**4. Insertion technique**

All LMAs consist of four parts, a hollow tube (shaft) continuous with a hollow mask or cuff, inflation line with pilot balloon and drain (gastric access) tube. The broad elliptical inflatable cuff has a smooth upper surface that prevents pharyngeal secretions from entering the airway and an under surface that sits over the larynx to create a seal.

The patient's neck is flexed and head is extended (sniffing position) (**Figure 1**). The LMA is partially deflated and the backside of the LMA is lubricated. The shaft is grasped with the dominant hand like a pen, as near to the mask as possible. The deflated flattened mask is inserted against the hard palate downward into the mouth along the curvature of the back of the pharynx. The index finger follows the tube into the mouth to keep pressing "back" and "down" until the aperture faces the laryngeal inlet. If at any time during insertion the mask fails to stay flattened or starts to fold back, it should be withdrawn and reinserted. Another technique is to

causes less mucosal trauma and leads to fewer airway morbidities. If an assistant is available, he can apply a jaw thrust manoeuvre which moves the tongue forward and prevents compression of the epiglottis [14]. In case of a single operator, a tongue depressor or a laryngoscope may be used to assist insertion of the LMA [15].

*Second Generation Supraglottic Airway (SGA) Devices DOI: http://dx.doi.org/10.5772/intechopen.93947*

Weight-based selection as per the manufacturer's guideline is done. If unsure, check the package cover for size information. More than one size should always be available, because the correct size cannot always be predicted. Weight-based selection has given way to sex-based selection, especially in adults. The consensus seems to be that the correct size would be a size 4 for most adult women and a size 5 for most adult men [51–57]. Whatever the initial size selected, if malposition or an inadequate seal is present, a larger size LMA should be considered. Alternative formulas based on weight have been proposed [58, 59]. For children, the width of the second to fourth fingers can be matched to the widest part of the mask [60]. If repeated attempts with

Wait for full recovery from anaesthesia. Do not try to pull out the SGA if the patient is biting down on the shaft. Usually, patients emerge smoothly with SGAs. It is recommended to use a bite block with the LMA in order to prevent damage to the airway tube or pilot balloon during emergence. Manufacturers usually recommend using a wad of gauze swabs rolled into a cylindrical shape and placed along the LMA. Some anaesthesiologists prefer to place the Guedel's airway. The LMA should never be removed if patient is in a light plane of anaesthesia as it may

SGAs have been conventionally classified based on the following characteristics

In recent years, devices with oesophageal sealing (Second Generation SGAs) have gained popularity due to presence of a gastric port which allows drainage of stomach contents and reduces the incidence of regurgitation and aspiration pneumonitis.

The airway sealing pressure or the oropharyngeal leak pressure (OLP) is the pressure at which gas leak occurs around the device. It indicates the degree of airway protection. After the successful placement of airway device, OLP can be determined

• Whether it is inflatable or anatomically pre-shaped

• Whether or not the sealing effect is directional and

Modern classification of SGAs is given in **Table 1**.

• Where in the hypopharynx it provides a seal

• Whether or not oesophageal sealing occurs

one type of LMA are unsuccessful, changing to another type may help.

**5. Size selection**

**6. Removal technique**

precipitate a laryngospasm.

**7. Classification**

**7.1 Sealing pressure**

**255**

by Miller [61].:

*Technique of LMA insertion. (a) The deflated and lubricated LMA is held by the index finger and thumb of right hand. (b) The left hand stabilizes the occiput. LMA is inserted in the mouth pressed against the hard palate. (c) Using the index finger, it is advanced behind the tongue. (d) It is further pushed into the hypopharynx with the index finger. (e) After removing the index figure, the airway tube of the LMA is pushed further inside with the left hand till a resistance is felt.*

allow the dominant hand to guide the shaft and use the nondominant hand to push the tube with or without an introducer [45–47].

Proper placement of the airway is prudent. Cuff should be inflated to achieve adequate tidal volumes with minimal leaks. The cuff inflation pressure should never exceed 60mm Hg. Higher Cuff pressures may lead to increased pharyngeal mucosal pressures which may lead to mucosal ischemia and airway morbidities [48].

Marjot showed that intracuff pressure increased as cuff volume increases [49]. The pressure exerted on the pharynx by the SGA is usually higher than that of mucosal capillary perfusion pressure when the cuff is inflated with the recommended maximum volume of air.

However, if the cuff is deflated excessively, it may not protect the airway from soiling, due to the regurgitated fluid from the stomach [50]. Therefore. it is desirable to inflate the cuff of the SGA with minimum volume of air which provides a seal around the mask.

In case of malpositioning of the mask, it may have to be replaced or other manoeuvres may have to be tried. A partially or fully inflated SGA cuff may ease insertion [8–10]. Wakeling et al. claim that inserting an SGA with a fully inflated cuff causes less mucosal trauma and leads to fewer airway morbidities. If an assistant is available, he can apply a jaw thrust manoeuvre which moves the tongue forward and prevents compression of the epiglottis [14]. In case of a single operator, a tongue depressor or a laryngoscope may be used to assist insertion of the LMA [15].
