A patient receiving 35% O₂ through an air-entrainment mask set at 6 L/min input flow becomes tachypneic. Simultaneously, you notice that the SpO₂ has fallen from 91% to 87%. Which of the following actions would be most appropriate in this situation?
a. Switch the patient to a 40% air-entrainment mask.
b. Increase the device's input flow to 10 L/min.
c. Switch the patient to a 28% air-entrainment mask.
d. Decrease the device's input flow to 4 L/min.