Reduction of Airborne Bacterial Burden in the OR by Installation of Unidirectional Displacement Airflow (UDF) Systems.
BACKGROUND
Intraoperative bacterial contamination is a major risk factor for postoperative wound infections. This study investigated the influence of type of ventilation system on intraoperative airborne bacterial burden before and after installation of unidirectional displacement air flow systems.


METHODS
We microbiologically monitored 1286 surgeries performed by a single surgical team that moved from operating rooms (ORs) equipped with turbulent mixing ventilation (TMV, according to standard DIN-1946-4 [1999], ORs 1, 2, and 3) to ORs with unidirectional displacement airflow (UDF, according to standard DIN-1946-4, annex D [2008], ORs 7 and 8). The airborne bacteria were collected intraoperatively with sedimentation plates. After incubation for 48 h, we analyzed the average number of bacteria per h, peak values, and correlation to surgery duration. In addition, we compared the last 138 surgeries in ORs 1-3 with the first 138 surgeries in ORs 7 and 8.


RESULTS
Intraoperative airborne bacterial burden was 5.4 CFU/h, 5.5 CFU/h, and 6.1 CFU/h in ORs 1, 2, and 3, respectively. Peak values of burden were 10.7 CFU/h, 11.1 CFU/h, and 11.0 CFU/h in ORs 1, 2, and 3, respectively). With the UDF system, the intraoperative airborne bacterial burden was reduced to 0.21 CFU/h (OR 7) and 0.35 CFU/h (OR 8) on average (p<0.01). Accordingly, peak values decreased to 0.9 CFU/h and 1.0 CFU/h in ORs 7 and 8, respectively (p<0.01). Airborne bacterial burden increased linearly with surgery duration in ORs 1-3, but the UDF system in ORs 7 and 8 kept bacterial levels constantly low (<3 CFU/h). A comparison of the last 138 surgeries before with the first 138 surgeries after changing ORs revealed a 94% reduction in average airborne bacterial burden (5 CFU/h vs. 0.29 CFU/h, p<0.01).


CONCLUSIONS
The unidirectional displacement airflow, which fulfills the requirements of standard DIN-1946-4 annex D of 2008, is an effective ventilation system that reduces airborne bacterial burden under real clinical conditions by more than 90%. Although decreased postoperative wound infection incidence was not specifically assessed, it is clear that airborne microbiological burden contributes to surgical infections.
Department of Hand, Plastic, and Reconstructive Surgery, Burn Center, BG Trauma Center Ludwigshafen, University of Heidelberg, Ludwigshafen, Germany.
Sebastian
S
Fischer
Division of Hospital Hygiene, Darmstadt Clinic, Darmstadt, Germany.
Martin
M
Thieves
Department of Plastic and Reconstructive Surgery, Burn Centre, BG University Hospital Bergmannsheil, Ruhr University Bochum, Bochum, Germany.
Tobias
T
Hirsch
Department of Hand, Plastic, and Reconstructive Surgery, Burn Center, BG Trauma Center Ludwigshafen, University of Heidelberg, Ludwigshafen, Germany.
Klaus-Dieter
KD
Fischer
Department of Hygiene, University of Applied Science, Giessen-Friedberg, Germany.
Helmine
H
Hubert
Department of Hygiene, University of Applied Science, Giessen-Friedberg, Germany.
Steffen
S
Beppler
Department of Hygiene, University of Applied Science, Giessen-Friedberg, Germany.
Hans-Martin
HM
Seipp
D000391:Air Microbiology / Q000592:standards; D001419:Bacteria / Q000302:isolation & purification; D015169:Colony Count, Microbial; D005858:Germany; D006801:Humans; D007432:Intraoperative Period; D009873:Operating Rooms / Q000592:standards; D013530:Surgical Wound Infection / Q000517:prevention & control; D014691:Ventilation / Q000295:instrumentation* / Q000592:standards