circulation time, the time required for blood to flow from one part of the body to another. Timing a particle of blood involves injecting a traceable dye or radioisotope into a vein and timing its reappearance in an artery at the point of injection. Alternatively, a substance that can be tasted, such as saccharin, can be injected and the time it takes to travel to the tongue noted. The resulting time helps determine problems with heart failure and decreased cardiac output.
