Nasal mask

A nasal mask assembly for preferred use in CPAP treatment. The mask assembly comprises a central body, a face cushion, a forehead support and a gas inlet. The gas inlet is rotatably connected to the central body, and the forehead support is pivotally connected to the central body. A method of using such a mask is also provided.

BACKGROUND AND SUMMARY OF THE INVENTION

This invention pertains to a nasal mask. Nasal masks may be used to deliver gases of controlled composition, at a controlled pressure, and at a controlled flow to a person's nasal passages for inhalation. Gas composition typically is controlled to achieve a particular medical goal, such as anesthesiology. Gas pressure typically is controlled to ease or assist the breathing process, made difficult for example due to high altitude or a medical condition afflicting the user.

The nasal mask described here is particularly useful with continuous positive airway pressure (“CPAP”) treatment for sleep disorders, such as obstructive sleep apnea. Pursuant to this treatment the user wears a nasal mask while sleeping. As will be readily understood by one of ordinary skill in the art, a device delivers air to the nasal mask at a pressure above atmospheric pressure. This helps the user to breathe more normally during sleep. Further descriptions of CPAP treatments and devices can be found in U.S. Pat. Nos. 5,199,424 and 5,433,193, which are hereby fully incorporated by reference. The mask may be used in the home as well as institutional settings such as long term care facilities.

The nasal mask described here also is particularly useful in a bi-level or non-invasive ventilator. As a preferred embodiment it may be used to treat chronic obstructive pulmonary disease (COPD), congested heart failure (CHF), and/or gastro esophageal reflux disorder (GERD).

The nasal mask described here has a lower profile than prior art masks. This has several advantages. It allows less restricted head movement by the user, permits quicker and less expensive manufacturing, and provides a better aesthetic appearance. One or more of these advantages may encourage treatment compliance by persons who may benefit from treatment requiring use of nasal masks.

The nasal mask described here further has an improved forehead cushion support. The position of the forehead cushion support is variable, so that a single mask may fit different persons with differently sloping foreheads. This variability permits a single mask design to fit several different persons, thus obviating to some extent the need for making masks of differing sizes. The forehead cushions also are removable from their support to allow more easy and better cleaning, as well as easy replacement. They are nonetheless attached securely to prevent them falling off unintentionally.

WRITTEN DESCRIPTION OF PREFERRED EMBODIMENTS

A preferred nasal mask assembly10is shown in the accompanying drawings, withFIGS. 1-3showing the entire assembly as a whole and the remaining Figures detailing the particular parts. The nasal mask10has two main components, a shell12and a face cushion14. The shell component12is preferably made of plastic, which is preferably optically transparent. The plastic should be impermeable to gas or air. The shell component12has several parts, including a central body16, a gas inlet18and a forehead support20.

The central body16defines a central cavity22. A circular inlet aperture24in the front of the central body16permits air to enter the central cavity22. The gas inlet18is rotatably attached to the central body16so that it covers the circular aperture24. One of ordinary skill in the art will know several methods of rotatably attaching the gas inlet18over the circular aperture24.

In the embodiment shown inFIGS. 4-8, for example, the gas inlet18defines a circular edge portion26having several flanges30, each with a groove28. The flanges30along the circular edge portion26extend into the central cavity22of the central body16. The central body rim32, which defines the circular aperture24, snaps in behind the grooves28of the flanges30, thereby sealing against the release of air from within the cavity22or gas inlet18to the outside environment.

The gas inlet18extends to a cylindrical tube portion36having a tube axis T, oriented with respect to the center axis C of the gas inlet18at a tube angle A. Where the tube portion36extends parallel to the circular aperture's center axis C the tube angle A is zero (0) degrees. Where the tube portion36extends perpendicular to the circular aperture's center axis C the tube angle A is ninety (90) degrees. The tube angle A of the nasal mask10may be anywhere from between about 0 and about 130 degrees. The upper limit for the tube angle A is dictated solely by the need to avoid the tube (not shown in drawings) interrupting head movement as much as possible. The tube angle A is preferably between 0 and about 90 degrees, more preferably between about 60 and about 90 degrees, and most preferably between about 75 and about 90 degrees. That preferred range permits the tube portion36to be made with a relatively lower profile than is available in the prior art.

The cylindrical tube portion36connects to a flexible gas delivery tube (not shown in the drawings) in such a way that the tube may rotate with respect to the cylindrical tube portion36. One of ordinary skill in the art will know of various suitable rotatable connections. For example,FIGS. 9-11show a rotation fitting38for connecting the tube to the tube portion36. The rotation fitting38has two cylindrical portions, one having a smaller diameter37than the other39, thereby defining an interior shelf40within the rotation fitting38. The cylindrical tube portion36may exhibit a fitting ring44at its end for snap fitting within the interior shelf40of the rotation fitting38. Or, the cylindrical tube portion36may alternatively exhibit several flanged projections42(not shown in the drawings), similar to the flanges30of the gas inlet18, for providing a snap fit with the rotation fitting38. The cylindrical tube portion36may further have an external ring46. The smaller diameter portion37of the rotation fitting38slides on to the tube portion36of the mask10until it abuts the external ring46. At that point either the fitting ring44just barely projects into the larger diameter39portion of the rotation fitting38, and snaps out on to the interior shelf40. The fitting ring44therefore keep the rotation fitting38from sliding off of the tube portion36, but also permits rotational movement between the elements. The tube then slides on to the larger diameter portion39of the rotation fitting38, preferably stopped by a tube ring41, and is held there by frictional forces.

The nasal mask10includes a forehead support20comprising a forehead frame50and forehead cushions52. The forehead frame50, as shown for example inFIGS. 12-17, has a horizontal member54, on which the forehead cushions52are mounted, and a vertical member56. The forehead cushions52, shown inFIGS. 18-20, are mounted on the horizontal member54in a removable manner. One example of a removable mount is shown in the drawings as raised walls57in the horizontal member54slidably receiving grooved ends59of a cushion52. A cushion52may be removed from the horizontal member54by sliding it toward a vertical slot90at the end of the horizontal member54. A ramp58adjacent the slot90permits easy removal of the forehead cushion52without allowing the forehead cushion52to unintentionally be removed. One of ordinary skill will know of other ways to attach a forehead cushion52to a supporting frame50in a removable manner.

The forehead cushions52are preferably made of a bio-friendly material such as silicone. The cushion may have internal ribs55of various configurations (two are shown in the drawings) to impart sufficiently flexible support. While two cushions52are shown in the drawings, any number of cushions52may be used in practice, for example 1, 3, 4 or more. Or no cushions may be used.

The vertical member56of the forehead frame50attaches to the central body16of the nasal mask10. The vertical member56has two arcuate grooves60, one in each side. Two arms62, preferably arcuate in shape, extend from the top of the central body16as shown inFIGS. 21-23. Each arm62has an inwardly extending ridge64for mating with a groove60in the vertical member56of the forehead support20. This arcuate ridge-in-groove attachment permits the forehead frame50to pivot with respect to the central body16, thereby accommodating user foreheads of differing slope.

The nasal mask10may include structure for maintaining the forehead support20at one of two or more discrete positions relative to the central body16. One of ordinary skill in the art will know of many ways to do this. For example, the drawings show a positioning arm66extending from the central body16, between the two arms62. The positioning arm66may alternatively, or in addition, extend from one or both arms62. The positioning arm66has two projections68, which each may mate with one or more dips70in the underside of the forehead frame vertical member56. Each dip70represents a discrete position of the forehead frame50with respect to the central body16. The positioning arm66is flexible to permit bending the arm66down so that the projections68exit a dip70, and the forehead support20may be shifted to another position.

The nasal mask10may further include structure for stopping the forehead support48at two extreme positions with respect to the central body16. There are several ways to do this, as will be known to one of ordinary skill in the art. In the embodiment shown in the drawings, a central tab72extends from the positioning arm66and into an aperture74in the vertical member56of the forehead frame50. The forehead frame50reaches one of its two extreme positions when the tab72reaches the upper or lower end of the aperture74.

A preferred face cushion component14for the mask10is shown inFIGS. 24-31. The face cushion14serves two basic functions: user comfort and sealing. Thus the face cushion14should be made of a bio-friendly elastomeric material which is both substantially gas impermeable and elastic enough to conform comfortably to the contours of a person's face. A preferred material is silicone. The face cushion14may take any shape; the shape shown in the drawings is preferred.

The face cushion14comprises a cushion body76having two opposed openings, a mask-side or “front” opening78and a face-side or “rear” opening80. The front rim82defining the front opening78sealingly fits into the rear of the shell's central body16in any one of several ways which will be known to one of ordinary skill in the art.FIG. 3, for example, shows a brace84supported within the central body16by several posts86(six are shown in the Figures). The brace84is shaped to conform to the contour of the central body's16rear rim87, leaving sufficient space between them such that the front rim82of the cushion14snugly (and substantially air-tightly) fits into the space. Thus the brace84acts to secure the cushion14to the central body16.

The cushion body76extends from the front rim82to the rear rim88. The cushion body76is sufficiently long that its elastomeric properties can provide a cushioning effect between the nasal mask10and the user's face when the mask10is worn, but not so long to make the mask10cumbersome to use during sleep. The cushion body76is sufficiently thick to provide cushioning and to prevent deformation due to pressure on the nasal mask10when tightened down on to the user's head.

The rear opening80of the face cushion14is defined by a double rim88. An inner88aand outer88brim extend inwardly from the cushion body76. The outer rim88bis relatively thin so that it may more easily conform to the contours of different persons' faces. Pressurized air entering the mask10from the tube sealingly presses the outer rim88bagainst the user's face. The inner rim88ais thicker than the outer rim88bto provide better support for the mask10against the user's face, but preferably is thin enough to provide for some adjustment against the contours of the user's face.

For the most efficient operation, the nasal mask10should be held against the user's face. This ensures a sufficiently tight seal so that an elevated pressure is maintained within the mask10and the gas delivered to the mask10does not leak to the outside environment. The mask10may be held against the user's face by hand, but that is generally not satisfactory over long periods of time.

Therefore the nasal mask10may include strap slots92for attaching straps (not shown) to the mask10. A strap end may be looped through a strap slot92and then secured, preferably with a snap or hook and loop connection. The strap then may be wrapped around the user's head and adjusted to provide a tight enough fit for maintaining a proper seal, but loose enough for the comfort of the user. The strap slots92are preferably located on opposite sides of the central body16, and perhaps on opposite sides of the horizontal member54of the forehead support20(for example, slots90may be used as strap slots in addition to providing a sliding entry for the cushions52). One of ordinary skill in the art will know of several alternatives.

The strap slots92may be formed integrally with a portion of the nasal mask shell12, such as illustrated in the drawings of the slot90. Alternatively the strap slots92may be part of a strap attachment94, such as illustrated inFIG. 1andFIGS. 32-36. The strap attachment94slips over a strap arm96on the central body16. A holder98on the strap arm96projects up into an aperture100in the strap attachment94. Thus the holder fits over and around a holder bar102, as shown inFIG. 1. A flexible tab104prevents the holder98from exiting the aperture100unless and until the strap attachment94is rotated around the holder98far enough that the flexible tab104snaps off of the holder98by flexing around to the front of the holder98. Use of the strap attachment94permits the strap to be easily attached to and detached from the central body16, with a minimal risk that the strap will be accidentally detached as the user rolls around during sleep.

The nasal mask10disclosed herein may be used in the following manner. First the user puts the mask10on his or her head and adjusts the head straps to achieve a comfortable but sealingly tight fit. A machine operates to supply air of a desired composition and pressure to a tube, as known in the art. The supplied air travels through the tube and into the tube portion36of the mask10. From there it travels into the mask shell's central cavity22, through the face cushion's front and rear openings78,80and into the user's nasal passageways, to be inhaled by the user.

The nasal mask10described herein may incorporate one or more exhaust ports106to permit gas exhaled by the user (e.g. carbon dioxide) to exit the mask10before the user's next inhalation. The exhaust port(s)106may be located somewhere in the face cushion14, in the central body16, in the gas inlet18, or even in the tube somewhere proximate the nasal mask10. In the drawings the exhaust ports106are shown in the central body16. One of ordinary skill in the art will know of several exhaust port designs which permit exhaust of gas exhaled by the user, and also do not permit exhaust of gas supplied through the tube.

The presently disclosed mask10is a nasal mask only. This device may easily be modified to become a combined nasal/mouth mask by making the central cavity16and face cushion14large enough to encompass the user's nose and mouth. Or, use of two separate nasal and mouth bodies connected by an airway conduit may be preferable to maintain a better seal with the user's face or for some other reason. Other methods of making a combined nasal/mouth mask may be known to one of ordinary skill in the art. Similarly the presently disclosed device may be made as a mouth mask only.