Page 172 - Clinical Application of Mechanical Ventilation

138 Chapter 5

for complications such as regurgitation, laryngeal spasm, bronchospasm, coughing,
retching, excessive salivation, and oxygen desaturation (Nunez et al., 1998; Samar-
kandi, 1998).
Limitations of LMA

Due to the unique position of its mask, rotation or turning of the LMA may cause mis-
placement of the mask and result in gastric insufflation and air leakage from the mask
seal (Latorre et al., 1998). For this reason, the patient’s head position and alignment of
the LMA should be checked frequently to ensure adequate ventilation. Positive pres-
Positive pressure ventila- sure ventilation may be provided via most LMA at peak inspiratory pressure of up to
tion may be provided via most
LMAs at peak inspiratory 20 cm H O (up to 30 cm H O with LMA-ProSeal). For patients with low compliance
2
2
pressure of up to 20 cm H 2 O or high airflow resistance, the LMA may not be able to withstand the pressure, and
(up to 30 cm H 2 O with LMA-
ProSeal). air leaks may develop. When high peak inspiratory pressure is anticipated, the LMA
should be replaced with an endotracheal tube (LMA North America, Inc., 1999, 2012).
The recommended time of LMA usage for each patient is 2 hours repetitive, with
a maximum time from 6 to 8 hours in the hands of experienced users. For extended
usage, a heat and moisture exchanger may be used to provide supplemental humid-
ity to the airway. Since nitrous oxide diffusion through the silicone cuff of a reusable
LMA can raise the cuff volume and pressure, the cuff pressure should be checked
periodically and maintained at 60 cm H O. Excessive cuff pressure may lead to
2
malposition of the LMA or other adverse outcomes (LMA North America, 2012).
The LMA is not a secured airway and it does not protect the lower airway from
Most LMAs are dispos-
able. aspiration. The esophagus, which lies posterior to the LMA, has complete access to
the larynx, and thus regurgitation or aspiration is a potential complication (Norton,
1998).
Most LMAs are disposable. The reusable version of the LMA is handmade, thus
the cost is rather significant. With proper sterilization by steam autoclave and careful
autoclave: A method of steriliza-
tion using steam pressure, usually handling, it can be reused up to 40 times, as long as the mask is not damaged during
at 250°F (121°C) for a specific use, handling, and steam autoclaving. Table 5-7 outlines the limitations of the LMA.
length of time. (Up to 275°F or
135°C for reusable LMA’s.

TABLE 5-7 Limitations of the Laryngeal Mask Airway

Rotation of the LMA may cause misplacement of mask, gastric inflation,
and air leaks.

Cuff does not provide seal at airway pressures greater than 20 cm H O.
2
The LMA does not protect the lower airway from aspiration.
Reusable version is costly but it can be reused up to 40 times after
cleaning and steam sterilization.
Steam autoclaving is the only recommended method of sterilization for
reusable LMA.
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