Abstract:
A nasal CPAP treatment apparatus is disclosed with a flow generator coupled to a nasal mask. The mask has a nasal cushion forming a nose-receiving cavity. The cushion has a triangularly-shaped frame of resilient material with a mask engaging portion connected by a side wall to a face engaging portion which has a nasal bridge region, a cheek region and a lip region. The cushion may have a portion of the side wall in the nasal bridge region being other than straight to provide an improved sealing in the nasal bridge region. A plurality of membranes, preferably three, of resilient material extend substantially around the triangularly-shaped frame. Some of the membranes are thicker in the lip region than in the nasal bridge region to improve fit of the cushion in use.

Description:
RELATED APPLICATIONS  
       [0001]    This application, pursuant to 37 C.F.R. §1.78( c ), claims priority based on provisional application serial No. 60/291,902 filed May 18, 2001 and provisional application serial No. 60/314,141 filed Aug. 22, 2001. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates to an improved cushion that contacts a portion of a patient&#39;s face to provide a comfortable interface and improved seal between an external device, such as a respiratory mask, and the patient.  
         DESCRIPTION OF RELATED ART  
         [0003]    A variety of respiratory masks are known having a flexible seal that covers the area surrounding the nose and/or mouth of a human user and that are designed to create a continuous seal against the user&#39;s face.  
           [0004]    Because of the sealing effect created, gases can be provided at a positive pressure within the mask for consumption by the user. The uses of such masks include, but are not limited to high altitude breathing (aviation applications), swimming, mining and fire fighting applications along with various medical diagnostic and therapeutic applications.  
           [0005]    One requisite of many of these masks, particularly medical respiratory masks, is that they provide an effective seal against the user&#39;s face to prevent leakage of the gas being supplied. Commonly, in conventional mask configurations, the mask-to-face seal has been attained in many instances only with considerable discomfort for the user. This problem is most crucial in those applications, especially medical applications, which require the user to wear the mask continuously for hours or perhaps even days. In such situations, the user will not tolerate an uncomfortable mask for long durations and optimum therapeutic or diagnostic objectives will not be achieved if imperfect seals are formed, or will be achieved with great difficulty and considerable user discomfort.  
         BACKGROUND OF THE INVENTION  
         [0006]    Nasal masks are commonly used in the treatment of respiratory conditions and sleep disorders (e.g., obstructive sleep apnea) by delivering a flow of breathable gas for, or to assist patient respiration. These nasal masks typically receive a gas supply line which delivers gas into a chamber formed by walls of the mask and the user&#39;s face. The walls usually are semi-rigid and have a face contacting portion including an aperture which is aligned with the wearer&#39;s nostrils. The face contacting portion can comprise a soft, resilient elastometric material which may conform to varius facial contours. The mask normally is secured to the wearer&#39;s head by straps. The straps are adjusted to pull the mask against the face with sufficient force to achieve a gas tight seal between the mask and the wearer&#39;s face but not so tight as to be uncomfortable. Gas is thus delivered to the mask and into the wearer&#39;s nasal passages.  
           [0007]    Problems often arise with masks of the above configuration. For example, the mask may be dislodged, thereby breaking the seal between the mask and wearer. This may occur if the wearer rolls over when sleeping thereby creating a drag force on the gas supply line which is transmitted to the mask, breaking the seal. In the case of a mask being used for the administration of Continuous Positive Airway Pressure (CPAP) treatment for the condition obstructive sleep apnea, such a leak can result in the pressure supplied to the entrance of the wearer&#39;s airway being below the therapeutic value, and the treatment becoming ineffective.  
           [0008]    Another problem is the face contacting portion may apply excessive pressure to the wearer&#39;s face resulting in discomfort and possibly skin irritation. This can occur because the face contacting portion has to distort beyond its normal range of elasticity to conform to certain facial contours which requires the application of excessive forces. In some cases these excessive pressures and forces may cause the face to distort to conform with the face contacting portion to increase wearer discomfort, resulting in facial soreness and ulceration.  
           [0009]    An example of the respiratory mask useful in the CPAP treatment is in U.S. Pat. No. 6,112,746 issued to Kwok et al. Sep. 5, 2000, the entire disclosure of which is incorporated by reference. That patent lists over 200 pieces of prior art generally pertinent to the subject invention. The present invention relates to a cushion for a respiratory mask which is more comfortable and provides a superior seal than heretofore available.  
           [0010]    These and other advantages will be described in more detail below.  
         SUMMARY OF THE INVENTION  
         [0011]    Accordingly, it is an object of the present invention to provide an improved cushion effecting an superior seal for confronting engagement with the surface of the users face to form a sealed interface therewith that overcomes the shortcomings of conventional seal techniques. This object is achieved, according to one embodiment of the present invention, by providing a cushion in which three membranes are used to provide superior sealing characteristics while minimizing the head strap tension and therefore the compressive forces exerted by the mask against the user&#39;s face.  
           [0012]    Another object of the present invention is to provide a respiratory mask with an improved cushion wherein the cushion is provided with membranes having variable thicknesses between the nasal bridge region and the region that fits between the nares and the upper lip to provide superior sealing characteristics.  
           [0013]    Yet another object of the invention is to provide a mask cushion having a side wall that is other than straight, such as curved or sinuous, which makes the cushion nose compressible to better fit around the user&#39;s face. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    For the purpose of facilitating an understanding of the invention, there is illustrated in the accompanying drawings a preferred embodiment thereof, from an inspection of which, when considered in connection with the following description, the invention, its construction and operation, and many of its advantages should be readily understood and appreciated.  
         [0015]    [0015]FIG. 1 is a side elevational view of a respiratory mask in accordance with the present invention placed against the face of the user;  
         [0016]    [0016]FIG. 2 is a front elevational view of the face side of the respiratory mask including the improved cushion of the present invention;  
         [0017]    [0017]FIG. 3 is a perspective view of an embodiment of the improved cushion;  
         [0018]    [0018]FIG. 4 is a perspective view of a cushion embodying the present invention;  
         [0019]    [0019]FIG. 5 is a view like FIG. 4 rotated with respect to FIG. 4;  
         [0020]    [0020]FIG. 6 is a cross-sectional view of one embodiment of the present invention as viewed along line A-A of FIG. 4;  
         [0021]    [0021]FIG. 7 is a cross-sectional view of one embodiment of the present invention as seen along line B-B of FIG. 4;  
         [0022]    [0022]FIG. 8 is a cross-sectional view of another embodiment of the present invention as seen along line A-A of FIG. 4;  
         [0023]    [0023]FIG. 9 is a cross-sectional view of the embodiment of FIG. 8 as seen along line B-B of FIG. 4;  
         [0024]    [0024]FIGS. 10A and 10B are views partly in section of an embodiment of the invention with an improved side wall; and  
         [0025]    [0025]FIG. 11 is an elevational view partly in section of the embodiment of FIGS. 10A and 10B. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0026]    Referring now to the drawings and particularly FIGS. 1 and 2, there is shown a respiratory mask  10  which includes a rigid shell or cone  15  having a body portion  16 . The body portion  16  in plan view is triangular in shape in order to fit the contours of a person&#39;s face above the nose to between the nose and the lips. The body portion has a rim  17  with outwardly extending tabs  18  for use with head straps to hold the mask to the users face which are not shown. The cone  15  has an end  20  defining a circular opening  21  to which is coupled a conduit  22  shown by broken line which connects a coupling  23  to the cone  15  and a gas source and flow generator  24 . Upwardly extending from the cone  15  is a tab or frame member  25  having parallel vertically disposed slots  26  to accommodate portions of the head straps (not shown but well known in the art) which are used to affix the respiratory mask  10  to the user  36 .  
         [0027]    Referring now to FIGS.  3 - 8 , there is shown a cushion  30  including the inventive seals or membranes for use in the respiratory mask  10  of the present invention. The cushion  30  includes an outer surface  31  having a frame engaging portion  32  around the bottom periphery thereof and a face engaging portion  33 . The cushion  30  defines a chamber  35  between the user  36  and the cone  15 .  
         [0028]    The cushion  30  further includes a nasal bridge region  38  positioned in use above the user&#39;s nose at the bridge portion thereof and a lip region  39  generally positioned in use between the nares of the nose and the lips. A cheek region  40  separates the nasal bridge region  38  and the lip region  39 . The frame engaging portion  32  is relatively thick compared to the rest of the cushion  30  and defines a channel  41  in the frame engaging portion  32 , the cushion  30  having a bottom surface  42  extending around the channel  41  being defined by an inner lip portion  43  and the side wall  45  extending upwardly from the bottom surface  32  of the cushion. The channel  41  is sized to fit around the rim  17  of the rigid shell or cone  15  in order to securely mount the cushion  30  to the cone or shell  15 .  
         [0029]    Referring to FIGS.  6 - 7 , there is shown a first embodiment of the present invention in which the side wall  45   a  near the lip region  39  of the cushion  30  is shorter than the side wall  45   b  near the nasal bridge region  38  of the cushion  30  to provide a better fitting cushion. Near the lip region  39  of the cushion  30  there are three membranes integral with the side wall  45  and extending therefrom, the membranes being denoted as  46   a ,  47   a  and  48   a . The membrane  46   a  is the thickest of the three membranes at the lip region  39  of the cushion  30 . The membrane  47   a  is thinner than the membrane  46   a  at the lip region  39  and thicker than the outermost membrane  48   a . The membranes  46 ,  47 , and  48  all have flexibility and deform when a force is applied against the cushion  30  when the cushion is in place against the users face  36 , as seen in FIG. 1. The use of three or more membranes is an improvement over the use of two membranes commonly used and seems to provide significant advances in comfort for the user. In the embodiment of FIGS. 6 and 7, the thicknesses of the membranes  46 ,  47  and  48  change between the lip region  39  of the cushion  30  and the nasal bridge region  38  of the cushion  30 . The membranes  46   b ,  47 , and  48   b  at the nasal bridge region  38  of the cushion  30  are all about the same thickness and all, preferably are as thin as the membrane  48   a  at the lip region  39  of the cushion  30 . At the lip region  39  the membranes have different thicknesses with, for instance membrane  46   a  being 0.06 inches thick, the membrane  47   a  being about 0.03 inches thick and membrane  48   a  being about 0.02 inches thick. The change in thickness of the membrane between the lip region  39  and the nasal bridge region  38  occurs in the cheek region  40 . The advantages of the embodiment illustrated in FIGS. 6 and 7 as well as hereinafter is the use of the triple membrane system in combination with the varying thickness in the membrane in order to provide not only a soft feeling cushion but also an improved seal. As seen in FIG. 4, the area labeled “c” corresponds to the cheek region  40  and is the area where the membranes  46  and  47  are reduced in thickness until they all become the same thickness at the nasal bridge region  38  of the cushion  30 . The area denoted in FIG. 4 as area “d” is the nasal bridge region  38  of the cushion  30  and it is in that region that the outer membrane  48   b  comes in contact with the bridge of the users nose and where for instance, the thickness of all membranes may be 0.02 inches.  
         [0030]    As seen from FIG. 6, the thickness of the side wall  45   a  just above the channel  41  may be just slightly thicker than the thickness of the inner membrane  46   a . Thereafter, the thickness of the side wall  45  diminishes from the inner membrane  46  to the outer membrane  48 . Finally, the side wall  45  becomes the outer membrane  48 . Also, the side wall  45   a  may be thicker at the lip region  39  than at  45   b  in the nasal bridge region  38 . The variable thicknesses in the membranes  46 ,  47  and  48  are a significant feature of the invention and provide a significant improvement in the comfort of cushion  30 , in use.  
         [0031]    Preferably, the cushion  30  is a single piece of molded plastic and may be removably or fixedly secured to the cone or shell  15  as by sonic welding, adhesives or any other suitable means. Silicon plastics are well known in the art.  
         [0032]    Referring to FIGS. 8 and 9, there is shown another embodiment of the present invention in which cushion  130  is illustrated. Like numerals have been applied to like pieces with the exception that the embodiment of FIGS. 8 and 9 is identified with the corresponding number in the 100s. For instance, the outer surface of the cushion  130  is  131  as distinguished from the outer surface of the cushion  30  which is  31 . The cushion  130  also has three membranes, the inner membrane  146 , the middle membrane  147  and the outer membrane  148 . The principal difference between the embodiments of FIGS. 6 and 7 and the embodiments of FIGS. 8 and 9 lies in the fact that the inner membrane  146  and the middle membrane  147  join to form a rib  149  connecting the membranes  146  and  147  to the side  145 . Another difference in the embodiment of FIGS. 6 and 7 and the embodiment of FIGS. 8 and 9 is that the membranes  146 ,  147  and  148  do not change the thickness from the lip region  139  to the nasal bridge region  138 .  
         [0033]    Referring now to FIGS. 10A and 10B and  11 , there is disclosed a third embodiment of the present invention which is similar to the embodiment disclosed in FIGS. 6 and 7 except that the side wall  150  has a portion  151  which is other than straight. In the embodiment illustrated in FIGS. 10A and 10B and  11 , the portion  151  which is other than straight includes two arcuate portions  152  and  153  which are joined to each other to form a sinuous portion  151 . Although a sinuous portion  151  is shown in FIGS. 10A and 10B and  11 , other designs are intended to be incorporated herein and covered by the claims and include, by way of example only, simple arcuate portions, curved portions, V-shaped portions, box or rectangular shaped cross-sections or any other than straight cross-section which provides a more compressible function to the side wall  150 . The other than straight portion  151  of the side wall  150  is a significant improvement in the present invention in that the portion  151  is more compressible and provides a far improved sealing mechanism to the nasal bridge region of the cushion  30 A. The remaining portions of the cushion  30 A other than the side wall portion  151  is the same as shown in the embodiments illustrated in FIGS. 6 and 7. However, preferably the side wall portion  45 A in FIG. 6 is extended somewhat as shown in FIGS. 10A and 10B and  11  and provides an improved angle of contact when the cushion  30 A is worn by a user; and in the preferred embodiment is 1.95 inches in the lip region and 2.15 inches in the nasal bridge region.  
         [0034]    As illustrated in the drawings of FIGS. 10A and 10B and  11 , the other than straight portion  151  extends in a horse shoe configuration around the nasal bridge region of the cushion  30 A and extends approximately ⅔ of the way along the side wall  150  from the nasal bridge region into the cheek region and toward the lip region of the cushion  30 A. Although as illustrated in FIGS. 10A and 10B and  11 , the other than straight portion  151  does not completely encircle the cushion  30 A, there is no particular reason that it may not. Accordingly, it is intended to cover within the invention herein disclosed, an other than straight portion  151  which extends entirely around the cushion  30 A as well as the embodiment illustrated in which the other than straight portion  151  eventually blends into the straight side wall portion near the lip region.  
         [0035]    [0035]FIGS. 10A and 10B contains many actual measurements from one preferred embodiment of the present invention, but are included only for purposes of illustration and not by way of limitation.  
         [0036]    While there has been disclosed what is considered to be the preferred embodiment of the present invention, it is understood that various changes in the details may be made without departing from the spirit, or sacrificing any of the advantages of the present invention.