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Endotracheal tubes and intubation

Tubes are placed in the trachea to overcome an obstruction, to facilitate ventilation, especially when controlled, and to allow the anesthetist access to the airway while distanced from the operative site. They are necessary in intrathoracic surgery where intermittent positive pressure is applied to overcome the problem of collapsing lungs when the chest is open. Tracheostomy has been described for relieving upper airway obstruction since Asclepiades in 100 BC. It was used for the treatment of quinsy (Cornelius Celsus AD 14, Pedro Virgili C18). Chevalier Jackson, who also designed a laryngoscope, popularized tracheotomy for the relief of obstruction (1909) (1). In 1780, Chaussier introduced the concept of laryngeal intubation for asphyxia of the newborn. Diphtheria was a rampant killer during epidemics. Between 1879 and 1884, Joseph O’Dwyer, a physician at the New York Foundling Hospital developed a set of metal laryngeal tubes and special forceps to insert them into the larynx in cases of diphtheria. Many children died from this disease, particularly when a membrane developed over the larynx resulting in suffocation. His aim was to use a laryngeal tube to replace the need for a tracheostomy which was often a bloody procedure performed without anesthesia. He began experimenting with his ideas in 1879 and took some years to perfect the tubes. They had to fit through the larynx, not prevent epiglottic closure, and allow free passage of air and coughing up of secretions. Initially, they were too short and could be coughed out so he lengthened them and made a widening which prevented their easy expulsion (Figure 1). Diphtheria was a dangerous disease. In 1880, 1969 of 5022 patients (39%) with diphtheria in New York and Boston died. In a compilation of 21 853 cases of obstructive diphtheritic croup reported before 1887 from UK, USA, France, and Germany who had tracheostomy, the recovery rates were 24–32 percent. The results depended on the expertise of the operator and the death rate was higher in children under three years old. The introduction of diphtheria antitoxin in 1895 was one of the great advances in preventative medicine, initially reducing the mortality to one-third of the previous figure. Progressively, the mortality decreased, so that survival was over 90 percent. In 1927, F. Scholes, at Fairfield Infectious Diseases Hospital in Melbourne, reported a series of 1275 cases where these tubes were used with great success. Tracheotomy continued to be used in children until polyvinyl chloride (PVC) tubes were introduced about 1960. The introduction of prolonged nasotracheal intubation (1962) contributed to the evolution of pediatric intensive care. Various tubes have been used for anesthesia in children. The red rubber tube was widely used but caused irritation if left in for too long. One variant, developed by Dicky Salt, the technician in the Nuffield Department in Oxford, was the Oxford tube which was bent at a right angle at the back of the pharynx at the appropriate distance from the larynx so that it would lie correctly in the larynx. The tube was slightly thicker to prevent kinking but narrowed slightly as it approached the end where it passed through the larynx. This could create a hazard from pressure on the mucosa if it was inadvertently inserted too far. Small babies have a narrow larynx. The Cole tube had a wide lumen to allow free flow of gas but it narrowed for the last 2–3 cms so that it could fit a narrow larynx. The reason for this relates to Pouisseuille’s Pediatric Anesthesia ISSN 1155-5645