Using the recorded measurements from a pulmonary artery catheter, how is the systemic vascular resistance calculated?

The calculation of systemic vascular resistance (SVR) is essential for evaluating the afterload that the left ventricle must overcome to eject blood. To derive SVR, the formula incorporates mean arterial pressure (MAP) and central venous pressure (CVP) alongside cardiac output (CO).

The correct answer involves subtracting the CVP from MAP, which accounts for the pressure difference driving blood through the systemic circulation. This difference reflects the force the heart needs to generate to move blood against the resistance in the vascular system. The result is then divided by cardiac output, which provides a measure of how much blood is flowing through the system.

This formula effectively illustrates the relationship between blood flow (cardiac output) and the pressure gradient (MAP minus CVP) that is necessary to overcome the vascular resistance. Therefore, using (MAP - CVP) divided by cardiac output accurately calculates systemic vascular resistance, enabling healthcare professionals to assess vascular tone and potential circulatory issues in patients.