You Are First on the Scene of a 61-Year-Old Female

You are first on the scene of a 61-year-old female in need of assistance with her respirations.You have a pocket mask with supplemental oxygen.How can you determine that your artificial ventilation is effective?

A) You are assisting respirations at 10 breaths per minute.
B) Patient's pulse returns to normal.
C) You assure oxygen is being delivered at 15 liters per minute.
D) Patient's skin color remains the same.