The patient is placed in the tracheostomy position with a bag of saline behind the neck. The skin is cleaned with antiseptic and toweled up. The neck is palpated and infiltrated with local anesthetic (currently bupivacaine 0.5 per cent with 1:2000 ephedrine) along the line of insertion. The operator should stand at the head of the patient, not the side. A mounted needle is then stabbed into the midline of the cricothyroid membrane and air is aspirated into the local anesthetic solution, after which 2 ml are injected into the trachea. This prevents a dangerous coughing attack which encourages bleeding and emphysema. A wire is then threaded down the needle, which is angled to direct the wire down rather than across the trachea. The needle is removed. A dilator is inserted and removed. A moist swab placed over the operation site will be required to stop the air leak and spraying of blood which can be alarming. The mounted minitracheostomy tube is now threaded over the wire and should pass into the trachea (Fig.: 1). The step in size between the tube and the dilator sometimes causes a failure to thread easily. A slight screwing action will usually overcome this. The inner dilator is now removed, the tube is in position, air is aspirated again into a fluid-filled syringe, and a suction catheter is passed into the trachea to demonstrate that there is no obstruction and secretions can be removed. If this cannot be done, the tube is incorrectly placed. If the patient has a bulky neck, it is possible to miss the cricothyroid membrane altogether which can result in a high tracheal insertion, but this does not cause any additional difficulties. A failure rate of 1 per cent can be expected. Calcification of the membrane or a very short fat neck are likely to make insertion impossible. Studies of the anatomy of the adult larynx show that a small cricothyroid membrane, normally between 5 and 9 mm, may prevent tube insertion. Insertion using undue force can result in late subglottic stenosis.
Fig. 1 Minitracheostomy tube, with neck flange folded, mounted on an internal dilator.
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