Factores predictivos de brote o aumento de actividad de la enfermedad

British anaesthetists were aware of the advances made by their American colleagues and had made their own contributions. Dr Ivan Whiteside Magill (1888 – 1986) was the leading proponent in Britain of endotracheal anaesthesia. In the United States, the main stimulus for the development of endotracheal anaesthesia and IPPR had been the need to solve the pneumothorax problem and the need to support the patient‘s respiration when using the respiratory depressant anaesthetic cyclopropane. In England, Magill was faced with a different problem; when he was posted in 1919 to the Queen‘s Hospital for Facial and Jaw Injuries in Sidcup, Kent, Magill was faced with the problems of maintaining a clear airway when the surgeons were

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Cournand A, Motley HL, Werko L, Richards DW. Physiological studies of the effects of intermittent positive pressure breathing on cardiac output in man. Am J Physiol. 1948;152: 162-74.

operating on the face of soldiers injured during the First World War (1914 – 1918). The usual anaesthetic for face and jaw operations was oil and ether administered per rectum.

Magill and his colleague Dr E S Rowbotham instituted a series of improved methods, progressing from insufflation (i.e. blowing a stream of air and ether) into the larynx (the emerging blast of gas sprayed the unfortunate surgeon with ether and blood) to ‗blind‘ intubation of the trachea, skilfully introducing the tracheal tube through the nose without seeing the larynx.89 90 The same year he wrote of endotracheal anaesthesia: ‗Within recent years the advantages of the method have become widely known. Surgeons are increasingly anxious to avail themselves of these advantages and many expert anaesthetists in England now employ the method as a routine for operations which formerly involved many anaesthetic difficulties.‘91

This may be interpreted as a statement that endotracheal anaesthesia was widely practiced, but Magill used the qualification ‗expert‘; most anaesthetics were not given by experts at that time. Magill‘s next sentence acknowledged this: ‗Nevertheless, in some hospitals endotracheal anaesthesia is not available‘. In the same paper he described endotracheal intubation through the mouth. ‗When the oral route is chosen I prefer to pass the tube by direct vision with the aid of a speculum. ... A self contained battery in the handle is a convenient means of illumination.‘ This ‗speculum‘ was a laryngoscope. By 1936 Magill was anaesthetising patients for thoracic surgery using a cuffed endotracheal tube or even one of a variety of tubes which could be passed into one of the branches of the trachea (the main bronchi) to isolate a lung infected with tuberculosis and protect the sound one.92 He was not convinced however of the safety or necessity of intermittent positive pressure respiration in patients with an open chest.

So the use of endotracheal tubes by anaesthetists was well established among expert anaesthetists in Britain sixteen years before it would be required for the

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Rowbotham ES, Magill I. Anaesthetics in the plastic surgery of the face and jaws. Proc R Soc Med. 1921;Section of anaesthetics;17–27.

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Summary of proceedings. Technique in endotracheal intubation. Br Med J. 1930;Sept. 13: 434.

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Magill IW. Techniques in endotracheal anaesthesia. Br Med J. 1930;Sept 13:817–9.

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Magill IW. Anaesthesia in thoracic surgery, with special reference to lobectomy. Proc R Soc Med. Section of anaesthetics. 1936;29:643– 53.

treatment of patient with respiratory failure in intensive care. But the use of manual ventilation of the lungs by anaesthetists came later.

The British anaesthetist Dr Michael Nosworthy (1902 – 1980) visited Guedel and his group in Los Angeles in 1939.93 As has been described above, although Waters found that his new anaesthetic depressed the patient‘s respiration, it was left to Guedel in 1940 to determine that that the degree of respiratory depression was often unacceptable and even dangerous.94 Guedel‘s paper was published in 1940 but obviously he was able to communicate his conclusions during the latter‘s visit to Los Angeles the previous year. Guedel taught that the patient‘s breathing should be completely controlled by the anaesthetist squeezing the rebreathing bag of the anaesthetic circuit and intermittently inflating the lungs. In his paper given at the Royal Society of Medicine in London in 1941 Nosworthy discussed the advantages of controlled intermittent positive pressure respiration.95 ‗Controlled‘ in this context means that the patient makes no respiratory efforts, all the lung ventilation is provided by rhythmical squeezing of the rebreathing bag. This is in contrast to ‗assisted respiration‘ in which the patient is still breathing but his respiratory efforts are inadequate and are supplemented by the anaesthetist squeezing the bag either gently or intermittently. This process has been referred to by many synonyms in the literature; passive respiration, controlled respiration and more correctly, intermittent positive-pressure ventilation of the lungs (IPPV). The later term and its acronym will be used henceforth in this thesis. It was IPPV which anaesthetists would need to use if they were to be able to treat patients with respiratory failure in intensive care. Relaxants

In 1946 Professor T Cecil Gray (1913-2008) and Dr John Halton (1903-1968) of Liverpool added one more element to the need for effective (that is intermittent positive pressure) ventilation in anaesthesia, not only for thoracic surgery but for all major surgery. They described their use of relaxants in Britain at a meeting of the Royal Society of Medicine in London.96 These agents, the prototype of which is

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Nosworthy MD. Anaesthesia in chest surgery, with special reference to controlled respiration and cyclopropane. Proc R Soc Med 1941;34:479–506.

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Guedel AE. Cyclopropane anaesthesia. Anesthesiology 1940;1:13-25.

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Nosworthy MD. Anaesthesia in chest surgery. 1941:495.

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curare, relax the muscles. One of the problems of surgery in the abdomen is that unless the muscles of the abdominal wall are very relaxed and slack, the intestines are forced out of the surgical incision and access for the surgeon to the intra- abdominal organs is difficult. Until the introduction of relaxants the abdominal muscles had to be relaxed by very deep anaesthesia, which is toxic and recovery is slow and unless it is carefully supervised, is dangerous. The injection of curare while the patient is lightly anaesthetised provides perfect surgical conditions without the disadvantages of deep anaesthesia. There is a catch; curare and its congeners do not only relax the muscles of the abdominal wall, they relax all muscles including those of respiration. In a second paper in 1952, Gray, this time with Jackson Rees, wrote ‗As a result of the respiratory depression subsequent upon adequate doses of the relaxant agents there has been no hesitation in resorting to completely controlled respiration for the cases in which this technique has been employed.‘ 97

Perhaps surprisingly, the ‗adoption very widely‘ of relaxants and controlled respiration did not lead to widespread development of automatic respirators. Anaesthetists were prepared to use manual ventilation of the lungs for the few hours necessary for most operations. The ‗feel‘ of the bag and the resistance of the lung to inflation gave the anaesthetist an idea of how relaxed the patient was. He or she could interrupt the movement of the lungs for a minute or two to allow the surgeon to do a delicate part of the operation. A partnership between the surgeon and the anaesthetist developed, the latter watching the progress of the operation and anticipating the need for more gentle respiration, or for more inflation pressure to ensure the lung was fully inflated before closure of the chest. Most anaesthetists were resigned to the need to ventilate the lungs by hand during anaesthesia for surgery.

One anaesthetist thought differently, and as a result an IPPR machine, the Blease Pulmoflator (P1) became the first commercially available in Britain in 1950. The strange history of its designer John (―Jack‖) Blease has been described by McKenzie.98 A self-taught engineer and successful racer of motor cycles which he built himself, Blease made parts for an anaesthetic machine designed by a friend, Dr Henry Roberts, a general practitioner who was also an anaesthetist at the Liverpool

1946;39:400-10.

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Gray TC, Rees J G. The role of apnoea in major surgery. Br Med J. 1952;2:891-92.

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Dental Hospital. When his friend died suddenly, Blease took over his role as dental anaesthetist and became highly skilled at the art. Although anaesthesia is generally the preserve of registered medical practitioners in the UK, dental anaesthesia was for many years an exception, being regularly administered by dentists or even persons with no qualifications at all. In the early 1940s Blease was appointed Emergency Anaesthetist to Birkenhead General Hospital, Merseyside and even anaesthetised for thoracic surgery. In 1941 he designed a lung ventilator which was tested on patients with the help of Dr John Halton, the anaesthetist who with Cecil Gray introduced the modern use of relaxants.99 After several prototype Pulmoflators, the first ventilator freely available commercially in Britain, the Blease Pulmoflator (P1) was launched in 1950. Over five years about 200 were produced.

In the first half of the twentieth century Janeway had intubated the trachea with a cuffed endotracheal tube, and had applied positive pressure to the lungs intermittently. Waters had introduced cyclopropane which was an excellent anaesthetic but a powerful respiratory depressant. He had also introduced a carbon dioxide absorption rebreathing circuit. Guedel had taught that intermittent positive pressure ventilation of the lungs (he used the term ‗passive respiration‘) was necessary in deep cyclopropane anaesthesia. He had shown that over-ventilation was relatively innocuous. Cournand and his colleagues had shown how to ventilate the lungs by intermittent positive pressure ventilation without disturbing the circulation. Ibsen was able to demonstrate in 1952 that application of these techniques reduced the mortality in bulbo-spinal paralysis due to polio.

In Great Britain by 1952 endotracheal intubation and IPPV were in use by British anaesthetists and had been said to be necessary not only in thoracic or facial surgery but in routine abdominal surgery. There was even a perfectly effective automatic lung ventilator available. It might be expected that British anaesthetists would be ready to introduce intensive care by using these techniques to treat respiratory failure due to polio and other diseases. However for several years after 1952, few anaesthetists participated in intensive care in England and Wales. The care of patients with respiratory failure continued to be undertaken for several years by those who had had that responsibility before 1952-3; usually the epidemiologists and

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specialists in infectious diseases, with or sometimes without the help of anaesthetists. The reasons for the apparent disinterest among anaesthetists will be discussed in the next chapter.