What does pulse oximetry primarily measure?

Pulse oximetry primarily measures the percentage of bound hemoglobin in the blood. This non-invasive method estimates how much oxygen is being carried by hemoglobin, which is crucial for assessing a patient's respiratory and cardiovascular status. The device shines light through a part of the body, often a fingertip or earlobe, and by analyzing the light absorption, it can determine the proportion of hemoglobin that is saturated with oxygen, as well as that which is not.

This measurement is vital because it indicates how effectively oxygen is being transported in the bloodstream. A high percentage of bound hemoglobin indicates good oxygenation, while a low level can signify hypoxemia or other underlying health issues. Thus, understanding the saturation of hemoglobin is essential for clinical assessments, particularly in patients with respiratory conditions.

In contrast, the other options either refer to the functions or conditions that are not directly measured by pulse oximetry. For instance, while lung function and tissue oxygen levels are related to oxygen delivery, they are assessed through different methods or clinical evaluations.