What is Blood Pressure?
The systolic pressure is the maximum pressure on the arteries during left ventricular contraction (systole) (OER #1). The left ventricle is a lower chamber of the heart responsible for pumping blood out to the body. The diastolic pressure is the resting pressure on the arteries between each cardiac contraction (OER #1) when the heart’s chambers are filling with blood (diastole).
Stroke volume is the amount of blood ejected from the left ventricle in a single contraction. Stroke volume provides information about the functioning of the heart. Stroke volume is influenced by age and typically ranges from 5–80 mL. Newborns have a stroke volume of about 5 mL per contraction while adults have a stroke volume of about 30–70 mL per contraction; the stroke volume increases as individuals grow and their hearts become stronger and can pump more volume per contraction.
Direct measurement of stroke volume involves an invasive approach in which a catheter is passed into the pulmonary artery via a large neck vein; this monitoring device is only used during critical care situations.
Indirect measurement of stroke volume involves assessing the pulse pressure, which is the difference between the systolic and diastolic values and signifies the force required by the heart each time it contracts. For example, if someone’s blood pressure is 120/80 mm Hg, the pulse pressure is 40 mm Hg.
A higher pulse pressure can indicate arterial stiffness, which often happens as a result of aging or cardiovascular disease. A higher pulse pressure can also be indicative of aortic valvular insufficiency where the diastolic pressure is unusually low and the systolic pressure is mildly elevated or unchanged. A lower pulse pressure can be a marker of poor heart function, where cardiac output is decreased.
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