Adult Critical Care Specialty (ACCS) Practice Exam

What is indicated by a Ca-Vo2 difference of 8.2 vol%?

1. Normal cardiac output

2. Severe tissue hypoxia

3. Reduced oxygen utilization

4. Normal venous saturation

The correct answer is: Severe tissue hypoxia

A Ca-Vo2 difference of 8.2 vol% indicates the amount of oxygen that is extracted by the tissues from the blood as it circulates through the body. In general, a Ca-Vo2 difference reflects how effectively oxygen is being utilized by the tissues. In a healthy physiological state, the normal range for the Ca-Vo2 difference is typically between 4-6 vol%. When the difference exceeds this range, as in the case of 8.2 vol%, it may suggest that tissues are extracting more oxygen than usual due to inadequate delivery or supply of oxygen. This condition often arises in situations of severe tissue hypoxia, where the body's tissues are not receiving enough oxygen to meet their metabolic demands. Thus, a Ca-Vo2 difference of 8.2 vol% signals that there may be severe tissue hypoxia, as the body is trying to extract as much oxygen as possible from the available blood supply due to limited oxygen delivery or saturation.