Safety Assessment
There are no special hazards associated with this experiment although protective gloves and safety spectacles should be worn to avoid direct contact of the skin with radioactive material.

To understand the use of a radioactive tracer in the determination of a non-regular volume.

This experiment has been designed to illustrate some of the features and limitations of the single tracer technique for the measurement of blood volume. The dynamics of circulation, gaseous exchange, absorption and excretion are dependent on the rate of flow of blood through tissues and the amount of blood available in the intravascular bed. Indices commonly used to reflect blood volume are unreliable and fraught with error. For example, the haematocrit percentage only indicates the volume that red cells occupy in a sample of blood expressed as a percentage of the total volume of the sample. The trend in blood and fluid therapy is towards reinstituting physiologic functions by quantitatively replacing the elements that constitute blood volume in vivo. In modern methods, circulating blood is considered to be an unknown diluent to which a known quantity of tracer is added. The final concentration of tracer in the blood is therefore, indirectly and inversely proportional to the volume of the diluent, i.e. the blood volume.

Single tracers are routinely used for simplicity in measuring blood volume, and normally short-lived isotopes are used. This experiment makes use of 3H (which would not be used for blood volume measurements in practice) in the form of tritiated water, and circulation apparatus containing approximately the same volume of water as the average adult male has blood.

Experimental procedure for Determination of a volume using dilution technique with a single tritium tracer

Questions for Determination of a volume using dilution technique with a single tritium tracer