Blood or arterial pressure allows us to measure the strength of pressure exerted on the blood by the walls of arteries. Using an inflatable arm cuff, blood pressure is measured in two values. Systolic blood pressure corresponds to the higher value, obtained during the systole phase of the heart, or the phase where the heart ejects the blood, while diastolic pressure corresponds to the lower value given when the heart releases. These measurements are calculated in millimeters of mercury. Average blood pressure is defined as that which would be needed to perform the same strength of circulation if the value did not fluctuate. It does not constitute an average of the two values, but is the result of a more complex calculation, and is scarcely used in practice.