Which of the following would suggest that a patient is ready to be weaned from a ventilator?

a. Vital capacity (VC) of 8 mL/kg ideal body weight (IBW)
b. PaO2 or 65 mm Hg on and FIO2 of 0.6
c. Dead space-to-tidal volume ratio (VD/VT) of 0.75
d. Rapid shallow breathing index of 75 breaths/min/L

ANS: D
The RSBI is the most frequently studied and one of the more reliable tests for determining a pa-tient's weaning status. It is calculated by dividing the respiratory frequency (in breaths/min) by the VT (in L): f/VT. This measurement is taken 1 minute after disconnecting the spontaneously breathing patient from the ventilator and oxygen. Successful weaning is more likely if the RSBI is less than 105 (normal range, 60-105). Values above 105 suggest that a patient is not ready for weaning and probably will fail a weaning trial.