These definitions should provide a general understanding of the material presented here, and should not be considered as a substitute for detailed study of a medical text.
Aortic Regurgitation: Characterised by the presence of a reflux of blood (backflow) from the aorta into the left ventricle during diastole (i.e. while the heart is relaxing between beats). This often occurs when the aortic valve does not open or close correctly.
Arterial Compliance: An index that describes the stiffness of the arterial wall. Compliance is affected by numerous factors, such as age and hypertension. Therefore, determination of this parameter may facilitate diagnosis of hypertension.
Bernoulli Effect: High velocity flow produces an additional force pulling the wall inward, into the flow stream. This physical phenomenon is used by Pulse Dynamics to measure blood pressure.
Brachial Artery: The artery that runs down the inside of the upper arm. Blood pressure is usually measured from the brachial artery.
Correlation Coefficient: An index to compare two sets of measurements. A coefficient of 1.0 corresponds to identical sets of measurements. A coefficient of 0.75 or greater is considered a good correlation, while a coefficient of 0.90 or greater is considered excellent in a physiological system.
Diastolic Blood Pressure (DBP): The lowest blood pressure in the artery. Occurs when the heart is in diastole (i.e. relaxing between beats).
Direct Measurement: Direct measurement is the gold standard for blood pressure measurement. These measurements are taken by the surgical insertion of a catheter into the patient. Also known as "invasive" measurements.
Korotkoff Sounds: The sounds that occur in the artery as an inflatable cuff deflates from systolic through diastolic pressures. There are five different sounds, or phases. The appearance of Phase I sounds corresponds to systolic pressure. Diastolic pressure occurs during either Phase IV or Phase V. There is still some debate as to which phase most correctly measures diastolic pressure. Korotkoff sounds are thought to be caused by changes in blood flow through the artery during the measurement process.
Left Ventricular Contractility (dP/dt LV): An indicator of the strength of contraction of the heart.
Mean Arterial Blood Pressure: The "average" blood pressure in the artery from systole through diastole. It may be estimated approximately by the equation MAP = SBP/3 + 2DBP/3. Physically, it is the point in the cardiac cycle where there is no deformation of the arterial wall due to blood pressure or flow.
Non-Invasive Measurement: Also known as "indirect" measurements. These measurements are conducted without surgery, and are performed on an out-patient basis. These measurements are more common than invasive measurements for measuring blood pressure because of patient safety, comfort, and cost. Examples are auscultatory and oscillometric measurements.
Peripheral Resistance: The heart must exert effort to pump blood through the circulation. Peripheral resistance is a measure of the resistance that must be overcome by the heart in order to pump blood.
Systolic Blood Pressure (SBP): The highest blood pressure experienced by the artery. Occurs while the heart is in systole (i.e. contracting to pump blood).
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