Novel Insight Into the Determinants of Skeletal Muscle Oxygen Consumption by Dual‐Wavelength Diffuse Correlation Spectroscopy

Abstract

Near‐infrared diffuse correlation spectroscopy (DCS) is a promising new optical imaging technique to noninvasively quantify microvascular perfusion. Combining DCS with conventional near‐infrared spectroscopy (NIRS) provides novel insight into the determinants of skeletal muscle oxygen consumption, by measuring microvascular oxygen delivery (by DCS) and oxygen utilization (by NIRS, i.e. tissue saturation). To test this hypothesis, we compared DCS‐derived measures of skeletal muscle oxygen delivery and utilization against Doppler ultrasound and direct measures of oxygen saturation from the venous effluent of the exercising muscle. Eight healthy male subjects (age 27.2 ± 4.2; BMI 26.9 ± 4.3) performed a graded handgrip exercise test. Subjects were instructed to perform rhythmic hand grip exercise on a two‐second duty cycle, at 10, 13, 16, and 19 kg. All subjects were instrumented with the DCS probe placed over the belly of the flexor digitorum profundus, a retrograde venous catheter (deep vein) inserted into the antecubital vein, and Doppler ultrasound over the brachial artery. Heart rate was monitored by ECG and blood pressure by continuous finger‐pressure of the non‐gripping hand. The major findings were two‐fold: First, we observed a strong intra‐individual relationship between DCS‐derived muscle perfusion and Doppler‐derived brachial artery blood flow (r2 = 0.95). Second, we observed an unexpected dissociation between skeletal muscle saturation, as measured by DCS, which declined progressively with each incremental workload (BL 71.9 ± 0.29%, 10kg 68.4 ± 0.91%, 13 kg 64.2 ± 1.04%, 16kg 61.8 ± 0.54%, 19kg 59.4 ± 1.26%), while directly measured venous oxygen saturation declined with the onset of exercise but remained unchanged thereafter (BL, 65.3 ± 7.20%; 10kg, 39.8 ± 8.42%; 13 kg, 39.5 ± 7.83%, 16kg, 42 ± 4.14%, 19kg, 41 ± 3.38%). Taken together, these results support DCS as a valuable tool, capable of providing novel insight into the determinants of skeletal muscle oxygen consumption at the microvascular level. The fact that tissue saturation was dissociated from venous saturation suggests that DCS may provide insight beyond conventional measurements.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.