Tracheal intubation (usually simply referred to as intubation), an invasive medical procedure, is the placement of a flexible plastic catheter into the trachea. For millennia, tracheotomy was considered the most reliable (and most risky) method of tracheal intubation. By the late 19th century, advances in the sciences of anatomy and physiology, as well as the beginnings of an appreciation of the germ theory of disease, had reduced the morbidity and mortality of this operation to a more acceptable rate. Also in the late 19th century, advances in endoscopic instrumentation had improved to such a degree that direct laryngoscopy had finally become a viable means to secure the airway 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 of anesthesia, critical care medicine, emergency medicine, gastroenterology, pulmonology and surgery.
Tracheotomy
The earliest known depiction of a tracheotomy is found on two Egyptian tablets dating back to circa 3600 BC. The 110-page Ebers Papyrus, an Egyptian medical papyrus that dates to around 1550 BC, also refers to the tracheotomy. Tracheotomy was described in an ancient Indian scripture, the Rigveda: 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." The Sushruta Samhita () is another text from the Indian subcontinent on ayurvedic medicine and surgery that mentions tracheotomy.
The Greek physician Hippocrates (–) condemned the practice of tracheotomy. Warning against the unacceptable risk of death from inadvertent laceration of the carotid artery during tracheotomy, Hippocrates also cautioned that "The most difficult fistulas are those that occur in the cartilaginous areas." Homerus of Byzantium is said to have written of Alexander the Great (356–323 BC) saving a soldier from asphyxiation by making an incision with the tip of his sword in the man's trachea.
Despite the concerns of Hippocrates, Galen of Pergamon (129–199) and Aretaeus of Cappadocia (both of whom lived in Rome in the 2nd century AD) credit Asclepiades of Bithynia (–40 BC) as being the first physician to perform a non-emergency tracheotomy. However, Aretaeus warned against the performance of tracheotomy because he believed that incisions made into the tracheal cartilage were prone to secondary wound 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". 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 a transverse incision be made between the third and fourth tracheal rings for the treatment of life-threatening airway obstruction. Antyllus wrote that tracheotomy was not effective however in cases of severe laryngotracheobronchitis because the pathology was distal to the operative site. Antyllus' original writings were lost, but they were preserved by Oribasius (–400) and Paul of Aegina (–690), both of whom were Greek physicians as well as historians. Galen clarified the anatomy of the trachea and was the first to demonstrate that the larynx generates the voice. 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.
During the Middle Ages, scientific discoveries were few and far between in much of Europe. However, the scientific culture flourished in other parts of the world. In 1000, Abu al-Qasim al-Zahrawi (936-1013), an Arab who lived in Al-Andalus, published the 30-volume Kitab al-Tasrif, the first illustrated work on surgery. He never performed a tracheotomy, but he did treat a slave girl who had cut her own throat in a suicide attempt. Al-Zahrawi (known to Europeans as Albucasis) sewed up the wound and the girl recovered, thereby proving that an incision in the larynx could heal. Circa 1020, Ibn Sīnā (980–1037) described the use of tracheal intubation in The Canon of Medicine to facilitate breathing. In the 12th century medical textbook Al-Taisir, Ibn Zuhr (1091–1161) of Al-Andalus (also known as Avenzoar) provided an anatomically correct description of the tracheotomy operation.