Document ga4ea5DdX34n1QkXJ8xMwDnrJ

144 CHAPTER 7 1951 Guide 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 -kin circulation is established. A hot, dry environment (89.6 F and 35 percent relative humidity) has been used over an extended period for the treatment of patients with rheumatoid arthritis, with reported improvement.82 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; summer cooling with some dehumidification tends to eliminate excessive' fatigue 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 . modem anesthetic gases and apparatus. Ether administered by the old drop method gives rise to an explosive mixture, but in practice this method is still regarded as comparatively safe. When ether is mixed with pure oxygen, 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.33 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 than 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 percent 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 this 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 study24 of 230 anesthetic explosions and fires, 70 percent of the ex- Air Conditioning in Prevention and Treatment of Disease 145 , -.n,, and go percent of the deaths were caused by igniting agents other th"j statjc sparks. In 1941 the National Fire Protection Association35 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 line of explosive anesthetic gases. Twelve air changes per hour and a humidity PfV; nercent lire advised. If a higher humidity were compatible with the well being f the patient and personnel, it should be maintained. All electrical installations hmild 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. Tonrevent static sparks, all bodies in an operating room should be conductive or -.-!--d!cj It is essential that adequate grounding be provided for the floor and every obTectTn 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 of complete 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 able duct systems as installed aboard ship should be acceptable. Serious explosions can occur in a closed system, but proper precautions will reduce this hazard to a minimum. It should be realized that when a room and the occupants have been com pletely grounded, there is always the possibility that the'patient or the operator might receive a dangerous shock if a short circuit developed in any of the electrical equipment. A comprehensive study of the explosion problem and of the general causes and prevention of operating room hazards, by the University of Pittsburgh, the A.S.H.V.E.-Research Laboratory, and the U. S. Bureau of Mines has led to a fruitful attempt to eliminate the explosive range of cyclopropane, one of the best but most difficult gases to handle. The use of hefium as a diluent in the total gaseous mixture controls the oxygen concentration by displacement and, because of its flame quenching properties, it is the ideal gas for this purpose. In addition, a gaseous mixture containing helium is more difficult to ignite by electric discharges, and this quality also in creases the safety factor of anesthetic administration. Operating Room Conditions Little is known about optimum air conditions for maintaining normal body temperatures during anesthesia and the immediate post-operative period. An anesthetized patient displays dilation of blood vessels in the skin resulting in profuse sweating and (it has been believed) inability to regulate body temperature. From this it was concluded that all anes thetized patients suffered considerable heat loss, although there may be little more than 0.8 F variation in the rectal temperature during the course of the operation.33 The severe physiological effects, such as excessive sweating and rapid pulse, of high operating room temperatures on attend ants and patients during the hot months signify the need for proper cool ing. Statements of surgeons who operate in both air conditioned and non-air conditioned rooms strongly indicate that the recuperative power of the patient is greater when operated upon in air conditioned rooms.33 Although the comfortable air conditions for the operators are not identi cal with those for the patient, it is usually not difficult to compromise within