American Association of Critical-Care Nurses (AACN) Certification Practice Test

How is systemic vascular resistance (SVR) related to blood vessels?

1. It determines the volume of the blood

2. It indicates the frequency of heart contractions

3. It indicates the dilation or constriction of blood vessels

4. It reflects the oxygenation levels in the blood

The correct answer is: It indicates the dilation or constriction of blood vessels

Systemic vascular resistance (SVR) is a critical concept in cardiovascular physiology, directly related to the condition of blood vessels. It represents the resistance that the blood encounters as it flows through the systemic circulation, primarily influenced by the diameter of the blood vessels. When blood vessels constrict, their diameter decreases, leading to increased resistance and thus higher SVR. Conversely, when blood vessels dilate, their diameter increases, resulting in decreased resistance and lower SVR. This relationship between SVR and the dilatation or constriction of blood vessels is crucial for understanding how the body regulates blood flow and blood pressure. It helps to control the distribution of blood to various tissues based on metabolic needs, ensuring that areas requiring more oxygen and nutrients receive adequate blood supply. In contrast, the other options do not accurately capture the essence of what SVR indicates. Blood volume pertains to the total amount of blood in the circulatory system, heart contraction frequency relates to heart rate not resistance, and oxygenation levels depend on factors like respiratory function rather than directly correlating with vascular resistance. Thus, the assertion that SVR indicates the dilation or constriction of blood vessels is indeed the most accurate and informative connection.