The local regulation of blood flow evaluated simultaneously by 133-xenon washout and laser Doppler flowmetry

The laser Doppler flowmeter and the 133-Xenon washout techniques of measuring cutaneous blood flow were compared for measuring the vasoconstrictor response of the hand during orthostatic maneuvres. Important discrepancies were detected for the two methods. When the hand was lowered by 40 cm a 40% decrease in blood flow was detected by the 133-Xenon method, while a 60% decrease was seen by the laser Doppler technique. Lowering the hand by 50 cm resulted in no further blood flow decrease when using the 133-Xenon method, but an 80% blood flow decrease was recorded with the laser Doppler method. A marked decrease in blood flow was recorded by the laser Doppler technique in hands that were sympathectomized or a hand that was subjected to a nerve blockade, strategies which should eliminate the orthostatic vasoconstrictor response of superficial cutaneous vessels. The 133-Xenon technique did not detect any blood flow changes in hands without sympathetic tone. We found the laser Doppler flowmetry technique unsatisfactory for measurement of blood flow changes that occur in nutritional vessels as this method measures total skin blood flow including non-capillary vessels.     

Increased subcutaneous adipose tissue blood flow in UVB-inflamed human skin. The existence of a cutaneous-subcutaneous reflex mechanism?

In 4 healthy subjects a skin area 10 mm in diameter was exposed to twice the minimal erythema dose of UVB. Subcutaneous blood flow (SBF) in the area was measured by the local 133-Xenon washout technique before and 8, 24, 48 and 72 h after induction of inflammation. Local skin temperature (TS) was monitored with electrical thermocouples. SBF gradually increased by 400% and peaked 24 to 48 h after induction of inflammation, while TS peaked after 8 h (+3 degrees C). The disparity in skin temperature and subcutaneous blood flow indicates that TS is not the governing factor in the increase in SBF. As release of inflammatory mediators from the cutis influencing the subcutis and a local effect of UVB on subcutis are unlikely, we suggest the existence of a cutaneous-subcutaneous vascular reflex mechanism as an explanation for the increased subcutaneous blood flow.     

A method for testing the effect of pressure-relieving materials in the prevention of pressure ulcers

A method is described by which the effect of pressure and relief of pressure on blood flow in cutaneous and subcutaneous tissue can be evaluated. Five normal persons were placed supine on a transparent polyacrylate board and blood flow in the skin overlying the sacral area was measured. Cutaneous blood flow was measured by the laser-Doppler technique and subcutaneous blood flow was measured by the 133Xenon washout technique using atraumatic application. Blood flow was measured by both techniques before and after relief of pressure, using the antipressure material Comfeel Pressure Relieving Dressing (in the following referred to as Comfeel PRD) consisting of a foamy plastic material with an adjustable central opening. With this material, it was possible to obtain relief of pressure which was shown as a significant increase in blood flow measured by both methods. It is suggested that the methods described should be used to test other materials as well.     

Effect of fluocinolone acetonide cream on human skin blood flow.

Blood flow rate was measured in the forearm skin of human subjects exposed to ultraviolet irradiation. Blood flow was determined by the 133Xe disappearance technique 18 hr after ultraviolet (UV) irradiation with a Westinghouse RS sunlamp held 10 inches from the skin for 10 min. Ultraviolet irradiation caused skin blood flow to increase. Application of fluocinolone acetonide cream, 0.025%, 4 times in the 16 hr following UV irradiation had no effect on either control skin blood flow or the UV-induced hyperemia.     

A time-correlation study of ultraviolet B-induced erythema measured by reflectance spectroscopy and laser Doppler flowmetry.

Ultraviolet B (UVB)-irradiated skin pigmentation was quantified using 2 objective and noninvasive techniques. Ten healthy volunteers were exposed to increasing UVB doses in the interval from 6 mJ/cm2 to 120 mJ/cm2 and the resultant vascular and pigmentary changes were evaluated using laser Doppler flowmetry (LDF) and reflectance spectroscopy (RS). Measurements were made 0.25 h, 1 h, 4 h, 8 h, 24 h, 72 h and 192 h post-irradiation. Visual scores were determined 24 h post-irradiation. Both RS and LDF revealed an early and rapid erythematous response to UVB irradiation, peaking between 8 h and 24 h, with no single UVB dose showing any significant increase until 4 h post-irradiation. LDF showed a peak increase in blood flow at 8 h post-irradiation for sites with low UVB exposure (less than or equal to 36 mJ/cm2). Doses greater than or equal to 42 mJ/cm2 showed maximal increase at 24 h. After this increase in blood flow, a slow normalization began that was not complete at 192 h post-irradiation at sites exposed to greater than or equal to 60 mJ/cm2. The present RS analysis is able to distinguish between oxygenized (OH) and deoxygenized hemoglobin (DOH). The only significant increase in DOH was found for the averaged 6 mJ/cm2 and 12 mJ/cm2 UVB dose sites 24 h after irradiation. OH peaked 24 h post-irradiation and resolution was still incomplete after 192 h. RS revealed no dose, as did the LDF, below which the vascular response peaked earlier. LDF measures dermal blood flow and RS measures hemoglobin content in the skin.(ABSTRACT TRUNCATED AT 250 WORDS)     

Evaluation of cutaneous blood flow responses by 133Xenon washout and a laser-Doppler flowmeter

A new method for noninvasive measurement of cutaneous blood flow is laser-Doppler flowmetry. The technique is based on the fact that laser light is back-scattered from the moving red blood cells, with Doppler-shifted frequencies; these impulses lead to photodetectors and are converted to flow signals. In this work we used a new system with a low noise level. Comparison was made between this technique and the atraumatic epicutaneous 133Xenon technique for measurement of cutaneous blood flow during reactive hyperemia and orthostatic pressure changes. The laser-Doppler flowmeter seems to measure blood flow in capillaries as well as in arteriovenous anastomoses, while the 133Xe method probably measures only capillary flow. A calibration of the laser-Doppler method against the 133Xe method would appear to be impossible in skin areas where arteriovenous anastomoses are present. The changes in blood flow during reactive hyperemia, orthostatic pressure changes, and venous stasis were found to be parallel as measured by the two methods in skin areas without shunt vessels. The laser-Doppler flowmeter would appear to be a useful supplement to the 133Xe washout method in cutaneous vascular physiology, but it is important to keep in mind that different parameters may be measured.     

Increased 133xenon washout from cutaneous tissue in generalized scleroderma indicates increased blood flow.

Blood flow in cutaneous tissue of the dorsum of the hand was measured by the local 133Xenon washout technique in 18 normal persons and in 26 patients suffering from generalized scleroderma of the acrosclerosis types. Flow values calculated from the accepted blood--tissue solubility coefficient (lambda) were 8.6 +/- 0.4 S.E.M. ml/100 g X min in normals and 14.5 +/- 1.1 ml/100 g X min in sclerodermic skin (i.e. increased by 69%). The difference was significant (p less than 0.001). Blood flow values in sclerodermic skin were directly proportional to the degree of dermal sclerosis. As lambda in sclerodermic skin is probably decreased due to a decreased fat content, it may not be correct to interpret these results as evidence of increased blood flow. A "worst case" was constructed in calculation of lambda using zero fat content for sclerodermic skin. Flow value was now 12.3 +/- 1.1 S.E.M. ml/100 g X min for sclerodermic skin, an increase of 43% compared with normal skin. It is probably only justified to use this "worst case lambda" in the group of severely involved cases of scleroderma. In these patients it yielded a flow value of 17.8 +/- 3.1 (N = 6) which, when compared with the flow value for normal skin, indicates an increase by 100% of the blood flow in severely involved sclerodermic skin.     

Cutaneous blood flow measurements for the detection of malignancy in pigmented skin lesions.

This work assesses cutaneous blood flow measurements as an adjunct in the differentiation between malignant and benign pigmented skin lesions. Blood flow in pigmented lesions and in their vicinity was measured by laser Doppler flowmetry (LDF), which measures the superficial skin blood flow. The lesions were then excised and histologically examined. While LDF readings for most of the benign lesions did not differ from those of control measurements, basal cell carcinomas showed a significant elevation and so did the melanomas (p less than 0.0001). Moreover, comparing the two groups of malignant lesions, namely the melanomas and basal cell carcinomas, the melanomas showed a significantly higher elevation (p less than 0.02). These results suggest that LDF may serve as an additional tool in the diagnosis of pigmented skin lesions: the probability of malignancy is low when LDF readings show no difference from adjacent normal skin; on the contrary, elevated readings suggest an increased likelihood of malignancy.     

Quantitation of microcirculatory blood flow changes in human cutaneous tissue induced by inflammatory mediators

The cutaneous microcirculation is a desirable model for pharmacologic and physiologic studies of inflammatory mediators. For exact measurements of the induced blood flow changes, two objective methods are introduced. The laser-Doppler flowmeter and the 133Xe washout technique have formerly been used for measurement of the undisturbed cutaneous blood flow. We have modified these methods to measure changes in the blood flow following intracutaneous deposition of a vasodilator, leukotriene D4. When compared with a metric estimate of the erythemal response, the two new methods were found to be more sensitive than the traditional estimate of cutaneous blood flow changes. Both methods exhibited a good sensitivity and reproducibility when applied simultaneously, although the 133Xe washout technique appeared to be able to separate interindividual differences that could not be recognized by the laser-Doppler technique. Even though the laser-Doppler technique is superior in simplicity of use, the 133Xe washout technique is recommended for exact measurements.     

Comparative quantitative analysis of ultraviolet B-induced skin blood flow change using laser Doppler perfusion imaging technique

Laser Doppler perfusion imaging (LDI), recently developed, can generate a color-coded image of tissue perfusion, making it possible to assess the spatial distribution of skin perfusion without touching the surface. Using this apparatus, we investigated ultraviolet B (UVB)-induced perfusion profile of the skin and compared the results with those obtained from laser Doppler flowmetry (LDF). Fifteen adult male Korean volunteers were irradiated with several doses of UVB ranging from 25 mJ/cm2 to 186 mJ/cm2. Twenty-four hours later, the erythema reaction was evaluated with LDF and LDI systems. There was a significant correlation between the logarithmic dose of UVB and erythema values. The curves consisted of two parts, an initial, flat phase and then a linear, steep one. Also, there was a good correlation between LDF and LDI. The LDI is as sensitive as conventional LDF, but has the many advantages of measuring blood flow over large areas without contact with the skin surface. This instrument will be useful in the measurement of skin blood flow in many areas of dermatological application.     

Assessment of erythema in irritant contact dermatitis

Assessment of erythema in experimentally-induced irritant contact dermatitis has been performed visually and using the laser Doppler flowmeter (LDF). A close correlation was shown between the 2 methods (r = 0.9079, p less than 0.001), with the LDF producing mean blood flow values which were able to discriminate between the different visual scores. Of the 100 patch tests evaluated, 3 gave poor correlations between their visual and LDF readings, including 2 dithranol reactions and 1 sodium hydroxide response. Patch tests with no visible erythema had blood flow values similar to those of normal untreated skin. Although the LDF was an easy instrument to operate, it was not considered suitable for use in the routine patch test clinic, due mainly to the unacceptable length of time required to measure each patch test.     

Preparation of liposomes from stratum corneum lipids

Cutaneous and subcutaneous blood flow (CBF, SBF) were studied in non-lesional psoriatic skin (NLS) of 10 patients with only minimal psoriatic skin manifestations, using the local 133Xe washout method. Measurements of the CBF and SBF in the NLS of the patients and 10 normal individuals yielded no statistically significant differences. The results of the present study indicate that the activity of psoriasis can be monitored by the CBF measurements in the NLS, since previously published values for CBF of NLS have shown increasing values with increasing psoriatic activity. The significance of these findings may be more evidence of humoral factors playing a role in the pathogenesis of the disease. The tissue-to-blood partition coefficient for 133Xe was calculated on the basis of biochemical estimations of the relative content of lipids, proteins, and water in skin biopsies from non-lesional skin sites of 8 psoriatic patients. The relative content of lipids, proteins, and water was normal. Thus, the normal 133Xe partition coefficient of 0.7 ml/g should be used for measurements of the CBF in NLS.     

Ultraviolet B dose-dependent inflammation in humans: a reflectance spectroscopic and laser Doppler flowmetric study using topical pharmacologic antagonists on irradiated skin.

Normal skin responds acutely to ultraviolet (UV) light exposure with complex inflammatory mechanisms. In the present study UVB irradiation ranging from subclinical erythema doses to twice the minimal erythema dose (24 mJ/cm2 to 96 mJ/cm2) was delivered to the skin of 8 volunteers. Pre-irradiated sites were immediately afterwards exposed to a 24-h occlusive patch containing 1 of 4 anti-inflammatory agents or vehicle control. The resultant change in erythema (vascular reaction) was measured objectively using laser Doppler flowmetry (LDF) and reflectance spectroscopy (RS). The 4 anti-inflammatory compounds reduced the UVB-induced vascular reactions in different and dose-dependent ways. Betamethasone-17-valerate and diphenhydramine were most effective at the 24 mJ/cm2 dose site and indomethacin and acetylsalicylic acid were more effective at sites > or = 48 mJ/cm2. Ranking the reduction in oxygenized hemoglobin (OH) content was as follows: betamethasone-17-valerate (OH reduction = 37.4%) > indomethacin (OH reduction = 21.5%) > acetylsalicylic acid (ASA) (OH decrease = 21.0%) > diphenhydramine (OH reduction = 18.4%). Using LDF, the total ranking of the cutaneous blood flow (BF) reduction was: indomethacin (BF reduction = 39.7%) > betamethasone-17-valerate (BF reduction = 32.7%) > acetylsalicylic acid (BF decrease = 17.5%) > diphenhydramine (BF reduction = 12.3%). Diphenhydramine significantly reduced erythema only at the lowest irradiation dose (24 mJ/cm2) and the decrease in OH was associated with an increased amount of deoxygenized hemoglobin (DOH). A similar slight venous dilatation was present at acetylsalicylic acid-exposed sites.(ABSTRACT TRUNCATED AT 250 WORDS)     

Epstein-Barr virus and human herpesvirus type 6 infection in patients with psoriasis

The association of psoriasis with latent human herpesvirus infection has not been well described. To better understand the relationship between severe psoriasis and its treatment with latent human herpesvirus infection, we performed a cross-sectional study to determine if patients with severe psoriasis and psoriasis patients treated with immunosuppressive therapies have higher rates of Epstein-Barr virus and human herpesvirus 6 replication compared to healthy controls. The prevalence of Epstein-Barr virus and human herpesvirus 6 replication was measured in white blood cells by quantitative polymerase chain reaction. We found no evidence of active viral replication in white blood cells of healthy controls (0/10; 95% confidence interval 0-0.26), patients with severe psoriasis (0/25; 95% confidence interval 0-0.11) or severe psoriasis patients on immunosuppressive treatment (0/26; 95% confidence interval 0-0.11). The results of this study suggest that neither severe psoriasis alone, nor in combination with immunosuppressive therapy, is associated with an increase in Epstein-Barr virus or human herpesvirus 6 replication in white blood cells.     

Quantitation of contact allergy in guinea pigs by measuring changes in skin blood flow and skin fold thickness

Skin blood flow determined by laser Doppler flowmetry (LDF) and skin fold thickness (SFT) have been used to quantitate allergic contact dermatitis in the guinea pig maximization test (GPMT) using chlorocresol as the allergen. The closed patch test procedure itself influenced both LDF and SFT measurements when determined in 12 sham-treated guinea pigs. The LDF was maximal at 24 hours and the SFT at 48 hours. Before correlating the quantitative measurements with the conventional visual scoring in test and control animals the value from a nearby control site was subtracted from the test site values. The correlations were highly significant (p less than 0.001-0.05) indicating that the quantitative methods were useful supplements to the visual scoring as a measure of interobserver and interlaboratory differences.     

The regulation of subcutaneous blood flow in patient with Dercum's disease

Dercum's disease or adiposis dolorosa is a poorly understood disorder with painful fatty deposits in the skin localized to the lower extremities. The etiology is unknown. In such a patient the mechanisms of local regulation of blood flow in subcutaneous tissue was investigated by the local 133Xenon washout technique. The patient was reinvestigated one week after treatment with intravenous lidocaine. The local vasoconstrictor response to increase in venous transmural pressure was not present in this patient, but reappeared after lidocaine treatment. Autoregulation of blood flow in subcutaneous tissue was present before as well as after lidocaine treatment. It seems likely that a pain elicited increase in sympathetic activity in the vasoconstrictor fibres abolished the normal vasoconstrictor response to increase in venous transmural pressure. The mechanism of pain relief after intravenous lidocaine infusion is uncertain, but central as well as peripheral mechanisms may be considered.     

Local variation in cutaneous and subcutaneous blood flow measured by CdTe(C1) minidetectors in normal and psoriatic skin

The accuracy of the 133Xe washout method and the validity of newly developed cadmium telluride CdTe(Cl) minisemiconductor detectors were estimated by performing comparative, simultaneous measurements of both cutaneous (CBF) and subcutaneous (SBF) blood flow using 2 conventional scintillation sodium iodide NaI(Tl) and CdTe(Cl) detectors over the same radioactive depot in each of 10 individuals. The accuracy of the 133Xe washout method was found to be 13-15% (C.V.) for the CBF measurements and 9-12% (C.V.) for the SBF measurements. The CdTe(Cl) detectors, which have a weight of 20 g and were attached directly over the radioactive depot, may replace stationary NaI(Tl) detectors placed 20 cm from the depot for measurements of both CBF and SBF. Two CdTe(Cl) detectors were used for estimations of the local variation in CBF and SBF within a distance of 5 cm in normal skin of 10 individuals. The C.V. was 7% for the CBF measurements and 18% for the SBF measurements. Measurements of CBF and SBF were performed in 6 psoriatic patients who, after about 1 week of antipsoriatic treatment with beech tar, developed typical Woronoff rings. The local CBF differed significantly from the center of psoriatic plaques to the margin, in the Woronoff ring, and in nonlesional skin. In contrast, SBF was remarkably equal within the plaque and in the Woronoff ring. The color of the Woronoff ring cannot be ascribed to a local cutaneous vasoconstriction. Cutaneous blood flow in chronic stable, lesional psoriatic skin was significantly lower than previously published values for active lesional psoriatic skin, but significantly higher than CBF in normal individuals. Measurements of CBF in tetrahydrofurfuryl nicotinic acid (Trafuril)-treated skin showed higher values than measurements of CBF in the postischemic hyperemia period both in normal and in lesional psoriatic skin. Trafuril induced a significant increase of CBF in both lesional and nonlesional skin. The high CBF rates in lesional psoriatic skin are not due to a maximally, passively dilated vascular bed.     

Evaluation of contact allergy to chemicals using laser Doppler flowmetry (LDF) technique

Skin blood flow in allergic contact reactions and cross-sensitivity were evaluated using laser Doppler flowmetry (LDF) to study the dose-response relationships in phases of induction and challenge in guinea pigs. Guinea pigs were sensitized with different doses of 1-chloro-2,4-dinitrobenzene (DNCB) and challenged with different doses of DNCB and 2,4-dinitrobenzene sulfonic sodium salt (DNBS). The skin reactions were evaluated by LDF and visual reading score. The results indicated that there were dose-response relationships between the doses of DNCB and LDF measurements in both phases of induction and challenge, that there was a cross-reaction between DNCB and DNBS, and that the reactions at 24 h were greater than that at 48 h after removal of the patches. LDF may discriminate between positive patch test reactions and negative or doubtful reactions, but not between weak positive and strong positive reactions. This is because vascular dilatation and increase of flow already reaches a maximum in weak reactions. The more advanced phases are dominated by oedema formation. This is simply the nature of the inflammatory reaction, rather than a methodological error. The important point is that LDF can separate positive reactions from negative/uncertain reactions. The results indicated that LDF, as a non-invasive technique, may objectively and quantitatively evaluate the dose-response relationships of contact sensitivity of sensitizers.     

Local cold exposure test as therapy control in patients with Raynaud's phenomenon: comparison between laser Doppler fluxmetry and simultaneous red blood cell velocity measurements in nailfold capillaries

Summary Synchronous measurement of laser Doppler flux (LDF) and capillary red blood cell velocity (CBV) was performed in adjacent areas of the same nailfold during a local cold stress test in 12 healthy controls (eight women and four men) and in 22 patients (17 women and seven men) with secondary Raynaud's phenomenon before and after treatment. Two questions were addressed: Are there any differences in the signal pattern between LDF and RBV? Is it possible to detect early on in therapy, before clinical benefit becomes obvious, whether a treatment is successful or not? Despite the fact that the resulting signal patterns recorded by these two techniques are widely compatible, certain differences could be observed. In healthy controls, decrease of values during cooling time and increase after cooling were more distinct in RBV than in LDF. Compared with control values, CBV and LDF in patients with Raynaud's phenomenon were lower. After cooling CBV took an average of 3 min to reach initial value again as compared with 40s in healthy controls. During 4 min observation time, pretest values of LDF were not achieved again in patients, whereas it took 50s in healthy controls. If, after a few days of vasospasmolytic therapy, test results improved or normalized, clinical symptoms subsided gradually during the next weeks. Clinical improvement was not observed in those patients in whom cutaneous blood flow remained decreased despite therapy. CBV indicated this more clearly than LDF. Duration of flow stop at the end of cooling showed a marked improvement in patients treated successfully. Discrepancies between CBV and LDF are interpreted as being due to LDF detecting other vessels in addition to the superficial, nutritional capillaries. LDF seemed to be a poor tool for evaluating the effect of treatment. Determination of CBV and flow stop duration during local cold exposure may help in early selection of the best treatment for a patient with Raynaud's phenomenon by predicting later possible clinical benefit.     

Vascular effects of leukotriene D4 in human skin

Leukotriene D4 (LTD4) increased the blood flow rate in human skin, equipotent to histamine in the dose range of 3.1-200 pmol. The vasodilatation lasted for up to 60 min, and no late reactions occurred. Indomethacin did not affect the LTD4-induced blood flow rate. H1 and H2 antagonists reduced the increase in blood flow rate, but did not abolish the response to LTD4. Local nerve block inhibited the axon reflex-mediated flare component of the LTD4-induced blood flow rate, leaving a local red reaction. This local red reaction was not affected by H1 and H2 antagonists. These results indicate histamine as a mediator of the axon reflex, and show that LTD4 causes a direct vasodilatory effect that is not mediated via histamine or cyclooxygenase products. The laser-Doppler flowmeter was applied for dynamic studies of the vasopressor response in the skin during a Valsalva maneuver, and the relative changes in blood flow were confirmed by control estimates of the blood flow rate by a 133xenon washout method. The pressor response to a Valsalva maneuver was reversed by local nerve block, but not affected by LTD4. Therefore LTD4 did not interfere with the sympathetic activity on the cutaneous vessels. Leukotriene D4 caused a dose-dependent wheal reaction, equipotent to histamine in the dose range of 0.2-200 pmol. Only minor whealing occurred when the vasculature to the test arm was occluded before injection of LTD4 and the circulation restored 30 min later. Most of the LTD4 was apparently metabolized within this period. Subsequent injections of LTD4 into the same sites demonstrated the development of tachyphylaxis with respect to whealing. This evidence suggests that LTD4 cannot mediate sustained inflammation. The injections of LTD4 caused neither pain nor itching. In conclusion, the elucidated properties point to LTD4 as a possible mediator of microvascular changes during acute inflammation.