Effect of unidirectional airflow ventilation on surgical site infection in cardiac surgery: environmental impact as a factor in the choice for turbulent mixed air flow

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 are equipped with heating, ventilation and air conditioning (HVAC) systems to prevent airborne contamination of the wound, either through turbulent mixed air flow (TMA) or unidirectional air flow (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-centre cohort study collected data from 1288 patients who underwent open heart surgery over 2 years. During the two study periods, institutional SSI preventive measures remained the same, with the exception of the type of HVAC system that was used.

FINDINGS

Using multi-variable logistic regression analysis that considered confounding factors (diabetes, obesity, duration of surgery, and re-operation), the hypothesis that TMA is an independent risk factor for SSI was rejected (odds ratio 0.9, 95% confidence interval 0.4-1.8; P>0.05). It was not possible to demonstrate the preventive effect of UDAF on the incidence of SSI in patients undergoing open heart surgery when compared with TMA.

CONCLUSION

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

Heat sterilisation dramatically reduces filter efficiency of the majority of FFP2 and KN-95 respirators

BACKGROUND

Because of the enormous demand for personal protective equipment and especially respiratory protective devices (respirators) during the initial phase of the corona pandemic shortages arose. Sterilisation of used respirators can reduce these shortages. In our study, respirator testing was carried out after only one sterilisation cycle.

AIM

To determine if steam sterilisation and reuse could be safely applied for used respirators.

METHODS

In a cabinet an aqueous solution of NaCl (0.02% w/v) was nebulized and passed through a sample of the material of a respirator. Passing particle concentrations were measured directly from the cabinet and via the filter material of the respirator for particles ≥ 0.3 μm, ≥ 0.5 μm and ≥ 1.0 μm.

FINDINGS

only three out of ten steam sterilised respirators met the requirements of 94% filtration efficiency.

CONCLUSION

The results prove that heat sterilisation cannot be generically applied for reuse of respirators safely.