Skin Blood Flux Research Articles

Pulmonary and systemic effects of inhaled PACAP38 in healthy male subjects

Pituitary adenylate cyclase activating polypeptide 1-38 (PACAP38) displays biological activities (e.g. bronchodilatory, pulmonary vasodilatory and anti-inflammatory properties) that are relevant in several pulmonary diseases. The aim of this study was to assess the safety and tolerability and the pulmonary and systemic effects of inhaled PACAP38 in humans. Twelve healthy male subjects (mean age 28) were studied in a randomized, double-blind, placebo-controlled dose escalation trial with inhalation of PACAP38 to a cumulative dose of 480 microg. Lung function was measured by body plethysmography. Systemic absorption was evaluated by plasma levels, skin blood flux (estimated by laser Doppler imager fluxmetry) and systemic haemodynamics. Inhalation of PACAP38 did not cause relevant adverse reactions or an increase of PACAP38 plasma levels. No statistically significant changes in lung function tests and no systemic effects (blood pressure, pulse rate or skin blood flux) occurred. Inhaled PACAP38 was well tolerated without systemic side-effects in healthy male subjects.

Cutaneous Endothelial Dependent and Independent Vascular Responsiveness after Prolonged Head-Down Bed Rest

Spaceflight, or its ground based analog head-down bed rest (HDBR), reduces the elevation in skin blood flow to whole-body and local heating. The mechanisms that underlie these microgravity-related changes are unclear and may be related to altered cutaneous post-synaptic function (i.e., decreased sensitivity to vasodilator neurotransmitters and co-factors). PURPOSE: Test the hypothesis that HDBR alters post-synaptic cutaneous vascular responsiveness to endothelial-dependent and independent vasodilators. METHODS: Intradermal microdialysis membranes were placed in forearm skin of seven healthy subjects (5 males, 2 females) before and, in a randomised fashion, on day 16 or 18 of 6° HDBR, thereby allowing local delivery of the endothelial-dependent vasodilator, acetylcholine (ACh; 1x10-7 to 1x10-1 M at 10-fold increments) and the endothelial-independent nitric oxide donor, sodium nitroprusside (SNP; 5x10-8 to 5x10-2 M at 10-fold increments). Local skin temperature was clamped at 34 °C throughout the protocols. Cutaneous vascular conductance (CVC) was calculated from the ratio of laser-Doppler derived skin blood flux (assessed directly over the membranes) to mean arterial blood pressure. CVC dose-response curves to ACh and SNP were modeled via nonlinear regression curve fitting to identify the dose of ACh and SNP causing 50% of the maximal vasodilator response (EC50), used as an index of cutaneous vascular responsiveness. RESULTS: The EC50 of the ACh dose response curve was unchanged after HDBR (pre-HDBR: −3.71 ± 0.35 vs post HDBR: −3.82 ± 0.64 log M, P = 0.88) as was the EC50 of the SNP dose response curve (pre-HDBR: −3.98 ± 0.25 vs post HDBR: −4.37 ± 0.33 log M, P = 0.30). CONCLUSIONS: HDBR does not affect post-synaptic cutaneous endothelial dependent and independent responsiveness, as indexed by the EC50 of the assessed dose-response curves. Given these findings, reduced increases in skin blood flow during whole-body and local heating after HDBR are unlikely to be due to impaired endothelial dependent and independent vasodilator responsiveness. This research project was funded by grants from the National Heart, Lung and Blood Institute (HL-61388, HL-67422, HL-84072, GM-68865).

Carotid baroreceptor stimulation alters cutaneous vascular conductance during whole‐body heating in humans

Prior studies investigating carotid baroreflex control of the cutaneous vasculature have yielded mixed findings. However, previously used methodological and analytical techniques may limit the ability to detect carotid baroreflex-mediated changes in cutaneous vascular conductance (CVC). The aim of this study was to test the hypothesis that dynamic carotid baroreceptor stimulation (i.e. 5 s trials) using neck pressure (NP, simulated carotid hypotension) and neck suction (NS, simulated carotid hypertension) will decrease and increase CVC, respectively, during normothermic and whole-body heating conditions in resting humans. Data were obtained from nine subjects (age, 31 +/- 2 year). The ratio of forearm skin blood flux (laser-Doppler flowmetry) and arterial blood pressure (Finapres) was used as an index of CVC. Multiple 5 s trials of NP (+40(Torr)) and NS (-60(Torr)), as well as breath-hold/airflow control trials, were applied during end-expiratory breath-holds while subjects were normotheric and heat stressed (change in core temperature approximately 0.75 degrees C). CVC responses to each NP and NS trial were averaged into 1 s intervals during the following periods: 3 s prestimulus, 5 s during stimulus, and 5 s poststimulus. Peak CVC responses (3 s average) to NP and NS were compared to prestimulus values using paired t test. During normothermia, NP decreased CVC by 0.032 +/- 0.007 arbitrary units (a.u.) mmHg(-1); (P < 0.05); however, breath-hold/airflow control trials resulted in similar decreases in CVC. NS did not change CVC (Delta = 0.002 +/- 0.005 a.u. mmHg(-1); P = 0.63). During whole-body heating, NP decreased CVC (by 0.16 +/- 0.04 a.u. mmHg(-1); (P < 0.05), whereas NS increased CVC by 0.07 +/- 0.03 a.u. mmHg(-1); (P < 0.05). Furthermore, these changes were greater than, or directionally different from, the breath-hold/airflow control trials. These findings indicate that carotid baroreceptor stimulation elicits dynamic changes in CVC and that these changes are more apparent during whole-body heating.

EVALUATION OF ACUPUNCTURE WEIGHT LOSS PROGRAMME USING LASER DOPPLER PERFUSION IMAGING

Recent development of non-invasive and remote sensing modalities such as the Laser Doppler Perfusion Imager (LDPI) technology for probing the skin blood perfusion and its spatial variability over a region of interest, allows for detailed analysis of alterations in skin blood perfusion, with virtually no disturbance of the microcirculation under study. In this study, we have investigated perfusion flux pattern changes obtained from the abdominal area of 30 Chinese male patients (mean age of 26, presented only 2 typical cases) undergoing an acupuncture slimming course. The objective was to study the alterations in skin blood flux by detailed analysis of the Doppler images taken before, during which and after the insertion of needles. We explained the correlation of alterations of skin blood flux with the flow of Qi and the losses of body weight and body fat content. The purpose was to quantify a relationship between changes in perfusion flux pattern and the efficacy of weight loss through acupuncture. In conclusion, this study affirmed that skin blood perfusion flux values in the abdominal area were the highest, whilst the acupuncture needles were inserted. There is also evidence that the increased flux values occurred along the meridian channels of acupuncture, thereby acknowledging the flow of Qi in them. Hence, further clinical studies in the use of LDPI to investigate acupuncture with more subjects are warranted.

Hemodynamic effects of intermittent pneumatic compression in patients with critical limb ischemia

Traditional teaching assumes that the distal arterial tree is maximally dilated in patients with critical limb ischemia (CLI). Endovascular or arterial bypass procedures are the commonly used interventions to increase distal perfusion. However, other forms of treatment such as spinal cord stimulation or intermittent pneumatic compression (IPC) have been shown to improve limb salvage rates. This prospective study was designed to determine if the use of IPC increases popliteal, gastrocnemial, collateral arterial, and skin blood flow in patients with CLI. Twenty limbs with CLI in 20 patients (mean age, 74 years) were evaluated with duplex ultrasound scans and laser Doppler fluxmetry in the semi-erect position before, during, and after IPC. One pneumatic cuff was applied on the foot and the other on the calf. The maximum inflation pressure was 120 mm Hg and was applied for 3 seconds at three cycles per minute. All patients had at least two-level disease by arteriography. Fourteen limbs were characterized as inoperable, and six were considered marginal for reconstruction. Flow volumes were measured in the popliteal, medial gastrocnemial, and a genicular collateral artery. Skin blood flux was measured on the dorsum of the foot at the same time. Significant flow increase during the application of IPC was found in all three arteries (18/20 limbs) compared with baseline values (P < .02). The highest change was seen in the popliteal, followed by the gastrocnemial and the collateral artery. After the cessation of IPC, the flow returned to baseline. This was attributed to the elevation of time average velocity, as the diameter of the arteries remained unchanged. The skin blood flux increased significantly as well (P < .03). In the two limbs without an increase in the arterial or skin blood flow, significant popliteal vein reflux was found. Both limbs were amputated shortly after. IPC increases axial, muscular, collateral, and skin blood flow in patients with CLI and may be beneficial to those who are not candidates for revascularization. Patients with significant venous reflux may not benefit from IPC. This supports the theory that one of the mechanisms by which IPC enhances flow is by increasing the arteriovenous pressure gradient.

Cutaneous Vascular Conductance Is Not Altered By Carotid Baroreceptor Stimulation

Electrical stimulation of the carotid sinus nerve failed to elicit reproducible changes in skin sympathetic nerve activity. Furthermore, average cutaneous vascular conductance (CVC) at the end of 3 minutes of repeated 300ms R-wave triggered carotid baroreceptor stimulation was unchanged compared to a pre-stimulus period. However, it remains unknown whether longer duration (5sec) carotid baroreceptor stimulation modulates CVC. PURPOSE To test the hypothesis that unloading of the carotid baroreceptors via repetitive square-wave neck pressure (NP) alters CVC in normothermic resting humans. METHODS In six subjects (age, 27±2), integrated laser Doppler flowmeter probes were attached to the skin at the mid-thigh. CVC was identified from the ratio of skin blood flux and arterial blood pressure. NP (+40 Torr) was applied in trains of 5sec NP followed by 5sec release of NP, repeatedly for 5 minutes. The resulting peaks and valleys in arterial blood pressure and CVC for each 10sec train (i.e. CVC at the blood pressure peaks and CVC at blood pressure valleys) were identified and statistically compared using a paired t-test. RESULTS Increases (108±10 mmHg) and decreases (96±12 mmHg) in mean arterial pressure in response to NP, were significantly different (P < 0.05). However, calculated CVC was not different when blood pressure was elevated (0.10±0.05 CVC units) relative to when blood pressure was reduced (0.09±0.01 CVC units; P=0.08). The absence of a change in CVC indicates the cutaneous vasculature is not responsive to carotid baroreceptor unloading when these values are assessed dynamically during fluctuations in arterial blood pressure. CONCLUSION These findings confirm prior observations that the carotid baroreflex does not exhibit control of skin blood flow in resting normothermic humans.

Microcirculatory changes parallel the clinical deterioration of chronic venous insufficiency

Objective: This study was designed to determine microcirculatory changes in patients belonging to different chronic venous insufficiency (CVI) classes. Methods: A total of 80 patients from all CVI classes and 15 symptom-free volunteers were studied prospectively. Venous reflux was verified with duplex scanning. Patients with conditions that may have affected the local microcirculation were excluded. Skin blood flux (SBF) was measured using a laser Doppler flowmeter in the supine position in a constant room temperature of 22°C and after 10 minutes acclimatization. The veno-arteriolar response (VAR) was estimated from the SBF change from supine to dependent position. The vasomotor activity (VMA) was determined from the baseline SBF.The amplitude of cycles (AC) and SBF during heat stress at 45°C were also measured. Results: Mean age, duration of disease and prevalence of deep vein thrombosis were greater in classes 4-6 compared with classes 1-3 ( P &lt;0.02). Although there was an increase in SBF and AC in classes 2 and 3 compared with the controls this was not significant. Values for SBF and AC were higher in classes 4-6 than classes 1-3 ( P &lt;0.01), and higher in class 6 than class 4 ( P &lt;0.01). Upon heating, the SBF increased more in classes 1-3 than in classes 4-6 ( P &lt;0.01), and in class 4 more than in class 6 ( P &lt;0.01). Values for VAR and VMA decreased with worsening of CVI, but these changes were not significant. Conclusions: Deterioration of the microcirculation is largely responsible for the clinical symptoms and signs seen in patients with CVI classes 4-6.

Dependence of human forearm skin postocclusive reactive hyperemia on occlusion time

Introduction: Human postocclusive forearm skin reactive hyperemia is not only a potential means of identifying early signs of cardiovascular diseases, it can also be used in the assessment of local microvascular response to topically applied compounds on skin. The method is not fully characterized. In this study, we investigated the influence of occlusion time on postocclusive forearm skin reactive hyperemia using laser Doppler fluximetry (LDF). Methods: Twenty healthy male volunteers were studied on three separate days (at least 24 h apart) via a randomized design. Volunteers were studied in a supine position while fasted. Laser Doppler probes were placed on the volar surface of the antebrachium. In preliminary studies, 3 min of upper arm blood flow occlusion at suprasystolic pressure was found to be the upper limit of tolerability. Subsequently, volunteers were randomized to receive 1, 2, or 3 min occlusion on 3 different days. Skin blood flux was measured before, during, and after occlusion using LDF. The primary outcome calculated was maximal change in skin blood flux before and after occlusion, expressed in arbitrary units (AU). Results: Skin blood flux changes (mean±S.E.M.) after 1, 2, and 3 min occlusion period were 15.39±1.27 AU, 24.84±1.62 AU, and 32.14±1.73 AU, respectively. Using repeated-measures analysis of variance (ANOVA), significant difference ( P<.05) in skin blood flux changes were revealed between these three occlusion durations, where 3 min occlusion produced significantly greater in skin blood flux occlusion change compared to 1 and 2 min occlusion. Discussion: Three minutes of occlusion produces the greater postocclusive reactive hyperemia. It is recommended that studies using postocclusive forearm skin reactive hyperemia should occlude the forearm for at least 3 min.

Recovery of nitric oxide from acetylcholine-mediated vasodilatation in human skin in vivo.

To investigate the relative contribution of nitric oxide (NO) to the vascular and neural mechanisms underlying the ACh-induced vasodilatation in human skin. ACh was delivered to the skin of the forearm of 28 healthy volunteers using intradermal microdialysis. Subsequent changes in tissue levels of NO and histamine were measured in the dialysate outflow and the associated changes in skin blood flux followed with the use of scanning laser Doppler imaging. ACh caused a dose-dependent increase in skin blood flux measured directly above the probe, associated with a twofold increase in dialysate NO. L-NAME (5 mM) delivered simultaneously via the dialysis probe totally blocked the increase in dialysate NO but only partially attenuated (approximately 30%) the ACh-induced increase in blood flux. At concentrations > or =6.25 mM, ACh also induced a widespread flare response, up to 40 mm in width, accompanied by the sensation of itch. The flare was not blocked by L-NAME or the H1 receptor antagonist levocetirizine, but was reduced by C-fiber blockade. Dialysate histamine levels remained unchanged at all times. These experiments offer further insight into the use of dialysis as an experimental technique in the skin. They provide direct evidence that the skin microvascular response to ACh is only partially mediated by NO. Further they suggest that ACh at higher concentrations can induce an axon-reflex-mediated response that is independent of NO release at the site of dermal provocation or of local histamine release.

The effect of polyneuropathy on foot microcirculation in Type II diabetes.

The aim of this study was to investigate the influence of peripheral polyneuropathy (PNP) on skin microcirculation and foot swelling rate in the feet of patients with Type II (non-insulin-dependent) diabetes mellitus. 38 Type II diabetic patients, 24 with PNP (PNP+), 14 without PNP (PNP-), and 16 healthy control subjects were studied, first supine and subsequently sitting with the foot dependent for 50 mn. In patients with PNP, foot skin temperature was higher, (p<0.04) and capillary blood cell velocity (CBV, nailfold capillary microscopy), was lower compared to patients without PNP (222 vs 313 micro m/s respectively, p<0.03). Compared to the control subjects, the percentage reduction in skin blood flux, (LDF, laser-Doppler fluxmetry), after 10 min was higher in the PNP- and PNP+ patients (3% vs 18% and 26% respectively, p<0.02). These disturbances were most pronounced in PNP+ patients with a history of a foot ulcer. Foot swelling rate (mercury strain gauge plethysmography) in the first 10 min of dependency, was lower in patients with PNP+ compared to the control subjects (0.00165 vs 0.00286 ml.100 ml(-1)s respectively, p<0.01). In addition, we found a negative correlation (r=-0.41; p<0.01) between Valk-score (severity of PNP) and FSR. Type II diabetes PNP is associated with multiple abnormalities in the (skin) microcirculation of the foot, characterised by reduced capillary blood flow, an enhanced reduction in skin blood flux and impaired fluid filtration after sitting up. The most severe abnormalities were observed in patients with a history of foot ulceration.

Development of Vasomotor Control in Lean (+/?) and Genetically Obese ( fa/fa) Rat Pups

DÖRING, H., H. SANN AND I. SCHMIDT. Development of vasomotor control in lean (+/?) and genetically obese (fa/fa) rat pups. PHYSIOL BEHAV 66(2) 303–308, 1999.—Using laser Doppler flowmetry, we determined whether vasomotor control is already functional in 7-, 11-, and 16-day-old rat pups, and whether differences in vasomotor responses between 16-day-old lean (+/?) and fatty ( fa/fa) pups occur. For 3 h, at the end of their daily light phase, the pups were exposed to 30-min step changes of ambient temperature ( T a) alternating between thermoneutrality and cold loads resulting in a 50–100% increase of metabolic rate (MR) above its thermoneutral value, while core temperature ( T c), skin blood flux at the hindpaw, and MR were recorded. In all age groups, blood flux changed significantly in response to these T a changes. The time needed for a significant change in blood flux was shorter in the 7-day-old than in the 16-day-old lean pups, while the T a dependency of T c was more pronounced in the younger pups. Comparison of the responses of the 16-day-old fatty and lean pups showed a parallel shift to lower values in the correlation of T a with MR in the fa/fa pups, but no difference in the correlation of T a with blood flux. This demonstrates that the vasomotor control system in the rat is already functional by the age of 7 days, and that the fa/fa lesion influences the vasomotor control less than the metabolic cold defense.

Elastotic degenerative change and yellowish discolouration in photoaged skin.

One clinical sign of photodamage is a sallow discolouration of the skin, and solar elastotic degenerative change in the upper dermis may cause this change. We have attempted to quantify these phenomena and relate them to each other and to age. Twenty-seven healthy volunteers (age 18 to 61 years) were recruited. We examined the back of the hand of photodamaged individuals and the inner upper arm to demonstrate changes due to ageing. Each site was assessed for cutaneous blood flux using a laser Doppler fluxmeter (PF4000, Perimed UK), and for melanin pigmentation using a Melanin Index meter (Dermotronics Ltd, Cardiff, UK). Skin colour was measured using a diode array spectrophotometer (MCPD-1000, Photal, Japan), which computes CIE coordinates L*, a*, b*. Biopsies from each site were obtained from 13 of the subjects and were processed and stained with Gomori's aldehyde fuchsin. The percentage area of elastic staining material in the dermis was measured using image analysis. Sections were measured in four bands of 200 micron depth, and four fields were measured per band. Neither melanin content nor skin blood flux correlated with age for either skin site. Percentage area of elastosis correlated with age on the exposed site from the uppermost 600 microns of the dermis, (<200 micron depth, r=0.74, P<0.01, 200<depth<400, r=0.57, P<0.05; 400<depth<600, r=0.57, P<0.05). No correlation was found on the unexposed inner upper arm site. On the back of hand site, a linear relationship was found between a parameter derived from the L*, a*, b* coordinates of (b*-5a*) and both age (r=0.904, P<0.001) and percentage area of elastosis of the uppermost 200 microns of dermis (r=0.74, P<0.01). This was not seen for the inner upper arm site. On exposed sites, the coefficient (b*-5a*) correlates with solar elastosis and these both correlate with age, which is related to exposure. This data confirms that solar elastosis accounts for the yellowish discolouration of sun damaged skin, and suggests that the coefficient b*-5a* could be used for the non-invasive quantification of solar elastosis.

Laser Doppler skin blood flux dynamics in chronic venous insufficiency

Laser Doppler skin blood flux dynamics in chronic venous insufficiency

Effect of maximal arm exercise on skin blood flux in the paralyzed lower limbs in persons with spinal cord injury.

The purpose of the present study was to examine the effect of maximal arm exercise on the skin blood circulation of the paralyzed lower limbs in persons with spinal cord injury (PSCI). Eight male PSCI with complete lesions located between T3 and L1 performed graded maximal arm-cranking exercise (MACE) to exhaustion. The skin blood flux at the thigh (SBFT) and that at the calf (SBFC) were monitored using laser-Doppler flowmeter at rest and for 15 s immediately after the MACE. The subject's mean peak oxygen uptake and peak heart rate was 1.41 +/- 0.22 l.min-1 and 171.6 +/- 19.2 beats.min-1, respectively. No PSCI showed any increase in either SBFT or SBFC after the MACE, when compared with the values at rest. These results suggest that the blood circulation of the skin in the paralyzed lower limbs in PSCI is unaffected by the MACE.

Effect of maximal arm exercise on skin blood flux in the paralyzed lower limbs in persons with spinal cord injury

Effect of maximal arm exercise on skin blood flux in the paralyzed lower limbs in persons with spinal cord injury

Microcirculation in the footsole as a function of mechanical pressure

Objective. In this study an experimental set-up for measuring skin microvascular responses of the footsole to changes in externally applied pressure was analysed. Design. A clinical study. Skin microvascular blood flow was measured in healthy volunteers, during and after external mechanical pressure of different magnitudes. Background. During standing and walking the footsole is commonly exposed to high static and dynamic mechanical pressure, resulting in changes in the microcirculation of the footsole. In diabetic patients a disturbed interaction between externally applied pressure and skin microvascular response seems to be involved in the development of a foot ulcer. Methods. Eleven volunteers participated in the study. Static loads were applied to the heel part of the footsole with the person in a supine position. Contact pressure and skin blood flux, based on the laser Doppler technique, were simultaneously monitored. The pressure used was varied in five discrete steps between 10 and 160 kPa and applied during a period of 5 min each. The microcirculation was measured during as well as after pressure loading. Results. Pressures of 40 kPa and higher do stop the blood flow in the skin micro-circulation. Releasing the applied pressure resulted in a hyperaemic response. This response appears to increase in amplitude at increasing pressures up to 800% of the baseline laser Doppler fluxmetry level. Beyond a pressure level of 80 kPa the hyperaemic response seems not to be influenced by the pressure level. The time needed to achieve the maximal laser Doppler fluxmetry level decreased when the pressure was raised from 10 to 80 kPa, but increased again when higher pressures were applied ( P = 0.051). An intra-individual variation of 11–50% was observed for the parameters describing the blood flux before, during, and after pressure application. Conclusion. Simultaneously measuring changes in contact pressure and laser Doppler flux of the footsole is a useful method to study the interaction of external mechanical pressure and skin microvascular reactions. Pressures above 40 kPa stop skin microvascular blood flow. Releasing the applied pressure results in a hyperaemic response, which increases when the applied pressure increases from 40 to 80 kPa. Higher pressures do not influence the amplitude in skin microvascular response, but result in a longer delay to maximal hyperaemia.

Effects of Monoionic and Nonionic Radiographic Contrast Media on Cutaneous Microcirculation in Patients with Peripheral Arterial Occlusive Disease

The purpose of the study was to compare the in vivo effects of two low-osmolar radiographic contrast media, a monoionic (sodium/-meglumine ioxaglate, Hexabrix) and a nonionic one (iopromide, Ultravist 300) on the cutaneous microcirculation in patients with peripheral arterial occlusive disease in a prospective randomised double-blind study. In 20 patients with peripheral arterial occlusive disease scheduled for percutaneous transluminal angioplasty skin microcirculation was assessed by laser Doppler fluxmetry and transcutaneous oxygen tension measurements at the foot dorsum for continuous recordings of the cutaneous microvascular perfusion and skin oxygenation. Before angioplasty 10 ml nondiluted contrast medium was injected intraarterially and the acute effect on transcutaneous oxygen tension and laser Doppler flux was registered. Mean laser Doppler flux and oxygen tension were evaluated initially, after arterial puncture and after contrast medium injection. In addition, flux motion was analysed with respect to frequency and amplitudes changes. No significant changes in laser Doppler flux and fluxmotion patterns were found between both groups after contrast medium injection. However, mean transcutaneous oxygen tension of the patients receiving monoionic ioxaglate dropped significantly (P = 0.01). The differences of both contrast media on red blood cell aggregation shown in vitro do not correlate to intravital microcirculatory measurements in patients with arterial occlusive disease of the lower limb. Microvascular skin blood flow and flux motion at the foot in these patients do not change significantly after intraarterial injection of ioxaglate and iopromide. However, oxygen supply of the skin is transient impaired after interarterial injection of the anionic contrast agent ioxaglate, which was not associated with clinical symptoms.

Simultaneous assessment of muscle and skin blood fluxes with the laser-Doppler technique.

The laser-Doppler technique was used to assess local muscle and skin blood fluxes at the lower limb in 20 healthy volunteers. After puncturing the anterior tibial muscle with a steel cannula, a single-fibre probe with a diameter of 0.5 mm was inserted into the muscle. Simultaneously, the skin blood flux was measured at calf and foot. The muscle blood flux at rest was 3.5 to 4 times higher than the skin blood flux at calf or foot. The spatial variability of the muscle blood flux at three different sites of measurement was considerable and tended to be higher than in the skin of the calf. After an arterial occlusion lasting 3 min, peak flux was reached in the muscle after 18.7 +/- 9.8 s, in the skin of the calf after 16.8 +/- 9.3 s, and in the skin of the foot after 22.9 +/- 14.6 s (NS). The relative flux increase during reactive hyperaemia was significantly lower in the muscle (2.7 +/- 1.3) than in the skin of the calf (3.9 +/- 1.9; p<0.05) or the foot (5.1 +/- 3.5; p<0.005). The reproducibility of reactive hyperaemia response in muscle was excellent with unchanged probe position, but exhibited a marked variability on different days. The laser-Doppler technique provides the possibility for simultaneous measurement of flow dynamics in muscle and skin with a high temporal resolution. Methodological problems include differences in probe geometry of the single-fibre compared to standard probes and differences in optical properties of the tissues. Direct comparison of flux values may, therefore, be subject to criticism, but not the comparative analysis of relative flux changes. The influence of tissue trauma on muscle blood flux has to be considered for the analysis of flux data.

Local blood flux in skin and muscle during voluntary hyperventilation in healthy controls and patients with hyperventilation syndrome.

Laser Doppler fluxmetry was used to analyze local blood flux in the anterior tibial muscle and the skin of the calf simultaneously during 3 min of hyperventilation. Examinations were performed in 10 controls and 10 patients with a hyperventilation syndrome in order to evaluate a possible different vascular response to the provocation test. During hyperventilation, mean muscle blood flux increased in both groups. In controls, flux augmented from 23.4 +/- 12.3 arbitrary units (AU) to 51.6 +/- 28.3 AU (p < 0.05) and in patients from 21.6 +/- 10.8 AU to 45.0 +/- 26.4 AU (p < 0.05). The changes of skin blood flux during hyperventilation were not significant. The flux response did not differ significantly in controls and patients. Using the laser Doppler technique we were able to confirm muscular vasodilatation previously reported during short-term hyperventilation. Possible mechanisms include release of vasoactive substances and/or a stimulation of the autonomic nervous system.

Skin Flux and Histology in Venous Hypertension

Skin blood flux and the venoarteriolar response have been studied by laser- Doppler flowmetry (LDF) in 20 postphlebitic limbs and in 20 normal limbs. Histology was also studied with punch biopsy specimens in postphlebitic limbs and in 4 randomly selected, normal volunteers. Skin flux was increased and the venoarteriolar response decreased in all postphlebitic limbs. Also in all patients an apparent increase in the number of capillaries was observed. They appeared dilated and tortuous, and the thick ened capillary wall was surrounded by a pericapillary halo composed of pro tein, neutral polysaccharides, hemosiderin, and fibrin. In conclusion, measurements with LDF differentiate between normal and postphlebitic limbs, corresponding to the histologic finding of an altered capil lary system. Therefore, LDF is useful for defining the degree of microan giopathy due to venous hypertension.