Source strength as a measurement to define the ability of clean air suits to reduce airborne contamination in operating rooms

Surgical site infections after total hip and knee replacement are linked to the quality of the operating room (OR) air. Wearing tight occlusive clothing, effective ventilation, and correct working methods, are key interventions to obtain low bacterial concentrations in the OR air. The dry penetration test referred to the European standard (EN 13795-2:2019) is a screening method for materials used in operating clothes and can be used when selecting and comparing products. Source strength defined as the dispersal of bacteria-carrying particles from persons during activity, is a functional test of the products and has been calculated in a dispersal chamber and in operating rooms. We compared the results of dry penetration tests for five surgical clothing systems available on the Swedish market. We report experimental data on the function of the same products expressed as source strength calculated from results in dispersal chambers and in ORs during orthopaedic operations. All materials tested with dry penetration ≤ 50 cfu gave source strength values < 3 cfu/s for one person in the dispersal chamber, whereas the material of one product when laundered more than a hundred times gave a source strength in the dispersal chamber of up to 11 cfu/s. Source strength results in ORs were half the value of that in the dispersal chamber. The dry penetration test could predict the performance of clean air suits of the same design, but more studies are needed to obtain a more valid correlation. Requirements of source strength should be included in standards.