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142 CHAPTER 10 1965 Guide And Data Book ments of the majority of- premature infants. Additional heat for Weak (or debilitated) infauta may be furnished in the cribs or by means of electric incubators placed inside the conditioned nursery, with temperature adjusted according to individual requirements. In this way a multiplicity of chambers a^d of air-conditioning apparatus is obviated; the infants in the heated beds derive the benefit of breathing cool humid air, and the nurses and doctors need not expose themselves to extreme conditions. Importance of Humidity: Although external heat is an important factor in the maintenance of normal body tem perature, humidity appears to be of equal or greater impor tance. When the premature nurseries at the Children's Hos pital were kept at relative humidity between 25 and 50 percent for two weeks or longer, the body temperature be came unstable, gain in weight diminished, the incidence of gastrointestinal disturbances increased, and the mortality rose. On the other hand, continuous exposure to air condi tions with 55 to 65 percent relative humidity gave satis factory results over a period of years. The initial physiologic loss of body weight (loss occurring within first four days of life) was found to vary inversely with the humidity. In the old nurseries with natural humidity it averaged 12.4 percent of the birth weight; in the conditioned nurseries it was 8.9 percent with 25 to 49 percent relative humidity, and 6.0 percent with 50 to 75 percent relative humidity. The number of days required to regain the birth weight was correspondingly maximum in the old nursery, and minimum in the conditioned nurseries under high humidity. Maximum gains in body weight occurred in the condi tioned nurseries under high humidity (55 to 65 percent) in infants weighing less than 5 lb. The gains were less under low humidity (25 to 50 percent) in the same nurseries, and in the old nurseries prior to use of air-conditioning apparatus. The incidence and severity of digestive syndromes, with diarrhea, persistent vomiting, diminishing gain or loss of body weight, and other symptoms, were generally -from two to three times as high under low as under high humidity. Summarizing, the best chances for life in premature in fanta are created by maintaining a relative humidity of 65 percent in the nursery, and by providing a uniform environ mental temperature just sufficiently high to keep the body temperature within normal limits. Medical and nursing care are, of course, factors of equal and sometimes of greater im portance. Air-Conditioning Equipment Many of the installations now in use are of the central system type providing for filtration, for humidification and heating in cold weather, and for cooling and dehumidifica tion in hot weather. A ventilation rate between 8 and 12 air changes per hour is desirable to remove odors and maintain uniformity, of temperatures in extremes of weather. Re circulation should not be used in these wards because of odors and the possibility of infection. There should be & frequent change in spray water. Control of Airborne Infection Hie protection of the premature and older infant against infection is of the utmost importance. It was found in one installation equipped with air conditioning, germicidal lights and mt^haniftkl barriers that air conditioning alone did not prevent respiratory cross-infections.** Bacterial .ultraviolet barriers, air conditioning, and mechanical barriers are effi cient. However, infections are brought in, and often spread, by ward personnel in spite of these measures. PATIENT ROOMS Good practice in the air conditioning of hospital patients' bedrooms involves fewer limitations than does that of special purpose areas, and most of the generalizations which apply are discussed in other parts of this chapter. It will be found that each of the several types of systems in common use has its application, that money, space, probable maintenance, and climate all must be into account, and that which is chosen should be the best compromise possible in any given situation. The following are those characteristics which are desirable in a patient room air-conditioning system, and their relative availability should be checked in connection with any system being considered. They are listed, not necessarily in the order of their importance, but in the order in which they might logically be considered. 1. It should be as economical as is compatible with the results desired, both in initial and operating cost and in space. 2. It should afford year-round conditioning according to literal definition. It should be able to deliver heating and cooling simultaneously to various areas os required. 3. It must provide positive automatic temperature control. It should provide positive automatic temperature control on a room by room basis and a range of maintained temperature from 70 degrees to 85 degrees summer and winter is desirable. 4. Recirculation between rooms should be avoided in order to minimize the.possibility of cross-contamination. - 5. Wet coils for recirculated air are best avoided oh account of their tendency to accumulate and release odors. If used, they should be arranged for easy cleaning. 6. It should include the most effective filtration possible; the best is none too good. 7. It should involve air motion sufficient to avoid stagnation but with room velocities, especially across floors, kept low in order to minimi** the reentry of dust. ALLERGIC DISORDERS Hay fever, asthma, eczema arid contact dermatitis are classified as allergic disorders. The allergic individual re sponds to contact with a variety of substances, which are innocuous to a non-allergic person, with severe manifesta tions of hypersensitivity. These substances arc known as allergens and consist of airborne irritants such as dusts, molds, feathers, pollens, animal dander and others; of food protein such as milk, wheat, eggs, etc., or of ample chemicals brought in contact with the skin. They may enter the body by various routes of which inhalation is the most common-type. Ingestion f of offending food substances is not infrequent. The offending substance reacts with the sensitized cells of the mucous membranes or skin. During this reaction, histamine or a histamine-like substance is released and causes (a) increased capillary permeability, (b) secretion of mucus and (c) muscular contraction. In the eyes and nose this produces itching, redness and lacrimation or rhinorrhea, in short, the symptoms of hay fever. In the lungs it causes, in addition to the secretory response, a contraction of the smooth muscles of the bronchi resulting in a bronchial asthma. It is commonly known that non-specific environmental factors such as dust, irritating gases, change of temperature and humidity may precipitate.asthmatic attacks in allergic subjects, even in the absence of exposure to specific allergens. It is assumed that the presence of frequent allergic bronchial constriction renders the smooth muscles of the bronchi so sensitive to various non-specific stimuli that the threshold of their response to such irritation is considerably lower than that* of a non-allergic individual. A^f.Conditioning in the Prevention and Treatment of Disease 143 Air.Condiioning Apparatus Of ail the measures to relieve a specifically sensitive in dividual elimination of exposure to the responsible allergen is the most efficient, though not always a practical, form of treatment In recent years considerable effort has been made to accomplish such elimination by removal of respiratory allergens from enclosures by filtration or other air-condition ing processes. ... ^papgr or doth filters, mounted m inexpensive wmdow or floor units, prove quite satisfactory in many cases, but since dust and smoke frequently cause asthmatic attacks, it is desirable that-an air filter, to be of full value in the treat ment of asthma, should remove all possible dusts and pollens regardless of size or amount. Electrostatic air cleaners are more efficient than most commonly used types for capturing very fine dust. ' Although the chief remedial factor in the treatment by conditioned air is the filtration of pollen, a certain amount of cooling and dehumidification appears to be desirable. A comfortable temperature between 70 and 75 F, and a rela tive humidity well below 50 percent has proved satisfactory.** Direct drafts, overcooling or overheating are apt to initiate or aggravate the symptoms. Limitations of Air-Conditioning Methods The results obtained with air filtration, or other air con ditioning processes, in the control of allergic conditions, are fairly comparable to those obtained by desensitization treat ment, so long as the patients remain in the pollen-free at mosphere. 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 nights. With rare exceptions, the symptoms recur on exposure to pollen-laden air. Moreover, the useful ness of air-conditioning methods is limited, because all cascs are not caused by airborne substances. Cases of bacterial' asthma do not respond to treatment with filtered air. Despite these limitations, air-conditioning methods-pro vide definite advantages in the simplicity of treatment, con venience, and, under certain conditions, almost immediate relief.*1 Pollen cases are usually relieved of most of their symptoms within 1 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 iHnoaa SPECIAL APPARATUS A variety of apparatus has been created for the application' special conditions to be applied to various patients to assist in the cure of specific diseases. Hyperthermia, the de liberate creation of a fever; hypothermia, cooling below nor-' Dial body temperature; fog therapy, the use of a superhumidified atmosphere; and oxygen therapy are the most important. HYPERTHERMIA Hyperthermia is a technique to raise patients' temperatures to points sufficient to kill certain bacteria within them.** Gonorrhea, syphilis and pelvic infections were often treated by jjising the body temperature to between 104 and 107 F for three to eight hours. The-development .of antibiotics ade this dangerous procedure unnecessary, and it is now a aeariy forgotten technique. HYPOTHERMIA - Hypothermia was originally used in the 1930's for the treatment of cancer known to be inoperable.** It waa'later shown to be ineffective for this purpose, but the technique had a resurgence recently as an SuSiuetiC for Open-heart surgery, brain operations, and liver surgery ***** Reduction of a patient's temperature throughout his body, or the isola tion of part of his body and localized cooling, lowers the oxygen demand to the point that the blood supply can be cut off tem porarily and dry surgery can be done. The development of other techniques, such as the use of pumps to furnish a supply of blood to the rest of the body, has lessened the use of hypo thermia, but it is still used and is sometimes coupled with the use of the pump to reduce the obligatory blood flow.*4 There is a variety in methods of producing hypothermia. One method is to lower the patient into a tank of shaved ice. In another, cold water is circulated through an enveloping mattress to cool the patient. A pump may be used to circulate chilled blood through a specific organ to reduce its tempera ture. The method is hazardous and slow, but it has permitted successful completion of special surgery. In its latest role hyperthermia has been used in the rewanning of these patients. Heated electric pads, induction coils, hot baths, infrared lamps, or a long wait for the patient to regain his normal temperature have all been used.*7 FOG THERAPY . Devices have been installed in patients' rooms to create a heavy, foggy atmosphere.** The excess moisture vaporizes when the air is warmed to body temperature on inhalation, preventing water loss. This atmosphere is used for the treat ment of respiratory disease and helps to hydrate the thick, tenacious excretions that clog patients' respiratory passages. The therapy, though effective, has its own hazards. The rooms and machines themselves can become overgrown with bacterial and fungal growths. Care must be taken to prevent the spread of disease by painting the rooms with bacteriaand mildew-resistant paint and by a concurrent disinfection of the humidifying and air-conditioning manhinM. When a patient is discharged from such a room, it should be cleaned by wiping it down with a bactericidal and fungi cidal solution. Beds and furniture should be sprayed with a steam-hydraulic jet cleaner.. Mattresses, bedding, and the patient's clothes and belongings should be sterilized in a non destructive device such as an ethylene oxide gas sterilizer. OXYGEN THERAPY Many patients have such decreased capacity for inspiring oxygen from the atmosphere that they are given a supply of pure oxygen. This can be done with a mask or a nasal tube or by oxygenating a plastic tent. Regardless of the method, it is important to realize that the oxygen must be humidified and the temperature must be con trolled to complement the weakened human system.4 Since pure oxygen enhances combustion, it is necessary to insure that the beating device is designed to protect against oxygen fire hft-Eftrda. POLLUTANTS The air of numerous localities contains hundreds of sub stances that' cause discomfort, illness, and, sometimes,death.** Histologic study of inflated lungs has demonstrated rupture of the walls of the alveoli and relaxation of the al veolar ducts about deposits of soot trapped in the parenchyma, as the initial lesion in chronic emphysema.4* Postoperative tetanus and gas gangrene have been attributed .to bacteria sucked into the ventilating system from manured-lawns. - < Ventilation with outside air, therefore, is often,undesirable.