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Pathological alterations of the microcirculatory system can be identified by measuring the temporal and spectral properties of laser Doppler flowmetry (LDF) signals acquired on the skin, and their changes following physiological stimulation. A wide range of stimulation protocols and measurement locations is observed in literature. Researchers often use non-invasive stimulation techniques, such as post-occlusive hyperaemia, cold tests, and local heating. As concerns the stimulation/recording sites, the forearm, fingers, and toes are typically selected to conduct microcirculation studies. However, recent clinical investigations showed that different anatomical sites present dissimilar blood flow patterns. Therefore, studies involving the comparison of LDF data, obtained from various anatomical locations, and thus subjected to the intrinsic heterogeneity of the microcirculation, may be methodologically inaccurate. At the moment, no consensus has been reached upon the optimal measurement location, the stimulation pattern, and the physiological parameters of interest. The aim of this study is to quantitatively characterize the heterogeneity of the peripheral perfusion at different anatomical locations: the index finger, the forearm, and the hallux. The skin microvascular system exhibits a complex vasodilatory response in the temporal domain, upon local heating. This physiological reactive hyperaemia comprises two effects: a fast transient response, correlated to neural activation, named axon reflex, followed by a slower hyperaemic plateau, mediated by the release of nitric oxide. In this work, we compare the vasodilatory reaction to heating at the different sites, based on a parametric representation of the perfusion signal. Moreover, skin blood flow is characterized by several components fluctuating at different time scales. Time-frequency decomposition of LDF signals allows to quantitatively evaluate the relative contribution of known physiological mechanisms to the regulation of the peripheral circulation. For this reason, we analyze the wavelet transform coefficients of LDF signals at baseline, to assess potential spatial heterogeneities of the perfusion power spectra among the aforementioned anatomical locations.

The study aimed to investigate local thermally induced microvascular reactivity in patients with type 1 (T1DM) or type 2 diabetes mellitus (T2DM) and polyneuropathy and to compare it with healthy controls. A hundred and fourteen subjects were investigated divided into 3 groups: 1st group -20 patients with T1DM; 2nd group -50 patients with T2DM; 3rd group -44 healthy controls. The skin perfusions of the first tiptoe were monitored by laser Doppler flowmetry during thermal test. The initial (PUi) and basal perfusions at 32°C (PUb) tended to be higher in the DM groups and the PUb of T1DM group was higher compared with the healthy subjects. The perfusion responses to heating were attenuated in the patients compared with the controls. The calculated vasodilator heat-induced indices were significantly lower and the vasoconstrictor indices during relative cooling in the recovery period were significantly higher in DM patients related to the healthy subjects. The reduced cutaneous microvascular responses to local thermal stimulation in the plantar sides of the toes of both T1DM and T2DM patients with polyneuropathy were similar to those found by previous studies in other investigated sites of glabrous and nonglabrous skin of patients with DM.

Unlabelled: The aim of the study was to assess whether Laser Doppler-recorded venoarteriolar reflex (VAR) response to hand lowering can contribute to differentiate primary from secondary Raynaud's phenomena., Materials and Methods: Skin fingerpulp perfusion (PU) of each hand of 60 persons was investigated: 15 healthy controls; 15 primary Raynaud's phenomenon (RP) patients; 15 patients with Raynaud's phenomenon secondary to systemic sclerosis (SSc); 15 patients with Raynaud's phenomenon secondary to vibration exposure. Blood perfusion was monitored by Laser Doppler flowmetry (LDF) as initial values and at a temperature of 32 degrees C with hands on the sternum (PUh) and in dependency (PUd). VAR indices were analyzed: delta VAR (DeltaVAR) calculated as (PUd-PUh); percent change of perfusion--[(DeltaVAR/PUh) x 100]; and vasoconstriction response--(PUd/PUh)., Results: Initial mean superficial skin temperatures and perfusions in Raynaud's phenomenon groups were significantly lower compared to healthy controls but with wide overlap of the values in individual cases. Venoarteriolar indices were significantly different between secondary Raynaud's phenomenon groups and healthy controls and between secondary and primary Raynaud's phenomenon groups. Percent changes were significantly higher in control and primary RP groups compared to secondary RP groups. Vasoconstriction indices between primary and secondary RP patients (p<0.0001) and between controls and secondary RP patients (p<0.0001) also differed. A loss of venoarteriolar reflex (DeltaPU>or=0) was established in 10.0% of primary, 53.3% of sclerodermic, and 36.7% of vibration-induced Raynaud's phenomenon patients. The significantly higher prevalence rate of impaired venoarteriolar reflex in secondary Raynaud's phenomenon patients proves local vasomotor dysfunction and reflects either postganglionar sympathetic insufficiency with vascular tone failure or altered smooth muscle cells' responses., Conclusions: Laser Doppler flowmetry is a valuable noninvasive method for investigation of the very early skin venoarteriolar dysfunctions, for evaluation of focal autonomic dysregulation and skin vasomotor abnormalities in RP patients. Laser Doppler-recorded venoarteriolar reflex testing is a simple procedure and an adequate additional diagnostic tool, which contributes to diagnose RP and differentiate primary from secondary RP.

The aim of this study was to investigate the venoarteriolar reflex (VAR) responses in type 1 (T1DM) and type 2 (T2DM) diabetes mellitus (DM) with polyneuropathy and to estimate their relationship with age, DM duration, initial cutaneous temperature and body mass index. Four groups of subjects were investigated: 1st group - 20 patients with T1DM; 2nd group - 50 patients with T2DM; 3rd group of 20 healthy subjects with similar age and body mass index (BMI) to the T1DM group; 4th group (Control2) of 24 healthy subjects adjusted by age and BMI to the T2DM group. The cutaneous perfusions of the big toe pulp were monitored as baseline perfusions at a temperature of 32°C in supine and sitting position with hanging legs and back in supine position. Loss of venoarteriolar reflex responses was established in 75% of T1DM patients, 78% of T2DM patients and in none of the investigated healthy controls. Reduced venoarteriolar perfusion responses were established in both T1DM and T2DM patients with polyneuropathy compared with healthy subjects. Reliable positive associations between VAR responses and the age, DM duration and initial cutaneous temperature were found. [ABSTRACT FROM AUTHOR]