III. Ventilation of Operating Rooms—Bacteriological Investigations

Abstract

Airborne bacteria in surgical operating rooms were studied during operations, using a slit-sampler and sedimentation plates. When particles contaminated with Staphylococcus aureus reached concentrations of 1 - 2 per cubic foot and settled at 0.5 per square foot per minute, wound sepsis after the operations was common. Counts of 0.02/cu. ft. and 0.005/sq. ft./min. respectively were associated with less sepsis, but it is not yet possible to define safety limits for the bacterial content of air in operating rooms. Contamination is much reduced by preventing excessive staff activity during operations and by pressure ventilation to prevent air reaching the operating area from other parts of the hospital. Experiments in a dummy operating room showed that uniform contamination or localized contamination at low levels are best removed by downward displacement ventilation systems; and localized contamination at high level, by a turbulent system. Choice of ventilation methods for operating rooms now depend on experiments to show if S. aureus is scattered mainly from sources and reservoirs above or below the operating table.