The effect of Unidirectional Airflow ventilation on Surgical Site Infection in Cardiac Surgery: environmental impact as a factor in the choice for Turbulent Mixed Airflow

Background: Surgical site infection (SSI) in the form of postoperative deep sternal wound infection (DSWI) after cardiac surgery is a rare, but potentially fatal complication. In addressing this, the focus is on preventive measures as most risk factors for SSI are not controllable. Therefore operating rooms (OR) are equipped with heating, ventilation and air conditioning (HVAC) systems to prevent airborne contamination of the wound either through turbulent mixed airflow (TMA) or unidirectional airflow (UDAF).

Aim: To investigate if the risk for SSI after cardiac surgery was decreased after changing from TMA to UDAF.

Methods: This observational retrospective single-center cohort study collected data from 1288 patients who underwent open-heart surgery in two years. During the two study periods institutional SSI preventive measures were the same, with the exception of the type of HVAC system that was used.

Findings: Using multivariable logistic regression analysis taking into account confounding factors (diabetes, obesity, operation duration and re-operation) the hypothesis of TMA being an independent risk factor for SSI was rejected (odds ratio 0.9; 95% CI 0.4-1.8; P >0.05). Thus we could not demonstrate the preventive effect of UDAF on the incidence of SSIs in open-heart surgery when compared to TMA.

Conclusion: Based on our results the use of UDAF in open-heart surgery should be weighed against its low cost-effectiveness and negative environmental impact due to large electricity consumption. Reducing energy overuse by utilizing TMA for cardiac surgery can diminish the carbon footprint of ORs and hereby their contribution to climate-related health hazards.