 
         [0031]    Cushion assembly  16  includes a nasal cushion  28  structurally and fluidly coupled to a sub-frame member  30 . In the illustrated embodiment, nasal cushion  28  is a “pillows” style nasal cushion made of flexible, cushiony, elastomeric material, such as, without limitation, silicone, an appropriately soft thermoplastic elastomer, a closed cell foam, or any combination of such materials. As seen in  FIGS. 1 and 2 , the exemplary pillows style nasal cushion  28  includes a main body portion  32  having nasal prongs  34 A and  34 B extending from a top side thereof. Alternatively, nasal cushion  28  may be a “cradle” style nasal cushion that rests beneath and covers the patient&#39;s nares, or some other suitable nasal cushion configuration structured to engage the nose of the patient. 
         [0032]    In addition, sub-frame member  30  is made of a rigid or semi-rigid material, such as, without limitation, an injection molded thermoplastic or silicone. Sub-frame member  30  includes a central support portion  36  having a central opening  38 . As seen in  FIGS. 1 and 2 , fluid coupling conduit  10  is coupled to a front side of central support portion  36  through opening  38 . As also seen in  FIGS. 1 and 2 , main body portion  32  of nasal cushion  28  is sealingly coupled to a rear side of central support portion  36  such that fluid coupling conduit is in fluid communication with the interior of nasal cushion  28  through opening  38 . This configuration allows the flow of breathing gas from pressure generating device  4  to be communicated to nasal cushion  28 , and then to the airway of a patient (through the patient&#39;s nares which are engaged by nasal prongs  34 A,  34 B). 
         [0033]    Sub-frame member  30  further includes pivot mounting portions  40 A,  40 B extending from opposite sides thereof. Each pivot mounting portion  40 A,  40 B includes a post member  42 A,  42 B. 
         [0034]    As seen in  FIGS. 1 and 2 , cushion assembly  16  is rotatably mounted to frame member  14  by inserting post members  42 A,  42 B through respective pivot openings  23 A,  23 B. When post members  42 A,  42 B are received in pivot openings  23 A,  23 B in this manner, cushion assembly  16  is able to rotate relative to frame member  14  about an axis through mounting portions  22 A,  22 B in a plane that is generally parallel to the extension portions  24 A,  24 B (i.e., toward and away from the patient&#39;s face as shown by the arrows in  FIG. 1 ). 
         [0035]    In addition, as seen in  FIGS. 1 and 2 , coiled spring members  44 A and  44 B are provided in between sub-frame member  30  and arms  20 A and  20 B on either side of sub-frame member  30 . In particular, each spring member  44 A,  44 B includes a first terminal end  46 A,  46 B that is coupled to a respective pivot mounting portion  40 A,  40 B, and a second terminal end  48 A,  48 B that is coupled to a respective arm  20 A,  20 B. In this manner, coiled spring members  44 A and  44 B provide rotational resistance to cushion assembly  16  relative to frame member  14 . More particularly, cushion assembly  16  will have a preset original base position wherein coiled spring members  44 A and  44 B are in a relaxed state (with no force being applied to cushion assembly  16 ). When a force is applied to nasal prongs  34 A,  34 B by the nose of the patient as a result of patient interface device  8  being donned by the patient, that force will work against the rotational resistance provided by spring members  44 A,  44 B and cause cushion assembly  16  to automatically rotate (tilt) relative to frame member  14  (about the axis described above) to a tilted/loaded position that will accommodate the particular nose geometry of the patient. When that force is removed, the bias of the spring members  44 A,  44 B will cause the cushion assembly  16  to automatically return to the original base position (unloaded). As a result, patient interface device  8  is able to automatically adjust to accommodate different patient facial geometries. 
         [0036]    A system  50  adapted to provide a regimen of respiratory therapy to a patient according to an alternative exemplary embodiment is generally shown in  FIG. 3 . System  50  includes a number of the same components as system  2 , and like components are labeled with like reference numerals. 
         [0037]    System  50  includes an alternative patient interface device  52  that is similar to patient interface device  8  (i.e., it includes fluid coupling conduit  10  and an automatically tilting cushion assembly/frame member combination). Patient interface device  52 , however, includes an alternative patient sealing assembly  54  having an alternative cushion assembly  56  rotatably coupled to an alternative frame member  58  in the manner described in greater detail below.  FIGS. 4A and 4B  are cross-sectional views of a portion of alternative patient interface device  52  showing the operation of patient interface device  52  (described below). 
         [0038]    As seen in  FIG. 3 , frame member  58  includes a number of the same parts as frame member  14 . The central portion  18  of frame member  58 , however, includes slots  60 A,  60 B formed therein, the function of which is described below. 
         [0039]    Cushion assembly  56  includes a nasal cushion  62  structurally and fluidly coupled to a sub-frame member  64 . In the illustrated embodiment, nasal cushion  62  is a “pillows” style nasal cushion made of flexible, cushiony, elastomeric material, such as, without limitation, silicone, an appropriately soft thermoplastic elastomer, a closed cell foam, or any combination of such materials. Alternatively, nasal cushion  62  may be a “cradle” style nasal cushion, or some other suitable nasal cushion configuration structured to engage the nose of the patient. As seen in  FIGS. 3 ,  4 A and  4 B, the exemplary pillows style nasal cushion  62  includes a main body portion  66  having nasal prongs  68 A and  68 B extending from a top side thereof. In addition, nasal cushion  64  includes T-shaped elastomeric tensioner members  70 A and  70 B extending from a bottom side of main body portion  66 . In the exemplary embodiment, elastomeric tensioner members  70 A and  70 B are integrally molded as part of nasal cushion  62 , and may be made of the same material as main body portion  66  or a different material than main body portion  66 . 
         [0040]    In addition, sub-frame member  64 , like sub-frame member  30  of  FIGS. 1 and 2 , is made of a rigid or semi-rigid material, such as, without limitation, an injection molded thermoplastic or silicone. Sub-frame member  64  includes a central support portion  72  having a central opening  74 . As seen in  FIGS. 3-4B , fluid coupling conduit  10  is coupled to a front side of central support portion  72  through opening  74 . As also seen in  FIGS. 3-4B , main body portion  66  of nasal cushion  62  is sealingly coupled to a rear side of central support portion  72  such that fluid coupling conduit  10  is in fluid communication with the interior of nasal cushion  62  through opening  74 . This configuration allows the flow of breathing gas from pressure generating device  4  to be communicated to nasal cushion  62 , and then to the airway of a patient (through the patient&#39;s nares which are engaged by nasal prongs  68 A,  68 B). 
         [0041]    In addition, central support portion  72  of sub-frame member  64  further includes a stop member  76  extending downwardly therefrom. The purpose of stop member  76  is described below. Sub-frame member  64  also includes pivot mounting portions  78 A,  78 B extending from opposite sides thereof. Each pivot mounting portion  78 A,  78 B includes a post member  80 A,  80 B. 
         [0042]    As seen in  FIG. 3 , cushion assembly  56  is rotatably mounted to frame member  58  by inserting post members  80 A,  80 B through respective pivot openings  23 A,  23 B. When post members  80 A,  80 B are received in pivot openings  23 A,  23 B in this manner, cushion assembly  56  is able to rotate relative to frame member  58  about an axis through mounting portions  22 A,  22 B in a plane that is generally parallel to the extension portions  24 A,  24 B (i.e., toward and away from the patient&#39;s face as shown by the arrows in  FIG. 3 ). 
         [0043]    In addition, elastomeric tensioner members  70 A and  70 B are each received within a respective slot  60 A,  60 B of central portion  18  of frame member  58 . In this manner, elastomeric tensioner members  70 A and  70 B provide rotational resistance to cushion assembly  56  relative to frame member  58 . More particularly, cushion assembly  56  will have a preset original base position wherein elastomeric tensioner members  70 A and  70 B are in an un-stretched, relaxed state (with no force being applied to cushion assembly) as seen in  FIG. 4A . In this state, stop member  76  will engage a top surface of central portion  18 . When a force is applied to nasal prongs  68 A,  68 B by the nose of the patient as a result of patient interface device  52  being donned by the patient, that force will work against the rotational resistance provided by elastomeric tensioner members  70 A and  70 B, causing them to stretch as shown in  FIG. 4B , and will cause cushion assembly  56  to automatically rotate (tilt) relative to frame member  58  (about the axis described above) to a tilted/loaded position that will accommodate the particular nose geometry of the patient. When that force is removed, the bias of the elastomeric tensioner members  70 A and  70 B (wherein they will want to un-stretch), will cause the cushion assembly  56  to automatically return to the original base position (unloaded). Again, in this state, stop member  76  will engage the top surface of central portion  18  to prevent over rotation. 
         [0044]    A system  100  adapted to provide a regimen of respiratory therapy to a patient according to another alternative exemplary embodiment is generally shown in  FIG. 5 . System  100  includes a number of the same components as system  2 , and like components are labeled with like reference numerals. 
         [0045]    System  100  includes an alternative patient interface device  102  that is similar to patient interface device  8  (i.e., it includes fluid coupling conduit  10  (shown in partial cut-away form) and an automatically tilting cushion assembly/frame member combination). Patient interface device  102 , however, includes an alternative patient sealing assembly  104  having an alternative cushion assembly  106  rotatably coupled to frame member  14  as described in connection with  FIG. 1  in the manner described in greater detail below.  FIGS. 6A ,  6 B and  6 C are cross-sectional views of a portion of alternative patient interface device  102  showing the operation of patient interface device  102  (described below). 
         [0046]    Cushion assembly  106  includes a nasal cushion  112  structurally and fluidly coupled to a sub-frame member  114 . In the illustrated embodiment, nasal cushion  112  is a “pillows” style nasal cushion made of flexible, cushiony, elastomeric material, such as, without limitation, silicone, an appropriately soft thermoplastic elastomer, a closed cell foam, or any combination of such materials. Alternatively, nasal cushion  112  may be a “cradle” style nasal cushion, or some other suitable nasal cushion configuration structured to engage the nose of the patient. As seen in  FIGS. 5-6C , the exemplary pillows style nasal cushion  112  includes a main body portion  116  having nasal prongs  118 A and  118 B extending from a top side thereof. In addition, nasal cushion  112  includes post members  120 A and  120 B extending from opposite sides of main body portion  116 . In the exemplary embodiment, post members  120 A and  120 B are integrally molded as part of nasal cushion  112 , and may be made of the same material as main body portion  116  or a different material than main body portion  116 . 
         [0047]    In addition, sub-frame member  114 , like sub-frame member  30  of  FIGS. 1 and 2 , is made of a rigid or semi-rigid material, such as, without limitation, an injection molded thermoplastic or silicone. Sub-frame member  114  includes a central support portion  122  having a central opening  124 . As seen in  FIGS. 5-6C , fluid coupling conduit  10  is coupled to a front side of central support portion  122  through opening  124 . As also seen in  FIGS. 5-6C , main body portion  116  of nasal cushion  112  is sealingly coupled to a rear side of central support portion  122  such that fluid coupling conduit  10  is in fluid communication with the interior of nasal cushion  112  through opening  124 . This configuration allows the flow of breathing gas from pressure generating device  4  to be communicated to nasal cushion  112 , and then to the airway of a patient (through the patient&#39;s nares which are engaged by nasal prongs  118 A,  118 B). 
         [0048]    Moreover, in this embodiment, a plurality of coiled (metal, e.g., steel) spring members  126  are provided in between the bottom surface of nasal cushion  112  and the top surface of central portion  18  of frame member  14 . In the illustrated exemplary embodiment, front spring members  126 A and  126 B and rear spring member  126 C and  126 D are provided. Also, as seen in  FIG. 5 , cushion assembly  106  is rotatably mounted to frame member  14  by inserting post members  120 A,  120 B through respective pivot openings  23 A,  23 B. When post members  120 A,  120 B are received in pivot openings  23 A,  23 B in this manner, cushion assembly  106  is able to rotate relative to frame member  14  about an axis through mounting portions  22 A,  22 B in a plane that is generally parallel to the extension portions  24 A,  24 B (i.e., toward and away from the patient&#39;s face as shown by the arrows in  FIG. 5 ). 
         [0049]    In addition, spring members  126  provide rotational resistance to cushion assembly  116  relative to frame member  14 . More particularly, cushion assembly  116  will have a preset original base position shown in  FIGS. 5 and 6A  (with no force being applied to cushion assembly  116 ). When a force is applied to nasal prongs  118 A,  118 B by the nose of the patient as a result of patient interface device  102  being donned by the patient, that force will work against the rotational resistance provided spring members  126 , causing front spring members  126 A,  126 B to stretch and rear spring member  126 C,  126 D to compress and bend as shown in  FIG. 6B , and will cause cushion assembly  106  to automatically rotate (tilt) relative to frame member  14  (about the axis described above) to a tilted/loaded position that will accommodate the particular nose geometry of the patient. When that force is removed, the bias of spring members  126  will cause the cushion assembly  106  to automatically tilt in the reverse direction (as shown in  FIG. 6C ) and ultimately return to the original base position of  FIG. 6A . 
         [0050]    In an alternative embodiment, sub-frame member  114  may further include a stop member extending downwardly therefrom to restrict the reverse rotation of cushion assembly  116 . In another alternative embodiment, post members  120 A,  120 B may be omitted and instead sub-frame member  114  may include pivot mounting portions having post members (like pivot mounting portions  78 A,  78 B having post member  80 A,  80 B) extending from opposite sides thereof. 
         [0051]    A system  100 ′ adapted to provide a regimen of respiratory therapy to a patient according to a further alternative exemplary embodiment is generally shown in  FIGS. 10-13 . System  100 ′ is similar to system  100 , and includes a number of the same components as system  100 , and like components are labeled with like reference numerals. However, as seen in  FIGS. 7-8C , cushion assembly  106 ′, unlike cushion assembly  106 , does not include post members  120 A,  120 B, and cushion assembly  106 ′ is thus not pivotably mounted to arms  20 A,  20 B of frame member  14 . Instead, in this embodiment, cushion assembly  106 ′ is structured to float in between mounting portions  22 A,  22 B on spring members  126 . 
         [0052]    A system  150  adapted to provide a regimen of respiratory therapy to a patient according to still another alternative exemplary embodiment is generally shown in  FIG. 9 . System  150  includes a number of the same components as system  2 , and like components are labeled with like reference numerals. 
         [0053]    System  150  includes another alternative patient interface device  152  that is similar to patient interface device  8  (i.e., it includes fluid coupling conduit  10  and an automatically tilting cushion assembly/frame member combination). Patient interface device  152 , however, includes another alternative patient sealing assembly  154  having an alternative cushion assembly  156  rotatably coupled to an alternative frame member  158  in the manner described in greater detail below.  FIGS. 10A and 10B  are cross-sectional views of a portion of alternative patient interface device  152  showing the operation of patient interface device  152  (described below). 
         [0054]    As seen in  FIG. 9 , frame member  158  includes a number of the same parts as frame member  14 . The central portion  18  of frame member  158 , however, includes an upwardly extending stop portion  160 , the function of which is described below. 
         [0055]    Cushion assembly  156  includes a nasal cushion  162  structurally and fluidly coupled to a sub-frame member  164 . In the illustrated embodiment, nasal cushion  162  is a “pillows” style nasal cushion made of flexible, cushiony, elastomeric material as described elsewhere herein. Alternatively, nasal cushion  162  may be a “cradle” style nasal cushion, or some other suitable nasal cushion configuration structured to engage the nose of the patient. As seen in  FIGS. 9-10B , the exemplary pillows style nasal cushion  162  includes a main body portion  166  having nasal prongs  168 A and  168 B extending from a top side thereof. 
         [0056]    In addition, sub-frame member  164 , like sub-frame member  30  of  FIGS. 1 and 2 , is made of a rigid or semi-rigid material, such as, without limitation, an injection molded thermoplastic or silicone. Sub-frame member  164  includes a central support portion  172  having a central opening  174 . As seen in  FIGS. 9-10B , fluid coupling conduit  10  is coupled to a front side of central support portion  172  through opening  174 . As also seen in  FIGS. 9-10B , main body portion  166  of nasal cushion  162  is sealingly coupled to a rear side of central support portion  172  such that fluid coupling conduit  10  is in fluid communication with the interior of nasal cushion  162  through opening  174 . This configuration allows the flow of breathing gas from pressure generating device  4  to be communicated to nasal cushion  162 , and then to the airway of a patient (through the patient&#39;s nares which are engaged by nasal prongs  168 A,  168 B). 
         [0057]    Sub-frame member  164  also includes pivot mounting portions  178 A,  178 B extending from opposite sides thereof. Each pivot mounting portion  178 A,  178 B includes a post member  180 A,  180 B. 
         [0058]    Moreover, in this embodiment, a number of coiled (metal, e.g., steel) spring members  182  ( 182 A and  182 B in the illustrated embodiment) are provided in between the bottom surface of nasal cushion  162  at the rear end thereof and the top surface of central portion  18  of frame member  158 . Also, as seen in  FIG. 9 , cushion assembly  156  is rotatably mounted to frame member  158  by inserting post members  180 A,  180 B through respective pivot openings  23 A,  23 B. When post members  180 A,  180 B are received in pivot openings  23 A,  23 B in this manner, cushion assembly  156  is able to rotate relative to frame member  158  about an axis through mounting portions  22 A,  22 B in a plane that is generally parallel to the extension portions  24 A,  24 B (i.e., toward and away from the patient&#39;s face as shown by the arrows in  FIG. 14 ). 
         [0059]    In addition, spring member(s)  182  provide rotational resistance to cushion assembly  156  relative to frame member  158 . More particularly, cushion assembly  156  will have a preset original base position wherein spring member(s)  182  are in an un-compressed, relaxed state (with no force being applied to cushion assembly) as seen in  FIG. 10A . In this state, the front end of the bottom surface of nasal cushion  162  will engage the top edge of stop portion  160 . When a force is applied to nasal prongs  168 A,  168 B by the nose of the patient as a result of patient interface device  152  being donned by the patient, that force will work against the rotational resistance provided by spring member(s)  182 , causing them to compress and bend as shown in  FIG. 10B , and will cause cushion assembly  156  to automatically rotate (tilt) relative to frame member  158  (about the axis described above) to a tilted/loaded position that will accommodate the particular nose geometry of the patient. As seen in  FIG. 10B , in this state, the front end of the bottom surface of nasal cushion  162  will lift off and be spaced from the top edge of stop portion  160 . When that force is removed, the spring member(s)  182  will decompress and unbend and cause the cushion assembly  156  to automatically return to the original base position (unloaded). Again, in this state, the front end of the bottom surface of nasal cushion  162  will engage the top edge of stop portion  160  and prevent over rotation of cushion assembly  156 . 
         [0060]    A system  200  adapted to provide a regimen of respiratory therapy to a patient according to an additional alternative exemplary embodiment is generally shown in  FIGS. 11 ,  12 A and  12 B. System  200  is similar to system  100 ′ (like components are labeled with like reference numerals) in that the patient interface device  202  thereof has a cushion assembly  206  that does not include post members (like post members  120 A,  120 B), and cushion assembly  206  is thus not pivotably mounted to arms  20 A,  20 B of frame member  14 . Instead, in this embodiment, cushion assembly  206  is supported on central portion  18  of frame member  14  and is structured to float in between mounting portions  22 A,  22 B. More specifically, cushion assembly  206  includes nasal cushion  212  having a main body portion  216  having nasal prongs  218 A and  218 B extending from a top side thereof. Cushion assembly  206  also includes a sub-frame  214 . In addition, nasal cushion  212  includes a bellows section  219  on a rear side thereof extending from a top surface of main body portion  216  to a bottom surface of main body portion  216 . 
         [0061]    In operation, when patient interface device  202  is in use, the inside of nasal cushion  212  is under pressure and that pressure will tend to cause nasal cushion  212  to have an original base expanded state as shown in  FIG. 12A . When a force is applied to nasal prongs  218 A,  218 B by the nose of the patient as a result of patient interface device  202  being donned by the patient, that force will work against the internal pressure just described, causing bellows section  219  to compress as shown in  FIG. 12B . As a result, the tilt angle of nasal prongs  218 A,  218 B will automatically adjust to accommodate the particular nose geometry of the patient. When that force is removed, bellows section  219  will decompress and cause cushion assembly  206  to automatically return to the original expanded base position. In the exemplary embodiment, bellows section  219  has a cross-sectional thickness that is less than the cross-sectional thickness of the remainder of nasal cushion  212  to enable bellows section  219  to more easily collapse under the force provided by the nose of the patient as described above. 
         [0062]    In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word “comprising” or “including” does not exclude the presence of elements or steps other than those listed in a claim. In a device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The word “a” or “an” preceding an element does not exclude the presence of a plurality of such elements. In any device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain elements are recited in mutually different dependent claims does not indicate that these elements cannot be used in combination. 
         [0063]    Although the invention has been described in detail for the purpose of illustration based on what is currently considered to be the most practical and preferred embodiments, it is to be understood that such detail is solely for that purpose and that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover modifications and equivalent arrangements that are within the spirit and scope of the appended claims. For example, it is to be understood that the present invention contemplates that, to the extent possible, one or more features of any embodiment can be combined with one or more features of any other embodiment.