The blood volume of a patient is to be determined by means of 32P. For this purp

Question

The blood volume of a patient is to be determined by means of 32P. For this purpose, 15.0 ml of blood is withdrawn from the patient and mixed with a very small volume of Na2H(32P)O4 of high specific activity. In 1 hour the erythrose (red blood cells) take up all the 32P; 1ml is found to have an activity of 216,000 cpm in the detector system used. Exactly 5ml of this tagged sample is reinjected into the patient and 30min later a new sample is withdrawn; 10ml of this gives 2,300 cpm. Calculate the blood volume.

Explanation / Answer

1 ml sample = 216000 cpm

5 ml of this sample is injected

So the activity of the 5 ml sample = (216000 * 5 ) cpm

This 5 mal sample is injected in the body,

so the activity of the whole blood volume (V) should be = (216000 * 5) cpm

10 ml of the new sample has activity 2300

So

V = 216000 * 5 * 10 / 2300 (Simple cross multiplication)

V = 4695 ml

So the blood volume is 4695 ml

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