Evaluation and optimum use of directed horizontal filtered air flow for surgeries.

Airborne micro-organisms, a suspected cause of surgical wound infection, are significantly reduced by the use of filtered unidirectional air flow (UAF) in operating rooms. A horizontal UAF system was installed at UCLA for evaluation and to determine procedures which would optimize its use. Major findings are listed: though the air flow was found to be somewhat turbulent and non-uniform in velocity downstream from the filter-bank entrance, the gross flow direction was maintained throughout the protected region; airborne particles were swept downstream with little vertical drop and no large scale recirculation; proper orientation and placement of objects in the clean air stream maximized its purging effect; correlation of non-viable with viable particle counts was not possible; better control of sources of contamination, particularly the operating team, would further reduce the potential for airborne infection; as yet there is no definitive proof that the addition of filtered UAF in a modern operating room reduces occurrences of deep wound sepsis.