Which option best describes the primary purpose of pulse oximetry?

• A. To monitor heart rate.
• B. To measure blood pressure.
• C. To assess hydration status.
• D. To monitor arterial oxygen saturation continuously.

Answer: (D)

Pulse oximetry is a noninvasive method that continuously monitors the arterial oxygen saturation (SpO2) of hemoglobin in the blood. It works by emitting red and infrared light and measuring how much is absorbed as blood pulses through a fingertip or other site, translating that into a percentage saturation and a pulse rate. The primary use is to track how well oxygen is being carried to the tissues over time and to detect hypoxemia early so oxygen therapy or other interventions can be adjusted. It does not measure blood pressure or hydration status, and while a heart rate reading may be displayed, that is a secondary piece of information rather than the main purpose.