<prompt> Inulin is used for the measurement of-ECFICFPlasma volumeBlood volume  <response>: Ans. is a i.e., ECF The volume of the various body compartments can be measured by injecting into them an indicator substance marker or dye and estimating its volume of distribution. Measurement of body fluid volumes is done by Dilution method i.e., by knowing the diluted concentration of dye in the fluid. Suppose 5 gm of dye is added to a beaker containing unknown volume of water. After equilibrium, if the marker concentration in water is lg100 ml, the waterin the beaker can calculated as follows : Volume of water Total amount of marker---Concentration of marker in water5g---1g100 ml 500 ml Volume of fluid Total amount of marker injected---Concentration of marker in the fluid, to be measured Most of the fluid are calculated directly by dilution method, except for intracellular fluid ICF and interstitial fluid. Both these are calculated indirectly by calculating other body fluids.ICF Total body water volume - ECF volumeInterstitial fluid ECF volume - Plasma volume Dyes used for various fluid volume measurement are : -Fluid volumeDyeindicator usedTotal body water TBW volumeDeuterium oxide: D2O most commonly used, tritium oxide 3H2O, Aminopyrine, AntipyrineExtracellular fluid ECF volumeInulin most accurate, Sucrose, Mannitol, Sodium thiosulfate, Na22, I125- iothalamatePlasma volume PVEvans Blue T-1824, Serum albumin labeled with radioactive iodineI125Blood cell volumeCr51 labeled RBC 