Microbiological aspects of clean room technology as applied to surgery, with special reference to unidirectional airflow systems

The microbiological aspects of clean room technology a s applied to surgery were reviewed. The following pertinent subject a reas were examined: (1) clean room technology per s e and its utilization for surgery, ( 2 ) microbiological monitoring of the clean room surgical environment, (3) clean rooms and their impact on operating room environmental microbiology, and (4) the effect of the technology on surgical wound infection rates. Conclusions were drawn for each topic investigated. SUMMARY AND OVERALL CONCLUSIONS In i ts formulation and initial applications, clean room technology was aimed a t controlling nonbiological environmental parameters. The demonstration of the clean room1 s value for the control of viable contamination in NASA programs and its merit in the reduction of postoperative wound infection rates a s interpreted from European studies provided the basic impetus for the transfer of the technology to the operating room. The transfer has, to date, not seen the development of a standard that i s definitive with respect to the microbial control afforded by clean rooms in the surgical context, Therefore, the environmental control provided by surgical clean rooms i s often described per existing standards relating to the control of nonviable particulates. However, the surgeon employing this technology i s not concerned about nonviable particulates (as were i ts originators and many of i ts present day practitioners), but, rather, he i s interested in the environmental microbiologic control it affords and the effect of such on wound infection. In line with the objective of microbiological control, the use of HEPA filtration, efficient at the submicron level, may not be necessary in light of data that indicate the preponderance of airborne surgical wound infection producing particles can probably be removed from incoming operating room a i r by fi l ters efficient in the retention of la rger size particles. Human beings, rather than the air-handling system, account for the major contribution of microbial contamination in the modern operating room. Recent studies of surgical apparel systems, cited a s effective microbial barr iers , tend to indicate the feasibility of the rigid control of human source microorganisms in the operating room, a s a technique capable of enhancing the clean room technology approach to reducing microbial contamination of the surgical wound. There exists a great danger in total reliance on clean rooms for environmental microbiologic control; they cannot be depended on to compensate totally for improperly applied o r faulty aseptic technique. Clean rooms, be they turbulent o r unidirectional flow, a r e not in themselves the final solution to problems of control of the operating room1 r microbiological environment, For maximum benefit, technology applied towards this goal murt be tailored to i t r rurgical ure. Rererrch in thir area i r not complete and efforts should be continued to define the most meaningful, effective and economical method8 for regulating the microbial environment of the operating room. It will require a large, controlled study to directly evaluate, in a statistically significant manner, t1 t effect of the clean room on the incidence of postoperative surgical wound infection. However, pertinent data do exist that point to the value of a reduced level of operating room airborne microbial contamination in lowering the incidence of wound infection far certain surgical situations. DEFINITION O F TERMS The following te rms a r e used throughout this document and therefore require special attention a s to definition: CLEAN ROOM An enclosed area employing control over (defined per Federal the particulate matter in a i r with temperaStandard 209 B (1973)) ture, humidity, and pressure control, a s required; with a particle count not to exceed a total of 100,000 particles per cubic foot (approximately 3500 per l i te r ) of a size 0. 5 pm and larger , o r 700 particles per cubic foot (approximately 25 per l i te r ) of a size 5.0 p m and larger . CLEAN AIR Air issued directly from a HEPA filter (see page 9 ) . The clean roome under discussion employ HEPA filtration, hence the te rms clean room and clean a i r will be used interchangeably. Other t e rms a r e defined a s they appear in the text.