Definition

Endotracheal intubation is the placement of a tube into the trachea (windpipe) in order to maintain an open airway in patients who are unconscious or unable to breathe on their own. Oxygen, anesthetics, or other gaseous medications can be delivered through the tube.

Purpose

Specifically, endotracheal intubation is used for the following conditions:

• respiratory arrest
• respiratory failure
• airway obstruction
• need for prolonged ventilatory support
• Class III or IV hemorrhage with poor perfusion
• severe flail chest or pulmonary contusion
• multiple trauma, head injury and abnormal mental status
• inhalation injury with erythema/edema of the vocal cords
• protection from aspiration

Description

To begin the procedure, an anesthesiologist opens the patient's mouth by separating the lips and pulling on the upper jaw with the index finger. Holding a laryngoscope in the left hand, he or she inserts it into the mouth of the patient with the blade directed to the right tonsil. Once the right tonsil is reached, the laryngoscope is swept to the midline, keeping the tongue on the left to bring the epiglottis into view. The laryngoscope blade is then advanced until it reaches the angle between the base of the tongue and the epiglottis. Next, the laryngoscope is lifted upwards towards the chest and away from the nose to bring the vocal cords into view. Often an assistant has to press on the trachea to provide a direct view of the larynx. The anesthesiologist then takes the endotracheal tube, made of flexible plastic, in the right hand and starts inserting it through the mouth opening. The tube is inserted through the cords to the point that the cuff rests just below the cords. Finally, the cuff is inflated to provide a minimal leak when the bag is squeezed. Using a stethoscope, the anesthesiologist listens for breathing sounds to ensure correct placement of the tube.

Preparation

For endotracheal intubation, the patient is placed on the operating table lying on the back with a pillow under the head. The anesthesiologist wears gloves, a gown and goggles. General anesthesia is administered to the patient before starting intubation.

Risks

The anesthesiologist should evaluate and follow the patient for potential complications that may include edema; bleeding; tracheal and esophageal perforation; pneumothorax (collapsed lung); and aspiration. The patient should be advised of the potential signs and symptoms associated with life-threatening complications of airway problems. These signs and symptoms include but are not limited to sore throat, pain or swelling of the face and neck, chest pain, subcutaneous emphysema, and difficulty swallowing.

Normal results

The endotracheal tube inserted during the procedure maintains an open passage through the upper airway and allows air to pass freely to and from the lungs in order to ventilate them.

Alternatives

Alternatives to endotracheal intubation include:

• Esophageal tracheal combitube (ETC). The ETC is a double-lumen tube, combining the function of an esophageal obturator airway and a conventional endotracheal airway. The esophageal lumen has an open upper end, perforations at the pharyngeal level, and a closed distal end. The tracheal lumen has open ends. The lumens are separated by a wall and each is linked via a short tube with a connector. An oropharyngeal balloon serves to seal the oral and nasal cavities after insertion. At the lower end, a second cuff serves to seal either the trachea or esophagus.
• Laryngeal mask airway (LMA). The LMA consists of an inflatable silicone ring attached diagonally to a flexible tube. The ring forms an oval cushion that fills the space around and behind the larynx. It achieves a low-pressure seal between the tube and the trachea without insertion into the larynx.
• Tracheostomy. A tracheostomy is a surgically created opening in the neck that allows direct access to the trachea. It is kept open with a tracheostomy tube. A tracheostomy is performed when it is not possible to intubate the patient.

See also Anesthesia evaluation.

Resources

BOOKS

Finucane, B. T., and A. H. Santora. Principles of Airway Management. New York: Springer Verlag, 2003.

Roberts, J. T. Fundamentals of Tracheal Intubation. New York: Grune & Stratton, 1983.

Stewart, C. E. Advanced Airway Management. St. Louis: Quality Medical Publishing, 2002.

PERIODICALS

Bochicchio, G. V., et al. "Endotracheal intubation in the field does not improve outcome in trauma patients who present without an acutely lethal traumatic brain injury." Journal of Trauma Injury, Infections and Critical Care 54 (February 2003): 307–311.

Erhan, E., et al. "Tracheal intubation without muscle relaxants: Remifentanil or alfentanil in combination with propofol." European Journal of Anaesthesiology 20 (January 2003): 37–43.

Udobi, K. F., E. Childs, and K. Touijer. "Acute respiratory distress syndrome." American Family Physician 67 (January 2003): 315–322.

Van de Leur, J. P., J. H. Zwaveling, B. G. Loef, and C. P. Van der Schans. "Endotracheal suctioning versus minimally invasive airway suctioning in intubated patients: A prospective randomized controlled trial." Intensive Care Medicine 186 (February 8, 2003).

ORGANIZATIONS

American Society of Anesthesiologists. 520 N. Northwest Highway, Park Ridge, IL 60068-2573. (847) 825-5586. <http://www.asahq.org/>.

OTHER

"Endotracheal intubation." Health_encyclopedia. <http://www.austin360.com/search/healthfd/shared/health/adam/ency/article/003449.html>.

"Endotracheal intubation." PennHealth. <http://www.penn health.com/ency/article/003449.htm>.

"Intubation." Discovery_Health. <http://health.discovery.com/diseasesandcond/encyclopedia/1219.htmlgt;.

Monique Laberge, Ph.D.

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. When performed improperly (e.g., unrecognized esophageal intubation), the associated complications will rapidly lead to the patient's death. 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, and again in 2005.

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.

Predicting ease of intubation

• Look externally (hx of craniofacial traumas/previous surgery)
• Evaluate 3,3,2 - three of the patient's fingers should be able to fit into his/her mouth when open, three fingers should comfortable fit between the chin and the throat, and two fingers in the thyromental distance (distance from thyroid cartilage to chin)
• Mallampati score (divides airways into four classes according to visable anatomy)
• Obstructions (stridorous breath sounds, wheezing, etc)
• Neck mobility (can patient tilt head back and then forward to touch chest)

Observational 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 tube's 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 , although some conditions require infants and children to have cuffed tubes to provide high-pressure ventilations

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 appropriate 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 assess anatomical difficulties is the Mallampati score, 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 known description on the surgical procedure of intubation was given in the 1020s by Avicenna in The Canon of Medicine in order to facilitate breathing. The first detailed report on endotracheal intubation and following artificial respiration of animals was in 1543, when Andreas Vesalius pointed out in this report that such a measure could sometimes be life-saving. It remained unnoticed however.

In 1869, the German surgeon Friedrich Trendelenburg accomplished the first successful intubation of humans for anaesthesia. He introduced the tube through a temporary tracheotomy. In 1878, the British surgeon McEwen performed the first oral intubation.

During the First World War, 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 commercially available: Miller, and Macintosh. Miller is a straight blade with a flanged-tip, Macintosh is a curved-blade and small handle.

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.
• 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.