WO2004108199A1 - Respiratory face mask - Google Patents

Abstract

A respiratory mask (10) suitable for the treatment of sleep apnea is formed from an inner layer (14) of plastic material molded to the shape of the face of the patient (12). Air is supplied to the mask from a flexible hose (28) connected to the inlet end of a bifurcated air supply tube (26) molded into the mask. Tube (26) discharges air into a plenum chamber formed between the layers (14,16) just below the nostrils of the patient (12) and is inhaled through nostril holes in the inner layer (14). Exhaled air and overflow air from supply tube (26) is discharged through the ends of a tubular a muffler assembly (34) that is mounted transversely adjacent the upper lip of the patient (12). Diffuser plugs (3) are inserted into the outer ends of the muffler to attenuate the noise of the discharging air and to disperse its flow. The mask (10) is held in place by a neck strap (36) that is anchored to hooks (40) on the ends of the muffler assembly (34), and by a pate harness that is attached to hooks (44) in the forehead portion (18) of the mask (10). The construction is such that incoming air does not contact the skin of the patient's face and, therefore, does not tend to lift or move the mask from or on the face of the patient during use.

Description

TITLE: RESPIRATORY FACE MASK

TECHNICAL FIELD

This invention relates to respiratory face masks through which gas can be supplied under pressure to the nose of a human over an extended period of time.

The respiratory face masks of this invention are particularly, though not exclusively, suitable for use with continuous positive airway pressure (CPAP) therapy for the treatment or alleviation of obstructive sleep apnea, disordered breathing during sleep, and similar human conditions. In such therapy, the patient sleeps with the mask fitted to the face and air is supplied to the nose under positive pressure via the mask.

In this specification a respiratory face mask is one that fits over and around the nose of the patient, is strapped or otherwise fixed to the head and is fitted with an air inlet tube. This is to be distinguished from a nose box that rests on, or is strapped onto, the upper lip of the patient and feeds air into the nostrils via a pair of short outlet tubes or spigots. The nose box is fitted with one or two air inlet tubes and, thus, forms a manifold that that distributes air into the nostrils. Though the nose box does not cover the nose of the patient, it is sometimes confusingly referred to as a 'nose mask' in the art.

Respiratory masks - whether face masks or nose boxes - are often loosely referred to in the art as 'sleep apnea masks'. The term 'respiratory face mask' will be used herein to both indicate a mask that covers the nose and one that is not necessarily limited to the treatment of sleep apnea.

Of course, simple nostril tubes that supply air (usually oxygen enriched) directly into the nostrils without any mask or manifold are quite different again and are not relevant here.

BACKGROUND TO THE INVENTION

While the benefits of CPAP therapy are well recognized, it has proven difficult to devise a face mask that: can be comfortably worn for hours by a sleeping patient, allow normal movements of the patient during sleep, does not exhaust air in a noisy or drafty manner that is likely to disturb the patient's bed partner, and, ensures delivery of air to the patient's nostrils at the required pressure without leakage.

Conventional respiratory face masks almost universally comprise a cup-like cover that has a soft peripheral edge which fits around the nose and upper lip of the patient, the cover being supplied with air via a flexible tube and being provided with an exhaust vent through which excess applied air is continuously discharged, along with air exhaled by the patient, from the mask. A mask that is soft and lightweight tends to be lifted off the face by the air pressure and to leak air around the edges. It is also easily dislodged when the patient lies on one side or turns while asleep. A stiffer mask that is strapped firmly to the patient's head tends to be uncomfortable. Whether soft or rigid, the exhausting of air from such masks tends to be noisy and disturbing to both the patients and their bed partners.

In my prior international patent application WO 00/35525, 1 disclosed a respiratory face mask that was custom-molded to the contour of the patient's face, covering the forehead, nose, cheeks and chin and having holes for the eyes and mouth. The mask included a 'transfer box' over the nose with a large opening on which a swivel-mounted air inlet hose was fitted. This mask had the advantage that it was comfortable, could be held to the patient's head with little force and yet be secure against dislodgement by normal movement. However, the swiveling air inlet over the transfer did not allow a flat profile and I considered that superior silencing and exhaust dispersal would be desirable.

US patent application 20020014241 by Gradon et al discloses a typical triangular cup-like face mask that fits over the nose and is fitted with a central upwardly extending air inlet tube that allows an air hose to be connected at the level of the forehead. In an attempt to silence exhausting air, a plurality of exhaust holes are formed in the front of the mask and are covered by a removable filter-like diffuser cap. The mask not only tends to lift off the face under air pressure and leak around the edges but the diffuser cap further increases the substantial profile of the mask, making it more prone to dislodgement and leakage as the patient turns or lies on one side.

US patent 5,937,851 to Serowski et al discloses a face mask of typical triangular shape but wherein the inlet is in the form of a swiveling elbow that protrudes from the front of the mask for connection to the air supply. In this case, however, a tubular silencer connects the air supply hose to the elbow, allowing air to be exhausted along coaxial passages and slots formed in the hose. As in the previous example of the prior art, this type of mask not only tends to be lifted from the face under air pressure but has a large profile that makes the mask prone to movement or dislodgement when the patient sleeps on one side or turns in bed. Another more conventional face mask with a swiveling inlet nozzle over the nose is disclosed in US patent 6,467,483 to Kopacko, more than 50 items of prior art relating to similar masks being referenced in this patent.

International patent application by Breas Medical AB [publication No. WO 00/59567] discloses a very small face mask that may rightly be called a 'nose mask'. It is shaped to the contour of the individual patient's nose, covering only the nose from the bridge to the start of the upper lip. Air inlet and exhaust hoses are affixed to the mask opposite the nostrils or to one end of a 'nose bone' cross-tube above the upper lip having side holes opposite the nostrils. While this mask obtains a commendably low profile, it is so small that it must be strapped tightly to the head to ensure a satisfactory seal despite the tugging of the inlet hose during normal movements while the patient is asleep. The forces on the mask will be particularly great if the inlet hose is attached to one end of a cross-tube as proposed in one example. The need to fit such a small mask so tightly makes it uncomfortable to wear. The discomfort is exacerbated because the arrangement of air inlet and exhaust hoses/tubes makes sleeping on one's side difficult. Either the inlet hose is forced into the pillow or the exhaust outlet is blocked by the pillow. Further, due to the necessarily restricted exhaust opening, masks of this type will be noisy.

It might be noted in passing that nostril boxes having an air manifold located on the patient's top lip with outlet protrusions that fit in the nostrils of the patient are also of commendably low profile but have similar problems to the last described 'nose mask' with respect to securing the device to the head in a comfortable manner. While air pressure in the nostril box does not tend to lift the device from the face of the patient, it does tend to move the manifold away from the nostrils. As in the previously referenced item of art, the small size of the device makes diffusion of exhaust air difficult so that it tends to be noisy. Also the supply hose(s) tend to tangle or wrap about the head of the patient during normal sleep movements. An example of this type of 'nostril box' is provided by US patent 6,478,026 to Wood, against which some 70 references relating to similar devices were cited.

OUTLINE OF THE INVENTION

From one aspect, this invention comprises a respiratory facemask with forehead, nose and nostril portions, having an air inlet passage extending from near the forehead portion to the nostril portion in a manner such that the inlet air does not come into contact with the patient's skin and, thereby, tend to lift the mask from the patient's face. A low profile may be achieved by having a fixed upwardly- pointing air inlet adjacent the forehead portion of the mask area and a bifurcated air passage extending down each side of the nose bulge.

The nostril portion of the mask preferably includes a plenum chamber having outlet means for directing air from the chamber into the nostrils of a patient wearing the mask and having air exhaust means adapted to exhaust exhaled and excess inlet air from the chamber. The air from the air passage may be discharted directly into the plenum chamber or it may be discharged into the exhaust means and from thence into the plenum chamber. The air outlet means may comprise a pair of short, thin and flexible tubular protrusions adapted to enter the nostrils of a patient wearing the mask. The exhaust means may comprise a transverse open- ended tubular muffler arranged to receive exhaust air (including air exhaled from the nostrils) from the plenum chamber through one or more side orifices and to exhaust the air through diffuser means located within the open ends of the transverse tube. Air may also be discharged downwardly from one or more diffusers located in the bottom of the muffler tube. It will be convenient to attach the ends of a lower strap means (eg, a neck-strap) using anchor means (eg, hook-like protrusions) on the ends of the muffler tube and rings or the like on the ends of the strap. Upper strap means (eg, a pate harness) can be used to hold the forehead portion of the mask to a patient's head by attachment to attachment means (eg, hooks or holes) in the mask. To retain the shape of the mask and provide support for the attachment means, a relatively stiff reinforcing plate may be incorporated in the forehead portion of the mask, extending down the sides of the nose portion if desired.

In one form, the mask may be formed by an inner layer and an outer layer of moldable plastic sheet-like material that together define the forehead and nose portions of the mask, along with the air inlet passage, the plenum chamber and/or the exhaust means. Preferably, the inner layer is contoured to the face of the individual patient so that it will fit snugly and comfortably thereon and so that it isolates the patient's face from the supplied air so that the mask does not tend to lift off the face by the pressure of that air.

From another aspect, the invention comprises a respiratory mask suitable for use in the treatment of sleep apnea, which has a nose portion adapted to fit over the nose of a patient, a forehead portion adapted to rest on the forehead of the patient above the nose portion, and a nostril portion adapted to rest on or near the upper lip of the patient. An upwardly facing air inlet located adjacent the forehead portion is connected by an air passage to the nostril portion. The nostril portion preferably has air exhaust means adapted to exhaust excess inlet air and exhaled air laterally from either side of the nostril portion when the mask is in use. The exhaust means may comprise a transversely arranged tubular muffler spaced approximately in front of the patient's upper lip, which is adapted to exhaust air to the atmosphere through one or both ends. The muffler preferably has one or more restriction orifices by which air is received from and/or delivered to the nostrils of the patient and and/or one or more formaminous diffuser tubes, discs or plugs through which the exhaust air flows to the atmosphere so as to silence and/or disperse exhaust air flow from the muffler. Preferably, air is exhausted from both ends of the muffler to the atmosphere so that, when one end of the muffler is blocked - as when one side of the patients' face is pressed against a pillow, air can still be exhausted from the other end.

From another aspect, the invention comprises a respiratory facemask having a sheet-like inner layer molded to the facial contour of the patient, and a sheet-like outer layer affixed to the inner layer so as to define an air passage therebetween from a central air inlet located above the nose to the nostrils of the patient.

DESCRIPTION OF EXAMPLES Having portrayed the nature of the present invention, particular examples will now be described with reference to the accompanying drawings. However, those skilled in the art will appreciate that many variations and modifications can be made to the examples without departing from the scope of the invention as outlined above. In the accompanying drawings:

Brief Description of the Drawings

FIGURE 1 is a perspective view of the respiratory facemask of the first example fitted to the face of a sleeping patient and connected to an air supply hose.

FIGURE 2 is a front elevation of the respiratory facemask of the first example fitted to a standing patient's face, but without connection to an air supply hose.

FIGURE 3 is a front elevation of the mask of the first example.

FIGURE 4 is a side elevation of the mask of the first example.

FIGURE 5 is a bottom end elevation of the mask of the first example.

FIGURE 6 is an exploded view of the mask of the first example.

FIGURE 7 is a longitudinal section of the mask of the first example taken on section line 7 - 7 of Figure 3.

FIGURE 8 is rear elevation of the mask of the first example. FIGURE 9 is a side elevation of the core molding of the muffler assembly of the first example.

FIGURE 10 is an end elevation of the core molding of Figure 9.

FIGURE 11 is a partial section of the muffler assembly of the first example.

FIGURES 12(a) and 12(b) are respectively a sectional side and a sectional end elevation of the core end cap employed in the muffler assembly of Figure 11.

FIGURE 13 is a partial section of a first variant of the muffler assembly of the first example.

FIGURES 14(a) and 14(b) are respectively a sectional side and a sectional end elevation of the core end cap employed in the muffler assembly of Figure 13.

FIGURE 15 is a partial section of a second variant of the muffler assembly of the first example.

FIGURES 16(a) and 16(b) are respectively a sectional side and a sectional end elevation of the core end cap employed in the muffler assembly of Figure 15.

FIGURE 17 is a perspective view of the respiratory facemask of the second example fitted to the face of a sleeping patient and connected to an air supply hose.

FIGURE 18 is a front elevation of the mask of the second example.

FIGURE 19 is a side elevation of the mask of the second example

FIGURE 20 is a bottom end elevation of the mask of the second example. FIGURE 21 is an external side elevation of the core molding of the muffler assembly of the second example.

FIGURE 22 is an end elevation of the core molding of Figure 21.

FIGURE 23 is a sectional side elevation of the core molding of Figure 21 taken on section line 23 - 23 of Figure 22, showing the diffusers fitted therein.

FIGURE 24 is an end elevation of the sectioned core molding of Figure 23.

FIGURE 25 is a sectional side elevation of a first variant of the core molding of the muffler of the second example showing an alternative arrangement of diffusers therein.

FIGURE 26 is an end elevation of the sectioned core molding of Figure 25.

FIGURE 27 is a sectional side elevation of a second variant of the core molding of the muffler of the second example showing an different arrangement of diffusers therein.

FIGURE 28 is an end elevation of the sectioned core molding of Figure 27.

FIGURE 29 is a front elevation of the third example of a mask formed in accordance with this invention.

FIGURE 30 is a side elevation of the mask of the third example.

FIGURE 31 is a bottom end elevation of the mask of the third example.

FIGURE 32 is a side elevation of one half of the core molding of the muffler assembly of the third example.

FIGURE 33 is an end elevation of the half core molding of Figure 32. FIGURE 34 is a part sectional side elevation of the muffler assembly of the third example.

FIGURE 35 is a part sectional side elevation of a variant of the muffler assembly of the third example.

FIGURE 36 is a side elevation of a removable hooked screw-in end cap of the muffler assembly of the third example.

FIGURE 37 is a front elevation of a mask comprising the fourth example.

FIGURE 38 is a side elevation of the mask of Figure 37.

FIGURE 39 is a bottom end elevation of the mask of Figure 37.

FIGURE 40 is a diagrammatic front elevation of the mask comprising the fifth example.

FIGURE 41 is a front elevation of an elongated blank reinforcing plate suitable for use in the mask of the fourth example.

FIGURE 42 is a sectional elevation of the blank plate of Figure 41 , the section being taken on section plane 42 - 42 of Figure 41.

FIGURE 43 is a front elevation of a reinforcing plate suitable for use in the masks of the first, second, third and fifth examples.

FIGURE 44 is sectional elevation of the plate of Figure 43 taken on section plane 44 - 44 of Figure 43.

FIGURE 45 is a front elevation of a metal ring used on the end of the neck strap of the first example.

FIGURE 46 is a side elevation of the metal ring of Figure 45. FIGURE 47 is a front elevation of a metal ring used on the end of the neck strap of the second example.

FIGURE 48 is a side elevation of the metal ring of Figure 47.

FIGURE 49 is a front elevation of a metal buckle with double hooks ring used on the pate harness of the first example.

FIGURE 50 is a side elevation of the metal buckle of Figure 49.

FIGURE 51 is a front elevation of a metal buckle ring used on the pate harness of the second example.

FIGURE 52 is a side elevation of the metal buckle ring of Figure 51.

FIGURE 53 is an exploded perspective view of the principal components of the mask comprising the sixth example.

FIGURE 54 is a side sectional elevation of the mask of the assembled mask of the sixth example take on a plane equivalent to that indicated at 7 - 7 in Figure 3 for the first example.

FIGURE 55 is a front elevations of a blank reinforcing plate used in the mask of the sixth example.

Figure 56 is a sectional side elevation of the blank plate of Figure 55 taken on section plane 56 - 56 of Figure 55.

Example 1 The facemask 10 of the first example is illustrated in Figures 1 - 16, 43 -46, 49 and 50, together with associated parts and variants. It is shown fitted to the head of a patient 12 shown reclining in Figure 1 and upright in Figure 2, patient 12 being absent in the other Figures relating to this example. The terms 'upper' and 'lower' will be used assuming an upright patient and the terms 'inner' and 'outer' refer to portions of the mask that are closer to or more remote from the patient's face.

Mask 10 and is conveniently shaped or molded from relatively soft and pliable silicone plastic sheet material by techniques known in the plastics art. It basically comprises an inner layer 14 [see also Fig. 6], which is preferably molded to match the contours of the individual patient's forehead, nose, upper-lip and the portions of the cheeks adjacent to the nose, and an outer layer 16 [see also Fig. 6] bonded to the periphery of inner layer 14 and molded to form other features of the mask. The two layers form a forehead portion 18 resting against the forehead of patient 12, an upwardly pointing tubular air inlet socket 20 disposed adjacent but spaced outwardly from forehead portion 18, a central nose portion 22 that covers the nose of patient 12, a lower nostril portion 24 adjacent the upper lip of patient 12, and, a bifurcated air passage 26 that extends from air inlet 20 to nostril portion 24 on each side of nose portion 22. A flexible air supply hose 28 is coupled to inlet socket 20 by a snap-in connector 29 so that air under pressure can be conveyed through passage 26 into the nostrils of patient 12 from nostril portion 24. Overflow inlet air along with exhaled air is then exhausted to atmosphere from nostril portion 24 through diffuser plugs 30 fitted into the open ends 32 of a transverse tubular muffler assembly 34 located adjacent (but spaced outwardly from) the patient's lower lip. Thus, in this example, the exhaust means comprises muffler assembly 34 and diffuser plugs 30.

As will be best seen from Figures 1 and 2, mask 10 is attached to the head of patient 12 by (i) lower strap means comprising a simple adjustable neck-strap 36 having metal end-rings 38 that are engaged with anchor means - in this case, hooks 40 - formed on ends 32 of muffler assembly 34 and by (ii) upper strap means comprising an adjustable pate harness 41 of generally conventional design fitted at the front with a double-hooked metal loop 42 that engages attachment means on forehead portion 18 of mask 10 - in this case downwardly facing hooks or protrusions 44 molded integrally into forehead portion 18. An end ring 38 of neck-strap 36 is shown in Figures 45 and 46 and the double-hooked loop 42 of pate harness 41 is shown in Figures 49 and 50. Mask 10, removed from patient 12, connector 29 and air hose 28 and from neck- strap 36 and pate harness 41 , is illustrated in more detail in Figures 3 - 5. It will be seen from Figures 4 and 5 that inner layer 14 is molded to the shape of the patients' forehead, nose, cheeks and upper lip so that it fits snugly and comfortably thereon and that the periphery of outer layer 16 is shaped to conform to the periphery of inner layer 14, the peripheries of the two layers being bonded together by heat and/or adhesive. The way in which nose portion 22 of outer layer 16 protrudes through and between the two halves 26a and 26b of bifurcated passage 26 will also be evident from Figures 4 and 5, as is the manner in which bifurcated air passage 26 extends from air inlet socket 20 to nostril portion 24. In this example, air inlet socket 20 and passage 26 are molded from outer layer 16 so that socket 20 and upper part of passage 26 are supported from forehead portion 18 by an integral web 48. Outer layer 16 is also molded to encompass muffler assembly 34 and to support it by a transverse arched web 50 off a part 52 of nose portion 24 that fits over the upper lip of the patient.

Because the material of the inner and outer mask layers (14 and 16) is relatively soft and pliable, forehead portion 18 is preferably reinforced to provide stiffness in the region of the brow-ridge and nose-bridge generally indicated at 53 in Figure 4 and, particularly, to support downwardly facing attachment hooks 44. This is achieved by encapsulating an appropriately shaped stiff plastic or metal reinforcing plate 54 between inner layer 14 and outer layer 16 in forehead portion 18 and brow-ridge 53. This plate is shown in broken lines in Figures 3, 4 and 8, in section in Figure 7 and as a flat blank before shaping to contour n Figures 43 and 44, but it is not shown in the exploded view of Figure 6. Plate 54 has a downwardly projecting hook 56 on each side that is thinly covered by outer layer 16 of forehead portion 18 to form attachment hook 44 (see Figures 3 and 4) and has a bifurcated lower portion forming short side arms 57 that extend down either side of brow- ridge and nose-bridge portion 53 . Depressions or holes 58 are also formed in reinforcing plate 54 to more securely locate it between layers 14 and 16.

Figure 6 is an exploded perspective view showing inner layer 14 and outer layer 16 just prior to assembly and after (i) inner layer has been shaped to the face of patient 12 over a positive face mold [not shown], (ii) outer layer 16 has been shaped and fabricated to form inlet socket 20, passage 26, supporting webs 48 and 50, and muffler assembly 34 with anchor hooks 40, and (iii) the periphery of outer layer 16 has been shaped to conform with that of inner layer 14. Inner layer 14 thus has a central nose molding 60 that is shaped to the nose of patient 12 and that fits within a nose bulge 62 of outer layer 16 that protrudes between sub- passages 26a and 26b of bifurcated air passage 26. Nose molding 60 includes a pair of nostril openings 64 that include short, thin and flexible hollow tube-like protrusions 66 that fit snugly into the nostril openings of patient 12. Protrusions 66 are just visible in Figure 5 but more clearly shown in the section view of Figure 7 and in the underside view of mask 10 in Figure 8.

As best seen from the longitudinal section view of mask 10 shown in Figure 7, a plenum chamber 70 is formed immediately below nostril openings 64 between inner 14 and outer layer 16 in the nostril portion 24 of mask 10. It is into chamber 70 that air from air passages 26a and 26b is discharged and from that chamber that air is fed into the nostril openings 64 of the mask when it is in use. Overflow air from chamber 70, along with air that is exhaled through nostril openings 64 into chamber 70, is exhausted from chamber 70 through a central orifice 71 (Figure 7) through diffuser plugs 30 the ends of muffler assembly 34.

Though only one orifice 71 is employed in this example, it will be appreciated that more than one orifice can be used and, indeed, that the area of the orifice(s) can be such that the plenum chamber is effectively combined or contiguous with the interior of muffler 34. It will also be appreciated that, given sufficient orifice area, air passage 26 can be arranged to discharge into the muffler rather than into the plenum chamber and from thence into the muffler. Example 6, described below offers such an alternative.

Muffler assembly 34, together with two variants - muffler assemblies 34a and 34b - will now be described with reference to Figures 9 - 16, all being based upon a pre-molded core 72 comprising a transverse open-ended core tube 74 with a supporting core web 76, core 72 being incorporated into the mask between layers 14 and 16, with layer 16 substantially surrounding the outer and lower portion of core 72 to form the outer surface of muffler assembly 34 and external supporting web 50. Figures 9 - 12 illustrate assembly 34, which has hollow tubular sintered metal diffuser plugs 30 protruding from each end 32, which are retained in place by end caps 78 molded from hard plastic, end caps 78 being shaped to form core hooks 80. The arrangement is such that core 72 and end caps 78 are held in place by outer layer 16 that is wrapped there-around to form the exterior of muffler assembly 34 and anchor means / hooks 40. In this example, an additional hollow tubular diffuser plug 82 is pushed into each end of core tube 74 inwards of the respective protruding diffuser plug 30. The central orifice 71 is formed in the upper wall of core tube 74 to admit exhaust air from plenum chamber 70. The combination of orifice 71 and diffuser plugs 30 and 82 act to significantly attenuate the noise of air flow from muffler assembly 34, protruding diffuser plugs 30 also serving to spread the exhausting air stream so that air currents from the exhausted air are minimized.

The first variant of the muffler assembly, indicated at 34a in Figures 13 and 14, differs from that of Figures 9 - 12 in that diffuser plugs 30 and 80, along with plastic end caps 78, are replaced by formaminous cap-plugs 86 that combine the function of the plastic caps 78 and protruding diffuser plugs 30, core hooks 80a being formed integrally on cap-plugs 86. As before, outer layer 16 bonds and integrates the molded core 72 and cap-plugs 86 into the muffler assembly 34a and nose portion 24 of mask 10.

The second variant of the muffler assembly, indicated at 34b in Figures 15 and 16, differs from that of Figures 9 - 12 in that no internal diffuser plugs are used and in that modified end caps 78b are used into which modified protruding diffuser plugs 30b are pressed. Another modification is that a series of slots 88 is formed in the upper wall of core tube 74 in place of central orifice 71. Again, slots 88 and diffuser plugs 30b serve to both silence exhaust air flow through muffler 34 and to minimize air currents emerging there-from around the sides of mask 10.

Example 2

The second example, also with some variants in the diffuser assembly, will now be described with reference to Figures 17 - 28. As the mask of the second example is the same in many respects as that of the first example, reference numbers in the drawings that indicate parts of the mask of the second example that are essentially the same - or which have essentially the same function - as those of the first example, will include the same digits as in the first example preceded by the numeral '2'. Thus, the mask of the second example is indicated at 210 and will not be described in detail since reference can be made to the description of the mask of the first example.

The primary difference between mask 210 and mask 10 is in the design and construction of the muffler assembly 234. Instead of hook like anchor means (40 in the first example) the exterior of each end of muffler assembly has an annular groove 240 to take bent wire loops 238 of neck strap 236 shown in Figures 47 and 48. Grooves 240 give the interior of the ends of muffler 234 an undulating form that is used to locate internal elements, as illustrated in more detail in Figures 23 - 28. As before, outer layer 216 is wrapped around a pre-molded core assembly 272, comprising a core tube 274 and a supporting web 276, to incorporate core 272 into the nostril portion 224 of mask 210.

Core assembly 272, shown in Figures 21 - 28, is assembled from two longitudinally divided halves 272a and 272b that are bonded together to form core tube 274 and web 276 and to enclose an inner disk 289a and an outer diffuser disc 289b on respective sides of each groove 240 at each end of tube 274. Also enclosed in tube 274 is a central diffuser bypass tube 290 that is located at each end by inner discs 289a so that exhaust air flowing into diffuser tube 290 effectively bypasses inner discs 289a. Inner discs 289a are preferably made of impermeable material, though they can also be air-permeable. Discs 289a and 289b assist in the alignment of the two halves 272a and 272b of core assembly 272 and in preventing grooves 240 from collapsing or being distorted by rings 238 of neck strap 236. Alignment of the two halves 272a and 272b is also facilitated by dowel pins 291. As in the muffler of the first example, exhaust air from the plenum chamber is admitted into core tube 274 by a central orifice 271 or, if desired, by a series of slots like slots 88 shown in Figure 15.

In the variant muffler core assembly 272a shown in section in Figures 23 and 24, inner and outer diffuser discs 289a and 289b and diffuser bypass tube 290 of the muffler core assembly 272 described above are replaced by thick externally grooved diffuser end plugs 292 that provide solid support for external grooves 240 and permit the passage of air through fine holes or passages. As before, end plugs 292 may be formed from formaminous plastic, metal or ceramic material.

In the variant muffler 234b shown in Figures 27 and 28, flanged closed-end sintered diffuser tubes 230a are employed and project from the open ends 232 in a similar manner to diffuser plugs 30 of muffler assembly 34 of the first example. In this case, however, the large flanges 230' of tubes 230a hold plugs 30 in place. A pair of similar flanged diffuser tubes 230b (indicated by broken lines) can be located inwards of external grooves 240, tubes 230a and 230b thus providing structural reinforcement for grooves 240.

Example 3 The third example with some variations is shown in Figures 29 - 36 and Figures 51 and 52. It comprises a respiratory facemask 310 for the treatment of sleep apnea that is in many respects the same as Example 1. Accordingly parts that are essentially the same, or that have essentially the same function, as those of Example 1 will be given the same reference numbers preceded by '3' and only the differences between masks 10 and 310 will be described. The primary differences between mask 310 and mask 10 lie in the design and construction of the upper attachment means for the pate harness (not shown) and in the design of the muffler assembly 334.

Instead of using downwardly facing hooks 44 on forehead portion 18 (as in

Example 1), mask 310 employs a hole 393 in the web 348 that supports air inlet socket 320 for bifurcated air passage 326. Hole 393 is engaged by a wire buckle 394, shown in Figures 51 and 52, attached to pate harness 41 of Example 1 instead of buckle 42 of that example. Buckle 294 has a split lower loop 394a that can be parted and twisted to enter both halves into hole 393 and thus provide a secure attachment for the pate harness.

The muffler assembly 334 of the third example is shown in Figures 32 - 34 and 36, along with a minor variant shown in Figure 35. As in previous examples, a pre- formed core assembly 372 is molded and bonded into the nostril portion 324 by outer layer 316 so that it is in fluid-flow connection with the plenum chamber (not depicted in this example) by way of one or more orifices. As in the second example, core assembly 372 is formed in two longitudinal halves, one of which - 372a - is shown in Figures 32 and 33, each half forming half 374a of core tube 374 and half 376a of core web 376. Instead of a central orifice, a number of vertical orifice slots 371a (Figures 32 and 34) are employed to exhaust air from the plenum chamber (not shown).

The ends of core tube half 374a are molded with coarse female screw threads 395 so that, when tube 374 is assembled, screw-threaded tubular end plugs or caps 396, each incorporating a diffuser plug 330, may be screwed into place. One such cap 396 is shown in side elevation in Figure 36. In muffler assembly 334 (show in part section in Figure 34), each diffuser element 330 is a hollow cone that is retained in the bore of the respective cap 395 by friction or by a snap-fit. It will be noted that screw caps 395 form hook-like anchor means 340 adapted to be engaged by a neck strap and attachment loops such as those shown in Example 1. Variant muffler assembly 334a (shown in part section in Figure 35) differs from that of assembly 334 of Figures 32 - 34 in that the tubular screw-threaded end caps 396 are fitted with alternative diffuser means comprising a snap-on external hemispherical diffuser shell 330a and a push-in internal diffuser disc 330b.

Example 4

The fourth example of the application of the principles of the present invention is a sleep apnea respiratory facemask 410 illustrated in Figures 37 - 39 and Figures 41 and 42. Mask 410 will not be described in detail but the same reference numerals - with the prefix numeral '4' added - as used for the mask of Example 1 will be applied to indicate parts with the same or similar form and function in mask 410. Reference may then be made to the description of Example 1. In Figure 38, the facial profile of a patient 412 wearing the mask is shown in dash-dot broken lines. Mask 410 differs from mask 10 primarily in (i) the use of an air inlet tube 426 that is not bifurcated, (ii) the shape of reinforcing plate 454 and (iii) in the provision of a secondary exhaust outlet or diffuser plug 496 in the bottom muffler assembly 434.

As in Example 1 , air inlet tube 426 is molded from outer layer 416, along with the outer parts of forehead portion 418, nose portion 422 and nostril portion 424. However, tube 426 passes over and around the nose bulge 462. This makes tube easier to form in outer layer 416 but raises the profile of the mask somewhat, as will be seen from the side elevation of Figure 38 and the bottom elevation of Figure 39. As before, air from tube 426 is exhausted centrally into the plenum chamber (not shown) formed by the inner and outer layers 414 and 416 just above muffler assembly 434 and just below the nostril openings (not shown).

In this example, reinforcing plate 454 is bifurcated so that one arm 454a extends right along one side of the nose portion 324 and the other arm 454b extends right down the other side of nose portion 324. This additional strengthening of the nose portion compensates for additional distorting forces that may result from a mask with a higher profile. Reinforcing plate 454 is shown in Figures 41 and 42 as a flat blank prior to being shaped to suit the particular profile of a patient's face. As in Example 1 , depressions or holes 458 are formed on the top part of plate 454 to assist in securely locating it in place when it is pressed between inner and outer layers 414 and 416. In addition, plate 454 includes extra holes or depressions 458a in each side arm 454a and 454b that serve the same function - but in the nose portion 424 rather than in the forehead portion 418.

Secondary exhaust outlet or diffuser plug 496 is, as already mentioned, located centrally in the bottom wall of muffler assembly 434 so as to spread air exhausted there-from downwardly. Although not preferred, two or more diffuser plugs could be used instead of end diffusers 430, it being preferred to use diffuser 496 to supplement exhaust outlet diffusers 430.

Example 5

The respiratory facemask 510 of the fifth example, shown in front elevation in

Figure 40, is similar in some respects to the facemask of my above-noted prior patent in that it is intended to cover almost the entire face of the patient, having eye holes 511. Indeed, the mask may extend downward over the chin of the patient, as indicated by broken lines 515, and a mouth hole 519 may be provided (also indicated in broken lines). As in Example 1 , a bifurcated air passage 526 leads air from an inlet socket 520 supported by a web 548 from the forehead portion 518 of mask 510 and a reinforcing plate 554 of similar design to than in Example 1 is employed to stiffen the area around the patient's brow ridge and upper nose. Plate 554 provides support for similar downwardly facing hooks 544 to form attachment means for the pate harness (not shown) as in the first example. As before, diffuser plugs 530 are fitted into the open ends of the muffler assembly and hook like protrusions 540 are provided on each end of the muffler assembly 534 to form the anchor means for the lower harness or neck strap (not shown in Figure 40).

While respiratory mask 510 can be formed in many different ways, it has been found convenient and preferable to use moldable silicon rubber sheets in two layers to form the air passage, plenum chamber and muffler as previously described. Example 6 As the mask 610 of this Example is similar in external appearance and function - but of different fabrication - to mask 10 of Example 1 , external views of mask 610 have not been provided. Figures 53 - 56 illustrate the manner of construction of mask 610. As noted previously, this example differs from the preceding examples in that air from the air passage is discharged into the muffler rather than the plenum chamber. There are also other important differences between this example and the foregoing.

As before, mask 610 has an inner layer 614 and an outer layer 616 but, in this case, a separately molded bifurcated tube assembly 617 is encased between layers 614 and 616 when they are bonded together around their peripheries. Tube assembly 617 is conveniently molded as separate outer and inner halves 617a and 617b so as to integrally include the transverse core tube halves 619a and 619b of core tube of a muffler assembly like that of Example 1. Thus, in this example, inlet air flowing from passage 626 in insert 617 enters the muffler tube 619a / 619b) rather than the plenum chamber 670. Because of this, it is necessary to ensure free exchange of air between the plenum chamber and the muffler tube so that carbon dioxide from exhaled air does not accumulate in the plenum chamber. Half of a large central slot-like orifice 671 is shown in outer half core tube 619b, the other half being formed in core tube half 619a. Indeed, as previously indicated, orifice slot 671 may be so large that the plenum chamber and the interior of the muffler core tube are effectively combined.

It will be appreciated that muffler assembly 634 can incorporate any of the diffuser variations discussed above, though those skilled in the art will appreciated that the lateral dimension of orifice slot 671 should not be so great as to straddle any of the circular section diffuser discs or plugs. Again, in this example, the core tube 619a / 619b of the muffler 634 is incorporated into the mask by wrapping top layer 616 around it as previously described with respect to Example 1. Such wrapping thus forms the exterior of muffler assembly 634 with its open ends 632 and supporting web 650, after insertion of desired diffuser plugs 630.

As in Example 1 , inner layer 614 is molded to the face of the patient, has a nose molding 660 that fits within the nose bulge 662 of outer layer 616, nostril openings 664 and tube-like protrusions 666. Tube assembly 617 fits onto inner layer 614 so as to encircle nose molding 660 at its lower end and so that muffler core tube 619 (when assembled) is spaced a little below nostril openings 664. When outer layer 616 is fitted over inner layer 614, a plenum chamber 670 is formed immediately below and in communication with nostril openings 664. As noted, this chamber receives air from the air inlet tube 617, delivers it to nostril openings 664 and exhausts overflow air along with air exhaled from the nostril openings into the muffler assembly

In mask 610 of Example 6, a reinforcing plate 654 (show in section in Figure 54 and in blank form in Figures 55 and 56) is employed that is similar to plate 54 of Example 1 , except for the important addition of an upstanding tenon 623 on the outer face of plate 654 that has a transverse alignment hole 625 formed in it. A coacting channel 627 for tenon 623 is formed on the inside face of the upper end of lower half 617b of air core-tube 617 between two parallel protrusions 629 on that face. Alignment holes 631 are formed in protrusions 629 for alignment with hole 625 on tenon 623. Figure 54 shows the assembled respiratory mask in section, it being noted that the sides of outer layer 616 are brought together around upper portion of air core-tube 617 to form a supporting web 648 and to encapsulate reinforcing plate 654 between layers 614 and 616. Alignment holes 625 and 631 are made to extend through web 648 and form the attachment means for the pate harness, as described in Example 3.

While six examples of different masks formed in accordance with the invention have been described and many variations and combinations thereto indicated, it will be appreciated by those skilled in the art that many other examples and variants can be devised without departing from the scope of the invention as defined by the following claims. For example, it will be readily understood that the non-bifurcated inlet passage (426) of the fourth example can be readily molded as a separate insert an incorporated between the layers of the mask in the same way as described for the bifurcated tube insert (617) of the sixth example.

Claims

1. A respiratory face mask suitable for the treatment of sleep apnea having a nose portion adapted to fit over the nose of a patient, a forehead portion adapted to rest on the forehead of the patient above the nose and a nostril portion adapted to rest on the upper lip of the patient below the patient's nostrils when the mask is worn by the patient, the mask having an upwardly facing air inlet adjacent the forehead portion, an air passage arranged to convey air supplied under pressure from the inlet to the nostril portion, and air exhaust means forming part of the nostril portion of the mask and adapted to exhaust air there-from to atmosphere during use of the mask.

2. A respiratory face mask according to claim 1 wherein said passage is formed so that air flowing from the air inlet to the nostril portion does not contact the skin of the patient's face and, therefore, does not tend to lift the mask off the face of the patient's face.

3. A respiratory face mask according to claim 1 or claim 2 wherein said air exhaust means is adapted to exhaust air laterally from at least one side of the nostril portion of the mask, when the mask is in use.

4. A respiratory face mask according to claim 1 or 2 wherein: the nostril portion of the mask defines a plenum chamber adapted for location immediately in front of the nostrils of a patient when the mask is worn by the patient, said plenum chamber has air outlet means adapted to direct air from the plenum chamber into the nostrils of a patient wearing the mask, said air passage is adapted to convey air from the inlet to said plenum chamber either directly or via the exhaust means, and said exhaust means is adapted to exhaust air from said plenum chamber along with overflow air from the air passage.

5. A respiratory face mask according to claim 4 wherein said passage is bifurcated by the nose portion so that a first sub-passage lies on one side of the nose portion connecting the air inlet to the plenum chamber and so that a second sub-passage lies on the other side of the nose portion also connecting the air inlet to the plenum chamber.

6. A respiratory face mask according to claim 4 or 5 wherein said air outlet means of the plenum chamber comprise a pair of thin, flexible and hollow air outlet protrusions, each of said protrusions being adapted to fit into a corresponding nostril of a patient wearing the mask so that air supplied to the plenum chamber under pressure is fed into the nostrils of the patient without contacting the exterior of the nose of the patient.

7. A respiratory face mask according to any preceding claim wherein: said air exhaust means includes an exhaust opening on each side of the nostril portion adapted to exhaust air from the nostril portion of the mask to atmosphere, and diffuser means is included in the exhaust means for diffusing air flowing from the exhaust means and/or for attenuating the noise of air flow from the exhaust means.

8. A respiratory face mask according to any one of claims 1 - 6 wherein: said air exhaust means comprises a transversely arranged tubular muffler assembly located adjacent but in spaced relation to a patient's upper lip when the mask is being worn by the patient, said muffler assembly having first and second ends laterally disposed with respect to the nose portion of the mask, said muffler assembly has an opening in each end thereof adapted to exhaust air from the nostril portion of the mask to atmosphere through said muffler assembly, and said muffler assembly includes formaminous diffuser means arranged so that exhaust air will flow there-through, said diffuser means being adapted to diffuse air flowing from the exhaust means and/or to attenuate the noise of air flow from the exhaust means.

9. A respiratory face mask according to any one of claims 1 - 6 wherein: said air exhaust means comprises a transversely arranged tubular muffler assembly located adjacent but in spaced relation to a patient's upper lip when the mask is being worn by the patient, said muffler assembly having first and second ends laterally disposed with respect to the nose portion of the mask, said muffler assembly having an opening in each end thereof adapted to exhaust air from the nostril portion of the mask to atmosphere through said muffler assembly, and said muffler assembly including orifice means between said muffler assembly and said plenum chamber permitting air flow between the plenum chamber and the muffler assembly.

10. A respiratory face mask according to claim 9 wherein: said muffler assembly includes formaminous diffuser means arranged so that exhaust air will flow there-through, said diffuser means being adapted to diffuse air flowing from the exhaust means and/or to attenuate the noise of air flow from the exhaust means.

1 1.A respiratory face mask according to claim 9 or 10 wherein: said orifice means is at least one hole in the wall of the tubular muffler assembly connecting said the interior of said muffler assembly and the plenum chamber for conveying exhaust air flow from the plenum chamber into the muffler assembly and/or air from the air passage to the plenum chamber.

12. A respiratory face mask according to claim 9 or 10 wherein: said orifice means comprises a series of transverse slots in the wall of the tubular muffler assembly for conveying exhaust air flow from the plenum chamber into the muffler assembly.

13. A respiratory face mask according to claim 9 or 10 wherein: said orifice means comprises a series of axial slots in the wall of the tubular muffler assembly for conveying exhaust air flow from the plenum chamber into the muffler assembly.

14. A respiratory face mask according to claim 9 or 10 wherein: said air passage is connected to discharge air into the muffler means, and said orifice means comprises an opening between the plenum chamber and the muffler means to permit free exchange of air there-etween

15. A respiratory face mask according to any one of claims 8 - 14 wherein said diffuser means comprises a formaminous air-permeable plug in each end opening of said muffler assembly.

16. A respiratory face mask according to claim 15 wherein said diffuser plug is a first hollow tube with a closed end that extends from the respective end of the muffler assembly.

17. A respiratory face mask according to claim 16 wherein each of said diffuser plugs includes a second hollow tube with a closed end, said second tube being located within the muffler means with its open end adjacent to the open end of the first hollow tube.

18. A respiratory face mask according to claim 15 wherein said diffuser plug is a first disc located in each end opening of said muffler assembly.

19. A respiratory face mask according to claim 15 wherein said diffuser plug is a second disc located in each end opening of said muffler assembly in axial spaced relation to said first disc.

20. A respiratory face mask according to any one of claims 8 - 13 wherein said diffuser means is a formaminous tube arranged substantially coaxially within the tubular muffler assembly so that exhaust air entering the muffler assembly from the plenum chamber passes through the wall of said formaminous tube before being exhausted from the muffler assembly.

21 .A respiratory face mask according to claim 20 wherein said formaminous tube is held in place in the center of a pair of spaced annular discs, each disc being arranged near a respective end of the tubular muffler assembly.

22. A respiratory face mask according to claim 21 wherein each of said annular discs is formed from formaminous material that is air-permeable.

23. A respiratory face mask according to claim 22 wherein each of said annular discs is formed from material that is not air-permeable.

24. A respiratory face mask according to claim 23 wherein a second disc that is formaminous and air permeable is arranged within the tubular muffler assembly between each of said annular non air-permeable discs and the respective end of the muffler assembly.

25.A respiratory face mask according to any one of claims 8 to 24 wherein: lower strap means, having first and second ends, is provided for holding the nostril portion of the mask in position adjacent the upper lip of a patient wearing the mask, and anchor means is formed on each end of the tubular muffler assembly for anchoring a respective one of said ends of said first strap means.

26. A respiratory face mask according to claim 25 wherein: said lower strap means is a neck strap having two ends, each end of the neck strap is fitted with a loop adapted to engage said anchor means, said anchor means comprises a hook or groove formed on or in the respective end of the tubular muffler assembly.

27. A respiratory face mask according to any preceding claim wherein: upper strap means is provided for holding the forehead portion of the mask in position against the forehead of a patient wearing the mask, and attachment means is formed on the forehead portion for attachment of a respective one of said ends of the upper strap means.

28. A respiratory face mask according to claim 27 wherein: the forehead portion has first and second sides, said attachment means comprises a downwardly facing hook on each side of said forehead portion, and each of said upper strap means is attached to a wire buckle having ends adapted to engage said hooks.

29. A respiratory face mask according to claim 27 wherein: said attachment means comprises a web outstanding from the forehead portion and a hole formed in said web, and each end of said upper strap means is attached to a wire buckle having hook means adapted to enter said hole and engage said web.

30. A respiratory face mask according to any preceding claim wherein: the mask incorporates a reinforcing plate extending from said forehead portion to said nose portion and adapted to resist relative distortion of said forehead and nose portions.

31.A respiratory face mask according to claim 28 wherein: the mask incorporates a reinforcing plate extending from said forehead portion to said nose portion and adapted to resist relative distortion of said forehead and nose portions, and. said plate includes said downwardly facing hooks or provides the cores thereof.

32. A respiratory face mask according to any one of claims 1 - 28 wherein: the mask incorporates a reinforcing plate extending from said forehead portion to said nose portion and adapted to resist relative distortion of said forehead and nose portions, and. said plate supporting a web connecting the air inlet and the forehead portion of the mask.

33. A respiratory face mask according to any one of claims 2 - 32 having: an inner layer adapted to conform to and rest against the forehead, nose, cheek areas adjacent the nose and the upper lip of a patient wearing the mask, and an outer layer fitting over and secured to said inner layer so as to enclose or form there-between said inlet passage and said plenum chamber.

34. A respiratory face mask according to claim 33 wherein said air inlet is formed between said inner and said outer layer in the region of the forehead portion of the mask.

35. A respiratory face mask according to claim 32 or 34 wherein a separate bifurcated tubular insert forms said air inlet and said air passage, said tubular insert being secured in place between and by said inner and outer layers.

36. A respiratory face mask according to claim 35 wherein said tubular insert also includes at least portion of said exhaust means.

37. A respiratory face mask according to 35 or 36 when read through claim 8, wherein said insert also forms said transverse tubular muffler and at least portion of said plenum chamber.

38. A respiratory face mask according to claim 35 or 36 when read through claim 29 wherein said reinforcing plate is encased between said inner and outer layers in an area extending from the forehead portion to the bridge of the nose when the mask is worn by a patient.

39. A respiratory face mask substantially in accordance with: Example 1 as described herein with reference to Figures 1 - 16 of the accompanying drawings with reference to Figures 43 - 46 and 49 - 50, Example 2 as described herein with reference to Figures 17 - 28 and 47 - 48 of the accompanying drawings, Example 3 as described herein with reference to Figures 29 - 36 and - 52,

Example 4 as described herein with reference to Figures 37 - 39 and - 42, Example 5 as described herein with reference to Figure 40, or

Example 6 as described herein with reference to Figures 53 - 56.