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.