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Skin capillary appearance and skin microvascular perfusion due to topical application of analgesia cream
Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
2000 (English)In: Microvascular Research, ISSN 0026-2862, E-ISSN 1095-9319, Vol. 59, no 1, 14-23 p.Article in journal (Refereed) Published
Abstract [en]

Local topical analgesia changes basal skin perfusion and its regulation. In particular, the response induced by local heating, which in nontreated skin comprises a rapidly increased perfusion followed by a normalization within 30 s, is altered to a delayed and persistent perfusion increase. The response dependency to the analgesia cream application time, that is, the intradermal penetration of the analgesics and in which vascular plexa the response occurs, is not known. The aim of this study was to assess changes in the appearance of superficial skin capillaries and skin microvascular perfusion changes due to different application periods of topical analgesia cream (EMLA). Twelve subjects were treated with EMLA and placebo applied to the volar side of each forearm, respectively. The treatment areas were assigned different application times (20 min, 40 min, 1 h, 2 h, and 3 h). The areas were cleared from the creams and shortly thereafter provoked during 9 s with a probe heated to 45°C. To assess capillary number density and skin perfusion, capillary microscopy, and Laser Doppler perfusion imaging (LDPI), respectively, were used. The number density of physiologically active capillary was significantly decreased with longer application times of EMLA (P < 0.005). The LDPI-signal showed a persistent perfusion increase after provocation associated with increasing application time of the cream. This perfusion pattern was not seen after 20 min of treatment, but was present in 9 of 12 subjects after 3 h of treatment. No significant relationship between changes in the capillary number density and the LDF measurement was found. In conclusion, a longer application time and therefore a higher intradermal concentration and a deeper penetration of the analgesics was associated with a delayed and persistent perfusion increase after local heating. There was a discrepancy between changes in capillary number density and skin perfusion, indicating that the perfusion increase does not occur in the capillaries but in the deeper lying vessels. Hence, the contribution of the capillary perfusion to the LDF-signal is smaller than previously anticipated. Capillary number density and presumably their perfusion were decreased with longer application times.

Place, publisher, year, edition, pages
2000. Vol. 59, no 1, 14-23 p.
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-30587DOI: 10.1006/mvre.1999.2206Local ID: 16178OAI: oai:DiVA.org:liu-30587DiVA: diva2:251410
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2017-12-13
In thesis
1. Computer assisted video microscopy: in characterization of capillary ensembles
Open this publication in new window or tab >>Computer assisted video microscopy: in characterization of capillary ensembles
2000 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis focuses on evaluation and analysis of capillary microcirculatory changes in the skin, that can be improved and extended by computer assisted video microscopy. Capillary microscopy has been used extensively, both in clinical practice and research, to study different phenomena in the microvasculature of the skin, mainly in the nailfold of fingers and toes where a large portion of the capillary loop can be observed.

In the majority of the different skin regions, the nutritive capillary network approaches the skin surface perpendicularly and capillary microscopy in these sites reveals the apex of the capillary loop as a dark spot. The main approach in this work has been to study a large ensemble of capillary loops, in order to apply statistical and planar models whilst, at the same time, obtaining spatial parameters related to the capillary localization.

The statistical models of proximity are based on nearest neighbour methods and triangulation techniques. The main reason for introducing these models is because of their capability to characterize the heterogeneity of the capillary ensemble.

A computer assisted video microscopy system, that enables both capturing and evaluating of capillary bed images, was assembled and was, thereafter, successfully used in laboratory and clinical studies.

Place, publisher, year, edition, pages
Linköping: Linköpings universitet, 2000. 64 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 648
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-29442 (URN)14788 (Local ID)91-7219-822-2 (ISBN)14788 (Archive number)14788 (OAI)
Public defence
2000-09-12, Berzeliussalen, Universitetssjukhuset, Linköping, 09:00 (Swedish)
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2013-02-27
2. Origin and processing of laser Doppler spectra
Open this publication in new window or tab >>Origin and processing of laser Doppler spectra
2000 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Laser Doppler Flowmetry (LDF) is a technique for studying microvascular blood flow. Laser light is guided to the tissue and the backscattered light, after being Doppler shifted by moving Red Blood Cells (RBCs), is detected using a heterodyne process. In Laser Doppler Perfusion Monitoring, the light is guided to and from the tissue using optical fibers, whilst in Laser Doppler Perfusion Imaging (LDPI), a freely impinging laser beam is used. The Power Spectral Density (PSD) of the photodetector current constitutes the LDF spectrum and can be processed to yield an estimate of the tissue perfusion.

The aim of this thesis was to study the origin and suggest adequate processing of the LDF spectra from both a technical and a physiological perspective.

The orientation and length of the average scattering vector resulting from a RBC/photon interaction, are altered when changing the laser source wavelength. It has been shown theoretically that the change in the orientation and length do not alter the average frequency shift of the scattering event. In vivo measurements on a low and a high perfused area using the wavelengths 632.8 nm and 780 nm respectively, confirm the theoretical findings. The heterodyne efficiency of the detector increases for longer wavelengths, giving higher photodetector signal amplitude.

A method for differentiating high velocity flows, by changing the filtering of the LDF spectra is presented. Emphasis is given to higher frequencies, including information from higher flow velocities.

The scanning mode and the shape of the laser beam. influence the spectral signature in LDPI. In order to maintain a high signal quality, a stepwise mode is to be preferred. The continuous mode induces large spectral components that depend on the scanning speed and the tissue surface roughness. Using a slightly divergent beam minimizes the inlluence of the distance between the detector and the tissue surface.

The physiological perspective includes two randomized and placebo controlled studies of the rela tionship between topical skin analgesia and the perfusion response to different local stimuli. In the first study, it was shown that analgesia using EMLA® cream during local heating, changes the dynamic flow regulation to a persistent and delayed perfusion increase. This was not observed in untreated or placebo treated skin. In the second study, this heating response was positively related to longer treatment times and. hence. to higher intradermal concentrations of the analgesics. By using capillary microscopy. it was shown that analgesic cream treatment for at least one hour reduces the number of physiologically active capillaries by 50%, while LDf perfusion remains unaltered. After local heating, the LDF perfusion increased, in 9/11 subjects by an average of 8.7 times, while the number of capillaries remained decreased. These findings suggest a low capillary influence of the LDF signal in human skin.

Place, publisher, year, edition, pages
Linköping: Linköpings universitet, 2000. 44 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 644
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-29444 (URN)14791 (Local ID)91-7219-805-2 (ISBN)14791 (Archive number)14791 (OAI)
Public defence
2000-09-11, Berzeliussalen, Universitetssjukhuset, Linköping, 09:15 (Swedish)
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2013-02-27

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Salerud, GöranStrömberg, Tomas

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