If all other techniques to obtain a patent airway fail, then the patient is likely to rapidly deteriorate, and suffer a cardiac arrest due to hypoxia. Rapid and decisive intervention is therefore required. A surgical airway is potentially life saving in this situation. The two surgical airway techniques taught on this course are needle cricothyroidotomy and surgical cricothyroidotomy.
The needle cricothyroidotomy is a technique to insert a cannula through the cricothyroid membrane into the trachea. This membrane is located in the anterior neck, below the easily palpated thyroid cartilage, and above the cricoid ring. A syringe should be attached to the back of a large bore cannula. This cannula is inserted through the cricothyroid membrane, at a 45 degree angle facing caudally. Once the tip of the cannula lies in the trachea, air can be freely aspirated in to the syringe.
At this point the cannula should be advanced forward over the needle and the needle removed. The cannula then needs to be attached a high flow oxygen source to provide intermittent oxygenation. There are several techniques to achieve this. Perhaps the most efficient way to do this is to attach a 3 way tap between the cannula and the oxygen tubing attached to one of the other ports. This will leave one port open which should be used to provide intermittent oxygenation to the patient. This is achieved by occluding the port for 1 second and then opening it for 4 seconds. This is then repeated in a cyclical manner, so that oxygen is being driven into the patient for 1 second out of every 5.
This technique does not ventilate since it does not allow for gas exchange. Instead, it allows for oxygenation of the patient. For this reason, this technique is only a temporising measure and will usually allow approximately 20-30 minutes before a more definitive procedure should be undertaken. This window can be life saving, and the value of this procedure should not be underestimated.
Potential complications of this procedure are numerous and by understanding the local anatomy, the practitioner will be able to understand and anticipate potential problems. Complications include (but are not limited to) malposition of the cannula (with subsequent emphysema, haemorrhage or oesophageal perforation), hypoventilation, barotrauma and thyroid trauma.
This technique involves a surgical incision through the cricothyroid membrane to allow passage of a more definitive airway device. This is ideally with size 6.0 cuffed endotracheal tube.
Since this provides a larger bore than the cannula of needle cricothyroidotomy, it is possible to provide ventilation, not simply oxygenation. However, since a larger incision is required, there is a greater risk of complication.