Does the specific time of day used to capture data on ventilator-days have an impact on the documented rates of ventilator-associated pneumonia?

Definitions of ventilator-associated pneumonia do not note a preferred daily time for obtaining denominator data. We examined collecting data on the number of ventilator-days at different times of day in 7 intensive care units. Rates of ventilator-associated pneumonia did not significantly differ when denominator data were collected at midnight, 8 am, or 4 pm, supporting standard definitions.