Microvascular blood flow during vascular occlusion tests assessed by diffuse correlation spectroscopy

Abstract

Vascular function can be assessed by measuring post-occlusion hyperaemic responses along the arterial tree (vascular occlusion test; VOT). It is currently unclear if responses are similar across vascular beds following cuff release, given potential differences in compliance. To examine this, we compared laser Doppler-derived blood flux in the cutaneous circulation (LDF cut) and skeletal muscle microvascular blood flux (BFI) using diffuse correlation spectroscopy (DCS), to brachial artery blood flow (BABF) during VOT. We hypothesized that during a VOT following cuff release, (1) BFI response would be delayed compared to the brachial artery response, and (2) time to peak blood flux in the cutaneous vasculature would be slower than both brachial artery and skeletal muscle responses. Seven healthy men (26 ± 4 years) performed three trials of a brachial artery VOT protocol with 10 min of rest between trials. A combined DCS and near-infrared spectroscopy probe provided BFI and oxygenation characteristics (total-[haem]), respectively, of skeletal muscle. BABF was determined via Doppler ultrasound and microvascular cutaneous blood flux was determined via LDF cut. Following cuff release, time to peak of BFI (32.3 ± 6.0 s) was significantly longer than BABF (7.3 ± 2.5 s), LDF cut (10.0 ± 6.4 s) and total-[haem] (14.2 ± 8.3 s) (all P < 0.001). However, time to peak of BABF, LDF cut and total-[haem] were not significantly different (P > 0.05). These results suggest mechanistic differences in control of cutaneous and muscular blood flow distribution after transient ischaemia.

Influence of blood flow occlusion on muscular recruitment and fatigue during maximal‐effort small muscle‐mass exercise

“…2014; Didier et al . 2020), the time courses for post‐occlusive microvascular hyperaemia (Didier et al . 2020) and tissue oxygenation (Bopp et al .…”

“…2020), the time courses for post‐occlusive microvascular hyperaemia (Didier et al . 2020) and tissue oxygenation (Bopp et al . 2011) of the forearm appear similar to the rise in force production from the present study.…”

Mild obesity does not affect the forearm muscle microvascular responses to hyperglycemia

“…25,38 For instance, as previously discussed, while the %FMD response is mainly NO/endothelium-dependent, which is known to be negatively affected by obesity and hyperglycemia, the mechanisms controlling microvascular reactivity to an ischemia/reperfusion stimulus has been suggested to be associated with a microvascular response to the mechanical and ischemic insult generated by cuff inflation. 39,40 In connection to this idea, the positive correlations between fasting insulin and the reperfusion slope, although only significant in the lean group, opposed to the relationship between insulin and %FMD observed in Figure 3 First, the trend for higher %FMD in obese individuals compared with the lean participants observed in the current investigation is to some extent surprising. However, in addition to the fact that findings related to differences in %FMD between lean and obese individuals are still controversial, [43][44][45] it is likely that the smaller brachial artery diameter found in the obese group may have resulted in a greater shear rate at cuff release and, consequently, greater stimulus for the FMD when compared to the lean individuals.…”

“…Finally, the controversy of the findings related to the effects of obesity on the vascular responses to glucose ingestion is also largely influenced by the heterogeneity of the effects of obesity throughout the vascular tree and the differences in mechanisms controlling vascular function at different vascular beds 25,38 . For instance, as previously discussed, while the %FMD response is mainly NO/endothelium‐dependent, which is known to be negatively affected by obesity and hyperglycemia, the mechanisms controlling microvascular reactivity to an ischemia/reperfusion stimulus has been suggested to be associated with a microvascular response to the mechanical and ischemic insult generated by cuff inflation 39,40 . In connection to this idea, the positive correlations between fasting insulin and the reperfusion slope, although only significant in the lean group, opposed to the relationship between insulin and %FMD observed in Figure 3, which further indicates differences in the mechanisms controlling conduit artery and microvascular function and in the link of metabolic effects of insulin and vascular reactivity.…”

Limitations to exercise tolerance in type 1 diabetes: the role of pulmonary oxygen uptake kinetics and priming exercise

“…and is thus likely to more closely represent the factors limiting skeletal muscle respiration in the interrogated region when compared to central measures of O2 delivery (3,20,21,30).…”