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1、CHAPTER 3Managing the AirwayBasic techniques, 37 The laryngeal mask airway, 42 Emergency airway Simple adjuncts, 39 Tracheal intubation, 43 techniques, 50 Maintenance of a patent airway is an essential prerequisite for the safe and successful conduct of anesthesia. In addition, during resuscitation
2、patients often have an obstructed airway either as the cause or result of their loss of consciousness. The skill of airway maintenance should be acquired by all doctors, and not simply regarded as the responsibility of the anesthetist. The descriptions of airway management techniques, which follow,
3、are intended to supplement practice either on a manikin or preferably on and anesthetized patient under the direction of a skilled anesthetist.Basic techniques Anesthesia frequently results in loss of the airway and it is most easily restored by a combination of the head tilt along with a jaw thrust
4、 (see Chapter 2). The latter is provided by the anesthetists fourth and fifth fingers (of one or both hands) lifting the angle of the mandible. The overall effect desired is that the patients mandible is lifted into the mask rather than the mask being pushed into the face (Fig. 3.1).FACEMASKSl The m
5、ost commonly used type in adults is the BOC anatomical facemask (Fig. 3.2) which is designed to fit the contours of the face with the minimum of pressure.l Leakage of anesthetic gases is minimized by an air-filled cuff around the edge.l Masks ate made in a variety of sizes and the smallest one, whic
6、h provides a good seal, should be used (to minimize the increase in dead space, which occurs).l The Ambu mask (Fig. 3.2) has a transparent bodyallowing identification of vomit making it poplar for resuscitation.l All masks must be disinfected between each patient.Simple adjuncts The most commonly an
7、d used are the oropharyngeal (Guedel ) and nasopharyngeal airways, inserted after the induction of anesthesia to help maintain the airway in conjunction with the techniques described above.OROPHARYNGEAL AIRWAYl These are curved plastic tubes, flattened in cross-section and flanged at the oral end, w
8、hich lie over the tongue, preventing it from falling back into the pharynx.l They are available in a variety of sizes from neonates to large adults. The commonest sizes are 2-4, for small to large adults, respectively.l A guide to the correct size is determined by comparing the airway length to the
9、vertical distance from the corner of the patients mouth to the angle of the mandible.l It is initially inserted upside down as far as the back of the hard palate (Fig. 3.3a), rotated 180 (Fig.3.3b) and fully inserted util the flange lies in front of the teeth or gums in an edentulous patient (Fig. 3
10、.3 c).NASOPHARYNGEAL 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 6-8 mm, for small to large adults, respec
11、tively.l A guide to the correct size is made by comparing the diameter to the external naris.l Prior to insertion, the patency of the nostril (usually the right ) should be checked and the airway lubricated.l The airway is inserted along the floor of the nose, with the bevel facing medially to avoid
12、 catching the turbinates (Fig.3.4).l A safety pin may be inserted through the flange to prevent inhalation of the airway.l If obstruction is encountered, force should not be used as severe bleeding may be provoked. Instead, the other nostril can be tried.PROBLEMS WITH AIRWAYS The presence of snoring
13、, indrawing of the supraclavicular, suprasternal and intercastal spaces, use of the accessory muscles or paradoxical respiratory movement (see-saw respiration) suggest that the above methods ate failing to maintain a patent airway. Common problems arising using these techniques along with a facemask
14、 during anesthesia are:1 inability to maintain a good seal between the patients face and the mask, particularly in those without teeth;2 fatigue, when holding the mask for prolonged periods;3 the risk of aspiration, due to the loss of upper airway reflexes;4 the anesthetist is not free to deal with
15、any other problems, which may arise.The laryngeal mask airway (LMA) or tracheal intubation may be used to overcome these problems.The laryngeal mask airway This device was designed for use in spontaneously breathing patients. It consists of a mask, which sits over the laryngeal opening, attached to
16、which is a tube, which protrudes from the mouth and connects directly to the anesthetic breathing system. On 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 female and male adults, respectively. Positive pressure
