Which of the following factors will decrease the FiO2 delivered by a low-flow O2 system? 1. Short inspiratory time 2. Fast rate of breathing 3. Lower O2 input 4. Large minute ventilation

a. 2 and 4 only
b. 1, 2, and 3 only
c. 3 and 4 only
d. 1, 2, 3, and 4

ANS: D
The amount of air dilution depends on several patient and equipment variables. Table 41-4 sum-marizes these key variables and how they affect the FiO2 provided by low-flow systems