Parameters:
(1) number of days in the ICU
(2) number of days on the mechanical ventilator
(3) number of day with an indwelling urinary catheter
(4) number of days with a central venous catheter or other central line
device utilization ratio =
= ((days on mechanical ventilation) + (days with a urinary catheter) + (days with a central line)) / (number of days in the ICU)
Interpretation:
• minimum ratio: 0
• maximum ratio: 3 (= number of devices being monitored)
• The higher the ratio the greater the risk of a nosocomial infection related to one of the monitored devices.
Since the number of devices associated with nosocomial infections are increasing, the number of devices monitored could be increased beyond the initial 3.
One modification is to measure the number of days prior to the onset of a nosocomial infection (de Irala-Estevez et al). For example, if the person is in the ICU for 14 days but has a nosocomial infection diagnosed on day 10, then the denominator becomes 10 and the device usage is measured only for the first 10 days of the ICU stay.
