The Effect of Door Openings on Numbers of Colony Forming Units in the Operating Room during Hip Revision Surgery

Background: The aim of this study was to investigate the effect of door opening rates on air quality in the operation room during hip revision surgery by measuring the number of colony forming units per cubic meter (CFU/m 3 ). Methods: During 70 hip revision operations the number of CFU/m 3 was measured at four time points. Factors that may influence air quality were recorded, including the number of persons present, duration of surgery, and door opening rates. The measured CFU/m 3 was dichotomized as either acceptable (≤20 CFU/m 3 ) or not acceptable (>20 CFU/m 3 ). To determine whether door openings were associated with CFU/m 3 values, we used generalized linear mixed models to model the dichotomized repeatedly measured CFU/m 3 values. Results: The median number of door openings per operation was eight (range, 0–72), the median duration of surgery was 145 min (range, 60–285), and the median number of persons present during surgery was eight (range, 5–10). Adjusted for number of persons in the operation room and duration of surgery, the number of door openings per operation was associated (odds ratio [OR] 1.05 [95% confidence interval {CI} 1.02–1.09]; p = 0.003) with an unacceptable number of CFU/m 3 . Conclusions: In conclusion, a substantial association between number of door openings and an unacceptable number (>20) of CFU/m 3 was found. Adjusted for number of persons in the operation room and duration of surgery, every door opening increased the odds of unacceptable CFU/m 3 values by 5%. Number of persons present during surgery and duration of surgery were not related to CFU/m 3 .