Abstract:
A patient interface for delivering pressurised gases to a user comprising a housing configured to receive gases and deliver them to a user and a forehead rest. The forehead rest is engaged with the housing and has a single area of contact with a user&#39;s forehead. The forehead rest includes a bridge portion between the user&#39;s forehead and housing allowing a substantially unrestricted view for a user&#39;s eyes. The forehead rest is pivotally movable in relation to the housing and can be locked by a friction engagement into position.

Description:
FIELD OF INVENTION  
         [0001]    This invention relates to patient interfaces particularly though not solely for use in delivering CPAP therapy to patients suffering from obstructive sleep apnoea (OSA).  
         BACKGROUND OF THE INVENTION  
         [0002]    In the art of respiration devices, a variety of respiratory masks are well known that 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 will not be achieved, or will be achieved with great difficulty and considerable user discomfort.  
           [0004]    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, PCT publication No. WO 00/78384 and U.S. Pat. No. 6,119,693 are examples of attempts to improve a forehead rest attached to the mask.  
         SUMMARY OF THE INVENTION  
         [0005]    It is an object of the present invention to attempt to provide a patient interface 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]    In a first aspect the present invention consist in an interface for delivering pressurised gases to a user comprising:  
           [0007]    a housing configured to receive gases and deliver them to a user,  
           [0008]    a forehead rest engaged with said housing and having a single area of contact with a user&#39;s forehead and including a bridge member between a users forehead and said housing allowing a substantially unrestricted view for a users eyes.  
           [0009]    Preferably said bridge member is adjustable or configurable in orientation with respect to said housing.  
           [0010]    Preferably said bridge member includes a pivoting engagement to said housing.  
           [0011]    Preferably said bridge member has a substantially parallel side.  
           [0012]    Preferably said forehead rest including attachment points for headgear, said attachment points lying in an approximately mid sagittal plane.  
           [0013]    Preferably said interface is a mask.  
           [0014]    Preferably said mask is a nasal mask.  
           [0015]    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. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    Preferred forms of the present invention will now be described with reference to the accompanying drawings.  
         [0017]    [0017]FIG. 1 is a block diagram of a humidified continuous positive airway pressure (system) as might be used in conjunction with the present invention  
         [0018]    [0018]FIG. 2 is an illustration of the nasal mask in use according to the preferred embodiment of the present invention.  
         [0019]    [0019]FIG. 3 shows a perspective view of the mask with cushion  
         [0020]    [0020]FIG. 4 is a cutaway view of the mask showing the cushion.  
         [0021]    [0021]FIG. 5 is a cutaway view of the periphery of the outer membrane of the mask cushion.  
         [0022]    [0022]FIG. 6 is a cutaway view of the periphery of the mask body portion.  
         [0023]    [0023]FIG. 7 is a perspective view of the narrow forehead rest.  
         [0024]    [0024]FIG. 8 is a front view of the narrow forehead rest of FIG. 7.  
         [0025]    [0025]FIG. 9 shows a prior art forehead rest in isolation.  
         [0026]    [0026]FIG. 10 shows a section view of a forehead rest cushion that maybe used with the mask and forehead rest of the present invention.  
         [0027]    [0027]FIG. 11 is a section of an alternative forehead rest cushion.  
         [0028]    [0028]FIG. 12 is a cross section view of Se friction engagement that is used to fix the forehead rest in position.  
     
    
     DETAILED DESCRIPTION  
       [0029]    The present invention provides improvements in the delivery of CAP therapy. In particular a patient interface is described which is quieter for the user to wear and reduces the side leakage as compared with the prior art. 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 CAP 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.  
         [0030]    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  that 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  that 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 meads 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 . A flow of gases (for example air) is provided to the chamber through inlet  16  from a gases supply means or blower  15 . 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  through outlet  4 . Exhaled gases from the patient&#39;s mouth are passed directly to ambient surrounding in FIG  1 .  
         [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 sped 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 .  
         [0033]    Nasal Mask  
         [0034]    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  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.  
         [0035]    The headgear  108  maybe attached by a clip  122  to sliding straps  120  that allow movement of the headgear  108  but prevent the mask  2  from moving on the patients face.  
         [0036]    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.  
         [0037]    Mask Cushion  
         [0038]    Referring now to FIGS. 3 and 4, the mask cushion  1104  is provided around the periphery of the nasal mask  1102  (having a bridge member attachment  1103 ) to provide an effective seal onto the face of the user to prevent leakage. The mask cushion  1104  is shaped to approximately follow the contours of a patient&#39;s face. The mask cushion  1104  will deform when pressure is applied by the headgear ( 108 , as shown in FIG. 2), to adapt to the individual contours of any particular user. In particular, there is an indented section  1150  intended to fit over the bridge of the user&#39;s nose as well as a less indented section  1152  to seal around the section beneath the nose and above the upper lip.  
         [0039]    In FIG. 4 we see that the mask cushion  1104  is composed of an inner foam cushion  1110  covered by an outer sealing sheath  1112 . The inner cushion  1110  is constructed of a resilient material for example polyurethane foam, to distribute the pressure evenly along the seal around the user&#39;s face. The inner cushion  1110  is located around the outer periphery  1114  of the open face  1116  of the hollow body  1102  Similarly the outer sheath  1112  may be commonly attached at its base  1113  to the periphery  1114  and loosely covers over the top of the inner cushion  1110 .  
         [0040]    In the preferred embodiment shown in FIGS.  3  to  6  the bottom of the inner cushion  1110  fits into a generally triangular cavity  1154  in the hollow body  1102 . The cavity  1154  is formed from a flange  1156  running mid-way around the interior of the hollow body.  
         [0041]    The outer sheath  1112  fits in place over the cushion  1101  holding it in place. The sheath  1112  is secured by a snap-fit to the periphery  1114  of the hollow body. In FIGS. 5 and 6 the periphery  1114  is shown including an outer bead  1158 . The sheath  1112  includes a matching bead  1159 , whereby once stretched around the periphery the two beads engage to hold the sheath in place.  
         [0042]    Prior Art Forehead Rest  
         [0043]    A prior art nasal mask  2102  is shown in FIG. 9. This mask  2102  includes a hinged forehead rest  2106 . The attachment of the forehead rest  2106  to the mask body  2102  effectively allows the forehead rest  2106  to move freely in proximity to the user but with no lateral movement. Pins  2130  are provided mounted on a base  2132  attached to the mask body  2102 . These pins  2130  are co-axial within cylinders  2131  mounted on a bridge member  2136 . The forehead rest  2106  is T-shaped.  
         [0044]    At the top end  2142  (that rests against the user&#39;s forehead) of the bridge member  2136 , harnessing slots  2138  are provided which allow straps from the headgear to be inserted to secure the mask to the headgear. For the uses comfort one or more resilient cushions  2140  are provided underneath the top end  2142  of the bridge member  2136 , which rest on the forehead of the user. The cushion  2140  might be constructed of silicon or any foam materials as is known in the art for providing cushioning.  
         [0045]    The forehead rest  2106  may include a weakened section  2130  at its base  2132  which allows the joining member  2136  to pivot from the mask body  2102 . The bridge member extends up to the forehead of the user. The mask can also include a vertical upwardly extending inlet. In this case the bridge member  2136  is hinged at its base  2132  to either side of the inlet passage, Again the bridge member would then extend to the forehead.  
         [0046]    Narrow Forehead Rest  
         [0047]    In FIGS. 7 and 8, a nasal mask  505  is shown with the forehead support  500  of the present invention. In this embodiment the forehead rest  500  is narrow to minimise the profile and frontal appearance of the mask  505 .  
         [0048]    The forehead rest  500  is comprised of a bridge member  532  that is narrow with parallel sides. The bridge member  532  has an adjustment knob  550  placed on the opposite side of a friction member  520 . When the adjustment knob  550  is a loosened the position of the bridge member  530  can be adjusted to any desired angle relative to the mask body  510 , in a similar to the prior art mask of FIG. 9. The bridge member  532  may also be fixed in place or include a malleable inset to allow the bridge member  532  to flex. A single cushion  560  is attached to the apex  546  of the bridge member  532 . Headgear (not shown) attaches through slots  540 ,  542  which extend away from the forehead in an approximately mid sagittal plane.  
         [0049]    The forehead rest is most preferably made from a thermoplastic polycarbonate or similar and manufactured by injection moulded. The advantage is that the forehead sport is small and streamlined as the headgear attachment points are placed above the main forehead support structure, rather than extending out the side, which is the traditional approach as shown in FIG. 9. A mask is smaller and therefore is less intrusive than prior art masks with T-shaped forehead rests.  
         [0050]    The adjustment knob  550  in a loosened position the bridge member  532  maybe pivoted to any desired angle with respect to the mask body  434 . The locking of the bridge member  532  in a particular position is performed by a friction engagement  432  with the mask body  510  as shown in FIG. 12. Once in the desired position the knob  550  may be configured to a tightened position whereby the angle of the bridge member  532  relative to the mask body  510  is substantially fixed by virtue of the friction engagement in the interlocking parts.  
         [0051]    The adjustment knob  550  includes a helical thread engaging with a reciprocal helical thread  440  on pin  442  running transversely through the bridge member  532 . The pin also runs through apertures in flanges  444  extending up from the mask body  510  and an internal flange from  446 . In this fashion the flanges  444  and  446  may frictionally engage (optionally also with the inner surfaces of the bridge member  532 ) once the knob  550  is in a tightened position. Adjustment may either be allowed in a finite number of predetermined positions or may be completely variable.  
         [0052]    The forehead rest of the present invention may be locked in a single position. The locking action may be provided by an engaging clip that is attached through an aperture at the base of a bridge member, similar to that disclosed in co-pending U.S. patent application Ser. No. 10/297279 or copending U.S. patent application Ser. No. 10/267279. The lock and clip may have number of ribs that engage with at least two ribs on the interior of the aperture that allows it to lock and place it in at least an upper Position and a lower position. In the upper position the locking clip is clear of the mask body and allows the bridge member to pivot freely. In the lower position the locking pin engages with a cavity on the surface of the said mask body which locks said bridge member at a predetermined angular position with respect to said mask body.  
         [0053]    Furthermore in other embodiments the forehead rest may have a spring-loaded attachment to the mask body. The force provided by the spring is adjusted to give an optimum pressure on the bridge of the use&#39;s nose. This ensures adequate sealing around the nose and prevents any excess pressure causing irritation. The spring comprises a spirally wound spring attached at one end to the mask body, and at the other to the base of the bridge member The spring is biased to provide a clockwise moment.  
         [0054]    In a further embodiment the forehead rest may have a malleable insert. The malleable insert would comprise a metal strip joining the mask body to the forehead rest. The metal can be chosen from anyone of a number of metals known in the art to provide enough malleability to be bent to a particular angle and enough stiffness to retain the angle once installed on the patient. The malleable member may be connected to the mask body by any type of mounting.  
         [0055]    In a still further embodiment the forehead rest of the present invention may be provided with a pivoting bridge member and an adjustable pivot stop as described in co-pending U.S. patent application Ser. No. 10/297279. The bridge member is attached to and pivots about pins extending from in the side of the upwardly extending inlet conduit of the mack. The pine engage with matching apertures in the bridge member.  
         [0056]    The pivot stop may be adjusted into a number of predetermined positions whereby the angle to which the forehead rest member can freely pivot is restricted. Accordingly the pivot stop requires an adjustable engagement with the bridge member. Preferably the engagement is provided with a locking clip which engages with any one of a number of mating depressions or protrusions in the bridge member. Alternatively the engagement could be provided by for example a friction engagement including some tensioned member (not shown) frictionally engaging the bridge member. The tensioned member could be releasable to allow movement and engageable to fix the position.  
         [0057]    Forehead Rest Cushion  
         [0058]    Referring to FIG. 10 one embodiment of the forehead rest cushion  560  that maybe used with the forehead rest of the present invention is illustrated. The cushion  560  in cross section generally includes a first convex member  210  and a second inner convex member  212  both of which are attached at each end to a straight base member  214 . The inner convex member  212  is a substantially flatter convex shape than the first convex member  210 . In this fashion when the cushion  560  comes into contact with the user&#39;s face the first convex member  210  deforms as more pressure is applied to the cushion towards the face. This is a first mode of deformation. Once the first convex member  21  deforms enough to contact the second convex member a second mode of deformation occurs. As will be appreciated, as the first convex member is less flat than the second convex member  212  the first mode requires less force. Once in the second mode of deformation extra force is required to deform the first convex member  210  and the second convex member  212  as well as the fact that a flatter convex shape requires more force to deform. This configuration described above results in more even deformation force across the load beating surface  216  of the cushion and also results in a more distributed force of cushioning when the cushion  560  is deformed.  
         [0059]    An alternative cushion  560 ′ that may be used with the mask and forehead rest of the present invention is shown in FIG. 13. The cushion  560 ′ is shown with a first convex member  220  attached at either end to a straight base member  222 . A second convex member  224  is inverted with respect the first convex member  220  and is attached at either end two points on the  226 , 228  on the first convex member  220 . The second convex member is lower in overall height than the first convex member  220  such that a first mode of deformation occurs when the first convex member  220  is deformed. A second mode of deformation occurs when the second convex member  224  contacts the base member  222 . The first convex member  220  and the second convex member  224  deform simultaneously. The forces across the load bearing surface  230  are further distributed by virtue of a generally quadrilateral member  232  including as one side the base member  222  which attaches over the first convex member  220  approximately at its ends and at its load bearing point  234 . The quadrilateral member  232  provides additional stiffness and reduces lateral deformation.