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246 CHAPTER 13 1946 Guide 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 anesthetized 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 operation52. The severe physiological effects, such as excessive sweating and rapid pulse, of high operating room temperatures on attendants and patients during the hot months signify the need for proper cooling. A comparison of'surgeons^ statements who operate in both air conditioned and non-air conditioned rooms strongly indicates that the recuperative power of the patient is greater when operated upon in air conditioned rooms2?. Although the comfortable air conditions for the operators are not identical with those for the patient, it is usually not difficult to coniprd- mise within a range of 55 to 60 per cent relative humidity, and 72 to.80 F temperature. The work just cited , reported that 68 to 70 F, effective temperature not only furnished comfort for the operating room workers, but apparently prevented exhaustion of the patient as evidenced by rapid convalescence in the recovery ward. Additional heat may be furnished to the patient locally or by suitable covering according to body-tempera ture in individual cases. -, . . In the control of airborne infection in the operating room the prevention of dispersal of infectious materials into the air, control of dust and proper ventilation supersede attempts to remove or kill pathogenic organisms. ' _ : Ih'ariinvestigatiori recently conducted at the University of Pittsburgh, , in,a cpoperative research,program with the Society, comparative stiidies were made, on bacterial content', of conditioned and n'on'-conditioned operating rooms. From these studies22 it .was concluded that' the bac terial content of conditioned operating rooms was' considerably less than that of npn-conditioned rooms. Bacterial counts aboard an air conditioned submarine were found to be exceptionally low arid not cumulative.with time'although all: of the air' w^ recirculated for more than 12 hours " without replenishment. The removal of bacteria by the process of air cooling'and condensation of moisture out of air' merits further study ". ' The degree of air contamination can be reduced by proper ventilation if-velocity of air over the floor does'not exceed 50 fpm. Research is in progress onqhe.use of-filtered air flowing through a systein-of mechanical cleaners which protect the patient against infection from''attendants and ' from bacteria-containing air in the corridor of ward . Operations may be-postponed on allergic patients during asthmatic manifestations:through fear of'complications.' The removal of air-borne allergens, therefore,.is.in some cases an important function of the air conditioning.system.in preparing, patientsfor:operation. Central system air coriditioning plants and unit air conditioners prove satisfactory in operatirig roorns when .producing between 8 and 12 air .-changes per hour of filtered and properly conditioned air without redrculhtiori during the course' of anesthesia. A separate exhaust fan system is usually- necessary to confine and remove the gases and odors. Double winddws are desirable arid often necessary to prevent-condensation and Air Conditioning in the Prevention and Treatment of Disease 247 frosting on the glass in cold weather arid to minimize drafts. The air flow of 8 to 12 air changes in operating rooms should: (1) reduce the concen tration of the anesthetic to well below the pharmacologic threshold in the vicinity of the operating personnel, (2) remove the great amounts of heat'and sometimes moisture, from sterilizing equipment if inside the operating room, from the powerful surgical lights, from solar heat, and from: the bodies of the operatives, and (3) provide extra capacity for quickly preparing , the room for emergency: operations. Much can be gained by thermal insulation of sterilizing equipment and by thorough exhaust ventilation of sterilizing rooms adjoining the operating rooms. Too great a difference in temperature between the operating room and the finaf hospital destination of the patient, including corridors and elevators, is conducive to infections of the upper part of the respiratory tract and .post-operative pneumonia.' A suggested remedy, is a recovery ward in which conditions closely approximate those of the operating room and in which the patients remain from one to four days.' Satis factory conditions in the recovery ward not only hasten convalescence, but dispel the fear frequently found in patients who must undergo operations during the hot seasons ......... .. Experience has shown that aifew: hours after the operation the tem perature of the post-operative room can be decreased a few degrees below that of an overheated operating room to stimulate recovery, NURSERIES FOR PREMATURE INFANTS One of the most important requirements.in. the. care of premature' infants is the stabilization of body temperature. , This is necessary, because their heat regulating systems are not fully developed; the metabolism is low and the infants generally, exhibit-marked inability to maintain normal body temperatures. The resistance to infectionjs low and mortality rate high. . ... Air Conditioning Requirements Theoptimum air conditions for the. growth and development of these in fants were determined by extensive research2? at the Children's Hospital,, Boston, Mass., using four valid criteria; namely,- stability of body tem perature, gain in weight, incidence of digestive syndromes, and mortality. Individual temperature requirements varied>,widely;(frorir72 '.to TOO F) according to the cohstitutional state of the infants and body.. .weights. The optimum relative humidity was about 65 per cent,.'and.'.the air mpvemeht'less. than 20 fpm-,. A single-nursery conditioned to 77 F arid 65 per,cent relative humidity was found to fulfill satisfactorily the.,requirements, of the' majorityof premature infants. Additional .heat , for weak (or debilitated) .infants may be furnished in the cribs or by means of electric incubators placed inside the conditioned nursery, and, the.temperature adjusted according to individual requirements. "In' this way multiplicity of chambers and. of air conditioning apparatus is obviated;.the infonts irijtheffieated'beds' derive the benefit of breathing cool humid air, arid :the nurses and .doctors need not expose themselves to extreme conditions, Importance of Humidity: I Although external , heat : is: an ..-important factor in the maintenarice of.normal body temperature, humidity appears to be of equal or greater importance/: When' the:premature.nurseries at the Children's Hospital were kept at relative humidity betweerr`-25 and 50