NIRS and indocyanine-green-determined muscle blood flow during exercise in humans

摘要

We present a method for determination of muscle blood flow (MBF) using near infrared spectroscopy (NIRS) with indocyanine green (ICG) as the tracer. MBF was quantified using the integrated arterial $LB@ICG$RB and the accumulation of ICG in muscle. MBF was determined together with ICG-assessed cardiac output (CO) at rest and during incremental cycling. To further modify CO, the same work loads were performed after cardio-selective beta blockade by metoprolol. In one subject both MBF (9 to 110 ml $DOT 100 g$+$MIN@1$/ $DOT min$+$MIN@1$/) and CO increased linearly with work rate (8 to 19 l $DOT min$+$MIN@1$/). Under beta blockade, both the increase in MBF and CO were lower: 5 to 70 ml $DOT 100 g$+$MIN@1$/ $DOT min$+$MIN@1$/ and 5 to 161 DOT min$+$MIN@1$/, respectively. During exercise with and without beta blockade, MBF increased with work load to represent a larger proportion of CO. Also, NIRS could detect an attenuated increase in MBF manifest by the restrained CO during leg exercise after cardio-selective beta blockade. Both observations indicate that NIRS detection of indocyanine green provides an estimate of muscle blood flow over the range from rest to intense exercise.