Cardiac output, one of the aspects of blood pressure, specifically refers to the diameter of the blood vessels.

Cardiac Output

The amount of blood pumped by the heart. One of the two major variables that determine blood pressure. Cardiac output is itself determined by two other variables: the rate at which the heart beats (commonly measured in beats per minute) and the amount of blood ejected from the heart (stroke volume). See also total peripheral resistance.

Blood Pressure

The force of circulating blood on the walls of blood vessels, often measured as an indicator of cardiovascular health.