Intubation

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Intubation being practiced on a dummy (conventional technique using a laryngoscope).

In medicine, intubation is the placement of a tube into an external or internal orifice of the body. Although the term can refer to endoscopic procedures, it is most often used to denote tracheal intubation. Tracheal intubation is placing a tube into the trachea. The most common tracheal intubation is orotracheal intubation where an endotracheal tube is passed through the mouth, through the larynx, and into the trachea. Another possibility is nasotracheal intubation where a tube is passed through the nose.

1 Indications
2 Types of tubes
3 Techniques
4 History
5 See also
6 References
7 External links

[edit] Indications

Tracheal intubation is performed in various medical conditions:

in comatose or intoxicated patients who are unable to protect their airways. In such patients, the throat muscles may lose their tone so that the upper airways obstruct or collapse and air can not easily enter into the lungs. Furthermore, protective airway reflexes such as coughing and swallowing, which serve to protect the airways against aspiration of secretions and foreign bodies, may be absent. With tracheal intubation, airway patency is restored and the lower airways can be protected from aspiration.
in general anesthesia. In anesthetized patients spontaneous respiration may be decreased or absent due to the effect of anesthetics, opioids, or muscle relaxants. To enable mechanical ventilation, an endotracheal tube is often used, although there are alternative devices such as face masks or laryngeal mask airways.
in diagnostic manipulations of the airways such as bronchoscopy.
in endoscopic operative procedures to the airways such as laser therapy or stenting of the bronchi.
in intensive care medicine for patients who require respiratory support.
in emergency medicine, particularly for cardiopulmonary resuscitation.

[edit] Types of tubes

Image:Inserting an endotracheal tube.png

There are various types of tracheal tubes for oral or nasal intubation. Tubes may be either flexible or preformed and relatively stiff. Adult tubes have an inflatable cuff to seal the lower airways against air leakage and aspiration of secretions. Smaller pediatric tubes generally are uncuffed, due to concerns over blood flow to the trachea due to improper tube size or overinflation of the cuff[1], although some conditions require infants and children to have cuffed tubes to provide high-pressure ventilations[2].

[edit] Techniques

Image:Chapter5figure69b-nasotracheal intubation.jpg

Several techniques exist. Tracheal intubation can be performed by direct laryngoscopy (conventional technique), in which a laryngoscope is used to obtain a view of the glottis. A tube is then inserted under direct vision. This technique can usually only be employed if the patient is comatose (unconscious), under general anesthesia, or has received local or topical anesthesia to the upper airway structures (e.g., using a local anesthetic drug such as lidocaine).

Rapid sequence induction (RSI) is a variation of the standard technique for patients under anesthesia. It is performed when immediate definitive airway management through intubation is required, and especially when there is a risk of aspiration. For RSI, a short acting sedative such as etomidate, propofol, thiopental or midazolam is normally administered, followed shortly thereafter by a paralytic such as succinylcholine or rocuronium.

Another alternative is intubation of the awake patient under local anesthesia using a flexible endoscope or by other means (e.g., using a GlideScope video laryngoscope). This technique is preferred if difficulties are anticipated, as it allows the patient to breathe spontaneously throughout the procedure, thus ensuring ventilation and oxygenation even in the event of a failed intubation.

Some alternatives to intubation are

Tracheotomy - a surgical technique, typically for patients who require long-term respiratory support
Cricothyrotomy - an emergency technique used when intubation is unsuccessful and tracheotomy is not an option, typically performed by paramedics.

The ease of intubation can be predicted by the Mallampati score,<ref>Mallampati S, Gatt S, Gugino L, Desai S, Waraksa B, Freiberger D, Liu P (1985). "A clinical sign to predict difficult tracheal intubation: a prospective study.". Can Anaesth Soc J 32 (4): 429-34. PMID 4027773.</ref> which is determined by looking at the anatomy of the oral cavity and based on the visibility of the base of uvula, faucial pillars and the soft palate.

[edit] History

The first report of endotracheal intubation and following artificial respiration of animals originates from the year 1543. Andreas Vesalius pointed out in this report that such a measure could sometimes be life-saving. It remained unnoticed however.

In the year 1869 the German surgeon Friedrich Trendelenburg accomplished the first intubation of humans for anaesthesia. He introduced the tube through a temporary tracheotomy. Tracheostomy is the correct term.

In 1878 the British surgeon McEwen performed the first oral intubation.

In the years of the First World War in particular Magill and Macintosh achieved profound improvements in the application of intubation. The most used replaceable spatula of the laryngoscope is named after Macintosh. After Magill the Magill curve of an endotracheal tube and the Magill pliers for positioning the tubus during nasal intubation are named.

Th RSI is only correctly performed using an induction agent with a 1 arm-brain circulation time. The only agents classicaly used are those with 1 arm brain circulation times and are Thiopentone and etomidate. This provides the shortest induction time, and provided the appropirate dose based on body mass is used, protects against awareness during the RSI. Propofol and midazolam (in combination with other induction agents) may be used for induction where there is more time, however, propofol is increasingly being used to good effect for RSI.

[edit] See also

There are many types of laryngoscope. The main categories are those for adult use and those for child use. The blade may be curved (eg the Macintosh); straight (eg Miller blade and most paediatric blades); at a 120 degree angle as in the polio blade; or with a hinged blade tip seen in the McCoy laryngoscope which is commonly used in managing difficult intubations. The handle may be short to allow use when there is limited space, commonly seen during a rapid sequence induction of an obese individual where there is less room for both cricoid pressure application and performing laryngoscopy. The fibreoptic intubating laryngoscope is also used for intubation (its other uses including examination of the airway and bronchial tree.) Fiberoptics are particually useful when intubation is required in the presence of upper airway obstruction (eg oral abcess), tumor, angioedema, or limited neck movement. In these circumstances, the airways are carefully anaesthetised with local anaesthetic and vasoconstrictor drugs before performing awake intubation. The Magill forceps ( there are is also a Magill laryngoscope) are long and angled to allow access to the pharynx, so enabling nasogastric tube or nasotracheal tube placement and also removal of debris from the pharynx. This is a basic, minimal introduction to laryngoscopes. Other important aids to laryngoscopy include the gum elastic gougie, which may be passed through the cords and a ETT railoaded over it, and the stylet as is used in North America, although it has no advantage over the bougie.

For good summaries of this topic, see Al-Shaikh's Essentials of Anaesthetic Equipment, Fundamentals of Anaesthesia by Ted Lin, or the Difficult Airway Society website.