Document xdbNZeE171ZbpjpyYZxvLzb7G

140 CHAPTER 7 1950 Guide tages of part time cooling on personnel to promote rest and sleep in tropical areas would provide a prophylactic measure of great potential importance. TREATMENT OF DISEASE In the past few years considerable progress has been made in using air conditioning as an adjunct in the treatment of various diseases. Among the important applications are those in operating rooms, nurseries for premature infants, maternity and delivery rooms, children's wards, clinics for arthritic patients, heat therapy, cold therapy, oxygen therapy, X-ray rooms, the control of allergic disorders, and for the physiological effects in industry. Normal individuals may be subjected to considerable strain in adjusting to hot, humid conditions. Heat loss by radiation is reduced, as is loss by evaporation of sweat. Individuals with certain disease processes are at a still greater disadvantage since they may also have difficulty in the trans port of heat from the interior to the surface of the body via the circulation. Patients with thyrotoxicosis tolerate hot, humid conditions or heal waves very poorly. Their metabolism is high, and therefore their heat production is excessive. They may be unable to eliminate heat from the body surface as rapidly as it is produced and transported to the skin. They develop hyperthermia or fever, and a tachycardia or rapid heart rate. The demand on the circulation for transport of heat from the interior of the body to the skin surface is increased. The increased body temperature leads to in creased cell metabolism, and in turn to still greater heat production. This vicious cycle may threaten life if the eardio-vascular or transport mecha nism breaks down. A cool, dry environment favors the loss of heat by radiation and evaporation from the skin, and may save the life of the pa tient with thyrotoxicosis. Cardiac patients may be unable to maintain the circulation necessary to insure normal heat loss. Individuals with head injuries, those subjected to brain operations, and those with barbiturate poisoning may have hy perthermia, especially in a hot environment, due to a disturbance in the heat regulatory center of the brain. Obviously, one of the most important factors in recovery is an environment in which the patient can lose heat by radiation and evaporation, namely, a cool room with dehumidified air. The patient in shock, or the patient who has had a severe hemorrhage, may have an inadequate volume of circulating blood and be unable to maintain an adequate skin circulation. This may result in heat storage or fever. Patients with extensive skin bums may be unable to lose heat adequately from the limited uninvolved skin surface, and thus develop a fever. They need adequate fluid replacement, saline solution, plasma or blood to expand the circulating blood volume and thereby improve pe ripheral circulation. A cool environment is valuable in aiding heat loss after adequate skin circulation is established. A hot, dry environment (89.6 F and 35 per cent relative humidity) has been used over an extended period for the treatment of patients with rheumatoid arthritis, with reported improvement." OPERATING ROOMS The widest application of air conditioning in hospitals is in operating rooms. Complete air conditioning of operating wards is important be cause winter humidification helps reduce the danger of anesthetic gases; Air Conditioning in Prevention and Treatment of Disease 141 cooling with some dehumidification tends to eliminate excessive fUHm7e and to protect the patient and operating personnel; and finally, filtering aids the removal of allergens from the operating room air. Reducing Explosion Hazard Explosion hazards in operating rooms began with the introduction of modern anesthetic gases and apparatus. Ether administered by the old T. method gives rise to an explosive mixture, but in practice this method is still regarded as comparatively safe. When ether is mixed with pure oxveen or nitrous oxide in certain concentrations, the explosion hazard may be'as great as with ethylene-oxygen, or cyclopropane-oxygen mixtures. Of the anesthetic gases nitrous oxide alone does not explode but supports combustion. Ether, vinyl ether, ethylene, and cyclopropane are as poten tially dangerous as gasoline or illuminating gas in the home " Chloroform does not explode violently in contact with flame but decomposes to liberate phosgene. All of the anesthetic gases and vapors, except ethylene, are heavier air. Although the incidence of injury or death from explosion is negligible compared with other hazards in the operating room, the dra matic features surrounding an explosion justify continued investigation to eliminate the hazard. During the course of ethylene anesthesia, the mixture, usually 80 per cent ethylene and 20 per cent oxygen, is so rich that the danger of explosion is slight in the immediate vicinity of the face mask, but leakage of ethylene into the air may accumulate to any lower concentration, and thus introduce a serious hazard. The most dangerous period is at the end of the operation when the patient's lungs and the anesthesia apparatus are customarily washed out with oxygen with or without the addition of carbon dioxide. Even when thi3 procedure is omitted, it is difficult in practice to avoid dilution of the anesthetic gas with air during the normal course of breathing following the administration. In either case the mixture would pass through the explosion range and extraordinary precaution is necessary for the safety of the patient and operating personnel. In a study54 of 230 anesthetic explosions and fires, 70 per cent of the ex plosions and 60 per cent of the deaths were caused by igniting agents other than static sparks. In 1941 the National Fire Protection Association" made certain recommendations for safe practice based on available infor mation. Some of these recommendations are: Windows should be kept closed so that the air conditioning system can prevent pooling of explosive anesthetic gases. Twelve air changes per hour and a humidity of 55 per cent are advised. If a higher humidity were compatible with the well being of the patient and personnel, it should be maintained. All electrical installations should comply with the standards set by the National Electrical Code for use in ex plosive situations. Cautery equipment should not be used in hazardous locations. To prevent static sparks, all bodies in an operating room should be conductive or coupled. It is essential that adequate grounding be provided for the floor and every object in the operating room. Conductive rubber should be used on shoes, leg tips, operating table coverings and all rubber parts of the anesthesia equipment. All furniture in contact with the floor should be metal. -In the absence ofcomplete grounding facilities, the simple method of intercoupling patient, operating table, anesthetist and gas machine at ground potential may be used. Experience has shown that neither high humidity nor intercoupling devices has eliminated the danger from static electric discharge. The removal of gas concentrations from the operating table area, by means of specially devised exhaust ventilation, should be thoroughly tested. Port-