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Comparison of three distinct surgical clothing systems for protection from air-borne bacteria: A prospective observational study

Comparison of three distinct surgical clothing systems for protection from air-borne bacteria: A... Background: To prevent surgical site infection it is desirable to keep bacterial counts low in the operating room air during orthopaedic surgery, especially prosthetic surgery. As the air-borne bacteria are mainly derived from the skin flora of the personnel present in the operating room a reduction could be achieved by using a clothing system for staff made from a material fulfilling the requirements in the standard EN 13795. The aim of this study was to compare the protective capacity between three clothing systems made of different materials – one mixed cotton/ polyester and two polyesters - which all had passed the tests according to EN 13795. Methods: Measuring of CFU/m air was performed during 21 orthopaedic procedures performed in four operating rooms with turbulent, mixing ventilation with air flows of 755 – 1,050 L/s. All staff in the operating room wore clothes made from the same material during each surgical procedure. Results: The source strength (mean value of CFU emitted from one person per second) calculated for the three garments were 4.1, 2.4 and 0.6 respectively. In an operating room with an air flow of 755 L/s both clothing systems made of polyester reduced the amount of CFU/m significantly compared to the clothing system made from mixed material. In an operating room with air intake of 1,050 L/s a significant reduction was only achieved with the polyester that had the lowest source strength. Conclusions: Polyester has a better protective capacity than cotton/polyester. There is need for more discriminating tests of the protective efficacy of textile materials intended to use for operating garment. Keywords: Orthopaedic surgery, Protective clothing, Ventilation Background possible to use ventilation to dilute and/or swipe away Since the 1970s, it is a generally accepted view that the the bacteria-carrying particles in the air [5]. One can amount of bacteria in the operating room air should be also use a clothing system made of a material that is as low as possible in orthopaedic prosthetic surgery to so dense that the bacteria-carrying skin scales which prevent postoperative infections related to the implant. continuously come loose from the outer skin layer does The air-borne bacteria that reach the surgical site are not reach the air in the room [6,7]. mainly staphylococci derived from the skin flora of Since the year 2009 there is a European standard, EN the personnel present in the operating room. This was 13795, which describes the requirements imposed on presented in historic landmark articles by Charnley and the material density for a dress to be classified as a so- Lidwell [1,2] and has later been confirmed by other called Clean Air Suite [8]. In Swedish orthopaedic sur- authors [3,4]. In order to achieve low bacteria levels it is gery the most commonly used dress for operating room personnel is made of cotton/polyester. This material meets the standard requirements when it is brand new. * Correspondence: ann.tammelin@sll.se Department of Medicine, Solna (MedS), Unit of Infectious Diseases, The clothes are intended for multiple use and therefore Karolinska Institutet, Stockholm, Sweden 3 undergo a large number of washing processes during Department of Infection Control and Hospital Hygiene, Stockholm County their lifetime. The repeated washing could lead to a Council, Södersjukhuset, hiss S, plan −1, Stockholm SE-118 83, Sweden Full list of author information is available at the end of the article © 2012 Tammelin et al.; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Tammelin et al. Patient Safety in Surgery 2012, 6:23 Page 2 of 6 http://www.pssjournal.com/content/6/1/23 change of the material properties so that it becomes more permeable to bacteria-carrying particles. In some Swedish hospitals the operating room staff use dresses made of polyester, and there are indications that this garment would have a better protective effect than the standard clothing system made from the mixed material [5]. Based on the measured total amount of Colony Forming Units (CFU) per cubic meter (m ) air, the air flow and the number of people in the operating room it is possible to calculate the protective efficacy of a surgical clothing system in terms of source strength (mean value of CFU emitted from one person per sec- ond), which makes it possible to compare the protect- ive capacity of clothing made from different materials Figure 1 Operating staff dressed in clothes made from mixed [9]. material. In this study we wanted to investigate whether there was any difference in protective efficacy between cloth- ing systems made of polyester (two different materials) Polyester material (Mertex HK-1069KS , Mercan AB) and a mixed material (cotton/polyester), all of which consisting of 99% polyester and 1% carbon fibre. Weight meet the requirements of standard EN 13795. We also 100 gram per square meter. wanted to investigate if there was reason to believe that Polyester material (Selguard 4 , 807TK-310, Martinson the protective effect may be impaired in garments of Konfektion AB) consisting of 99% polyester and 1% mixed material which had been washed repeatedly. carbon fibre. Weight 120 gram per square meter. In operating room 1 we made a comparison between the routinely used dresses that had been washed for sev- Methods eral times (up to a maximum of 100 washing processes) Setting picked from the shelf (two operations) and brand new The study was conducted at South Hospital (Södersju- dresses (two operations), all made from the mixed ma- khuset), Stockholm, in 2010. South Hospital is an emer- terial. In operating room 2 air-samples were taken dur- gency hospital with approximately 650 beds where about ing three operations with all staff using washed dresses 6,000 orthopaedic surgical procedures are performed made from the mixed material. each year. In operating rooms 3 and 5 sampling was performed A total of 21 orthopaedic surgical procedures per- during six surgical procedures where staff wore dresses formed in the operating rooms 1, 2, 3 and 5 were made from mixed material and eight surgical procedures included in the study. The operating theatres had turbu- where they used dresses made from polyester. lent, mixing ventilation with air flow (air intake) at 996, 965, 1,050 and 755 L/s respectively. The selection of sur- gical procedures was haphazard and made mainly by the Sample collection and microbiological analysis availability of personnel who could perform the sample Measurements of CFU/m air were carried out by collection. personnel from the laboratory for clinical microbiology All present staff (5 – 9 persons) in the operating room at the Karolinska University Hospital in Huddinge. Air wore clothes made from the same material during each sampling was made with a Sartorius MD8 air sampler surgical procedure. All dresses were of the same design with a flow of 100 L/min for periods of 10 minutes (thus i.e. the trousers had cuffs at the leg and the short- sampled air volume of 1.0 m ). Air was sucked over a sleeved shirts had cuffs at the arm, bottom and neckline sterile gelatine filter placed as near the surgical wound (Figure 1). as possible (approximately 20 – 50 cm). (Figure 2) At each operation air was sucked for four-six ten-minute Clothing systems periods. Each gelatine filter was placed on a sterile blood The three clothing systems studied were made from the agar plate that was incubated at 35°C for two days. The following fabrics: number of bacterial colonies on the plate was then ® 3 Mixed material (Mertex P-3477 , Mercan AB) consist- counted and expressed as CFU/m air. From the four-six ing of 69% cotton, 30% polyester, and 1% carbon fibre. samples a mean value of CFU/m air was calculated for Weight 150 gram per square meter. each operation. Tammelin et al. Patient Safety in Surgery 2012, 6:23 Page 3 of 6 http://www.pssjournal.com/content/6/1/23 Table 1 Mean values of CFU/m air during four operations in operating room 1 when all persons present were dressed in a surgical clothing system of mixed material (69% cotton, 30% polyester, 1% carbon fibre) which was either washed repeatedly or brand new Type of Clothing Number of CFU/m3 surgery persons air mean present (min-max) Hip fracture Mixed material, 7 38.3 (17–55) washed Hip fracture Mixed material, 8 20.2 (9–32) washed Lower leg fracture Mixed material, 7 16.7 (13–24) brand new Lower leg fracture Mixed material, 7 31.8 (8–50) brand new Figure 2 Position of holder for sterile gelatine filter. values (CFU/m ) were 27.7 and 34.5 respectively. The difference was not significant (Tables 1, 2, 3 and 4). Data analysis Mann–Whitney U-test, two-sided, was used when com- paring means of CFU/m air from operations when Mixed material (cotton/polyester) and polyester washed and brand new clothes made from mixed mater- When we compared the results obtained with clothes ial were used. made from mixed material (washed and brand new) and Mann–Whitney U-test, one-sided, was used when the two polyesters (added results from both HK-1069KS comparing means of CFU/m air from operations when and 807TK-310) in operating rooms 3 and 5 there was clothes made from mixed material and polyester were no significant difference between mixed material and used, with the hypothesis that polyester would give polyester in operating room 3 but the difference was sig- lower counts of CFU/m air. nificant in room 5 (Tables 3 and 4). Mann–Whitney U-test, one-sided, was used when When we added all results (from room 3 and 5) comparing means of source strength calculated from obtained with the clothing system made from mixed operations when clothes made from mixed material and material and compared with the added results (from polyester were used, with the hypothesis that polyester room 3 and 5) obtained with each of the clothing would result in lower source strength. The same test systems made from polyester (HK-1069KS and 807TK- was used when comparing source strength for the two 310 respectively) the difference in CFU/m was signifi- polyesters, with the hypothesis that Selguard 4 , 807TK- cantly lower in favour of each of the polyesters 310 would have a lower source strength. (Tables 3 and 4). P-values ≤ 0.05 were considered significant. Due to few operations included it was not possible to tell if the difference in number of CFU/m was signifi- Ethical approval cant when making the same comparison between mixed This study has not been subject to judgement by an eth- ics committee as it was regarded as a quality project. Table 2 Mean values of CFU/m air during three operations in operating room 2 when all persons present were dressed in a surgical clothing system of mixed Results material (69% cotton, 30% polyester, 1% carbon fibre) Washed and brand new dresses made from mixed which was washed repeatedly material (cotton/polyester) Type of surgery Clothing Number of CFU/m3 In operating room 1 we found no significant differences persons airmean present (min-max) in the number of CFU/m air between the two opera- Wrist Mixed material, 5 41.3 (9–65) tions in which staff wore washed clothes (mean 29.3) washed and the two when brand new ones were worn (mean Hamstring Mixed material, 7 24.0 (17–38) 24.3), all made from mixed material (Table 1). muscle washed When comparing all operations performed with staff Shoulder Mixed material, 7 31.0 (11–45) dressed in washed and brand new clothes made from washed mixed material irrespective of operating room the mean Tammelin et al. Patient Safety in Surgery 2012, 6:23 Page 4 of 6 http://www.pssjournal.com/content/6/1/23 Table 3 Mean values of CFU/m air during seven Table 5 Source strength (mean value of CFU emitted operations in operating room 3 when all persons present from one person per second) calculated for each clothing were dressed in surgical clothing systems of either mixed system during each operation material (69% cotton, 30% polyester, 1% carbon fibre) or Clothing system Source strength polyester (99% polyester, 1% carbon fibre) of two kinds (CFU/s) mean (min – max) Type of surgery Clothing Number of CFU/m3 persons air mean Mixed material, washed 4.2 (1.5 – 8.0) present (min-max) Mixed material, brand new 4.0 (2.4 – 5.0) Back, infected Mixed material, 7 9.8 (1–20) Polyester HK-1069KS 2.4 (0.8 – 4.8) washed Polyester 807TK-310 0.6 (0.5 – 0.8) Ankle Mixed material, 7 34.7 (20–49) washed Shoulder, clavicle Mixed material, 7 22.2 (14–37) washed Discussion According to the company (Textilia AB) that supplies Ankle Polyester HK-1069KS 8 12.7 (7–16) clothing to the hospital the density of Clean Air Suits Hip replacement Polyester HK-1069KS 6 27.2 (10–40) made from mixed material has been tested after 120 Hip replacement Polyester 807TK-310 7 3.2 (1–6) washing processes and was then found to meet the stan- Ankle fracture Polyester 807TK-310 7 5.3 (2–12) dard's requirements. The supplier warrants that each piece of garment is eliminated after a maximum of 100 washing processes. Our results support that there is no material and each of the polyesters for the two operating significant difference between the washed clothes rou- rooms 3 and 5 separately. tinely used during orthopaedic surgery and the brand new clothes, both made from mixed material, with re- Source strength spect to their ability to protect the patient from air- Source strength was calculated for the different clothing borne bacteria coming from the personnel. systems used (washed and brand new mixed material, Already in 1990 Whyte et al. showed that surgical polyester HK-1069KS and polyester 807TK-310). The clothing made of polyester was superior to cotton cloth- difference between new and washed clothes made from ing with respect to reduction of air-borne bacteria in an mixed material was not significant, neither was the dif- operating room with conventional, turbulent, mixing ference between clothes made from mixed material and ventilation [10]. The same was shown by Verkkala et al. polyester HK-1069KS or between the two polyesters. in 1998 [11]. In spite of that, cotton has not been The difference between mixed material and polyester replaced by polyester but by the mixed material (cotton/ 807TK-310 was significant. (Table 5) polyester) for routine use in Swedish orthopaedic sur- gery. This might partly be explained by promising results Table 4 Mean values of CFU/m air during seven from studies with surgical clothing made from mixed operations in operating room 5 when all persons present material in operating theatres supplied with partial uni- were dressed in surgical clothing systems of either mixed directional air flow [12]. As most operations for hip and material (69% cotton, 30% polyester, 1% carbon fibre) or knee replacement in Sweden still are performed in oper- polyester (99% polyester, 1% carbon fibre) of two kinds ating theatres with mixing, turbulent air flow it seems Type of surgery Clothing Number of CFU/m3 important to investigate whether it is possible to im- persons air mean present (min-max) prove air quality in this kind of operating rooms by Hip Mixed material, 7 46.5 (40–58) using polyester garment. brand new Our overall results show that a dress in polyester is Knee Mixed material, 8 49.0 (37–88) able to reduce bacterial counts in the operating room air brand new to a significantly greater extent than the commonly used Knee Mixed material, 6 28.6 (12–50) dress in mixed material even though the material used brand new for garment of each type meets the requirements for Knee Polyester HK-1069KS Not noted 7.3 (5–10)* Clean Air Suite due to the standard EN 13795. The test replacement methods specified in the standard thus seems suitable to Knee Polyester HK-1069KS 7 7.0 (1–13) outrange materials that are totally inappropriate for use Knee Polyester 807TK-310 8 5.2 (2–8) in surgical clothing systems intended to be medical Knee Polyester 807TK-310 7 4.3 (2–9) devices, i.e. clothes that should protect the patient from air-borne bacteria. For materials passing the tests it is * Value not used in calculation of source strength (Table 4). though impossible to distinguish between those having Tammelin et al. Patient Safety in Surgery 2012, 6:23 Page 5 of 6 http://www.pssjournal.com/content/6/1/23 source strengths of below 1 and around 4 CFU/s re- choosing a clothing system it is desirable that the user spectively. Under real conditions in the operating room could expect the protective capacity to be stable. this difference in source strength leads to differences in In this study only a small number of surgical proce- CFU/m air ranging from below 5 to around 50. dures with each clothing system were investigated and The operating rooms 1, 2 and 3 all had an air intake of the results need to be confirmed by further studies. An- approximately 1,000 L/s whereas room 5 had an intake other limitation could be that different kind of opera- of only 755 L/s. The lower air-flow in room 5 has prob- tions were studied as activity and performance differs ably resulted in the higher mean value of 41.4 CFU/m which might lead to higher or lower levels of bacterial (min 12, max 88) compared to the mean value of 27.0 contamination of the air. It is however noteworthy that CFU/m (min 1, max 65) in the rooms 1, 2 and 3 when the CFU-levels could differ almost two-fold between adding results from all operations performed with operations of the same kind performed in the same op- dresses in the mixed material. This supports the theory erating room with the same number of staff present and that a higher air intake helps to keep low levels of bac- using the same kind of clothing, which indicates that teria in the air by dilution. The difference in air intake there are both low and high shedders of skin scales affected the final results as shown below. among the staff (Table 1). Our results indicate that with a conventional, turbu- lent, mixing ventilation with an air flow of about 1,000 Conclusions L/s (15–20 air changes per hour) it is not possible to ex- Clothing systems made of polyester has a better protect- pect a microbiological air quality with the desired level ive capacity than those made of cotton/polyester. There of <10 CFU/m when using clothes in mixed material is need for more discriminating tests of the protective ef- giving a mean source strength of about 4 CFU/s, al- ficacy of textile materials intended to use for operating though the material meets the requirements in EN garment. Of the two polyester fabrics tested one - Selguard 4 , Competing interests 807TK-310 - showed to result in a significantly lower None of the authors have any competing interests. source strength than the mixed material. If the standard Authors’ contributions EN 13795 should be able to show such differences in AT conceived of the study, and participated in its design and coordination protective efficacy it has to be completed with more and drafted the manuscript. BL participated in the design of the study and sophisticated test methods. Today we have to rely on helped to draft the manuscript. BR participated in the design of the study and its coordination and participated in the sampling during operations and investigations in dispersal chambers or operating thea- helped to draft the manuscript. All authors read and approved the final tres to find them. manuscript. In this study the operating rooms 3 and 5 hade air flows of 1,050 and 755 L/s respectively. In room 5 we Acknowledgements obtained a higher mean value of CFU/m than in room To the staff from the laboratory for clinical microbiology at the Karolinska University Hospital in Huddinge for skilful technical assistance. 3 when dresses in mixed material were used (41.4 ver- sus 22.2 for all operations) and the reduction achieved Author details by polyester garment was significant in room 5 but not Department of Medicine, Solna (MedS), Unit of Infectious Diseases, Karolinska Institutet, Stockholm, Sweden. Department of Energy and in room 3. The result is not surprising. With a high Environment, Division of Building Services Engineering, Chalmers University baseline the air quality was improved also when results 3 of Technology, Göteborg, Sweden. Department of Infection Control and with the polyester Mertex HK-1069KS were included Hospital Hygiene, Stockholm County Council, Södersjukhuset, hiss S, plan −1, Stockholm SE-118 83, Sweden. although this polyester had a lower protective capacity. In room 3 with a lower baseline the number of opera- Received: 16 August 2012 Accepted: 8 October 2012 tions with dresses made from Selguard 4 , 807TK-310 Published: 15 October 2012 unfortunately were too few to show a significant reduc- tion. We are however convinced that this fabric with a References 1. Charnley J: Postoperative infection after total hip replacement with mean source strength of 0.6 CFU/s has contributed to a special reference to air contamination in the operating room. Clin Orthop mean value of 4.3 CFU/m for the two operations Relat Res 1972, 87:167–187. where it was used although the difference was not 2. Lidwell OM: Air, antibiotics and sepsis in replacement joints. J Hosp Inf 1988, 11 Suppl C:18. significant. 3. Whyte W, Hambraeus A, Laurell G, Hoborn J: The relative importance of It is worth notice that the source strength for the the routes and sources of wound contamination during general surgery clothing systems made from mixed material and from II. Airborne. J Hosp Inf 1992, 22:(1)41–54. 4. Edmiston CE, Seabrook GR, Cambria RA, Brown KR, Lewis BD, Sommers JR, the polyester Mertex HK-1069KS varied substantially Krepel CJ, Wilson PJ, Sinski S, Towne JB: Molecular epidemiology of between operations whereas the variation was less for microbial contamination in the operating room environment: Is there a the polyester Selguard 4 , 807TK-310 (Table 5). When risk for infection? Surgery 2005, 138(4):573–579. Tammelin et al. Patient Safety in Surgery 2012, 6:23 Page 6 of 6 http://www.pssjournal.com/content/6/1/23 5. Nordenadler J: Some observations on safety ventilation in operating rooms. Royal Institute of Technology, Stockholm, Building Services Engineering: PhD thesis; 2010. 6. Tammelin A, Domicel P, Hambraeus A, Ståhle E: Dispersal of methicillin- resistant Staphylococcus epidermidis by staff in an operating suite for thoracic and cardiovascular surgery: relation to skin carriage and clothing. J Hosp Inf 2000, 44:119–126. 7. Reinmüller B, Ljungqvist B: Evaluation of cleanroom garments in a dispersal chamber – some observations. Eur J Parent Sci 2000, 5:55–58. 8. European Committee for Standardization, European Standard EN 13795, ICS 11.140. http://www.sis.se/hälso-och-sjukvård/sjukvårdstextilier-allmänt/ss-en- 9. Ljungqvist B, Reinmüller B, Nordenadler J: Performance of clothing systems in the context of operating rooms: a question of patient safety. Clean Air and Containment Review 2011, 7:10–13. 10. Whyte W, Hamblen DL, Kelly IG, Hambraeus A, Laurell G: An investigation of occlusive polyester surgical clothing. J Hosp Inf 1990, 15:363–374. 11. Verkkala K, Eklund A, Ojajärvi J, Tiittanen L, Hoborn J, Mäkelä P: The conventionally ventilated operating theatre and air contamination control during cardiac surgery – bacteriological and particulate matter control garment options for low level contamination. Eur J Card-thor Surg 1998, 14:206–210. 12. Tammelin A, Hambraeus A, Ståhle E: Routes and sources of Staphylococcus aureus transmitted to the surgical wound during cardiothoracic surgery: Possibility of preventing wound contamination by use of special scrub suits. Inf Cont Hosp Epid 2001, 22:338–346. doi:10.1186/1754-9493-6-23 Cite this article as: Tammelin et al.: Comparison of three distinct surgical clothing systems for protection from air-borne bacteria: A prospective observational study. Patient Safety in Surgery 2012 6:23. 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Comparison of three distinct surgical clothing systems for protection from air-borne bacteria: A prospective observational study

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Springer Journals
Copyright
Copyright © 2012 by Tammelin et al.; licensee BioMed Central Ltd.
Subject
Medicine & Public Health; Surgery
eISSN
1754-9493
DOI
10.1186/1754-9493-6-23
pmid
23068884
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Abstract

Background: To prevent surgical site infection it is desirable to keep bacterial counts low in the operating room air during orthopaedic surgery, especially prosthetic surgery. As the air-borne bacteria are mainly derived from the skin flora of the personnel present in the operating room a reduction could be achieved by using a clothing system for staff made from a material fulfilling the requirements in the standard EN 13795. The aim of this study was to compare the protective capacity between three clothing systems made of different materials – one mixed cotton/ polyester and two polyesters - which all had passed the tests according to EN 13795. Methods: Measuring of CFU/m air was performed during 21 orthopaedic procedures performed in four operating rooms with turbulent, mixing ventilation with air flows of 755 – 1,050 L/s. All staff in the operating room wore clothes made from the same material during each surgical procedure. Results: The source strength (mean value of CFU emitted from one person per second) calculated for the three garments were 4.1, 2.4 and 0.6 respectively. In an operating room with an air flow of 755 L/s both clothing systems made of polyester reduced the amount of CFU/m significantly compared to the clothing system made from mixed material. In an operating room with air intake of 1,050 L/s a significant reduction was only achieved with the polyester that had the lowest source strength. Conclusions: Polyester has a better protective capacity than cotton/polyester. There is need for more discriminating tests of the protective efficacy of textile materials intended to use for operating garment. Keywords: Orthopaedic surgery, Protective clothing, Ventilation Background possible to use ventilation to dilute and/or swipe away Since the 1970s, it is a generally accepted view that the the bacteria-carrying particles in the air [5]. One can amount of bacteria in the operating room air should be also use a clothing system made of a material that is as low as possible in orthopaedic prosthetic surgery to so dense that the bacteria-carrying skin scales which prevent postoperative infections related to the implant. continuously come loose from the outer skin layer does The air-borne bacteria that reach the surgical site are not reach the air in the room [6,7]. mainly staphylococci derived from the skin flora of Since the year 2009 there is a European standard, EN the personnel present in the operating room. This was 13795, which describes the requirements imposed on presented in historic landmark articles by Charnley and the material density for a dress to be classified as a so- Lidwell [1,2] and has later been confirmed by other called Clean Air Suite [8]. In Swedish orthopaedic sur- authors [3,4]. In order to achieve low bacteria levels it is gery the most commonly used dress for operating room personnel is made of cotton/polyester. This material meets the standard requirements when it is brand new. * Correspondence: ann.tammelin@sll.se Department of Medicine, Solna (MedS), Unit of Infectious Diseases, The clothes are intended for multiple use and therefore Karolinska Institutet, Stockholm, Sweden 3 undergo a large number of washing processes during Department of Infection Control and Hospital Hygiene, Stockholm County their lifetime. The repeated washing could lead to a Council, Södersjukhuset, hiss S, plan −1, Stockholm SE-118 83, Sweden Full list of author information is available at the end of the article © 2012 Tammelin et al.; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Tammelin et al. Patient Safety in Surgery 2012, 6:23 Page 2 of 6 http://www.pssjournal.com/content/6/1/23 change of the material properties so that it becomes more permeable to bacteria-carrying particles. In some Swedish hospitals the operating room staff use dresses made of polyester, and there are indications that this garment would have a better protective effect than the standard clothing system made from the mixed material [5]. Based on the measured total amount of Colony Forming Units (CFU) per cubic meter (m ) air, the air flow and the number of people in the operating room it is possible to calculate the protective efficacy of a surgical clothing system in terms of source strength (mean value of CFU emitted from one person per sec- ond), which makes it possible to compare the protect- ive capacity of clothing made from different materials Figure 1 Operating staff dressed in clothes made from mixed [9]. material. In this study we wanted to investigate whether there was any difference in protective efficacy between cloth- ing systems made of polyester (two different materials) Polyester material (Mertex HK-1069KS , Mercan AB) and a mixed material (cotton/polyester), all of which consisting of 99% polyester and 1% carbon fibre. Weight meet the requirements of standard EN 13795. We also 100 gram per square meter. wanted to investigate if there was reason to believe that Polyester material (Selguard 4 , 807TK-310, Martinson the protective effect may be impaired in garments of Konfektion AB) consisting of 99% polyester and 1% mixed material which had been washed repeatedly. carbon fibre. Weight 120 gram per square meter. In operating room 1 we made a comparison between the routinely used dresses that had been washed for sev- Methods eral times (up to a maximum of 100 washing processes) Setting picked from the shelf (two operations) and brand new The study was conducted at South Hospital (Södersju- dresses (two operations), all made from the mixed ma- khuset), Stockholm, in 2010. South Hospital is an emer- terial. In operating room 2 air-samples were taken dur- gency hospital with approximately 650 beds where about ing three operations with all staff using washed dresses 6,000 orthopaedic surgical procedures are performed made from the mixed material. each year. In operating rooms 3 and 5 sampling was performed A total of 21 orthopaedic surgical procedures per- during six surgical procedures where staff wore dresses formed in the operating rooms 1, 2, 3 and 5 were made from mixed material and eight surgical procedures included in the study. The operating theatres had turbu- where they used dresses made from polyester. lent, mixing ventilation with air flow (air intake) at 996, 965, 1,050 and 755 L/s respectively. The selection of sur- gical procedures was haphazard and made mainly by the Sample collection and microbiological analysis availability of personnel who could perform the sample Measurements of CFU/m air were carried out by collection. personnel from the laboratory for clinical microbiology All present staff (5 – 9 persons) in the operating room at the Karolinska University Hospital in Huddinge. Air wore clothes made from the same material during each sampling was made with a Sartorius MD8 air sampler surgical procedure. All dresses were of the same design with a flow of 100 L/min for periods of 10 minutes (thus i.e. the trousers had cuffs at the leg and the short- sampled air volume of 1.0 m ). Air was sucked over a sleeved shirts had cuffs at the arm, bottom and neckline sterile gelatine filter placed as near the surgical wound (Figure 1). as possible (approximately 20 – 50 cm). (Figure 2) At each operation air was sucked for four-six ten-minute Clothing systems periods. Each gelatine filter was placed on a sterile blood The three clothing systems studied were made from the agar plate that was incubated at 35°C for two days. The following fabrics: number of bacterial colonies on the plate was then ® 3 Mixed material (Mertex P-3477 , Mercan AB) consist- counted and expressed as CFU/m air. From the four-six ing of 69% cotton, 30% polyester, and 1% carbon fibre. samples a mean value of CFU/m air was calculated for Weight 150 gram per square meter. each operation. Tammelin et al. Patient Safety in Surgery 2012, 6:23 Page 3 of 6 http://www.pssjournal.com/content/6/1/23 Table 1 Mean values of CFU/m air during four operations in operating room 1 when all persons present were dressed in a surgical clothing system of mixed material (69% cotton, 30% polyester, 1% carbon fibre) which was either washed repeatedly or brand new Type of Clothing Number of CFU/m3 surgery persons air mean present (min-max) Hip fracture Mixed material, 7 38.3 (17–55) washed Hip fracture Mixed material, 8 20.2 (9–32) washed Lower leg fracture Mixed material, 7 16.7 (13–24) brand new Lower leg fracture Mixed material, 7 31.8 (8–50) brand new Figure 2 Position of holder for sterile gelatine filter. values (CFU/m ) were 27.7 and 34.5 respectively. The difference was not significant (Tables 1, 2, 3 and 4). Data analysis Mann–Whitney U-test, two-sided, was used when com- paring means of CFU/m air from operations when Mixed material (cotton/polyester) and polyester washed and brand new clothes made from mixed mater- When we compared the results obtained with clothes ial were used. made from mixed material (washed and brand new) and Mann–Whitney U-test, one-sided, was used when the two polyesters (added results from both HK-1069KS comparing means of CFU/m air from operations when and 807TK-310) in operating rooms 3 and 5 there was clothes made from mixed material and polyester were no significant difference between mixed material and used, with the hypothesis that polyester would give polyester in operating room 3 but the difference was sig- lower counts of CFU/m air. nificant in room 5 (Tables 3 and 4). Mann–Whitney U-test, one-sided, was used when When we added all results (from room 3 and 5) comparing means of source strength calculated from obtained with the clothing system made from mixed operations when clothes made from mixed material and material and compared with the added results (from polyester were used, with the hypothesis that polyester room 3 and 5) obtained with each of the clothing would result in lower source strength. The same test systems made from polyester (HK-1069KS and 807TK- was used when comparing source strength for the two 310 respectively) the difference in CFU/m was signifi- polyesters, with the hypothesis that Selguard 4 , 807TK- cantly lower in favour of each of the polyesters 310 would have a lower source strength. (Tables 3 and 4). P-values ≤ 0.05 were considered significant. Due to few operations included it was not possible to tell if the difference in number of CFU/m was signifi- Ethical approval cant when making the same comparison between mixed This study has not been subject to judgement by an eth- ics committee as it was regarded as a quality project. Table 2 Mean values of CFU/m air during three operations in operating room 2 when all persons present were dressed in a surgical clothing system of mixed Results material (69% cotton, 30% polyester, 1% carbon fibre) Washed and brand new dresses made from mixed which was washed repeatedly material (cotton/polyester) Type of surgery Clothing Number of CFU/m3 In operating room 1 we found no significant differences persons airmean present (min-max) in the number of CFU/m air between the two opera- Wrist Mixed material, 5 41.3 (9–65) tions in which staff wore washed clothes (mean 29.3) washed and the two when brand new ones were worn (mean Hamstring Mixed material, 7 24.0 (17–38) 24.3), all made from mixed material (Table 1). muscle washed When comparing all operations performed with staff Shoulder Mixed material, 7 31.0 (11–45) dressed in washed and brand new clothes made from washed mixed material irrespective of operating room the mean Tammelin et al. Patient Safety in Surgery 2012, 6:23 Page 4 of 6 http://www.pssjournal.com/content/6/1/23 Table 3 Mean values of CFU/m air during seven Table 5 Source strength (mean value of CFU emitted operations in operating room 3 when all persons present from one person per second) calculated for each clothing were dressed in surgical clothing systems of either mixed system during each operation material (69% cotton, 30% polyester, 1% carbon fibre) or Clothing system Source strength polyester (99% polyester, 1% carbon fibre) of two kinds (CFU/s) mean (min – max) Type of surgery Clothing Number of CFU/m3 persons air mean Mixed material, washed 4.2 (1.5 – 8.0) present (min-max) Mixed material, brand new 4.0 (2.4 – 5.0) Back, infected Mixed material, 7 9.8 (1–20) Polyester HK-1069KS 2.4 (0.8 – 4.8) washed Polyester 807TK-310 0.6 (0.5 – 0.8) Ankle Mixed material, 7 34.7 (20–49) washed Shoulder, clavicle Mixed material, 7 22.2 (14–37) washed Discussion According to the company (Textilia AB) that supplies Ankle Polyester HK-1069KS 8 12.7 (7–16) clothing to the hospital the density of Clean Air Suits Hip replacement Polyester HK-1069KS 6 27.2 (10–40) made from mixed material has been tested after 120 Hip replacement Polyester 807TK-310 7 3.2 (1–6) washing processes and was then found to meet the stan- Ankle fracture Polyester 807TK-310 7 5.3 (2–12) dard's requirements. The supplier warrants that each piece of garment is eliminated after a maximum of 100 washing processes. Our results support that there is no material and each of the polyesters for the two operating significant difference between the washed clothes rou- rooms 3 and 5 separately. tinely used during orthopaedic surgery and the brand new clothes, both made from mixed material, with re- Source strength spect to their ability to protect the patient from air- Source strength was calculated for the different clothing borne bacteria coming from the personnel. systems used (washed and brand new mixed material, Already in 1990 Whyte et al. showed that surgical polyester HK-1069KS and polyester 807TK-310). The clothing made of polyester was superior to cotton cloth- difference between new and washed clothes made from ing with respect to reduction of air-borne bacteria in an mixed material was not significant, neither was the dif- operating room with conventional, turbulent, mixing ference between clothes made from mixed material and ventilation [10]. The same was shown by Verkkala et al. polyester HK-1069KS or between the two polyesters. in 1998 [11]. In spite of that, cotton has not been The difference between mixed material and polyester replaced by polyester but by the mixed material (cotton/ 807TK-310 was significant. (Table 5) polyester) for routine use in Swedish orthopaedic sur- gery. This might partly be explained by promising results Table 4 Mean values of CFU/m air during seven from studies with surgical clothing made from mixed operations in operating room 5 when all persons present material in operating theatres supplied with partial uni- were dressed in surgical clothing systems of either mixed directional air flow [12]. As most operations for hip and material (69% cotton, 30% polyester, 1% carbon fibre) or knee replacement in Sweden still are performed in oper- polyester (99% polyester, 1% carbon fibre) of two kinds ating theatres with mixing, turbulent air flow it seems Type of surgery Clothing Number of CFU/m3 important to investigate whether it is possible to im- persons air mean present (min-max) prove air quality in this kind of operating rooms by Hip Mixed material, 7 46.5 (40–58) using polyester garment. brand new Our overall results show that a dress in polyester is Knee Mixed material, 8 49.0 (37–88) able to reduce bacterial counts in the operating room air brand new to a significantly greater extent than the commonly used Knee Mixed material, 6 28.6 (12–50) dress in mixed material even though the material used brand new for garment of each type meets the requirements for Knee Polyester HK-1069KS Not noted 7.3 (5–10)* Clean Air Suite due to the standard EN 13795. The test replacement methods specified in the standard thus seems suitable to Knee Polyester HK-1069KS 7 7.0 (1–13) outrange materials that are totally inappropriate for use Knee Polyester 807TK-310 8 5.2 (2–8) in surgical clothing systems intended to be medical Knee Polyester 807TK-310 7 4.3 (2–9) devices, i.e. clothes that should protect the patient from air-borne bacteria. For materials passing the tests it is * Value not used in calculation of source strength (Table 4). though impossible to distinguish between those having Tammelin et al. Patient Safety in Surgery 2012, 6:23 Page 5 of 6 http://www.pssjournal.com/content/6/1/23 source strengths of below 1 and around 4 CFU/s re- choosing a clothing system it is desirable that the user spectively. Under real conditions in the operating room could expect the protective capacity to be stable. this difference in source strength leads to differences in In this study only a small number of surgical proce- CFU/m air ranging from below 5 to around 50. dures with each clothing system were investigated and The operating rooms 1, 2 and 3 all had an air intake of the results need to be confirmed by further studies. An- approximately 1,000 L/s whereas room 5 had an intake other limitation could be that different kind of opera- of only 755 L/s. The lower air-flow in room 5 has prob- tions were studied as activity and performance differs ably resulted in the higher mean value of 41.4 CFU/m which might lead to higher or lower levels of bacterial (min 12, max 88) compared to the mean value of 27.0 contamination of the air. It is however noteworthy that CFU/m (min 1, max 65) in the rooms 1, 2 and 3 when the CFU-levels could differ almost two-fold between adding results from all operations performed with operations of the same kind performed in the same op- dresses in the mixed material. This supports the theory erating room with the same number of staff present and that a higher air intake helps to keep low levels of bac- using the same kind of clothing, which indicates that teria in the air by dilution. The difference in air intake there are both low and high shedders of skin scales affected the final results as shown below. among the staff (Table 1). Our results indicate that with a conventional, turbu- lent, mixing ventilation with an air flow of about 1,000 Conclusions L/s (15–20 air changes per hour) it is not possible to ex- Clothing systems made of polyester has a better protect- pect a microbiological air quality with the desired level ive capacity than those made of cotton/polyester. There of <10 CFU/m when using clothes in mixed material is need for more discriminating tests of the protective ef- giving a mean source strength of about 4 CFU/s, al- ficacy of textile materials intended to use for operating though the material meets the requirements in EN garment. Of the two polyester fabrics tested one - Selguard 4 , Competing interests 807TK-310 - showed to result in a significantly lower None of the authors have any competing interests. source strength than the mixed material. If the standard Authors’ contributions EN 13795 should be able to show such differences in AT conceived of the study, and participated in its design and coordination protective efficacy it has to be completed with more and drafted the manuscript. BL participated in the design of the study and sophisticated test methods. Today we have to rely on helped to draft the manuscript. BR participated in the design of the study and its coordination and participated in the sampling during operations and investigations in dispersal chambers or operating thea- helped to draft the manuscript. All authors read and approved the final tres to find them. manuscript. In this study the operating rooms 3 and 5 hade air flows of 1,050 and 755 L/s respectively. In room 5 we Acknowledgements obtained a higher mean value of CFU/m than in room To the staff from the laboratory for clinical microbiology at the Karolinska University Hospital in Huddinge for skilful technical assistance. 3 when dresses in mixed material were used (41.4 ver- sus 22.2 for all operations) and the reduction achieved Author details by polyester garment was significant in room 5 but not Department of Medicine, Solna (MedS), Unit of Infectious Diseases, Karolinska Institutet, Stockholm, Sweden. Department of Energy and in room 3. The result is not surprising. With a high Environment, Division of Building Services Engineering, Chalmers University baseline the air quality was improved also when results 3 of Technology, Göteborg, Sweden. Department of Infection Control and with the polyester Mertex HK-1069KS were included Hospital Hygiene, Stockholm County Council, Södersjukhuset, hiss S, plan −1, Stockholm SE-118 83, Sweden. although this polyester had a lower protective capacity. In room 3 with a lower baseline the number of opera- Received: 16 August 2012 Accepted: 8 October 2012 tions with dresses made from Selguard 4 , 807TK-310 Published: 15 October 2012 unfortunately were too few to show a significant reduc- tion. We are however convinced that this fabric with a References 1. Charnley J: Postoperative infection after total hip replacement with mean source strength of 0.6 CFU/s has contributed to a special reference to air contamination in the operating room. 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Patient Safety in SurgerySpringer Journals

Published: Oct 15, 2012

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