Microcirculatory dysfunction contributes to morbidity and mortality in vascular diseases. Here, we aimed at establishing a sensitive and valid method to measure microvascular reactivity during post-occlusive reactive hyperemia (PORH) using scanning laser Doppler perfusion imaging (LDPI) of the forearm.
In a first series, LDPI was methodologically evaluated on the volar forearm of healthy volunteers (n = 10) before and after one to five minutes of upper arm occlusion. In a second series, readings were performed in 20 healthy subjects and 20 patients with coronary artery disease (CAD).
Three minutes of forearm occlusion were sufficient to induce maximal vasodilation during PORH as indicated by maximal increase in perfusion unit (PU) amplitude that did not further increase after five-minute occlusion. Five-minute occlusion led to a significant prolongation of PORH with greater area under curve (AUC) suggesting longer lasting vasodilation of microvessels. The five-minute occlusion was associated with lower variability as compared with three minutes (intraindividual variability: 9-17% vs. 12-21%; interindividual variability: 13-24% vs. 14-26%). CAD patients exhibited significantly reduced amplitude (105 +/- 49 vs. 164 +/- 35 PU; p < 0.001), ratio (4.7 +/- 1.8 vs. 7.1 +/- 1.8; p < 0.001), and AUC (1656 +/- 1070 vs. 2723 +/- 864 PU x minutes; p = 0.001).
Scanning LDPI is a feasible and reproducible method for non-invasive assessment of the cutaneous microcirculatory response during PORH.
[Show abstract][Hide abstract] ABSTRACT: Both spatial variability and temporal variability of skin blood flow are high. Laser speckle contrast imagers (LSCI) allow non-contact, real-time recording of cutaneous blood flow on large skin surfaces. Thereafter, the observer can define different sizes for the region of interest (ROI) in the images to decrease spatial variability and different durations over which the blood flow values are averaged (time of interest, TOI) to decrease temporal variability. We aimed to evaluate the impact of the choices of ROI and TOI on the analysis of rest blood flow and post occlusive reactive hyperemia (PORH).
Cutaneous blood flow (CBF) was assessed at rest and during PORH. Three different sizes of ROI (1mm(2), 10mm(2) and 100mm(2)), and three different TOI (CBF averaged over 1s, 15s, and 30s for rest, and over 1s, 5s and 10s for PORH peak) were evaluated. Inter-subjects and intra-subjects coefficient of variations (inter-CV and intra-CV) were studied.
The inter-subject variability of CBF is about 25% at rest and is moderately improved when the size of the ROI increases (inter-CV=31%, for 1s and 1mm(2) versus inter-CV=23%, for 15s and 100mm(2)). However, increasing the TOI does not improve the results. The variability of the PORH peak is lower with an inter-CV varying between 11.4% (10s and 100mm(2)) and 21.6% (5s and 1mm(2)). The lowest intra-CV for the CBF at rest was 7.3% (TOI of 15s on a ROI of 100mm(2)) and was 3.1% for the PORH peak (TOI of 10s on a ROI of 100mm(2)).
We suggest that a size of ROI larger than 10mm(2) and a TOI longer than 1s are required to reduce the variability of CBF measurements both at rest and during PORH peak evaluations at the forearm level. Many technical aspects such as comparison of laser speckle contrast imaging and laser Doppler imaging or the effect of skin to head distance on recorded values with LCSI are required to improve future studies using this fascinating clinical tool.
Microvascular Research 03/2011; 82(1):88-91. DOI:10.1016/j.mvr.2011.03.009 · 2.13 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To investigate whether a daily intake of a moderate dose of antioxidants modifies the microcirculatory response to smoking, assuming a major influence of oxidative stress on microcirculation.
The microvascular response to smoking was assessed in individual capillaries by capillaroscopy before and after two weeks of treatment with oral antioxidants.
Smoking prolonged time to peak (TtP) capillary blood flow velocity in all subjects. When the subjects were pre-treated with ascorbate, TtP was comparable to baseline values of untreated subjects. No significant effect of vitamin E was observed either before or after smoking. Capillary blood flow velocity increased after treatment with ascorbate as well as after vitamin E. However, significant reductions in velocity were still observed in response to smoking even after subjects consumed ascorbate and vitamin E (p<0.0004 and p<0.000008 respectively).
This study focused on individual capillaries, and confirms that smoking has a very pronounced, direct and reproducible microvascular effect possible to demonstrate in vivo in human capillaries. Moderate intake of the antioxidant ascorbate clearly mitigated the effects induced by smoking. TtP after smoking in subjects treated with ascorbate was similar to that observed in untreated subjects before smoking a cigarette. Thus, oxidative stress could be assumed to play a role in the effects of smoking on microcirculation.
Microcirculation (New York, N.Y.: 1994) 08/2011; 19(1):86-93. DOI:10.1111/j.1549-8719.2011.00125.x · 2.57 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: For more than two decades, methods for the non-invasive exploration of cutaneous microcirculation have been mainly based on optical microscopy and laser Doppler techniques. In this review, we discuss the advantages and drawbacks of these techniques. Although optical microscopy-derived techniques, such as nailfold videocapillaroscopy, have found clinical applications, they mainly provide morphological information about the microvessels. Laser Doppler techniques coupled with reactivity tests are widespread in the field of microvascular function research, but many technical issues need to be taken into account when performing these tests. Post-occlusive reactive hyperemia and local thermal hyperemia have been shown to be reliable tests, although their underlying mechanisms are not yet fully understood. Acetylcholine and sodium nitroprusside iontophoresis, despite their wide use as specific tests of endothelium-dependent and -independent function, respectively, show limitations. The influence of the skin site, recording conditions, and the way of expressing data are also reviewed. Finally, we focus on promising tools such as laser speckle contrast imaging.
Microcirculation (New York, N.Y.: 1994) 08/2011; 19(1):47-64. DOI:10.1111/j.1549-8719.2011.00129.x · 2.57 Impact Factor
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