Which of the following does a pulse oximeter NOT measure?

• A. The level of oxygen in the blood
• B. The level of hydration of the animal's tissues
• C. The animal's platelet functions
• D. The tidal volume of the animal

Answer: (B)

A pulse oximeter estimates how much of the hemoglobin in arterial blood is carrying oxygen (oxygen saturation) and it also gives a pulse rate. It does this by using light absorption through a small tissue site and tracking the pulsatile blood flow. It does not assess hydration status, platelet function, or tidal volume. Hydration involves fluid balance and tissue perfusion over time, which isn’t measured by this device. Platelet function requires coagulation or platelet-activity tests, and tidal volume requires ventilation measurements like airflow, not oxygen saturation. So the measurement not provided by a pulse oximeter is the level of hydration.