National Board Ex- 6 Book .pmd - National Board Of Examination

two flexible vertical rubber bars,called mask aperture bars (MAB),to prevent the epiglottis fromentering and obstructing the airway.The inner aspect of themask is called the bowl, which iscomprised of the distal aperture,mask aperture bars, back plateand the inner aspect of the inflatablecuff. The mask inflationline, which is attached to the mostproximal portion of the cuff inthe midline consists of fourparts, the long narrow inflationline itself, the inflation indicatorballoon (pilot balloon), a metallicvalve and the syringe port. Thevalve, which has a white colouredcore is made from polypropyleneand has a stainless steel springvalve. The safety record is goodfor elective surgery. Positive pressureventilation is readily accomplishedwith the cLMA. 2 In thecLMA the glottic seal is usuallylost at peak airway pressuresabove 20 cm H2O. Though thecorrectly positioned cLMA offerssome protection against aspiration,the incidence of aspirationwith the LMA in fasted patientsis 0.012%. 4,5 It is available in eightsizes, neonates to large adults (1,1.5, 2, 2.5, 3, 4, 5, 6).Flexible Laryngeal maskairway (LMA-Flexible) 4 -TheFlexible (reinforced) LMA wasreleased in1992 following reportsof kinking of LMA tube inAnaesthesia in 1990. It is madefrom medical grade silicone andrubber and is reusable. It consistsof a classic LMA cuff connectedto a flexible wire reinforced tubewhich is longer and narrowerthan the airway tube of thecLMA. Though the diameter ofthe oral tube of the Flexible LMAis narrower than that of thecLMA, it is comparable to atracheal tube thus making itpractical for intraoral surgeriesespecially adenotonsillectomy.The extra length ensures that theanaesthesiologist can be awayfrom the surgical field. It isavailable in six sizes (2, 2.5, 3, 4,5, 6).Fig 3. LMA-FlexibleLMA Unique 4 - The disposableLMA or the LMA-Unique was releasedin 1998 for cardiopulmonaryresuscitation because thesilicone based cLMA was costlyand needed proper sterilization toprevent cross infection. The disposableLMA is constructedfrom clear medical-grade polyvinylchloride, other than the stainlesssteel spring valve. It is suppliedsterile, and cannot withstandautoclaving without losingstructural integrity. It is meant forsingle use in the field or out ofbox situations. The dimensions,shape, and intersize scaling areidentical to the cLMA, but thetube is more rigid and the cuffthicker. The disposable LMA iscurrently available in size 3-5. InAugust 2000, the design was alteredto make the backplate andairway tube softer, but the cuffwas unchanged.Fig 4. LMA UniqueThe Intubating LMA (ILMA)4,6,7-The intubating LMA-Fastrach is especially designed toaid blind tracheal intubation andit consists of three parts-theILMA itself, the tracheal tube anda stabilizing rod. The ILMA is arigid, anatomically curved airwaytube made of stainless steel witha standard 15 mm connector. Thetube is wide enough to accommodatean 8.0 ETT and shortenough to ensure passage of theETT beyond the vocal cords. Arigid handle attached to the tubefacilitates one-handed insertion,removal, and most importantly,adjustment of the device’s positionso that the aperture directlyopposes the larynx. The mask aperturebars of the cLMA are replacedhere by a single flap, theepiglottic elevating bar of theILMA. It has been used for routineintubation, rescue intubation,and intubation of the difficult airwaypatient after the induction ofanesthesia or in the awake state. 5The ILMA is available in adultsizes only (3,4,5) that correspondJournal of Postgraduate Medical Education, Training & Research85