Information about Intubation

In medicine, intubation refers to 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 the placement of a flexible plastic tube into the trachea to protect the patient's airway and provide a means of mechanical ventilation. The most common tracheal intubation is orotracheal intubation where, with the assistance of a laryngoscope, an endotracheal tube is passed through the mouth, larynx, and vocal cords, into the trachea. A bulb is then inflated near the distal tip of the tube to help secure it in place and protect the airway from blood, vomit, and secretions. Another possibility is nasotracheal intubation where a tube is passed through the nose, larynx, vocal cords, and trachea.

Extubation is the removal of the tube.

Risk vs. benefit

Tracheal intubation is a potentially dangerous invasive procedure that requires a lot of clinical experience to master.^[1] When performed improperly (e.g., unrecognized esophageal intubation), the associated complications will rapidly lead to the patient's death.^[2] Subsequently, tracheal intubation's role as the "gold standard" of advanced airway maintenance was downplayed (in favor of more basic techniques like bag-valve-mask ventilation) by the American Heart Association's Guidelines for Cardiopulminary Resuscitation in 2000,^[3] and again in 2005.^[4]

Risk management

No single method for confirming tube placement has been shown to be 100% reliable. Accordingly, the use of multiple methods to confirm correct tube placement is now the standard of care. At least one of the methods utilized should be an instrument. Waveform capnography is emerging as the gold standard instrument for the confirmation of correct tube placement and maintenance of the tube once it is in place.

Methods to confirm correct tube placement

• Direct visualization of the tube passing through the vocal cords
• Clear and equal bilateral breath sounds on auscultation of the chest
• Absent sounds on auscultation of the epigastrium
• Equal bilateral chest rise with ventilation
• Fogging of the tube
• An absence of stomach contents in the tube

Instruments to confirm correct tube placement

• Colorimetric end tidal CO₂ detector
• Waveform capnography
• Self inflating esophageal bulb
• Pulse oximetry (patients with a pulse)

Tube maintenance

The tube is secured in place with tape or an endotracheal tube holder. A cervical collar is sometimes used to prevent motion of the airway. Tube placement should be confirmed after each physical move of the patient and after any unexplained change in the patient's clinical status. Continuous pulse oximetry and continuous waveform capnography are often used to monitor the tubes correct placement.

Indications

Tracheal intubation is performed by paramedics or physicians in various medical conditions:

• 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.
• 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.
• Diagnostic manipulations of the airways such as bronchoscopy.
• Endoscopic operative procedures to the airways such as laser therapy or stenting of the bronchi.
• Patients who require respiratory support, including cardiopulmonary resuscitation.

Types of tubes

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. Special double-lumen endotracheal tubes have been developed for lung and other intra-thoracic surgery. These tubes allow one-lung ventilation while the other lung can be collapsed to make surgery easier. 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].

Techniques

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. RSI is only correctly performed using an induction agent with a 1 arm-brain circulation time. The only agents classically 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.

Another alternative is intubation of the awake patient under local anesthesia using a flexible endoscope or by other means (e.g., using a 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.

Because the life of a patient can depend on the success of an intubation, it is important to assess possible obstacles beforehand. The ease of intubation is difficult to predict. One score to asses anatomical difficulties is the Mallampati score,^[5] 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. It should however be noted that no single score or combination of scores can be trusted to detect all patients who are difficult to intubate. Therefore, persons performing intubation must be familiar with alternative techniques of securing the airways.

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.

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. The Magill curve of an endotracheal tube and the Magill pliers for positioning the tubus during nasal intubation are named after Magill.

Technology

Laryngoscope

Historically, the most common device used for intubation has been the laryngoscope. Although it has proven sufficient throughout history, many serious problems can arise from its misuse (ex. dental trauma). Newer technologies have fared better in reducing problematic incidence.

There are two styles of laryngoscopes comercially available: Miller, and Macintosh. Miller is a straight blade with a flanged-tip, Macintosh is a curved-bladesmall handle.jpg and [3]

A reduction of the proximal flange of a Miller blade decreases the blade’s effectiveness for laryngeal visualization, whereas a similar modification of a Macintosh blade increases blade-tooth distance, decreases the number of blade-tooth contacts and provides a better laryngeal view.

Fiber Optics

Another common technology used for intubation has been fiber optics. Although this system provides better visibility, it still has drawback such as inadequate controls and sporadic visibility failure. It is also considered very slow relative to the laryngoscope.

Image Sensor

The latest technology used to intubate is a computer system utilizing CMOS image sensors. Visibility failures still occur but to a lesser extent. Also, this technology is still extremely expensive and little used, but progress has been made to reduce visibility failures and costs.

References

External links

• Airway devices for intubation

Relevant journal articles

• Fridrich P, Frass M, Krenn CG, Weinstabl C, Benumof JL, Krafft P. The UpsherScope in routine and difficult airway management: a randomized, controlled clinical trial. Anesth Analg. 1997 Dec;85(6):1377-81.
• Mallampati SR, Gatt SP, Gugino LD, Desai SP, Waraksa B, Freiberger D, Liu PL. A clinical sign to predict difficult tracheal intubation: a prospective study. Can Anaesth Soc J. 1985 Jul;32(4):429-34.
• Adnet F, Borron SW, Racine SX, Clemessy JL, Fournier JL, Plaisance P, Lapandry C. The intubation difficulty scale (IDS): proposal and evaluation of a new score characterizing the complexity of endotracheal intubation. Anesthesiology. 1997 Dec;87(6):1290-7.
• Ovassapian A. Conduct of anesthesia. In: Shields TW, ed. General thoracic surgery. 4th ed.Baltimore:Williams & Wilkins, 1994:307–23.
• de Menezes Lyra R. Glottis simulator. Anesth Analg. 1999 Jun;88(6):1422-3.http://www.anesthesia-analgesia.org/cgi/reprint/88/6/1424.pdf
• Smith, N Ty. Simulation in anesthesia: the merits of large simulators versus small simulators. Current Opinion in Anaesthesiology. 13(6):659-665, December 2000.
• Kabrhel C, Thomsen TW, Setnik GS, Walls RM (2007). "Videos in clinical medicine. Orotracheal intubation". N. Engl. J. Med. 356 (17): e15. DOI:10.1056/NEJMvcm063574. PMID 17460222. 

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