**7.1 Sealing pressure**

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

allow the dominant hand to guide the shaft and use the nondominant hand to push

*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*

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

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

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

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

pressures which may lead to mucosal ischemia and airway morbidities [48].

mucosal capillary perfusion pressure when the cuff is inflated with the

the tube with or without an introducer [45–47].

*Special Considerations in Human Airway Management*

*further inside with the left hand till a resistance is felt.*

recommended maximum volume of air.

seal around the mask.

**254**

**Figure 1.**


In 1992 a task force was commissioned by the ASA to establish practice guidelines for management of difficult airway scenarios. In 1993, the ASA published the algorithm for difficult airways. They stressed on an early attempt at LMA insertion in case of inadequate face mask ventilation. cLMA has revolutionised anaesthetic

The angle between the mask and shaft is 30°. The machine end of the shaft has a standard 15-mm adapter. Two flexible vertical bars at the junction of the shaft and mask prevent obstruction of the ventilating lumen by the epiglottis (**Figure 3**). Reusable devices are constructed of medical grade silicone designed to provide an oval seal around the laryngeal inlet and act as a sleeve joint at the upper oesophagus.

practice ever since [63].

• Pilot tube

**Figure 2.** *Classic LMA.*

**257**

• Elliptical mask

*7.2.2 Device description, technical aspects*

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

• Curved airway tube (shaft)

*7.2.3 Limitations of the LMA classic™*

management, it has some limitations

The cLMA consists of the following parts (**Figure 2**):

The single use devices have a cuff constructed of polyvinyl-chloride.

• It has a moderate pharyngeal seal (20 cm H2O)

The classic laryngeal mask is available in eight sizes, as shown in **Table 2**.

Although the cLMA is used in a large number of cases requiring airway

• It may be associated with pulmonary aspiration of regurgitated fluid

*LMA: laryngeal mask airway, ILA: intubating laryngeal airway, LTS: Laryngeal Tube Suction, LTS-D: Laryngeal Tube Suction disposable, PLA: perilaryngeal airway.*

#### **Table 1.**

*Classification of supraglottic airways.*

by turning off the ventilator and closing the adjustable pressure limiting valve of the circuit. A fixed gas flow of 3 L/min is started and the pressure allowed to rise. There are various methods of assessment of OLP [62].:


Correct placement of the LMA can be checked by a simple test. A soap bubble solution is placed over the tip of the drain tube. If the tip of the LMA is in the laryngopharynx, bubbling or bursting of soap solution column will occur during positive pressure ventilation.

#### **7.2 First generation SGA**

## *7.2.1 LMA classic* ™ *(cLMA)*

The original Laryngeal Mask Airway (cLMA, Intavent Direct, Maidenhead, UK) was the first SGAs introduced into clinical practice. It was invented by Dr. Archie Brain in the United Kingdom 1981 and was introduced into clinical practice in 1988. *Second Generation Supraglottic Airway (SGA) Devices DOI: http://dx.doi.org/10.5772/intechopen.93947*

In 1992 a task force was commissioned by the ASA to establish practice guidelines for management of difficult airway scenarios. In 1993, the ASA published the algorithm for difficult airways. They stressed on an early attempt at LMA insertion in case of inadequate face mask ventilation. cLMA has revolutionised anaesthetic practice ever since [63].
