Abstract:
A CPAP system is described for improved respiratory therapy of patients. In particular a patient interface is disclosed with an outlet vent with lower noise levels and more diffused outlet flow over prior art outlet vents. The outlet vent includes a main vent which is diffused and muffled and a higher resistance vent provided in case the main vent is blocked. The outlet vent is removable for easy maintenance and provides indication to the user when maintenance is required. The outlet vent described may be used on nasal masks, mouthpieces and patient interfaces generally.

Description:
[0001]    This application is a continuation application of Ser. No. 09/881,394, filed on Jun. 14, 2001 (now allowed), and entitled “Nasal Mask”. 
     
    
     
       FIELD OF INVENTION  
         [0002]    This invention relates to patient interfaces particularly though not solely to nasal mask for use in providing CPAP therapy to patients suffering from obstructive sleep apnea (OSA).  
         BACKGROUND OF THE INVENTION  
         [0003]    In the art of respiration devices, there are well known a variety of respiratory masks which cover the nose and/or mouth of a human user 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 user. 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.  
           [0004]    One requisite of such respiratory devices has been that they provide an effective seal against the user&#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 user. This problem is most crucial in those applications, especially medical applications, which require the user to wear such a mask continuously for hours or perhaps even days. In such situations, the user 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 user discomfort.  
           [0005]    Where such masks as those used above are used in respiratory therapy, in particular treatment of obstructive sleep apnea (OSA) using Continuous Positive Airway Pressure (CPAP) therapy, there is generally provided in the art a vent for washout of the bias flow or expired gases to the atmosphere. Such a vent may be provided for example, as part of the mask, or in the case of some respirators where a further conduit carries the expiratory gases, at the respirator. The washout of gas from the mask is essential to ensure that carbon dioxide build up does not occur over the range of flow rates. In the typical flow rates in CPAP treatment, usually between  4 cm H 2  O to 20 cm H 2  O, prior art attempts at such vents have resulted in excessive noise causing irritation to the user and concentrated flows of gases irritating any bed partners.  
           [0006]    Various approaches have been developed in the prior art to attempt to reduce the noise when CPAP therapy is provided. For example, in PCT Patent Application No. W 0 98/34665 it has been proposed that the vent include a resilient plug with rounded edges at the apertures to reduce noise. In PCT patent application no WO00178382 a vent is provided with a semi annular flap. However, these prior art methods are not entirely satisfactory in eliminating the extra noise created by a vent at the mask.  
         SUMMARY OF INVENTION  
         [0007]    It is an object of the present invention to attempt to provide a nasal mask which goes some way to overcoming the abovementioned disadvantages in the prior art or which will at least provide the industry with a useful choice.  
           [0008]    Accordingly in a first aspect the invention consists in a device for delivering a supply of gases to a user comprising:  
           [0009]    a patient interface, in use in fluid communication with said supply of gases and supplying said gases to said user, including at least one outlet vent integrated or adjacent therewith and  
           [0010]    a removable diffusing member adapted to in use covering said vent, and diffuse a substantial portion of the expired gases of said user.  
           [0011]    Preferably a device for delivering a supply of gases to a user as claimed in claim 1 wherein said removable member in use diffusing and audibly muffling a substantial portion of the expired gases of said user.  
           [0012]    Preferably a device for delivering a supply of gases to a user as claimed in claim 2 wherein said outlet means including at least one low resistance outlet and at least one high resistance outlet through which the expired gases of said user flow out through.  
           [0013]    Preferably a device for delivering a supply of gases to a user as claimed in claim 3 wherein during normal use the majority of said expired gases passing from said vent and out through said low resistance outlet, whereby if the majority of said expired gases are substantially prevented from passing through said low resistance outlet, the majority of said expiratory gases passing out said high resistance outlet.  
           [0014]    Preferably a device for delivering a supply of gases to a user as claimed in claim 3 or 4 wherein said high resistance outlet is comprised of apertures in said patient interface or said removable member or in the intersection there between.  
           [0015]    Preferably a device for delivering a supply of gases to a user as claimed in claim 3 or 4 wherein said high resistance outlet is adapted such that in use is said low resistance outlet is blocked or has significant increase in resistance, said high resistance outlet vents a sufficient flow gas so as to prevent rebreathing of carbon dioxide by said user.  
           [0016]    Preferably a device for delivering a supply of gases to a user as claimed in claim 3 or 4 wherein said removable member comprises a frame member and a disposable medium in use juxtaposed between said frame member and said vent, said low resistance outlet comprising the flow of said expired gases through said disposable medium.  
           [0017]    Preferably a device for delivering a supply of gases to a user as claimed in claim 7 wherein said disposable medium reducing the external audible noise level and diffusing the flow pattern that would otherwise occur from said gases flowing through said vent.  
           [0018]    Preferably a device for delivering a supply of gases to a user as claimed in claim 7 wherein said disposable medium is a filter material.  
           [0019]    Preferably a device for delivering a supply of gases to a user as claimed in any of claims 1 to 4 wherein said patient interface comprises a nasal mask having a hard body portion, an inlet to said body portion receiving said supply of gases, sealing means engaged with said body portion, and adapted to seal against the facial contours of said user, and means of securement to said user providing a compressive force on said sealing means to ensure said supply of gases is delivered to a user without significant leakage, said vent comprising t least one aperture in said body portion.  
           [0020]    Preferably CPAP system for delivering gases to a user including a pressurised source of gases, transport means in fluid communication with said pressurised source adapted to convey said gases, and a patient interface in fluid communication with said transport means in use delivering said gases to said user, said patient interface including:  
           [0021]    outlet means having at least one outlet vent, and a removable diffusing member covering said vent, said outlet means in use passing a substantial portion of the expired gases of said user.  
           [0022]    Preferably a CPAP system as claimed in claim 11 wherein said patient interface is a nasal mask.  
           [0023]    In a second aspect the present invention consists in a CPAP system for delivering gases to a user including a pressurised source of gases, transport means in fluid communication with said pressurised source adapted to convey said gases, and a patient interface in fluid communication with said transport means in use delivering said gases to said user, said patient interface including:  
           [0024]    outlet means having at least one outlet vent, and a removable diffusing member covering said vent, said outlet means in use passing a substantial portion of the expired gases of said user.  
           [0025]    In a third aspect the present invention consists in a removable diffusing member for a gases delivery patient interface, said removable member adapted to be juxtaposed on or over a vent, associated with a patient interface and pass a substantial portion of expired gases from a user flowing out from a vent.  
           [0026]    Preferably a removable diffusing member as claimed in claim 13 wherein said removable member is adapted to in use diffuse and audibly muffle a substantial portion of the expired gases of a user flowing out from a vent.  
           [0027]    Preferably a removable diffusing member as claimed in claim 13 or 14 comprising a frame member and a disposable medium, said disposable medium adapted to be juxtaposed in use between said frame member and a vent, and in use a low resistance outlet being formed by the flow of expired gases through said disposable medium, said removable diffusing member further comprising a high resistance outlet for the flow of expired gases if said low resistance outlet in use becomes blocked.  
           [0028]    Preferably a removable diffusing member as claimed in claim 15 wherein said disposable medium is a filter material.  
           [0029]    To those skilled in the art to which the invention relates, many changes in construction and widely differing embodiments and applications of the invention will suggest themselves without departing from the scope of the invention as defined in the appended claims. The disclosures and the descriptions herein are purely illustrative and are not intended to be in any sense limiting.  
           [0030]    The invention consists in the foregoing and also envisages constructions of which the following gives examples.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0031]    One preferred form of the present invention will now be described with reference to the accompanying drawings in which;  
         [0032]    [0032]FIG. 1 is a block diagram-of a humidified continuous positive airway pressure (CPAP system) as might be used in conjunction with the present invention,  
         [0033]    [0033]FIG. 2 is an illustration of the nasal mask in use according to the preferred embodiment of the present invention,  
         [0034]    [0034]FIG. 3 is a front view of the nasal mask illustrating the headgear securement to the mask,  
         [0035]    [0035]FIG. 4 is a perspective view of the mask illustrating the plurality of engaging clips to connect to the sliding strap  
         [0036]    [0036]FIG. 5 is a perspective view of the mask showing the sliding strap clipped into the engaging clips,  
         [0037]    [0037]FIG. 6 is a side view showing the sliding strap,  
         [0038]    [0038]FIG. 7 is a perspective view of the mask illustrating the outlet vents,  
         [0039]    [0039]FIG. 8 is a perspective view of the mask illustrating the vent cap in place, and  
         [0040]    [0040]FIG. 9 is a perspective view of the vent cap.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0041]    The present invention provides improvements in the field of CPAP therapy. In particular an outlet is described which is quieter and has a more diffused outlet flow. It will be appreciated that the nasal mask 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 outlet vent described is equally applicable to all forms of patent interface, in particular a mouth piece.  
         [0042]    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 nasal mask  2  (or other types of patient interface as appropriate) 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.  
         [0043]    Controller  9  receives input from sources such as user input means or dial  10  through which a user 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 user 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 and is 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.  
         [0044]    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 carried out by controller  9 ) in response to inputs from controller  9  and a user set predetermined required value (preset value) of pressure or fan speed via dial  19 .  
         [0045]    Nasal Mask  
         [0046]    Referring to FIG. 2 the nasal mask, according to the preferred embodiment of the present invention, is shown in detail. The mask includes a hollow body  102  with an inlet  103  connected to the inspiratory conduit  3 . The mask  2  is positioned around the nose of the user I with the headgear  108  secured around the back of the head of the patient  1 . The restraining force from the headgear  108  on the hollow body  102  and the forehead rest  106  ensures enough compressive force on the mask cushion  104 , to provide an effective seal against the patient&#39;s face.  
         [0047]    The hollow body  102  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 in the preferred embodiment of the present invention are expelled through a valve in the mask  300 , or alternatively a further expiratory conduit (not shown), or any other such method as is known in the art.  
         [0048]    Mask Headgear  
         [0049]    Referring now to FIGS. 2 and 3 the headgear  108  is shown connected to the hollow body  102 . Rather than traditional fixed or adjustable attachments the present invention utilises a sliding engagement between the headgear  108  and the hollow body  102 . This is achieved with a loop  120 , running through harnessing clips  122 ,  124  on either side of the headgear  108  and over the top of the hollow body  102 . The loop  120  is reciprocally engaged with guides  126 ,  128  mounted on the top surface of the hollow body  102 . The guides constrain the loop  120  but allow it to slide in and out, meaning the headgear  108  can move laterally, independently of the hollow body  102 .  
         [0050]    The advantage to this is as the face is contorted during various sleeping positions the headgear is able to move with the changes in position while the mask is left in the correct position on the nose of the user and an effective seal is maintained.  
         [0051]    Additional guides  129 ,  130 ,  131  allow the user to adjust position of loop  120 , giving ability to get different pressure-on the seal depending on loop  120  position.  
         [0052]    To further ensure user comfort and effective pressure on the mask cushion  104 , the headgear  108  may be constructed either using two straps running around the back of the user&#39;s head as shown in FIG. 2 or with a partial skull cap or any other configurations as are known in the art. In this case the straps or partial skull cap would be constructed using neoprene but may also be constructed using any material as is known in the art which will be comfortable for the user.  
         [0053]    In a further embodiment shown in FIGS. 4, 5 and  6  the present invention is illustrated using a sliding strap to attach the headgear  108  to the hollow body  102 . The strap  200 , shown in FIG. 6 in isolation, is constructed of polyacetal (Delrin 500P NC010) using injection moulding techniques to give a polished finish. This material, similar to other nylon based derivatives, with its polished finish has a particularly low friction co-efficient, slides with respect to the hollow body  102  with very little resistance. As shown in FIG. 4, the hollow body  102  includes a number of engaging clips  202 , in use the sliding strap  200  snaps into place into the engaging clips  202  and can only be removed therefrom using a substantial force. This means that with any normal use the sliding strap  200  will stay retained within the engaging clips  202 . It will also be appreciated from FIG. 4 that a number of clips are so provided, in order to allow pressure from different angles for different face shapes.  
         [0054]    As shown in FIG. 6 the sliding strap includes a mid-section  204  intended to reciprocate with the engaging clips  202 , terminated at each end by loops  206 ,  208  which attach to the headgear. The first loop  206  is a full loop through which the headgear  108  is permanently attached with for example, a velcro strap. The loop  208  at the other end, is only a partial loop  210  designed so that a strap or loop from the headgear  108  can be easily slipped in or out of the open section  212  to allow easy removal and attachment of the mask.  
         [0055]    Outlet Vent  
         [0056]    In a further improvement shown in FIGS.  7  to  9  the present invention includes an outlet vent  300  as part of the body portion. The outlet vent  300  includes a number of apertures  302  either moulded in the body portion  102  or drilled through after moulding. The apertures  302  are separated and to some extent surrounded by a number of partitions  304  which provide support for a filter cap which is installed over top of the apertures  302 . The filter cap is designed primarily prevent what would otherwise be the noise generated from the flow of gases through the apertures  302  externally. This filter cap comprises a frame member  306  (shown in FIG. 9) which snaps on over top of the partition  304  and holds in place a piece of filter medium  308  which sits over top of the partitions  304 . The frame  306  includes large vents  307  such that the expiratory or bias flow from the mask flows out the apertures  302  through the filter medium  308  and out the vent  307 . The piece of filter medium  308  is preferably Ecofilt brand filter medium (PM135) which is less prone to blocking from the humidity levels often found in such applications.  
         [0057]    The structure of the outlet vent allows for the filter medium to be replaced as and when necessary in an easy and efficient manner. The frame  306  can be easily removed, the filter medium  308  replaced and the frame  306  snapped on back in place. Further in the rare event of the filter medium blocking, auxiliary vents  310  are provided in the frame  306  which match up with gaps  312  in the partitions  304 . As the auxiliary vents  310  are much smaller than the main vents  307  during normal use very little flow passes through them. If the filter medium  108  becomes blocked the flow is then forced through the auxiliary vents  310 . This will be significantly more noisy than normal and will indicate the need for maintenance to the user.  
         [0058]    It will be appreciated that by providing such a system the present invention effectively minimises the noise generated by the outward flow of expiratory gases from the mask. The present invention is of a low maintenance type and when replacement of the filter medium is required, it is an easy and simply exercise. As well as reducing the noise level the flow through the outlet vent is more diffused. This avoids for example, a flow of gases directed at a sleeping partner or a similar flow directed at the patient, either of which causing restlessness or waking.