Peripheral neuropathies may involve the small diameter nerve fibers of the autonomic nervous system. In the presence of clinical signs compatible with dysautonomia, it is very difficult to affirm that these signs are really linked to an alteration in postganglionic autonomic innervation, and not to a lesion of the central nervous system or to a direct damage to the tissues and innervated organs. Also, in the context of the investigation of peripheral neuropathies, there is an interest in performing objective and quantitative assessment of distal autonomic innervation. The corresponding autonomic tests are mainly based on the exploration of sudomotor or vasomotor disorders of the limb extremities. In this article, we provide an overview of the various tests available for the study of the autonomic nervous system in clinical practice, including vasomotor reactivity tests, in particular based on laser Doppler techniques, and sudomotor tests, based on axon-reflexes produced by iontophoresis of cholinergic drugs or on the simpler measurement of electrochemical skin conductance by the Sudoscan® device.

The purpose of this study was to detect and compare the surface temperature of plantar vessels in mild diabetic peripheral neuropathy (DPN) patients and healthy controls, to explore a simple, convenient and reliable method for early diagnosis of DPN, and to explore the influence of sex and age on vascular surface temperature.

In this study, 60 mild DPN patients (30 males and 30 females) and 60 healthy volunteers were randomly recruited according to their age and sex. Intra-class correlation coefficient was used to evaluate the repeatability of skin temperature measurement in the vascular area. A general linear model was used to analyse the difference of skin temperature between mild DPN patients and healthy controls.

The infrared detection results of skin temperature corresponding to blood vessels showed excellent test-retest reliability. There was no significant difference in skin temperature between sex and age. But there were significant differences in skin temperature between mild DPN patients and healthy controls, except for the posterior tibial artery.

For mild DNP patients, in case of no obvious abnormality in the infrared detection of lower extremity arterial surface temperature, the small vessels have shown early abnormal body surface temperature, that is, the surface temperature of related vessels increased. The research conclusions of this article not only enable us to better understand the correlation between body surface temperature and hemodynamic parameters, but also provide an in vivo, non-invasive, and convenient way of thinking and methods for early diagnosis of DPN.

The pathophysiology and time course of impairment in cutaneous microcirculatory function and structure remain poorly understood in people with diabetes, partly due to the lack of investigational tools capable of directly imaging and quantifying the microvasculature in vivo. We applied a new optical coherence tomography (OCT) technique, at rest and during reactive hyperemia (RH), to assess the skin microvasculature in people with diabetes with foot ulcers (DFU, n = 13), those with diabetes without ulcers (DNU, n = 9), and matched healthy controls (CON, n = 13). OCT images were obtained from the dorsal part of the foot at rest and following 5 min of local ischemia induced by inflating a cuff around the thigh at suprasystolic level (220 mmHg). One-way ANOVA was used to compare the OCT-derived parameters (diameter, speed, flow rate, and density) at rest and in response to RH, with repeated-measures two-way ANOVA performed to analyze main and interaction effects between groups. Data are means ± SD. At rest, microvascular diameter in the DFU (84.89 ± 14.84 µm) group was higher than CON (71.25 ± 7.6 µm, P = 0.012) and DNU (71.33 ± 12.04 µm, P = 0.019) group. Speed in DFU (65.56 ± 4.80 µm/s, P = 0.002) and DNU (63.22 ± 4.35 µm/s, P = 0.050) were higher than CON (59.58 ± 3.02 µm/s). Microvascular density in DFU (22.23 ± 13.8%) was higher than in CON (9.83 ± 2.94%, P = 0.008), but not than in the DNU group (14.8 ± 10.98%, P = 0.119). All OCT-derived parameters were significantly increased in response to RH in the CON group (all P < 0.01) and DNU group (all P < 0.05). Significant increase in the DFU group was observed in speed (P = 0.031) and density (P = 0.018). The change in density was lowest in the DFU group (44 ± 34.1%) compared with CON (199.2 ± 117.5%, P = 0.005) and DNU (148.1 ± 98.4, P = 0.054). This study proves that noninvasive OCT microvascular imaging is feasible in people with diabetes, provides powerful new physiological insights, and can distinguish between healthy individuals and patients with diabetes with distinct disease severity.

Background  Vascular dysfunction dominates the clinical picture of peripheral autonomic neuropathy in lower extremity. Patients and Methods  We have studied functional changes of leg vasculature in 30 patients with chronic ulceration due to peripheral autonomic neuropathy between clinical stages 1 and 3. They suffered from lower extremity wounds. After sympathetic skin response test, pedal arterial blood flow analysis including peak systolic velocity (PSV) and pulsatility index (PI) was made by duplex ultrasonography (DUS) in involved legs. Vascular anatomy of leg was also examined by magnetic resonance angiography. Results  The mean PSV value was found 58.32 cm/s in stage 1, 35.31 cm/s in stage 2, and 15.71 cm/s in stage 3. The mean PI value was observed 1.17 in stage 1, 1.43 in stage 2, and 1.87 in stage 3. In chronic stage 3, three patients had inadequate arterial blood supply and recurrent ulcer. Conclusions  We suggest that reduced sympathetic activity due to small fiber neuropathy causes temporal variations in leg blood flow. There was a nonlinear relationship between vascular functional changes and stages of disease with increased, intermediate, and decreased blood flow, respectively. DUS assessment of pedal arteries contributed to differentiation of clinical stages and permitted vascular evaluation in the course of peripheral autonomic neuropathy.

Peripheral arterial disease is very common in patients with diabetes, but it remains grossly under-recognized in this type of patients. Ankle brachial index (ABI) is a simple, non-invasive and reproducible method for detection and improving risk stratification. However, the sensitivity appears to be lower in diabetic patients and, false 'high' readings occur because of the arterial calcification of the vessel media which render the vessels incompressible.

The study evaluated the prevalence of a low ABI <0.9 in diabetic patients in a hospital-based cross sectional observational study. The study has been registered.

The prevalence of peripheral arterial disease in diabetics with ABI< 0.9 was 18%. The majority (77%) of responders were asymptomatic with mild PAD (ABI 0.7-0.9). Age >60 years, hypertension (systolic BP > 140 mmHg) and presence of foot ulcer were identified as independent risk factors. 22 participants (4.4%) of the 500 had ABI greater than 1.3 but were excluded in the analysis.

The prevalence of PAD in diabetics measured by the ABI index was low and the majority in our setting had mild PAD and were asymptomatic. ABI could be used in patients with diabetes, but values should be interpreted with precision, according to the clinical situation as higher values are common.

We investigated the significance of microangiopathy in the development of foot ulcer, which is still disputed.

We assessed microangiopathy by histological analysis of the capillary ultrastructure using transmission electron microscopy and capillary density and arteriolar morphology in paraffin-embedded sections from the skin of type 2 diabetic patients: 30 neuroischaemic patients (Isc) revascularised with peripheral angioplasty and 30 neuropathic patients (Neu) with foot ulcer, compared with ten non-diabetic volunteers.

In the diabetic patients, capillaries in the dermal papillary layer were fewer (-22.2%, 159 ± 43 vs 205 ± 52 mm(2) in non-diabetic volunteers, p < 0.01). They also showed detrimental remodelling, with a 2.2-fold increase in capillary basement membrane thickness (3.44 ± 1.19 vs 1.53 ± 0.34 μm in non-diabetic volunteers, p < 0.001) and a 57.7% decrease in lumen area (14.6 ± 11.1 vs 34.7 ± 27.5 μm(2), p < 0.001). No differences were observed between the diabetic Isc or Neu patients. Isc were more prone to develop arteriolar occlusion than Neu (16.8 ± 6.9% vs 6.7 ± 3.7%, respectively, p < 0.001). No patient had been amputated at 30 days and healing time was significantly longer in Isc (180 ± 120 vs 64 ± 50 days in Neu, p < 0.001).

Capillary microangiopathy is present in equal measure in neuroischaemic and neuropathic diabetic foot skin. The predominance of arteriolar occlusions with neuroischaemia indicated the existence of an additional 'small vessel disease' that did not affect an effective revascularisation and did not worsen the prognosis of major amputations but slowed the healing process of the neuroischaemic foot ulcer.

ClinicalTrials.gov NCT02610036.

Microvascular dysfunction in diabetes plays a crucial role in the development of diabetic complications. The skin, as one of the most accessible organs, serves as a model for the investigation of microvascular dysfunction. Several non-invasive, mostly laser-Doppler-based methods have been developed lately to assess microvascular function in the skin. Microvascular functional changes occur even in the prediabetic state and become more complex with overt diabetes, being exacerbated by the presence of peripheral and/or autonomic diabetic neuropathy. The present article aims at shedding light on the implication of endothelial and neurovascular dysfunction in microvascular changes in diabetes, highlighting the contribution of different forms of diabetic neuropathy.

Diabetic foot is traditionally attributed to a triad of neuropathy, ischemia and infection. Cellular hypoxia in diabetic foot can neither be attributed to an occlusive large artery disease (which are mostly patent) nor to the so called diabetic small vessel disease (where such occlusion was never proved). The physiological findings that accompany cellular hypoxia are confusing: elevated local blood flow and high oxygen saturation in both the tissue and its collecting veins. It is well known that some tissues (e.g. skin) are wired with two types of capillaries: True capillaries - also known as exchange capillaries, where nutrients and gases exchange takes place, and metarteriole thoroughfare channels - also known as shunting capillaries. We hypothesize that in the diabetic foot tissue blood flow is rerouted through the metarteriole thoroughfare channel, bypassing the exchange capillaries. Hence, nutrient and gas exchange is disabled and tissue cells became hypoxic regardless of the tissue blood flow. As a result of the shunt, arterial oxygen is not consumed and the oxygen saturation in the collecting veins remains high. The hereby hypothesis suggests that mal-perfusion rather than hypo-perfusion is the underlying cause of cellular hypoxia in diabetic foot. This hypothesis complies with the findings of patent arteries proximal to the affected site, normal to elevated tissue blood flow and high oxygen saturation in the affected tissue and its collecting veins.

A coupled computational model of the foot consisting of a three-dimensional soft tissue continuum and a one-dimensional (1D) transient blood flow network is presented in this article. The primary aim of the model is to investigate the blood flow in major arteries of the pathologic foot where the soft tissue stiffening occurs. It has been reported in the literature that there could be up to about five-fold increase in the mechanical stiffness of the plantar soft tissues in pathologic (e.g. diabetic) feet compared with healthy ones. The increased stiffness results in higher tissue hydrostatic pressure within the plantar area of the foot when loaded. The hydrostatic pressure acts on the external surface of blood vessels and tend to reduce the flow cross-section area and hence the blood supply. The soft tissue continuum model of the foot was modelled as a tricubic Hermite finite element mesh representing all the muscles, skin and fat of the foot and treated as incompressible with transversely isotropic properties. The details of the mechanical model of soft tissue are presented in the companion paper, Part 1. The deformed state of the soft tissue continuum because of the applied ground reaction force at three foot positions (heel-strike, midstance and toe-off) was obtained by solving the Cauchy equations based on the theory of finite elasticity using the Galerkin finite element method. The geometry of the main arterial network in the foot was represented using a 1D Hermite cubic finite element mesh. The flow model consists of 1D Navier-Stokes equations and a nonlinear constitutive equation to describe vessel radius-transmural pressure relation. The latter was defined as the difference between the fluid and soft tissue hydrostatic pressure. Transient flow governing equations were numerically solved using the two-step Lax-Wendroff finite difference method. The geometry of both the soft tissue continuum and arterial network is anatomically-based and was developed using the data derived from visible human images and magnetic resonance images of a healthy male volunteer. Simulation results reveal that a two-fold increase in tissue stiffness leads to about 28% reduction in blood flow to the affected region.

Despite the clinical usefulness of transcutaneous oxygen tension (TcPO(2)) to assess the severity of limb ischemia, the factors determining TcPO(2) in patients with peripheral arterial disease (PAD) have not been fully clarified. We therefore examined the regions of arterial stenosis and clinical factors affecting lower-extremity TcPO(2).

Resting TcPO(2) (REST-TcPO(2)) and postexercise TcPO(2) (Ex-TcPO(2)) in the calf region and the dorsalis pedis were measured simultaneously in 66 patients (132 limbs) with clinically suspected PAD, in whom angiography was also performed.

The peripheral arteries of the lower extremities were divided into five segments, and the impact of significant stenosis in each segment on ipsilateral TcPO(2) was evaluated by multiple regression analysis. In the calf region, significant stenosis of the proximal arteries (common-external iliac artery) revealed stronger involvement determining Ex-TcPO(2) than the peripheral segment (posterior tibial artery). In the dorsalis pedis, the peripheral segment (anterior tibial artery) more strongly determined Ex-TcPO(2) and REST-TcPO(2) than proximal segments. Age, creatinine, and diabetes were associated with REST-TcPO(2) of the calf region independent of arterial stenoses, while those of the dorsalis pedis were independently associated with age, and creatinine. In contrast, Ex-TcPO(2) in both regions was not independently associated with clinical factors, except for stenosis of the perfusing arteries.

The vascular lesions affecting TcPO(2) differ between the calf region (proximal > peripheral) and the dorsalis pedis (proximal < peripheral). In addition postexercise TcPO(2) is solely determined by stenosis of the perfusing arteries, while TcPO(2) at rest is affected by multiple clinical factors.

Diabetic foot disease and ulceration is a major complication that may lead to the amputation of the lower limbs. Microangiopathy may play a significant role in the pathogenesis of tissue breakdown in the diabetic foot. However, the precise mechanisms of this process remain unclear and poorly understood. Microvasculature in the skin is comprised of nutritive capillaries and thermoregulatory arteriovenous shunt flow. It is regulated through the complex interaction of neurogenic and neurovascular control. The interplay among endothelial dysfunction, impaired nerve axon reflex activities, and microvascular regulation in the diabetic patient results in the poor healing of wounds. Skin microvasculature undergoes both morphologic changes as well as functional deficits when parts of the body come under stress or injury. Two important theories that have been put forward to explain the abnormalities that have been observed are the haemodynamic hypothesis and capillary steal syndrome. With advances in medical technology, microvasculature can now be measured quantitatively. This article reviews the development of microvascular dysfunction in the diabetic foot and discusses how it may relate to the pathogenesis of diabetic foot problems and ulceration. Common methods for measuring skin microcirculation are also discussed.

The aim of this article was to investigate the effectiveness of testing cold immersion recovery responses in the diabetic foot with neuropathy using a contact thermography system based on thermochromic liquid crystals. A total of 81 subjects with no history of diabetic foot ulceration were assigned to neuropathy, non neuropathy and healthy groups. Each group received prior verbal and written description of the test objectives and subsequently underwent a comprehensive foot care examination. The room temperature and humidity were consistently maintained at 24 degrees C and less than 50%, respectively, with air conditioning. The right foot for each subject was located on the measurement platform after cold immersion in water at 18-20 degrees C. Whole-field thermal images of the plantar foot were recorded for 10 minutes. Patients with diabetes with neuropathy show the highest 'delta temperature', that is difference between the temperature after 10-minute recovery period and baseline temperature measured independently at all the three sites tested, that is first metatarsal head (MTH), second MTH and heel. This clinical study showed for the first time the evidence of poor recovery times for the diabetic foot with neuropathy when assessing the foot under load. A temperature deficit (because of poor recovery to baseline temperature) suggests degeneration of thermoreceptors, leading to diminished hypothalamus-mediated activity in the diabetic neuropathic group.

There are currently 3 established techniques employed routinely to determine the risk of foot ulceration in the patient with diabetes mellitus. These are the assessment of circulation, neuropathy, and foot pressure. These assessments are widely used clinically as well as in the research domain with an aim to prevent the onset of foot ulceration. Routine neuropathic evaluation includes the assessment of sensory loss in the plantar skin of the foot using both the Semmes Weinstein monofilament and the biothesiometer. Thermological measurements of the foot to assess responses to thermal stimuli and cutaneous thermal discrimination threshold are relatively uncommon. Indeed, there remains uncertainty regarding the importance of thermal changes in the development of foot ulcers. Applications of thermography and thermometry in lower extremity wounds, vascular complications, and neuropathic complications have progressed as a result of improved imaging software and transducer technology. However, the uncertainty associated with the specific thermal modality, the costs, and processing times render its adaptation to the clinic. Therefore, wider adoption of thermological measurements has been limited. This article reviews thermal measurement techniques specific to diabetic foot such as electrical contact thermometry, cutaneous thermal discrimination thresholds, infrared thermography, and liquid crystal thermography.

To explore mechanisms by which temperature could influence the pathogenesis and symptoms of diabetic polyneuropathy.

We conducted a literature review attempting to identify mechanisms by which diabetic polyneuropathy could be affected by temperature.

Cooling can theoretically hasten the progression of diabetic polyneuropathy through several different mechanisms. Specifically, cooling can enhance neuronal ischaemia, increase formation of reactive oxygen species, slow axonal transport, increase protein kinase C activity, and interfere with immune function. Short-term temperature fluctuations (both warming and cooling) can initiate and exacerbate neuropathic pain by causing neuronal hyperexcitability and functional deafferentation. Although normal fluctuations of distal extremity temperature may be sufficient for these effects, impaired thermoregulation may make the distal extremities more susceptible to temperature extremes. Eventually, a 'vicious cycle' may ensue, resulting in neuronal deterioration with further disruption of temperature regulation. Limited epidemiological data suggest a higher prevalence of diabetic polyneuropathy in populations living in colder locations, supporting our hypothesis.

Variations in foot temperature may play an important but as yet unrecognized role in the development and symptoms of diabetic polyneuropathy. Further basic and clinical research exploring this concept could help elucidate the natural history of diabetic polyneuropathy and lead to novel therapeutic strategies.

The potential for malignancy detection using dynamic infrared imaging (DIRI) has been investigated in an animal model of human malignancy. Malignancy was apparent in images formed at the vasomotor and cardiogenic frequencies of tumour bearing mice. The observation of malignancy was removed by the administration of an agent that blocks vasodilation caused by nitric oxide (NO). Image patterns similar to those that characterize malignancy could be mimicked in normal mice using an NO producing agent. Apparently DIRI allows for cancer detection in this model through vasodilation caused by malignancy generated NO. Dynamic infrared detection of vasomotor and cardiogenic surface perfusion was validated in human subjects by a comparison with laser Doppler flowmetry (LDF). Dynamic infrared imaging technology was then applied to breast cancer detection. It is shown that dynamic infrared images formed at the vasomotor and cardiogenic frequencies of the normal and malignant breast have image pattern differences, which may allow for breast cancer detection.

Neurophysiological assessment of the peripheral autonomic system is characterized by various limitations. An alternative approach to laser Doppler and venous plethymography is the assessment of the sympathetic vasomotor response of the radial artery obtained by continuous wave Doppler sonography. Nomogram data have been established and demonstrate the temporary disappearance of diastolic flow after coughing or deep inspiration.

We assessed the sympathetic vasomotor response in 25 patients (mean age 64 years, range 43-76) with diabetic foot syndrome. The Doppler data were correlated with nerve conduction studies of the median and peroneal nerve, the extent of radiologically diagnosed media sclerosis, and compared with nomogram values (n = 41).

Although similar mean flow velocities were found under baseline conditions, the flow pattern was characterized by higher pulsatility in the diabetic group (resistance index [RI] 1.1 vs. 0.7). No significant difference in RI was observed after coughing. The latency of onset of the response was prolonged (2.1 vs. 1.5 s), while the duration of the response did not differ (18 vs. 15 s). Only the nerve conduction velocity of the peroneal nerve correlated inversely with the RI. The extent of radiologically proven calcification tended to correlate with the pulsatility of the baseline signal and the response latencies.

The data obtained by this study suggest the concurrent existence of reduced vessel elasticity due to media sclerosis and dysfunction of the autonomic vasomotor system.

Chronic foot ulceration is a major source of morbidity in diabetic patients. Despite traditional comprehensive wound management, including vascular reconstruction, there remains a cohort of patients with non-responding wounds, often resulting in amputation. These wounds may benefit from molecular manipulation of growth factors to enhance the microcirculation.

A review of the current literature was performed using Pubmed, with secondary references obtained from key articles.

There has been a generally disappointing clinical outcome from growth factor trials, although topical platelet-derived growth factor has shown significant benefit and should be considered in non-healing, well perfused ulcers after failure of conventional wound care. The modulatory role of the extracellular matrix in the cellular response to growth factors and data from regenerative-type fetal wound healing are further areas of interest. The chemical induction of microvessel formation may become a future therapeutic option.

A loss of sympathetic function could lead to changes in capillary fluid filtration in diabetic patients. We investigated whether a decreased sympathetically mediated vasomotion in the skin in diabetic patients with peripheral neuropathy is associated with an abnormal capillary leakage.

Three matched groups were studied: 18 diabetic patients with documented peripheral neuropathy (DN), 18 diabetic patients without peripheral neuropathy (D), and 18 healthy control subjects (C). Sensory and motor nerve function of the distal extremities were assessed by standard neurography, and expressed in a sensory-motor nerve function score. Sympathetic vasomotion of the skin microcirculation was assessed by determining the power of blood flow variability in the low-frequency (0.02-0.14 Hz) band by spectral analysis of laser Doppler flowmetry at the median ankle. Skin capillary leakage was evaluated by sodium fluorescein videodensitometry at the same site of the foot.

Sympathetically mediated vasomotion of the foot skin microcirculation was lower in diabetic patients with documented peripheral neuropathy compared with diabetic patients without peripheral neuropathy and control subjects (p<0.001). Capillary sodium fluorescein leakage was larger in 18 diabetic patients with documented peripheral neuropathy than in diabetic patients without peripheral neuropathy (p<0.02) and C (p<0.005). Multiple regression analysis disclosed that a reduced sympathetically mediated vasomotion, together with a lower sensory-motor nerve function score, independently contributed to the variance in sodium fluorescein leakage, for 30% (p<0.001) and 17% (p<0.01), respectively.

A loss of sympathetic tone, apart from sensory-motor nerve dysfunction, seems to be a major determinant of an increased capillary permeability in diabetic patients with neuropathy.

Several authors have reported higher skin temperature in the feet of diabetic subjects with autonomic neuropathy. We reexamined this association in a cross-sectional study of 712 veterans with diabetes mellitus. Potential subjects included all diabetic patients enrolled in a general internal medicine clinic at a veterans affairs healthcare system. Sensory neuropathy was defined as any pedal insensitivity to the 5.07 monofilament. Autonomic neuropathy was determined using standard cardiovascular reflex tests. An infrared surface scanner was used to measure foot skin temperature at multiple sites. Subjects with sensory neuropathy had lower mean plantar foot skin temperature than those without (28.4 degrees C vs. 28.9 degrees C, P=.0101). Autonomic neuropathy as a dichotomous variable was unrelated to foot skin temperature. Foot skin temperature, though, negatively correlated with greater drop in systolic blood pressure with standing, which is an indicator of autonomic neuropathy (r=-.08, P=.0385). Adjustment for potential confounding factors using multiple linear regression analysis resulted in diminution of the associations between foot skin temperature and sensory neuropathy or orthostatic blood pressure drop, but the latter association remained statistically significant in the right foot. Diabetic veterans with sensory or autonomic neuropathy do not have higher foot skin temperature. Our results suggest that skin temperature may be slightly lower with higher orthostatic blood pressure fall. Other causes exist for the frequently observed differences in skin temperature in the feet of diabetic subjects.

Increased pressure due, to sensory neuropathy, is important in the development of plantar ulceration in type II diabetes. However, additional factors are thought to pre-dispose the skin tissue to ulceration. Autonomic neuropathy and microangiopathy are the basis for the capillary steal theory and the haemodynamic hypothesis, developed to explain the aetiology of this type of ulcer, in terms of microvascular complications. The aim of the present study was to develop a system to allow assessment of blood flow at prevalent sites of ulceration. Previous studies have been limited to assessment of the bare foot under rest conditions. The new system allows measurements to be made in-shoe, during static and dynamic loading. The system comprises a laser Doppler sensor, a load sensor, measurement shoe, instrumentation and analysis software. The measurement shoe was designed to minimise movement artefact and provide thermal insulation for the foot. A simple flow rig was used to characterise the sensor. The blood flux response was linear (<5% deviation from ideal) for particle concentrations up to 0.25% and for mean particle velocities up to 8mm s(-1). The worst case drift in the response over a six-month period was 3.7%. Device to device repeatability varied by 12.5% over five devices.

Capillaries play a critical role in cardiovascular function as the point of exchange of nutrients and waste products between the tissues and circulation. Studies of capillary function in man are limited by access to the vascular bed. However, skin capillaries can readily be studied by the technique of capillaroscopy which enables the investigator to assess morphology, density and blood flow velocity. It is also possible to estimate capillary pressure by direct cannulation using glass micropipettes. This review will describe the techniques used to make these assessments and will outline some of the changes that are seen in health and disease.

Early diagnosis of diabetic autonomic neuropathy contributes to the prevention of serious complications and improves the prognosis of patients with diabetes. Common tests of peripheral autonomic function are the quantitative sudomotor axon reflex test or the sympathetic skin response (SSR). Quantitative sudomotor axon reflex test is quantifiable but technically demanding. Sympathetic skin response cannot be quantified easily. To study whether measurement of skin vasomotion is suited to assess early sympathetic peripheral neuropathy, we monitored skin blood flow at the index finger pulp using laser Doppler flowmetry before and after electrical stimulation. We assured that the stimulus was sufficient to elicit an efferent sympathetic response by monitoring palmar SSR ipsilateral to the flow measurement. In 21 diabetic patients with at least stage one polyneuropathy and 21 age-matched controls, SSR was recorded from one palm and sole following electrical stimulation at the contralateral wrist. Sympathetic skin response was present at the palms in all patients and controls and absent at the sole of two patients only. Eight patients (38.9%) had abnormal SSR, with absent plantar responses in two patients, prolonged plantar latencies in six patients, and prolonged volar SSR latencies in two patients. Skin blood flow responses were more often abnormal (46.1%) than SSR (P < 0.05), responses were delayed in two patients and absent in another 8 patients. Skin blood flow retest reliability was high with a repeatability coefficient of 10.64% in controls and 12.34 % in patients. Skin blood flow monitoring after sympathetic stimulation provides a reproducible parameter of sympathetic vasomotor control and complements the diagnostic value of SSR testing.

In view of the relationship between microvascular pathology and organ complications in diabetes mellitus, the aim of the present study was to examine the microvascular response of upper arm skin to non-immunological contact irritants in 17 insulin-dependent diabetic patients and 11 non-diabetic controls.

Non-immunological contact urticaria, an inflammatory reaction mediated in a unique way, not previously studied in diabetic patients, was examined. The test agents were benzoic acid and methyl nicotinate. The intensity of the reactions was measured using laser-Doppler flowmetry and colorimetry. The patients were divided into two groups, depending on whether they had had diabetes for less or more than 10 years.

There were no differences in the maximal blood flow responses between the groups, but the diabetic patients showed increased blood flow responses to the lowest irritant concentrations compared to the controls. The reactions in the two groups of diabetic patients were similar.

The present study suggests that the microvascular reactivity of diabetic skin to non-immunological contact irritants is increased.

Neuropathy and ischemia, two common complications of diabetes mellitus, are the primary underlying risk factors for the development of foot ulcers and their complications. The presence of symmetric distal polyneuropathy, encompassing motor, sensory, and autonomic involvement, is one of the most important factors in the development of diabetic foot ulcers. Perhaps one third of diabetic foot ulcers have a mixed neuropathic and ischemic etiology. Although neuropathy and ischemia are the primary predisposing factors in the formation of diabetic foot ulcers, an initiating factor, such as physical or mechanical stress, is required for an ulcer to develop. Ischemic ulcers develop as a result of low perfusion pressure in a foot with inadequate blood supply, whereas neuropathic ulcers result from higher pressures in a foot with adequate blood supply but loss of protective sensation. In addition to increasing the risk of ulceration, diabetes mellitus also increases the risk of infection by impairing the body's ability to eliminate bacteria. The processes by which ulcers develop are reviewed here.

19 insulin-dependent diabetes mellitus (IDDM) patients participated in a randomized double-blind crossover investigation to investigate the impact of human C-peptide on skin microvascular blood flow. The investigation was also carried out with 10 healthy volunteers. Blood pressure, heart rate, blood sugar, and C-peptide levels were monitored during a 60-min intravenous infusion period of C-peptide (8 pmol kg-1 min-1) or saline solution (154 mmol liter-1 NaCl), and 30 min after stopping the infusion. During the same time period, capillary blood cell velocity (CBV), laser Doppler flux (LDF), and skin temperature were assessed in the feet. In the verum arm, C-peptide levels increased after starting infusion to reach a maximum of 2.3+/-0.2 nmol liter-1 after 45 min, but remained below 0. 15 nmol liter-1 during the saline treatment. Baseline CBV was lower in diabetic patients compared with healthy subjects (147+/-3.6 vs. 162+/-4.2 micron s-1; P < 0.01). During C-peptide administration, CBV in IDDM patients increased progressively from 147+/-3.6 to 167+/-3.7 micron s-1; P < 0.001), whereas no significant change occurred during saline infusion or in healthy subjects. In contrast to the CBV measurements, the investigation of LDF, skin temperature, blood pressure, heart rate, or blood sugar did not demonstrate any significant change during the study. Replacement of human C-peptide in IDDM patients leads to a redistribution in skin microvascular blood flow levels comparable to levels in healthy subjects by increasing the nutritive CBV relative to subpapillary arteriovenous shunt flow.

Neurogenic inflammation, mediated by unmyelinated C-nerve fibers, is part of the acute neurovascular response to injury. Laser doppler flowmetry was used to measure the flare response to transcutaneous electrical nerve stimulation (TENS) and to compare this axon reflex vasodilatation with postischemic hyperemia in the skin of the foot in diabetic and nondiabetic subjects. Twenty-one control subjects and 57 diabetic patients (25 type I; 32 type II; 14 without complications; 14 with neuropathy and without retinopathy; 8 with retinopathy and without neuropathy; 21 with neuropathy and retinopathy) were enrolled in the study. Following TENS, an increase in skin blood flow was found at the dorsum of the foot without any significant difference between the different groups. Compared to the control group, axon reflex vasodilatation was significantly reduced in the group of patients with diabetic neuropathy and in the group of patients with diabetic neuropathy and retinopathy at the pulp of the hallux (61 +/- 15 versus -6 +/- 16; versus 23 +/- 5; p < 0.05, respectively). All investigated groups exhibited a significant increase in skin blood flow after arterial occlusion without any significant difference between the groups. A good association was observed between postocclusive and TENS-induced hyperemia at the dorsum of the foot (r = 0.39; p = 0.0002), but only a weak association was found at the pulp of the hallux (r = 0.24; p = 0.03). TENS-induced hyperemia was associated with a diminished sweat response (p = 0.03), but not with pathological cardiovascular function tests (p = 0.07). Electrical axon reflex vasodilatation is diminished in diabetic patients suffering from peripheral autonomic C-fiber injury, especially in skin rich in thermoregulatory blood flow. The diminished neurovascular response is independent of vascular alterations in diabetes mellitus.

The acute effects of a newly synthesized thromboxane dual blocker (KDI-792), a combined thromboxane synthase inhibitor and receptor antagonist, on lower limb circulation were examined using two-dimensional color and pulse Doppler ultrasonography and laser Doppler flowmetry. A randomized single-masked, placebo-controlled trial was performed on 36 type 2 diabetic patients with minimally impaired baseline flow. The anatomical cross-sectional area (CSA), maximum flow velocity (MFV) and flow volume index (FVI) in the right dorsal pedis artery (DPA) and right femoral artery (FA) were determined by Doppler ultrasonography before and 45 and 90 minutes after the administration of either 100 or 200 mg of KDI-792 to the dose groups or placebo to the control group. Periflux blood flow (PBF) in the right foot was determined simultaneously by laser Doppler flowmetry. Both CSA and MFV in the dose groups were significantly increased in both the FA and DPA. FVI was markedly increased from 21.4 +/- 3.7 to 68.3 +/- 26.8 in the DPA (M +/- SD, P < 0.01) and from 365.4 +/- 35.3 to 771.7 +/- 75.7 in the FA (P < 0.01) in the 200 mg dose group. In the 100 mg dose group, FVI was markedly increased from 20.0 +/- 8.7 to 68.3 +/- 26.8 (P < 0.01) in the DPA and from 372.5 +/- 130.0 to 677.5 +/- 187.8 (P < 0.01) in the FA. PBF was also increased in both dose groups (from 4.15 +/- 1.4 to 7.0 +/- 4.0 ml/min/100 g tissue in the 200 mg dose group, P < 0.01), whereas there were no significant changes in either measurement in the control group. There were no significant changes in pulse rate or blood pressure after administration in either the dosage group or the placebo group. These and previous findings indicate that a single administration of KDI-792 markedly increases lower limb blood flow and might have a more potent vasodilating effect than that of prostaglandin I2 derivatives.

To determine the relationship of skin microangiopathy and other diabetic microvascular complications, we measured changes in skin blood flow after the administration of the prostacyclin (PGI2) analogue, beraprost sodium (BPS), in 82 patients with non-insulin-dependent diabetes mellitus and 20 healthy subjects. The diabetic patients had various degrees of retinopathy and nephropathy. Using laser Doppler flowmetry we measured skin blood flow at the dorsum of the right big toe at various times after the administration of 40 micrograms BPS and calculated the blood flow change (delta flux = peak flux--basal flux). We also determined the ankle pressure index (API), an ankle/brachial systolic pressure ratio. The basal blood flow was higher in healthy subjects than in diabetic patients (P < 0.001). BPS significantly increased blood flow in both diabetic patients and healthy subjects (P < 0.001). In all 102 subjects delta flux was positively correlated with the API (R = 0.40, P < 0.001). Despite no differences in API among the diabetic retinopathy and nephropathy subgroups, the delta flux in diabetic patients with progressive retinopathy and macroalbuminuria was significantly lower than in healthy subjects or in diabetic patients with less severe retinopathy and nephropathy (P < 0.05). The results suggested that BPS increases skin blood flow and the flow increase induced by BPS is related partly to the levels of API. The effect of BPS on skin blood flow decreased with an increases in the severity of retinopathy and nephropathy. Diabetic skin microangiopathy appears to coexist with other microvascular diabetic complications and may be proportional to their severity.

In recent years a variety of techniques have been developed for studying peripheral microvascular function in man, which have provided important information regarding the functional breakdown of the microcirculation in diabetes mellitus. In insulin dependent diabetes a sequence of physiological changes have been described which support the so-called haemodynamic hypothesis: control-dependent increases in capillary pressure result in microvascular sclerosis leading to limitation of hyperaemia and loss of autoregulation. Furthermore, capillary pressure appears to be especially raised in patients with incipient nephropathy who are at particular risk of microangiopathy. The limitation of maximum hyperaemia is duration related, may be observed in early childhood, and is correlated with the degree of basement membrane thickening. In contrast in normotensive non-insulin dependent patients a different array of functional disturbances are described: Capillary pressure and capillary filtration coefficient are normal whereas maximum hyperaemia is profoundly depressed even at diagnosis. This differential pattern of abnormalities arguably reflects the impact of a prediabetic insulin resistant phase on the subsequent expression of microangiopathy. An understanding of the physiological breakdown of the microcirculation in diabetes permits the generation of plausible candidate cellular and molecular mechanisms, knowledge of which will accelerate the development of protective therapy.

We examined the effect of cutaneous warming on the transcutaneous oxygen measurement (TcPO2) at standard locations below the knee, on the dorsal foot, on the plantar right great toe, and on the plantar surface under the second metatarsal head of 656 diabetic and 16 nondiabetic subjects. All subjects underwent a directed medical history, physical examination, and neurovascular lower extremity evaluation and assessment of autonomic neuropathy. Associations between autonomic neuropathy and TcPO2 were tested using two-way analysis of variance and multiple linear regression. An unexpected, statistically significant fall in TcPO2 occurred with cutaneous warming from 37 degrees C to 44 degrees C on the plantar great toe surface that did not differ by presence of autonomic neuropathy, or the presence of diabetes (mean change: -8.82 mmHG, 95% confidence interval [CI]: -7.70 to -9.93). The TcPO2 measured at the plantar metatarsal head site also fell with cutaneous warming from 37 degrees C to 44 degrees C (mean change: -9.67 mmHG, 95% CI: -7.75 to -11.59). As expected, the TcPO2 increased with cutaneous warming from 37 degrees C to 44 degrees C on the dorsal foot site (mean rise:= 35.61 mmHg, 95% CI: 34.18 to 37.04). The mean TcPO2 at any site did not differ by presence of autonomic neuropathy at either 37 degrees C or 44 degrees C. We conclude that cutaneous warming leads to a paradoxical fall in TcPO2 on the plantar foot surface that does not depend on the presence of autonomic neuropathy or diabetes. Caution in interpretation of ambient versus warmed plantar TcPO2 values is recommended.

Microvascular research is seriously hampered by the great temporal and spatial variability of the measured skin blood flow and variation in sympathetic vasomotor reflexes within and between persons. Therefore skin vasomotor reflexes were studied before and after ulnar nerve blockade within the same person, resulting in a temporal complete denervation of the fifth finger and partial denervation of the fourth finger. Skin temperature and laser Doppler flux (LDF) were registrated to measure predominantly arteriovenous shuntflow. Measurements were performed on the palmar tip of the second and fifth finger in nine healthy volunteers, at baseline, and during a sympathetic reflex test (i.e. inspiratory gasp) and postural response test. Beat-to-beat digital blood pressure was recorded from the third and fourth finger by a Finapres device. Baseline capillary blood cell velocity (CBV) was measured at the nailfold of the second and the fifth finger. After ulnar blockade baseline skin temperature, LDF and CBV increased significantly, with respectively (mean +/- SE) 3.2 +/- 0.9 degrees C, 20.9 +/- 5.9 relative perfusion units and 0.79 +/- 0.40 mm-1 s. The percentage LDF decrease of the fifth finger during inspiratory gasp was 48.2 +/- 5.3% before and 3.1 +/- 0.9% after blockade. The postural response test showed a decrease in LDF of the fifth finger with no significant difference before and after blockade, respectively 12.3 +/- 14.7% and 8.0 +/- 2.7%, while no difference was found in the increase in digital blood pressure in the denervated fourth finger compared to both the same finger before blockade and to the third non-blocked finger.(ABSTRACT TRUNCATED AT 250 WORDS)

We have recently shown that the skin microcirculation of toes is significantly impaired in patients with diabetes and peripheral vascular disease, and this may be one major reason why these patients are highly susceptible to developing skin ulcers. The aim of the present study was to investigate whether the skin microcirculation is impaired also in diabetic patients free from macroangiopathy. One foot in each of 20 patients with insulin-dependent diabetes was investigated: 10 patients with and 10 patients without late complications. All patients had normal arterial circulation of their lower extremities. Two groups of age- and sex-matched healthy subjects served as controls. The capillary blood cell velocity in the nailfold of the great toe was investigated by computerised videophotometric capillaroscopy, and the total microcirculation within the same area evaluated by laser Doppler fluxmetry. The capillary blood cell velocity and the total skin microcirculation were studied during rest, and during postocclusive reactive hyperaemia. The total microcirculation was similar in patients and control subjects, whereas the capillary circulation was markedly reduced (p < 0.01) in the patients. The ratio between the capillary and total microcirculation was significantly decreased (p < 0.05-0.01) in the patients as compared to the control subjects, indicating a local maldistribution of blood in the skin microcirculation of the diabetic patients. The results of the present study show that in spite of a normal total skin microcirculation in the toes of insulin-dependent diabetic patients, both with and without late complications, the nutritional capillary circulation is severely impaired.(ABSTRACT TRUNCATED AT 250 WORDS)

There is a close relationship between the abnormal microcirculation in diabetic subjects and diabetic neuropathy. Neurogenic factors play a prominent role in the regulation of the microcirculation. In diabetic neuropathy, damage to these mechanisms results in a profound haemodynamic disturbance with increased arteriovenous shunting, abnormal postural regulation of blood flow, and abnormal inflammatory responses to tissue injury. Abnormal neurogenic regulation of microvascular haemodynamics may contribute to the development of microangiopathy manifest as increased basement thickening and both are undoubtedly implicated in the pathogenesis of diabetic foot ulceration. In turn it is now recognized that microvascular abnormalities may contribute to the ischaemic aetiology of diabetic neuropathy.

The effect of lowering the foot on the factors governing fluid filtration in the foot were studied in 12 male insulin-dependent diabetic subjects and 10 controls. Toe skin blood flow, measured by laser Doppler flowmetry, was significantly higher during dependency in the diabetic group. In the control subjects, the colloid osmotic pressure of venous blood sampled from the foot rose to 47.7 mmHg (range 45.1-53.8) after 50 min of foot dependency. In the diabetic group, colloid osmotic pressure failed to rise to the same extent (median 36.7 mmHg; range 28.6-43.0; P < 0.001). Capillary pressure, measured directly by the Landis microinjection technique, was significantly higher in the diabetic group (85.3 +/- 1.7 (n = 6) vs. 92.2 +/- 4.6 cm H2O (n = 6); P < 0.007), as was foot swelling rate determined by mercury strain gauge plethysmography (0.069 +/- 0.022 vs. 0.099 +/- 0.025 ml min-1 100 ml-1; P < 0.02). These results suggest an impairment of the oedema-preventing mechanisms in diabetic subjects which may contribute to the risks of ulceration in the diabetic foot.

Transcutaneous oxygen tension is a useful method with which to assess the functional status of skin blood flow. The reduced values observed in diabetic patients have been interpreted as a consequence of peripheral vascular disease. However, diabetic patients show lower transcutaneous oxygen tension values than control subjects with equivalent degrees of peripheral vascular disease, suggesting that additional factors are involved. Since the autonomic nervous system influences peripheral circulation, we studied the relationship between autonomic neuropathy and foot transcutaneous oxymetry in non-insulin-dependent diabetic (NIDDM) patients without peripheral vascular disease. The following age-matched patients were selected and evaluated: control subjects, C, (n = 20), NIDDM patients without autonomic neuropathy, D, (n = 16) and with autonomic neuropathy, DN, (n = 20). All diabetic patients showed lower transcutaneous oxygen tension values than control subjects, while no differences were observed between the diabetic patients with and without autonomic neuropathy. In addition the saturation index that increases in the presence of autonomic neuropathy does not correlate with foot TcPO2. In conclusion autonomic neuropathy does not influence foot TcPO2 and therefore it is unlikely that it contributes to development of foot lesions during induction of foot skin ischaemia.

Macroaggregated albumin has been used to assess capillary circulation for over 20 years. The aim of the present study was to use 99mTc-macroaggregated albumin (99mTc-MAA) perfusion scanning to assess capillary circulation in feet with ischaemic ulcers in patients with diabetes, and relate the appearances to outcome. Twenty-three patients with diabetes presented with a total of 41 neuroischaemic foot ulcers. Perfusion scanning was performed by direct femoral artery injection of approximately 400,000 particles of 99mTc-MAA and imaging with a gamma camera. Patients were followed prospectively for 3 months. Scans were graded independently by a radiologist who was unaware of the site of the ulcers. Significant associations were detected between a radiologist's assessment of increased tissue perfusion and complete healing after 3 months (p = 0.047) and poor tissue perfusion on the image and failure to heal (p = 0.0005). This technique may be useful in deciding whether to persist with conservative treatment in patients with diabetes and foot ulceration.

The diabetic neuropathic ulcer is typically slow to heal and recurrent. Macrovascular insufficiency is usually excluded as foot pulses are present and ankle:brachial pressure ratios are not decreased. These assessments cannot however exclude more distal vascular disease. Digital pressure measurements enable a reliable assessment of the distal peripheral vascular status to be made. The aim of this study was therefore to use toe pressures to assess the contribution of distal ischaemia in the pathogenesis of the neuropathic ulcer. Sixteen diabetic patients with recurrent neuropathic foot ulceration had their toe pressures compared to 10 neuropathic patients without a history of foot ulceration, 10 diabetic control subjects, and 11 normal subjects. Four non-diabetic patients with neuropathy and foot ulceration were also assessed. All subjects had ankle:brachial pressure indices > or = 1. Toe pressure was assessed using laser Doppler flowmetry to record the return of skin blood flow. The toe:brachial pressure index (TBI) was then calculated. The diabetic patients with a history of recurrent neuropathic ulceration, had the lowest mean TBI, 0.63 +/- 0.14 (SD), compared to the non-ulcerated diabetic neuropathy patients, the diabetic control subjects, and the normal subjects. 0.84 +/- 0.11, 0.82 +/- 0.1, and 0.81 +/- 0.07, p < 0.01, respectively. Three of the four non-diabetic patients with neuropathic foot ulceration also had an abnormally low TBI. Reduced toe pressure measurements are thus found to be associated with neuropathic foot ulceration. The contribution of distal ischaemia in the pathogenesis of the diabetic neuropathic foot ulcer needs to be evaluated.