Impact of human-induced disturbances and supply air temperature on air-velocity distribution in a surgical micro-environment under unidirectional and mixing ventilation systems

BACKGROUND: Maintaining high indoor air quality in operating rooms is an important element of surgical site infection prevention. Although ventilation system performance may be assessed using both at-rest and operational measurements, airflow-related tests used for commissioning and acceptance procedures are commonly conducted under controlled conditions without patients or medical staff present. AIM: The aim of this study was to evaluate the influence of medical staff presence, patient presence, patient sex, and supply air temperature on air velocity within the surgical micro-environment. METHODS: Experiments were conducted in a laboratory operating room equipped with unidirectional airflow (UDAF) and mixing ventilation (MV) systems. Sixteen experimental scenarios were analysed, including at-rest conditions, thermal manikins representing medical staff, real volunteers representing patients (female and male patient groups) and supply-air temperatures of 19°C and 26°C. Air velocity was measured at five locations within the surgical micro-environment, with the sensors positioned 0.35 m above the operating table surface. FINDINGS: The presence of occupants significantly altered local air velocity in both ventilation systems. Depending on the measurement location, differences between occupied and unoccupied conditions reached up to 50% under UDAF ventilation and up to 65% under MV ventilation. The observed changes indicated a redistribution of airflow within the surgical micro-environment rather than a uniform reduction in velocity. Patient sex influenced airflow conditions, particularly under UDAF ventilation at a supply-air temperature of 19 °C. Increasing the supply-air temperature from 19 °C to 26 °C generally reduced air velocity in both systems.