Final answer:
Supplemental oxygen would be required when the oxygen saturation falls below the normal range of 95-100 percent.
Step-by-step explanation:
Oxygen saturation is normally monitored using a device called a pulse oximeter, which measures the percentage of hemoglobin sites occupied by oxygen in a patient's blood. Normal pulse oximeter readings range from 95-100 percent. Supplemental oxygen may be required when the oxygen saturation falls below this range, indicating hypoxemia or low blood oxygen levels.