Endotracheal tube

  An endotracheal tube (also called an ET tube or ETT) is used in anaesthesia, intensive care and emergency medicine for airway management and mechanical ventilation. The tube is inserted into a patient's trachea in order to ensure that the airway is not closed off and that air is able to reach the lungs. The endotracheal tube is regarded as the most reliable available method for protecting a patient's airway.

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Inventor

Sir Ivan Magill or Ivan Whiteside Magill (1888-1986) was an Irish born anaesthetist who is famous for his involvement in much of the innovation and development in modern anaesthesia.

Originally a general practitioner, he accepted a post at the Queen's Hospital, Sidcup in 1919 as an anaesthetist. The hospital had been established for the treatment of facial injuries sustained in the World War I. Working with plastic surgeon Harold Gillies, he was responsible for the development of numerous items of anaesthetic equipment but most particularly the single-tube technique of endotracheal anaesthesia. This was driven by the immense difficulties of administering "standard" anaesthetics such as chloroform and ether to men with severe facial injury using masks; they would cover the operative field. Following the closure of the hospital, and the diminishing numbers of patients seen from the war era, he continued to work with Gillies in private practice but was also appointed to the Westminster and Brompton Hospitals in London.

He was Knighted by Queen Elizebeth II in 1960.

The original tubes were cut from a roll of rubber industrial tubing by his assistant, hence the natural curve of the tube. A curved metal adaptor was designed (Magill oral & nasal connectors) and a 4" black rubber connecting hose to fit to the anaesthetic circuit was adapted from an MG brake hose and named the 'catheter mount' by Magill's theatre technician at Westminster Hospital. originally, there was no inflatable cuff, the tube was packed either side of the sub-glottis by two green anaesthetic swabs, with ribbon gauze sewn on by hand to aid extraction at extubation of the ETT. Anaesthetic gel or ointment was used to lubricate the tube and provide some relief for the patients sore throat post procedure. (This author was one of the theatre technicians and can verify this technique personally- CjW)

Portex Medical (England and France) produced the first cuffless plastic 'Ivory' ET tubes, in conjunction with Dr Magilll's design later adding a cuff as manufacturing techniques became more viable, these were glued on by hand to make the famous Blue-line tube copied by many other manufacturers.

Mallincrodt GmBH developed the disposable ETT and produced a plethora of design variations, adding the 'Murphy Eye' to their tubes in case of 'accidental' placement of the tube to avoid right bronchial occlusion.

David S. Sheridan was one of the manufacturers of the American markets "disposable" plastic endotracheal tube now used routinely in surgery. Previously, red rubber tubes were used, then sterilized for re-use which carried a small a risk of infection.

He also held more than 50 medical instrument patents. Mr Sheridan died April 29 2004 in Argyle, New York at the age of 95.

Procedure

Intubation usually requires general anesthesia and muscle relaxation but can be achieved in the awake patient with local anaesthesia or in an emergency without any anaesthesia, although this is extremely uncomfortable and generally avoided in other circumstances.

It is usually performed by visualising the larynx by means of a hand-held laryngoscope that has a variety of curved and straight blades. The intubation can also be performed "blind" or with the use of the attendant's fingers (this is called digital intubation). A stylet can be used inside the endotracheal tube. The malleable metal stylet is a bendable piece of metal inserted into the ETT as to make the tube more stiff for easier insertion, this is then removed after the intubation and a ventilator or self-inflating bag is attached to the ETT. The goal is to position the end of the ETT 2 centimeters above the bifurcation of the lungs or the carina. If inserted too far into the trachea it often goes into the right main bronchus (the right main brochus is less angled than the left one).

Types

There are many types of Endotracheal tubes (ETT). Endotracheal tubes range in size from 3-10.5 mm in internal diameter (ID) - different sizes are chosen based on the patient's body size with the smaller sizes being used for paediatric and neonatal patients.

Tubes larger than 6 mm ID tend to have an inflatable cuff. Dr Robert-Shaw developed a double-lumen endo-bronchial tube for intra-thoracic surgery. These tubes allow single-lung ventilation whilst the other lung can be collapsed to make surgery easier and re-inflated as surgery finishes to check for fistulas (tears) etc. Another type of endotracheal tube has a second lumen with an opening situated right above the inflatable cuff, which can be used for suction of the nasopharngeal area and above the cuff to aid extubation (removal).

This allows a suction system to be connected to the ETT to allow for suctioning of secretions which sit above the cuff. This helps reduce the risk of chest infections in long-term intubated patients. the preferable method in these cases is to insert a shortened version of the tube via a tracheostomy, i.e. an opening into the trachea via neck. Patients can live with these respiratory aids permanently in some cases, although the majority are temporary airway adjuncts.

Mallincrodt Endotracheal tubes http://www.nellcor.com/prod/Product.aspx?S1=AIR&S2=ETT&id=120