Determinants of skeletal muscle oxygen consumption assessed by near-infrared diffuse correlation spectroscopy during incremental handgrip exercise

Abstract

Near-infrared diffuse correlation spectroscopy (DCS) is a rapidly evolving optical imaging technique for the assessment of skeletal muscle O2 utilization (mVO2). We compared DCS-derived determinants of mVO2 with conventional measures [blood flow by brachial artery Doppler ultrasound and venous O2 saturation ([Formula: see text])] in eight volunteers at rest and during incremental handgrip exercise. Brachial artery blood flow and DCS-derived blood flow index (BFI) were linearly related (R2 = 0.57) and increased with each workload, whereas [Formula: see text] decreased from 65.3 ± 2.5% (rest) to 39.9 ± 3.0% (light exercise; P < 0.01) with no change thereafter. In contrast, DCS-derived tissue O2 saturation decreased progressively with each incremental stage ( P < 0.01), driven almost entirely by an initial steep rise in deoxyhemoglobin/myoglobin, followed by a linear increase thereafter. Whereas seemingly disparate at first glance, we believe these two approaches provide similar information. Indeed, by plotting the mean convective O2 delivery and diffusive O2 conductance, we show that the initial increase in mVO2 during the transition from rest to exercise was achieved by a greater increase in diffusive O2 conductance versus convective O2 delivery (10-fold vs. 4-fold increase, respectively), explaining the initial decline in [Formula: see text]. In contrast, the increase in mVO2 from light to heavy exercise was achieved by equal increases (1.8-fold) in convective O2 delivery and diffusive O2 conductance, explaining the plateau in [Formula: see text]. That DCS-derived BFI and deoxyhemoglobin/myoglobin (surrogate measure of O2 extraction) share the same general biphasic pattern suggests that both DCS and conventional approaches provide complementary information regarding the determinants of mVO2. NEW & NOTEWORTHY Near-infrared diffuse correlation spectroscopy (DCS) is an emerging optical imaging technique for quantifying skeletal muscle O2 delivery and utilization at the microvascular level. Here, we show that DCS provides complementary insight into the determinants of muscle O2 consumption across a wide range of exercise intensities, further establishing the utility of DCS.

Vascular ATP‐sensitive K+ channels support maximal aerobic capacity and critical speed via convective and diffusive O2 transport

“…2005), during handgrip exercise (Rosenberry et al . 2019) and in disease populations during isolated knee extensor and cycling exercise (chronic obstructive pulmonary disease: Broxterman et al . 2020; HFrEF: Esposito et al .…”

“…The interplay between convective and diffusive O 2 delivery on muscleVO 2 has been assessed directly in healthy skeletal muscle across fibre types (Behnke et al 2003;McDonough et al 2005), during handgrip exercise (Rosenberry et al 2019) and in disease populations during isolated knee extensor and cycling exercise (chronic obstructive pulmonary disease: Broxterman et al 2020;HFrEF: Esposito et al 2010). To our knowledge, the current investigation is the first to assess changes in convective and diffusive O 2 conductance following specific channel/enzyme inhibition and provides evidence that this approach can ) Figure 4.…”

Near-infrared diffuse correlation spectroscopy tracks changes in oxygen delivery and utilization during exercise with and without isolated arterial compression

“…Whereas bulk conduit brachial artery blood flow (measured by Doppler ultrasound) followed changes in perfusion pressure during arm manipulation, microvascular perfusion was preserved during steady-state handgrip exercise, which we interpreted as evidence of myogenic autoregulation (46). In a separate, more recent NIR-DCS study, we challenged the system using a graded handgrip exercise test, hoping to observe a divergence between oxygen delivery and oxygen extraction at higher workloads (39). However, in this small muscle mass model, oxygen delivery and extraction increased linearly with each workload.…”

“…Diffuse correlation spectroscopy (DCS) is an emerging optical imaging approach to measure skeletal muscle perfusion during exercise (3,22,39,46). DCS is completely noninvasive and has high temporal resolution for measuring relative changes in blood flow at the level of the microvasculature (3,7).…”

“…Pairing DCS with near-infrared spectroscopy (NIRS), an established noninvasive technique for characterizing the transport and utilization of oxygen through the microcirculation (4,5,11,15,19,23,39,42,46), allows for simultaneous measurement of oxygen delivery and utilization (determinants of skeletal muscle oxygen consumption) at the level of the microvasculature. Indeed, recent studies performed in our laboratory (3,39,46) demonstrate good concurrent validity between near-infrared diffuse correlation spectroscopy (NIR-DCS) and conventional measures of oxygen delivery (Doppler Ultrasound) and utilization (venous oxygen saturation) during both fixed workload (46) and incremental (39) handgrip exercise. However, it is still unclear whether NIR-DCS can track acute perturbations in oxygen delivery and utilization at the level of the microvasculature.…”