Document 6bDJOwL8NXG0EM5kGvamr7zy6

228 CHAPTER 13 1948 Guide Limitations of Air-Conditioning Methods The results obtained with air filtration or other air conditioning pro-' cesses in the control of allergic conditions are fairly comparable to those obtained by desensitization treatment so long as the patients remain in the pollen free atmosphere. But while specific desensitization is preven tive and in a few instances curative, for all practical purposes filtration gives' only temporary relief. In mild cases sleeping in an air conditioned space may make it possible'for the individual to pass more comfortable days. With rare exceptions, the symptoms recur on exposure to pollen laden air. Moreover the usefulness of air conditioning methods is limited, because all cases are not caused by air-borne substances. Cases of bacterial asthma do not respond to treatment with filtered air. Despite these limitations air conditioning methods possess definite advantages in the simplicity of treatment, convenience, arid under certain conditions almost immediate relief ". Pollen cases are usually relieved of most of their symptoms within I to 3 hr after exposure to properly filtered air. A pollen-free atmosphere is especially valuable when desensitization has given little or no relief, and when desensitization is not advisable owing to intercurrent illness. OXYGEN THERAPY Oxygen therapy is the. principal measure employed for preventing and relieving, the distressing symptoms of anoxemia, which is a deficiency, in the oxygen content of the blood. Some of the more important conditions in which oxygen treatment is believed to be beneficial are pneumonias, anemia,', heart affections, post-operative pulmonary disturbances, certain mental; disturbances, asphyxia, asthma and atelectasis in new-born infants., The effectiveness of oxygen therapy depends upon the manner of ad ministration* Three common methods, catheter, face mask or tent n are employed. ; The necessity of air conditioning in oxygen therapy arises from the fact that oxygen is too expensive a gas to waste in the ventilation of oxygen tents and oxygen chambers. The oxygen rich atmosphere in these enclosures is therefore reconditioned in a closed circuit by removal of excess heat, moisture, and carbon dioxide given off from the occupants being treated. Oxygen Tents In oxygen tents the air enriched with oxygen is usually circulated by means of a small motor blower,which sends the air over soda lime to remove carbon dioxide and then over ice to remove excess heat and moisture. The concentration of oxygen in the tent is regulated by means of a pressure reducing valve and flow meter. In an inadequately cooled tent, high temperatures and humidities are inevitable, increasing the discomfort of the patient and imposing,an added strain on an already' overburdened heart. Oxygen therapy under such conditions may do more harm than good. An ice melting rate of approximately 10 lb per hour gives satisfactory results in patients with fever in a medium size oxygen tent. . Oxygen tents are confining to the patient. They may terrify the rest less and delirious patient. Medical and nursing care is complicated, as the tent must be opened or removed with attendant loss of oxygen, Air Conditioning in the Prevention and Treatment of Disease 229 Oxygen concentrations of 50 per cent or more are difficult'to maintain, and it is a problem to keep the temperature and humidity low enough in hot weather. . However, with attention to details, the patient can be made quite comfortable. Oxygen Chambers ^ The conventional oxygen chamber is an air-tight sheet metal enclosure of fire-proof. construction, large enough to accommodate one or two patients. Trap, doors or curtains are provided for . the personnel, food and service, to avoid loss of oxygen. Glass windows in the ceiling and walls admit-light frorn outside the chamber. The air conditioning system may be of the gravity type, or of the fan type using mechanical refrig- feration or air drying agents. The temperature and humidity requirement in oxygen therapy depends primarily upon the physical condition of the patient, and secondarily upon the type of disease. In pneumonias28 prescribed conditions should be a temperature of 60 to .75 F, humidity 20-50 per cent, moderate air movement, oxygen concentration of 50 per cent, and carbon dioxide of 1 nnr. 1-1 nno Oxygen in Aviation An important application of the principle of oxygen therapy is in aviation. At the present time all high altitude military airplanes inthis country are provided with gaseous oxygen equipment and military personnel are required to utilize oxygen at all times while-in flight above 15,000 ft, or between 12,000 to 15,000 ft for longer than two hours; or between 10,000 to 12,000 ft for longer than six hours. The use of oxygen in commercial aviation will depend on the height and duration of the flights as welj as the state of health of the passengers. The necessity for portable, comfortable equipment, the possible fire hazards due to smoking, and the use of oxygen on sleeper planes are.some of the difficulties facing civil airline operators. The pressure cabin airplane is a solution to the problem. GENERAL HOSPITAL AIR CONDITIONING Complete conditioning of a large hospital involves a capital investment and running expenses which may not be justified. In clean and quiet districts, the requirements.of almost all general and private wards during the cool season of the year can be satisfactorily fulfilled by the use of conventional heating equipment in conjunction with window air supply and gravity or mechanical exhaust. Insulation against heat arid sound is much more important than humidification in winter; it will also help in keeping the building cool in warm weather. Excessive outside noise and dust may require the use of silencers and air filters in the openings. Cooling and dehumidification in warm weather are important: In new hospitals particularly, the desirability of cooling certain sections of-the building should be given serious consideration. Financial reasons may preclude the cooling of the entire building, but the needs of the average hospital can be met by the use of built-in room coolers and a few portable units which can be wheeled from ward to ward when needed. In the North and certain sections of the Pacific Coast, cooling is needed but a few days during summer, while in the South, it can be used to advantage from May to October, and in tropical climates almost con tinuously throughout the year.