What principle is primarily used in the operation of an oximeter?

The operation of an oximeter primarily relies on the principle of reflectance or transmission of light to measure blood oxygen levels. An oximeter typically uses light-emitting diodes (LEDs) that emit specific wavelengths of light—usually red and infrared—through a translucent area of the body, such as a fingertip or earlobe.

As the light passes through the tissues, the device measures the amount of light absorbed by the blood. Oxygenated hemoglobin absorbs light differently than deoxygenated hemoglobin. By analyzing the ratio of absorbed light at these wavelengths, the oximeter can accurately calculate the percentage of hemoglobin that is saturated with oxygen, providing a non-invasive means of assessing a patient’s oxygenation status.

The other options are associated with different medical technologies and do not pertain to the functioning of an oximeter. Ultrasound-based measurements are primarily used for imaging and monitoring soft tissues, electrocardiographic monitoring tracks heart rhythms and functions, and magnetic resonance imaging provides detailed images of organs and structures. None of these modalities utilize the light absorption principles that are essential to how oximeters work.