Patients were recruited from 3 ICUs at Virginia Commonwealth University Medical Center,
a large urban hospital. All patients older than 18 years (n = 10 913) in medical, surgical/
trauma, and neuroscience ICUs were screened for inclusion. The Figure provides
information about screening, enrollment, and attrition. Patients were randomized to
treatment within each ICU according to a permuted block design developed by the
biostatistician (D.K.M.) before the start of the study. Patients receiving mechanical
ventilation were enrolled within 24 hours of intubation. Because reintubation increases the
risk for VAP,23,24 patients who had had a previous endotracheal intubation during the
current hospital admission were excluded. Edentulous patients were excluded because dental
plaque could not be assessed. Patients with a clinical diagnosis of pneumonia at the time of
intubation were excluded because determination of nosocomial pneumonia is confounded in
patients with preexisting pneumonia. Consent was obtained for 547 patients.
Patients remained in the study for a maximum of 7 days unless extubated; for patients
extubated before day 7, participation in the study ended on the day of extubation. This step
was necessary because VAP was scored by using the CPIS, and variables necessary for
computation of the CPIS (eg, number of times endotracheal suctioning was performed,
ventilator settings, endotracheal tube cultures) were not available after extubation. The
primary outcome of the study was the CPIS on day 3. On day 3, the analysis sample
consisted of 192 patients, 116 patients remained in the analysis sample on day 5, and 76
patients were analyzed on day 7.