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142 CHAPTER 7 1955 Guide providing a uniform environmental temperature just sufficiently high to keep the body temperature within normal limits. Medical and nursing. 1 care are, of course, factors of equal and sometimes of greater importance. Air Conditioning Equipment _ Many of the installations now in use are of the central system type pro viding for filtration, for humidification and heating in cold weather, and for cooling and dehumidification in hot weather. A ventilation rate be tween 8 and 12 air changes per hour is desirable to remove odors and main tain uniformity of temperatures in extremes of weather. Recirculation should, not be used in these wards owing to odors and the possibility of infection. There should be a frequent change in spray water. Control of Airborne Infection The protection of the premature and older infant against infection is , of the utmost importance. It was found in.one installation equipped with I air conditioning, germicidal lights and mechanical barriers that air conditioning alone did not prevent the spread of respiratory cross-infections.41 ? Bacterial ultraviolet barriers, air conditioning and mechanical barriers are efficient. However, infections are brought in by, and often spread by, ward personnel in spite of these measures. FEVER THERAPY Artificial production of high fever in man can be considered an imitation of nature's way of overcoming invading pathogenic organisms. The action ' may be direct and specific by destruction of the invading organism within > the safe limit of human temperatures, or indirect in the case of heat re- ? sistant organisms, by general mobilization of the defensive mechanisms ofit the body. Although the action may be direct and specific by destruction of the invading organisms within the safe human limits, fever therapy exerts much of its benefit through the improvement of the mechanism of bodily1 defense. A serious challenge to the theory on which fever therapy is based- comes from the demonstration .that high fever causes a reduction in the. concentration of circulating antibodies in experimental animals. Patients for fever therapy should be carefully selected. The most serious i complications which may arise are heat stroke, heat exhaustion and eir-.. culatory collapse. The chief minor complications are heat cramps, fever, blisters and mild dehydration. r The limits of induced systemic fever are usually between 104 and 107 Fr ' (rectal), and the duration from 3 to 8 hours at a time. The total period1 of fever treatment varies with the type of the organism involved. ' The diseases which respond favorably to artificial fever therapy are,; gonorrhea and its complications (which include arthritis, pelvic infections? in women, and involvement of the eye), syphilis and chorea. ; The most striking results are seen in gonorrhea and syphilis, since the causative organisms can be destroyed at temperatures compatible with human life. However, the use of fever therapy has decreased since peni cillin has been found so effective in the treatment of gonorrhea and syphilis. Mild fever, up to 101 F for one hour, has recently been used in the treatment? of rheumatoid arthritis. This degree of fever is not bactericidal, but isi believed to stimulate the body defense mechanism. ' Air Conditioning in Prevention and Treatment of Disease 143 Equipment for Production of Fever Artificial fever can be induced by injections of various crystalloid or colloid substances, bacterial products of typhoid and malarial organisms, or by physical methods using hot baths, radiant heat cabinets, hot humidi fied air cabinets, or by short wave diathermy in combination with a cabinet. The relative advantages of various methods have been evaluated clin ically.42 Among the devices for the production of fever by physical means, the one most widely used is the hot humid air or air conditioned cabinet. This apparatus was developed at the Kettering Institute for Medical Re search at Miami Valley Hospital in Dayton, Ohio. In the earlier studies of the Society, temperatures were elevated more easily using saturated atmospheres. A fever therapy apparatus43 using these same principles has proved efficient as a means of inducing and main taining fever in a body, with small likelihood of burns because of the com paratively low dry-bulb temperatures. When heat is necessary in treating legs or arms, such media as short or long wave diathermy, micro-waves, infrared, water baths, etc., have been used extensively. A recent development, a saturated atmosphere heating unit, similar to one previously described has proven satisfactory, because heat may be administered over longer periods which render deep heating possible without fear of bums or shocks. Local heating has been somewhat satisfactory in relieving the painful symptoms of peripheral vascular disease. This procedure, however, is not without danger. Elevation of tissue temperature increases cell metabolism and the need for oxygen. The inadequate blood supply and oxygen deficiency may lead to tissue death or gangrene. Application of heat to the trunk or abdomen, with conse quent reflex dilatation of the vessels of the extremities, eliminates this dan ger of local heat application. Short wave diathermy within the cabinet during the induction phase has been used. When the desired body temperature has been reached by elec trical induction, the atmosphere of the enclosure is kept at saturation to prevent heat loss, thus maintaining the patient's temperature at the de sired point. The two underlying principles in the production of fever by the hot, humid air cabinet are: (1) the transfer of heat by conduction from the circulating hot air to the body, and (2) prevention of heat loss. The latter is more important. In an atmosphere of high humidity, the heat loss by evaporation is markedly decreased. COLD THERAPY Cold as an anesthetic agent was advocated by Allen several years ago.44 freezing of the tissue must be avoided. For certain patients, in whom am putation of an extremity is indicated, the application of a tourniquet with cooling of the affected extremity down to near freezing (5 C or 40 F) is of Vajue. The patient, following this procedure can be prepared for surgery Jothout the handicap of absorption of septic products and severe pain, ims procedure has proven especially valuable in the neglected diabetic patient with an infected gangrenous extremity. Time for treatment of coma and hydration of the patient is gained. However, if amputation 1 an extremity is not indicated, the application of a tourniquet and pack-