|Oesophageal intubation may occur if the tube is not seen to pass between the vocal folds. End-tidal CO2 monitoring and auscultation is essential to confirm correct placement of the tube into the trachea.
There may sometimes be difficulty in deciding whether the tube has been correctly placed: if there is any doubt, the tube should be withdrawn and re-introduced.
|Endobronchial intubation occurs if too long a tube is used and inserted into one of the mainstem bronchi. The un-intubated lung does not contribute to gas exchange, and the large volume of blood flowing through this lung results in a substantial right-to-left shunt.
Signs are those of arterial hypoxaemia, including cyanosis and laboured breathing. In addition, uptake of the inhalation anaesthetic agent may be impaired, resulting in an unexpectedly light plane of anaesthesia.
This problem may be avoided by trimming of the tube to the correct length and securing it firmly. If too long a tube is used and it is tied around the back of the patient's neck, movement of the tube during surgery may move the tip of the tube into a bronchus.
|Impaction of the tip of the tube against the tracheal wall may result in respiratory obstruction, particularly where the trachea contains a sharp bend, such as the thoracic inlet.
|The Murphy eye, incorporated into many modern tubes, permits airflow to take place, even if this has occurred.
|Herniation of the cuff over the lumen of the tube may occur if the cuff of an old, perished tube is over-inflated. This, again, will cause respiratory obstruction.
|Compression of the lumen of the tube by the cuff may be caused by over-inflation of the cuff or by gradual diffusion of nitrous oxide onto the cuff during the course of anaesthesia. This problem is more common when silicone rubber tubes are used.
|Stretching of the tracheal wall may be caused by over-inflation of the cuff. This may lead to tracheitis, pressure necrosis of the tracheal wall or tracheal rupture.
Fires are a danger associated with the increasing use of lasers for airway and oral surgery. Steps which may be taken to reduce this extremely serious hazard include:
- Using special laser tubes, which may be made of jointed metal or clear plastic (with no radiopaque strip).
- Wrapping exposed portions of the tube with aluminium tape.
- Use of helium-oxygen mixtures which are less supportive of combustion than oxygen alone or oxygen-nitrous oxide mixtures.
would like to thank Dr Guy Watney for allowing the reproduction of his images for this educational resource.