Conditions for air cleanliness in a unidirectional airflow ventilation, during orthopaedic joint replacement procedures.

Background: Microbiological air contamination in the operating room (OR) is associated with the risk of surgical site infections (SSIs) after joint replacement procedures. Recommendations define the level of microbiological air cleanliness by the number of colony-forming units (cfu) in an OR. Airborne microorganisms originate from the staff and unidirectional airflow (UDAF) ventilation is effective in the OR, providing filtered air to create ultraclean zones.

Aim: To evaluate the air cleanliness in the demarcation zone during joint replacement procedures and describe the limitations for optimal air cleanliness in an UDAF ventilation.

Methods: In a cross-sectional design, cfu were measured using active air sampling in an OR with UDAF. Comparative measures were taken between demarcation and outer zone, supplemented by observations of staff numbers, traffic flow and movements.

Findings: A total of 166 samples were collected during 20 arthroplasty procedures. There were significantly more cfus in the outer zone than in the demarcation zone (P < 0.001). The only significantly predictor associated for higher cfu counts were the numbers of persons in the outer zone (odds ratio: 2.566; 95% confidence interval: 1.306-5.044; P = 0.006). Observations associated with higher cfu counts were method or organisational related.

Conclusions: Air cleanliness in UDAF ventilation was better in the demarcation zone compared to the outer zone, and the number of persons in the outer zone was associated with decreased air cleanliness. Intraoperative movements could cause higher cfu counts in demarcation zone, but further studies are needed to evaluate the consequences of staff movements.