Surgical area contamination - comparable bacterial counts using disposablehead and mask and helmet aspirator system, but dramatic increase upon omission of head-gear: an experimental study in horizontal laminar airflow

The effect of different head coverings on air-borne transmission of bacteri a and particles in the surgical area was studied during 30 strictly standar dized sham operations performed in a horizontal laminar air flow (LAF) unit . The operating team members wore disposable gowns plus either a non-steril e head covering consisting of a squire type disposable hood and triple lami nar face mask, a sterilized helmet aspirator system or no head cover at all . In the wound area both types of head cover resulted in low and comparable a il (means of 8 and 4 cfu/m(3)) and surface contamination (means of 69 and 1 26 cfu/m(2)/h) rates. Omission of head-gear resulted in a three- to five-fo ld increase (P<0.01-P<0.001), depending on site sampled air contamination r ate (mean of 22 cfu/m3) whereas the bacterial sedimentation rate in the wou nd area increased about 60-fold (P< 0.0001). A proper head cover minimized the emission of apparently heavy particles that were not removed by the hor izontal LAF and contained mainly streptococci, presumably of respiratory tr act origin. Dust particle counts revealed no differences between the three experimental situations. No correlation between air and surface contaminati on rates or between air contamination and air particle counts was found. We conclude that, from a bacteriological point of view, disposable hoods of squire type and face masks are equally as efficient as a helmet aspirator system and both will efficiently contain the substantial emission of bacter ia-carrying droplets from the respiratory tract occurring when head cover i s omitted. Finally, the use of bacterial air counts to assess surgical site surface contamination in horizontal LAF units must be seriously questioned . (C) 2001 The Hospital Infection Society.