The outcome variable was defined as the occurrence
of VAP. Development of VAP was quantified
by using the Clinical Pulmonary Infection Score (CPIS)
and confirmed by using the alternative pneumonia
clinical criteria for infants and children defined by the
Centers for Disease Control and Prevention and the
National Healthcare Safety Network (CDC/NHSN).
The CPIS is a clinical score of 0 to 12 based on the
following 6 variables: temperature, blood leukocyte
count, tracheal secretions, radiological pulmonary
imaging, oxygenation, and microbiological data.
Scores of 6 or greater are considered indicative of
VAP.7 The CDC/NHSN diagnosis is based on serial
chest radiographs, changes in body temperature,
blood leukocyte count, oxygenation, lung auscultation,
and characteristics of the pulmonary secretions.8
A physician determined these scores. When
the CPIS and the CDC/NHSN scores did not agree,
a second expert analyzed the data to determine the
final diagnosis. Each episode of VAP was characterized
as early or late onset. Early-onset VAP occurs
during the first 4 days of mechanical ventilation
and late-onset VAP develops 5 or more days after
initiation of mechanical ventilation