The indicator dilution principle is based on the definition of a concentration. If the amount of the substance is known and the resulting concentration is measured the volume can be calculated.
Body Fluids
Measurement of body fluid volume. Volume amount concentration or more specifically volume amount given amount lost during equilibration concentration b. Marker substances direct measurements and their marker substances. This is estimated by measuring the volume of distribution of isotopes of water. Moissl um1 wabel p chamney pw bosaeus i levin nw bosy westphal a korth o müller mj ellegård l malmros v kaitwatcharachai c kuhlmann mk zhu f fuller nj. If you know plasma volume and hematocrit of blood volume that is made up by cells total blood volume can be calculated. A more recent study estimated joint fluid volume in rabbits by dividing the total calcium concentration in the joint cavity lavage μgjoint by calcium concentration in the plasma μgml4to confirm the relevance of the method radioactivity in the plasma and joint cavity lavage was determined after intravenously injecting 3h2o.
The volume of a fluid compartment in the body can be measured by placing an indicator substance in the compartment allowing it to disperse evenly through out the compartments fluid and then analyzing the extent to which the substance becomes diluted. Tritium oxide tho is used because it is a weak beta emitter making it easy to measure in a liquid scintillation counter. Tbw is strongly related to fat free mass ffm which contains in healthy individuals an average of 732 of water. The measurement of body fluid volumes extracellular water ecw intracellular one icw and their sum total body water tbw is important in many pathologies. Body fluid volume determination via body composition spectroscopy in health and disease. This is the volume of that body fluid compartment eg volume of distribution of d20 is volume of tbw etc.
It is measured by holding the patients hand at heart level and pressing on the pad of their middle finger for five seconds. 100 38 5645 ml. Total body water 30 012 ml d2o x 0001 ml d2oml water 29880 ml or 30 l therefore total body water as a percentage of body weight equals 50 in this woman. 222 total body water. Based upon the calcium ratio technique joint fluid volumes ranged from a mean 401 μljoint in normal rabbits to 680 μljoint in arthritic rabbits. To measure extracellular water volume the ideal indicator should distribute rapidly and uniformly outside the cells and should not enter the cell compartment.
Figure 254 shows this indicator dilution method of meas uring the volume of a fluid compartment which is based on the principle of conservation of mass. The pressure is released and the time measured in seconds until normal colour returns. 3500 x 100. Rapid mixing of tritiated water throughout all compartments occurs during a 3 to 4 hour equilibration period. Volume it was dissolved in. Capillary refill time crt is a good measure of the fluid present in the intravascular fluid volume large 2005.
Body fluid compartments can be measured by dilution of a compound that distributes only in the space of interest.
Gallery of Measurement Of Body Fluid Volume
