Cutaneous Perfusion Research Articles

Investigation into the affectivity on cutaneous blood perfusion of different application time lengths of cold hydrotherapy

Introduction As scientific research into the use of hydrotherapy is scarce and often vague in its recommendation for practical use, this study was designed to test and compare the effects on upper limb blood flow of differing time lengths of short cold hydrotherapy application, with a view to improving the current short duration hydrotherapy application guidelines used in the British College of Osteopathic Medicine clinic. It was proposed that the different time lengths of hydrotherapy application would have a significantly different influence on both ipsilateral and contralateral blood perfusion and skin temperature. Design Crossover design, intervention study. Methods Intervention: Short duration application of cold hydrotherapy of duration 30s, 1min, 2min, 3min and 5min using cold wraps at 12°C to the dominant forearm. Participants: Thirty-five asymptomatic, right-hand dominant male subjects. Outcome Measures: Blood flow and skin temperature measured by the Microflo DSP Digital Laser Perfusion Monitor. Results All short duration time lengths of application of cold hydrotherapy had a significant effect on blood perfusion both in the arm to which the hydrotherapy was applied and to the contralateral arm. There was a significant difference in the skin temperature of the arm to which the hydrotherapy was applied but not to the contralateral arm. The results also showed that there was no significant difference in blood perfusion between the differing time lengths of application. Conclusions It was concluded therefore that short duration applications of hydrotherapy do have a significant effect on blood perfusion in both the limb to which they are applied and to the contralateral limb. It was also concluded that there was no significant difference between the different time lengths of application thus a 1-min application of cold hydrotherapy overall had a similar effect on blood flow as a 5-min application.

Drive dependent neural functional of the self-organisation of global drive reduction: an interspecies comparison

Introduction: We have repeatedly demonstrated the practical significance of a 0.15 Hz rhythm band in the cutaneous perfusion patterns (e.g. 1). In order to study the origin of this rhythm, we studied and analysed a set of physiological systems in the frequency domain in dog and in man by modifying the level of activation. In dog this was achieved using anesthetics and in man using relaxation techniques. Methods: An adult male mongrel dog (BW18kg) was administered additional chloralose-urethane after fading of the initial anesthesia. Invasively recorded were blood pressure, intrapleural pressure, and extracellular neural activity of reticular neurons in the brainstem. In man, an expert (female, 56 yrs.) practiced autogenic training while non-invasively recording blood pressure, thoracic excursions, and forehead skin perfusion. Analysis used non-linear routines: Morlet-Wavelet time frequency spectra, Pointwise transinformation. Results: In both species, non-linear analysis unveiled identical dynamics in response to the experimental maneuvers as the 0.15 Hz emerged first in unspecific neurons to appear in all other cardiovascular time series. Discussion: The reticular formation (RF) in the lower brainstem was shown to be responsible for the generation of cardio-vascular-respiratory rhythms in mammals in a frequency band at 0.15 Hz. This rhythm emerged in unspecific reticular neurons of the RF not associated with any specific nuclei. This rhythm was therefore referred to as the reticular rhythm (retR) which was not identical with the respiratory rhythm, but both were coordinated exhibiting temporarily phase- and frequency-coupling (2,3).

Effect of an 8-week resistance training program on cutaneous perfusion in type 2 diabetes

A positive association has previously been demonstrated between chronic aerobic exercise and prior maximal exercise and enhanced dorsal foot skin perfusion in physically active individuals with type 2 diabetes. The current study examined whether an 8-week resistance training program would also positively affect cutaneous perfusion in type 2 diabetic individuals. Ten individuals with type 2 diabetes and nine similar nondiabetic controls participated in 8 weeks of moderate-intensity resistance training. Prior to training, dorsal foot cutaneous perfusion was measured noninvasively by continuous laser Doppler assessment at baseline and during localized heating to 44°C. These measurements were repeated exactly 48–72 h following 8 weeks of resistance training performed 3 days per week. Interstitial nitric oxide (NO) levels were measured concurrently in the contralateral foot dorsum. Neither subject group experienced significant increases in dorsal foot perfusion responsiveness during local heating to 44°C following moderate resistance training, nor did the training significantly enhance baseline skin perfusion. Interstitial NO levels were not significantly different under any condition. At baseline, groups differed only on fasting serum glucose and overall glycemic control. In conclusion, the responsiveness of cutaneous perfusion in response to heating to 44°C is not significantly enhanced by 8 weeks of moderate resistance training in diabetic individuals or their matched controls, independent of interstitial NO levels.

Exogenous Zinc Improves Blood Fluidity But Has No Effect on the Mechanisms of Vascular Response to Acetylcholine Iontophoresis in Humans

Recent findings in cellular signaling function of zinc through the mobilization intracellular calcium or by inducing ATP release suggest that extracellular zinc plays an important role in many physiological functions. However, such an extracellular signaling action of zinc for most cells is not known. Therefore, we investigated whether zinc plays any role in endothelium- dependent acetylcholine (ACh)-induced vasodilatation in microvascular beds. Transdermal iontophoresis was used to transport ACh through the forearm skin and cutaneous perfusion was measured using a laser Doppler flowmeter (LDF). Experiments were repeated using (1) zinc instead of ACh to test the effect of zinc ions alone and (2) concomitant iontophoresis of ACh and zinc to explore the effect of zinc on ACh-induced vasodilatation. Although zinc augments blood flow, curve-fitting to LDF signals indicate that zinc has no effect on the neural and endothelial component of ACh-induced vasodilatation. Additionally, no effect of Zn2+ on blood flow was found during its iontophoresis alone. Therefore, it is suggested from the Fourier analysis of LDF signals that the Zn+ might influence blood fluidity by its action on red blood cells deformability/ aggregability during a high-blood-flow condition, which might, in turn, decrease blood viscosity and improve blood flow in vivo.

Comparison of the Role of the Subcutaneous Tissues in Cutaneous Wound Healing in the Dog and Cat

To describe and compare the contribution of the subcutaneous tissues to 1st and 2nd intention cutaneous wound healing in the dog and cat. Experimental study. Domestic shorthaired cats (n=6) and 6 beagle dogs. Paired wounds were created on either side of the dorsal midline; the subcutaneous tissue was removed on 1 side and left intact on the other. Square, open wounds of the dorsal aspect of the thorax were observed for 21 days to monitor granulation tissue formation, wound contraction, epithelialization, and total healing (contraction+epithelialization). Breaking strength of sutured linear wounds was measured 7 days after wounding. Laser-Doppler perfusion imaging (LDPI) was used to measure cutaneous perfusion. First intention healing: subcutaneous tissue removal had no consistent effect on sutured wound strength at 7 days in dogs or cats. Second intention healing: removal of subcutaneous tissue reduced wound perfusion, granulation, contraction, epithelialization, and total healing. Granulation tissue formation and wound contraction were delayed to a significantly greater degree in cats than in dogs (P<.05). Two dogs (33%) had minor wound infections. The subcutaneous tissues make an important contribution to 2nd intention cutaneous healing. Dog and cat wounds had delayed 2nd intention healing when subcutaneous tissues were removed; wounds in dogs, but not cats, had largely recovered from this delay by 21 days. Extensive debridement of subcutaneous tissue may delay wound healing particularly in feline patients. A higher risk for wound infections may accompany extensive removal of subcutaneous tissues in dogs.

Contrasting Effects of Varicose Vein Surgery on Endothelial-dependent and -independent Cutaneous Vasodilation in the Perimalleolar Region

Objectives To evaluate the effects of varicose vein surgery on cutaneous microvascular perfusion and vasodilator responses to acetylcholine (Ach) and sodium nitroprusside (SNP) in the gaiter area of patients with great saphenous vein insufficiency. Methods Twenty-nine patients with isolated great saphenous vein incompetence attended three study mornings (before surgery, and 6–8 weeks and 6 months after sapheno-femoral ligation+partial stripping) during which cutaneous microvascular responses were measured in the supine and standing positions using laser Doppler fluximetry (LDF) combined with incremental-dose iontophoretic administration of endothelial-dependent (Ach) and -independent (SNP) vasodilators. Results Varicose vein surgery had no significant effect on baseline cutaneous perfusion or the microvascular response to Ach: e.g. peak vasodilator responses to the 1000 μC stimulus were mean 58 SEM 7, 64 SEM 6 and 65 SEM 7 PU on the pre-operative, 6–8 weeks and 6 months assessments. In contrast, the corresponding responses to SNP were significantly increased following surgery: e.g. at 2000 μC, mean 63 SEM 9, 142 SEM 4 and 157 SEM 9 PU ( p<0.0001) in the upright position. Conclusions Sapheno-femoral ligation and partial stripping in patients with great saphenous vein insufficiency improves endothelial-independent cutaneous vasodilator function at the gaiter area, which may at least partly explain the benefits of surgery in reducing the risk of venous ulceration.

Change in cutaneous perfusion following 10 weeks of aerobic training in Type 2 diabetes

A small, but positive, association between aerobic training status or prior maximal exercise and enhanced dorsal foot skin perfusion in active individuals with Type 2 diabetes has been shown. This study, therefore, was designed to examine whether an aerobic training intervention would positively affect cutaneous perfusion in sedentary Type 2 diabetic individuals as well. Nine sedentary participants with Type 2 diabetes (DS) and 10 obese nondiabetic controls (CS) were studied. Prior to the initiation of aerobic training, dorsal foot cutaneous perfusion was measured noninvasively by continuous laser Doppler assessment at baseline and during localized heating to 44 °C. These measurements were repeated 48–72 h following 10 weeks of moderate aerobic training performed 3 days per week. Interstitial nitric oxide (NO) levels were measured concurrently in the contralateral foot dorsum. Aerobic training did not significantly enhance baseline skin perfusion, nor were interstitial NO levels different under any condition. At baseline, groups differed only in glycated hemoglobin (HbA1c), fasting serum glucose, HDL-cholesterol, and insulin resistance. At rest, cutaneous perfusion during local heating to 44 °C was significantly lower in DS before training, but did not differ significantly from CS afterward. Neither group, however, experienced significant increases in dorsal foot perfusion during local responsiveness to heating to 44 °C following 10 weeks of moderate aerobic training, despite slightly lower perfusion in DS before training; these findings were independent of interstitial NO levels. Thus, moderate aerobic training for only 10 weeks does not appear to reverse the impairment in cutaneous perfusion of the foot dorsum in response local heating in a Type 2 diabetic population.

Cutaneous Wound Healing in the Cat: A Macroscopic Description and Comparison with Cutaneous Wound Healing in the Dog

To describe the macroscopic features of first and second intention cutaneous wound healing in the cat and compare with the dog. Experimental study. Domestic shorthaired cats (6) and beagle dogs (6). Square, open cutaneous wounds created on the dorsal aspect of the thorax were evaluated for 21 days for temporal and spatial development of granulation tissue, wound contraction, epithelialization, and total healing. To evaluate first intention healing, breaking strength of sutured linear cutaneous wounds was measured at 7 days post-wounding. Laser-Doppler perfusion imaging was used to measure cutaneous perfusion. First intention healing: sutured wounds in cats were only half as strong as those in dogs at day 7 (0.406 versus 0.818 kg breaking strength). Second intention healing: cats produced significantly less granulation tissue than dogs, with a peripheral, rather than central distribution. Wound epithelialization and total wound healing (total reduction in open wound area from contraction and epithelialization) were greater for dogs than for cats over 21 days. Wound contraction on day 7 was greater for dogs, but not on day 14 or 21. Cutaneous perfusion was initially greater for dogs than for cats, but no differences were detected after day 7. Significant, previously unreported differences in cutaneous wound healing exist between cats and dogs. In general, cutaneous wounds in cats are slower to heal. Cats and dogs also appear to use different mechanisms of second intention healing. In cats wounds close mainly by contraction of the wound edges, whereas in dogs wounds close more from central pull, and epithelialization. Surgeons should view the cat as a unique species, which presents its own special challenges in wound healing, and should take this into account when planning treatment of feline wounds, either by primary closure, or by second intention healing.

Effects of exercise training and detraining on cutaneous microvascular function in man: the regulatory role of endothelium-dependent dilation in skin vasculature

This study investigated how exercise training and detraining affect the cutaneous microvascular function and the regulatory role of endothelium-dependent dilation in skin vasculature. Ten healthy sedentary subjects cycled on an ergometer at 50% of maximal oxygen uptake (VO(2max)) for 30 min daily, 5 days a week, for 8 weeks, and then detrained for 8 weeks. Plasma nitric oxide (NO) metabolites (nitrite plus nitrate) were measured by a microplate fluorometer. The cutaneous microvascular perfusion responses to six graded levels of iontophoretically applied 1% acetylcholine (ACh) and 1% sodium nitroprusside (SNP) in the forearm skin were determined by laser Doppler. After training, (1) resting heart rate and blood pressure were reduced, whereas VO(2max), skin blood flow and cutaneous vascular conductance to acute exercise were enhanced; (2) plasma NO metabolite levels and ACh-induced cutaneous perfusion were increased; (3) skin vascular responses to SNP did not change significantly. However, detraining reversed these effects on cutaneous microvascular function and plasma NO metabolite levels. The results suggest that endothelium-dependent dilation in skin vasculature is enhanced by moderate exercise training and reversed to the pretraining state with detraining.

Skin vasoreactivity to insulin iontophoresis is reduced in elderly subjects and is absent in treated non-insulin-dependent diabetes patients

We investigated the skin vasoreactivity to insulin in normal subjects and in treated non-insulin-dependent diabetes mellitus (NIDDM) patients. We measured cutaneous perfusion by laser-Doppler flowmetry (LDF) at rest and during skin cathodal iontophoresis (six pulses of 0.1 mA each for 20 s, with 40 s interval between stimulations) of insulin (0.1 ml Humulin R 100 IU/ml diluted 1/10 with of 0.9% saline solution) in 45 healthy subjects (HS), (25 males, 20 females, aged 45 ± 18 years), and in 15 treated NIDDM patients (13 males), aged 66 ± 8 years. Fifteen of the HS were used as controls. In these 15 sex- and age-matched HS and in the patients, we assessed also the skin postischemic hyperemia by LDF. In HS cutaneous blood flux response (CBF) to iontophoresis of insulin in saline (expressed as percent changes from baseline) was significantly higher than CBF response to iontophoresis of pure saline (maximum response: 360 ± 51% versus 172 ± 42%, respectively; P < 0.001, ANOVA for repeated measures). The maximum “net” CBF response to insulin (response to insulin minus response to saline) showed a negative correlation ( r = –0.361; P < 0.01) with age in HS, and resulted significantly lower in the oldest than in the youngest HS (105 ± 40% versus 307 ± 45%, respectively; P < 0.01). No significant correlation was observed between the maximum CBF response to saline and the age of subjects. In NIDDM patients the “net” CBF response to insulin iontophoresis resulted significantly lower than in 15 sex- and age-matched control subjects (maximum response: –50 ± 89% versus 201 ± 81%, respectively; P < 0.001, ANOVA for repeated measures). No significant difference was observed between diabetics and controls, nor in basal perfusion (6.5 ± 1.3 IU versus 6.8 ± 1.7 IU, respectively) neither in the skin postischemic hyperemia (250 ±14% versus 258 ± 27%, respectively). These results confirm that insulin iontophoresis induces a skin vasodilatatory effect in normal subjects and show that this effect is reduced by aging and is absent in treated NIDDM patients. The local skin vasodilatatory effect induced by insulin seems to involve mechanisms different from those underlying the skin postischemic hyperemia.

Novel, high-amplitude blood-flow oscillations in vasodilating human skin

While investigating cutaneous perfusion during rewarming from cold-water immersion (18 °C), we observed high-amplitude oscillations in skin blood flow. This novel phenomenon occurred during whole-body heating (40 °C) with, and without, β -adrenergic blockade, but was not present during basal thermoneutral conditions (28 °C). Blood-flow oscillations (∼0.4 Hz), spanning ∼700–800 ms were observed during both rewarming phases, and were comprised of high-amplitude peaks (∼1500 AU) arising from a stable baseline (∼200 AU). Propranolol treatment had no effect on these oscillations. A second experiment was conducted to determine whether pre-cooling was essential to the induction of such oscillations. Herein we provide the first description of these novel oscillations. We hypothesise that these oscillations were influenced by variations in core and skin temperatures, and we are currently exploring the control mechanisms and the physiological significance of these high-amplitude oscillations.

Neuromuscular electric stimulation enhances endothelial vascular control and hemodynamic function in paretic upper extremities of patients with stroke

Wang J-S, Chen S-Y, Lan C, Wong M-K, Lai J-S. Neuromuscular electric stimulation enhances endothelial vascular control and hemodynamic function in paretic upper extremities of patients with stroke. Arch Phys Med Rehabil 2004;85:1112-6. Objective To investigate the effects of neuromuscular electric stimulation (NMES) on endothelial vascular control and hemodynamic function in patients in rehabilitation after acute stroke. Design Before-after trial. Setting Inpatients in a tertiary hospital. Participants Sixteen stroke patients (11 women, 5 men) with a mean age of 60.6±19.5 years. Interventions All patients received NMES for paretic wrist extensor and flexor muscles 30 minutes daily, 5 days a week, for 4 weeks. The nonparetic upper extremities, which served as controls, did not receive NMES. Main outcome measures Laser Doppler perfusion testing was conducted to measure cutaneous microcirculatory reponses to transdermal iontophoresis of acetylcholine (ACh) and sodium nitroprusside (SNP), as specific endothelium-dependent and -independent vasodilators, respectively. Arterial and venous hemodynamic function was also measured by impedance plethysmography. Results Before NMES treatment, the venous capacity and compliance of the paretic extremities did not differ significantly from those of the nonparetic extremities. However, hyperemic arterial inflow, ACh-induced cutaneous perfusion, and the ratio of ACh- to SNP-induced cutaneous perfusion were lower in the paretic than in the nonparetic extremities. After NMES treatment, hyperemic arterial inflow and venous outflow increased by 21.5% and 57.2%, respectively, in the paretic extremities ( P<.05). ACh-induced cutaneous perfusion and the ratio of ACh- to SNP-induced cutaneous perfusion were also significantly enhanced in the paretic extremities. In contrast, hyperemic arterial inflow decreased by 39.6% in the nonparetic extremities ( P<.05), and endothelium-dependent cutaneous vasodilation also decreased significantly. Conclusions NMES therapy may enhance the hyperemic arterial response and endothelium-dependent dilation in skin vasculature in the paretic upper extremities of patients with stroke.

Hysteresis of heart rate and heat exchange of fasting and postprandial savannah monitor lizards ( Varanus exanthematicus)

Reptiles are ectothermic, but regulate body temperatures ( T b) by behavioural and physiological means. Body temperature has profound effects on virtually all physiological functions. It is well known that heating occurs faster than cooling, which seems to correlate with changes in cutaneous perfusion. Increased cutaneous perfusion, and hence elevated cardiac output, during heating is reflected in an increased heart rate ( f H), and f H, at a given T b, is normally higher during heating compared to cooling (‘hysteresis of heart rate’). Digestion is associated with an increased metabolic rate. This is associated with an elevated f H and many species of reptiles also exhibited a behavioural selection of higher T b during digestion. Here, we examine whether digestion affects the rate of heating and cooling as well as the hysteresis of heart rate in savannah monitor lizards ( Varanus exanthematicus). Fasting lizards were studied after 5 days of food deprivation while digesting lizards were studied approximately 24 h after ingesting dead mice that equalled 10% of their body mass. Heart rate was measured while T b increased from 28 to 38 °C under a heat lamp and while T b decreased during a subsequent cooling phase. The lizards exhibited hysteresis of heart rate, and heating occurred faster than cooling. Feeding led to an increased f H (approximately 20 min −1 irrespective of T b), but did not affect the rate of temperature change during heating or cooling. Therefore, it is likely that the increased blood flows during digestion are distributed exclusively to visceral organs and that the thermal conductance remains unaffected by the elevated metabolic rate during digestion.

Evaluation of forearm microvascular blood flow regulation by laser Doppler flowmetry, iontophoresis, and curve analysis: contribution of axon reflex

The relative contribution of vasodilating factors to the control of blood flow in the forearm cutaneous microcirculation is not well defined. Therefore, a mathematical transformation is introduced to decompose the superimposed signal and to investigate the involved mechanisms separately. Transdermal iontophoresis was used for the delivery of acetylcholine (ACh) or sodium nitroprusside (SNP) into the forearm, and cutaneous perfusion was measured using a laser Doppler flowmeter (LDF). The curve fitting procedure used in this study indicates that the LDF signal in response to ACh iontophoresis can be described by the superposition of two independent hyperbolic response curves. Obviously, each component of LDF signal indicates the existence of a separate mechanism, with corresponding rate constant k, latency T, and the saturation level F max. Blockade of C-fiber function (axon reflex) with topical anesthesia removes one of the two components of this response and allows the precise quantification of its contribution. SNP-evoked response also has two components, but their parameters were different from those of ACh. Therefore, ACh and SNP cause vasodilation in the skin microcirculation through different pathways. These findings have implications for clinical studies that use the iontophoresis technique for assessing vascular function and comparing responses to ACh and SNP to evaluate endothelial dysfunction.

Poster 6: Complex regional pain syndrome and distal radius fractures: intermediate-term follow-up

Objective: To evaluate the impact of complex regional pain syndrome (CRPS) after distal radius fractures on function and health-related quality of life (HRQOL). Design: Retrospective and prospective clinical study. Setting: University orthopedic department. Participants: 28 patients with CRPS after distal radius fractures. Interventions: Fracture management (closed reduction, cast immobilization, external fixation, open reduction and internal fixation, percutaneous pinning) and CRPS management (autonomic nerve blocks, oral medications, hand therapy, median nerve decompression). Main Outcome Measures: Clinical findings; thermoregulatory testing (isolated cold stress testing, laser Doppler measurements of cutaneous perfusion and digital pulp temperature); and HRQOL instruments (McGill Pain Questionnaire, McCabe Cold Sensitivity Scale, Levine Symptom Severity and Functional Scale, Disabilities of Arm, Shoulder, and Hand [DASH] questionnaires, Wake Forest University Symptom Rating Scale). All 3 measures were compared at initial presentation and at a mean follow-up of 5 years. Results: At 5-year follow-up, patients with CRPS after distal radius fractures who received the active intervention showed diminished pain, improved strength, and decreased stiffness; however, numbness and cold intolerance was not improved. Conclusion: CRPS after distal radius fractures results in a significantly diminished function, HRQOL, and residual disability despite active and vigorous intervention.

The acute effect of peripheral nerve transection on digital thermoregulatory function

Purpose: This study tests the hypothesis that major peripheral nerves serve as important routes for adrenergic neural fibers and therefore peripheral nerve injury affects cutaneous perfusion within the nerve's sensory innervation territory. The specific aim of the study was to determine whether an acute isolated peripheral nerve injury would result in alteration of blood flow to a specific digit, digital pain, and/or cold sensitivity. Methods: The influence of peripheral nerves on their dominant area of autonomic vasomotor function was evaluated in 9 patients who had primary neurorrhaphy after a single complete median or ulnar nerve transection. At a mean follow-up of 47 days the response of digital perfusion to a cold stress was examined in these patients by using isolated cold stress testing and laser Doppler fluxmetry. Patients also completed subjective questionnaires to evaluate their symptoms. Results: The affected hands showed a decreased cutaneous perfusion when compared with the contralateral hands during all 3 phases of the cold stress test. In addition cutaneous perfusion patterns evaluated by laser Doppler perfusion imaging showed markedly decreased cutaneous perfusion patterns in the digits within the innervation territory of the injured nerve. There was no notable difference in digital baseline temperatures and temperature changes after an isolated cold stress test between the most affected digits of the injured hands and corresponding digits of the unaffected, contralateral hands. All 9 patients reported mild to severe digital numbness, 8 reported mild to severe pain, and 4 reported mild to moderate cold sensitivity of the upper extremity. Conclusions: This study documents that cutaneous perfusion and thermoregulatory function is altered after isolated peripheral nerve injury. (J Hand Surg 2003;28A:481-488. Copyright © 2003 by the American Society for Surgery of the Hand.)

Regulation of human cutaneous circulation evaluated by laser Doppler flowmetry, iontophoresis, and spectral analysis: importance of nitric oxide and prostaglandines

Nitric oxide (NO) and prostaglandines (PGs) are important in regulation of vascular tone and blood flow. Their contribution in human cutaneous circulation is still uncertain. We inhibited NO synthesis by infusing N G-monomethyl- l-arginine ( l-NMMA) in the brachial artery (16 μmol/min for 5 min) and reversed it by intraarterial infusion of l-arginine (40 μmol/min for 7.5 min). PG synthesis was inhibited by the cyclooxygenase inhibitor aspirin (600 mg over 5 min intravenously). Basal cutaneous perfusion and perfusion responses during iontophoresis with the endothelium-dependent vasodilator acetylcholine (ACh) and the endothelium-independent vasodilator sodium nitroprusside (SNP) were recorded by laser Doppler flowmetry (LDF). We performed wavelet transforms of the measured signals. Mean spectral amplitude within the frequency interval from 0.0095 to 1.6 Hz and mean and normalized amplitudes of five intervals around 1, 0.3, 0.1, 0.04, and 0.01 Hz were analysed. The oscillations with frequencies around 1, 0.3, 0.1, and 0.04 Hz are influenced by the heartbeat, the respiration, the intrinsic myogenic activity of vascular smooth muscle, and the neurogenic activity of the vessel wall, respectively. We have previously shown that the oscillation with a frequency around 0.01 Hz is modulated by the vascular endothelium. l-NMMA reduced mean value of the LDF signal by ≈20% ( P = 0.0067). This reduction was reversed by l-arginine. Mean value of the LDF signals during ACh and SNP iontophoresis did not change after infusion of l-NMMA. Aspirin did not affect mean value of the LDF signal or the LDF signal during ACh or SNP iontophoresis. Before interventions the only significant difference between the effects of ACh and SNP was observed in the frequency around 0.01 Hz, where ACh increased normalized amplitude to a greater extent than SNP. l-NMMA abolished this difference, whereas it reappeared after infusion of l-arginine ( P = 0.0084). Aspirin did not affect this difference ( P = 0.006). We conclude that basal cutaneous blood flow and the endothelial dependency of the oscillation around 0.01 Hz are partly mediated by NO, but not by endogenous PGs. Other aspects of human cutaneous circulation studied are not regulated by NO or PGs.

Vascular and neural mechanisms of ACh-mediated vasodilation in the forearm cutaneous microcirculation.

The relative contribution of endothelial vasodilating factors to acetylcholine (ACh)-mediated vasodilation in the forearm cutaneous microcirculation is unclear. The aims of this study were to investigate the contributions of prostanoids and cutaneous C fibers to basal cutaneous blood flow (CuBF) and ACh-mediated vasodilation. ACh was iontophoresed into the forearm, and cutaneous perfusion was measured by laser-Doppler flowmetry. To inhibit the production of prostanoids, four doses of acetylsalicylic acid (ASA; 81, 648, 972, and 1,944 mg) were administered orally. Cutaneous nerve fibers were blocked with topical anesthesia. Cyclooxygenase inhibition did not change basal CuBF or endothelium-mediated vasodilation to ACh. In contrast, ASA (972 and 1,944 mg) significantly reduced the C-fiber-mediated axon reflex in a dose-dependent fashion. Blockade of C-fiber function significantly reduced axon reflex-mediated vasodilation but did not affect basal CuBF or endothelium-dependent vasodilation. The findings suggest that prostanoids do not contribute significantly to basal CuBF or endothelium-dependent vasodilation in the forearm microcirculation. In contrast, prostanoids are mediators of the ACh-provoked axon reflex.

Fractal dimensions of laser doppler flowmetry time series

Laser Doppler flowmetry (LDF) provides a non-invasive method of assessing cutaneous perfusion. As the microvasculature under the probe is not defined the measured flux cannot be given absolute units, but the technique has nevertheless proved valuable for assessing relative changes in perfusion in response to physiological stress. LDF signals normally show pronounced temporal variability, both as a consequence of the pulsatile nature of blood flow and local changes in dynamic vasomotor activity. The aim of the present study was to investigate the use of methods of nonlinear analysis in characterizing temporal fluctuations in LDF signals. Data were collected under standardised conditions from the forearm of 16 normal subjects at rest, during exercise and on recovery. Surrogate data was then generated from the original time series by phase randomization. Dispersional analysis demonstrated that the LDF data was fractal with two distinct scaling regions, thus allowing the calculation of a fractal dimension which decreased significantly from 1.23 ± 0.09 to 1.04 ± 0.02 during exercise. By contrast, dispersional analysis of the surrogate data showed no scaling region.

Évaluation des modifications radio-induites tardives de la microcirculation superficielle après irradiation aiguë β.II. Intérêt pronostique du laser doppler cutané

Objective. – The changes that occur in the tissular microcirculation after accidental acute irradiation account for some of the early effects of such irradiation, especially at the cutaneous level. The prognostic importance of the cutaneous laser doppler was tested in an experimental model of acute β-irradiation. Methods. – Ten pigs were given β-irradiation with a high single localized dose of 90Sr/ 90Y (32 or 64 Gy, 7 mg/cm 2) delivered to the flank, and were evaluated 2, 7, 14, 21 and 28 days thereafter. Each individual was its own control. The local microcirculation was measured in the resting state and during thermal stimulation at 42° C, using a Periflux® cutaneous Doppler laser with p413® probes. Three periods of six minutes each were continuously recorded: period 1 (P1) represented basal resting cutaneous perfusion, with the slope p corresponding to the increase in perfusion when two minutes of thermal stimulation at 42° C began; P2 to plateau perfusion during this stimulation; and P3 to perfusion on the return to equilibrium. Results. – After acute β-irradiation in the pig, all the cutaneous microcirculation parameters measured (P1, p, P2 and P3) had risen at day 2 in the irradiated area by a factor of 2 to 4, depending on the dose ( p < 0.001), compared to the adjacent control area. On the other hand, as from day 7, the resting and the stimulated microcirculation varied little, except for a reduction of the slope p by a factor of 2 ( p < 0.05) after the strongest radiation dose. Conclusion. – After acute irradiation, the increase in the resting cutaneous microcirculation may correspond to immediate but transitory capillary vasodilatation that accompanies the initial erythema in accidental irradiation. The absence of vascular response to thermal stimulation seems to be a good means of reaching an early diagnosis of delayed cutaneous radiation necrosis.