Oxygen saturation (SaO2) refers to what?

Oxygen saturation (SaO2) specifically refers to the percentage of hemoglobin binding sites that are occupied by oxygen. This measurement is crucial because it indicates how effectively oxygen is being transported in the blood to meet the body's metabolic needs. Hemoglobin, a protein found in red blood cells, carries oxygen from the lungs to the tissues and helps in returning carbon dioxide from the tissues back to the lungs for exhalation.

Understanding this concept is important for evaluating a patient's respiratory function and overall oxygenation status. A normal oxygen saturation level typically ranges from 95% to 100%, and levels below this may indicate hypoxemia, or insufficient oxygen in the blood, which requires prompt attention and intervention.

The other choices do not accurately represent the concept of oxygen saturation. For instance, the percentage of hemoglobin saturation with carbon dioxide does not pertain to oxygen saturation but rather to carbon dioxide transport in the blood. The amount of oxygen in blood plasma and the proportion of oxygen entering the lungs represent different aspects of respiratory physiology that are not captured by the term oxygen saturation.