Stable laser-Doppler flow-motion patterns in the human cutaneous microcirculation: Implications for prospective geroscience studies (original) (raw)
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Microvascular Research, 1998
The hairless plantar paw surface of the rat shows high mm 2 at the back; P õ 0.001). The greater microvascular density at the paw was reflected in a threefold higher skin blood flow with a substantial response to thermal stimulation. This contrasts with hair-covered areas such basal blood flow (6.6 { 0.44 ml/min/100 g) compared to that in the back (1.99 { 0.07 ml/min/100 g) (P õ as the back, where there is much lower basal flow and thermal response. These properties are similar to the 0.001). Microvascular volume at the back was 0.14 { 0.01 1 10 6 RBC/ml in the basal state compared to 0.31 differences seen in humans between skin sites which have a high density of arterioles and venules (AV areas) { 0.01 1 10 6 RBC/ml at the paw. Thus, the increased number of vessels at the paw resulted in a twofold in-and sites with predominantly nutritive (NUTR) capillary perfusion. However, there has been no previous study crease in microvascular volume. The plantar paw surface has considerably more vessels than the back. As might of the microvascular anatomy of rodent skin. We used NIH Image, a quantitative imaging program, to count be expected, there is a higher proportion of arterioles and venules compared to capillaries at the paw than at the capillaries, arterioles, and venules in the skin of the plantar paw surface and the back of 14 Wistar-Kyoto the back. Thus, the plantar paw surface is an AV site compared to the back, which is a NUTR site. Although rats. We also used laser-Doppler techniques to determine skin blood flow at these sites. We found signifi-our prior studies have largely assumed that we could use the paw and back as contrast sites comparable to cantly more vessels per unit area at the paw. There were twice as many capillaries in the paw (19.6 { 2.4 per AV and NUTR sites in humans, we have now for the first time conclusively established this fact. The increased mm 2) compared to the back (9 { 1.5 per mm 2) (P õ 0.001). Similarly, there were three times as many ve-microvascular density at the paw results in higher skin blood flow at this site. ᭧ 1998 Academic Press nules (11.8 { 1.2 per mm 2 vs 3.48 { 0.45 per mm 2 ; P õ 0.001). The largest difference was in the number of arterioles (7.76 { 0.74 per mm 2 vs 0.79 { 0.13 per The microvasculature of the skin varies signifi-Diabetes Center,
Dynamics of Microvascular Blood Flow and Oxygenation Measured Simultaneously in Human Skin
Microcirculation, 2014
We have evaluated the dynamics of skin microvascular blood flow (BF) and tissue oxygenation parameters (OXY) measured simultaneously at the same site using a combined non-invasive BF+OXY+temperature probe. Skin BF, oxygenated (oxyHb) and deoxygenated (deoxyHb) haemoglobin and mean oxygen saturation (SO 2) were measured in 50 healthy volunteers at rest and during perturbation of local blood flow by post-occlusive reactive hyperaemia, sympathetic nervous system-mediated vasoconstriction (deep inspiratory breath-hold) and local skin warming. The relationship between BF and SO 2 over the range of flows investigated was described by a non-linear equation with an asymptote for SO 2 of 84% at BF >50 PU. SO 2 was independently associated with BF, skin temperature, BMI and age, which together identified 59% of the variance in SO 2 (p<0.0001). Fourier analysis revealed periodic low frequency fluctuations in both BF and SO 2 , attributable to endothelial (~0.01 Hz), neurogenic (~0.04 Hz) and myogenic (~0.1Hz) flow motion activity. The frequency coherence between the BF and SO 2 signals was greatest in the endothelial and neurogenic frequency bands. The simultaneous evaluation of microvascular blood flow and oxygenation kinetics in healthy skin provides a platform from which to investigate microvascular impairment in the skin and more generally the pathogenesis of microvascular disease.
Microvascular Research, 2006
The aim of this study was to investigate whether human essential arterial hypertension (EHT) is associated with modification of the skin blood flowmotion (SBF), which could be a sign of skin microcirculatory impairment. Forearm skin perfusion was measured by laser Doppler flowmetry (LDF) in conventional perfusion units (PU) before and after ischemia in 20 middle-age newly diagnosed EHT untreated patients, in 20 middle-age long standing EHT treated patients and in 30 age and sex matched healthy normotensive subjects (NS). Power spectral density (PSD) of SBF total spectrum (0.009-1.6 Hz), as well of five different frequency intervals (FI), each of them related to endothelial (0.009-0.02 Hz), sympathetic (0.02-0.06 Hz), myogenic (0.06-0.2 Hz), respiratory (0.2-0.6) or cardiac (0.6-1.6) activity, was also measured in PU 2 /Hz before and after ishemia, using Fourier analysis of LDF signal. The three studied groups did not differ in basal and post-ischemic skin perfusion or in basal SBF parameters considered. However, while a significant post-ischemic increase in PSD of total spectrum SBF (P < 0.001) and of its different FI, with the only exception of respiratory FI, was observed in NS, a significsnt post-ischemic increase in PSD was observed only for total spectrum (P < 0.01) and for endothelial FI (P < 0.001) in newly diagnosed EHT patients and only for myogenic FI (P < 0.05) in long standing EHT patients. These findings suggest that the mechanisms which mediate the post-ischemic increment of SBF are perturbed earlier in human EHT than the mechanisms which mediate the skin post-ischemic hyperaemia. The same findings also suggest that the impairment of the endothelial mechanism involved in SBF control occurs by the time in the course of EHT.
Biomedicine & Pharmacotherapy, 2006
Skin blood flow oscillation, the so called flowmotion, is a consequence of the arteriolar diameter oscillations, i.e. vasomotion, and it is thought to play a critical role in favoring the optimal distribution of blood flow in the skin microvascular bed. Investigation of skin blood flowmotion, using spectral analysis of the skin laser Doppler flowmetry (LDF) signal, showed different flowmotion waves of endothelial, sympathetic or myogenic mediated vasomotion origin. Using this method in peripheral arterial obstructive disease (PAOD) patients an impairment of all the three flowmotion waves was found at level of the diseased leg following ischemia in the II stage of the disease and basally in critical limb ischemia. In patients with essential arterial hypertension (EHT) forearm skin blood flowmotion showed a post-ischemic impairment of myogenic and sympathetic components in newly diagnosed patients, and of endothelial and sympathetic components in long standing patients. In diabetic patients there was a selective impairment of skin flowmotion wave mediated by sympathetic activity in basal conditions. Investigation of skin blood flowmotion in response to different vasoactive substances demonstrated an important role of nitric oxide (NO) in controlling the endothelial component of vasomotion and an insulin action on smooth muscle cells of skin microvessels. All these data suggest that the study of skin blood flowmotion can become a method to early and easily detect skin microvascular impairment in vascular diseases and to investigate the mechanisms of substances active on skin microvascular bed.
Angiology, 1987
The cutaneous laser Doppler device (LDF) was employed to determine its usefulness in differentiating the circulation of the feet in normal subjects from that in patients with arteriosclerosis obliterans. It is shown that the laser Doppler frequencies correlated well with results from venous occlusion plethysmography, which measured volume rate of flow. Thus, one can determine volume rate of flow by the simple Doppler method. There was a linear relationship between these two methods of measurements. Using the LDF method, it was determined that normal individuals have toe flows that on the average are 42% of finger flows in supine resting subjects. In peripheral vascular disease of the lower extremities, the LDF measurements showed a decreased circulation in the large toes when the patients are supine and the lower extremities flat. The results between health and disease are exaggerated by elevating the feet, at which time the diseased circulation falls to extremely low values compare...
Low-frequency oscillations of the laser Doppler perfusion signal in human skin
Microvascular Research, 2006
Spectral analysis of the laser Doppler flow (LDF) signal in the frequency interval from 0.0095-2.0 Hz reveals blood flow oscillations with frequencies around 1.0, 0.3, 0.1, 0.04 and 0.01 Hz. The heartbeat, the respiration, the intrinsic myogenic activity of vascular smooth muscle, the neurogenic activity of the vessel wall and the vascular endothelium influence these oscillations, respectively. The first aim of this study was to investigate if a slow oscillatory component could be detected in the frequency area below 0.0095 Hz of the human cutaneous blood perfusion signal. Unstimulated basal blood skin perfusion and enhanced perfusion during iontophoresis with the endothelium-dependent vasodilator acetylcholine (ACh) and the endothelium-independent vasodilator sodium nitroprusside (SNP) were measured in healthy male volunteers and the wavelet transform was computed. A low-frequency oscillation between 0.005 and 0.0095 Hz was found both during basal conditions and during iontophoresis with ACh and SNP. Iontophoresis with ACh increased the normalized amplitude to a greater extent than SNP (P = 0.001) indicating modulation by the vascular endothelium. To gain further insight into the mechanisms for this endothelium dependency, we inhibited nitric oxide (NO) synthesis with N G-monomethyl-L-arginine (L-NMMA) and prostaglandin (PG) synthesis by aspirin. L-NMMA did not affect the increased response to ACh vs. SNP iontophoresis in the 0.005-0.0095-Hz interval (P = 0.006) but abolished the difference in the 0.0095-0.021-Hz interval (P = 0.97). Aspirin did not affect the difference in response to ACh and SNP in either of the two frequency intervals. Thus, other endothelial mechanisms, such as endothelium-derived hyperpolarizing factor (EDHF), might be involved in the regulation of this sixth frequency interval (0.005-0.0095 Hz).
Scientific Reports, 2019
Laser Doppler flowmetry (LDF) and reflection photoplethysmography (PPG) are standard technologies to access microcirculatory function in vivo. However, different light frequencies mean different interaction with tissues, such that LDF and PPG flowmotion curves might have distinct meanings, particularly during adaptative (homeostatic) processes. Therefore, we analyzed LDF and PPG perfusion signals obtained in response to opposite challenges. Young healthy volunteers, both sexes, were assigned to Group 1 (n = 29), submitted to a normalized Swedish massage procedure in one lower limb, increasing perfusion, or Group 2 (n = 14), submitted to a hyperoxia challenge test, decreasing perfusion. LDF (Periflux 5000) and PPG (PLUX-Biosignals) green light sensors applied distally on both lower limbs recorded perfusion changes for each experimental protocol. Both techniques detected the perfusion increase with massage, and the perfusion decrease with hyperoxia, in both limbs. Further analysis wit...
A new laser Doppler flowmeter prototype for depth dependent monitoring of skin microcirculation
Review of Scientific Instruments, 2012
Laser Doppler flowmetry (LDF) is now commonly used in clinical research to monitor microvascular blood flow. However, the dependence of the LDF signal on the microvascular architecture is still unknown. That is why we propose a new laser Doppler flowmeter for depth dependent monitoring of skin microvascular perfusion. This new laser Doppler flowmeter combines for the first time, in a device, several wavelengths and different spaced detection optical fibres. The calibration of the new apparatus is herein presented together with in vivo validation. Two in vivo validation tests are performed. In the first test, signals collected in the ventral side of the forearm are analyzed; in the second test, signals collected in the ventral side of the forearm are compared with signals collected in the hand palm. There are good indicators that show that different wavelengths and fibre distances probe different skin perfusion layers. However, multiple scattering may affect the results, namely the ones obtained with the larger fibre distance. To clearly understand the wavelength effect in LDF measurements, other tests have to be performed.