Skin microcirculation in peripheral arterial obliterative disease

The Mechanism of Effort Intolerance in Patients with Peripheral Arterial Disease: A Combined Stress Echocardiography and Cardiopulmonary Exercise Test

AIM

We used a combined stress echocardiography and cardiopulmonary exercise test (CPET) to explore effort intolerance in peripheral arterial disease (PAD) patients.

METHODS

Twenty-three patients who had both PAD and coronary artery disease (CAD) were compared with twenty-four sex- and age-matched CAD patients and fifteen normal controls using a symptom-limited ramp bicycle CPET on a tilting dedicated ergometer. Echocardiographic images were obtained concurrently with gas exchange measurements along predefined stages of exercise. Oxygen extraction was calculated using the Fick equation at each activity level.

RESULTS

Along the stages of exercise (unloaded; anaerobic threshold; peak), in PAD + CAD patients compared with CAD or controls, diastolic function worsened (p = 0.051 and p = 0.013, respectively), and oxygen consumption (p < 0.001 and p < 0.001, respectively) and oxygen pulse (p = 0.0024 and p = 0.0027, respectively) were reduced. Notably, oxygen pulse was blunted due to an insufficient increase in both stroke volume (p = 0.025 and p = 0.028, respectively) and peripheral oxygen extraction (p = 0.031 and p = 0.038, respectively). Chronotropic incompetence was more prevalent in PAD patients and persisted after correction for beta-blocker use (62% vs. 42% and 11%, respectively).

CONCLUSIONS

In PAD patients, exercise limitation is associated with diastolic dysfunction, chronotropic incompetence and peripheral factors.

Lower Limb Arterial Ischemia: An Independent Risk Factor of Sudomotor Dysfunction in Type 2 Diabetes

BACKGROUND

As an early manifestation of diabetic peripheral neuropathy (DPN), sudomotor dysfunction significantly increases the risk of diabetic foot ulcer. The pathogenesis of sudomotor dysfunction is still unclear. Lower limb ischemia may be related to sudomotor dysfunction, but few studies have explored it. The purpose of this study is to explore the relationship between sudomotor function and comprehensive lower limb arterial ischemia including large arteries, small arteries and microvascular in type 2 diabetes mellitus (T2DM).

PATIENTS AND METHODS

511 T2DM patients were enrolled in this cross-sectional study. Sudomotor function was assessed qualitatively and quantitatively by Neuropad. Lower limb arterial ischemia was defined as any abnormality of the ankle brachial index (ABI), toe brachial index (TBI) or transcutaneous oxygen tension (TcPO2).

RESULTS

In this study, 75.1% of patients had sudomotor dysfunction. Compared with normal sudomotor function, patients with sudomotor dysfunction had a higher incidence of lower limb arterial ischemia (51.2% vs 36.2%, p = 0.004). Similarly, compared with the non-arterial ischemia group, the proportion of sudomotor disorders was higher in the arterial ischemia group (p = 0.004). Low TBI and low TcPO2 groups also had a higher proportion of sudomotor disorders (all p < 0.05).Compare with normal groups, low ABI, low TBI, and low TcPO2 groups had lower Slop4 which quantitatively reflecting Neuropad discoloration. Arterial ischemia was an independent risk factor for sudomotor dysfunction [OR = 1.754, p = 0.024]. Low TcPO2 also independently increased the risk of sudomotor disorders [OR = 2.231, p = 0.026].

CONCLUSION

Lower limb arterial ischemia is an independent risk factor of sudomotor dysfunction. Especially below the ankle (BTA) small arteries and microvascular ischemia may also be involved in the occurrence of sudomotor disorders.

The effect of 12-week treatment with intermittent negative pressure on blood flow velocity and flowmotion, measured with a novel Doppler device (earlybird). Secondary outcomes from a randomized sham-controlled trial in patients with peripheral arterial disease

OBJECTIVES

Treatment with intermittent negative pressure (INP) is proposed as an adjunct to standard care in patients with peripheral arterial disease (PAD). The aims of this study were to evaluate the applicability of a novel ultrasound Doppler device (earlybird) to assess blood flow characteristics in patients with PAD during a treatment session with INP, and whether certain flow-properties could determine whom could benefit INP treatment.

METHODS

Secondary outcomes of data from a randomized sham-controlled trial were explored. Patients were randomized to 12 weeks of treatment with 40 mmHg or 10 mmHg INP, for one hour twice daily. Earlybird blood flow velocity recordings were made before and after the 12-week treatment-period and consists of a 5-minute recording in rest, 3-minute during INP treatment and 5-minute recording after ended INP test-treatment. Mean blood flow velocity (v_mean), relative changes in flow and frequency spectrum by Fourier-transform of the respective bandwidths of endothelial, sympathetic, and myogenic functions, were analyzed for the different series of blood flow measurements.

RESULTS

In total, 62 patients were eligible for analysis, where 32 patients were treated with 40 mmHg INP. The acquired recordings were of good quality and was used for descriptive analyses of flow characteristics. An immediate increase in v_mean during the negative pressure periods of the INP test-treatment was observed in the 40 mmHg INP treatment group at both pre- and post-test. There was a significant difference between the treatment groups, with a difference between the medians of 13.7 (p < 0.001) at pretest and 10.7 (p < 0.001) at posttest. This finding was confirmed with spectrum analysis by Fourier-transform of the bandwidth corresponding to INP treatment. The change in amplitude corresponding to myogenic function after 12 weeks of treatment, was significantly different in favor of the 40 mmHg INP treatment group. We were not able to detect specific flow characteristics indicating whom would benefit INP-treatment.

CONCLUSIONS

Earlybird is an applicable tool for assessing blood flow velocity in patients with PAD. Analysis of the flow velocity recordings shows that INP induce an immediate increase in blood flow velocities during INP. The positive effects of INP may be attributed to recruitment of arterioles, and thereby increasing blood flow. In these analyses no flow characteristics was determined which could predict whom would benefit INP-treatment.

Autologous Stem Cell Therapy for Chronic Lower Extremity Wounds: A Meta-Analysis of Randomized Controlled Trials

Lower extremity chronic wounds (LECWs) commonly occur in patients with diabetes mellitus (DM) and peripheral arterial disease (PAD). Autologous stem cell therapy (ASCT) has emerged as a promising alternative treatment for those who suffered from LECWs. The purpose of this study was to assess the effects of ASCT on LECWs. Two authors searched three core databases, and independently identified evidence according to predefined criteria. They also individually assessed the quality of the included randomized controlled trials (RCTs), and extracted data on complete healing rate, amputation rate, and outcomes regarding peripheral circulation. The extracted data were pooled using a random-effects model due to clinical heterogeneity among the included RCTs. A subgroup analysis was further performed according to etiology, source of stem cells, follow-up time, and cell markers. A total of 28 RCTs (n = 1096) were eligible for this study. The pooled results showed that patients receiving ASCT had significantly higher complete healing rates (risk ratio (RR) = 1.67, 95% confidence interval (CI) 1.28-2.19) as compared with those without ASCT. In the CD34+ subgroup, ASCT significantly led to a higher complete healing rate (RR = 2.70, 95% CI 1.50-4.86), but there was no significant difference in the CD34- subgroup. ASCT through intramuscular injection can significantly improve wound healing in patients with LECWs caused by either DM or critical limb ischemia. Lastly, CD34+ is an important cell marker for potential wound healing. However, more extensive scale and well-designed studies are necessary to explore the details of ASCT and chronic wound healing.

Identification of Gingival Microcirculation Using Laser Doppler Flowmetry in Patients with Orthodontic Treatment-A Longitudinal Pilot Study

Background and Objectives: Orthodontic tooth movement is associated with inflammatory responses. The aim of this study was to identify gingival microcirculation using laser Doppler flowmetry in patients with orthodontic treatment. Materials and Methods: A longitudinal pilot study was performed. The participants were selected using a non-probability consecutive sampling. Of the twenty-five subjects, a total of six (four women and two men) complied with the criteria. Before and during the treatment, the oral hygiene index, gingival index, probing depth, level of epithelial attachment, and gingival microcirculation were evaluated with laser Doppler flowmetry (integrated parameters: 1. integrated primary basal flow (IPBF), 2. integrated total secondary real flow (ITSRF), and 3. difference between integration (DBI)) in all of the participants). Results: (a) An increase in gingival blood flow was identified at all time intervals with different arches during orthodontic treatment. (b) The IPBF and ITSRF (with treatment) identified after 20 min (treatment initial stage) were compared with the different time intervals, and we observed an increase in gingival perfusion at the 24th, 48th, and 72nd hours in some arches. (c) In the DBI, we found statistically significant differences (p < 0.005) in the Nitinol group of 0.016 inches among all the time intervals (24 h, 48 h, and 72 h) within the 30-day interval, observing a flow increase three times greater than the basal flow after 30 days. Conclusions: Healthcare professionals must identify the inflammatory processes in treatment to observe and discontinue use of harmful methods in clinical practice.

Perfusion Patterns in Patients with Chronic Limb-Threatening Ischemia versus Control Patients Using Near-Infrared Fluorescence Imaging with Indocyanine Green

In assessing the severity of lower extremity arterial disease (LEAD), physicians rely on clinical judgements supported by conventional measurements of macrovascular blood flow. However, current diagnostic techniques provide no information about regional tissue perfusion and are of limited value in patients with chronic limb-threatening ischemia (CLTI). Near-infrared (NIR) fluorescence imaging using indocyanine green (ICG) has been used extensively in perfusion studies and is a possible modality for tissue perfusion measurement in patients with CLTI. In this prospective cohort study, ICG NIR fluorescence imaging was performed in patients with CLTI and control patients using the Quest Spectrum Platform^® (Middenmeer, The Netherlands). The time–intensity curves were analyzed using the Quest Research Framework. Fourteen parameters were extracted. Successful ICG NIR fluorescence imaging was performed in 19 patients with CLTI and in 16 control patients. The time to maximum intensity (seconds) was lower for CLTI patients (90.5 vs. 143.3, p = 0.002). For the inflow parameters, the maximum slope, the normalized maximum slope and the ingress rate were all significantly higher in the CLTI group. The inflow parameters observed in patients with CLTI were superior to the control group. Possible explanations for the increased inflow include damage to the regulatory mechanisms of the microcirculation, arterial stiffness, and transcapillary leakage.

Lower endothelium-dependent microvascular function in adult breast cancer patients receiving radiation therapy

Purpose

Cancer patients with a history of radiotherapy are at an increased risk of ischemic heart disease. Preclinical animal studies demonstrate markedly impaired acetylcholine (ACh)-mediated endothelium-dependent vasorelaxation within days to weeks post-irradiation, however, whether microvascular function is affected in the intact human circulation during cancer radiation therapy has yet to be determined.

Materials and methods

Using laser-Doppler flowmetry, microvascular endothelium-dependent and independent responses were evaluated through iontophoresis of acetylcholine (ACh) (part 1, n = 7) and sodium nitroprusside (SNP) (part 2, n = 8), respectively, in women currently receiving unilateral chest adjuvant radiation therapy for breast cancer. Measurements were performed at the site of radiation treatment and at a contralateral control, non-radiated site. Cutaneous vascular conductance (CVC) was calculated by normalizing for mean arterial pressure.

Results and Conculsions

In part 1, patients received an average radiation dose of 2104 ± 236 cGy. A significantly lower peak ACh-mediated endothelium-dependent vasodilation was observed within the radiated microvasculature when compared to non-radiated (radiated: 532 ± 167%, non-radiated 1029 ± 263%; P = 0.02). In part 2, the average radiation dose received was 2251 ± 196 cGy. Iontophoresis of SNP elicited a similar peak endothelium-independent vasodilator response in radiated and non-radiated tissue (radiated: 179 ± 58%, non-radiated: 310 ± 158; P = 0.2). The time to 50% of the peak response for ACh and SNP was similar between radiated and non-radiated microvasculature (P < 0.05). These data provide evidence of early endothelium-dependent microvascular dysfunction in cancer patients currently receiving chest radiation and provide the scientific premise for future work evaluating coronary endothelial function and vasomotor reactivity using more detailed and invasive procedures.

Microvascular Dysfunction in Peripheral Artery Disease: Is Heat Therapy a Viable Treatment?

Peripheral artery disease (PAD) is characterized by the development of atherosclerotic plaques in the lower-body conduit arteries. PAD is commonly accompanied by microvascular disease, which may result in poor wound healing, plantar ulcer development, and subsequent limb amputation. Understanding the mechanisms underlying the development of plantar ulcers is a critical step in the development of adequate treatment options for patients with PAD. Skin is classified into two major components: glabrous and non-glabrous. These skin types have unique microcirculation characteristics, making it important to differentiate between the two when investigating mechanisms for plantar ulcer development in PAD. There is evidence for a microcirculation compensatory mechanism in PAD. This is evident by the maintenance of basal microcirculation perfusion and capillary filling pressure despite a reduced pressure differential beyond an occlusion in non-critical limb ischemia PAD. The major mechanism for this compensatory system seems to be progressive vasodilation of the arterial network below an occlusion. Recently, heat therapies have emerged as novel treatment options for attenuating the progression of PAD. Heat therapies are capable of stimulating the cardiovascular system, which may lead to beneficial adaptations that may ultimately reduce fatigue during walking in PAD. Early work in this area has shown that full-body heating is capable of generating an acute cardiovascular response, similar to exercise, which has been suggested as the most efficient treatment modality and may generate adaptations with chronic exposure. Heat therapies may emerge as a conservative treatment option capable of attenuating the progression of PAD and ultimately impeding the development of plantar ulcers.

Cutaneous microcirculation in patients with peripheral arterial occlusive disease: Comparison of capillary blood circulation in the nail fold of finger and toe

In patients with peripheral arterial occlusive disease (PAOD) a restricted circulation in cutaneous microvessels has been reported. In this study the velocity of erythrocytes (very) in finger nailfold capillaries - a vascular area without upstream macroangiopathy - and also in toe nailfold capillaries - a post-stenotic area –was investigated using capillary microscopy in apparently healthy subjects and patients with PAOD. Already in finger nailfold capillaries very of patients with PAOD under resting conditions was significantly lower than in capillaries of healthy subjects. This was also true for the circulation in toe capillaries. In addition, the erythrocyte velocities under resting conditions in the toe capillaries were significantly lower than in the finger capillaries. Similar results were found for the duration and the maximum velocity of postocclusive hyperemia. It is concluded that the resting blood flow in the skin microcirculation is impaired in PAOD patients, both under resting conditions and during postocclusive hyperemia in finger as well in toe nailfold capillaries.

Determinants of Bone Material Strength and Cortical Porosity in Patients with Type 2 Diabetes Mellitus

CONTEXT

Reduced bone material strength index (BMSi) and increased cortical porosity (CtPo) have emerged as potentially contributing to fracture risk in type 2 diabetes mellitus (T2DM) patients.

OBJECTIVE

To determine whether BMSi or CtPo are related to other diabetic complications.

DESIGN

Cross-sectional observational study.

SETTING

Subjects recruited from a random sample of southeast Minnesota residents.

PARTICIPANTS

A total of 171 T2DM patients (mean age, 68.8 years) and 108 age-matched nondiabetic controls (mean age, 67.3 years).

MAIN MEASURES

Bone material strength index was measured using microindentation, skin advanced glycation end-products (AGEs) measured using autofluorescence, high-resolution peripheral quantitative computed tomography at the distal radius and tibia, assessment of diabetic microvascular complications including urine microalbuminuria, retinopathy, neuropathy, and vascular disease (ankle brachial index and transcutaneous oxygen tension [TcPO2]). All analyses were adjusted for age, sex, and body mass index.

RESULTS

Skin AGEs were negatively correlated with the BMSi in both T2DM (r = -0.30, P < 0.001) and control (r = -0.23, P = 0.020) subjects. In relating diabetic complications to CtPo, we found that T2DM patients with clinically significant peripheral vascular disease (TcPO2 ≤ 40 mm Hg) had higher (+21.0%, P = 0.031) CtPo at the distal tibia as compared to controls; in these subjects, CtPo was negatively correlated with TcPO2 at both the distal tibia (r = -0.39, P = 0.041) and radius (r = -0.41, P = 0.029).

CONCLUSIONS

Our findings demonstrate that bone material properties are related to AGE accumulation regardless of diabetes status, while CtPo in T2DM patients is linked to TcPO2, a measure of microvascular blood flow.

Effect of orthostasis on the regulation of skin blood flow in upper and lower extremities in human

OBJECTIVE

The research is aimed to investigate interactions between cardiovascular signals and to assess contributions of central and local mechanisms to skin blood flow regulation in upper and lower extremities at rest and under orthostasis.

METHODS

Heart rate variability, respiration, forearm, and foot skin blood flow were assessed at rest and during postural test in 25 healthy volunteers. Spectral analysis was performed. Phase synchronization degree of analyzed signals was determined by group phase wavelet coherence function.

RESULTS

Skin blood flow was lower on foot at rest and during postural test than on forearm. High-frequency component of heart rate variability was higher at ~0.3 Hz during postural test versus rest. Blood flow oscillation amplitudes on the foot were lower in frequency range including respiratory interval at rest than on forearm. Postural exposure increased amplitude of foot blood flow oscillations in respiratory interval and decreased amplitudes in cardiac interval versus rest. Orthostasis increased group wavelet phase coherence between foot blood flow and heart rate variability or respiration, as well as between forearm and foot blood flow at 0.3 Hz corresponding to respiration.

CONCLUSIONS

The contribution of central mechanisms associated with respiration to blood flow regulation increased in lower extremities during orthostasis.

Do Surgical Site Infections in Open Aortoiliac Surgery Differ Between Occlusive and Aneurysmal Arterial Disease?

Background:

Surgical site infections (SSI) are frequently seen after aortoiliac vascular surgery (2%-14%). Deep SSIs are associated with graft infection, sepsis, and mortality. This study evaluates the difference in incidence and nature of SSI following open aortoiliac surgery for aneurysmal disease compared to occlusive arterial disease.

Methods:

A retrospective cohort study was conducted, including all consecutive patients who underwent open aortoiliac vascular surgery between January 2005 and December 2016 in the Amphia Hospital, Breda, the Netherlands. Patients were grouped by disease type, either aneurysmal or occlusive arterial disease. Data were gathered, including patient characteristics, potential risk factors, and development of SSI. Surgical site infections were defined in accordance with the criteria of the Centers for Disease Control.

Results:

Between January 2005 and December 2016, a total of 756 patients underwent open aortoiliac surgery of which 517 had aortoiliac aneurysms and 225 had aortoiliac occlusive disease. The group with occlusive disease was younger, predominantly male, and had more smokers. After exclusion of 228 patients undergoing acute surgery, the SSI rate after elective surgery was 6.2%, with 10 of 301 SSIs in the aneurysmal group (3.0%) and 22 of 213 SSIs in the group with occlusive disease (10.3%, P < .001). Also, infection-related readmission and reintervention were higher after occlusive surgery, 6.6% versus 0.9% ( P < .001) and 4.2% versus 0.9% ( P = .003), respectively. Staphylococcus aureus was found as the most common pathogen, causing 64% of SSI in occlusive disease versus 10% in aneurysmal disease ( P = .005). Logistic regression showed occlusive arterial disease and chronic renal disease were associated with SSI.

Conclusion:

Our study presents evidence for a higher rate of SSI in patients with aortoiliac occlusive disease compared to aortoiliac aneurysmal disease, in part due to inherent use of inguinal incision in patients with occlusive disease. All precautions to prevent SSI should be taken in patients undergoing vascular surgery for arterial occlusive disease.

Micro-Lightguide Spectrophotometry (O2C) for Lower Limb Perfusion: Effects of Exercise Walking in Claudicants

Background  Exercise walking has improved walking capacity in patients with intermittent claudication without affecting the macrocirculation reflected in ankle pressures. We wanted to investigate microcirculation in the skin related to exercise walking by using Micro-Lightguide Spectrophotometry (O2C). Materials and Methods  Twenty-eight patients with intermittent claudication-bilateral in 17-were included in a 12 weeks of structured home-based exercise program. The pain-free and maximal walking distances were determined on a treadmill. Saturation and flow, monitored by O2C, were examined immediately before and after the treadmill test. O2C examination took place before as well as after completion of the exercise program. Ankle-brachial index was obtained before treadmill testing. Results  As expected, walking performance improved significantly without affecting ankle pressures. Neither oxygen saturation nor flow, assessed at 2 mm depth, was affected following a 12 weeks of exercise program. We observed a significant decrease in oxygen saturation and flow upon treadmill testing in the both limbs in patients with bilateral peripheral arterial disease (PAD). In contrast, the treadmill test elicited no changes in the opposite and asymptomatic limb in patients with only unilateral PAD. Conclusion  The findings suggest that O2C may be used to study microcirculatory changes. However, it is best suited for the study of phenomena resulting in major changes as it eliminates some inherent variability.

Continuous monitoring of interstitial tissue oxygen using subcutaneous oxygen microsensors: In vivo characterization in healthy volunteers

Measurements of regional tissue oxygen serve as a proxy to monitor local perfusion and have the potential to guide therapeutic decisions in multiple clinical disciplines. Transcutaneous oximetry (tcpO2) is a commercially available noninvasive technique that uses an electrode to warm underlying skin tissue and measure the resulting oxygen tension at the skin surface. A novel approach is to directly measure interstitial tissue oxygen using subcutaneous oxygen microsensors composed of a biocompatible hydrogel carrier platform with embedded oxygen sensing molecules. After initial injection of the hydrogel into subcutaneous tissue, noninvasive optical measurements of phosphorescence-based emissions at the skin surface are used to sense oxygen in the subcutaneous interstitial space. The object of the present study was to characterize the in vivo performance of subcutaneous microsensors and compare with transcutaneous oximetry (tcpO2). Vascular occlusion tests were performed on the arms of 7 healthy volunteers, with repeated tests occurring 1 to 10 weeks after sensor injection, yielding 95 total tests for analysis. Comparative analysis characterized the response of both devices to decreases in tissue oxygen during occlusion and to increases in tissue oxygen following release of the occlusion. Results indicated: (I) time traces returned by microsensors and tcpO2 were highly correlated, with the median (interquartile range) correlation coefficient of r = 0.93 (0.10); (II) both microsensors and tcpO2 sensed a statistically significant decrease in normalized oxygen during occlusion (p < 0.001 for each device); (III) microsensors detected faster rates change (p < 0.001) and detected overshoot during recovery more frequently (38% vs. 4% of tests); (IV) inter-measurement analysis showed no correlation of baseline values between microsensors and tcpO2 (r = 0.03), but comparison of integrated oxygen dynamics showed similar variation in the normalized response to occlusion between devices (p = 0.06), (V) intra-measurement analysis revealed that microsensors detect greater physiological fluctuations than tcpO2 (p < 0.001) and may provide enhanced sensitivity to processes such as vasomotion. Additionally, the functional response of microsensors was not significantly different across time groupings (per month) post-injection (p = 0.61). Although the compared devices have differences in the mechanisms used to sense oxygen, these findings demonstrate that subcutaneous oxygen microsensors measure changes in interstitial tissue oxygen in human subjects in vivo.

Current methods for the assessment of skin microcirculation: Part 1

Microcirculation accounts for about 99% of blood vessels in adults and mediates between the arterial and venous parts of the cardiovascular system, both structurally and functionally. Skin microcirculation consists of two vascular plexuses: superficial and deep. Microcirculation includes vessels with a diameter of less than 150 μm, i.e. arteries, small veins, lymphatic vessels and arteriovenous anastomoses, which build the microcirculation unit. Skin microcirculation may be affected both in systemic pathologies and specific skin disorders. Several non-invasive techniques are available to assess the skin microcirculation. The clinical value is recognised for capillaroscopy and videocapillaroscopy, laser Doppler flowmetry thermography and transcutaneous oxygen measurement. The list of methods that may be used in clinical research also includes: photoplethysmography, orthogonal spectral polarization, near infrared spectroscopy and tissue reflectance spectrophotometry and optical coherence tomography.

Perfusion of the skin's microcirculation after cold-water immersion (10°C) and partial-body cryotherapy (-135°C)

Background

Investigations of the perfusion of the skin's microcirculation with laser speckle contrast imaging (LSCI) after cold treatments are rare. Therefore, the aim of this study was to compare the effects between cold‐water immersion (CWI) conduction and partial‐body cryotherapy (PBC) convection on perfusion of the microcirculation and skin temperature on the thigh.

Materials and Methods

Twenty healthy males were randomly allocated to CWI (10°C for 10 minutes) or PBC (−60°C for 30 seconds, −135°C for 2 minutes). Perfusion and skin temperature measurements were conducted on the anterior thigh region up to 60 minutes post‐treatment.

Results

Cold‐water immersion decreased perfusion of the microcirculation significantly compared to baseline values between 10 minutes (P = 0.003) and 30 minutes (P = 0.01) post‐treatment. PBC increased perfusion of the microcirculation and decreased skin temperature only at the first measurement interval (0 minute, both P = 0.01) post‐treatment. Additionally, local skin temperature was significantly decreased compared to baseline values only after CWI up to 30 minutes (P = 0.04) post‐treatment.

Conclusion

Cold‐water immersion reduced local skin microcirculation and skin temperature while PBC only slightly increased the perfusion of the microcirculation immediately after the treatment. For cooling purposes, the conduction method seems superior compared to the convection method, assessed with a LSCI device.

Lower cutaneous microvascular reactivity in adult cancer patients receiving chemotherapy

Cancer patients with a history of anticancer chemotherapy are at an increased cardiovascular disease risk compared with cancer-free populations. Therefore, we tested the hypothesis that cancer patients receiving adjuvant chemotherapy would have a lower cutaneous microvascular reactivity and lower endothelium-dependent flow-mediated dilation (FMD) of the brachial artery compared with matched cancer-free control subjects. To test this hypothesis, we performed a case control study with seven cancer patients receiving adjuvant chemotherapy and seven matched healthy reference control subjects. Red blood cell flux was measured as an index of cutaneous blood flow via laser Doppler flowmetry. Acetylcholine (ACh)-mediated vasodilation was determined by iontophoresis. Data were expressed as percent increase in cutaneous vascular conductance. Endothelium-dependent FMD of the brachial artery via ultrasonography was determined as an index of macrovessel endothelial function. Cutaneous microvascular reactivity was attenuated in cancer patients compared with control subjects [cancer: 959.9 ± 187.3%, control: 1,556.8 ± 222.2%; P = 0.03, effect size (ES) = 1.1]. Additionally, cancer patients demonstrated a significantly lower area under the curve response to ACh iontophoresis compared with healthy control subjects. Brachial artery FMD was also significantly lower in cancer patients compared with control subjects (cancer: 2.2 ± 0.6%, control: 6.6 ± 1.4%; P = 0.006, ES = 1.6), which was significantly associated with measurements of microvascular reactivity. These findings suggest that decreases in vascular reactivity can occur during cancer chemotherapy, which may have implications for the long-term risk of cardiovascular disease morbidity and mortality. NEW & NOTEWORTHY Cancer survivors treated with chemotherapy experience an increased risk of cardiovascular events, linked to both cardiac and vascular toxicity. The major finding of this study is that microvascular reactivity and macrovascular endothelium-dependent flow-mediated dilation are lower in cancer patients currently receiving adjuvant chemotherapy compared with healthy counterparts.

The response of peripheral microcirculation to gravity-induced changes

BACKGROUND

The peripheral microcirculation supplies fresh blood to the small blood vessels, providing oxygen and nutrients to the tissues, removing waste, and maintaining normal homeostatic conditions. The goal of this study was to characterize the response of the peripheral microcirculation, in terms of blood flow and tissue oxygenation variables, to gravity-induced changes.

METHODS

The study included 20 healthy volunteers and the experiment involved monitoring central and peripheral variables with the right hand positioned at different heights. These positions correspond to various gravitational levels. Peripheral perfusion and oxygenation were monitored using a laser Doppler flowmeter, photoplethysmograph, and transcutaneous oxygen tension monitor. Local blood pressure and respiration rate were also measured.

FINDINGS

At the heart level, tissue oxygenation displayed a nadir, while capillary flow displayed a peak. Similar but weaker changes were observed at the control hand. In contrast, the photoplethysmograph's amplitude strongly decreased upon reducing the arm position below heart level. Both systolic and diastolic pressures decreased linearly between the highest to lowest arm position.

INTERPRETATION

The results may reflect peripheral compensation mechanisms, as well as an interaction between the central and peripheral cardiovascular systems, in response to local changes in blood pressure. The observed dependence of the oxygenation pattern on height could lead to important new insights for the diagnosis and treatment of problems in the regulation of tissue perfusion.

The correlation between transcutaneous oxygen tension and microvascular complications in type 2 diabetic patients

AIMS

This study aimed to assess whether transcutaneous oxygen tension (TcPO₂) was associated with the presence of microvascular complications in type 2 diabetic (T2D) patients and whether TcPO₂ could act as an independent risk factor for predicting the occurrence of microvascular events in these patients.

METHODS

We recruited 436 patients with T2D. Based on the presence of diabetic kidney disease, diabetic retinopathy, and/or diabetic peripheral neuropathy, the patients were divided into groups with and without microvascular complications. The differences between these 2 groups were examined using the chi-square test and the t test. The influencing factors of diabetic microangiopathy were studied using a logistic regression analysis.

RESULTS

The results showed that sex, diabetes duration, smoking history, TcPO₂, and HbA1c were independent risk factors for the occurrence of diabetic microvascular events (P<0.05). In particular, the risk of developing microvascular complications was 10.16 times higher in patients with low TcPO₂ than that in those with high TcPO₂ (OR=10.157, 95% CI: 4.602-22.418).

CONCLUSION

This study showed that TcPO₂ was significantly negatively associated with the occurrence of microvascular events in type 2 diabetic patients and that TcPO₂ may be an independent risk factor for predicting the occurrence of microvascular complications in these patients. These results suggest that for type 2 diabetes mellitus with clinically reduced TcPO₂, we should pay close attention to the occurrence of microvascular complications and engage in early prevention.

Clinical impact of exercise in patients with peripheral arterial disease

Increasing prevalence, high morbidity and mortality, and decreased health-related quality of life are hallmarks of peripheral arterial disease. About one-third of peripheral arterial disease patients have intermittent claudication with deleterious effects on everyday activities, such as walking. Exercise training improves peripheral arterial disease symptoms and is recommended as first line therapy for peripheral arterial disease. This review examines the effects of exercise training beyond improvements in walking distance, namely on vascular function, parameters of inflammation, activated hemostasis and oxidative stress, and quality of life. Exercise training not only increases walking distance and physiologic parameters in patients with peripheral arterial disease, but also improves the cardiovascular risk profile by helping patients achieve better control of hypertension, hyperglycemia, obesity and dyslipidemia, thus further reducing cardiovascular risk and the prevalence of coexistent atherosclerotic diseases. American guidelines suggest supervised exercise training, performed for a minimum of 30-45 min, at least three times per week, for at least 12 weeks. Walking is the most studied exercise modality and its efficacy in improving cardiovascular parameters in patients with peripheral arterial disease has been extensively proven. As studies have shown that supervised exercise training improves walking performance, cardiovascular parameters and quality of life in patients with peripheral arterial disease, it should be encouraged and more often prescribed.

Critical Limb Ischemia: An Expert Statement

Critical limb ischemia (CLI), the most advanced form of peripheral artery disease, is associated with significant morbidity, mortality, and health care resource utilization. It is also associated with physical, as well as psychosocial, consequences such as amputation and depression. Importantly, after a major amputation, patients are at heightened risk of amputation on the contralateral leg. However, despite the technological advances to manage CLI with minimally invasive technologies, this condition often remains untreated, with significant disparities in revascularization and amputation rates according to race, socioeconomic status, and geographic region. Care remains disparate across medical specialties in this rapidly evolving field. Many challenges persist, including appropriate reimbursement for treating complex patients with difficult anatomy. This paper provides a comprehensive summary that includes diagnostic assessment and analysis, endovascular versus open surgical treatment, regenerative and adjunctive therapies, and other important aspects of CLI.

The effect of exercise training on cutaneous microvascular reactivity: A systematic review and meta-analysis

OBJECTIVES

This study aimed to review the efficacy of exercise training for improving cutaneous microvascular reactivity in response to local stimulus in human adults.

DESIGN

Systematic review with meta-analysis.

METHODS

A systematic search of Medline, Cinahl, AMED, Web of Science, Scopus, and Embase was conducted up to June 2015. Included studies were controlled trials assessing the effect of an exercise training intervention on cutaneous microvascular reactivity as instigated by local stimulus such as local heating, iontophoresis and post-occlusive reactive hyperaemia. Studies where the control was only measured at baseline or which included participants with vasospastic disorders were excluded. Two authors independently reviewed and selected relevant controlled trials and extracted data. Quality was assessed using the Downs and Black checklist.

RESULTS

Seven trials were included, with six showing a benefit of exercise training but only two reaching statistical significance with effect size ranging from -0.14 to 1.03. The meta-analysis revealed that aerobic exercise had a moderate statistically significant effect on improving cutaneous microvascular reactivity (effect size (ES)=0.43, 95% CI: 0.08-0.78, p=0.015).

CONCLUSIONS

Individual studies employing an exercise training intervention have tended to have small sample sizes and hence lacked sufficient power to detect clinically meaningful benefits to cutaneous microvascular reactivity. Pooled analysis revealed a clear benefit of exercise training on improving cutaneous microvascular reactivity in older and previously inactive adult cohorts. Exercise training may provide a cost-effective option for improving cutaneous microvascular reactivity in adults and may be of benefit to those with cardiovascular disease and metabolic disorders such as diabetes.

[Periungueal capillaroscopy: an easy and reliable method to evaluate all microcirculation diseases]

Periungueal capillaroscopy is a simple and reliable non-invasive technique allowing evaluation of cutaneous microcirculation. It was promoted for decades in patients with Raynaud's phenomenon in order to differentiate between the benign primary Raynaud's phenomenon and the secondary form in connective tissue diseases, especially systemic sclerosis. Nevertheless, the value of this procedure has also been shown in numerous pathologies such as diabetes or cardiovascular diseases. This literature review points to the versatility of this useful exam and its results in a large spectrum of diseases with microvascular involvement.

Regarding the quantification of peripheral microcirculation--Comparing responses evoked in the in vivo human lower limb by postural changes, suprasystolic occlusion and oxygen breathing

The human skin is an interesting model to explore microcirculation, particularly if using noninvasive technologies such as LDF (Laser Doppler Flowmetry) and tc (transcutaneous) gasimetry and methods as near as possible from the normal physiological state. In this study, we combined those technologies with three classical approaches--leg raising from supine, suprasystolic occlusion (in the ankle), and normobaric oxygen breathing to explore distal peripheral circulation in the foot. These methods are often cited, but a comparative assessment has not been done. The goal of this study was to identify relevant flow related descriptors, method-related advantages and pitfalls, and eventually, to find the best experimental approach. Volunteers (both genders, 22.1 ± 3.7 years old) were subjected to these methods and variables registered during basal, challenge and stabilization phases. Descriptive and comparative statistics were obtained, adopting a 95% confidence level. All flow-related quantitative descriptors potentially useful for the analysis were identified and compared. As expected, male patients consistently showed higher LDF levels and transepidermal water loss (TEWL) and lower tcpO2 values. However, lower results were recorded in the supine position, suggesting a postural dependence. Both leg raising and suprasystolic occlusion produced a hyperemic response after provocation, although different in magnitude, significantly reducing LDF and tcpO2 during provocation. The oxygen breathing method provided the most patient-friendly protocol, consistently reducing LDF (potentially by the inhibition of production of local vasodilators). TEWL increased during the provocation phase in all protocols, although not significantly. Baseline tcpO2 was found to correlate positively with the peak tcpO2 during oxygen breathing and basal LDF with peak flow during leg raising and suprasystolic occlusion. No statistical correlation between TEWL and LDF could be demonstrated under the current experimental conditions. We conclude that although equally useful considering the purpose, these methods involve very different practicalities and do not provide the same information. Also noteworthy, LDF is a highly sensitive indicator that could be further explored to look deeper into blood flow regulating mechanisms.

In vivo blood flow imaging of inflammatory human skin induced by tape stripping using optical microangiography

Vasculature response is a hallmark for most inflammatory skin disorders. Tape stripping on human skin causes a minor inflammation which leads to changes in microvasculature. In this study, optical microangiography (OMAG), noninvasive volumetric microvasculature in vivo imaging method, has been used to track the vascular responses after tape stripping. Vessel density has been quantified and used to correlate with the degree of skin irritation. The proved capability of OMAG technique in visualizing the microvasculature network under inflamed skin condition can play an important role in clinical trials of treatment and diagnosis of inflammatory skin disorders.

Assessment of speed distribution of red blood cells in the microvascular network in healthy volunteers and type 1 diabetes using laser Doppler spectra decomposition

We applied a recently reported method of decomposition of laser Doppler power density spectra for in vivo monitoring of speed distributions of red blood cells (RBCs) in the microvascular network. The spectrum decomposition technique allows us to derive the distribution of RBC speed (in absolute units (mm s(-1))) versus RBC concentration (in arbitrary units). We carried out postocclusive reactive hyperaemia (PORH) test in 15 healthy volunteers and 21 diabetic patients in which the duration of type 1 diabetes was longer than 10 years. Measurements were carried out simultaneously with the use of a typical laser Doppler commercial instrument and speed resolved laser Doppler instrument utilizing the new technique based on decomposition of the laser Doppler spectra. We show that for the classical laser Doppler instrument, none of the PORH parameters revealed a statistical significance of difference between the groups analyzed. In contrast, the RBC speed distributions obtained from laser Doppler spectra during rest in the control group and type 1 diabetes are statistically significant. This result suggests that speed distribution measurements in the rest state (without any kind of stimulation test) allows for the assessment of microcirculation disorders. Measurements carried out in healthy subjects show that the first moment of speed distributions (mean speed of the distributions) is 2.32 ± 0.54 mm s(-1) and 2.57 ± 0.41 mm s(-1) for optodes located on the toe and finger of the hand, respectively. Respective values in type 1 diabetes were higher: 3.00 ± 0.36 mm s(-1) and 3.10 ± 0.48 mm s(-1).

HIF isoforms in the skin differentially regulate systemic arterial pressure

Vascular flow through tissues is regulated via a number of homeostatic mechanisms. Localized control of tissue blood flow, or autoregulation, is a key factor in regulating tissue perfusion and oxygenation. We show here that the net balance between two hypoxia-inducible factor (HIF) transcription factor isoforms, HIF-1α and HIF-2α, is an essential mechanism regulating both local and systemic blood flow in the skin of mice. We also show that balance of HIF isoforms in keratinocyte-specific mutant mice affects thermal adaptation, exercise capacity, and systemic arterial pressure. The two primary HIF isoforms achieve these effects in opposing ways that are associated with HIF isoform regulation of nitric oxide production. We also show that a correlation exists between altered levels of HIF isoforms in the skin and the degree of idiopathic hypertension in human subjects. Thus, the balance between HIF-1α and HIF-2α expression in keratinocytes is a control element of both tissue perfusion and systemic arterial pressure, with potential implications in human hypertension.

Impact of diabetes and peripheral arterial occlusive disease on the functional microcirculation at the plantar foot

BACKGROUND

Plastic and reconstructive surgeons are commonly faced with chronic ulcerations and consecutive wound infections of the feet as complications in patients with diabetes and/or peripheral arterial occlusive disease (PAOD). Microcirculatory changes seem to play an important role. However, the evaluation of functional changes in the soft tissue microcirculation at the plantar foot using combined Laser-Doppler and Photospectrometry System has not yet been performed in patients with DM or PAOD.

METHODS

A prospective, controlled cohort study was designed consisting of a total of 107 subjects allocated to 1 of 3 groups-group A: healthy subjects (57% males, 63.3 y); group B: patients with diabetes mellitus (DM) (53% males, 59.4 y); and group C: patients with PAOD (81% males, 66.1 y). Microcirculatory data were assessed using a combined Laser-Doppler and Photospectrometry System.

RESULTS

Global cutaneous oxygen saturation microcirculation at the plantar foot of healthy individuals was 8.4% higher than in patients with DM and 8.1% higher than in patients with PAOD (both P = 0.033). Patients with diabetes did not show significant differences in global cutaneous blood flow when compared with either healthy subjects or patients suffering from PAOD.

CONCLUSIONS

Functional microcirculation at the plantar foot differs between healthy subjects and patients suffering from diabetes or PAOD of the same age. Patients with either diabetes or PAOD demonstrate deteriorated cutaneous oxygen saturation with equivalent blood perfusion at the plantar foot. More clinical studies have to be conducted to evaluate therapeutical methods that might ameliorate cutaneous oxygen saturation within diabetic foot disease and PAOD.

Recent progress in tissue optical clearing

Tissue optical clearing technique provides a prospective solution for the application of advanced optical methods in life sciences. This paper gives a review of recent developments in tissue optical clearing techniques. The physical, molecular and physiological mechanisms of tissue optical clearing are overviewed and discussed. Various methods for enhancing penetration of optical-clearing agents into tissue, such as physical methods, chemical-penetration enhancers and combination of physical and chemical methods are introduced. Combining the tissue optical clearing technique with advanced microscopy image or labeling technique, applications for 3D microstructure of whole tissues such as brain and central nervous system with unprecedented resolution are demonstrated. Moreover, the difference in diffusion and/or clearing ability of selected agents in healthy versus pathological tissues can provide a highly sensitive indicator of the tissue health/pathology condition. Finally, recent advances in optical clearing of soft or hard tissue for in vivo imaging and phototherapy are introduced. [Formula: see text].

Transcutaneous oxygen tension as a potential predictor of cardiovascular events in type 2 diabetes: comparison with ankle-brachial index

OBJECTIVE

Transcutaneous oxygen tension (TcPO2) measures tissue perfusion and is important in the management of peripheral artery disease (PAD). Ankle brachial index (ABI) is used for the diagnosis of PAD and represents a predictor of major adverse cardiovascular events (MACE), even if in diabetes its diagnostic and predictive value seems to be reduced. No study has evaluated TcPO2 as a predictor of cardiovascular events. Aim of this longitudinal study was to assess whether TcPO2 is better than ABI at predicting MACE in type 2 diabetic patients.

RESEARCH DESIGN AND METHODS

Among 361 consecutive patients with apparently uncomplicated diabetes, 67 MACE occurred during a follow-up period of 45.8 ± 23.2 months.

RESULTS

The percentage of both subjects with low ABI (≤ 0.9) and subjects with low TcPO2 (≤ 46 mmHg as measured by a receiver operating characteristic curve) was significantly (<0.001) greater among patients with than among those without MACEs (ABI 64.2 vs. 40.8; TcPO2 58.2 vs. 34%). The Kaplan-Meier method showed that both low ABI (Mantel log-rank test, 4.087; P = 0.043) and low TcPO2 (Mantel log-rank test, 33.748; P > 0.0001) were associated with a higher rate of MACEs. Cox regression analysis showed that low TcPO2 (hazard ratio 1.78 [95% CI 1.44-2.23]; P < 0.001) was a significant predictor of MACE, while ABI did not enter the model.

CONCLUSIONS

This longitudinal study showed that TcPO2 may be a potential predictor of MACE among patients with uncomplicated type 2 diabetes and that its predictive value seems to be greater than that of ABI.

Enhanced spectral analysis of blood flow during post-occlusive reactive hyperaemia test in different tissue depths

The objective of this study was to investigate the impairment of microcirculation in schizophrenic patients by means of spectral analysis of blood flow signals and to determine if microcirculation is unequally altered in different tissue depths. Furthermore, the impact of gender and age on the spectral parameters of the Laser Doppler Flowmetry (LDF) signal in healthy and diseased microcirculation are to be analysed. The segmented spectral analysis (SSA) algorithm was applied to LDF signals of a provoked post-ischemic stage and compared to the traditional total spectral analysis, hypothesizing that SSA reveals more detailed information on the dynamic behaviour of the blood flow. 15 healthy subjects (CON, mean age 32.4 years) and 15 patients (PAT, mean age 33.0 years) were enrolled. Spectral analysis was performed on two LDF signals at a depth of 2mm and 6-8mm. Features in five frequency subintervals were determined. Our results indicate that microcirculation is strongly impaired in patients. SSA of blood flow revealed differences between CON and PAT in all three frequency intervals referring to local vasomotion (endothelial p=0.03; sympathetic p=0.02, myogenic p=0.03) as well as the respiratory (p=0.02) and cardiac (p=0.006) bands in the deeper tissue. In contrast, in the near-surface tissue only the endothelial (p=0.006) and cardiac (p=0.006) components were altered. Furthermore, SSA determined a gender- and age dependency regarding blood flow. In conclusion, we could demonstrate that microcirculation in schizophrenic patients is significantly impaired, depending on its location in the near-surface skin or in the superficial muscle tissue. These alterations of microcirculation are more pronounced in the deeper tissue depth of about 6-8mm and are influenced by gender and age.

'Go with the flow ': a review of methods and advancements in blood flow imaging

Physics has delivered extraordinary developments in almost every facet of modern life. From the humble thermometer and stethoscope to X-Ray, CT, MRI, ultrasound, PET and radiotherapy, our health has been transformed by these advances yielding both morphological and functional metrics. Recently high resolution label-free imaging of the microcirculation at clinically relevant depths has become available in the research domain. In this paper, we present a comprehensive review on current imaging techniques, state-of-the-art advancements and applications, and general perspectives on the prospects for these modalities in the clinical realm.

Cutaneous microvascular dysfunction correlates with serum LDL and sLOX-1 receptor concentrations

The human cutaneous circulation is an accessible and representative regional circulation for investigating mechanisms of microvascular dysfunction, a systemic disease process occurring early in the pathogenesis of atherosclerosis. Elevated concentrations of low-density lipoproteins ([LDL]) are highly atherogenic and independently associated with the severity of coronary atherosclerosis through their actions on the lectin-like oxidized LDL receptors (LOX-1). We hypothesized that cutaneous microvascular dysfunction, as measured by a decrement in endothelial nitric oxide- (NO-) dependent vasodilation during local heating, would be correlated with serum [LDL], oxidized [LDL], and soluble LOX-1 receptors [sLOX-1]. Intradermal microdialysis fibers were placed in the skin of 53 otherwise healthy men and women (aged 52±8 years) whose serum [LDL] ranged from 72 to 233 mg/dL. Skin blood flow was measured by laser Doppler flowmetry over a local forearm skin site as it was heated (42°C) to induce sustained local vasodilation. After flux plateaued, L-NAME was infused to block endothelial NO synthase in order to determine the NO-dependent portion of the vasodilatory response. Data were normalized to maximal cutaneous vascular conductance (CVC). NO-dependent vasodilation was reduced as a linear function of [LDL] (R(2)=0.303, p<0.001), oxidized [LDL] (R(2)=0.214, p<0.001), and [sLOX-1] (R(2)=0.259, p=0.026) but was unrelated to high-density lipoprotein (HDL) concentration (R(2)=0.003, p=0.68). Hypercholesterolemia-induced microvascular dysfunction is related to various LDL markers and involves a reduction in NO-dependent vasodilation that appears to be a progressive process measurable in the skin microcirculation.

Dietary sodium loading impairs microvascular function independent of blood pressure in humans: role of oxidative stress

Animal studies have reported dietary salt-induced reductions in vascular function independent of increases in blood pressure (BP). The purpose of this study was to determine if short-term dietary sodium loading impairs cutaneous microvascular function in normotensive adults with salt resistance. Following a control run-in diet, 12 normotensive adults (31 ± 2 years) were randomized to a 7 day low-sodium (LS; 20 mmol day(-1)) and 7 day high-sodium (HS; 350 mmol day(-1)) diet (controlled feeding study). Salt resistance, defined as a 5 mmHg change in 24 h mean BP determined while on the LS and HS diets, was confirmed in all subjects undergoing study (LS: 84 ± 1 mmHg vs. HS: 85 ± 2 mmHg; P > 0.05). On the last day of each diet, subjects were instrumented with two microdialysis fibres for the local delivery of Ringer solution and 20 mm ascorbic acid (AA). Laser Doppler flowmetry was used to measure red blood cell flux during local heating-induced vasodilatation (42°C). After the established plateau, 10 mm l-NAME was perfused to quantify NO-dependent vasodilatation. All data were expressed as a percentage of maximal cutaneous vascular conductance (CVC) at each site (28 mm sodium nitroprusside; 43°C). Sodium excretion increased during the HS diet (P < 0.05). The plateau % CVCmax was reduced during HS (LS: 93 ± 1 % CVCmax vs. HS: 80 ± 2 % CVCmax; P < 0.05). During the HS diet, AA improved the plateau % CVCmax (Ringer: 80 ± 2 % CVCmax vs. AA: 89 ± 3 % CVCmax; P < 0.05) and restored the NO contribution (Ringer: 44 ± 3 % CVCmax vs. AA: 59 ± 6 % CVCmax; P < 0.05). These data demonstrate that dietary sodium loading impairs cutaneous microvascular function independent of BP in normotensive adults and suggest a role for oxidative stress.

Dynamic contrast-enhanced ultrasound for assessment of skeletal muscle microcirculation in peripheral arterial disease

OBJECTIVE

: This feasibility study was performed to assess whether dynamic contrast-enhanced ultrasound (CEUS) and transient arterial occlusion are able to detect alterations in the microvascular perfusion and arterial perfusion reserve in patients suffering from peripheral arterial disease (PAD) in comparison with healthy volunteers.

MATERIALS AND METHODS

: Twenty patients with PAD, Rutherford classification grade I, category III (mean age, 64 years; mean height, 173 cm; mean weight, 81.8 kg), and 20 volunteers (mean age, 50 years; mean height, 174 cm; mean weight, 77.8 kg) participated in the study. Low-mechanical index CEUS (7 MHz; MI, 0.28) was performed to the dominant lower leg after start of a continuous automatic intravenous injection of 4.8 mL suspension with microbubbles containing sulfur hexafluoride (SonoVue) within 5 minutes. Perfusion of the calf muscle was monitored by CEUS before, during, and after release of arterial occlusion at the thigh level lasting for 60 seconds. Several parameters, especially the time to maximum enhancement after release of occlusion (tmax), the maximum enhancement after release of occlusion (maxenh), the total vascular response after release of occlusion (AUCpost), and the resulting slope (m2) to maximum enhancement were calculated.

RESULTS

: After release of the occlusion, a significantly delayed increase of the CEUS signal to maxenh was observed in the patients with PAD (32 ± 17 seconds) compared with volunteers (17 ± 8 seconds, P = 0.0009). maxenh was 66.5 ± 36.6 (∼mL) in PAD versus 135.6 ± 75.1 (∼mL) in volunteers (P = 0.0016). AUCpost was 3016.5 ± 1825.8 (∼mL·s) in PAD versus 5906.4 ± 3173.1 (∼mL·s) in volunteers (P = 0.0013), and m2 was significantly lower in PAD (3.8 ± 5.2 vs. 14.8 ± 9.7 [∼mL/s], P = 0.0001).

CONCLUSIONS

: Microvascular perfusion deficits and reduced arterial perfusion reserve in patients with PAD are clearly detectable with dynamic CEUS after transient arterial occlusion.

Transcutaneous oxymetry as predictive test of peripheral vascular revascularization in haemodialysis population

BACKGROUND

Peripheral arterial disease (PAD) occurs frequently among haemodialysis patients but it is underestimated. Vascular treatment and amputations are more frequent in end stage renal disease (ESRD) population compared to the general population possibly because of a diagnosis of PAD delayed. Transcutaneous oxymetry (TcPO2) is commonly used in vascular medicine to reflect local arterial blood flow and skin oxygenation.The aim of this study was to assess the accuracy of the TcPO2 measurements to screen PAD and to predict vascular outcomes in haemodialysis population.

METHODS

In a 1-year prospective study, the value of TcPO2 was assessed in a cohort of 48 patients when starting haemodialysis.

RESULTS

Twenty one patients had at least one vascular stenosis (42%) on Doppler examination and were considered as affected by PAD. At inclusion a pathologic resting TcPO2 (<40mmHg) was found in 13 patients (29%). A severe ischemia (TcPO2 <30mmHg) was noted in 8 patients (16.7%) and a critical limb ischemia (TcPO2 <10mmHg) in 3 patients.(6%). Eleven (25.5%) and 6 patients (15%) had a TcPO2 <40mmHg at 6 and 12 months respectively. During the follow-up, death was seven times more frequent in patients with abnormal TcPO2 at T0 compared to patients with normal TcPO2 (38% vs 5.7%; p = 0.04). Revascularization (n = 6) or amputation (n = 5) were required for 5 patients. TcPO2 was pathologic in all patients and legs requiring a vascular treatment. The sensitivity, specificity, positive predictive value and negative predictive value were 100%, 85.2%, 38% and 100% respectively.

CONCLUSIONS

This study confirms the underestimated PAD diagnosis and the severity of PAD in haemodialysis population. A TcPO2 less than 40mmHg at the onset of the haemodialysis could identify patients at high risk of death and patients requiring vascular treatment. Moreover, since haemodialysis seems to be an accelerating factor of atherosclerosis, TcPO2 might be perform as a complement to traditional vascular explorations to assess the distal vascular conditions of limbs of haemodialysis patients.

Acute localized administration of tetrahydrobiopterin and chronic systemic atorvastatin treatment restore cutaneous microvascular function in hypercholesterolaemic humans

Elevated oxidized low-density lipoproteins (LDL) are associated with vascular dysfunction in the cutaneous microvasculature, induced in part by upregulated arginase activity and increased globalized oxidant stress. Since tetrahydrobiopterin (BH(4)) is an essential cofactor for endothelial nitric oxide synthase (NOS3), decreased bioavailability of the substrate l-arginine and/or BH(4) may contribute to decreased NO production with hypercholesterolaemia. We hypothesized that (1) localized administration of BH(4) would augment NO-dependent vasodilatation in hypercholesterolaemic human skin, which would be further increased when combined with arginase inhibition and (2) the improvement induced by localized BH(4) would be attenuated after a 3 month oral atorvastatin intervention (10 mg). Four microdialysis fibres were placed in the skin of nine normocholesterolaemic (NC: LDL = 95 ± 4 mg dl(-1)) and nine hypercholesterolaemic (HC: LDL = 177 ± 6 mg dl(-1)) men and women before and after 3 months of systemic atorvastatin. Sites served as control, NOS inhibited, BH(4), and arginase inhibited + BH(4) (combo). Skin blood flow was measured while local skin heating (42°C) induced NO-dependent vasodilatation. After the established plateau l-NAME was perfused in all sites to quantify NO-dependent vasodilatation (NO). Data were normalized to maximum cutaneous vascular conductance (CVC). Vasodilatation at the plateau and NO-dependent vasodilatation were reduced in HC subjects (plateau HC: 70 ± 5% CVC(max) vs. NC: 95 ± 2% CVC(max); NO HC: 45 ± 5% CVC(max) vs. NC: 64 ± 5% CVC(max); both P < 0.001). Localized BH(4) alone or combo augmented the plateau (BH(4): 93 ± 3% CVC(max); combo 89 ± 3% CVC(max), both P < 0.001) and NO-dependent vasodilatation in HC (BH(4): 74 ± 3% CVC(max); combo 76 ± 3% CVC(max), both P < 0.001), but there was no effect in NC subjects (plateau BH(4): 90 ± 2% CVC(max); combo 95 ± 3% CVC(max); NO-dependent vasodilatation BH(4): 68 ± 3% CVC(max); combo 58 ± 4% CVC(max), all P > 0.05 vs. control site). After the atorvastatin intervention (LDL = 98 ± mg * dl(-1)) there was an increase in the plateau in HC (96 ± 4% CVC(max), P < 0.001) and NO-dependent vasodilatation (68 ± 3% CVC(max), P < 0.001). Localized BH(4) alone or combo was less effective at increasing NO-dependent vasodilatation after the drug intervention (BH(4): 60 ± 5% CVC(max); combo 58 ± 2% CVC(max), both P < 0.001). These data suggest that decreased BH(4) bioavailability contributes in part to cutaneous microvascular dysfunction in hypercholesterolaemic humans and that atorvastatin is an effective systemic treatment for improving NOS coupling mechanisms in the microvasculature.

Oral atorvastatin therapy increases nitric oxide-dependent cutaneous vasodilation in humans by decreasing ascorbate-sensitive oxidants

Elevated low-density lipoproteins (LDL) are associated with cutaneous microvascular dysfunction partially mediated by increased arginase activity, which is decreased following a systemic atorvastatin therapy. We hypothesized that increased ascorbate-sensitive oxidant stress, partially mediated through uncoupled nitric oxide synthase (NOS) induced by upregulated arginase, contributes to cutaneous microvascular dysfunction in hypercholesterolemic (HC) humans. Four microdialysis fibers were placed in the skin of nine HC (LDL = 177 ± 6 mg/dl) men and women before and after 3 mo of a systemic atorvastatin intervention and at baseline in nine normocholesterolemic (NC) (LDL = 95 ± 4 mg/dl) subjects. Sites served as control, NOS inhibited, L-ascorbate, and arginase-inhibited+L-ascorbate. Skin blood flow was measured while local skin heating (42°C) induced NO-dependent vasodilation. After the established plateau in all sites, 20 mM ≪ngname≫ was infused to quantify NO-dependent vasodilation. Data were normalized to maximum cutaneous vascular conductance (CVC) (sodium nitroprusside + 43°C). The plateau in vasodilation during local heating (HC: 78 ± 4 vs. NC: 96 ± 2% CVC(max), P < 0.01) and NO-dependent vasodilation (HC: 40 ± 4 vs. NC: 54 ± 4% CVC(max), P < 0.01) was reduced in the HC group. Acute L-ascorbate alone (91 ± 5% CVC(max), P < 0.001) or combined with arginase inhibition (96 ± 3% CVC(max), P < 0.001) augmented the plateau in vasodilation in the HC group but not the NC group (ascorbate: 96 ± 2; combo: 93 ± 4% CVC(max), both P > 0.05). After the atorvastatin intervention NO-dependent vasodilation was augmented in the HC group (HC postatorvastatin: 64 ± 4% CVC(max), P < 0.01), and there was no further effect of ascorbate alone (58 ± 4% CVC(max,) P > 0.05) or combined with arginase inhibition (67 ± 4% CVC(max,) P > 0.05). Increased ascorbate-sensitive oxidants contribute to hypercholesteromic associated cutaneous microvascular dysfunction which is partially reversed with atorvastatin therapy.

Dynamic microvascular blood flow analysis during post-occlusive reactive hyperemia test in patients with schizophrenia

Patients suffering from schizophrenia have an increased mortality risk due to cardiovascular events. Recently the analysis of peripheral circulation has revealed interesting results in the study of vascular pathological conditions assuming that the state of microcirculation of the skin is at least partly representative for the constitution of other vascular beds including those of the cardiac muscle and arteries. The objective of this study was to investigate the microcirculation in patients with acute schizophrenia (PAT, n = 15, mean age 33.0 years, 7 male, 8 female) to identify whether spectral features from blood flow signals derived through laser Doppler spectrometry are significantly altered compared to healthy subjects (CON, n = 15, mean age 32.4 years, 7 male, 8 female) by means of the post-occlusive reactive hyperemia test. It was also explored if a segmentation of the post-ischemic stage can disclose more detailed and additional information about the dynamic behavior of the blood flow during hyperemic response. For this reason, time-frequency analyses were performed to observe the course of the blood flow frequency components over time. Our results indicate significant differences in the patients group, already detectable under baseline conditions but also in the hyperemic phase. The main modifications affect the respiratory (p = 0.006) as well as the cardiac (p = 0.001) activity. It was further shown that the application of a segmented analysis of the post-ischemic state considerably improves the differentiation between both groups. Only with the introduced segmentation algorithm using a window length of 2048 samples and a shift of 128 and 256 samples we could demonstrate influences of the disease on the endothelial (p = 0.029), the sympathetic (p = 0.019) and the myogenic (p = 0.029) mechanisms. These information provide further insights into the appearance of schizophrenia and could lead to an improvement of the patients' treatment to avoid the occurrence of cardiovascular events.

Imaging dermal blood flow through the intact rat skin with an optical clearing method

Noninvasive detection of skin microcirculation is very significant for clinical diagnosis and therapy of peripheral vascular disease. In this study, an optical clearing method enables a laser speckle contrast imaging (LSCI) technique to image dermal blood flow through intact rat skin. The optical clearing effect of rat skin in vitro caused by a mixture of PEG-400 and Thiazone is evaluated by a commercially available spectrophotometer with an integrating sphere. A LSCI system is applied to image the dermal blood flow of in vivo rat skin after topical treatment of the agents. The results show that the reduced scattering coefficient (630 nm) is down to 60% of the initial value after 40 min of topical treatment of the mixture on skin in vitro. In vivo experimental results show that a 12-min treatment of the mixture on the epidermis can make the skin transparent and dermal vessels can be observed, while treatment with pure PEG-400 cannot. The process of skin optical clearing lasts, and the skin can be recovered by treatment of saline solution. Because optical clearing decreases the temporal contrast, dermal blood flow can be obtained by the laser speckle contrast imaging technique.