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Tissue viability imaging: Microvascular response to vasoactive drugs induced by iontophoresis
Linköpings universitet, Institutionen för klinisk och experimentell medicin. Linköpings universitet, Hälsouniversitetet.
Berzelius Clinical Research Center AB.
Berzelius Clinical Research Center AB.
Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska högskolan.
Vise andre og tillknytning
2009 (engelsk)Inngår i: Microvascular Research, ISSN 0026-2862, Vol. 78, nr 2, s. 199-205Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

When one is studying the physiology of the cutaneous microcirculation there is a need for relevant non-invasive and versatile techniques. In this study we used a new optical device, the tissue viability imager (TiVi), to map changes in cutaneous microvascular concentrations of red blood cells during iontophoresis of vasoactive substances (noradrenaline (NA) and phenylephrine (Phe) for vasoconstriction and acetylcholine (ACh) and sodium nitroprusside (SNP) for vasodilatation). We aimed to present data both individually and pooled, using a four-variable logistic dose response model that is commonly used in similar in vitro vascular studies. The accuracy of the TiVi was also investigated by calculating the coefficient of variation and comparing it with similar tests previously done using laser Doppler imaging.

Tests were also performed using the TiVi and LDPI simultaneously to further compare the two methods. Results showed that the TiVi is capable of quantifying vascular responses to iontophorised noradrenaline and phenylephrine without the need to increase background flow first. Fitting the TiVi data to the dose response model resulted in ED50-values with narrow confidence intervals and acceptable r2 values. Mean ED50-values for the TiVi did not differ significantly from similar values obtained using laser Doppler.

Results further seem to suggest that when the blood perfusion increases during vasodilatation in skin the initial phase relies mainly on an increase in red blood cell concentration whereas the further perfusion increase is due to an increase in red blood cell velocity.

sted, utgiver, år, opplag, sider
2009. Vol. 78, nr 2, s. 199-205
Emneord [en]
Cutaneous microcirculation; Iontophoresis; Laser Doppler; Tissue viability imager
HSV kategori
Identifikatorer
URN: urn:nbn:se:liu:diva-21238DOI: 10.1016/j.mvr.2009.04.008OAI: oai:DiVA.org:liu-21238DiVA, id: diva2:240986
Merknad
Original Publication: Joakim Henricson, Anders Nilsson, Erik Tesselaar, Gert Nilsson and Folke Sjöberg, Tissue viability imaging: Microvascular response to vasoactive drugs induced by iontophoresis, 2009, Microvascular Research, (78), 2, 199-205. http://dx.doi.org/10.1016/j.mvr.2009.04.008 Copyright: Elsevier Science B.V., Amsterdam http://www.elsevier.com/ Tilgjengelig fra: 2009-09-30 Laget: 2009-09-30 Sist oppdatert: 2009-10-30bibliografisk kontrollert
Inngår i avhandling
1. Assessment of microvascular effects of vasoactive drugs: Methodological in vivo studies in humansbased on iontophoresis
Åpne denne publikasjonen i ny fane eller vindu >>Assessment of microvascular effects of vasoactive drugs: Methodological in vivo studies in humansbased on iontophoresis
2009 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

Cardiovascular disease is the leading cause of death in western societies and endothelial dysfunction is one of the earliest signs seen in the development of such conditions. Thedevelopment of prognostic tools to aid in the prediction of micro- and macrovascular diseasebased on assessment of vascular reactivity is therefore of paramount importance.

Transdermal iontophoresis offers a quick, non-invasive and relatively straightforward way todeliver vasoactive substances in order to provoke a vascular response in man. When combined with either laser Doppler flowmetry (LDF) or tissue viability imaging (TiVi) for quantification of these responses the methodology offers a potentially powerful tool forvascular investigations. The technique has, however, not been established in clinical practice yet and is mostly used in experimental settings. The lack of consensus in what data analysistechnique to use, uncertainty concerning the actual drug dose applied, and the difficulties associated with the assessment of responses to vasoconstrictors may have contributed to thisfact. The aim of this thesis is therefore to address these issues and thus facilitate the use and improve the applicability of transdermal iontophoresis for assessment of cutaneous microvascular function.

More specifically, a non-linear dose-response model (Emax-model) that is commonly used in in vitro investigations of vascular function was applied to the iontophoresis data. The resultsshow that the Emax-model accurately describes the cutaneous vascular responses totransdermally iontophoresed acetylcholine (ACh) and, sodium nitroprusside (SNP). The Emaxmodelgenerates variables that can be used for quantitative statistical analysis of data andenables a more powerful analysis compared to the methods presently used. It is furtherdemonstrated that the maximal dose effect and vascular responses vary between differentprotocols with the same total iontophoretic charge but with different current strengths anddurations. This finding implies that the assumption that the local drug dose is linearlyproportional to the iontophoretic charge (used for estimation of delivered drug dose to themicrovascular bed) may be inaccurate in in vivo investigations and that there is need for amore refined model.

It is also demonstrated that in a vasoconstrictive setting (iontophoresis of noradrenaline andphenylephrine) TiVi is the favourable technique for measuring vascular responses as it issensitive enough to generate data that can be fitted to the Emax-model even without predilatationof the vessels.

sted, utgiver, år, opplag, sider
Linköping: Linköping University Electronic Press, 2009. s. 47
Serie
Linköping University Medical Dissertations, ISSN 0345-0082 ; 1125
HSV kategori
Identifikatorer
urn:nbn:se:liu:diva-50642 (URN)978-91-7393-638-5 (ISBN)
Disputas
2009-11-06, Berzeliussalen, Hälsouniversitetet, Campus US, Linköpings universitet, Linköping, 09:00 (engelsk)
Opponent
Veileder
Tilgjengelig fra: 2009-10-13 Laget: 2009-10-13 Sist oppdatert: 2009-10-13bibliografisk kontrollert

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