The Certification Study Guide (6th edition) defines the ventilator utilization ratio (VUR) as a device utilization measure used in surveillance to describe the proportion of patient time during which a specific medical device—in this case, mechanical ventilation—is in use. It is calculated by dividing the total number of ventilator days by the total number of patient days for the same location and time period.

Using the first-quarter data provided, the calculation is as follows:

Ventilator Utilization Ratio = Ventilator Days ÷ Patient Days

Ventilator Utilization Ratio = 800 ÷ 1200 = 0.67

This means that ventilators were in use for 67% of all patient days in the ICU during the first quarter. The study guide emphasizes that device utilization ratios are essential for interpreting device-associated infection data, such as VAP rates, because they reflect the level of patient exposure to the device. Higher utilization increases the population at risk and can influence infection rates independently of prevention practices.

The other answer options are incorrect because they do not reflect the correct calculation. A ratio greater than 1.0 (options C and D) would imply more device days than patient days, which is not possible in this context. Option A underestimates utilization and does not match the provided data.

Understanding and correctly calculating utilization ratios is a core CIC exam competency, as these metrics support accurate surveillance, benchmarking, and performance improvement efforts.