Compliance

Overview
  • Compliance is a generic term referring to the relationship between the volume of an inflatable object and the transmural pressure required to achieve that volume of inflation. Compliance can be used to describe the volume-pressure relationship of several inflatable organs and tissues thus justifying its classification as a basic concept.
Derivation
  • Compliance = (Volume in object)/(Transmural Pressure)
Thought Experiment
  • Consider two balloons one of which is very thick and the other very thin. A hand pump is used to fill each of them with 1 liter of water. Because the thick balloon will require large pressures to fill it with 1 liter of water, it is considered to have a very low compliance. Because the thin balloon can be filled with 1 liter of water even at low pressures, it is considered to have a high compliance. Therefore, the more compliant an object is, the less pressure is required to fill it with larger volumes of fluid. Alternatively, the less compliant an object is, greater pressures are required to fill it with smaller volumes of fluid.