Advanced Patient Assessment Practice Exam

What is the best indicator of arterial oxygenation?

1. SaO2

2. P(A-a)O2

3. PaO2

4. CaO2

The correct answer is: CaO2

The most accurate indicator of arterial oxygenation is the arterial oxygen content, often referred to as CaO2. CaO2 takes into account both the oxygen dissolved in plasma (PaO2) and the oxygen bound to hemoglobin. It is calculated using the hemoglobin concentration, the saturation of hemoglobin with oxygen (SaO2), and the partial pressure of oxygen (PaO2). In clinical practice, assessing CaO2 provides a comprehensive understanding of a patient's ability to transport oxygen to tissues, making it essential for evaluating their oxygenation status. This includes considerations of both the efficiency of gas exchange in the lungs and the capacity of the blood to carry oxygen. While SaO2 and PaO2 are both important parameters in determining oxygenation, they only focus on specific aspects of oxygen transport. SaO2 indicates the percentage of hemoglobin saturated with oxygen, while PaO2 measures the partial pressure of oxygen dissolved in the blood. P(A-a)O2, which assesses the difference between alveolar and arterial oxygen levels, is useful for evaluating gas exchange efficiency but does not directly indicate how much oxygen is carried in the blood itself. By understanding the complete picture presented by CaO2, healthcare professionals can better assess and manage patients