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Venous return (VR) is the flow of blood back to the heart. Under steady-state conditions, venous return must equal cardiac output (Q), when averaged over time because the cardiovascular system is essentially a closed loop. Otherwise, blood would accumulate in either the systemic or pulmonary circulations.
This value is inversely related to the total cross-sectional area of the blood vessel and also differs per cross-section, because in normal condition the blood flow has laminar characteristics. For this reason, the blood flow velocity is the fastest in the middle of the vessel and slowest at the vessel wall.
The Fick principle states that blood flow to an organ can be calculated using a marker substance if the following information is known: Amount of marker substance taken up by the organ per unit time; Concentration of marker substance in arterial blood supplying the organ; Concentration of marker substance in venous blood leaving the organ
An ejection fraction (EF) is the volumetric fraction (or portion of the total) of fluid (usually blood) ejected from a chamber (usually the heart) with each contraction (or heartbeat). It can refer to the cardiac atrium , [ 1 ] ventricle , [ 2 ] gall bladder, [ 3 ] or leg veins, [ 4 ] although if unspecified it usually refers to the left ...
It can also be considered as the ‘load’ that the heart must eject blood against. Afterload is, therefore, a consequence of aortic large vessel compliance, wave reflection, and small vessel resistance (LV afterload) or similar pulmonary artery parameters (RV afterload). Left ventricular afterload is affected by various disease conditions.
Major factors influencing cardiac output – heart rate and stroke volume, both of which are variable. [1]In cardiac physiology, cardiac output (CO), also known as heart output and often denoted by the symbols , ˙, or ˙, [2] is the volumetric flow rate of the heart's pumping output: that is, the volume of blood being pumped by a single ventricle of the heart, per unit time (usually measured ...
Using the fact that each gram of hemoglobin can carry 1.34 mL of O2, the oxygen content of the blood (either arterial or venous) can be estimated by the following formula: = [] ( /) + PO2 is the partial pressure of oxygen and reflects the amount of oxygen gas dissolved in the blood. The term 0.0032 * P02 in the equation is very small and ...
Perfusion is measured as the rate at which blood is delivered to tissue, [2] or volume of blood per unit time (blood flow) per unit tissue mass. The SI unit is m 3 /(s·kg) [ citation needed ] , although for human organs perfusion is typically reported in ml/min/g. [ 3 ]