Kinetics of muscle deoxygenation and microvascular Po₂ during contractions in rat: comparison of optical spectroscopy and phosphorescence-quenching techniques

Abstract

The overarching presumption with near-infrared spectroscopy measurement of muscle deoxygenation is that the signal reflects predominantly the intramuscular microcirculatory compartment rather than intramyocyte myoglobin (Mb). To test this hypothesis, we compared the kinetics profile of muscle deoxygenation using visible light spectroscopy (suitable for the superficial fiber layers) with that for microvascular O(2) partial pressure (i.e., Pmv(O(2)), phosphorescence quenching) within the same muscle region (0.5∼1 mm depth) during transitions from rest to electrically stimulated contractions in the gastrocnemius of male Wistar rats (n = 14). Both responses could be modeled by a time delay (TD), followed by a close-to-exponential change to the new steady level. However, the TD for the muscle deoxygenation profile was significantly longer compared with that for the phosphorescence-quenching Pmv(O(2)) [8.6 ± 1.4 and 2.7 ± 0.6 s (means ± SE) for the deoxygenation and Pmv(O(2)), respectively; P < 0.05]. The time constants (τ) of the responses were not different (8.8 ± 4.7 and 11.2 ± 1.8 s for the deoxygenation and Pmv(O(2)), respectively). These disparate (TD) responses suggest that the deoxygenation characteristics of Mb extend the TD, thereby increasing the duration (number of contractions) before the onset of muscle deoxygenation. However, this effect was insufficient to increase the mean response time. Somewhat differently, the muscle deoxygenation response measured using near-infrared spectroscopy in the deeper regions (∼5 mm depth) (∼50% type I Mb-rich, highly oxidative fibers) was slower (τ = 42.3 ± 6.6 s; P < 0.05) than the corresponding value for superficial muscle measured using visible light spectroscopy or Pmv(O(2)) and can be explained on the basis of known fiber-type differences in Pmv(O(2)) kinetics. These data suggest that, within the superficial and also deeper muscle regions, the τ of the deoxygenation signal may represent a useful index of local O(2) extraction kinetics during exercise transients.

Relationship between (non)linear phase II pulmonary oxygen uptake kinetics with skeletal muscle oxygenation and age in 11–15 year olds

“…In the present study, we did observe a significant association between a decreased G p with the relative speeding of the MRT‐Δdeoxy[Hb+Mb] following the onset of U → VH compared to U → M. It has been reported that the τ of deoxy[Hb+Mb] kinetics coheres with that observed for the reduction in microvascular following the onset of skeletal muscle contractions (Koga et al., ). Accordingly, it is conceivable that those participants evincing a greater ‐to‐ mismatch (i.e.…”

Sildenafil improves microvascular O2 delivery-to-utilization matching and accelerates exercise O2 uptake kinetics in chronic heart failure

“…A caveat particularly pertinent to the present study, however, is its inability to differentiate Hb from Mb with regard to light absorption. However, by comparing muscle deoxygenation with PO 2mv , determined by phosphorescence quenching within the same muscle region in rat preparations, Koga et al (29) confirmed that the deoxygenation signal did provide a valid index of local fractional O 2 extraction kinetics during exercise transients.…”

Effect of differential muscle activation patterns on muscle deoxygenation and microvascular haemoglobin regulation

“…Barstow, ). In particular, time‐resolved NIRS (TR‐NIRS) was used to investigate non‐invasively the matching {via deoxy[haemoglobin + myoglobin] (deoxy[Hb + Mb]) and tissue O 2 saturation ()} and microvascular haematocrit (via total[Hb + Mb]) within specific muscle regions (Federspiel & Popel, ; Groebe & Thews, ; Koga et al., , ; Okushima et al., ). Crucially, TR‐NIRS measures in vivo optical path length distribution, facilitating resolution of absolute [Hb + Mb].…”