According to the company (Textilia AB) that supplies clothing to the hospital the density of Clean Air Suits made from mixed material has been tested after 120 washing processes and was then found to meet the standard'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 significant difference between the washed clothes routinely used during orthopaedic surgery and the brand new clothes, both made from mixed material, with respect to their ability to protect the patient from air-borne bacteria coming from the personnel.
Already in 1990 Whyte et al. showed that surgical clothing made of polyester was superior to cotton clothing with respect to reduction of air-borne bacteria in an operating room with conventional, turbulent, mixing ventilation . The same was shown by Verkkala et al. in 1998 . In spite of that, cotton has not been replaced by polyester but by the mixed material (cotton/polyester) for routine use in Swedish orthopaedic surgery. This might partly be explained by promising results from studies with surgical clothing made from mixed material in operating theatres supplied with partial unidirectional air flow . As most operations for hip and knee replacement in Sweden still are performed in operating theatres with mixing, turbulent air flow it seems important to investigate whether it is possible to improve air quality in this kind of operating rooms by using polyester garment.
Our overall results show that a dress in polyester is able to reduce bacterial counts in the operating room air to a significantly greater extent than the commonly used dress in mixed material even though the material used for garment of each type meets the requirements for Clean Air Suite due to the standard EN 13795. The test methods specified in the standard thus seems suitable to outrange materials that are totally inappropriate for use in surgical clothing systems intended to be medical devices, i.e. clothes that should protect the patient from air-borne bacteria. For materials passing the tests it is though impossible to distinguish between those having source strengths of below 1 and around 4 CFU/s respectively. Under real conditions in the operating room this difference in source strength leads to differences in CFU/m3 air ranging from below 5 to around 50.
The operating rooms 1, 2 and 3 all had an air intake of approximately 1,000 L/s whereas room 5 had an intake of only 755 L/s. The lower air-flow in room 5 has probably resulted in the higher mean value of 41.4 CFU/m3 (min 12, max 88) compared to the mean value of 27.0 CFU/m3 (min 1, max 65) in the rooms 1, 2 and 3 when adding results from all operations performed with dresses in the mixed material. This supports the theory that a higher air intake helps to keep low levels of bacteria in the air by dilution. The difference in air intake affected the final results as shown below.
Our results indicate that with a conventional, turbulent, mixing ventilation with an air flow of about 1,000 L/s (15–20 air changes per hour) it is not possible to expect a microbiological air quality with the desired level of <10 CFU/m3 when using clothes in mixed material giving a mean source strength of about 4 CFU/s, although the material meets the requirements in EN 13795.
Of the two polyester fabrics tested one - Selguard 4®, 807TK-310 - showed to result in a significantly lower source strength than the mixed material. If the standard EN 13795 should be able to show such differences in protective efficacy it has to be completed with more sophisticated test methods. Today we have to rely on investigations in dispersal chambers or operating theatres to find them.
In this study the operating rooms 3 and 5 hade air flows of 1,050 and 755 L/s respectively. In room 5 we obtained a higher mean value of CFU/m3 than in room 3 when dresses in mixed material were used (41.4 versus 22.2 for all operations) and the reduction achieved by polyester garment was significant in room 5 but not in room 3. The result is not surprising. With a high baseline the air quality was improved also when results with the polyester Mertex HK-1069KS® were included although this polyester had a lower protective capacity. In room 3 with a lower baseline the number of operations with dresses made from Selguard 4®, 807TK-310 unfortunately were too few to show a significant reduction. We are however convinced that this fabric with a mean source strength of 0.6 CFU/s has contributed to a mean value of 4.3 CFU/m3 for the two operations where it was used although the difference was not significant.
It is worth notice that the source strength for the clothing systems made from mixed material and from the polyester Mertex HK-1069KS® varied substantially between operations whereas the variation was less for the polyester Selguard 4®, 807TK-310 (Table 5). When choosing a clothing system it is desirable that the user could expect the protective capacity to be stable.
In this study only a small number of surgical procedures with each clothing system were investigated and the results need to be confirmed by further studies. Another limitation could be that different kind of operations were studied as activity and performance differs which might lead to higher or lower levels of bacterial contamination of the air. It is however noteworthy that the CFU-levels could differ almost two-fold between operations of the same kind performed in the same operating room with the same number of staff present and using the same kind of clothing, which indicates that there are both low and high shedders of skin scales among the staff (Table 1).