Abstract:
A breathing assistance apparatus ( 200 ) is disclosed, for use with delivery of respiratory gases to a patient. The breathing assistance apparatus includes a patient interface, having a body section adapted to cover the nose, or nose and mouth of a patient and a sealing interface. The sealing interface includes at least an outer sealing member. The outer sealing member ( 201 ) is adapted to attach to the body section in a sealing manner and has a substantially thin section ( 203 ) in at least its nasal bridge region. The thin section is substantially thinner than the rest of the outer sealing member.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     This invention relates to patient interfaces particularly though not solely for use in delivering CPAP therapy to patients suffering from obstructive sleep apnoea (OSA).  
         [0003]     2. Summary of the Prior Art  
         [0004]     In the art of respiration devices, there are well known 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.  
         [0005]     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.  
         [0006]     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.  
         [0007]     Where such masks are used in respiratory therapy, in particular treatment of obstructive sleep apnea (OSA) using continuance 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. A further requisite of such masks is the washout of gas from the mask 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 any bed partners.  
         [0008]     In common with all attempts to improve the fit, sealing and user comfort is the need to avoid a concentrated flow of air at any portion of the respiratory tracts. In particular with oral masks or mouthpieces it is a disadvantage of prior art devices that the oral cavity may become overly dehydrated by use of the device, causing irritation and possible later complications.  
         [0009]     Furthermore, a common complaint of a user of CPAP therapy is pressure sores caused by the mask about the nose and face and in particular in the nasal bridge region of the user.  
       SUMMARY OF THE INVENTION  
       [0010]     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.  
         [0011]     Accordingly in a first aspect the present invention consists in a breathing assistance apparatus, for use with delivery of respiratory gases to a patient comprising:  
         [0012]     a patient interface, having a body section adapted to cover the nose, or nose and mouth of said patient,  
         [0013]     a sealing interface, including at least an outer sealing member, said outer sealing member adapted to attach to said body section in a sealing manner, said outer sealing member having a substantially thin section in at least its nasal bridge region, said thin section being substantially thinner than the rest of said outer sealing member,  
         [0014]     wherein said outer sealing member is adapted to seal around the facial contours of said patient thereby providing a sealed fluid communication to the respiratory tract of said patient.  
         [0015]     The invention consists in the foregoing and also envisages constructions of which the following gives examples. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]     Preferred forms of the present invention will now be described with reference to the accompanying drawings.  
         [0017]      FIG. 1  is a block diagram of a humidified continuous positive airway pressure (system) as might be used in conjunction with the sealing interface of the present invention.  
         [0018]      FIG. 2  is an illustration of the nasal mask including a sealing interface in use according to the preferred embodiment of the present invention.  
         [0019]      FIG. 3  shows a perspective view of a mask with a sealing interface that is a cushion.  
         [0020]      FIG. 4  is a cutaway view of the mask showing the sealing interface cushion that has an inner sealing member and an outer sealing member.  
         [0021]      FIG. 5  is a cutaway view of the periphery of the outer sealing member or membrane.  
         [0022]      FIG. 6  is a cutaway view of the periphery of the mask body portion.  
         [0023]      FIG. 7  shows a mask and sealing interface as used with a forehead rest on a patient.  
         [0024]      FIG. 8  shows a cross section of a second preferred embodiment of the sealing interface.  
         [0025]      FIG. 9  shows perspective view of an inner sealing member of the second preferred embodiment of the sealing interface.  
         [0026]      FIG. 10  shows a cross section of a third preferred embodiment of the inner and outer sealing members of the present invention.  
         [0027]      FIG. 11  shows a perspective view of the inner sealing member of the third preferred embodiment of the sealing interface.  
         [0028]      FIG. 12  shows a plan view of the inner sealing member of the third preferred embodiment of the mask cushion.  
         [0029]      FIG. 13  shows a cross section of a fourth preferred embodiment of the sealing interface of the present invention.  
         [0030]      FIG. 14  shows a perspective view of the inner sealing member according to a fifth preferred embodiment of the sealing interface of the present invention.  
         [0031]      FIG. 15  shows a cross section of a sixth preferred embodiment of the sealing interface of the present invention.  
         [0032]      FIG. 16  shows a perspective view of the inner sealing member according to a seventh preferred embodiment of the sealing interface of the present invention.  
         [0033]      FIG. 17  shows a perspective view of the inner sealing member according to an eighth preferred embodiment of the sealing interface of the present invention.  
         [0034]      FIG. 18  shows a perspective view of the inner sealing member according to a ninth preferred embodiment of the sealing interface of the present invention.  
         [0035]      FIG. 19  shows a perspective view of the inner sealing member according to a tenth preferred embodiment of the sealing interface of the present invention.  
         [0036]      FIG. 20  shows a cross section of a further embodiment of the sealing interface of the present invention where the inner sealing foam member touches the outer sealing member at all times.  
         [0037]      FIG. 21  is a side view of a nasal mask of the present invention where the outer sealing member is substantially thinner in width in the nasal bridge region than the rest of the outer sealing member.  
         [0038]      FIG. 22  is a close-up view of detail A in  FIG. 21 .  
         [0039]      FIG. 23  is a perspective view of the nasal mask of  FIG. 21 .  
         [0040]      FIG. 24  is a cross-section of the outer sealing member of  FIG. 21 .  
         [0041]      FIG. 25  is a front perspective view of a full face mask of the present invention, where the outer sealing member is substantially thinner in width in the nasal bridge region than the rest of the outer sealing member.  
         [0042]      FIG. 26  is a back perspective view of a full face mask of  FIG. 25 .  
         [0043]      FIG. 27  is a cross-section through BB of the full face mask of  FIG. 25 .  
         [0044]      FIG. 28  is a perspective view of the outer sealing member of the fall face mask of  FIG. 25  in isolation, where the thin nasal bridge region is particularly shown.  
         [0045]      FIG. 29  is a cross-section through CC of the outer sealing member of  FIG. 28 .  
         [0046]      FIG. 30  is a front view of the outer sealing member of  FIG. 28 .  
         [0047]      FIG. 31  is a front view of a first alternative outer sealing member.  
         [0048]      FIG. 32  is a front view of a second alternative outer sealing member.  
         [0049]      FIG. 33  is a front view of a third alternative outer sealing member. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0050]     The sealing interface of the present invention provides improvements in the delivery of CPAP therapy. In particular a patient interface is described which reduces the pressure of the mask on the patient&#39;s face and may be quieter for the patient 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 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.  
         [0051]     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  which may comprise a microprocessor based controller executing computer software commands stored in associated memory.  
         [0052]     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 .  
         [0053]     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 .  
         [0000]     Nasal Mask  
         [0054]     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 patient  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.  
         [0055]     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.  
         [0000]     Mask Cushion  
         [0056]     Referring now to  FIGS. 3 and 4  in particular, the mask cushion  1104  is provided around the periphery of the nasal mask  1102  to provide an effective seal onto the face of the patient 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  2108  (see  FIG. 7 ) to adapt to the individual contours of any particular patient. In particular, there is an indented section  1150  intended to fit over the bridge of the patient&#39;s nose as well as an indented section  1152  to seal around the section beneath the nose and above the upper lip.  
         [0057]     In  FIG. 4  we see that the mask cushion  1104  is composed of an inner sealing member that is an inner cushion  1110  covered by an outer sealing sheath or member  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 patient&#39;s face. In other forms the inner cushion  1110  may be formed of other appropriate material, such as silicone or other composite materials. 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 .  
         [0058]     In the preferred embodiment of the present invention as shown in FIGS.  4  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.  
         [0059]     The outer sheath  1112  fits in place over the cushion  1110 , holding it in place. The sheath  1112  is secured by a snap-fit to the periphery  1114  of the hollow body. In FIGS.  5  to  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.  
         [0060]     A second preferred embodiment to the mask cushion is depicted in  FIGS. 9 and 10 . In the second embodiment the inner cushion  2000  includes a raised bridge  2002  in the nasal bridge region. The raised bridge  2002  can also be described as a cut out section made in the cushion. Also, the notch in the contacting portion (between the inner cushion and outer sheath) is less pronounced than proceeding embodiments. However, as the raised bridge  2002  is unsupported it is much more flexible and results in less pressure on the nasal bridge of the patient. The outer sheath  2004  contacts the inner cushion  2000  throughout the raised bridge  2002 . The peaks  2005 ,  2007 ,  2009 ,  2011  in the inner cushion  2000  between each of the indented sections  2006 ,  2008  and the raised bridge  2002  contact the outer sheath  2004  and when in use the sheath  2004  contacts the facial contours of the patient in the regions of these peaks.  
         [0061]     Referring particularly to  FIG. 10  the inner cushion  2000  includes a cheek contour  2006  to follow the cartilage extending from the middle of the nose, and a contoured lip sealing portion  2008  to seal between the base of the nose and the upper lip.  
         [0062]     Referring now to  FIGS. 11 and 12  a third preferred embodiment of the mask cushion is depicted, in this case, the inner cushion  2010  tapers down  2012  towards the nasal bridge region  2014 . For a short portion either side of the nasal bridge region  2014  the inner cushion  2010  is absent, forming a semi annular form in plan view as seen in  FIG. 12 .  
         [0063]     Referring to  FIG. 13 , a fourth preferred embodiment of the mask cushion is depicted. The outer sheath  2020  is adapted to contact the inner cushion  2022  completely about the inner cushion, including in the nasal bridge region  2024  and the check contour  2026 .  FIG. 18  shows the inner cushion  2022  where the upper edge  2050  of the cushion does not have any contours and thus will contact the outer sheath all around the edge of the inner cushion.  FIG. 20  shows a sealing interface similar to that of  FIG. 13  where the inner cushion also follows and touches the outer sheath all around its edge.  
         [0064]      FIG. 14  illustrates a fifth preferred embodiment of the inner cushion  2030 . In the nasal bridge region  2032  the inner cushion includes a lower bridge  2034  and upper bridge  2036 . Due to the gap the upper bridge  2036  is unsupported to reduce pressure on the patient&#39;s nasal bridge, but the lower rim  2034  of the inner cushion  2030  is continuous, which aids installation.  
         [0065]     In yet other forms of the sealing interface of the present invention the inner cushion may be provided with other contours on the front side of the inner cushion or cut outs on the back side of the inner cushion, so that in the areas where there are regions cut out of the back side of the cushion the cushion is more flexible. In particular, cut outs in the nasal bridge, cheek and upper lip regions provide the patient with a mask cushion that is more flexible and thus more comfortable.  FIG. 15  shows an embodiment of an inner cushion  2024  that has a curved cut out or dead space  2044  in the cheek region.  FIGS. 16 and 17  show embodiments of an inner cushion  2000  that has a cut out or dead space  2046  in the area where the patient&#39;s upper lip rests in the foam.  
         [0066]     A final form of a sealing interface is shown in  FIG. 19 , here the inner foam member has an annular shape but has a thin bridge or membrane  2048  that extends across and provides flexibility to the nasal bridge region.  
         [0067]     Referring now to  FIG. 21 , to improve the comfort to the patient the nasal mask  200  includes a thin bridge section  203  in the nasal bridge region of the outer sealing member  201 , that is, that part extending over the bridge of a patient&#39;s nose.  
         [0068]     Similar to described above the outer sealing member or outer sheath  201  fits in place over the inner sealing member (inner cushion)  202 , holding it in place. The outer sheath  201  is secured by a snap-fit to the periphery  205  of the mask hollow body  204 . The periphery  205  is shown including an outer bead  206 . The outer sheath  201  includes a matching bead  207 , whereby once stretched around the periphery  205 ; the two beads engage to hold the outer sheath  201  in place.  
         [0069]     The outer sealing member or sheath  201  is shown in more detail in FIGS.  22  to  24 . The outer sheath  201  has formed in it a region  203  that is thinner than the remainder of the cross-sectional thickness  210  of the sheath. In particular, the side walls  211 ,  212  (see  FIG. 23 ) must be thicker than in the region  203  so as to provide structural support for the sheath and ensure the sheath does not collapse in use, or when being assembled with the mask body. As an example only, for a nasal mask, if the thin bridge region was 0.2 mm thick, the side walls may be 0.3 to 0.6 mm thick. Therefore, the thin bridge region  203  is approximately half the thickness of the rest of the sheath  201  and so can provide a significant effect, such that the pressure to the patient&#39;s nose in the nasal bridge region is reduced compared to when a sheath does not have any reduced thickness section. Furthermore, a thin bridge region  203  in the outer sheath  201  allows for different sized patient&#39;s to comfortably use the mask and outer sheath of the present invention.  
         [0070]     In use, when a force is placed against the outer sheath  201  the thin bridge region  203  will collapse more than the rest of the outer sheath  201 . Therefore, this section  203  is more flexible and allows for added patient comfort.  
         [0071]     Referring particularly to  FIG. 22 , the thin bridge region  203  on the outer sheath  201  preferably does not extend completely to the outer edge  211  of the outer sheath  201 , but grows thicker in thickness. This is because the outer edges of the outer sheath  201  when thicker are less prone to tearing.  
         [0072]     In particular, in  FIG. 23 , that outer sheath  201  is substantially heart shaped and the thin bridge region  203  is shown to extend more than halfway down the sides of the sheath from the apex  213 . As shown in  FIG. 23 , the thin bridge region  203  does not extend fully down the edges  211  and  212  of the outer sheath  201 . This is because support is required in the edges of the sheath  201 , to provide structural stability of the sheath.  
         [0073]     In other forms of the nasal mask of the present invention, the thin bridge region may not extend as far as that shown in  FIG. 23 , but be restricted merely to the nasal bridge region (similar in manner to the mask cushion shown in  FIG. 30 , in relation to a full face mask).  
         [0000]     Full Face Mask  
         [0074]     A further embodiment of the present invention is shown in FIGS.  25  to  31  where the patient interface is a full face mask similar to that described in co-pending New Zealand patent application number 528029. The full face mask  300  includes a hollow body  302  and outer sealing member or mask cushion  301 . The cushion  301  is attached to the body  302  in a similar manner as described with reference to the nasal mask, but here no inner cushion is provided. Thus, the cushion  301  periphery extends over a flange on the mask body.  
         [0075]     The hollow body  302  has an integrally formed recess (not shown) in which an insert  304  is fitted into. The recess and insert  304  each have complimentary circular apertures (generally indicated as  305 ) that form an inspiratory inlet when the insert  304  is placed in the recess. The inlet  304  is capable of being connected to the tubing that forms the inspiratory conduit  3  (as shown on  FIG. 1 ). Gases, supplied to the inspiratory conduit  3  from the CPAP device and humidifier, enter the mask through the apertures  305  and the patient is able to breathe these gases. The mask  300  is positioned around the nose and mouth of the patient and headgear (not shown) may be secured around the back of the head of the patient to assist in the maintaining of the mask on the patient&#39;s face. The restraining force from the headgear on the hollow body  302  ensures enough compressive force on the mask cushion  301  to provide an effective seal against the patient&#39;s face.  
         [0076]     The hollow body  302  and insert  304  are injection moulded in a relatively inflexible material, for example, polycarbonate plastic. Such a material would provide the requisite rigidity for the mask as well as being transparent and a relatively good insulator. The mask cushion  301  is preferably made of a soft plastics material, such as silicone, KRATON™ or similar materials.  
         [0077]     The cushion  301  of the mask  300  includes a thin bridge section  305  in the nasal bridge region of the cushion  301 , that is, that part extending over the bridge of a patient&#39;s nose. As an example, in the region of the thin bridge section  305  the walls of the cushion may be 0.2 to 0.3 mm thick and the rest of the cushion may have a thickness of 1 mm. In particular, the side walls need to be thicker to provide support in the cushion, so that it does not collapse during use or assembly with the mask body. In  FIG. 29 , this is particularly illustrated, as the section  305  in the nasal bridge region is shown as being much thinner than the rest of the cushion (in particular the bottom side wall region  306 , which are much thicker in cross-section).  
         [0078]     Note must be made that the inner flange  307  of the cushion  301  that rests against the patient&#39;s face is also thinner in section than the side walls of the cushion  301  to provide flexibility to the cushion and thus comfort to the patient. In use, the inner flange  307  is the area of the cushion that seals against the patient&#39;s face and the side walls of the cushion provide stability to the cushion  301 .  
         [0079]     In use, when a force is placed against the cushion  301  the thin bridge section  305  will collapse more than the rest of the cushion  301 . Therefore, this section  305  is more flexible and allows for added patient comfort.  
         [0080]     Other forms of the cushion that may be used with the fall face mask of the present invention are shown in FIGS.  31  to  33  and each show alternative thin sections that may be provided for patient comfort, and to allow for fitting to different sized patients.  
         [0081]     Referring first to  FIG. 31 , cushion  310  may have a thin bridge section  311  that is narrower than that shown in  FIG. 30 .  
         [0082]     In  FIG. 32  the cushion  312  has a thin bridge section  313  only near the outer edge  317  of the cushion  312 . This cushion  312  also had a thin section  314  in the region of the cushion that would rest against the patient&#39;s chin.  
         [0083]     Finally, in  FIG. 33 , the thin section  316  of the cushion  315  may extend down the sides  318 ,  319  of the cushion.  
         [0000]     Forehead Rest  
         [0084]     The nasal mask and/or fall face mask of the present invention is preferably provided with a fixed forehead rest ( 208 , as shown in relation to the nasal mask in  FIGS. 21 and 23  or  303 , as shown in relation to the full face mask in  FIG. 25 ). The forehead rest is not required to be adjustable as the cut out in the nasal bridge region of the inner foam (for the nasal mask) and the thin section in the outer sheath (for both the nasal and full face masks) provides enough flexibility of the mask cushion to provide fitting to a number of different patients.