Page 169 - Clinical Application of Mechanical Ventilation

Special Airways for Ventilation 135

TABLE 5-5 uses and Application of a Laryngeal Mask Airway

Establishes airway in proven difficult intubations

Provides spontaneous and controlled ventilation in infants and children

Serves as a bridge to more secured airways
Provides complete survey of the larynx and trachea prior to thoracotomy

Provides lower work of breathing than endotracheal tube

Provides less hemodynamic response during surgical procedures
Provides less airway reaction

Offers benefit of shorter stay in hospital due to avoidance of
endotracheal intubation

(Data from Ferson et al., 1997; Fukutome et al., 1998; Joo & Rose, 1998; Joshi et al., 1998; Kim & Bishop, 1999;
Lopez-Gil, Brimacombe & Alvarez, 1996; Marietta et al., 1998; Parmet et al., 1998; Stanwood, 1997;
Webster et al., 1999; Zerafa et al., 1999.)
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The LMA should not be used as a conduit for emergency resuscitation drugs (e.g.,
epinephrine) because of low success rate (27% in one study). It may be used as an
option in emergency situations where a venous access or an endotracheal tube is not
readily available (Alexander et al., 1997; Challiner et al., 1997).
Selection of L MA

The LMA is reusable (silicone-based) or disposable (polyvinyl chloride). The dis-
For most adults, size 4 posable LMA-Unique performs similarly to the reusable LMA in clinical situations
should be used for females
and size 5 for males. (Verghese et al., 1998). For most adult females, size 4 should be used, and size 5
should be used for most adult males (Asai et al., 1998). A larger LMA with less air
in cuff provides a better seal. A smaller LMA along with overinflation of the cuff
A larger LMA with less air reduces the cuff compliance, resulting in an improper fit within the pharyngeal space.
in cuff provides a better seal.
When the maximum cuff volume is exceeded, air leak, gastric insufflations, and mask
malposition become more likely (Brimacombe & Brain, 1997; Ferson et al., 1998).
The standard cuff pressure is 60 cm H O (Berry et al., 1998), but the air in the cuff
2
should be adjusted to the minimal effective volume so as to decrease intracuff pressure,
pressure on the pharynx (Asai et al., 1998), and incidence of sore throat (Nott, 1998).
Table 5-6 provides the suggested LMA size for patients ranging from neonates to large
adults and the maximal cuff inflation volume (LMA North America, Inc., 1999).
Insertion of L MA

Different LMA types or brands require different insertion techniques. Users must
follow the manufacturer’s guidelines or recommendations for the insertion of
LMA. Prior to insertion of the LMA, the patient is in a supine position, and the
head is advanced slightly. The chin is depressed to open the mouth. With the cuff

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