H Rüden’s research while affiliated with University of Bonn and other places

Three standard variants of intensive care units are described. The hygienic-microbiological examinations of the patients' surrounding show in how fat architectural factors influence the propagation of germs responsible for nosocomial infections. The results are hygienic requirements concerning the architectural functional structure of intensive care units to facilitate the maintenance of anti- and asepsis for the nursing personal.

During the winter-half-year 1976/77 the concentrations of airborne microorganisms in the open air were measured in Bonn and at a place in the Sauerland. Simultaneously the data of wind direction, wind speed, atmospheric rel. humidity, temperature, intensity of solar radiation were registered. It can be shown, that the denominated parameters are influencing the content of microorganisms of the air in different proportions.

7 intensiv-care-units (I.U.C.) were compared by analysing the charts of 100 patients from each station. They showed remarkable differences concerning the diagnosis of admittance, age and other factors related to the risk of infection. Consequently, kind and number of intensive care related medical procedures, the use of antibiotics, the duration of the patients stay on the station and the death rate differed widely. Some criteria concerning the layout, personnel, organisation and therapy on I.C.U. are named, which are mainly related to the patients condition and to the thereby given risk of infection.

For a period of approximately six months the concentrations of airborne microorganisms were determined by the uptake of their day-characteristic at local places differing by the extent of air pollution. By simultaneously recording the meteorological parameters as temperature, relative humidity, direction and velocity of wind and intensity of solar radiation, it was intended to find out the relationship between these factors and the viability of airborne microorganisms. The present data show an oscillation of the concentration counts over a wide range and seem not yet to depend on the local situation of air pollution.In a further series of experiments the atmospheric aerosol m was collected on air-filters. The decreased substances were extracted from the filter material by aqueous and organic solutants and tested for their antimicrobial activities. In this context the seasonal dependence of the microbicidal activity of organic compounds of aerosol is discussed.

The concentration of microorganisms showed variations over a wide range. As factors influencing their viability meteorological parameters as relative humidity and temperature were recognized. Furthermore there are other antimicrobial compounds in the air. For their demonstration the aerosol was collected on air filters and then extracted in aqueous solutions. Their examinations showed that there are geographic and seasonal dependences of the antimicrobial activity of the aerosol.

Microbiological tests have established that intensive care units act as a reservoir from which hospital infections spread. The mode of their spread is reviewed. The increased incidence of nosocomial infections to intensive care wards is attributable partly to deficient antisepsis and asepsis and partly to inadequate planning of the building and organization of these wards. Plans for two intensive care wards are put forward which would reduce the risk of contact, smear and air-borne infections. In the planning of these units greater attention than has so far been the case should be paid to preventing the spread of pathogenic micro-organisms.

A climatic chamber for laboratory use is constructed using unexpensive materials. The relative humidity is to be adjusted between 20% and nearly 100% by regulation of the water temperature in the humidifier. The temperature range is 20-40 degrees C. As there are to be done experiments with air filter samples under practical conditions the system is enabled to work up 75 m3 of fresh air per hour. In comparison to commercially available apparatus the system described may be easily modified to fit the geometrical and experimental conditions.

The main use of ultraviolet light radiation in hospitals is for the disinfection of the air. A study was made of the disinfecting efficiency of indirect ultraviolet radiation (lifts, cleaning of bedding), direct irradiation of rooms overnight or after use, ultraviolet curtains (irradiation of the whole width of passages, doorways and entrances) and ultraviolet irradiation of the filter of air-conditioners. The results are analysed. With the exception of the barrier technique ultraviolet light irradiation did not substantially reduce the number of micro-organisms in the air. Knowledge of the limitations and side-effects of this technique, control of the intensity of ultraviolet irradiation and bacterial counts are regular intervals are some of the factors that determine the success of this mode of disinfection. Detailed studies of the acceptable upper limits of the number of micro-organisms in the air of hospital wards and operating theatres is of prime importance for evaluating the effectiveness of air-disinfection by ultraviolet light irradiation.

Quantitative determinations of antibiotic susceptibility established that infections occurring in intensive care units were predominantly exogenous cross infections. The most frequently isolated strains were: Klebsiella, Enterobacteriaceae, Serratia marcescens and Proteus mirabilis. The majority of the strains showed multiple resistance. Despite adequate antibiotic therapy a number of patients died of the infection. Many of the methods of disinfection were found to be inadequate, especially as regarded washbasins, face flannels, ultrasound inhalers, respirators and other apparatus. The fact that many of the isolated strains are capable of multiplying in water is not receiving sufficient attention.