referring first to the preferred embodiment of fig1 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 &# 39 ; 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 fig1 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 ( fig2 ) which is peripherally bonded to the inflatable ring 18 ( fig1 ) and in sealed engagement at peripheral line 25 &# 39 ; 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 ( fig2 ) 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 fig3 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 fig5 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 fig5 ) 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 fig5 . this 180 ° rotation tucks tube 26 into the flanged relatively large edge 32 of the open skirt of the moulded intermediate product of fig5 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 &# 39 ;) of the moulded intermediate product . in the preferred form shown , the mask body member 13 ( fig4 and 7 ) is a separately moulded component of relatively stiff nature as compared to the moulded intermediate product of fig5 . stiffness vs . softness will be understood to be relative terms and not necessarily to imply that these components are formed from different materials . in fig4 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 fig5 these components being shown in fig6 in assembled relation . relative stiffness ( thickness ) in the bowl or dome 34 of fig4 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 fig5 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 fig3 . 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 fig2 ) 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 fig2 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 fig2 , and 6 . furthermore , as seen in fig4 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 fig2 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 fig3 ; 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 fig5 this intercept line is accounted for by a local cut - out 40 &# 39 ; at the distal end of the skirt of the intermediate product of fig5 . the simplified sectional diagram of fig8 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 &# 39 ; suggested by phantom outline in fig6 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 fig8 . 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 fig5 . 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 fig5 the incremental local thickness at ridges 42 is suitably twice or three times the otherwise uniformly thin moulded product of fig5 as seen in fig5 a . in fig8 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 &# 34 ; height &# 34 ; dimension 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 fig9 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 &# 39 ;) which are upwardly dished ; and although deflation does little to compress tube 26 other than at the region 39 &# 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 &# 39 ; shown in the longitudinal mid - section of fig9 . 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 &# 39 ; 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 &# 39 ; 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 &# 39 ;, 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 , fig1 illustrates at phantom outline 26 &# 39 ; 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 fig5 . 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 &# 39 ;, in the inflated condition of the mask , i . e ., including inflation of back - cushion panel 25 . fig1 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 55 or body member of fig1 and 12 . the backing plate 55 may be similar to plate 13 of fig4 except that in fig1 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 fig1 , the formation 57 is seen to be in the central vertical plane 58 of symmetry of the bowl 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 &# 39 ; 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 fig1 , 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 fig5 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 fig1 , 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 &# 34 ; pass through &# 34 ; the inflatable ring , in order to develop a relationship which is suggested by fig5 . 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 .
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 .