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Pressure-Volume loops showing end-systolic pressure volume relationship. End-systolic pressure volume relationship (ESPVR) describes the maximal pressure that can be developed by the ventricle at any given LV volume. This implies that the PV loop cannot cross over the line defining ESPVR for any given contractile state.
Flow-Volume loop showing successful FVC maneuver. Positive values represent expiration, negative values represent inspiration. At the start of the test both flow and volume are equal to zero (representing the volume in the spirometer rather than the lung). The trace moves clockwise for expiration followed by inspiration.
Ventricular volume; Electrocardiogram; Arterial flow (optional) Heart sounds (optional) The Wiggers diagram clearly illustrates the coordinated variation of these values as the heart beats, assisting one in understanding the entire cardiac cycle. [1]
Very useful information can be derived by examination and analysis of individual loops or series of loops, for example: the horizontal distance between the top-left corner and the bottom-right corner of each loop is the stroke volume [5] the line joining the top-left corner of several loops is the contractile or inotropic state. [6]
The programmed delay at the AV node also provides time for blood volume to flow through the atria and fill the ventricular chambers—just before the return of the systole (contractions), ejecting the new blood volume and completing the cardiac cycle. [8] (See Wiggers diagram: "Ventricular volume" tracing (red), at "Systole" panel.)
Since then it has been extensively used by many researchers to solve different kinds of fluid flow and heat transfer problems. [1] Many popular books on computational fluid dynamics discuss the SIMPLE algorithm in detail. [2] [3] A modified variant is the SIMPLER algorithm (SIMPLE Revised), that was introduced by Patankar in 1979. [4]
Dimensionless numbers (or characteristic numbers) have an important role in analyzing the behavior of fluids and their flow as well as in other transport phenomena. [1] They include the Reynolds and the Mach numbers, which describe as ratios the relative magnitude of fluid and physical system characteristics, such as density, viscosity, speed of sound, and flow speed.
In most contexts a mention of rate of fluid flow is likely to refer to the volumetric rate. In hydrometry, the volumetric flow rate is known as discharge. Volumetric flow rate should not be confused with volumetric flux, as defined by Darcy's law and represented by the symbol q, with units of m 3 /(m 2 ·s), that is, m·s −1.