In a few words 9: The supraglottic airway – March 2015
To be able to follow the emergency mantra 101 to maintain a patent airway, a knowledge of all the adjuncts available is important. Where airway reflexes and consciousness are impaired for an ongoing period there will be two ever present problems. Firstly the tongue and the epiglottis can fall back into the oropharynx and occlude the glottis. Secondly, particularly if providing positive pressure ventilation and inevitably pushing some air into the stomach, gastric content can passively flow back along the oesophagus and enter the glottis. A simple OPA or NPA can help with the first problem but not the second. The next adjunct in line is the supraglottic airway. Two in common pre-hospital use are the laryngeal mask airway and the combitube.
The LMA is a tube that runs from just outside the mouth into the oropharynx. It has a standard 15mm connector on one end and a tear shaped cushion on the other. The cushion sits over the hypoglottis. If seated correctly flat it forms a seal that both helps to stop entry of gastric fluid and allows ventilation to occur through a hole in in the middle. The cuff can be air inflated or in some cases solid silicone. The LMA also displaces the tongue and the point of the ‘tear’ sits just inside the oesophagus. As such it can stimulate airway reflexes if they are slightly intact. It is a great option in cardiac arrest or where the patient will remain unconscious without any return of airway reflexes.
The combitube is a very different supraglottic airway to the LMA. It can be used on the same occasions as an LMA and offers similar protections. It is more complex than the LMA and has more steps in insertion. It is actually made of two joined tubes with two inflatable cuffs. At the proximal end a 15mm connector is attached to both external tube openings. There is a larger cuff half way along the tube that is inflated in the oropharynx. This displaces the tongue and epiglottis sealing the upper airway. The smaller cuff is on the distal end of the tube and sits in the oesophagus. When inflated gastric content is blocked from escape. The second tube ends before the oesophagus and has a number of holes in it to allow ventilation of the trachea. If the device is inadvertently pushed into the larynx it can be simply ventilated like an endotracheal tube through what should have been the gastric opening. Again, if airway reflexes return the device will have to be removed.
Jeff Kenneally – www.Prehemt.com