Certified Transport Registered Nurse Certification Practice Exam

SpO2 (O2 saturation) measures the saturation of what?

1. Partial pressure of oxygen

2. Carbon dioxide binding sites

3. Oxygen binding sites

4. Carbon monoxide levels

The correct answer is: Oxygen binding sites

The saturation of oxygen in the blood, commonly referred to as SpO2, specifically measures the percentage of hemoglobin binding sites in the red blood cells that are occupied by oxygen molecules. When hemoglobin, the protein responsible for transporting oxygen, binds with oxygen, it forms oxyhemoglobin. This process is critical for ensuring that oxygen is available to the tissues and organs throughout the body, which is vital for maintaining cellular metabolism and overall health. Understanding SpO2 is pivotal in assessing a patient's respiratory status, especially in conditions affecting lung function or oxygenation. When monitoring SpO2, healthcare providers can gauge how well the patient is oxygenating their blood and make decisions regarding interventions, such as supplemental oxygen or other therapeutic measures, based on those readings. The other options relate to different elements of respiratory physiology but do not directly pertain to measuring oxygen saturation. For instance, the partial pressure of oxygen relates to the amount of oxygen dissolved in blood plasma, which is not the same as the saturation indicated by SpO2. Carbon dioxide binding sites and carbon monoxide levels pertain to different gases and their interactions with hemoglobin, which do not influence the specific measurement of oxygen saturation by SpO2. Thus, the correct choice reflects the focus on the