Scaling behavior in non-Hookean compression of thin-walled structures.

The mechanics and stability of thin-walled structures is a challenging and important branch in structural mechanics. Under vertical compression the deformation of a thin-walled box differs from that of, e.g., a cylindrical shell. It is demonstrated here that compression of a box can be described by a set of generic scaling laws representing three successive regimes: a linear, wrinkled, and collapsed regime. The linear Hookean regime represents the normal behavior before any instability sets in, while the following wrinkled regime is shown to be analogous to compression of thin-film blisters. The compression force reaches its maximum at the onset of the final collapsed regime that has all the characteristics of membrane crumpling. The theoretical scaling laws were confirmed by numerical simulations.

Air contamination in open heart surgery with disposable coveralls, gowns, and drapes.

The effect of a polypropylene coverall, replacing shirt and trousers, combined with sterile laminated gowns and drapes compared with an all-cotton system was studied in regard to the dispersion of bacteria and particles in a conventionally ventilated operating theater. The operations carried out were open heart procedures in 30 adult patients. Blood agar sedimentation plates were placed in the operative, anesthesia, and perfusion areas. The mean sedimentation values during 1 hour after the start of operation were as follows in the laminate group: 63 colony-forming units (cfu)/m2 in the operative area; 77 cfu/m2 in the anesthesia area; and 143 cfu/m2 in the perfusion area. The corresponding figures in the cotton group were 350 cfu/m2, 364 cfu/m2, and 437 cfu/m2, respectively (p less than 0.0002). At the beginning of the operation, the mean values noted for colony-forming units in the air at the operative site were 8.0 cfu/m3 in the laminate group and 31 cfu/m3 in the cotton group. One hour later, the values were 10 cfu/m3 and 22 cfu/m3, respectively (p less than 0.0002). At the end of the operation, the number of particles 5 microns or larger in the air at the operative site was 278/m3 in the laminate group and 592/m3 in the cotton group. It is concluded that the use of a polypropylene coverall and laminated gowns and drapes significantly reduces the particle and bacterial contamination of the air and the bacterial sedimentation during cardiac operations.

Handwashing in Finland.

To prevent skin problems we have recommended in Finland that hospital personnel should avoid soap or other detergents for handwashing and instead use alcoholic preparations containing emollients such as 2% glycerol. Alcohol with emollient disinfection is used frequently in hospitals and it causes fewer complaints of skin dryness than washing with soap. However, there are still members of staff who have hand skin problems. Our studies conducted during winter have shown that when these persons used emulsion for hand cleansing, instead of washing with soap, skin deterioration was much less, allowing alcoholic disinfection of the hands whenever necessary, without impairment of the disinfecting effect of alcohol.

Prevention of dryness and eczema of the hands of hospital staff by emulsion cleansing instead of washing with soap.

The acceptability of two handwashing/cleansing methods, cleansing with emulsion or washing with liquid soap and water, were compared in a randomized, prospective long-term study. Thirty-eight members of hospital staff who had a history of hand skin dryness or eczema and a need for frequent handwashing used either liquid soap or emulsion for handwashing or cleansing. The clinical assessment of skin condition was done blindly by the same dermatologist at the onset of the study, and after 2 and 4 months with a predetermined scoring system. The median skin dryness index of persons in the liquid soap group increased significantly from an initial 1.4 to 3.6 during the 4-month winter study period (P less than 0.001), while the corresponding figure in the emulsion group decreased during the same time from 1.9 to 1.1 (P = 0.053). The difference in dryness between the groups was significant after 2 months (P = 0.04) and after 4 months (P less than 0.001). After 4 months, six people in the emulsion group had no dryness of the hands compared to only one in the liquid soap group. Similar trends were noticed in the occurrence of eczema. The median eczema index decreased significantly in the emulsion group from 0.4 to 0.1 during the study. In the liquid soap group, the increase in the median eczema index was from 0.4 to 0.7 (difference not significant). On an individual level, the eczema became worse in only one subject in the emulsion group, but in seven in the liquid soap group.(ABSTRACT TRUNCATED AT 250 WORDS)

Cleansing of hands with emulsion--a solution to skin problems of hospital staff?

In this study of hand cleansing, nursing staff with skin problems used emulsion followed by rinsing with water, while control groups, with or without skin problems, used liquid soap and water. Clinical evaluation of the without skin problems, used liquid soap and water. Clinical evaluation of the skin by a dermatologist, as well as by self-assessment, suggested that when the staff with skin problems used emulsion their skin was in better condition than that of controls with similar skin problems. This favourable effect on skin was later confirmed in extended use of emulsion for hand cleansing in other hospital wards. Objective evaluation of skin condition with biophysical measurements was unsuccessful. Emulsion cleansing of the hands seems to offer a favourable alternative to washing with soap and water, especially for persons with skin problems.

The conventionally ventilated operating theatre and air contamination control during cardiac surgery--bacteriological and particulate matter control garment options for low level contamination.

OBJECTIVE: The purpose of the study was to compare the usefulness of a conventional bacteriological technique with that of particle counting under lower air contamination and better aseptic conditions achieved with special staff garments and covering for the patient. Contamination levels were estimated with continuous on line air particle counting measurement, volumetric intermittent short period aerobic bacteriological cultures and wound surface contact cultures. METHODS: In a series of 66 consecutive coronary artery bypass operations performed by the same team and in the same theatre using different types of patient and staff clothing, the impact of a reduced bacteriological and particulate contamination were assessed. The volumetric air contamination of particles > or =5 microm and bacteria-carrying particles were monitored 30 cm above the sternal wound. The bacterial contamination and bacterial wound infections in the sternal and leg wounds were assessed as well. RESULTS: With the alternative garment and textile system, the air counts fell from 25 colony-forming units (CFU)/m3 to 7 CFU/m3 (P < 0.0038). The contamination of the sternal wound was reduced by 46% and that of the leg wound by >90%. In order to give continuous contamination feedback during the whole operation to the theatre staff, particle counts > or =5 microm were monitored and visualized. Air particle counts decreased rapidly from 850 particles/m3 and stabilized to approximately 50 particles/m3 when the alternative clothing system was used (P < 0.001). Low particle counts > or =5 microm should offer the possibility to indirectly estimate air bacteria carrying particle counts during the entire operation. Less than 20% of the total count in this size group carries bacteria. The low air contamination was achieved even in an ordinary ventilated theatre when individual team members used clean air suits in combination with impermeable patient drapes. When air particle level < or =50 particles/m3 is reached, the bacterial air contamination is in the order of that of orthopaedic hip operations. The staff must during the entire operation adjust their activity to air asepsis. CONCLUSIONS: The use of clean air suits and impermeable patient clothing results in a low exogenous contamination of air and wound. Continuous air particle monitoring is a good intraoperative method to monitor the air contamination longitudinally in an operating theatre.

Prevention of microbial contamination of the dental unit caused by suction into the turbine drive air lines.

OBJECTIVE: To determine whether a specially designed antisuction device can prevent the bacterial contamination of the drive air lines of the dental turbine that is caused by suction when the turbine is stopped. STUDY DESIGN: A dental unit with and without the antisuction device and three different types of sterilized handpieces were used in the tests. Each turbine was operated in air, then submerged into a bacterial suspension of E. coli and enterococci for 3 seconds, removed, and stopped. This procedure was repeated 10 times. Possible bacterial contamination of the drive air lines was examined by submersing the head of a sterilized handpiece with the turbine running into a nutrient broth for 30 seconds. The broth was incubated at 35 degrees C up to 2 days. RESULTS: After use of the conventional dental unit, bacterial growth of drive air lines was found in 10 of 150 broth samples. After the installation of the antisuction device no bacterial growth was found in any of the 138 samples. The difference in the contamination frequencies is statistically significant (p = 0.011, Fisher's two-sided exact test). CONCLUSIONS: The drive air lines of the turbine in the dental unit may become contaminated despite the sterilization of handpieces. The antisuction device installed into the dental unit was found to prevent the contamination. With the exception of possibly immunocompromised patients, the transmission of microbes by exhaust air may be too small to cause infections. However, transmission of oral material between patients should be prevented in dental practice.

Effectiveness of hand washing and disinfection methods in removing transient bacteria after patient nursing.

The effectiveness of various hand washing and disinfection methods in removing transient skin bacteria was studied in hospital after dry or moist contamination of the hands when nursing burn patients. The results were compared with those of laboratory tests with volunteers. A fairly good correlation of the bacterial reductions existed between hospital and laboratory tests. All other methods removed Staph. aureus from the hands more effectively than liquid soap. Gram-negative bacilli were more easily removed than staphylococci, even with soap wash alone. In hospital, none of the washing and disinfection methods always removed all patient-borne bacteria from the hands. After dry or moist contamination and subsequent washing with soap only, colonies of Staph. aureus were often detected in finger-print samples. Staphylococci were more often completely removed by a 4% chlorhexidine detergent scrub and alcoholic solutions (either with or without previous soap wash) than by liquid soap, hexachlorophene or iodophor preparations. Gram-negative bacilli were more easily removed by all the washing and disinfection methods. After moist contamination, Gram-negative bacilli were more often completely removed from the hands by ethanol than by other treatments. The results of the present study emphasize the importance of always using gloves when nursing a profuse spreader of bacteria or one who must be protected from infection.

An evaluation of antiseptics used for hand disinfection in wards.

The antibacterial effectiveness of hand antiseptics commonly used in wards was studied by laboratory and in-use tests and their acceptability assessed by means of a questionnaire passed to hospital staff. To determine the immediate and long-term antibacterial effects of the preparations the in-use tests were performed by groups of students. The greatest immediate reduction in bacterial counts on hands was obtained by products containing chlorhexidine. The long-term antibacterial effect was recorded with emulsions containing 3% hexachlorophane, 2% Irgasan CF3R or 4% chlorhexidine when used constantly on several consecutive days. Considerable discrepancies were recorded in the antibacterial effectiveness of some preparations when comparing laboratory and in-use test results. Therefore it is suggested that antiseptics should be tested by in-use tests which more closely resemble practical conditions before their use, or further trial, in hospital.

The importance of soap selection for routine hand hygiene in hospital.

Five different types of liquid soap were studied in hospital wards, each during two months' use. Altogether 1306 finger print samples were taken from the hands of the staff by sampling twice a week and the acceptability of the soaps was measured by a questionnaire. During the use of different soaps only slight differences were found in the numbers of total bacteria or in the occurrence of Staph. aureus and gram-negative bacilli on the hands. During the use of the emulsion-type product studied, several persons who had dermatological problems had lower mean bacterial counts of the fingers than during the use of the other soaps. This soap was also favourably accepted by the staff. After over one year's use of pine oil soap and alcohol, the staff of the hospital was satisfied with the method. However, several persons with skin problems admitted to not using soap or alcohol. The considerable differences found in the acceptability of soaps imply that for use in hospital the choice of a soap acceptable to the nursing staff is important in promoting proper hand hygiene.

The situation of hospital hygiene in Scandinavia.

The situation of hospital hygiene in Scandinavian countries, especially Finland, is described. The infection control activities are most often also quality assurance and management, although the infection control staff does not always realize it. The features of infection control in all Scandinavian countries are similar, but they differ in details. Most hospitals have Infection Control Committees with an advisory and expert role in infection control, but normally with no executive power. All Scandinavian countries have a network of skillful Infection Control Nurses working together with the Infection Control Officer of the hospital. The Scandinavian countries have advanced guidelines for various procedures and other activities that need infection control alertness. The voluntary infection control societies have a major role in the development of infection control activities and education. The development of suitable process and outcome quality indicators are a demanding task for the future.

Evaluation of chlorine compounds for surface disinfection by laboratory and in-use testing.

The disinfecting properties of chloramine and compounds containing chlorinated trisodium phosphate and potassium bromide or sodium dichlorisocyanurate and detergents were studied by laboratory and in-use tests and compared with a phenolic disinfectant containing detergents. In a modified Kelsey test all the preparations were effective in the recommended dilutions in clean conditions. The effectiveness of the chlorine-bromine disinfectant substantially decreased in the presence of organic material. The in-use testing was performed in infectious disease and intensive care wards. Chloramine was so disliked that the in-use test could not be carried out. In the infectious disease ward the total bacterial colony counts of the floors (disinfected once a day) were twice as high as those of the intensive care ward (disinfected 3 times a day) during the use of the phenolic and chlorine-bromine disinfectants. The frequent cleaning routine seemed thus to have an effect on the microbial contamination of the floors. The same difference was found in the contamination of the other non-vertical surfaces although they were disinfected only once a day in both wards. In both wards the total bacterial colony counts of all non-vertical surfaces were lower during the use of halogen compounds than during the use of the phenolic disinfectant. The staff, however, complained of the irritation of the skin and the mucous membranes when using chlorine disinfectants.

Failure of hand disinfection with frequent hand washing: a need for prolonged field studies.

In a prolonged field trial a 4% chlorhexidine digluconate detergent scrub (Hibiscrub(R)), that had earlier proved to be an effective hand disinfectant, was studied in hospital wards. Finger tips were found to harbour more bacteria than the hand dorsum and the samples collected from them yielded more information on the bacteriological and dermatological effects of hand disinfectants in practice.In wards with a relatively low hand-washing frequency (less than 20 times in 8 hours) the bacteriological results resembled those obtained by in-use tests with volunteers. In the neonatal unit where the hand washing frequency was remarkably high, even occasionally over 100 times/8 h shift, an increase in the bacterial colony counts of the majority of the staff was recorded both before and after hand washing already after using the preparation for 1 week. Age, occupation and hand-washing frequency all correlated with the bacteriological results. Twenty-seven out of 37 persons complained of side effects such as wounds of finger tips and redness or heavy drying of the skin. Wounds, particularly on finger tips, resulted in the failure of disinfection. An increase in bacterial counts was sometimes noted without any dermatological or subjective changes. Drying of the skin was complained of less often when no increase in skin bacteria occurred.After the changeover of washing practice to a detergent followed by a rinse with spirit solution containing chlorhexidine and glycerol a decrease was recorded in the bacterial counts. It is concluded that more attention should be paid to long-term testing of hand washing and disinfection methods to ensure optimum final results in practice. It is obvious that the knowledge obtained from short time in-use testing cannot be applied to all conditions of use.

The Venflon cannula as a sideport of infection.

The possible role of infection through the valved sideport of Venflon cannulae was evaluated by one individual who followed an identical procedure of placing a syringe into the sideport and injecting saline solution. Basic aseptic techniques were used in a contaminated, busy environment. No bacterial growth was found in either anaerobic or aerobic culture media following a total of 1500 injections. The experiment shows that if the measures used could be applied, infection through the sideport would be minimal.

Antistatic treatment for reducing airborne contamination of insulating materials in intensive care.

In an effort to reduce airborne contamination by Staphylococcus epidermidis harboured on emitted skin scales, items used in patient care were studied as regards bacterial contamination and electrical resistance. An alcoholic benzalkonium chloride sodium was used to coat stopcocks, latex drains, silicon drains and plastic covering. Static electricity did not accumulate when the insulating resistance was less than 10(9) to 10(10) ohms. Study items not treated with the antistatic solution had resistances of greater than 2 x 10(12) ohms, which decreased to 2 x 10(6) to 8 x 10(10) ohms following antistatic treatment. The resistance of the silicon drain before and after antistatic exposure remained unchanged; an increase in its weight after treatment suggests absorption rather than the solution adhering to its surface. Statistically significantly lowered aerobic bacterial colony counts occurred from study items antistatistically treated as compared to those items left untreated. The coating of an entire room and its metal contents failed to decrease bacterial contamination. The results suggest that coating of insulating objects with an antistatic solution will reduce electrical resistance and thereby airborne bacterial contamination.

Studies on the effects of ionization on bacterial aerosols in a burns and plastic surgery unit.

The effect of the ionization of the air on the decay of bacterial aerosols was studied in a Burns and Plastic Surgery Unit. Ions were generated by free corona needles. The air content of bacteria measured by settle plates was found to be smaller during the ionization period than during the controls period. The number of individual phage typed Staph. aureus strains was especially found to be lower during ionization. The opposite potential increased the disappearance of bacteria from the air. The size of skin particles carrying bacteria is not optimum, but the results obtained show that the ionization may have applications in controlling airborne infection.