Evaluations of a Patient Isolator System

Abstract

Levels of surface and airborne microbial contamination within a unitized patient isolator system were monitored during a 12-day period of occupancy. Essentially all of the bacterial isolates recovered from the interior of the isolator during this period were equated with organisms of documented patient origin. The majority of microorganisms isolated as surface contaminants within the isolator were of fecal origin; organisms from the upper respiratory tract appeared to be of minor importance as surface contaminants. The most significant finding was the absence within the isolator of pathogenic microbes other than those introduced by the patient. The effectiveness of the microbial barrier provided by the isolator system was further demonstrated in studies of the aero-microflora within the enclosure. These revealed the complete absence from the internal air volume of such normal airborne contaminants as fungi, yeast, or soil bacteria. However, progressive increases in the recovery rates of airborne bacteria during the period of occupancy suggested certain inadequacies in the air supply system as employed in this study. These were attributed to a reduction in efficiency in the air ventilation system brought about by the combined, and redundant, use of separate ultra-high efficiency filter units for filtration of both the intake and exhaust air streams. This was subsequently verified in a later clinical application of the isolator in which filtration of only intake air resulted in a 20- to 40-fold increase on ventilation efficiency.