Diffusion processes invalidating the intra-arterial krypton-85 beta-particle clearance method for measurement of skin blood flow in man.

Krypton-85 dissolved in 0.9% NaCl was injected into the femoral artery of man; fi particles were measured over the skin of the eras. Cutaneous mean blood flow was calculated using the integral equation of Zierler based on the mean transit time analysis of clearance curves recorded from the cutaneous tissue; these calculations gave estimates which were only about one-fifth those obtained by other methods. The low estimates were caused by an intercompartmental exchange of ^krypton between the cutaneous and subcutaneous tissues, an exchange implying that both tissues influence the shape of the clearance curve recorded from the cutaneous tissue alone. This intercompartmental exchange was effected not only by diffusion directly from the cutaneous to the subcutaneous tissue, but presumably also by transport from the blood streaming between the two tissues. The clearance rate of the tail of the curve was shown to correspond to that of the subcutaneous tissue. The errors distorting the clearance curve of /3 particles may invalidate the use of intra-arterial injection and measurement of clearance curves of /3 particles for measurement of blood flow in other tissues. ADDITIONAL