Abstract:
A respiratory mask assembly for delivering breathable gas to a patient includes a frame and an elbow assembly. The frame has a front surface and a rear surface adapted in use to face the patient. The frame includes a main body providing an aperture therethrough for the introduction of breathable gas into a nasal breathing cavity. The elbow assembly is swivelably coupled to the front surface of the frame. The elbow assembly includes a swivel elbow that defines an intake port and an exhaust port separated from the intake port using a baffle. The elbow assembly includes an end portion that interfaces with the aperture of the frame.

Description:
This application is a continuation of U.S. patent application Ser. No. 13/871,375, filed Apr. 26, 2013, allowed, which is a continuation of U.S. patent application No. 13,137,524, filed Aug. 24, 2011, now U.S. Pat. No. 8,439,039, which is a continuation of U.S. patent application Ser. No. 12/382,597, filed Mar. 19, 2009, now U.S. Pat. No. 8,011,369, which is a continuation of U.S. patent application Ser. No. 11/362,722, filed Feb. 28, 2006, now U.S. Pat. No. 7,523,753, which is a continuation of U.S. patent application Ser. No. 10/636,588, filed Aug. 8, 2003, now U.S. Pat. No. 7,066,178, which is a continuation of U.S. patent application Ser. No. 09/594,775, filed Jun. 16, 2000, now U.S. Pat. No. 6,691,707, which claims priority to Australian Application No. PQ 1029, filed Jun. 18, 1999, each of which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of Invention 
     The present invention relates to a connector for a respiratory mask and a respiratory mask. 
     The invention has been developed primarily for use with a breathable gas supply apparatus in Continuous Positive Airway Pressure (CPAP) treatment of, for example, Obstructive Sleep Apnea (OSA) and other ventilatory assistance treatments, such as Non Invasive Positive Pressure Ventilation (NIPPV) and will be described hereinafter with reference to these applications. However, it will be appreciated that the invention is not limited to these particular fields of use and also finds application in, for example, assisted respiration, mechanical ventilation and the like. 
     General Background and Related Art 
     CPAP treatment is a common ameliorative treatment for breathing disorders including OSA. CPAP treatment, as described in U.S. Pat. No. 4,944,310, provides pressurized air or other breathable gas to the entrance of a patient&#39;s airways at a pressure elevated above atmospheric pressure, typically in the range 3-20 cm H 2 O. 
     It is also known for the level of treatment pressure to vary during a period of treatment in accordance with patient need, that form of CPAP being known as automatically adjusting nasal CPAP treatment, as described in U.S. Pat. No. 5,245,995. 
     NIPPV is another form of treatment for breathing disorders which can involve a relatively higher pressure of gas being provided in the patient mask during the inspiratory phase of respiration and a relatively lower pressure or atmospheric pressure being provided in the patient mask during the expiratory phase of respiration. 
     In other NIPPV modes, the pressure can be made to vary in a complex manner throughout the respiratory cycle. For example, the pressure at the mask during inspiration or expiration can be varied through the period of treatment, as disclosed in the applicant&#39;s international PCT patent application No. PCT/AU97/00631. 
     Typically, the ventilatory assistance for CPAP or NIPPV treatment is delivered to the patient by way of a respiratory, preferably nasal, mask. Alternatively, a mouth mask or full face mask can be used. In this specification any reference to a mask is to be understood as incorporating a reference to a nasal mask, mouth mask or full face mask, unless otherwise specifically indicated. 
     In this specification any reference to CPAP treatment is to be understood as embracing all of the above-described forms of ventilatory treatment or assistance. 
     Breathable gas supply apparatus broadly comprise a flow generator constituted by a continuous source of air or other breathable gas generally in the form of a blower driven by an electric motor. The electric motor driving the blower is typically controlled by a servo-controller under the control of a micro controller unit. A hospital piped supply can also be used. The gas supply is connected to a conduit or tube which, in turn, is connected to the patient&#39;s mask which incorporates, or has in close proximity, a gas washout vent for venting exhaled gases to the atmosphere. The gas washout vent is sometimes referred to as a CO 2  washout vent. 
     As CPAP and NIPPV treatments are normally administered while the patient is sleeping, minimization of the noise is desirable for both the comfort of the patient and any bed partner. The exhausting of exhaled gas to the atmosphere through the gas washout vent creates noise due to turbulence generated at a shear layer between the moving vented gases and the still atmospheric air. 
     It is also desirable to locate the vent as close as possible to the mask in a location which encourages a circulation of flow within the mask so as to eliminate exhaled CO 2  through the vent and encourage inhalation of the supplied breathable gas. In this way, the retention of CO 2  within the mask is minimized. Further, by increasing the venting efficiency in this manner, the overall gas outflow is minimized, thereby reducing the opportunity for noise production. 
     One approach to minimize the noise generated by the venting of the exhaled gas is to direct the gas along an exterior surface which is a smooth prolongation of an interior surface of the outlet of the gas washout vent. This reduces the interaction between the vented gas and the still atmospheric air and, thus, the noise generated. 
     An example of the above approach is the AeroClick vent produced by MAP which has an annular vent passage that directs the exhaled gases along an adjacent cylindrical section of equal exterior diameter to the interior diameter of the annular vent. The AeroClick vent suffers from several disadvantages. Firstly, the annular vent is incorporated into a swivel mechanism which requires a certain amount of play or clearance in order to rotate freely. This play allows the components forming the interior and exterior surfaces of the annular vent passage to become misaligned and the size of the vent outlet being decreased from optimum in some regions and increased from optimum in other regions. The decreased area regions increase by the velocity of the gas flowing therethrough which increases noise and can produce an unpleasant whistling effect. Secondly, the flow of the gas from the vent outlet to a state where its velocity is in substantial equilibrium with the atmosphere is interrupted by an external shoulder closely downstream of the vent outlet. The shoulder is provided to locate the gas supply conduit. The stresses in the flow caused by the shoulder lead to the generation of noise. Additionally, the flow path from the gas conduit into the vent outlet is not smooth which introduces discontinuities into the flow which result in further noise generation. 
     Further, the AeroClick vent and other prior art devices that are of a substantially cylindrical in-line configuration, the exhaled gas must thus be forced a relatively large distance (typically around 60 mm) before reaching the outlet to the atmosphere. This reduces CO 2  washout efficiency, as noted above, and requires additional patient effort to force the gas against the direction of flow coming from the flow generator. 
     It is an object of the present invention to substantially overcome or at least ameliorate the prior art disadvantages and, in particular, to reduce the noise generated by venting exhaled gases to the atmosphere. 
     SUMMARY OF THE INVENTION 
     Accordingly, in a first aspect, the present invention provides a connector comprising: 
     a mask end for connecting in fluid communication with the interior of a respiratory mask; 
     a supply conduit end disposed at an angle to the mask end for connecting in fluid communication with the outlet of a breathable gas supply conduit; and 
     a gas washout vent passage having an inlet adjacent to, or forming part of, the mask end in fluid communication with the interior of the respiratory mask and an outlet in fluid communication with the atmosphere, the outlet including an interior surface that forms a smooth prolongation with an adjacent exterior surface of the connector, the vent outlet is disposed on the side of the connector remote the mask end, has a generally part-annular cross section and is adapted to direct the washout gas in a direction substantially perpendicular to the longitudinal axis of the mask end and substantially parallel to the longitudinal axis of the supply conduit end towards the supply conduit end. 
     The supply conduit end is preferably substantially perpendicular to the mask end. The supply conduit end can also be angled at approximately 135 degrees to the mask end. 
     Preferably, the connector includes a body portion and a cap portion, said body portion including said interior surface. The cap portion preferably also includes an interior surface spaced apart from the body portion interior surface, said body portion interior surface and said cap portion interior surface defining said vent passage therebetween. 
     The cap portion is desirably detachable from the body portion. The cap portion and body portion are also desirably rigid and fixed relative to each other when attached. The exterior of the body portion preferably includes grooves or ridges adapted to engage ridges or grooves respectively on the interior of the cap portion to attach the cap portion to the body portion. One of the body portion or cap portion preferably also includes a spacer extending between said cap portion interior surface and said body portion exterior surface. 
     In one form, the vent passage inlet is formed in the body portion adjacent to and downstream of the mask end, relative to the washout gas flow, and is in fluid communication with the mask interior via the body portion. 
     In another form, the vent passage inlet comprises part of the mask end and is in direct fluid communication with the mask interior. 
     The vent passage preferably comprises an inlet portion of relatively large cross-sectional area adjacent the vent passage inlet and an outlet portion of relatively small cross-sectional area adjacent the vent passage outlet. 
     The vent passage desirably comprises an inlet portion of constant cross-section, a relatively long outlet portion of constant cross-section and a relatively short transition portion of smoothly reducing cross-section extending from the inlet portion to the outlet portion. This shape reduces turbulence and affords a pressure drop from the interior of the mask to the outlet of the vent passage which reduces the pressure gradient at the outlet of the vent passage and, thus, reduces the noise generated. 
     The vent passage can also include internal ribs and/or an internal tortuous path to increase the pressure drop, if required. 
     The body portion is preferably of generally part toroidal shape. The cap portion is preferably of complimentary shape to a portion of the exterior of the body portion. 
     The vent passage preferably curves around the exterior of the body portion. 
     The connector desirably includes a swivel joiner at its supply conduit end, the exterior of the swivel joiner forming all, or a part, of said connector exterior surface. 
     In one form, the supply conduit end of the connector forms a smooth prolongation with the supply conduit. The supply conduit end and the supply conduit desirably have a substantially equal external diameter. 
     In another form, the swivel joiner forms a smooth prolongation with the supply conduit. The swivel joiner and the supply conduit having a substantially equal external diameter. The swivel joiner preferably includes an end of reduced external diameter adapted to be received within the interior of the supply conduit. 
     In a second aspect, the present invention provides a respiratory mask comprising: 
     a mask shell defining an interior of the respiratory mask; 
     a mask inlet for connecting in fluid communication with the outlet of a breathable gas supply conduit; and 
     a gas washout vent passage having an inlet forming part of the mask shell and in fluid communication with the interior of the respiratory mask and an outlet in fluid communication with the atmosphere, the outlet including an interior surface that forms a smooth prolongation with an adjacent exterior surface of the mask shell, the vent outlet is disposed on the side of the mask remote the mask interior and is adapted to direct the washout gas in a direction substantially parallel to the longitudinal axis of the mask inlet and away from the mask inlet. 
     Preferably, the mask shell includes a body portion and a cap portion, said body portion including said interior surface. The cap portion preferably also includes an interior surface spaced apart from the body portion interior surface, said body portion interior surface and said cap portion interior surface defining said vent passage therebetween. 
     The cap portion is desirably detachable from the body portion. The cap portion and body portion are also desirably rigid and fixed relative to each other when attached. The exterior of the body portion preferably includes grooves or ridges adapted to engage ridges or grooves respectively on the interior of the cap portion to attach the cap portion to the body portion. One of the body portion or cap portion preferably also includes a spacer extending between the interior surface of the cap portion and the exterior surface of the body portion. 
     The vent passage preferably comprises an inlet portion of a relatively large cross-sectional area adjacent the vent passage inlet and an outlet portion of a relatively small cross-sectional area adjacent the vent passage outlet. 
     The vent passage desirably comprises a relatively long inlet portion of constant cross-section, a relatively long outlet portion of constant cross-section and a transition portion of smoothly reducing cross-section extending from the inlet portion to the outlet portion. 
     The vent passage preferably substantially follows the shape of the exterior of the body portion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of a first embodiment of a connector in accordance with the first aspect of the invention, shown attached to a nasal respiratory mask and forehead support; 
         FIG. 2  is a cross-sectional side view of the connector shown in  FIG. 1 ; 
         FIG. 3  is a perspective view of the connector shown in  FIG. 1 ; 
         FIG. 4  is a perspective view of the connector shown in  FIG. 1  with the cap portion removed; 
         FIG. 5  is an underside perspective view of the cap portion of the connector shown in  FIG. 1 ; 
         FIG. 6  is a cross-sectional side view of a second embodiment of a connector in accordance with the first aspect of the invention; 
         FIG. 7  is a cross-sectional side view of a third embodiment of the connector in accordance with the first aspect of the invention; 
         FIG. 8  is a cross-sectional side view of a first embodiment of a respiratory mask in accordance with the second aspect of the invention; and 
         FIG. 9  is a cross-sectional side view of a fourth embodiment of the connector in accordance with the first aspect of the invention 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIGS. 1 to 5  show a first embodiment of the first aspect of the invention in the form of connector  10 . The connector  10  is shown attached to a nasal respiratory mask  12  and forehead support device  14 . The connector  10  is also suitable for use with a full face (i.e., nose and mouth) respiratory mask. 
     The mask  12  comprises a substantially rigid mask shell  15 , a flexible mask cushion  16  and two slotted lower head strap connectors  18  (only one connector shown). 
     The forehead support device  14  includes a lower portion  20  which is pivotally mounted to an upper portion  22 . The upper portion  22  includes forehead cushions  24  and two slotted upper head strap connectors  26  (only one cushion/connector shown). 
     As best shown in  FIG. 2 , the connector  10  includes a mask end  28  for connecting in fluid communication with the interior of the respiratory mask  12  and a supply conduit end  30  disposed substantially perpendicularly to the mask end  28  for connecting in fluid communication with the outlet of a breathable gas supply conduit  31 . The mask end  28  is rotatably coupled to the mask shell  15  by a retaining ring  29 . The close proximity of the inlet ports  41 , and the vent passage  32  overall, to the interior of the mask  12  advantageously increases CO 2  washout efficiency. 
     The connector  10  also includes a gas washout vent passage, indicated generally by the reference numeral  32 , a body portion  34 , a detachable cap portion  36  and a detachable swivel joiner  38 . The conduit  31  is a non-rotatable friction push fit over end  38   a  of the swivel joiner  38 . The end  38   b  of the swivel joiner  38  is a rotatable snap-engage fit with reduced diameter portion  39  of the body portion  34 . The portion  39  is formed from resilient fingers to allow flexing during snap-engagement with the swivel joiner  38 . 
     The vent passage  32  includes a pair of inlet ports  41  (see  FIG. 4 ) formed in the body portion  34  of the connector  10  adjacent the mask end  28 . The inlet ports  41  are in fluid communication with the interior of the mask  12  via the mask end  28 . The vent passage  32  also includes an outlet  40  opening to the atmosphere. The outlet  40  includes an interior surface  42  (comprising an exterior surface of the body portion  34 ) that forms a smooth prolongation with an adjacent exterior surface  44  of the body portion  34 . The smooth prolongation between the interior surface  42  and exterior surface  44  reduces noise by allowing the exhaled gases to vent along a continuous surface, as previously described. In order to minimize interruptions or disturbances that could generate turbulence downstream of the outlet  40 , and thus noise, the adjacent exterior surfaces  46 ,  48  of the swivel joiner  38  and the gas supply conduit  31  respectively are also formed as smooth prolongations of the interior surface  42  and adjacent exterior surface  44 . 
     As best shown in  FIG. 3 , the vent passage outlet  40  is of generally part annular cross-section subtending an angle of approximately 180° and is located on the side of the connector  10  remote the mask end  28  and, thus, the mask  12 . This ensures that gas is only vented along surfaces displaced, and facing away, from the mask  12  and the patient, which again minimizes the risk of the vented gases encountering noise-producing obstructions. 
     Returning to  FIG. 2 , it can be seen that the vent passage  32  comprises an inlet portion  50  of relatively large cross-sectional area compared to an outlet portion  52  of relatively small cross-sectional area. This provides a substantial pressure drop across the vent passage  32  and reduces the pressure drop between the outlet  40  and surrounding atmospheric air, again minimizing noise production. Also, the outlet portion  52  is relatively long in order to allow the gas to approach a laminar state and, thus, minimize turbulence before the gas exits to the atmosphere. A smooth tapering transition portion  54  is disposed between the inlet portion  50  and the outlet portion  52  which minimizes noise production by minimizing the introduction of any discontinuities into the gas flow. 
     As best shown in  FIGS. 3 and 4 , the body portion  34  includes grooves  56  which are adapted to engage with ridges  58  provided on the cap portion  36  to allow the cap portion  36  to be manually attachable detachable to/from the body portion  34  for ease of cleaning and replacement. As best shown in  FIG. 5 , the cap portion  36  also includes an interior strengthening rib  60  to provide rigidity and ensure the cross-sectional area of the vent passage  32  is not reduced due to external pressure, as may be caused by the patient rolling over onto their face during sleep. The detachable cap portion  36  also makes disassembly for cleaning easier and allows cap portions of various sizes to be used with a single body portion  34 , thereby allowing the size and shape of the vent passage to be easily and quickly varied for particular treatment applications. 
     Although the connector  10  has been described with reference to the swivel joiner  38  being interposed between the connector  10  and the breathable gas supply conduit  31 , it will be appreciated that the conduit can be joined directly to the body portion  34  if the ability to swivel is not required or if a swivel is provided elsewhere in the gas supply circuit. In that case, it is, of course, desirable for the external diameter of the gas supply conduit  31  to be equal to the adjacent external diameter of the exterior surface of the body portion  34 . 
     A second embodiment of connector  80  in accordance with the first aspect of the invention is shown in  FIG. 6 . Like reference numerals to those used in describing the first embodiment are used to indicate like features in the second embodiment. 
     The primary difference between the connector  10  and connector  80  is that the inlet ports  41  are omitted and an inlet port  82  of the gas washout vent passage  32  is incorporated into the mask end  28  of the connector  80 . Thus providing direct fluid communication between the interior of the mask  12  and the vent passage  32  and further minimizing CO 2  retention. The inlet portion  50  of the vent passage  32  also provides a relatively long distance over which a gradual reduction in pressure can be achieved. Further, the interior surface of the vent passage outlet  40  forms a smooth prolongation with the adjacent exterior surface  46  of the swivel joiner  38  rather than the body portion  34 , as with the first embodiment. 
       FIG. 7  shows a third embodiment of the connector  90  according to the first aspect of the invention. Like reference numerals to those used in describing the first embodiment will again be used to indicate like features in the third embodiment. The connector  90  also has the vent passage  32  in direct fluid communication with the interior of the mask  12 . However, in this embodiment, an inlet port  92  is formed in the mask shell  15 . 
       FIG. 9  shows a fourth embodiment of the connector  130  according to the first aspect of the invention. Like reference numerals to those used in describing the first embodiment will again be used to indicate like features in the fourth embodiment. The connector  130  also has an inlet port  132  formed in the mask shell  15 , similar to the third embodiment. However, in this embodiment, both the interior surface  42  and the smoothly prolongating adjacent exterior surface  46  are provided on the swivel joiner  38 . As the gas vents to the atmosphere downstream of the join  134  between the swivel joiner  38  and the body portion  34 , then any gas leaking through the join  134  cannot disturb the flow of gas at, or after, the outlet  40 . In this way, a further opportunity for turbulence, and thus noise generation, is eliminated. 
       FIG. 8  shows a first embodiment of a nasal respiratory mask  100  in accordance with the second aspect of the invention. The mask  100  includes a mask shell  102  and a mask cushion  104 . The mask shell  102  includes a mask inlet  106  for connecting in fluid communication with the outlet of the breathable gas supply conduit  108 . The mask  100  includes a gas washout vent passage indicated generally by the reference numeral  110 . 
     The mask shell  102  is comprised of a body portion  112  and a detachable/attachable cap portion  114 . The vent passage  110  includes an inlet port  116  formed in the body portion  112  of the mask shell  102 . The inlet port  116  is in direct fluid communication with the interior of the mask  100 . The vent passage  110  also includes an outlet  118  in fluid communication with the atmosphere. The outlet  118  includes an interior surface  120  on the exterior of the body portion  112  that forms a smooth prolongation with an adjacent surface  122  also provided on the exterior of the body portion  112 . The outlet  118  is adapted to direct the washout gas in a direction substantially parallel to the longitudinal axis of the mask inlet  106  and away from the mask inlet  106 . 
     As with earlier embodiments, the noise produced by venting the exhaled gas to the atmosphere is minimized by directing the vented gas on a smooth continuing surface before and after the outlet  118  and away from the mask  100 , the patient and other potential disturbances. Additionally, as with the earlier connector embodiments, the cap portion  114  is detachable from the body portion  112  for cleaning and or replacement with a cap portion of same, or different, size or shape. The vent passage  110  also similarly comprises an inlet portion  124  of relatively large cross-sectional area, a relatively long outlet portion  126  of relatively small cross-sectional area and a transition portion  128  of smoothly reducing cross-section extending from the inlet portion  124  to the outlet portion  126 . 
     Although the invention has been described with reference to the preferred embodiments, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms.