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138 CHAPTER 10 1965 Guide And Data Boole occur and enables the body to remain in heat and water balance. The capacity of the respiratory tract to maintain heat and water balance in comfortable ambient conditions depends upon the integrity of the mucosa. Inflammation of the mucosa, an increase in its temperature, or changes in its surface impede this vital function. During periods of fever, increased heat (7 percent per F deg fever) and water are dissipated. This reduces body temperature but causes excessive water loss. The ideal therapeutic environment for the person is a cool, dry, ambient condition which enhances the dissipation of heat from the re-, spiratory tract and the skin. Water loss must be replenished systematically, particularly when hyperventilation exists. Patients with chronic pulmonary disease are often plagued Fig. 2 .... Relation of Inspired Air Temperature to ' Humidity4 by viscous respiratory-tract secretions. As these accumulate and increase in viscosity, the exchange of heat and water dwindles. Warm, humidified, inspired air i3 rare-ntm! to prevent dehydration under these circumstances. ' ' -* - Patients requiring oxygen therapy or those with a trache otomy (an artificial opening into the windpipe) requirtfspteial attention to assure a warm humid supply of inspired air. The cold1 dry oxygen or the bypassing of the nasopharyngeal mucosa^presents. the.extreme situation. Rebreathing^tech niques for anesthesia and enclosure in an incubator are special means of treating impaired heat loss that must be considered under therapeutic environments. improvement. The greatest difference was in the perspiration rates, a factor of importance to cardiac patients ui particular.* The difficulty encountered in maintaining fluid and electro lyte balance in patients suffering from bums in temperate climates is tremendously increased in hot environments by additional evaporative fluid loss. Naval hospital ships having all wards, laboratories, and living spaces air cooled, represent a notable achievement in the control of environmental factors for the purpose of providing better treatment of patients, especially those suffering from extensive bums. - Patients with thyrotoxicosis tolerate hot humid conditions or heat 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 increased cell -'metabolism,'and in turn to.still greater heat production. This ' vicious cycle may - threaten' life if the cardio-vascular or 'transport mechanism-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-patient. Cardiac patients may be unable to maintain the circula tion necessary .to insure normal heat loss.. Recently the im portance of air conditioning hospital .'.wards and rooms of cardiac, patients, particularly those-with, congestive heart failure, has been stressed as a therapeutic measure.* It is more' important in tropical or subtropical climates. Indi viduals .with head injuries, those subjected to brain opera tions, 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. Ob viously, 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. 'A hot dry environment (89.6 F and 35 percent relative hu midity) has. been used over an extended period for the treatment of patients with rheumatoid' arthritis, with re ported improvement.T. . CONTROL OF AIRBORNE INFECTION - The Council of Physical Medicine of the American Medical Association approved the radiant disinfection of air in 1943, and' two sub-committees of the Committee on Research and Standards of the American Public Health Association have reported favbrablyupon the control of airborne infection by sanitary ventilation and on air sanitation respectively. INFLUB^CE OF AIR CONDITIONING ON HOSPITALIZED PATIENTS Hospital air conditioning assumes a more important role towards patients'than; the promotion of comfort; In many cases, proper air conditioning is a factor in'the therapy of the patient, and, in some instances, it is the major treatment. ..An.analysis.of patients in.a-partially air-conditioned.hos pital where the ambient climate,is normally hot and humid has revealed an improvementof vital in those patients hos pitalised in the-air-conditioned wards as compared to -the group assigned to the unconditioned part of the hnapitel The air-conditioned group was quieter and had more rapid physical Air/Conditionlrig-in the Prevention and Treatment of Disease 139 The ASHAE Technical Advisory Committee on Air Steriliza- * from 19^4 reported progress in The ASHAE ivSbhai. Section, Beating, Pipmg, Air CmdiUming and J0Dmmended a set of definitions, formulations and factors r^ioint adoption by the American Public Health Association JJJj Society- The following paragraphs give some idea of the scope of the subject. : The majority of airborne diseases are spread indoors where people gather. Today the unsolved problem of staphy lococci infection contracted in hospitals now far exceeds and also complicates the respiratory infection problem. Any pro- pi 0f ^ is influenced by a number of factors, ft^fche winter months, the closing of doors, windows, and other means of access to the outdoor air to conserve warmth, as well as the crowing of persons indoors, provides conditions con ducive to a high incidence of contagion. This seasonal phenom enon, illustrated in Big. 4 which represents a study made by the U- S. Public Health Service, will concern the ventilating engineer insofar as air quality (determined by temperature, humidity, air replenishment, type of air movement, and free dom from contamination) is a major intrinsic factor. Apart from the seasonal picture of airborne contagion are such ex;trinsic factors as rate of turnover of personnel, and the marked susceptibility of the recruit as compared with permanent personnel as shown (see Fig. 5) by studies of military per sonnel housed in barracks. These extraneous variables and the factor of contact infection (direct spray) tend to com plicate any evaluation of the effectiveness of air sanitation for elimination of microorganisms in droplet-nuclei and dropletidust. Thus, control measures may eliminate con sistently 90 percent of-airborne organisms in laboratory tests, but may not effect a decrease in actual incidence of infection exceeding 30 percent. Thirty percent may be the maximal reduction in infection possible by air treatment methods. The distinction should be clearly drawn, therefore, between the effectiveness of a procedure in laboratory tests and its effectiveness and applicability, in actually reducing the incidence of airborne disease. On the.other hand, recent studies suggest that inhalation of dust-borne bacteria is more important than direct inhalation of infectious droplets or drop let nuclei in the spread of respiratory tract infections. -. The following sequence of events has-been postulated.as occurring in a large proportion of intra-ward infections: (a) ejection of relatively large protected infective particles from patients, (5) rapid venting or settling of these particles so that those remaining airborne are in low concentration, (c) survival of infective particles to permit .the accumulation of high .concentrations on surfaces, (d) repeated reintroduction of infective particles into the air, under the stimulus of ward activities or by air currents'of the order of 50 fptn over the;floor, and (e) extension of infective.areas by air turbulence .throughout the. ward or hospital..The most im portant link in this probable infection chain has been demon strated to be the reintroduction of particles into the air.14 . Intensive studies on- air disinfection have indicated two distinct control measures: (a) suppression of dust and lint, Rg. 5 .... Monthly Incidence of Acute Respiratory Illness Among Naval Recruits and Ship's Company (Permanent Personnel)11 and (6) disinfection of droplet-nuclei. A. third measure, con trol of relative humidity, is important. It has been shown that the viability of certain organisms sprayed into the atmosphere from a liquid suspension is dependent on rela tive humidity. The mortality rate of the organisms- is .very high at a relative humidity'of'50*perceht,u and decreases'at humidities above and below this figure. It has also been re ported-that the influenza virus loses much of its virulence when the relative humidity,is 50 percent. Well controlled,'large scale tests of the various methods of air sterilization conducted in'barracks11*14 have con firmed the importance-of dust control in minimizing the -spread of airborne disease; a consideration which has guided / the practices of ventilating engineers for a number of years. The importance of the dust factor has been emphasised by many engineers,'and'has been convincingly demonstrated by subsequent bacteriological studies aboard ships. Ultraviolet;radiation of floors and upper air was studied extensively at the Naval Training Center, Sampson, N. Y. In barracks housing naval recruits, hospital admissions.for respiratory infections (mostly catarrhal fever),were 25 percent lower in a group of men exposed to ultraviolet radiation- 2537 Angstrom Units, 1 to-7. ergs per (cm*) (sec) at bed level. than they were in adjacent control .barracks without ultra violet radiation.11 ->* . . A.controlled study over a six-year period on'the.evalua tion of ultrnviolet radiation of siteping quarters;as a1 sup-