Mg. Clark et al., Failure of laser Doppler signal to correlate with total flow in muscle: Isthis a question of vessel architecture?, MICROVASC R, 60(3), 2000, pp. 294-301
The signal strength from LDF probes positioned in perfused muscle can be al
tered by vasoconstrictors despite total flow being maintained constant. Apa
rt from redistribution of flow via collateral channels outside the region o
f measurement, the change in LDF signal may arise because the vasoconstrict
ors have switched now to vessels of different architecture or altered the a
rchitecture of the blood vessels being perfused. Thus we have examined the
effect of tube architecture on LDF signal using polymer tubes of 250, 100,
and 50 mum internal diameter. At 3% hematocrit the LDF signal was linear fo
r each of the three tube sizes from 10 to 80 mul/h. The signal strength was
greatest from the smallest tube and least from the largest tube. For a sin
gle tube (100 mum) that doubled back on itself twice to cross the field of
measurement three times, the LDF signal at any now (10-80 mul/h, hematocrit
3%) was approx threefold greater than that for the same tube crossing the
field of measurement once. The effect of progressively switching flow (cons
tant at 120 mul/h, hematocrit 9%) from five to one tube in a manifold of fi
ve tubes (100 mum) gave rise to a progressive increase in signal. It is con
cluded that LDF signal derives predominantly from nonvectorial cell speed a
nd less from cell number. Thus any agent that alters the architecture has t
he potential to alter the LDF signal. (C) 2000 Academic Press.