Tracheal intubation (usually simply referred to asintubation), aninvasive medical procedure, is the placement of a flexible plasticcatheter into thetrachea. For millennia,tracheotomy was considered the most reliable (and most risky) method of tracheal intubation. By the late 19th century, advances in the sciences ofanatomy andphysiology, as well as the beginnings of an appreciation of thegerm theory of disease, had reduced themorbidity andmortality of this operation to a more acceptable rate. Also in the late 19th century, advances inendoscopic instrumentation had improved to such a degree that directlaryngoscopy had finally become a viable means to secure theairway by the non-surgical orotracheal route. Nasotracheal intubation was not widely practiced until the early 20th century. The 20th century saw the transformation of the practices of tracheotomy, endoscopy and non-surgical tracheal intubation from rarely employed procedures to essential components of the practices ofanesthesia,critical care medicine,emergency medicine,gastroenterology,pulmonology andsurgery.

The earliest known depiction of a tracheotomy is found on twoEgyptiantablets dating back to circa 3600 BC.^[1] The 110-pageEbers Papyrus, anEgyptian medical papyrus that dates to around 1550 BC, also refers to the tracheotomy.^[1][2] Tracheotomy was described in an ancient Indian scripture, theRigveda: the text mentions "the bountiful one who, without a ligature, can cause the windpipe to re-unite when the cervical cartilages are cut across, provided they are not entirely severed."^[2][3][4] TheSushruta Samhita (c. 400 BC) is another text from theIndian subcontinent on ayurvedic medicine and surgery that mentions tracheotomy.^[5]

TheGreek physicianHippocrates (c. 460–c. 370 BC) condemned the practice of tracheotomy. Warning against the unacceptable risk of death from inadvertent laceration of thecarotid artery during tracheotomy, Hippocrates also cautioned that "The most difficultfistulas are those that occur in the cartilaginous areas."^[6]Homerus of Byzantium is said to have written ofAlexander the Great (356–323 BC) saving a soldier fromasphyxiation by making an incision with the tip of his sword in the man's trachea.^[7]

Despite the concerns of Hippocrates,Galen ofPergamon (129–199) andAretaeus ofCappadocia (both of whom lived inRome in the 2nd century AD) creditAsclepiades of Bithynia (c. 124–40 BC) as being the first physician to perform a non-emergency tracheotomy.[8]^[9] However, Aretaeus warned against the performance of tracheotomy because he believed that incisions made into the trachealcartilage were prone to secondarywound infections and therefore would not heal. He wrote that "The lips of the wound do not coalesce, for they are both cartilaginous and not of a nature to unite".^[10][11]Antyllus, another Greek surgeon who lived in Rome in the 2nd century AD, was reported to have performed tracheotomy when treating oral diseases. He refined the technique to be more similar to that used in modern times, recommending that atransverse incision be made between the third and fourth tracheal rings for the treatment of life-threatening airway obstruction.^[10] Antyllus wrote that tracheotomy was not effective however in cases of severelaryngotracheobronchitis because thepathology was distal to the operative site. Antyllus' original writings were lost, but they were preserved byOribasius (c. 320–400) andPaul of Aegina (c. 625–690), both of whom were Greek physicians as well as historians.[10] Galen clarified the anatomy of the trachea and was the first to demonstrate that the larynx generates the voice.^[12][13] Galen may have understood the importance of artificial ventilation, because in one of his experiments he used bellows to inflate the lungs of a dead animal.^[14][15]

Circa 1020,Ibn Sīnā (980–1037) described the use of tracheal intubation inThe Canon of Medicine to facilitatebreathing.^[16] In the 12th century medical textbookAl-Taisir,Ibn Zuhr (1091–1161) of Al-Andalus (also known as Avenzoar) provided an anatomically correct description of the tracheotomy operation.^[17][18]

TheRenaissance saw significant advances in anatomy and surgery, and surgeons became increasingly open to surgery on the trachea. Despite this, the mortality rate failed to improve.^[10] From 1500 through 1832 there are only 28 known descriptions of successful tracheotomy in the literature.^[10] The first detailed descriptions on tracheal intubation and subsequentartificial respiration of animals were fromAndreas Vesalius (1514–1564) of Brussels. In his landmark book published in 1543,De humani corporis fabrica, he described an experiment in which he passed areed into the trachea of a dying animal whosethorax had been opened and maintained ventilation by blowing into the reed intermittently.^[15][19] Vesalius wrote that the technique could be life-saving.Antonio Musa Brassavola (1490–1554) ofFerrara treated a patient withperitonsillar abscess by tracheotomy after the patient had been refused bybarber surgeons. The patient apparently made a complete recovery and Brassavola published his account in 1546. This operation has been identified as the first recorded successful tracheostomy, despite many ancient references to the trachea and possibly to its opening.^[10]

Towards the end of the 16th century, anatomist and surgeonHieronymus Fabricius (1533–1619) described a useful technique for tracheotomy in his writings, although he had never actually performed the operation himself. He advised using a vertical incision and was the first to introduce the idea of a tracheostomy tube. This was a straight, shortcannula that incorporated wings to prevent the tube from advancing too far into the trachea. Fabricius' description of the tracheotomy procedure is similar to that used today.Julius Casserius (1561–1616) succeeded Fabricius as professor of anatomy at the University of Padua and published his own writings regarding technique and equipment for tracheotomy, recommending a curved silver tube with several holes in it.Marco Aurelio Severino (1580–1656), a skillful surgeon and anatomist, performed multiple successful tracheotomies during adiphtheriaepidemic inNaples in 1610, using the vertical incision technique recommended by Fabricius. He also developed his own version of a trocar.^[20]

In 1620 the French surgeonNicholas Habicot (1550–1624), surgeon of theDuke of Nemours and anatomist, published a report of four successful "bronchotomies" he had performed.^[21] One of these is the first recorded case of a tracheotomy for the removal of a foreign body, in this instance a blood clot in the larynx of a stabbing victim. He also described the first known tracheotomy performed on apediatric patient. A 14-year-old boy swallowed a bag containing 9 gold coins in an attempt to prevent its theft by ahighwayman. The object became lodged in hisesophagus, obstructing his trachea. Habicot suggested that the operation might also be effective for patients with inflammation of the larynx. He developed equipment for this surgical procedure that are similar in many ways to modern designs.

Sanctorius (1561–1636) is believed to be the first to use a trocar in the operation. He recommended leaving the cannula in place for a few days following the operation.^[22] Early tracheostomy devices are illustrated in Habicot'sQuestion Chirurgicale^[21] and Julius Casserius' posthumousTabulae anatomicae in 1627.^[23] Thomas Fienus (1567–1631), Professor of Medicine at theUniversity of Louvain, was the first to use the word "tracheotomy" in 1649, but this term was not commonly used until a century later.^[24] Georg Detharding (1671–1747), professor of anatomy at theUniversity of Rostock, treated a drowning victim with tracheostomy in 1714.^[25][26][27]

Fearful of complications, most surgeons delayed the potentially life-saving tracheotomy until a patient was moribund, despite the knowledge that irreversible organ damage would have already occurred by that time. This began to change in the early 19th century, when the tracheotomy finally began to be recognized as a legitimate means of treating severe airway obstruction. In 1832, French physicianPierre Bretonneau (1778–1862) employed tracheotomy as a last resort to treat a case ofdiphtheria.^[28] In 1852, Bretonneau's studentArmand Trousseau (1801–1867) presented a series of 169 tracheotomies (158 of which were forcroup and 11 for "chronic maladies of the larynx").^[29] In 1871, the German surgeonFriedrich Trendelenburg (1844–1924) published a paper describing the first successful elective human tracheotomy performed to administer general anesthesia.^{[30][31][32][33]} After the death of German EmperorFrederick III fromlaryngeal cancer in 1888, SirMorell Mackenzie (1837–1892) and the other treating physicians collectively wrote a book discussing the then-currentindications for tracheotomy and when the operation is absolutely necessary.^[34]

In the early 20th century, physicians began to use the tracheotomy in the treatment of patients affected by paralyticpoliomyelitis who required mechanical ventilation. The currently used surgical tracheotomy technique was described in 1909 byChevalier Jackson (1865–1958), a professor of laryngology atJefferson Medical College in Philadelphia.^[35] However, surgeons continued to debate various aspects of the tracheotomy well into the 20th century. Many techniques were employed, along with many different surgical instruments and tracheal tubes. Surgeons could not seem to reach a consensus on where or how the tracheal incision should be made, arguing whether the "high tracheotomy" or the "low tracheotomy" was more beneficial. Ironically, the newly developedinhalational anesthetic agents and techniques of general anesthesia actually seemed to increase the risks, with many patients with fatal postoperative complications. Jackson emphasised the importance of postoperative care, which dramatically reduced the mortality rate. By 1965, the surgical anatomy was thoroughly and widely understood,antibiotics were widely available and useful for treating postoperative infections and other major complications of tracheotomy had also become more manageable.

While all these surgical advances were taking place, many important developments were also taking place in the science ofoptics. Many newoptical instruments with medical applications were invented during the 19th century. In 1805, a German army surgeon namedPhilipp von Bozzini (1773–1809) invented a device he called thelichtleiter (or light-guiding instrument). This instrument, the ancestor of the modern endoscope, was used to examine theurethra, the humanurinary bladder,rectum, oropharynx and nasopharynx.^{[36][37][38][39]} The instrument consisted of a candle within a metal chimney; a mirror on the inside reflected light from the candle through attachments into the relevant body cavity.^[40] The practice of gastric endoscopy in humans was pioneered by United States Army surgeonWilliam Beaumont (1785–1853) in 1822 with the cooperation of his patientAlexis St. Martin (1794–1880), a victim of an accidental gunshot wound to the stomach.^[41] In 1853,Antonin Jean Desormeaux (1815–1882) of Paris modified Bozzini's lichtleiter such that a mirror would reflect light from akerosene lamp through a long metal channel.^[40] Referring to this instrument as anendoscope (he is credited with coining this term), Desormeaux employed it to examine the urinary bladder. However, like Bozzini's lichtleiter, Desormeaux's endoscope was of limited utility due to its propensity to become very hot during use.^[40] In 1868,Adolph Kussmaul (1822–1902) of Germany performed the firstesophagogastroduodenoscopy (adiagnostic procedure in which an endoscope is used to visualize the esophagus, stomach andduodenum) on a living human. The subject was asword-swallower, who swallowed a metal tube with a length of 47 centimeters and a diameter of 13 millimeters.^{[42][43][44][45]} On 2 October 1877,BerlinurologistMaximilian Carl-Friedrich Nitze (1848–1906) andViennese instrument maker Josef Leiter (1830–1892) introduced the first practicalcystourethroscope with an electric light source.^[46] The instrument's biggest drawback was thetungsten filamentincandescent light bulb (invented byAlexander Lodygin, 1847–1923), which became very hot and required a complicatedwater cooling system.^[40] In 1881, Polish physicianJan Mikulicz-Radecki (1850–1905) created the first rigid gastroscope for practical applications.^[47][48][49]

In 1932,Rudolph Schindler (1888–1968) of Germany introduced the first semi-flexible gastroscope.^[50] This device had numerouslenses positioned throughout the tube and a miniature light bulb at the distal tip. The tube of this device was 75 centimeters long and 11 millimeters in diameter, and the distal portion was capable of a certain degree of flexion. Between 1945 and 1952,optical engineers (particularly Karl Storz (1911–1996) of theKarl Storz GmbH company of Germany,Harold Hopkins (1918–1995) of England andMutsuo Sugiura of the JapaneseOlympus Corporation) built upon this early work, leading to the development of the first "gastrocamera".^[51][52] In 1964, Fernando Alves Martins (born 17 June 1927) of Portugal appliedoptical fiber technology to one of these early gastrocameras to produce the first gastrocamera with a flexible fiberscope.^[53][54] Initially used in esophagogastroduodenoscopy, newer devices were developed in the late 1960s for use inbronchoscopy,rhinoscopy and laryngoscopy. The concept of using a fiberoptic endoscope for tracheal intubation was introduced by Peter Murphy, an English anesthetist, in 1967.^[55] By the mid-1980s, the flexible fiberoptic bronchoscope had become an indispensable instrument within thepulmonology and anesthesia communities.^[56]

In 1854, a Spanishvocal pedagogist namedManuel García (1805–1906) became the first man to view the functioning glottis in a living human. García developed a tool that used two mirrors for which the Sun served as an externallight source.^[57] Using this device, he was able to observe the function of his own glottic apparatus and the uppermost portion of his trachea. He presented his observations at theRoyal Society of London in 1855.^[57][58]

In 1858,Eugène Bouchut (1818–1891), apediatrician from Paris, developed a new technique for non-surgical orotracheal intubation to bypass laryngeal obstruction resulting from a diphtheria-related pseudomembrane. His method involved introducing a small straight metal tube into the larynx, securing it by means of a silk thread and leaving it there for a few days until the pseudomembrane and airway obstruction had resolved sufficiently.^[59] Bouchut presented this experimental technique along with the results he had achieved in the first seven cases at theFrench Academy of Sciences conference on 18 September 1858.^[60] The members of the academy rejected Bouchut's ideas, largely as a result of highly critical and negative remarks made by the influential Armand Trousseau.^[61] Undaunted, Bouchut later introduced a set of tubes ("Bouchut's tubes") for intubation of the trachea, as an alternative to tracheotomy in cases of diphtheria.

In March 1878, Wilhelm Hack ofFreiburg published a paper describing the use of non-surgical orotracheal intubation in the removal ofvocal cord polyps.^[62] In November of that year, he published another study, this time on the use of orotracheal intubation to secure the airway of a patient with acuteglottic edema, progressively introducing sizes 3 through 11 of "Schrotter's graduated triangularvulcanite bougies" into the larynx.^[63][64] In 1880, theScottish surgeonWilliam Macewen (1848–1924) reported on his use of orotracheal intubation as an alternative to tracheotomy to allow a patient with glottic edema to breathe, as well as in the setting of general anesthesia withchloroform.^[64][65][66] All previous observations of the glottis and larynx (including those of García, Hack and Macewen) had been performed under indirect vision (using mirrors) until 23 April 1895, whenAlfred Kirstein (1863–1922) of Germany first described direct visualization of the vocal cords. Kirstein performed the first direct laryngoscopy in Berlin, using an esophagoscope he had modified for this purpose; he called this device anautoscope.^[67] The death in 1888 ofEmperor Frederick III^[34] may have motivated Kirstein to develop the autoscope.^[68]

Until 1913,oral and maxillofacial surgery was performed by maskinhalation anesthesia, topical application oflocal anesthetics to themucosa, rectal anesthesia, orintravenous anesthesia. While otherwise effective, these techniques did not protect the airway from obstruction and also exposed patients to the risk of pulmonary aspiration of blood andmucus into the tracheobronchial tree. In 1913,Chevalier Jackson was the first to report a high rate of success for the use of direct laryngoscopy as a means to intubate the trachea.^[69] Jackson introduced a new laryngoscope blade that had a light source at the distal tip, rather than the proximal light source used by Kirstein.^[70] This new blade incorporated a component that the operator could slide out to allow room for passage of an endotracheal tube or bronchoscope.^[71]

That same year,Henry H. Janeway (1873–1921) published results he had achieved using a laryngoscope he had recently developed.^[72] While practicing atBellevue Hospital inNew York City, Janeway was of the opinion that direct intratrachealinsufflation ofvolatile anesthetics would provide improved conditions forotolaryngologic surgery. With this in mind, he developed a laryngoscope designed for the sole purpose of tracheal intubation. Similar to Jackson's device, Janeway's instrument incorporated a distal light source. Unique however was the inclusion ofbatteries within the handle, a central notch in the blade for maintaining the tracheal tube in the midline of the oropharynx during intubation and a slight curve to the distal tip of the blade to help guide the tube through the glottis. The success of this design led to its subsequent use in other types of surgery. Janeway was thus instrumental in popularizing the widespread use of direct laryngoscopy and tracheal intubation in the practice of anesthesiology.^[68]

AfterWorld War I, further advances were made in the field of intratracheal anesthesia. Among these were those made by SirIvan Whiteside Magill (1888–1986). Working at theQueen's Hospital for Facial and Jaw Injuries inSidcup with plastic surgeon SirHarold Gillies (1882–1960) and anesthetist E. Stanley Rowbotham (1890–1979), Magill developed the technique of awake blind nasotracheal intubation.^{[73][74][75][76][77][78]} Magill devised a new type of angulated forceps (the Magill forceps) that are still used today to facilitate nasotracheal intubation in a manner that is little changed from Magill's original technique.^[79] Other devices invented by Magill include the Magill laryngoscope blade,^[80] as well as several apparati for the administration of volatile anesthetic agents.^[81][82][83] The Magill curve of an endotracheal tube is also named for Magill.

SirRobert Macintosh (1897–1989) also achieved significant advances in techniques for tracheal intubation when he introduced his new curved laryngoscope blade in 1943.^[84] The Macintosh blade remains to this day the most widely used laryngoscope blade for orotracheal intubation.^[85] In 1949, Macintosh published a case report describing the novel use of agum elasticurinary catheter as an endotracheal tube introducer to facilitate difficult tracheal intubation.^[86] Inspired by Macintosh's report, P. Hex Venn (who was at that time the anesthetic advisor to the British firm Eschmann Brothers & Walsh, Ltd.) set about developing an endotracheal tube introducer based on this concept. Venn's design was accepted in March 1973, and what became known as the Eschmann endotracheal tube introducer went into production later that year.^[87] The material of Venn's design was different from that of a gum elastic bougie in that it had two layers: a core of tube woven frompolyester threads and an outerresin layer. This provided more stiffness but maintained the flexibility and the slippery surface. Other differences were the length (the new introducer was 60 cm (24 in), which is much longer than the gum elastic bougie) and the presence of a 35° curved tip that let it be steered around obstacles.^[88][89] The concept of using a stylet for replacing or exchanging orotracheal tubes was introduced by Finucane and Kupshik in 1978, using acentral venous catheter.^[90]

The 20th century saw the transformation of the practices of tracheotomy, endoscopy and non-surgical tracheal intubation from rarely employed procedures to essential components of the practices of anesthesia,critical care medicine,emergency medicine,gastroenterology, pulmonology and surgery. The"digital revolution" of the 21st century has brought newer technology to the art and science of tracheal intubation. Several manufacturers have developedvideo laryngoscopes that usedigital technology such as theCMOSactive pixel sensor (CMOS APS) to generate a view of the glottis so that the trachea may be intubated. The Glidescope video laryngoscope is one example of such a device.^[91][92]

• History of anatomy
• History of general anesthesia
• History of medicine
• History of surgery

• Videos of direct laryngoscopy recorded with the Airway Cam (TM) imaging system
• Examples of some devices for facilitation of tracheal intubation
• Diagram of performance of the Sellick maneuver
• The CRIC Cricothyrotomy System from Pyng Medical Corporation
• The Rüsch QuickTrach from Teleflex Medical Corporation
• The Portex Cricothyroidotomy Kit (PCK)
• The Melker Emergency Cricothyrotomy Catheter Tray

• History of medicine
• Otorhinolaryngology

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