Simultaneous sampling of tissue oxygenation and oxygen consumption in skeletal muscle

Abstract

Under physiologic conditions, microvascular oxygen delivery appears to be well matched to oxygen consumption in respiring tissues. We present a technique to measure interstitial oxygen tension (PISFO2) and oxygen consumption (VO2) under steady-state conditions, as well as during the transitions from rest to activity and back. Phosphorescence Quenching Microscopy (PQM) was employed with pneumatic compression cycling to achieve 1 to 10 Hz sampling rates of interstitial PO2 and simultaneous recurrent sampling of VO2 (3/min) in the exteriorized rat spinotrapezius muscle. The compression pressure was optimized to 120–130 mmHg without adverse effect on the tissue preparation. A cycle of 5 s compression followed by 15 s recovery yielded a resting VO2 of 0.98 ± 0.03 ml O2/100cm3 min while preserving microvascular oxygen delivery. The measurement system was then used to assess VO2 dependence on PISFO2 at rest and further tested under conditions of isometric muscle contraction to demonstrate a robust ability to monitor the on-kinetics of tissue respiration and the compensatory changes in PISFO2 during contraction and recovery. The temporal and spatial resolution of this approach is well suited to studies seeking to characterize microvascular oxygen supply and demand in thin tissues.

Skeletal muscle microvascular and interstitial from rest to contractions

“…; Nugent et al . ). Moreover, limited temporal resolution has precluded kinetics analyses during the contraction transient in the past.…”

“…; Nugent et al . ). The reasons for this discrepancy are not entirely clear but could involve methodological aspects (e.g.…”

“…; Nugent et al . ), thus reflecting the imposed metabolic demand (Howlett & Hogan, ; Howlett et al . ).…”

Skeletal muscle interstitial O2 pressures: bridging the gap between the capillary and myocyte

“…A recent investigation from our laboratory thus aimed to resolve the temporal profile and determine the model parameters of PO 2 is on‐kinetics in healthy skeletal muscle (Figure , filled symbols in left panel) . In that study, baseline PO 2 is in the resting spinotrapezius muscle (16 ± 2 mm Hg) was lower than reported previously using phosphorescence quenching (~28 and 68 mm Hg) . The exact bases for this divergence are unclear but could involve methodological differences in probe delivery and/or localization, spatial resolution and phosphorescence quenching analyses.…”

“…Previous phosphorescence quenching assessment of muscle PO 2 is during metabolic transients has produced divergent results (eg, in absolute resting and contracting values) and, until recently, no formal description of its dynamic profile existed . A recent investigation from our laboratory thus aimed to resolve the temporal profile and determine the model parameters of PO 2 is on‐kinetics in healthy skeletal muscle (Figure , filled symbols in left panel) .…”