Abstract:
A improved nasal mask is disclosed for delivering CPAP therapy to patients. The nasal mask has a sliding engagement to the headgear. The sliding engagement allows substantial relative lateral movement eg: when face is distorted from sleeping on side, while still providing adequate compressive force to avoid side leakage. The sliding engagement also allows easy release from the headgear.

Description:
FIELD OF INVENTION  
         [0001]    This invention relates to nasal masks particularly though not solely for use in providing CPAP therapy to patients suffering from obstructive sleep apnoea (OSA).  
         BACKGROUND OF THE INVENTION  
         [0002]    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.  
           [0003]    One requisite of such respiratory masks 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.  
           [0004]    In common with prior art designs, is an inability to seal effectively when the user&#39;s face becomes distorted. For example, as shown in the prior art mask of FIG. 1 when the user  300  is sleeping on his or her side, one side  302  of the headgear tends to be pulled tight while the other side  304  tends to be loose. This causes the axis of the mask  306  to be twisted with respect to the axis of the head  308 —due to the net torque from the headgear—resulting in leakage  310  on one side. The user  300  sleeping on his or her side may also distort the facial contours around the nasal area  312  and may lead to further leakage.  
         SUMMARY OF INVENTION  
         [0005]    It is an object of the present invention 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.  
           [0006]    Accordingly in one aspect the invention consists in a device for delivering a supply of gases to a user comprising:  
           [0007]    a patient interface, in use in fluid communication with said supply of gases,  
           [0008]    securement means attached to or around the head of said user, and  
           [0009]    engaging means adapted to slidingly engage said securement means with said patient interface.  
           [0010]    In a second aspect the present invention consists in nasal mask for delivering gases to a user comprising:  
           [0011]    a body portion having a inlet, in use said inlet receiving a supply of gases,  
           [0012]    sealing means engaged with said body portion, and adapted to seal against the facial contours of said user, and  
           [0013]    engaging means adapted to in use provide a sliding engagement with a means of securement to a user, and a compressive force on said sealing means to ensure said supply of gases is delivered to a user without significant leakage.  
           [0014]    In a third 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 nasal mask in fluid communication with said transport means in use delivering said gases to said user, said nasal mask comprising  
           [0015]    a body portion having a inlet, in use said inlet receiving a supply of gases,  
           [0016]    sealing means engaged with said body portion, and adapted to seal against the facial contours of said user, and  
           [0017]    engaging means adapted to in use provide a sliding engagement with a means of securement to a user, and a compressive force on said sealing means to ensure said supply of gases is delivered to a user without significant leakage.  
           [0018]    This invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, and any or all combinations of any two or more of said parts, elements or features, and where specific integers are mentioned herein which have known equivalents in the art to which this invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth.  
           [0019]    The invention consists in the foregoing and also envisages constructions of which the following gives examples. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]    One preferred form of the present invention will now be described with reference to the accompanying drawings in which;  
         [0021]    [0021]FIG. 1 is a plan view of a prior art mask illustrating side leak,  
         [0022]    [0022]FIG. 2 is a plan view of a mask according to the preferred embodiment of the present invention,  
         [0023]    [0023]FIG. 3 is a block diagram of a humidified continuous positive airway pressure (CPAP system) as might be used in conjunction with the present invention,  
         [0024]    [0024]FIG. 4 is an illustration of the nasal mask in use according to the preferred embodiment of the present invention,  
         [0025]    [0025]FIG. 5 is a front view of the nasal mask illustrating the headgear securement to the mask,  
         [0026]    [0026]FIG. 6 is a perspective view of the mask showing multiple engaging clips,  
         [0027]    [0027]FIG. 7 is a perspective view of the mask showing the sliding strap clipped in place, and  
         [0028]    [0028]FIG. 8 is a side view of the sliding strap. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0029]    The present invention provides improvements in the field of nasal masks for use in CPAP therapy. In particular a nasal mask is described which is more comfortable for the user to wear and reduces the side leakage as compared with masks of the prior art. 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.  
         [0030]    With reference to FIG. 3 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  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.  
         [0031]    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. 3.  
         [0032]    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 .  
       Nasal Mask  
       [0033]    Referring to FIG. 4 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  1  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.  
         [0034]    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 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 Headgear  
       [0035]    Referring now to FIGS. 4 and 5 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 .  
         [0036]    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.  
         [0037]    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.  
         [0038]    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. 4 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.  
         [0039]    In a further embodiment shown in FIGS. 6, 7 and  8  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. 8 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, and therefore slides with respect to the hollow body  102  with very little resistance.  
         [0040]    As shown in FIG. 6, 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. 6 that a number of clips are so provided, in order to allow pressure from different angles for different face shapes.  
         [0041]    As shown in FIG. 8 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.  
         [0042]    It will be appreciated that in all embodiments of the present invention the attachment from the headgear to the mask is designed to slide with as less friction as possible while still ensuring adequate direct force on the mask cushion to the user&#39;s face. As shown in FIG. 2 the sliding connection  320  allows the headgear  322 , 324  to provide even force on both sides of the mask  326 . This avoids placing a torque on the mask and twisting of the mask which minimises mask leaks from the seal to the face  328 .