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The purpose of this prospective randomized study is the analysis of bacterial
colonization in ventilator circuits related to their characteristics and
changing interval to determine the role of ventilator circuits in prevention
of ventilator associated pneumonia (VAP) and to confirm the results of other
studies of a decreasing risk of VAP at increasing ventilator circuit interval
on a view of microbiologist. In a 12-bed surgical intensive care unit (SICU)
of a 1100-bed primary care university hospital 62 patients requiring
mechanical ventilation for more than 48 hours were enrolled in the study.
Quality and quantity of bacterial colonization was determined at three locations of
the ventilator-circuit. The bacterial colonization was compared in standard
nonheated circuits (Circuit A) versus heated wire circuits (Circuit B)
at two different ventilator circuit changing intervals.
The results were related to the microbiological findings in the patient
(stomach, oro-pharyngeale cavity, trachea) and to the development of
pneumonia. The trend was clear: the longer the circuit changeout time,
the lower the colonization with endogenous and exogenous microorganisms.
Mainly endogenous pathogens were identified in ventilator circuits, that were
microorganisms having been found in patient at first (endogenous contamination).
The patients themselves were the main sources of the bacterial
microorganism colonizing the circuit. In Circuit A, a system
with more need of intervention and formation of potentially contaminated
condensate, a higher rate of bacterial contamination was identified than
in circuit B. In comparison circuit A versus circuit B we found significant
differences (p < 0,05) in exogenous microbial colonization.
The endogenous contamination extremely depends on the ventilation mode.
In controlled ventilation mode the rate of circuit-contamination is significant
lower than in ventilation mode with high possibility of self-breathing.
Decreased manipulation of ventilator circuit by extending changing interval or
using circuits with less need of intervention led to a significant lower rate
of bacterial colonization and, published by other authors, to lower risk of VAP.
But a relationship between the quality and quantity of colonization and
the development of pneumonia could not to be proved.
The circuit change interval should be prolonged at least 7 day and ventilator
circuits with minimal need of intervention should be used to decrease the risk