Abstract:
A gastro-laryngeal mask features softly compliant construction of the distal half of the mask, wherein the mask is of generally elliptical configuration, with an inflatable peripheral cuff to seal and support the mask around the laryngeal inlet. A back cushion is inflatable to engage the back wall of the pharynx and thus to forwardly load the peripheral-cuff seal to the laryngeal inlet. An evacuation tube for external removal of a possible gastric discharge completes an evacuation or discharge passage contained within the mask and opening through the distal end of the peripheral cuff. Special provision is made for assuring integrity of the discharge passage within the flexible distal half of the mask, i.e., assuring against collapse of the distal-end half of the softly compliant evacuation tube in the distal region of the mask, such that inflation of the mask does not compromise viability of the evacuation tube by compressing softly compliant material of the evacuation tube during periods of mask inflation. The special provision also favors such collapse of the mask when deflated as to provide a leading flexible edge for piloting a safe and correct advancing insertional advance of the deflated mask in the patient&#39;s throat, in avoidance of epiglottis interference and to the point of locating engagement in the upper sphincter of the oesophagus.

Description:
RELATED CASE 
     This application is a continuation of original application, Ser. No. 08/609,521, filed Mar. 1, 1996, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to a laryngeal-mask airway (LMA) device, which is an artificial airway device designed to facilitate lung ventilation in an unconscious patient by forming a low-pressure seal around the laryngeal inlet. An inflatable-ring seal surrounds an appropriately shaped mask which fits into the lower pharynx and is attached to a tube which emerges from the mouth, as for connection to medical gas-supply tubing. 
     More particularly, the invention relates to a variety of laryngeal masks, known as gastro-laryngeal masks (GLM), wherein. provision is made for airway assurance to the patient who is at. risk from vomiting or regurgitation of stomach contents while unconscious. U.S. Pat. No. 5,241,956 deals with this problem by providing an evacuation tube which is open through the center of the inflatable seal of the laryngeal mask, thus utilizing the distal end of the inflatable ring as an inflatable-cuff formation which establishes peripherally sealed engagement to the upper sphinctral region of the oesophagus and centrally supports the distal end of the evacuation tube. In addition, said U.S. Pat. No. 5,241,956 discloses a further inflatable cuff carried by the laryngeal mask and by the evacuation tube, for referencing inflation against the back wall of the pharynx, thus making it possible to establish the laryngeal-inlet seal with reduced inflation pressure, as compared with prior structures not having such an additional inflatable cuff. 
     U.S. Pat. No. 5,305,743 discloses moulding techniques for manufacture of a variety of laryngeal masks, including a gastro-laryngeal mask, wherein an inflatable back cushion provides such referencing inflation against the back wall of the pharynx as to widely distribute the back-wall reference, over substantially the full area of the laryngeal mask. Such a back-cushion construction has been found to be mechanically simple and highly effective, and U.S. Pat. No. 5,355,879 discloses such a back cushion for each of several representative laryngeal-mask constructions. 
     In practice, although a gastro-laryngeal-mask as described in said U.S. Pat. No. 5,355,879 works well, it has the disadvantage that the gastric evacuation channel needs to be sufficiently stiff to prevent its collapse under the influence of the increased pressure within the back-cushion cuff, when it is inflated in the pharynx. A suitably stiff tube is readily provided, but the whole device is then more difficult to insert into the patient&#39;s throat, since insertion involves flexing the device around the angle at the back of the tongue. Provision of a pre-curved airway tube facilitates passage around the back of the tongue, but the advancing distal tip end of the device is then more likely to collide with the glottis (or entrance to the larynx), and indeed it may block the larynx by so doing, with consequent danger to the patient. 
     BRIEF STATEMENT OF THE INVENTION 
     It is an object of the invention to provide an improved gastro-laryngeal mask. 
     A specific object is to meet the above object with a construction that specifically avoids problems or difficulties with constructions of said U.S. patents. 
     Another specific object is to provide for ready compression and flexure of a gastric passage within a back-cushioned or cuffed gastro-laryngeal mask, when the mask is in deflated condition for insertion into the patient&#39;s throat. 
     Furthermore, for the deflated condition of the mask, i.e., in readiness for insertion into the patient&#39;s throat, it is an object to enable formation of a flattened flexible leading distal-end edge to self-adapt to and resiliently ride the outer limit of curvature of the patient&#39;s airway, throughout the insertional course of the deflated mask and into its locating engagement with the hypopharynx. 
     It is a further specific object, in conjunction with the foregoing specific objects, to provide for assurance of full patency of the gastric passage within the mask, when the mask has been inflated. 
     These objects are realized in the present invention by utilizing two structural mechanisms, both of which are operative when the device is inflated; one of these mechanisms prevents lateral compression of the wall of the gastric tube, while the other of these mechanisms prevents antero-posterior compression of the wall of the gastric tube; the result is to assure a substantially circular section within relatively soft portions of the evacuation passage, as long as the device is inflated and in installed position. 
     In a preferred embodiment of the invention, an artificial airway device to facilitate a patient&#39;s lung ventilation comprises an airway tube, an evacuation tube, and a laryngeal mask at one end of both tubes. The mask is of generally elliptical configuration and comprises a body or backplate of relatively stiffly compliant nature, and an inflatable annular cuff or ring of relatively softly compliant nature is connected to and surrounds the body or backplate. When inflated, the annular cuff adapts to and seals around the laryngeal inlet, and an inflatable cushion on the exterior of the inflated annulus bears against the back wall of the pharynx, to thereby forwardly load the inflated annulus into sealed relation with the laryngeal inlet, with the backplate dividing the mask between a laryngeal-chamber side and a pharyngeal-chamber side. The relatively stiff backplate is formed for connection to the airway tube for exclusive communication to the larynx through an opening in the backplate; and the backplate is also configured to guide and support a relatively soft flexible evacuation tube within the pharyngeal-chamber side, from a distally open end for reception of gastric products, to a proximal end for connection to an externally discharging evacuation tube. 
     It is a feature of the invention that along an aligning path for the flexible evacuation tube within the pharyngeal-chamber side of the mask, a first significant angular fraction of the periphery of the flexible tube is bonded to a stabilizing portion of the backplate, and that a second angular fraction of the periphery of the flexible tube is continuously bonded to the inner surface of the flexible back cushion, such that generally opposite unbonded further angular regions exist between the bonded regions. These unbonded further regions are provided with external stiffening ribs at a succession of axial intervals, to reinforce the unbonded regions against lateral compression when the back cushion and the inflatable ring are under inflation pressure. In this way, inflation of the annular laryngeal-inlet sealing ring and of the flexible back cushion will assure a maximally open evacuation passage within the mask in inflated condition, essentially without antero-posterior or lateral compression of the passage. And it is further assured that upon deflation of the mask, evacuation-passage compression will be essentially in the sense of achieving a squeezing and somewhat flattening deformation of the discharge passage against the formed back-plate area of evacuation-passage support; such flattening is maximal at the oesophageal end of the discharge passage, so that, when correctly deflated, the device forms a wedge shape for correct insertion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be illustratively described in detail for a presently preferred embodiment, and for certain other embodiments, all in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a simplified view, generally in side elevation, for the presently preferred embodiment of an artificial airway device, having at its distal end a laryngeal mask with a gastric-drainage feature of the invention, the same being shown in position for use in a patient; 
         FIG. 2  is a fragmentary plan view, to an enlarged scale showing the back or pharynx-facing side of the mask of  FIG. 1 ; 
         FIG. 3  is a plan view to the scale of  FIG. 2 , showing a softly compliant moulded inflatable component of the mask, as seen from the aspect of  FIG. 2 ; 
         FIG. 4  is a plan view to the scale of  FIG. 2 , showing a relatively stiffly compliant rigidising or reinforcing back-plate component of the mask, as seen from the aspect of  FIG. 2 ; 
         FIG. 5  is a longitudinal section of the softly compliant component of  FIG. 3 , to the scale of  FIGS. 2  to  4  and taken generally in the vertical plane  5 — 5  of substantial symmetry, but prior to an inside-out deformation step, to create the appearance of  FIG. 3 ; 
         FIG. 5A  is a section, taken at  5 A- 5 A in  FIG. 5 ; 
         FIG. 6  is another view in longitudinal section, to the scale of  FIGS. 2  to  5  and in the vertical plane  5 — 5  of  FIG. 3 , showing the relatively stiff component of  FIG. 4  in assembled relation to the softly compliant component of  FIG. 3 ; 
         FIG. 7  is an end view, being a proximally directed view, of the distal end of the rigidising component of  FIG. 4 ; 
         FIG. 8  is a simplified cross-sectional view of the inflated mask of  FIG. 2 , taken at  8 — 8  in  FIG. 2 ; 
         FIG. 9  is a simplified cross-sectional view of the deflated mask of  FIG. 2 , taken at  8 — 8  in  FIG. 2 ; 
         FIG. 10  is a view similar to  FIG. 2 , to show a first modification; 
         FIG. 11  is a view similar to  FIG. 4 , to show the back-plate component in the modification of  FIG. 10 ; 
         FIG. 12  is a sectional view, taken at  12 — 12  in  FIG. 11 ; and 
         FIG. 13  is a plan view to the scale of  FIG. 2  to illustrate an intermediate product which is a modification of that shown in FIGS.  5  and  6 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring first to the preferred embodiments of  FIGS. 1  to  9 , the invention is shown in application to an airway system comprising a laryngeal-mask unit  10  and its airway tube  11 , installed through the mouth  12  of a patient. The mask unit  10  may be generally as described in any of the above-identified U.S. patents and therefore need not now be described in detail. It suffices to say that mask unit  10  comprises a relatively stiff body or backing-plate member, generally indicated at  13 , and an apertured relatively thin body-membrane portion or panel  13 ′ having an aperture or lumen  14  through which the airway tube  11  can establish a free externally accessible ventilation passage, via the patient&#39;s mouth  12  and throat  15 , and past the epiglottis  16  to the larynx  17 . The body member  13  of mask  10  may be described as generally dome-shaped, with its concave side terminating in a generally elliptical footing, and facing the laryngeal inlet; and its convex side faces the backwall of the pharynx. Body  13  is suitably of an elastomer such as silicone rubber and relatively stiff; and body member  13  is surrounded by an inflatable ring  18  which is generally elliptical and which is circumferentially united to body member  13  in essentially a single plane. The inflatable ring  18  may also be of silicone rubber, although preferably relatively soft and flexible compared to body member  13 . An externally accessible tube  19  is the means of supplying air to the inflatable ring  18  and of extracting air from (and therefore collapsing) ring  18  for purposes of insertion in or removal from the patient; check-valve means  21  in tube  19  will be understood to hold a given inflation or to hold a given deflation of ring  18 . 
     In the installed position of  FIG. 1 , the projecting but blunted distal end  27  of ring  18  is shaped to conform with the base of the hypopharynx where it has established limited entry into the upper sphinctral region of the oesophagus  24 . The back side of body member  13  is covered by a thin flexible panel  25  ( FIG. 2 ) which is peripherally bonded to the inflatable ring  18  ( FIG. 1 ) and in sealed engagement at peripheral line  25 ′ around the entrance of tubes  11  and  23  to the mask structure to define an inflatable back cushion which assures referencing to the back wall of the pharynx and thus is able to load the mask unit forward for enhanced effectiveness of inflated-ring sealing engagement to the laryngeal inlet. The inflated ring, thus-engaged to the laryngeal inlet, orients the distal-end of the airway tube  11  at an acute angle to the general plane of ring  18  and in substantial alignment with the axis of the laryngeal inlet, for direct airway communication only with the larynx  17 . 
     The laryngeal-mask unit  10  is of the GLM variety in which an evacuation tube  23  ( FIG. 2 ) serves for extraction and external removal of gastric-discharge products from the oesophagus. Tube  23  follows the general course of the airway tube  11 , with sealed entry alongside airway tube  11 , beneath the back-cushion panel  25 , and with passage through the interior of ring  18 , near the distal end of the mask; in  FIG. 3 , the distally open end of the evacuation tube  23  is defined by a re-entrant tubular conduit formation  26  integrally formed with the relatively soft material of ring  18 . As explained in U.S. Pat. No. 5,241,956, inflation-air supply to the back cushion may be the same ( 19 ) as for ring  18 , or separate inflating means (not shown) may be provided for these separate inflatable means. 
     More specifically, for the particular construction shown, the relatively softly compliant flexible components may be integrally formed in a single moulding operation, in which the moulded intermediate product is an inside-out version of what will become the finished more flexible part of the finished mask unit  10 . The moulded intermediate product may thus have the appearance shown in  FIG. 5 , following the technique described in U.S. Pat. No. 5,305,743, to which reference is made for detailed description. It suffices here to identify the inflation-air inlet formation  28 , directed inwardly on a central axis  29  which also includes the outwardly directed distal-end formation of the evacuation tube  26 ; the central axis  29  may also be understood as identifying the equator plane (perpendicular to the drawing of  FIG. 5 ) which applies to the inflatable annular ring  18 , after evacuation tube  26  has been swung upward (counterclockwise), in the sense suggested by arrow  30 , and generally for 180° of rotation about an axis  31 , which (axis  31 ) is normal to the plane of the drawing of FIG.  5 . This 180° rotation tucks tube  26  into the flange relatively large edge  32  of the open skirt of the moulded intermediate product of FIG.  5  and makes it a simple matter to turn the remainder of the skirt inside-out, thus defining ring  18 , with the edge flange  32  seated on a ledge  33  of the upper dome-shaped feature (body-membrane portion or liner  13 ′) of the moulded intermediate product. 
     In the preferred form shown, the mask body member  13  ( FIGS. 4 and 7 ) is a separately moulded component of relatively stiff nature as compared to the moulded intermediate product of FIG.  5 . Stiffness vs. softness will be understood to be relative terms and not necessarily to imply that these components are formed from different materials. 
     In  FIG. 4 , the body component  13  is seen to comprise an apertured panel which is essentially a moulded dome or bowl  34  having a concave inner surface which conforms to the convex moulded contour of the dome shape  35  of the relatively soft (i.e., thin-walled) component of  FIG. 5 , these components being shown in  FIG. 6  in assembled relation. Relative stiffness (thickness) in the bowl or dome  34  of  FIG. 4  is generally in the range 2 to 5 mm, with gradually reducing thickness for greater flexibility in approach to the lower or distal end. The bowl or dome  34  has a peripheral edge which terminates in a single plane, for adhesively bonded seating to the ledge  33  of the relatively soft component of  FIG. 5 , after making the inside-out inversion. 
     The stiffness of body member  13  is greatest in the region of proximal-end seating to ledge  33 , above which an inlet-air formation  36  is oriented on an axis  37  which is not only inclined at an acute angle α to the plane of seating to ledge  33 ., but is also laterally offset from the central longitudinal plane of symmetry of the mask, denoted  5 — 5  in FIG.  3 . Relative stiffness of body member  13  is also enhanced (i) by the fact that its distal half features a slot  38  of width less than the diameter of the re-entrant distal-end tube  26 , (ii) by the fact that the re-entrant tube  26  is adhesively retained in cradled support by and between confronting edges of slot  38 , and (iii) by the fact that the distal end of evacuation tube  23  is preferably preformed (as seen in  FIG. 2 ) with a quarter-turn helical advance to track the course of slot  38  in the upper or proximal half of body member  13 . The evacuation tube  23  is preferably relatively stiff, e.g., stiffness (thickness) in the order of magnitude of the material at the upper (proximal) half of body member  13 , and is seen in  FIG. 2  to have telescoping fit to the proximally directed upper end of re-entrant tube  26 ; this is an adhesively sealed fit. 
     Stated in other words and in explanation of the distal and proximal halves of the body member  13  and the relation of these halves to the relatively thin material and distal-half extent of re-entrant tubular conduit  26 , said tubular conduit may be said to extend proximally to approximately 50 percent of the longitudinal extent of the inflatable ring  18 ; alternatively, said tubular conduit  26  may be said to extend proximally to at least substantially 50 percent of the longitudinal extent of the inflatable ring  18 , consistent with the drawings of  FIGS. 2 ,  3 , and  6 . Furthermore, as seen in  FIG. 4 , the distal half of backing-plate member  13  is essentially straight, thus determining a straight proximal direction of tubular conduit  26  for substantially the distal half of the longitudinal extent of the mask. 
     As also seen in  FIG. 2 , the back-cushion panel  25  covers a substantial part of the posterior surface of the mask, being peripherally sealed around the generally elliptical course of inflatable ring  18 , and also being centrally adhered to the re-entrant tube  26  for substantially the entire length of tube  26 , as suggested by cross-hatching  39 . Finally, to assure integrity of the inflatable ring  18 , the re-entrant tube  26  is adhesively sealed to the adjacent edges of tube- 26  local passage through ring  18  at the distal location designated  40  in  FIG. 3 ; for purposes of avoiding undue complexity in the drawings, this adhesively sealed region is not shown but will be understood to be along the line of tube- 26  intercept with locally adjacent walls of inflatable ring  18 . In  FIG. 5 , this intercept line is accounted for by a local cut-out  40 ′ at the distal end of the skirt of the intermediate product of FIG.  5 . 
     The simplified sectional diagram of  FIG. 8  illustrates the functional cooperation of described component parts and features of the described gastro-laryngeal mask construction, in inflated condition, to account for diametrically opposite section cuts through right and left halves of the inflatable ring  18 , spaced by sealed fit of body member  13  to the inner profile of ring  18 . The back-cushion panel  25 , being centrally adhered at  39  to the upper central region of re-entrant tube  26 , provides a lifting force which is in the direction to hold open the evacuation tube and, therefore, not to collapse tube  26  when the back cushion is inflated; without this force, in opposition to a retaining force attributable to adhesive connection to body member  13  (along edges of slot  38 ), there would be no tendency to hold a softly compliant tube  26  against collapse, in that the cushion panel would outwardly expand itself to a bowed shape  25 ′ suggested by phantom outline in  FIGS. 6 and 8 . 
     Preferably, the effective arcuate extent of adhesive connection  39  is in the range 45° to 90° about the central axis of tube  26 , as seen in FIG.  8 . Preferably also, the adhesive connection of tube  26  along the straight edges of the distal half of slot  38  accounts for a corresponding range of support of tube  26  against collapse in the circumstance of back-cushion inflation. In other words, inflation of the ring  18  and back cushion  25  will assure developed vertical forces to hold the evacuation passage of re-entrant tube  26  in substantially open condition, but the transversely opposed arcuate regions (each of approximately 90° arcuate extent) between these adhesively connected regions are vulnerable to compressionally inward bowing, thus reducing the sectional area of tube  26  while the mask is inflated. The invention resolves this vulnerability by providing axially spaced stiffening ribs or ridges  42  as integral formations of the re-entrant tube  26 , in the initially moulded intermediate product of FIG.  5 . As shown, there are three mutually opposed pairs of ridges  42 , at axial spacings which are in the order of the unstressed bore diameter of tube  26 . For the indicated silicone-rubber material of the product of  FIG. 5 , the incremental local thickness at ridges  42  is suitably twice or three times the otherwise uniformly thin moulded product of  FIG. 5 , as seen in FIG.  5 A. 
     In  FIG. 8 , a section taken near the location of tube  26  connection to the more stiffly compliant evacuation tube  23 , the inflated condition of the GLM mask of the invention is seen to have an overall “height” dimensions H 1 , meaning front-to-back (i.e., laryngeal inlet-to-pharynx back wall). When the mask is deflated, this dimension H 1  is seen to be reduced by approximately 50 percent, as shown at H 2  in  FIG. 9  for the deflated condition of the same mask. When deflated, as has been pointed out in U.S. Pat. No. 5,297,547, the ring  18  collapses into flattened double walls (marked  18 ′) which are upwardly dished; and although deflation does little to compress tube  26  other than at the region  39 ′ of adhesion to the back-cushion panel  25 , the overall deflated extent H 2  is essentially unchanged from the dimension H 2  which applies for collapse of ring  18 . On the other hand, at the distal end of the mask, the collapse of ring  18  is operative upon the formed distal-end opening  43  of tube  26  to somewhat flatten the opening  43 , into a generally shovel-shaped distal lip feature which merges smoothly into the adjacent upwardly dished double-wall. shape  18 ′ shown in the longitudinal mid-section of FIG.  9 . 
     It will be appreciated that the GLM device described thus far has an airway tube  11  that is of larger diameter than the evacuation tube  23 ; in this circumstance, the airway tube  11  is large enough to accommodate guided insertion of an endotracheal tube. The tubes  11 ,  23  enter the described laryngeal mask  10  in side-by-side relation and are preferably adhesively secured to each other in this side-by-side relation, and along their full longitudinal extent, in order to provide a measure of torsional resistance against twisting, thereby aiding a medically qualified person in quickly and correctly installing a fully deflated GLM in a patient, with assurance that, upon inflation of ring  18  and the back-cushion panel  25 , an exclusive and sealed airway connection will be established to the laryngeal inlet, via lumen  14  and from the airway tube  11 ; concurrently, a similarly exclusive evacuation connection is established to the upper sphinctral region of the oesophagus, via the distal-end opening  43  of tube  26 , through the evacuation tube  23 , and to suitable waste-collection means (not shown) external to the patient. 
     More specifically as to insertion of the fully deflated GLM device in a patient, it will be understood that a range of GLM sizes is available from which to select a sufficiently correct size for the patient. Deflation is accomplished via external means (not shown) and via check-valve means  21  to hold the deflated condition wherein the dome shape of body member  13  rises from within the dished peripheral lip  18 ′ of the collapsed ring  18 . A skilled operator is quickly able to develop the desired appearance of the GLM in its deflated state; but for a uniformly correct deflated shaping, it is recommended to use a forming tool as described in U.S. Pat. No. 5,711,293. 
     When correctly shaped and in its deflated condition, and at the distal end of the GLM, the opening  43  will have been flattened, and this distal end merges with the peripheral lip  18 ′ of the collapsed ring  18 . Noting that the entire distal half of the mask is of relatively soft material, stiffened only by indicated adhesive connection, the distal end projects distally and at its upwardly flared merge with lip  18 ′, for low acute-angle incidence to the posterior arcuate profile of the patient&#39;s throat passage. That being the case, a medical technician need only make sure that upon inserting the mask via the patient&#39;s mouth and throat, the flattened distal end rides the outer (posterior) arcuate contour of the patient&#39;s airway, in that the softly flexible nature of the distally projecting and somewhat flattened distal end will be flexibly self-adapting to local irregularities (if any) in the course of passage into the pharynx; final insertional location is noted by an increase in encountered resistance, upon distal-end engagement of the GLM with the upper sphinctral region of the oesophagus. At this juncture, inflation air supplied via line  19  and retained by check-valve means  21  establishes (i) the described seal of ring  18  to the laryngeal inlet, (ii) back cushion (panel  25 ) contact with the back wall of the pharynx, and (iii) full opening of the evacuation tube  26  for maximum accommodation of a possible gastric discharge from the oesophagus. 
     Beyond what has been described,  FIG. 10  illustrates at phantom outline  26 ′ that the flexible length of the re-entrant tube  26  may be of even greater length than the approximately half-mask length shown by the solid lines of FIG.  5 . In that event, arcuate stiffener ridges as described at  42  will be preferred, as long as lateral support is needed to prevent side-wall collapse of the extended tube  26 ′, in the inflated condition of the mask, i.e., including inflation of back-cushion panel  25 . 
       FIGS. 10  to  12  illustrate another GLM embodiment wherein an airway tube  50  and an evacuation tube  51  are of equal size, adhered (as suggested at  52 ) to each other in side-by-side relation for torsionally resistant and symmetrically positioned entry into corresponding side-by-side ports  53 ,  54  of the dome like moulded backing plate or body member  55  of  FIGS. 11 and 12 . The backing plate  55  may be similar to plate  13  of  FIG. 4 , except that in  FIG. 11  the somewhat helically arcuate conduit path from the inserted distal end of evacuation tube  51  to the point  56  of softly compliant re-entrant tube ( 26 ) connection is provided by an integral passage formation  57  of the backing plate  55 . At point  56  in  FIG. 11 , the formation  57  is seen to be in the central vertical plane  58  of symmetry of the bowl or dome-shape of backing plate  55  and in alignment for accepted proximal-end insertional accommodation of a re-entrant tube  26  of thin-walled material to which backing plate  55  is to be assembled, with edges of the straight slot  38 ′ supporting tube  26  in the manner already described. Also integrally formed with backing plate  55  is an inlet-connection counterbore for coupled connection of airway tube  50  to the laryngeally exposed side of the mask. Features in  FIG. 10 , such as the back-cushion panel  25 , the inflatable ring  18 , and the adhesively bonded connection  39  of panel  25  to tube  26  are all as previously described. 
     It will be understood that the inside-out technique described in connection with  FIGS. 5 and 6  for initially moulding and then inverting the skirt of the moulded product, is but one illustration of a way to create the mask and its inflatable ring, in which case the flexible drainage conduit does not get inverted. That being the case, the reinforcement ribs  42  are initially formed portions of the outer surface of the moulded product. On the other hand, another technique for forming the mask with its inflatable ring, involves moulding the mask bowl integrally with an elliptically configured product as shown in  FIG. 13 , wherein completion of inflatable-ring ( 18 ) integrity requires only an adhesively bonded completion of the ring peripherally around the inner substantially elliptical profile, where backing-plate ( 13 ) connection is also adhesively secured. In that case, the drainage tube  26  is integrally-moulded with the non-invertible ring ( 18 ), so that an inversion of tube  26  is necessary, to have it project re-entrantly, in the proximal direction, and the moulded product which is to become inflatable ring  18  must be cut away as at  40 , to permit inverted tube  26  to “pass through” the inflatable ring, in order to develop a relationship which is suggested by FIG.  5 . Of course, if tube  26  is to be inverted, the reinforcement ribs  42  are preferably integrally formed as radially inward rib reinforcements or discontinuities in the moulded bore of tube  26 . Inversion of tube  26  places these rib reinforcements on the outer surface of tube  26 , so that the bore of tube  26  is inherently smooth.