Abstract
‘The method by which oxygen is administered is of great importance. A well-ventilated oxygen chamber or tent seems preferable to other methods.’ 1 Alvan Barach, May 1934.
In April 1915, a 34-year-old sergeant in the British Army was among the thousands of allied troops attacked with chlorine gas during the second Battle of Ypres. While he survived, and ‘expected to recover in a day or two’, the previously healthy infantryman, who ‘had done heavy work all his life, and was a good athlete, having rowed and swum in races’, was left with persistent breathlessness, headache and chest tightness. 2
In the months that followed, similar chronic sequelae were increasingly recognised in those who had been poisoned by gas ‘either in battle, or in the manufacture of munitions of war.’ 3 Since many of these symptoms were identical to those experienced at high altitude, it was postulated that they might improve with supplemental oxygen therapy. 2
Beginning in July 1917, Joseph Barcroft and colleagues at the University of Cambridge Physiological Laboratory assessed the effects of the continuous administration of 40%–50% oxygen in 26 ‘chronically gassed’ patients. Treatment was delivered in an oxygen chamber, 1000 cubic feet in capacity, which was constructed from sheets of plate glass, supported by an iron frame. The chamber contained three beds and was fitted with air locks, as well as scrubbers containing soda lime and calcium chloride for the removal of carbon dioxide and water vapour respectively. Patients were enclosed from 1700 h to 1000 h, for five consecutive days, following which all but two reported symptomatic improvement.2,3 Barcroft later explained: ‘Our motivation for using this type of administration was merely that it was the simplest. The whole treatment being experimental we desired that the patient be subjected to only one altered condition of life – namely, the composition of the atmosphere which he breathed. For this reason, we avoided all types of apparatus for the administration of oxygen through a mask or otherwise, considering that a second variable was introduced.’
3
Purpose-built oxygen chambers were subsequently commissioned at several centres, including the Hospital of the Rockefeller Institute for Medical Research, New York, 6 Guy’s Hospital, London, 7 and the Mayo Clinic, Rochester, Minnesota. 8 Although these were widely perceived as ‘the ideal way to treat anoxaemia from the standpoint of effectiveness and comfort’, 9 the costs of construction and operation were high, 10 and they were ‘obviously impracticable for widespread use.’ 9
First described by Leonard Hill at a meeting of the Physiological Society in March 1921, 11 the oxygen tent possessed many of the advantages of a chamber with the additional benefits of portability and decreased expense. 12 Hill’s original design was intended ‘for the convenient administration of oxygen to patients, who will not, or cannot, put up with the use of a mask.’ 11 Fashioned from ‘balloon material’ which incorporated celluloid windows, the tent was suspended above the head of the bed using metal rods, then tucked under the mattress at the back and sides, and within the fold of sheet and blanket in front of the patient. Oxygen was delivered from a cylinder at 5l/min (maintaining an ambient concentration of 35%–37%) and the air within the tent continuously circulated through a cartridge of soda lime using the fan from a vacuum cleaner.
Lacking any means of cooling or dehumidifying the oxygen-enriched atmosphere, the interior of Hill’s ‘simple oxygen bed tent’ quickly became warm and stuffy, and several attempts were made to improve the apparatus.13,14 In 1926, Alvan Barach, from the Department of Medicine, Columbia University College of Physicians and Surgeons, New York, described ‘a new oxygen tent’ in which the air was circulated over ‘chunks of ice, the size of a man’s fist or larger.’ 15 This provided an effective means of cooling and drying the air, and became a common feature of many devices.16–18
Making extensive use of his oxygen tent to treat patients with severe pneumonia, 19 Barach discovered that carbon dioxide partly diffused through the rubberised fabric of the tent and in part dissolved on the watery surface of the melting ice. 20 This proved sufficient to wash out most of the carbon dioxide exhaled by the patient and, in the majority of cases, obviated the need to utilise soda lime. 21
During the late 1920s and early 1930s commercial manufacturers, including the McKesson Appliance Company, 17 continued to refine the design of oxygen tents, and by December 1932, some models were considered ‘almost as good as a chamber.’ 22 Despite these advances, their employment required considerable care and attention. At the Presbyterian Hospital, New York, every device was inspected, and the oxygen and carbon dioxide concentration tested, at least three times daily by one of two technicians who had been specially trained for this work. 23 They also required frequent maintenance and enforcement of strict fire precautions. Nevertheless, fires were not infrequent, often precipitated by patients lighting cigarettes.24–26
In 1943, a Committee on Public Health Relations of the New York Academy of Medicine published the first Standards of effective administration of inhalational therapy. These noted that ‘the most comfortable method of providing oxygen therapy, next to the use of the oxygen room, is in a tent with a pliofilm or other transparent canopy.’ 27 While a second report by the Committee, published in September 1950, continued to advocate tents as ‘a comfortable and effective means of administering 50–60% oxygen’, 28 their drawbacks led to their disappearance in the decade that followed.