Abstract:
A mask with cushion that has an outer film is disclosed. The film may be self-skinning or a film formed about or glued to the cushion body. In another form the cushion may be formed with at least a portion having a plurality of adjacent voids having a honeycomb-like structure.

Description:
FIELD OF INVENTION 
     This invention relates to patient interfaces particularly though not solely for use in delivering CPAP therapy to patients suffering from obstructive sleep apnoea (OSA). In particular, this invention relates to cushions used to support and seal the mask to a patient&#39;s face. 
     BACKGROUND OF THE INVENTION 
     In the art of respiration devices, there are well known variety of respiratory masks which cover the nose and/or mouth of a human patient in order to provide a continuous seal around the nasal and/or oral areas of the face such that gas may be provided at positive pressure within the mask for consumption by the patient. The uses for such masks range from high altitude breathing (i.e., aviation applications) to mining and fire fighting applications, to various medical diagnostic and therapeutic applications. 
     One requisite of such respiratory masks has been that they provide an effective seal against the patient&#39;s face to prevent leakage of the gas being supplied. Commonly, in prior mask configurations, a good mask-to-face seal has been attained in many instances only with considerable discomfort for the patient. This problem is most crucial in those applications, especially medical applications, which require the patient to wear such a mask continuously for hours or perhaps even days. In such situations, the patient will not tolerate the mask for long durations and optimum therapeutic or diagnostic objectives thus will not be achieved, or will be achieved with great difficulty and considerable patient discomfort. 
     U.S. Pat. No. 5,243,971 and U.S. Pat. No. 6,112,746 are examples of prior art attempts to improve the mask system U.S. Pat. No. 5,570,689 and PCT publication No. WO 00/78384 are examples of attempts to improve the forehead rest. 
     U.S. Pat. No. 6,634,358 and U.S. Pat. No. 6,581,602 of ResMed Limited disclose a nasal mask cushion to sealingly connect a mask to a wearer&#39;s face. The cushion has a nose-receiving cavity bounded by a frame and membrane. The membrane is spaced away from the rim of the frame, and its outer surface is of substantially the same shape as the rim. 
     In the prior art mask cushions are provided that have a solid inner wall that provides support but doesn&#39;t allow much change in the shape of the cushion. Thus, such mask cushions can be uncomfortable for a user. Furthermore, often prior art mask cushions are made of foam which is neither waterproof nor durable. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to attempt to provide a patient interface which overcomes the abovementioned disadvantages in the prior art or which will at least provide the industry with a useful choice. 
     Accordingly, in a first aspect the present invention consists in a cushion for a patient interface adapted to supply gas to a patient comprising: 
     a cushion body; and 
     an outer cover, 
     wherein said body and cover are substantially formed of the same elemental material. 
     Preferably said elemental material is polyurethane. 
     Preferably said cushion body is formed in polyurethane foam. 
     Preferably said outer cover is formed in polyurethane film. 
     Preferably said outer cover is adhered to said body. 
     Preferably said cushion body is assembled from more than one moulded component. 
     Preferably said cushion body includes an attachment adapted to engage a mask. 
     In a second aspect the present invention consists in a cushion for a patient interface adapted to supply gas to a patient comprising: 
     a cushion body having an outer cover, and 
     an outer sealing sheath, 
     wherein said cushion body is detachable from said outer sheath and said patient interface. 
     Preferably said cushion body and said outer sealing sheath are formed of the same elemental material. 
     Preferably said elemental material is silicone. 
     In a third aspect the present invention consists in a mask adapted to deliver gas to a patient comprising: 
     a cushion body wherein at least a portion thereof has a plurality of adjacent voids. 
     Preferably each of said voids has a hexagonal cross section. 
     Preferably each of said voids has an oval, square, rectangular, or other shaped cross section. 
     Preferably said cushion body has an outer cover and said mask further includes an outer sealing sheath. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Preferred forms of the present invention will now be described with reference to the accompanying drawings. 
         FIG. 1  is a block diagram of a humidified continuous positive airway pressure system as might be used in conjunction with the present invention. 
         FIG. 2  is an illustration of a nasal mask in use with a cushion according to the preferred embodiment of the present invention. 
         FIG. 3  shows a perspective view of the mask with cushion. 
         FIG. 4  is a cutaway view of the mask showing the cushion. 
         FIG. 5  shows a cross section of second preferred embodiment of the mask cushion. 
         FIG. 6  shows perspective view of an inner cushion of the second preferred embodiment of the mask cushion. 
         FIG. 7  shows a cross section of an inner cushion with a reinforcement film or coating. 
         FIG. 8  shows a cross section of an inner cushion made up of two portions welded or glued in the middle. 
         FIG. 9  shows a cross section of an inner cushion with a connecting catch between the halved portions of the cushion. 
         FIG. 10  shows a cross section of a halved foam cushion with mounting brackets. 
         FIG. 11  shows a plan view of a mask cushion having a honeycomb-like structure. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention provides improvements in the delivery of CPAP therapy. In particular a patient interface and cushion is described which is quieter for the patient to wear and reduces leakage from the mask, therefore providing for a good seal on a wearer&#39;s nose and face. Furthermore, the patient interface and cushion of the present invention provides for conformity to a patient&#39;s facial contours unlike other solid silicone mask or cushion designs and is comfortable for a patient to wear. Also, the cushion of the present invention is durable and allows the pressure of the face of a user to be reduced preventing face sores and the like. 
     It will be appreciated that the patient interface as described in the preferred embodiment of the present invention can be used in respiratory care generally or with a ventilator but will now be described below with reference to use in a humidified CPAP system. It will also be appreciated that the present invention can be applied to any form of patient interface including, but not limited to, nasal masks, oral masks and mouthpieces. 
     With reference to  FIG. 1  a humidified Continuous Positive Airway Pressure (CPAP) system is shown in which a patient  1  is receiving humidified and pressurised gases through a patient interface  2  connected to a humidified gases transportation pathway or inspiratory conduit  3 . It should be understood that delivery systems could also be VPAP (Variable Positive Airway Pressure) and BiPAP (Bi-level Positive Airway Pressure) or numerous other forms of respiratory therapy. Inspiratory conduit  3  is connected to the outlet  4  of a humidification chamber  5  which contains a volume of water  6 . Inspiratory conduit  3  may contain heating means or heater wires (not shown) which heat the walls of the conduit to reduce condensation of humidified gases within the conduit. Humidification chamber  6  is preferably formed from a plastics material and may have a highly heat conductive base (for example an aluminium base) which is in direct contact with a heater plate  7  of humidifier  8 . Humidifier  8  is provided with control means or electronic controller  9  which may comprise a microprocessor based controller executing computer software commands stored in associated memory. 
     Controller  9  receives input from sources such as patient input means or dial  10  through which a patient of the device may, for example, set a predetermined required value (preset value) of humidity or temperature of the gases supplied to patient  1 . The controller may also receive input from other sources, for example temperature and/or flow velocity sensors  11  and  12  through connector  13  and heater plate temperature sensor  14 . In response to the patient set humidity or temperature value input via dial  10  and the other inputs, controller  9  determines when (or to what level) to energise heater plate  7  to heat the water  6  within humidification chamber  5 . As the volume of water  6  within humidification chamber  5  is heated, water vapour begins to fill the volume of the chamber above the water&#39;s surface. The water vapour is then passed out of the humidification chamber  5  outlet  4  with the flow of gases (for example air) provided from a gases supply means or blower  15  which enters the chamber through inlet  16 . Exhaled gases from the patient&#39;s mouth are passed directly to ambient surroundings in  FIG. 1 . 
     Blower  15  is provided with variable pressure regulating means or variable speed fan  21  which draws air or other gases through blower inlet  17 . The speed of variable speed fan  21  is controlled by electronic controller  18  (or alternatively the function of controller  18  could be carried out by controller  9 ) in response to inputs from controller  9  and a patient set predetermined required value (preset value) of pressure or fan speed via dial  19 . 
     Nasal Mask 
     According to a first embodiment of the present invention the patient interface is shown in  FIG. 2  as a nasal mask. The mask includes a hollow body  100  with an inlet  101  connected to the inspiratory conduit  3 . The mask  2  is positioned around the nose of the patient  1  with the headgear  103  secured around the back of the head of the patient  1 . The headgear  103  preferably attaches to a gliding strap or straps  117  by way of connectors  118 . The gliding straps  117  allow for the patient to move his head but the mask  2  and more particularly the cushion  104  is not pulled from the patient&#39;s face. The restraining force from the headgear  103  on the hollow body  100  and the forehead rest  105  ensures enough compressive force on the mask cushion  104 , to provide an effective seal against the patient&#39;s face. 
     The hollow body  100  is constructed of a relatively inflexible material for example, polycarbonate plastic. Such a material would provide the requisite rigidity as well as being transparent and a relatively good insulator. The expiratory gases can be expelled through a valve (not shown) in the mask, a further expiratory conduit (not shown), or any other such method as is known in the art. 
     Mask Cushion 
     Referring now to  FIGS. 3 and 4  in particular, the mask cushion  104  is shown in further detail. The cushion  104  is provided around the periphery of the nasal mask hollow body  100  to provide an effective seal onto the face of the patient to prevent leakage. The mask cushion  104  is shaped to approximately follow the contours of a patient&#39;s face. The mask cushion  104  will deform when pressure is applied by the headgear ( 108 , see  FIG. 2 ) to adapt to the individual contours of any particular patient. In particular, there is an indented section  106  that fits over the bridge of the patient&#39;s nose as well as a less indented section  107  to seal around the section beneath the nose and above the upper lip. 
     As shown in  FIG. 4  the mask cushion  104  is composed of an inner cushion  108  covered by an outer sealing sheath  109 . The inner cushion  108  is constructed of a resilient material for example, polyurethane foam, to enable distribution of pressure evenly along the seal around the patient&#39;s face. The inner cushion  108  is located around the outer periphery  110  of the open face  111  of the hollow body  100 . Similarly the outer sheath  109  may be commonly attached at its base  112  to the periphery  110  and loosely covers over the top of the inner cushion  108 . 
     In a first embodiment of the mask cushion shown in  FIG. 4  the bottom of the inner cushion  108  fits into a generally triangular cavity  113  in the hollow body  100 . The cavity  113  is formed from a flange  114  running mid-way around the interior of the hollow body  100 . The outer sheath  109  fits in place over the cushion  108 , holding it in place. The sheath  109  is secured by a snap-fit to the periphery  110  of the hollow body. The periphery  110  of the hollow body is shown including an outer bead  115 . The sheath  109  includes a matching bead  116 , whereby once it is stretched around the periphery  110 , the two beads  115 ,  116  engage to hold the sheath  109  in place. 
     Referring now to  FIGS. 5 and 6 , a second embodiment of the mask cushion of the present invention is depicted. In this second embodiment, the inner cushion  200  includes a raised bridge  201  in the nasal bridge region. Thus the notch in the contacting portion is less pronounced than proceeding embodiments, however as the raised bridge  201  is unsupported it is much more flexible and results in less pressure on the nasal bridge of the patient. The outer sheath  202  contacts the cushion  200  throughout the raised bridge  201 . 
     Referring particularly to  FIG. 6 , the foam cushion  200  includes a check contour  203 , which follows the cartilage extending from the middle of the nose, and a contoured lip sealing portion  204 , to seal between the base of the nose and the upper lip. 
     Honeycomb Cushion 
     Referring to  FIG. 11 , a third embodiment of the mask cushion of the present invention is illustrated. The inner cushion  400  may be formed in a honeycomb structure  401 . The cushion  400  is shown in  FIG. 11  with a partial area of an array of hexagonal areas or voids  401 . It must be noted that select parts of the cushion could be made in the honeycomb structure, while other areas are fully formed from foam, gel, silicon, rubber or the like material. In yet other forms, the whole cushion may be formed in this type of honeycomb-like structure. 
     This type of honeycomb-like structure of the cushion  400  reduces the pressure on the patient&#39;s nasal bridge region in use, meaning this cushion  400  is more comfortable to use. 
     The hexagonal cushion  400  is preferably formed in a silicon or rubber material and as such is likely to be more flexible, durable and hygienic. The cushion  400  is preferably formed by injection moulding in silicone. Therefore, a mould for use to mould the cushion will have hexagonal or other appropriately shaped uprights that form the voids in the cushion. 
     The hexagonal cushion  400  may also be coated with an outer film or coating (not shown) by similar methods as are described below. In particular, the outer coating may be formed from silicone. 
     Film or Coating 
     A reinforcement film or coating (outer cover) can be applied onto any of the above described inner cushion&#39;s outer surfaces to reduce the possibility of tearing of the inner cushion. Such a reinforcement film would likely be made of a resilient material for example polyurethane. The coating may be applied onto the cushions surface using a variety of methods, for example, injection of a foam cushion onto the pre-made film that lines the cushion mould or adhering a pre-made cushion with a plastic film using processes such as high frequency welding, ultrasonic welding, or gluing. The film or coating could be a plastic film, for example a durable polyurethane film, or a sprayed or painted on plastic or paint coating. Alternatively, the inner cushion may be dipped in a plastic or paint to coat it. 
     It is preferred that the mask cushion in this form be comprised of an inner cushion with an outer cover and an outer sealing sheath. Preferably the inner cushion and outer cover are formed of the same elemental material, for example, polyurethane foam and film, respectively. The outer sealing sheath is preferably made of a flexible material, such as silicone or rubber. In other forms the inner cushion may be made of a gel, silicone, or rubber like material. In this form the inner cushion is not attached to the mask but floats between the outer sealing sheath and mask body. This enables the inner cushion, whether made from a foam or gel, silicone or rubber-like material and can be removed, enabling easy cleaning or the use of different sized inner cushions with the mask for better custom fitting for the user. 
     Referring to  FIG. 7 , a cushion  300  with a reinforcement film  301  is illustrated as a whole cushion body  302 . The cushion body  302  includes an upper outer periphery portion  303  and lower hollow fitting portion  304 . The outer periphery portion  303  rests against the patient&#39;s face in use and the hollow fitting portion  304  attaches to the mask hollow body, for example,  100  in  FIG. 4  in a manner as described above. 
     Referring to  FIG. 7 , the reinforcement film or coating  301  for example, a plastic film, can be applied to the outer periphery portion  303  and hollow fitting portion  304  separately, usually by injection moulding each portion, although other suitable methods such as painting or spraying may be used. Later the two portions may be joined together to form the whole cushion  300 . These two portions  303 ,  304  can be joined using different methods; one example is by high frequency welding where high or ultrasonic frequencies cause the cushion material, for example, foam (in the preferred embodiment), to meld together. The advantage of moulding two portions and joining them to make up the cushion is that the cushion is easier to manufacture. 
     As an example, the two portions  303 ,  304  of the cushion  300  may be formed by injecting foam into female moulds, then removing these and covering them with a plastic coating then using high or ultrasonic welding to meld the two portions plastic coatings together. 
     In other forms the cushion  300  may be welded on to the mask hollow body  100 . In this form the cushion would be permanently attached to the mask body  100  (see  FIG. 4 ). Here, it is likely that the mask body  100  is made from an injection moulding grade thermoplastic. A film  301  can be applied on to the pre-made portions  303 ,  304  or whole cushion  300  itself. For example, the reinforcement film or coating may be applied on to the pre-made cushion  300  by means of spraying (using an air-gun or the like), dipping or painting (of the mould before injecting of the cushion). Again, the cushion could be made in a single mould or in portions as described above. 
     In another form the film may be made of durable polyurethane and be vacuum formed onto a female mould, the mould may be a single cavity or multi-cavity to enable multiple forming of upper and lower portions of the cushion. The material making up the cushion, may then be injected into the cavity onto the film. The cushion and film are then left to cure at a temperature between 40° C. and 50° C. for 5 to 8 minutes. During this time the material making up the cushion (preferably foam) adheres to the film. The end result is a cushion covered with a plastic coating that will be resistant to wear, tear and moisture. 
       FIG. 8 , shows a cross section of a cushion  500  made up of two portions  501 ,  502  that are each covered in a coating or film  503  (similar to those described above) that have been welded together where the portions  501 ,  502  meet. 
     Referring to  FIG. 9 , the halved portions  601 ,  602  of a cushion  600  may be formed with a catch or key  604 . The two parts of the catch  604  are keyed together to assist in the alignment of the portions  601 ,  602  and then the portions are welded together. Each of the portions  601 ,  602  is shown in  FIG. 9  as being covered by a coating or film  603 . The catch of key  604  has the purpose of assisting to align the two portions and to prevent movement of the two portions during welding. 
     Referring to  FIG. 10 , a cushion  700  may be attached to the mask body with a mounting bracket  701  that clips to a groove (not shown) in the hollow mask body. The cushion  703 , for example, moulded of foam, is preferably directly molded on the bracket  701 . The reinforcement film or coating  702  is then adhered to the cushion&#39;s surface using the methods described above, an adhesive material or high frequency or ultrasonic welding. 
     In alternative forms of the cushion the cushion could be moulded onto the film and then welded to the bracket. The bracket is preferably made from a polyurethane or thermoplastic and has the purpose of enabling the clipping of the cushion to the mask body. 
     A mask cushion with a film coating will mean that while the cushion remains flexible and soft, it is more durable. Furthermore, the cushion will be waterproof, as moisture from the patient&#39;s skin or caused by surrounding apparatus or therapy the patient is undergoing, is not absorbed by the cushion. Therefore, the cushion will also be more hygienic.