CHAPTER 3Managing the AirwayBasic techniques，37 the laryngeal mask airway，42 emergency airwaySimple adjuncts，39 tracheal intubation，43 techniques，50maintenance of a patent airpway is an essential prerequisite for the safe and successful conduct of Anse sthesia。in addition，During resusitation patients often have an obstructed airtway either as the cause or result of their loss of consiousness。the skill of airtway mainte Nance should be acquired by all doctors，And not simply regarded as the responsibility of the Anse sthetist .the descriptions of aiway management techniques，which follow，Are intensed to supplement practice either on a mani kin or preferably on ananyBasic techniquesansesthesia frequently results in loss of the airway and it is most easily restored by a combination of the head tilt along with a jaw thrustthe later is provided by the ansesthe tist s fourth and fifth fingers(of one or both hands)Lifting the angle of the mandible .the overall effect desired is that the patient s mandible is lifted into the mask rather than the mask being pushed into the faceFACEMASKSl the most commonly used type in adults is the BOC anatomical face mask(fig . 3 . 2)which is designed to fit the contours of the face with the miningl leakage of anshetic gases is minimized by an air-filled cuff around the edge。l masks ate made in a variety of sizes and the smallest one，which provides a good seal，should be used(to minimize the increase in dead spaaadl the ambu mask(fig . 3 . 2)has a transparent body-allowing identification of vomitmaking it poplar for resusitation。l all masks must be disinfected between each patient。簡(jiǎn)單調(diào)整the most commonly and used are the oropharyngeal(gue del)and nasopharyngeal airways，Inserted after the induction of ansesthesia toOROPHARYNGEAL AIRWAYL these are curved plastic tubes，flattened in cross-section and flanged at the oral end，which lie over the tone，prevenng it from fallingl they are available in a variety of sizes from neonates to large adults。the commonest sizes are 2-4，for small to large adults，respectvely。l a guide to the correct size is determined by comparing the airtway length to the vertical distance from the corner of the patient s mouth to the anglel it is initially inserted upside down as far as the back of the hard pallate(fig . 3.3a)、Rotated 180 (fig.3.3b)和fullyNASOPHARYNGEAL AIRWAYL these are round，malleable plastic tubes，beveled at the pharyngeal end and flanged at the nasal end。l they are sized on their internal diameter in millimeters，with length increasing with diameter。the common sizes in adults are 6-8mm，for small to large adults，respectvely。l a guide to the correct size is made by comparing the diameter to the external naris。L prior to insertion，the p atency of the nostril(usually the right)should be checked and the airway lubricated .l the airtway is inserted along the floor of the nose，with the bevel facing medially to avoid catting the turbina tes(fig . 3 . 4)。l a safety pin may be inserted through the flange to prevent inhalation of the airway .L if obstruction is encounered，force should not be used as severe bleeding may be provoked . instead，the other nostril can be tried .PROBLEMS WITH AIRWAYSThe presence of snoring，in drawing of the supraclavicular，supra sternal and intercastal spaces，Use of the accessory muscles or paravicularcommon problems arising using these techniques along with a face mask during ansesthesia are :1 inability to maintain a good seal between the patient s face and the mask，particularmy in those without teeth；2 fatigue，when holding the mask for proonged periods；3 the risk of asiration，due to the loss of upper airway reflexes；4 the anshetist is not free to deal with any other problems，which may arise。the laryngeal mask airtway(LMA)or tracheal intubation may be used to overcome these problems。The laryngeal mask airwaythis device was designed for use in spontaneously breaking patients。it conists of a mask 、Which sits over the laryngeal opening、Attached to which is a tube、Which protrudes from the mouth and conningon the perimeter of the mask is an inflatable cuff，Which creates a seal and helps to stabilize it。the LMA is produced in a variety of sizes suitable for all patients，from neonates to adults，With sizes 3 and 4 being the most commonly used in finthe LMA is reusable，provided that it is sterized between each patient。the use of the laryngeal mask overcomes some of the problems of the previous techniques :l it is not affected by the shape of the patient s face or the absence of teeth；l the anshetist is not required to hold it in position，avoiding fatigue and allowing any other problems to be dealt with；l it reduces the risk of asiration of regurgitated gastric contents，but does not eliminate it。its use is