Tracheal intubation

The most widely used route is orotracheal, in which an endotracheal tube is passed through the mouth and vocal apparatus into the trachea. In a nasotracheal procedure, an endotracheal tube is passed through the nose and vocal apparatus into the trachea. Other methods of intubation involve surgery and include the cricothyrotomy (used almost exclusively in emergency circumstances) and the tracheotomy, used primarily in situations where a prolonged need for airway support is anticipated.

Because it is an

Diagnostic or therapeutic manipulation of the airway (such as bronchoscopy, laser therapy or stenting of the bronchi) may intermittently interfere with the ability to breathe; intubation may be necessary in such situations.^[4]

Syndromes such as

The vast majority of tracheal intubations involve the use of a

The decision to use a straight or curved laryngoscope blade depends partly on the specific anatomical features of the airway, and partly on the personal experience and preference of the laryngoscopist. The Miller blade, characterized by its straight, elongated shape with a curved tip, is frequently employed in patients with challenging airway anatomy, such as those with limited mouth opening or a high larynx. Its design allows for direct visualization of the epiglottis, facilitating precise glottic exposure.[10] Conversely, the Macintosh blade, with its curved configuration reminiscent of the letters "C" or "J," is favored in routine intubations for patients with normal airway anatomy. Its curved design enables indirect laryngoscopy, providing enhanced visualization of the vocal cords and glottis in most adult patients.^[11]

The choice between the Miller and Macintosh blades is influenced by specific anatomical considerations and the preferences of the laryngoscopist. While the Macintosh blade is the most commonly utilized curved laryngoscope blade, the Miller blade is the preferred option for straight blade intubation. Both blades are available in various sizes, ranging from size 0 (infant) to size 4 (large adult), catering to patients of different ages and anatomies. Additionally, there exists a myriad of specialty blades with unique features, including mirrors for enhanced visualization and ports for oxygen administration, primarily utilized by anesthetists and otolaryngologists in operating room settings.^[12][10]

An intubating stylet is a malleable metal wire designed to be inserted into the endotracheal tube to make the tube conform better to the upper airway anatomy of the specific individual. This aid is commonly used with a difficult laryngoscopy. Just as with laryngoscope blades, there are also several types of available stylets,^[17] such as the Verathon Stylet, which is specifically designed to follow the 60° blade angle of the GlideScope video laryngoscope.^[18]

The Eschmann tracheal tube introducer (also referred to as a "gum elastic bougie") is specialized type of stylet used to facilitate difficult intubation.^[19] This flexible device is 60 cm (24 in) in length, 15 French (5 mm diameter) with a small "hockey-stick" angle at the far end. Unlike a traditional intubating stylet, the Eschmann tracheal tube introducer is typically inserted directly into the trachea and then used as a guide over which the endotracheal tube can be passed (in a manner analogous to the Seldinger technique). As the Eschmann tracheal tube introducer is considerably less rigid than a conventional stylet, this technique is considered to be a relatively atraumatic means of tracheal intubation.^[20][21]

The tracheal tube exchanger is a hollow catheter, 56 to 81 cm (22.0 to 31.9 in) in length, that can be used for removal and replacement of tracheal tubes without the need for laryngoscopy.^[22] The Cook Airway Exchange Catheter (CAEC) is another example of this type of catheter; this device has a central lumen (hollow channel) through which oxygen can be administered.^[23] Airway exchange catheters are long hollow catheters which often have connectors for jet ventilation, manual ventilation, or oxygen insufflation. It is also possible to connect the catheter to a capnograph to perform respiratory monitoring.

The lighted stylet is a device that employs the principle of transillumination to facilitate blind orotracheal intubation (an intubation technique in which the laryngoscopist does not view the glottis).^[24]

Originally made from latex rubber,^[30] most modern endotracheal tubes today are constructed of polyvinyl chloride. Tubes constructed of silicone rubber, wire-reinforced silicone rubber or stainless steel are also available for special applications. For human use, tubes range in size from 2 to 10.5 mm (0.1 to 0.4 in) in internal diameter. The size is chosen based on the patient's body size, with the smaller sizes being used for infants and children. Most endotracheal tubes have an inflatable cuff to seal the tracheobronchial tree against leakage of respiratory gases and pulmonary aspiration of gastric contents, blood, secretions, and other fluids. Uncuffed tubes are also available, though their use is limited mostly to children (in small children, the cricoid cartilage is the narrowest portion of the airway and usually provides an adequate seal for mechanical ventilation).^[13]

In addition to cuffed or uncuffed, preformed endotracheal tubes are also available. The oral and nasal RAE tubes (named after the inventors Ring, Adair and Elwyn) are the most widely used of the preformed tubes.^[31]

There are a number of different types of

The "armored" endotracheal tubes are cuffed, wire-reinforced silicone rubber tubes. They are much more flexible than polyvinyl chloride tubes, yet they are difficult to compress or kink. This can make them useful for situations in which the trachea is anticipated to remain intubated for a prolonged duration, or if the neck is to remain flexed during surgery. Most armored tubes have a Magill curve, but preformed armored RAE tubes are also available. Another type of endotracheal tube has four small openings just above the inflatable cuff, which can be used for suction of the trachea or administration of intratracheal medications if necessary. Other tubes (such as the Bivona Fome-Cuf tube) are designed specifically for use in laser surgery in and around the airway.[33]

No single method for confirming tracheal tube placement has been shown to be 100% reliable. Accordingly, the use of multiple methods for confirmation of correct tube placement is now widely considered to be the standard of care.^[34] Such methods include direct visualization as the tip of the tube passes through the glottis, or indirect visualization of the tracheal tube within the trachea using a device such as a bronchoscope. With a properly positioned tracheal tube, equal bilateral breath sounds will be heard upon listening to the chest with a stethoscope, and no sound upon listening to the area over the stomach. Equal bilateral rise and fall of the chest wall will be evident with ventilatory excursions. A small amount of water vapor will also be evident within the lumen of the tube with each exhalation and there will be no gastric contents in the tracheal tube at any time.^[33]

Ideally, at least one of the methods utilized for confirming tracheal tube placement will be a

Rapid sequence induction and intubation (RSI) is a particular method of induction of general anesthesia, commonly employed in emergency operations and other situations where patients are assumed to have a full stomach. The objective of RSI is to minimize the possibility of

One important difference between RSI and routine tracheal intubation is that the practitioner does not manually assist the ventilation of the lungs after the onset of general anesthesia and cessation of breathing, until the trachea has been intubated and the cuff has been inflated. Another key feature of RSI is the application of manual 'cricoid pressure' to the cricoid cartilage, often referred to as the "Sellick maneuver", prior to instrumentation of the airway and intubation of the trachea.^[34]

Named for British anesthetist Brian Arthur Sellick (1918–1996) who first described the procedure in 1961,^[46] the goal of cricoid pressure is to minimize the possibility of regurgitation and pulmonary aspiration of gastric contents. Cricoid pressure has been widely used during RSI for nearly fifty years, despite a lack of compelling evidence to support this practice.^[47] The initial article by Sellick was based on a small sample size at a time when high tidal volumes, head-down positioning and barbiturate anesthesia were the rule.^[48] Beginning around 2000, a significant body of evidence has accumulated which questions the effectiveness of cricoid pressure. The application of cricoid pressure may in fact displace the esophagus laterally^[49] instead of compressing it as described by Sellick. Cricoid pressure may also compress the glottis, which can obstruct the view of the laryngoscopist and actually cause a delay in securing the airway.^[50]

Cricoid pressure is often confused with the "BURP" (Backwards Upwards Rightwards Pressure) maneuver.^[51] While both of these involve digital pressure to the anterior aspect (front) of the laryngeal apparatus, the purpose of the latter is to improve the view of the glottis during laryngoscopy and tracheal intubation, rather than to prevent regurgitation.^[52] Both cricoid pressure and the BURP maneuver have the potential to worsen laryngoscopy.^[53]

RSI may also be used in prehospital emergency situations when a patient is conscious but respiratory failure is imminent (such as in extreme trauma). This procedure is commonly performed by flight paramedics. Flight paramedics often use RSI to intubate before transport because intubation in a moving fixed-wing or rotary-wing aircraft is extremely difficult to perform due to environmental factors. The patient will be paralyzed and intubated on the ground before transport by aircraft.

A cricothyrotomy is an incision made through the skin and cricothyroid membrane to establish a patent airway during certain life-threatening situations, such as airway obstruction by a foreign body, angioedema, or massive facial trauma.^[54] A cricothyrotomy is nearly always performed as a last resort in cases where orotracheal and nasotracheal intubation are impossible or contraindicated. Cricothyrotomy is easier and quicker to perform than tracheotomy, does not require manipulation of the cervical spine and is associated with fewer complications.^[55]

The easiest method to perform this technique is the needle cricothyrotomy (also referred to as a

Several manufacturers market prepackaged cricothyrotomy kits, which enable one to use either a wire-guided percutaneous dilational (Seldinger) technique, or the classic surgical technique to insert a polyvinylchloride catheter through the cricothyroid membrane. The kits may be stocked in hospital emergency departments and operating suites, as well as ambulances and other selected pre-hospital settings.^[60]

Tracheotomy consists of making an incision on the front of the neck and opening a direct airway through an incision in the trachea. The resulting

There are significant differences in airway anatomy and respiratory physiology between children and adults, and these are taken into careful consideration before performing tracheal intubation of any pediatric patient. The differences, which are quite significant in infants, gradually disappear as the human body approaches a mature age and body mass index.^[64]

For infants and young children, orotracheal intubation is easier than the nasotracheal route. Nasotracheal intubation carries a risk of dislodgement of

Because the airway of a child is narrow, a small amount of glottic or tracheal swelling can produce critical obstruction. Inserting a tube that is too large relative to the diameter of the trachea can cause swelling. Conversely, inserting a tube that is too small can result in inability to achieve effective positive pressure ventilation due to retrograde escape of gas through the glottis and out the mouth and nose (often referred to as a "leak" around the tube). An excessive leak can usually be corrected by inserting a larger tube or a cuffed tube.^[70]

The tip of a correctly positioned tracheal tube will be in the mid-trachea, between the

Endotrachael suctioning is often used during intubation in newborn infants to reduce the risk of a blocked tube due to secretions, a collapsed lung, and to reduce pain.[7] Suctioning is sometimes used at specifically scheduled intervals, "as needed", and less frequently. Further research is necessary to determine the most effective suctioning schedule or frequency of suctioning in intubated infants.^[7]

In newborns free flow oxygen used to be recommended during intubation however as there is no evidence of benefit the 2011 NRP guidelines no longer do.^[71]

Tracheal intubation is not a simple procedure and the consequences of failure are grave. Therefore, the patient is carefully evaluated for potential difficulty or complications beforehand. This involves taking the medical history of the patient and performing a physical examination, the results of which can be scored against one of several classification systems. The proposed surgical procedure (e.g., surgery involving the head and neck, or bariatric surgery) may lead one to anticipate difficulties with intubation.^[34] Many individuals have unusual airway anatomy, such as those who have limited movement of their neck or jaw, or those who have tumors, deep swelling due to injury or to allergy, developmental abnormalities of the jaw, or excess fatty tissue of the face and neck. Using conventional laryngoscopic techniques, intubation of the trachea can be difficult or even impossible in such patients. This is why all persons performing tracheal intubation must be familiar with alternative techniques of securing the airway. Use of the flexible fiberoptic bronchoscope and similar devices has become among the preferred techniques in the management of such cases. However, these devices require a different skill set than that employed for conventional laryngoscopy and are expensive to purchase, maintain and repair.^[72]

When taking the patient's medical history, the subject is questioned about any significant

A detailed physical examination of the airway is important, particularly:^[73]

• the range of motion of the cervical spine: the subject should be able to tilt the head back and then forward so that the chin touches the chest.
• the range of motion of the jaw (the temporomandibular joint): three of the subject's fingers should be able to fit between the upper and lower incisors.
• the size and shape of the
  lower jaw, looking especially for problems such as maxillary hypoplasia (an underdeveloped upper jaw), micrognathia (an abnormally small jaw), or retrognathia
  (misalignment of the upper and lower jaw).
• the thyromental distance: three of the subject's fingers should be able to fit between the Adam's apple and the chin.
• the size and shape of the tongue and palate relative to the size of the mouth.
• the teeth, especially noting the presence of prominent maxillary incisors, any loose or damaged teeth, or
  crowns
  .

Many classification systems have been developed in an effort to predict difficulty of tracheal intubation, including the

Tracheal intubation is generally considered the best method for airway management under a wide variety of circumstances, as it provides the most reliable means of oxygenation and ventilation and the greatest degree of protection against regurgitation and pulmonary aspiration.[2] However, tracheal intubation requires a great deal of clinical experience to master^[83] and serious complications may result even when properly performed.^[84]

Four anatomic features must be present for orotracheal intubation to be straightforward: adequate mouth opening (full range of motion of the temporomandibular joint), sufficient pharyngeal space (determined by examining the

More serious complications include laryngospasm, perforation of the trachea or esophagus, pulmonary aspiration of gastric contents or other foreign bodies, fracture or dislocation of the cervical spine, temporomandibular joint or arytenoid cartilages, decreased oxygen content, elevated arterial carbon dioxide, and vocal cord weakness.^[84] In addition to these complications, tracheal intubation via the nasal route carries a risk of dislodgement of adenoids and potentially severe nasal bleeding.^[39][40] Newer technologies such as flexible fiberoptic laryngoscopy have fared better in reducing the incidence of some of these complications, though the most frequent cause of intubation trauma remains a lack of skill on the part of the laryngoscopist.^[84]

Complications may also be severe and long-lasting or permanent, such as vocal cord damage, esophageal perforation and retropharyngeal abscess, bronchial intubation, or nerve injury. They may even be immediately life-threatening, such as laryngospasm and negative pressure pulmonary edema (fluid in the lungs), aspiration, unrecognized esophageal intubation, or accidental disconnection or dislodgement of the tracheal tube.^[84] Potentially fatal complications more often associated with prolonged intubation or tracheotomy include abnormal communication between the trachea and nearby structures such as the innominate artery (tracheoinnominate fistula) or esophagus (tracheoesophageal fistula). Other significant complications include airway obstruction due to loss of tracheal rigidity, ventilator-associated pneumonia and narrowing of the glottis or trachea.^[33] The cuff pressure is monitored carefully in order to avoid complications from over-inflation, many of which can be traced to excessive cuff pressure restricting the blood supply to the tracheal mucosa.^[85][86] A 2000 Spanish study of bedside percutaneous tracheotomy reported overall complication rates of 10–15% and procedural mortality of 0%,^[61] which is comparable to those of other series reported in the literature from the Netherlands^[87] and the United States.^[88]

Inability to secure the airway, with subsequent failure of oxygenation and ventilation is a life-threatening complication which if not immediately corrected leads to

One complication—unintentional and unrecognized intubation of the esophagus—is both common (as frequent as 25% in the hands of inexperienced personnel)[89] and likely to result in a deleterious or even fatal outcome. In such cases, oxygen is inadvertently administered to the stomach, from where it cannot be taken up by the circulatory system, instead of the lungs. If this situation is not immediately identified and corrected, death will ensue from cerebral and cardiac anoxia.

Of 4,460 claims in the

Although it offers the greatest degree of protection against regurgitation and pulmonary aspiration, tracheal intubation is not the only means to maintain a patent airway. Alternative techniques for airway management and delivery of oxygen, volatile anesthetics or other breathing gases include the laryngeal mask airway, i-gel, cuffed oropharyngeal airway, continuous positive airway pressure (CPAP mask), nasal BiPAP mask, simple face mask, and nasal cannula.^[98]

General anesthesia is often administered without tracheal intubation in selected cases where the procedure is brief in duration, or procedures where the depth of anesthesia is not sufficient to cause significant compromise in ventilatory function. Even for longer duration or more invasive procedures, a general anesthetic may be administered without intubating the trachea, provided that patients are carefully selected, and the

Spontaneous ventilation has been traditionally performed with an inhalational agent (i.e. gas induction or inhalational induction using halothane or sevoflurane) however it can also be performed using intravenous anaesthesia (e.g. propofol, ketamine or dexmedetomidine). SponTaneous Respiration using IntraVEnous anaesthesia and High-flow nasal oxygen (STRIVE Hi) is an open airway technique that uses an upwards titration of propofol which maintains ventilation at deep levels of anaesthesia. It has been used in airway surgery as an alternative to tracheal intubation.[99]

Tracheotomy

The earliest known depiction of a tracheotomy is found on two Egyptian tablets dating back to around 3600 BC.

• Intratracheal instillation

References

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• Levitan, RM (2004). The Airway Cam Guide to Intubation and Practical Emergency Airway Management (1st ed.). Wayne, Pennsylvania: Airway Cam Technologies.
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• Longe, JL, ed. (2005). "The Gale Encyclopedia of Alternative Medicine: L-R". The Gale Encyclopedia of Alternative Medicine, Volume 4: S–Z (2nd ed.). Farmington Hills, Michigan: Gale Cengage.
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• Mackenzie, M (1888). The case of Emperor Frederick III.: full official reports by the German physicians and by Sir Morell Mackenzie. New York: Edgar S. Werner.
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External links

Wikimedia Commons has media related to Tracheal intubation.

• Video of endotracheal intubation using C-MAC D-blade and bougie used as introducer.
• Videos of direct laryngoscopy recorded with the Airway Cam (TM) imaging system
• Examples of some devices for facilitation of tracheal intubation
• Free image rich resource explaining various types of endotracheal tubes
• Tracheal intubation live case 2022