Air contamination for predicting wound contamination in clean surgery: A large multicenter study

•We assessed correlations between 2 types of air sampling and wound contaminations. •We included 13 operating rooms of cardiac and orthopedic surgery in 10 health care facilities. •A strong correlation exists between air particle counts and microbial contamination. •Particle counting is a good surrogate of airborne microbiologic contamination. •Laminar airflow was associated with decreased air microbial contamination. Background The best method to quantify air contamination in the operating room (OR) is debated, and studies in the field are controversial. We assessed the correlation between 2 types of air sampling and wound contaminations before closing and the factors affecting air contamination. Methods This multicenter observational study included 13 ORs of cardiac and orthopedic surgery in 10 health care facilities. For each surgical procedure, 3 microbiologic air counts, 3 particles counts of 0.3, 0.5, and 5 μm particles, and 1 bacteriologic sample of the wound before skin closure were performed. We collected data on surgical procedures and environmental characteristics. Results Of 180 particle counts during 60 procedures, the median log10 of 0.3, 0.5, and 5 μm particles was 7 (interquartile range [IQR], 6.2-7.9), 6.1 (IQR, 5.4-7), and 4.6 (IQR, 0-5.2), respectively. Of 180 air samples, 50 (28%) were sterile, 90 (50%) had 1-10 colony forming units (CFU)/m3 and 40 (22%) >10 CFU/m3. In orthopedic and cardiac surgery, wound cultures at closure were sterile for 24 and 9 patients, 10 and 11 had 1-10 CFU/100 cm2, and 0 and 6 had >10 CFU/100 cm2, respectively (P < .01). Particle sizes and a turbulent ventilation system were associated with an increased number of air microbial counts (P < .001), but they were not associated with wound contamination (P = .22). Conclusions This study suggests that particle counting is a good surrogate of airborne microbiologic contamination in the OR. The best method to quantify air contamination in the operating room (OR) is debated, and studies in the field are controversial. We assessed the correlation between 2 types of air sampling and wound contaminations before closing and the factors affecting air contamination. This multicenter observational study included 13 ORs of cardiac and orthopedic surgery in 10 health care facilities. For each surgical procedure, 3 microbiologic air counts, 3 particles counts of 0.3, 0.5, and 5 μm particles, and 1 bacteriologic sample of the wound before skin closure were performed. We collected data on surgical procedures and environmental characteristics. Of 180 particle counts during 60 procedures, the median log10 of 0.3, 0.5, and 5 μm particles was 7 (interquartile range [IQR], 6.2-7.9), 6.1 (IQR, 5.4-7), and 4.6 (IQR, 0-5.2), respectively. Of 180 air samples, 50 (28%) were sterile, 90 (50%) had 1-10 colony forming units (CFU)/m3 and 40 (22%) >10 CFU/m3. In orthopedic and cardiac surgery, wound cultures at closure were sterile for 24 and 9 patients, 10 and 11 had 1-10 CFU/100 cm2, and 0 and 6 had >10 CFU/100 cm2, respectively (P < .01). Particle sizes and a turbulent ventilation system were associated with an increased number of air microbial counts (P < .001), but they were not associated with wound contamination (P = .22). This study suggests that particle counting is a good surrogate of airborne microbiologic contamination in the OR.