Compliance (hollow organs)
Principle
Elastance is a measure of the tendency of a
hollow organ to recoil toward its original dimensions upon removal of a
distending or compressing force. It is the reciprocal of compliance.
Compliance of a hollow organ is calculated using the
following equation:
C =
ΔV/ΔP,
where ΔV is the change in volume, and ΔP is the
change in pressure. In SI-units, its dimension is L/Pa.
It should not be mixed up with the one-dimensional compliance,
or better the reciprocal, i.e. modulus of elasticity as defined in the theory
of strength of materials, see Elasticity
and Hooke's law, Elasticity 1: elastic or Young’s modulus and Tensile strength.
Application
Cardiovascular
system
The terms elastance and
compliance are of particular significance in cardiovascular physiology.
Specifically, the tendency of the arteries and veins to stretch in response to
pressure has a large effect on perfusion and blood pressure.
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. An extreme
application is the use of pressure trousers or suites by astronauts.
Compliance of the lungs is an important measurement in
pulmology. Fibrosis is associated with a decrease in pulmonary
compliance. Emphysema is associated with an increase in pulmonary
compliance.
More Info
For the cardiovascular system, see Elasticity
of the aorta, Blood pressure: models
and Windkessel model.
For the lungs,
see Lung gas transport 2, pressure, volume and flow and Lung gas
transport 2, resistance and compliance.