As I began my assessment to end my shift for the day, I noticed my patient’s oxygen level decreasing. I checked to make sure that the oxygen probe remained secure on the patient’s foot and began taking vital signs. I checked the patient’s trach placement and suctioned to make sure there were no mucus plugs blocking the patient’s airway. While listening to lung sounds, I noticed crackles in the RLL (right lower lobe). I immediately notified the patient’s physician. The physician instructed me to increase the oxygen level from 1L to 1 ½ L; which did not help because the patient’s oxygen saturation remained at 80%. The physician requested that the oxygen level be increased to 2 L, and at that time the patient