Influence of intermittent subglottic lavage on subglottic colonisation and ventilator-associated pneumonia

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Abstract
Objective: In order to prevent ventilator-associated pneumonia (VAP), we investigated whether the subglottic space, as a crucial pathogen reservoir and key area of infection, can be decontaminated by intermittent subglottic lavage using a special endotracheal tube allowing subglottic lavage and aspiration drainage (HI-LO EVAC ® II tube, Mallinckrodt Medical Inc, St Louis, MO, USA). Design: Prospective, randomised clinical trial. Setting: Intensive care unit at a university hospital. Subjects: Thirty-nine critically ill patients were prospectively randomised into three study groups. Interventions: In the subglottic lavage group, the subglottic space was flushed with 20 ml isotonic saline in three-hour intervals. In the pharyngeal lavage group, an additional oropharyngeal lavage with 500 ml n-saline was performed once daily. The control group received a daily diagnostic lavage of only 2 ml n-saline. Measurements and main results: In the lavage groups, bacterial growth in the lavage fluids was qualitatively and quantitatively determined before each subglottic lavage, as well as before and following the high-volume pharyngeal lavage procedures. With respect to changes in bacteria counts which were averaged over 24-hour periods, there were no significant differences in the corresponding median values between the three groups. Between subsequent lavage procedures, increasing as well as decreasing bacteria counts occurred in all groups. As far as the median values of changes in bacteria counts were concerned, which were around zero, the highest range of extreme values was found in the pharyngeal lavage group, whereas the control group showed the lowest variation. The pharyngeal lavage, taken by itself, caused a significant decrease in subglottic bacteria counts. However, in the interval between subsequent lavage procedures bacterial counts had returned to baseline levels. With respect to VAP, there was no statistically significant difference between the groups. In the control group, pneumonia tended to occur one day later. With respect to the origin of pathogens causing nosocomial pneumonia, bacteria of the oropharyngeal flora were found twice as often as bacteria of the intestinal flora. Conclusions: There was no significant effect of intermittent subglottic lavage on subglottic bacterial growth, or on the incidence of VAP. Depending on the lavage intensity, there was presumably an increasing mobilisation of the pharyngeal flora, which favoured a recolonisation of the subglottic space.

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