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Non-invasive techniques for assessment of peripheral blood flow at different vascular depths
Mälardalen University, School of Innovation, Design and Engineering. (ISS)
2011 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Missing or reduced blood flow can lead to pressure ulcers. Monitoring blood flow in areas prone to pressure ulcer development would be a valuable tool for prevention of pressure ulcers.

PPG and LDF are both established non invasive optical techniques that can be used to estimate the changes in blood flow in different tissue volumes. The aim of this thesis was to combine the established techniques, LDF and PPG, into one flexible silicon probe intended for evaluation of peripheral blood flow in tissue volumes prone to pressure ulcer development. Further, a temperature sensor was integrated.

Two probe configurations combining LDF and PPG has been evaluated regarding the ability to separate between shallow, medium and deep blood flow variations, and skin temperature changes. Further, techniques to reduce or totally avoid interference between LDF and PPG have been investigated.

The probes can be used to discriminate between blood flows at different vascular depths. The vascular depths reached by the different channels correspond to the depths of interest when investigating pressure ulcer aetiology. The probe itself has shown not to affect the skin surface temperature, neither due to the silicon sheet or the light. The skin temperature can be expected to rise and approach the body core temperature by lying in supine position alone, which has to be taken into consideration when designing studies.

By switching between the different light sources, interference can be totally avoided. When rapid blood flow variations at several vascular depths are of interest to evaluate, a peripheral placement of the LDF-fibre and an increased illumination power of the PPG-LEDs might be used to minimize the interference between LDF and PPG.

Both probes have shown potential to be used for investigation of the processes in pressure ulcer development.

Place, publisher, year, edition, pages
Västerås: Mälardalen University , 2011.
Series
Mälardalen University Press Licentiate Theses, ISSN 1651-9256 ; 131
Research subject
Electronics
Identifiers
URN: urn:nbn:se:mdh:diva-12226ISBN: 978-91-7485-014-7OAI: oai:DiVA.org:mdh-12226DiVA: diva2:415696
Presentation
2011-05-19, Pi, Högskoleplan 1, Västerås, 14:00 (Swedish)
Opponent
Supervisors
Available from: 2011-05-09 Created: 2011-05-09 Last updated: 2011-05-12Bibliographically approved
List of papers
1. Assessment of the optical interference in a PPG-LDF system used for estimation of tissue blood flow
Open this publication in new window or tab >>Assessment of the optical interference in a PPG-LDF system used for estimation of tissue blood flow
2011 (English)In: IFMBE PROCEEDINGS: 15th Nordic-Baltic Conference on Biomedical Engineering and Medical Physics, NBC 2011; Aalborg; 14 June 2011 through 17 June 2011 / [ed] Kim Dremstrup, 2011Conference paper (Refereed)
National Category
Medical Laboratory and Measurements Technologies
Research subject
Electronics
Identifiers
urn:nbn:se:mdh:diva-12223 (URN)10.1007/978-3-642-21683-1_4 (DOI)2-s2.0-79959985250 (ScopusID)978-364221682-4 (ISBN)
Available from: 2011-05-09 Created: 2011-05-09 Last updated: 2013-12-03Bibliographically approved
2. Long-term monitoring of blood flow at different depths using LDF and PPG - issues to consider
Open this publication in new window or tab >>Long-term monitoring of blood flow at different depths using LDF and PPG - issues to consider
(English)Article in journal (Refereed) Submitted
National Category
Medical Laboratory and Measurements Technologies
Research subject
Electronics
Identifiers
urn:nbn:se:mdh:diva-12224 (URN)
Available from: 2011-05-09 Created: 2011-05-09 Last updated: 2015-07-09Bibliographically approved
3. A technique based on laser Doppler flowmetry and photoplethysmography for simultaneously monitoring blood flow at different tissue depths
Open this publication in new window or tab >>A technique based on laser Doppler flowmetry and photoplethysmography for simultaneously monitoring blood flow at different tissue depths
Show others...
2010 (English)In: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 48, no 5, 415-422 p.Article in journal (Refereed) Published
Abstract [en]

The aim of this study was to validate a non-invasive optical probe for simultaneous blood flow measurement at different vascular depths combining three photoplethysmography (PPG) channels and laser Doppler flowmeter (LDF). Wavelengths of the PPG were near-infrared 810 nm with source-to-detector separation of 10 and 25 mm, and green 560 nm with source-to-detector separation of 4 mm. The probe is intended for clinical studies of pressure ulcer aetiology. The probe was placed over the trapezius muscle, and depths from the skin to the trapezius muscle were measured using ultrasound and varied between 3.8 and 23 mm in the 11 subjects included. A provocation procedure inducing a local enhancement of blood flow in the trapezius muscle was used. Blood flows at rest and post-exercise were compared. It can be concluded that this probe is useful as a tool for discriminating between blood flows at different vascular tissue depths. The vascular depths reached for the different channels in this study were at least 23 mm for the near-infrared PPG channel (source-to-detector separation 25 mm), 10-15 mm for the near-infrared PPG channel (separation 10 mm), and shallower than 4 mm for both the green PPG channel (separation 4 mm) and LDF.

Identifiers
urn:nbn:se:mdh:diva-11049 (URN)10.1007/s11517-010-0577-2 (DOI)000276771800002 ()2-s2.0-77955583312 (ScopusID)
Available from: 2010-11-11 Created: 2010-11-11 Last updated: 2013-12-03Bibliographically approved

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