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Laser Doppler Perfusion Monitoring and Imaging especially as regards testing for sympathetic nerve function

Freccero, Carolin LU (2005)
Abstract (Swedish)
Popular Abstract in Swedish

Laser Doppler metoder avsedda för mätning av blodflöde baserar sig på det faktum att fotoner skiftar i våglängd när de träffar blodkroppar i rörelse. Den förändrade våglängden registreras och signalen bearbetas varefter resultatet uttrycks i en godtycklig enhet och anses utgöra ett mått på blodflöde.



Laser Doppler Perfusion Monitoring (LDPM) är en metod med vilken blodflödet i en bestämd del av en vävnad, t.ex. huden, kan mätas medelst en sond. Bildframställning med hjälp av en scanner (Laser Doppler Perfusion Imaging - LDPI) är en likartad metod, men denna ger istället en ögonblicksbild av den rumsliga fördelningen av vävnadens (t.ex. hudens) blodflöde inom ett större fält.... (More)
Popular Abstract in Swedish

Laser Doppler metoder avsedda för mätning av blodflöde baserar sig på det faktum att fotoner skiftar i våglängd när de träffar blodkroppar i rörelse. Den förändrade våglängden registreras och signalen bearbetas varefter resultatet uttrycks i en godtycklig enhet och anses utgöra ett mått på blodflöde.



Laser Doppler Perfusion Monitoring (LDPM) är en metod med vilken blodflödet i en bestämd del av en vävnad, t.ex. huden, kan mätas medelst en sond. Bildframställning med hjälp av en scanner (Laser Doppler Perfusion Imaging - LDPI) är en likartad metod, men denna ger istället en ögonblicksbild av den rumsliga fördelningen av vävnadens (t.ex. hudens) blodflöde inom ett större fält. Båda metoderna påverkas av en rad instrumentella faktorer så som till exempel sondutförande (sond = den del av instrumentet som är i kontakt med huden) och laserljusets våglängd. I denna avhandling presenteras resultaten av mätningar av förändringar i hudens genomblödning som registrerats med dessa två laser Doppler-metoder, dvs. LDPM och LDPI. Speciellt studerades förändringar i hudens blodflöde framkallade av en kärlsammandragning förmedlad av det sympatiska nervsystemet.



Fingrets hudblodflöde undersöktes dels hos friska försökspersoner, dels hos diabetespatienter. Mätningar genomfördes med olika sondutföranden och vid olika våglängder. I tre av experimenten utlöstes kärlsammandragningen genom kylning av försökspersonens andra hand. Som ett mått på kärlreaktionen beräknades ett så kallad vasokonstriktionsindex (ung kärlsammandragningsindex; kvoten mellan blodflöde efter och före kylning). I ett annat experiment undersöktes effekterna av lokal värmning. Förutom blodflöde analyserades även data beträffande koncentrationen av blodkroppar i rörelse och deras genomsnittliga hastighet.



Våra observationer överensstämmer i stort med allmänt vedertagna hypoteser. Ett större avstånd mellan de fibrer i sonden som utsänder respektive registrerar ljuset, kan förväntas möjliggöra mätningar djupare i huden. Detta tycks även kunna uppnås genom en ökning av våglängden. Ändå kan ytligt kapillärblodflöde och blodflöde i hudens djupare skikt inte säkert särskiljas med hjälp av dessa olika instrument. Inte heller uppspaltningen av blodflödet i hastighet och blodkroppskoncentration kan med säkerhet användas för detta ändamål. Däremot kan hastighet och koncentration användas för att klargöra olika mikrocirkulatoriska händelser ur fysiologisk synvinkel. Exempelvis fann vi att de två komponenterna följs åt vid låga och måttliga flöden, medan koncentrationen ökar avsevärt mer vid höga flöden. Då vi tittade på rytmiskt återkommande händelser fann vi att förflyttningen av blodet från hjärtat till periferin sker i små snabba stötar vid varje hjärtslag, blodkropparnas täthet påverkas dock inte av det.



Då man inte kan mäta det mikrovaskulära blodflödet kvantitativt och dessutom är beroende av den instrumentella designen, är behovet av allmänt accepterade och standardiserade testprocedurer och protokoll uppenbart. Testet med kylning av en hand och mätning av blodflödet i den andra som presenteras i denna avhandling är bara ett möjligt exempel. Under de givna förutsättningarna blir resultatet praktiskt taget oberoende av de använda laser Doppler apparaterna. Hos diabetespatienter var kärlsammandragningsreflexen försvagad och vår metod kan användas för att följa förändringar av den sympatiska nervfunktionen i huden hos dessa patienter. (Less)
Abstract
The operating principle of all laser Doppler methods is based on the fact that incident photons shift in wavelength when interacting with moving blood cells passing through the microvascular network. After photodetection and further signal processing, the recorded parameter can be considered an arbitrary measure of tissue blood flow, and this is referred to as ?perfusion?. Laser Doppler perfusion monitoring with a probe (LDPM) gives a real-time recording from a small area, whereas imaging by use of a scanner (LDPI) creates an instant view of the spatial distribution over a wider area. Measurements are influenced by a variety of instrumental factors such as probe configuration and light wavelength. This thesis presents findings regarding... (More)
The operating principle of all laser Doppler methods is based on the fact that incident photons shift in wavelength when interacting with moving blood cells passing through the microvascular network. After photodetection and further signal processing, the recorded parameter can be considered an arbitrary measure of tissue blood flow, and this is referred to as ?perfusion?. Laser Doppler perfusion monitoring with a probe (LDPM) gives a real-time recording from a small area, whereas imaging by use of a scanner (LDPI) creates an instant view of the spatial distribution over a wider area. Measurements are influenced by a variety of instrumental factors such as probe configuration and light wavelength. This thesis presents findings regarding changes of skin microcirculation when assessed by various technologies, and special attention was paid to those changes induced by sympathetically mediated vasoconstriction.



Finger skin blood flow was investigated both in healthy subjects, and in patients with diabetes mellitus. Measurements with LDPM were performed with different probe configurations related to distance between emitting and detecting fibres. Measurements with LDPI were performed with different light wavelengths. In three experimental series, contra-lateral hand cooling induced vasoconstriction. In one series, the effects of local heating were explored. Besides the perfusion parameter, details regarding the concentration of moving blood cells and their average velocity were displayed and analysed.



Our clinical findings are coherent with technical and theoretical assumptions. Hence, the wider fibre separation in LDPM the deeper the measurement and an increment in wavelength seem to have a similar effect. However, superficial capillary blood flow and deeper shunt blood flow cannot reliably be distinguished from one another by means of these different instrumental standards. Neither can the separation of the perfusion parameter into velocity and concentration with safety be used for this purpose. However, velocity and concentration may be used for clarifying various microcirculatory events from the physiological point of view. We found for instance that the two components act merely parallel at low and moderate perfusion rates, whereas a high perfusion rate primarily is associated with an increase in concentration. By applying frequency analysis, it was furthermore shown that the movement of the column of blood periodically reaches the peripheral vascular bed concurrently with the cardiac cycle whereas concentration remains the same.



As microvascular blood flow cannot be measured quantitatively and due to varying instrumental design, the need for widely accepted and standardised test procedures and protocols is apparent. The cold pressor test used in this thesis is just one example. Under such given circumstances, the test parameter may be practically independent of the laser Doppler device used, as shown by the vasoconstriction index in the present studies. Diabetic patients showed an attenuated vasoconstriction response, and the index can reliably be used to monitoring peripheral sympathetic nerve function in these patients. (Less)
Please use this url to cite or link to this publication:
author
supervisor
opponent
  • Professor Sjöberg, Folke, Linköping University
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Physiology, wavelength, sympathetic vasodilatation, sympathetic vasoconstriction, sympathetic nerve function, parasympathetic nerve function, laser Doppler perfusion imaging, laser Doppler perfusion monitoring, finger skin blood flow, fibre separation, contralateral cooling, Concentration, Fysiologi, Cardiovascular system, Kardiovaskulära systemet, Diagnostik, Diagnostics
pages
100 pages
publisher
Department of Plastic and Reconstructive Surgery, Malmö University Hospital, Malmö, Sweden,
defense location
Kirurgiska Klinikens föreläsningssal, ingång 42, Universitetssjukhuset MAS, 20502 Malmö
defense date
2005-04-15 09:15
ISSN
1652-8220
ISBN
91-85439-15-0
language
English
LU publication?
yes
id
c12c029f-37b2-4399-aa4f-71c98cb0f8c1 (old id 544592)
date added to LUP
2007-10-13 12:10:33
date last changed
2016-09-19 08:44:54
@phdthesis{c12c029f-37b2-4399-aa4f-71c98cb0f8c1,
  abstract     = {The operating principle of all laser Doppler methods is based on the fact that incident photons shift in wavelength when interacting with moving blood cells passing through the microvascular network. After photodetection and further signal processing, the recorded parameter can be considered an arbitrary measure of tissue blood flow, and this is referred to as ?perfusion?. Laser Doppler perfusion monitoring with a probe (LDPM) gives a real-time recording from a small area, whereas imaging by use of a scanner (LDPI) creates an instant view of the spatial distribution over a wider area. Measurements are influenced by a variety of instrumental factors such as probe configuration and light wavelength. This thesis presents findings regarding changes of skin microcirculation when assessed by various technologies, and special attention was paid to those changes induced by sympathetically mediated vasoconstriction.<br/><br>
<br/><br>
Finger skin blood flow was investigated both in healthy subjects, and in patients with diabetes mellitus. Measurements with LDPM were performed with different probe configurations related to distance between emitting and detecting fibres. Measurements with LDPI were performed with different light wavelengths. In three experimental series, contra-lateral hand cooling induced vasoconstriction. In one series, the effects of local heating were explored. Besides the perfusion parameter, details regarding the concentration of moving blood cells and their average velocity were displayed and analysed.<br/><br>
<br/><br>
Our clinical findings are coherent with technical and theoretical assumptions. Hence, the wider fibre separation in LDPM the deeper the measurement and an increment in wavelength seem to have a similar effect. However, superficial capillary blood flow and deeper shunt blood flow cannot reliably be distinguished from one another by means of these different instrumental standards. Neither can the separation of the perfusion parameter into velocity and concentration with safety be used for this purpose. However, velocity and concentration may be used for clarifying various microcirculatory events from the physiological point of view. We found for instance that the two components act merely parallel at low and moderate perfusion rates, whereas a high perfusion rate primarily is associated with an increase in concentration. By applying frequency analysis, it was furthermore shown that the movement of the column of blood periodically reaches the peripheral vascular bed concurrently with the cardiac cycle whereas concentration remains the same.<br/><br>
<br/><br>
As microvascular blood flow cannot be measured quantitatively and due to varying instrumental design, the need for widely accepted and standardised test procedures and protocols is apparent. The cold pressor test used in this thesis is just one example. Under such given circumstances, the test parameter may be practically independent of the laser Doppler device used, as shown by the vasoconstriction index in the present studies. Diabetic patients showed an attenuated vasoconstriction response, and the index can reliably be used to monitoring peripheral sympathetic nerve function in these patients.},
  author       = {Freccero, Carolin},
  isbn         = {91-85439-15-0},
  issn         = {1652-8220},
  keyword      = {Physiology,wavelength,sympathetic vasodilatation,sympathetic vasoconstriction,sympathetic nerve function,parasympathetic nerve function,laser Doppler perfusion imaging,laser Doppler perfusion monitoring,finger skin blood flow,fibre separation,contralateral cooling,Concentration,Fysiologi,Cardiovascular system,Kardiovaskulära systemet,Diagnostik,Diagnostics},
  language     = {eng},
  pages        = {100},
  publisher    = {Department of Plastic and Reconstructive Surgery, Malmö University Hospital, Malmö, Sweden,},
  school       = {Lund University},
  title        = {Laser Doppler Perfusion Monitoring and Imaging especially as regards testing for sympathetic nerve function},
  year         = {2005},
}