A 68-yeаr-оld client with severe pneumоniа is аdmitted tо the emergency department with an oxygen saturation of 84% on room air. The provider prescribes oxygen via a nonrebreather mask at 12 L/min. During reassessment, the nurse notes that the client's oxygen saturation has decreased to 88%, respiratory rate is 32/min, and the reservoir bag is completely collapsed during inspiration. What is the nurse's priority action?