Pulse pressure

Pulse pressure is the difference between systolic and diastolic blood pressure. Pulse pressure is the difference between systolic and diastolic blood pressure. It is measured in millimeters of mercury (mmHg). It represents the force that the heart generates each time it contracts. Resting blood pressure is normally approximately 120/80 mmHg, which yields a pulse pressure of approximately 40 mmHg. Pulse pressure is the (higher) systolic blood pressure minus the (lower) diastolic blood pressure. The systemic pulse pressure is approximately proportional to stroke volume, or the amount of blood ejected from the left ventricle during systole (pump action) and inversely proportional to the compliance (similar to Elasticity) of the aorta. The aorta has the highest compliance in the arterial system due in part to a relatively greater proportion of elastin fibers versus smooth muscle and collagen. This serves the important function of damping the pulsatile (max pump pressure) output of the left ventricle, thereby reducing the initial systolic pulse pressure but slightly raising the subsequent diastolic phase (a period rather similar to Dwell time). If the aorta becomes rigid because of disorders such as arteriosclerosis or atherosclerosis, the pulse pressure would be very high because the aorta becomes less compliant due to the formation of rigid lesions to the (otherwise flexible) aorta wall. A pulse pressure is considered abnormally low if it is less than 25% of the systolic value. The most common cause of a low (narrow) pulse pressure is a drop in left ventricular stroke volume.In trauma, a low or narrow pulse pressure suggests significant blood loss (insufficient preload leading to reduced cardiac output). If the pulse pressure is extremely low, i.e. 25 mmHg or less, the cause may be low stroke volume, as in Congestive Heart Failure and/or cardiogenic shock. A narrow pulse pressure is also caused by aortic valve stenosis and cardiac tamponade. Usually, the resting pulse pressure in healthy adults, sitting position, is about 30–40 mmHg. The pulse pressure increases with exercise due to increased stroke volume, healthy values being up to pulse pressures of about 100 mmHg, simultaneously as total peripheral resistance drops during exercise. In healthy individuals the pulse pressure will typically return to normal within about 11 minutes.