airway management techniques such as bag-valve-mask ventilation, the laryngeal mask airway and the combitube. however, recent higher quality studies have shown no survival or neurological benefit with endotracheal intubation over supraglottic airway devices (laryngeal mask or combitube). one complication—unintentional and unrecognized intubation of the esophagus—is both common (as frequent as 25% in the hands of inexperienced personnel) 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 american society of anesthesiologists (asa) closed claims project database, 266 (approximately 6%) were for airway injury. of these 266 cases, 87% of the injuries were temporary, 5% were permanent or disabling, and 8% resulted in death. difficult intubation, age older than 60 years, and female gender were associated with claims for perforation of the esophagus or pharynx. early signs of perforation were present in only 51% of perforation claims, whereas late sequelae occurred in 65%. during the sars and covid-19 pandemics, tracheal intubation has been used with a ventilator in severe cases where the patient struggles to breathe. performing the procedure carries a risk of the caregiver becoming infected. alternatives 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. 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 risk-benefit ratio is favorable (i.e., the risks associated with an unprotected airway are believed to be less than the risks of intubating the trachea). airway management can be classified into closed or open techniques depending on the system of ventilation used. tracheal intubation is a typical example of a closed technique as ventilation occurs using a closed circuit. several open techniques exist, such as spontaneous ventilation, apnoeic ventilation or jet ventilation. each has its own specific advantages and disadvantages which determine when it should be used. 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. history tracheotomy the earliest known depiction of a tracheotomy is found on two egyptian tablets dating back to around 3600 bc. the 110-page ebers papyrus, an egyptian medical papyrus which dates to roughly 1550 bc, also makes reference to the tracheotomy. tracheotomy was described in the rigveda, a sanskrit text of ayurvedic medicine written around 2000 bc in ancient india. the sushruta samhita from around 400 bc is another text from the indian subcontinent on ayurvedic medicine and surgery that mentions tracheotomy. asclepiades of bithynia (c. 124–40 bc) is often credited as being the first physician to perform a non-emergency tracheotomy. galen of pergamon (ad 129–199) clarified the anatomy of the trachea and was the first to demonstrate that the larynx generates the voice. in one of his experiments, galen used bellows to inflate the lungs of a dead animal. ibn sīnā (980–1037) described the use of tracheal intubation to facilitate breathing in 1025 in his 14-volume medical encyclopedia, the canon of medicine. in the 12th century medical textbook al-taisir, ibn zuhr (1092–1162)—also known as avenzoar—of al-andalus provided a correct description of the tracheotomy operation. the first detailed descriptions of tracheal intubation and subsequent artificial respiration of animals were from andreas vesalius (1514–1564) of brussels. in his landmark book published in 1543, de humani corporis fabrica, he described an experiment in which he passed a reed into the trachea of a dying animal whose thorax had been opened and maintained ventilation by blowing into the reed intermittently. antonio musa brassavola (1490–1554) of ferrara successfully treated a patient with peritonsillar abscess by tracheotomy. brassavola published his account in 1546; this operation has been identified as the first recorded successful tracheotomy, despite the many previous references to this operation. towards the end of the 16th century, hieronymus fabricius (1533–1619) described a useful technique for tracheotomy in his writings, although he had never actually performed the operation himself. in 1620 the french surgeon nicholas habicot (1550–1624) published a report of four successful tracheotomies. in 1714, anatomist georg detharding (1671–1747) of the university of rostock performed a tracheotomy on a drowning victim. despite the many recorded instances of its use since antiquity, it was not until the early 19th century that the tracheotomy finally began to be recognized as a legitimate means of treating severe airway obstruction. in 1852, french physician armand trousseau (1801–1867) presented a series of 169 tracheotomies to the académie impériale de médecine. 158 of these were performed for the treatment of croup, and 11 were performed for "chronic maladies of the larynx". between 1830 and 1855, more than 350 tracheotomies were performed in paris, most of them at the hôpital des enfants malades, a public hospital, with an overall survival rate of only 20–25%. this compares with 58% of the 24 patients in trousseau's private practice, who fared better due to greater postoperative care. in 1871, the german surgeon friedrich trendelenburg (1844–1924) published a paper describing the first successful elective human tracheotomy to be performed for the purpose of administration of general anesthesia. in 1888, sir morell mackenzie (1837–1892) published a book discussing the indications for tracheotomy. in the early 20th century, tracheotomy became a life-saving treatment for patients affected with paralytic poliomyelitis who required mechanical ventilation. in 1909, philadelphia laryngologist chevalier jackson (1865–1958) described a technique for tracheotomy that is used to this day. laryngoscopy and non-surgical techniques the laryngoscopy. from garcía, 1884 in 1854, a spanish singing teacher named manuel garcía (1805–1906) became the first man to view the functioning glottis in a living human. in 1858, french pediatrician eugène bouchut (1818–1891) developed a new technique for non-surgical orotracheal intubation to bypass laryngeal obstruction resulting from a diphtheria-related pseudomembrane. in 1880, scottish surgeon william 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 with chloroform. in 1895, alfred kirstein (1863–1922) of berlin first described direct visualization of the vocal cords, using an esophagoscope he had modified for this purpose; he called this device an autoscope. 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. jackson introduced a new laryngoscope blade that incorporated a component that the operator could slide out to allow room for passage of an endotracheal tube or bronchoscope. also in 1913, new york surgeon henry h. janeway (1873–1921) published results he had achieved using a laryngoscope he had recently developed. another pioneer in this field was sir ivan whiteside magill (1888–1986), who developed the technique of awake blind nasotracheal intubation, the magill forceps, the magill laryngoscope blade, and several apparati for the administration of volatile anesthetic agents. the magill curve of an endotracheal tube is also named for magill. sir robert macintosh (1897–1989) introduced a curved laryngoscope blade in 1943; the macintosh blade remains to this day the most widely used laryngoscope blade for orotracheal intubation. between 1945 and 1952, optical engineers built upon the earlier work of rudolph schindler (1888–1968), developing the first gastrocamera. in 1964, optical fiber technology was applied to one of these early gastrocameras to produce the first flexible fiberoptic endoscope. initially used in upper gi endoscopy, this device was first used for laryngoscopy and tracheal intubation by peter murphy, an english anesthetist, in 1967. the concept of using a stylet for replacing or exchanging orotracheal tubes was introduced by finucane and kupshik in 1978, using a central venous catheter. by the mid-1980s, the flexible fiberoptic bronchoscope had become an indispensable instrument within the pulmonology and anesthesia communities. the digital revolution of the 21st century has brought newer technology to the art and science of tracheal intubation. several manufacturers have developed video laryngoscopes which employ digital technology such as the cmos active pixel sensor (cmos aps) to generate a view of the glottis so that the trachea may be intubated.