For details on equipment design and indications for use, refer to Chapter 3.
The LMA may be inserted almost immediately in the patient who has stopped breathing and become deeply unconscious.
There is some evidence to suggest that when a bag-valve device is used to ventilate the patient prior to insertion of the LMA, gastric regurgitation and aspiration are more likely to occur than if the LMA has been inserted immediately, without prior ventilation, as a first-line airway adjunct (Stone et al. 1998).
Once a ventilatory device such as a bag-valve has been attached to the LMA, it is important that high inflation pressures are not generated during ventilation as this increases the risk of gastric inflation and therefore potential regurgitation and aspiration.
• The LMA is available in sizes suitable for neonates through to large adults.
• A size 4 or 5 is suitable for all but very small adults, who may be more suited to a size 3.
Insertion technique (see Figure 7.5)
• Check the cuff patency by inserting the appropriate amount of air (as shown in Table 7.3). Deflate the cuff and ensure the outer face of the cuff is lubricated.
• Position the patient supine with the head and neck aligned. Slightly flex the neck and extend the head unless there is suspicion of cervical spine injury.
• Hold the tube like a pen and introduce the cuff into the patient's mouth. Using the index finger to provide support at the tip of the cuff, advance it along the roof of the patient's mouth into the airway until it reaches the back of the throat.
• Take hold of the external part of the tube and, keeping it in the midline, advance it further until resistance is felt and it locates in the back of the pharynx.
• Inflate the cuff with the appropriate amount of air. The tube should lift 1-2cm out of the mouth as the cuff finds its correct position on inflation.
• Connect the tube to a bag-valve device with supplemental oxygen and confirm adequate ventilation by noting bilateral chest movement. Use a stethoscope to listen for air entry during ventilation.
• If placement of the LMA does not allow adequate ventilation within 30 seconds of commencement, it should be removed and the patient ventilated and oxygenated prior to further attempts.
• Insert a bite block, such as a roll of gauze or oropharyngeal airway, alongside the tube and tie the tube securely.
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