What does pulse oximetry primarily measure?

Pulse oximetry is a non-invasive method used to measure the percentage of hemoglobin in the blood that is saturated with oxygen, often referred to as SpO2. This is achieved through a device that emits light wavelengths, which determines how much oxygen is bound to hemoglobin compared to the total amount of hemoglobin present.

Understanding how pulse oximetry works is crucial for monitoring patients with respiratory issues, ensuring that they maintain adequate oxygen levels for proper physiological functioning. This measurement is essential for assessing the effectiveness of oxygen therapy, guiding treatment decisions, and monitoring patients in critical care situations.

The other options do not convey the primary function of pulse oximetry. It does not measure the percentage of oxygen in the ambient air, carbon dioxide levels, or heart rate variability, as these parameters require different sensors and methodologies not related to the function of pulse oximeters.