ARM BLOOD-FLOW AT REST AND DURING ARM EXERCISE

To test the applicability of a dye-dilution method to quantitate total arm blood flow at rest and during arm exercise, indocyanine green was infused at a constant rate into the brachial artery. Eight subjects performed continuous 30-min arm exercises with an increase in intensity every 10 min (30, 60, and 90 W). The loads corresponded to 29 +/- 1, 48 +/- 2, and 78 +/- 4% (means +/- SE) of the maximal O2 uptake (VO2(max) 2.13 +/- 0.08 1/min) during arm exercise. VO2(max) during arm exercise was 61 +/- 1.7% of that during leg exercise. The dye concentration was analyzed in blood samples from three arm veins, two ipsi- and one contralateral, at shoulder level. Corresponding dye concentrations in both ipsilateral veins and a stable concentration difference between ipsi- and contralateral veins were achieved. Total arm blood flow was calculated to be 0.21 +/- 0.04 1/min at rest and 2.43 +/- 0.14 1/min at 90 W. Arm O2 uptake rose from 9 +/- 2 to 323 +/- ml/min. Arm blood flow and O2 uptake each correlated linearly with both work load (r = 0.98) and pulmonary O2 uptake (r greater-than-or-equal-to 0.98). Mechanical efficiency for the arm and body was 34-44 and 16-19%, respectively. We conclude that arm blood flow can be determined by continuous infusion of indocyanine green.