Background and purpose — The standard method for controlling operating room (OR) air quality is measuring bacteria-carrying particles per volume unit of air: colony forming units (CFU/m3). The result takes at least 2 days after sampling. Another method is real-time measurements of flu-orescing bioparticles per unit volume of air (FBP/dm3). We aimed to compare simultaneous measurements of FBP/50 dm3 and CFU/m3 during ongoing arthroplasty surgery.

Methods — 18 arthroplasties were performed in a modern OR with turbulent mixed airflow ventilation. The sampling heads of a BioAerosol Monitoring System (BAMS) and a microbiological active air sampler (Sartorius MD8 Air Sam-pler) were placed next to each other, and 6 parallel 10-minute registrations of FBP/50 dm3 and CFU/m3 were performed for each surgery. Parallel measurements were plotted against each other, Passing–Bablok nonparametric linear regression was performed, and the Spearman correlation coefficient (r) was calculated.

Results — The r between FBP ≥ 3 µm/50 dm3 and CFU/ m3 sampled for 96 x 10-minute intervals, was 0.70 (95% confidence interval [CI] 0.57–0.79). In the 25th percentile with the lowest 10-minute FBP ≥ 3µm/50 dm3, there were no CFU measurements with ≥ 10 and 4% with ≥ 5 CFU/m3. In the 75th percentile with the highest 10-minute FBP ≥ 3 µm/50 dm3, there were 58% CFU measurements with ≥ 10 and 88% with ≥ 5 CFU/m3. The r between FBP ≥ 3 µm/50 dm3 and CFU/m3 means sampled during 18 operations was 0.87 (CI 0.68–0.95).

Conclusion — Low FBP ≥ 3 µm/50 dm3 measured by BAMS indicates low CFU/m3; conversely, high FBP ≥ 3 µm/50 dm3 indicates high CFU/m3. Real-time measurements of FBP ≥ 3 µm/50 dm3 can be used as a supplement to CFU/m3 monitoring OR air bacterial load.