Compliance (physiology)

Compliance is a measure of the tendency of a hollow organ to resist recoil toward its original dimensions upon removal of a distending or compressing force. It is the reciprocal of "elastance".

Blood vessels
The terms elastance and compliance are of particular significance in cardiovascular physiology and respiratory physiology. An increase in blood volume occurs in a vessel when the pressure in that vessel is increased. The tendency of the arteries and veins to stretch in response to pressure has a large effect on perfusion and blood pressure. Venous compliance is 20-24 times larger than arterial compliance. Compliance is calculated using the following equation, where ΔV is the change in volume, and ΔP is the change in pressure:
 * $$C = \frac{ \Delta V}{ \Delta P} $$

Physiologic compliance is generally in agreement with the above and adds dP/dt as a common academic physiologic measurement of both pulmonary and cardiac tissues. Mathematical adaptation of utility formulas once best applied to rubber and latex now allow measurement of complex and dynamic physiologic states, specifically addressed here in pulmonary and cardiac tissue compliance.

Vulcanization of natural rubber occurs when elements such as sulfur are introduced to the media. In industry, sulfur or similar additions are titrated to the desired compliance performance definition of the media. The Myocardium is decidedly not made of rubber but certainly shares many characteristics regarding infiltration by other agents. Introduction of Calcium within myocardial mass is a similar process that detracts from compliance and heralds Diastolic Dysfunction. Current proponents of restoration of Ventricular Dyssynchrony purport that cardiac dP/dt curves can be reversed, thus demonstrating clinical improvement. One could then assume that inexpensive echocardiographically defined reversal of derived E:A time intervals of flow across the mitral valve would follow these curves in support of the theory espoused. Veins have a much higher compliance than arteries (largely due to their thinner walls.) Veins which are abnormally compliant can be associated with edema. Pressure stockings are sometimes used to externally reduce compliance, and thus keep blood from pooling in the legs.