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Tissue Blood Flow Responses to External Pressure Using LDF and PPG: Testing a System Developed for Pressure Ulcer Research
Linköping University, Department of Medical and Health Sciences, Nursing Science. Linköping University, Faculty of Health Sciences.ORCID iD: 0000-0002-9663-3720
2009 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Background: Pressure ulcers are a problem for immobile individuals, and having pressure ulcers impact and restrict the daily and are often associated with pain. Pressure ulcers occur frequently and cause high costs for the health care system. The prevention of pressure ulcers by focussing on different mattresses and overlays aimed to reduce the interface pressure or the pressure exposure of the tissue. The problem is the poor evaluation of this type of equipment. There are important factors regarding pressure ulcer development, pressure, shear, temperature and humidity. People are affected by external pressure in different ways and therefore it is preferable to measure the effect of pressure as a complement to the pressure measurement and thus we consider blood flow measurements to be a suitable method.

Aims: The aim of Study I, the first part in this thesis was to investigate the existence of sacral tissue blood flow at different depths in response to external pressure in elderly individuals as a part of evaluation of a. newly developed system. The aim of Study II, the second part was to evaluate a multiparametric system combining LDF and photoplethysmography into a single probe, for the simultaneous measurement of blood flow at different depths in the sacral tissue when the tissue is exposed to external load. This new system will be used to facilitate the understanding of pressure ulcer formation.

Methods: To be able to observe tissue blood flow, the non-invasive optical methods laser Doppler flowmetry and photoplethysmography were used. In this thesis a newly developed prototype probe was used, combining the two methods. Green light and infrared light were used in the PPG instrument for penetrating the depths of approximately 2 mm, 8 mm and 20 mm depths. A HeNe laser was used to measure the superficial skin blood flow, <1 mm depth. The prototype probe, made of silicone was fixed in a stiff 10×10 cm plate.

Seventeen active individuals over the age of 60 were recruited for the two studies. In Study I, the subject´s sacral blood flow and tissue thickness (using ultrasound) were measured in unloaded position and in supine position loading the area with their own body weight. In Study II, the sacral area was provoked with external load at 37.5 mmHg and 50.0 mmHg and the relative change in blood flow at different depths was observed before, during and after load.

Results: Study I showed that the sacral tissue in elderly individuals is highly affected by load and is compressed by 60.3 ± 11.9%. The mean sacral tissue thickness was 26 ± 13 mm in unloaded tissue and 10 ± 6 mm in loaded tissue. Correlations were found between BMI and tissue thickness: both TTunload r=0.68 (p=0.003) and TTload r=0.68 (p=0.003). Almost all subjects had affected blood flow superficially but only occasionally deeper in the tissue and findings may indicate that the blood flow is occluded in the superficial layer before it is occluded deeper in the tissue structure. The most common response in Study II was an increase in blood flow while loading. In those occasions when the blood flow decreased, it was mostly affected at the skin surface and the reactive hyperaemia occurred more frequently in the superficial tissue structures. The blood flow responses may be different in the different tissue layers.

Conclusions: The newly developed system was found to be suitable for measuring tissue blood flow at different depths; however the prototype probe had some limitations that will be solved in the further development of the system into a thin flexible probe with ability to measure a larger area.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press , 2009. , 48 p.
Series
Linköping Studies in Health Sciences. Thesis, ISSN 1100-6013 ; 109
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-51886ISBN: 978-91-7393-472-5 (print)OAI: oai:DiVA.org:liu-51886DiVA: diva2:278058
Presentation
2009-12-10, Linden, ingång 65, Campus US, Linköpings Universitet, Linköping, 13:00 (English)
Supervisors
Note

In the list of articles in the Thesis the title of article I is "Tissue blood flow responses to external pressure in the sacral region of elderly individuals". The correct title is "Existence of tissue blood flow in response to external pressure in the sacral region of elderly individuals - Evaluation of a prototype".

Available from: 2009-11-23 Created: 2009-11-23 Last updated: 2014-08-29Bibliographically approved
List of papers
1. Existence of Tissue Blood Flow in Response to External Pressure in the Sacral Region of Elderly Individuals - Using an Optical Probe Prototype
Open this publication in new window or tab >>Existence of Tissue Blood Flow in Response to External Pressure in the Sacral Region of Elderly Individuals - Using an Optical Probe Prototype
2010 (English)In: MICROCIRCULATION, ISSN 1073-9688, Vol. 17, no 4, 311-319 p.Article in journal (Refereed) Published
Abstract [en]

Pandgt;Objective: The aim was to investigate the existence of sacral tissue blood flow at different depths in response to external pressure and compression in elderly individuals using a newly developed optical probe prototype. Methods: The tissue blood flow and tissue thickness in the sacral area were measured during load in 17 individuals using laser Doppler flowmetry and photoplethysmography in a combined probe, and digital ultrasound. Results: The mean age was 68.6 +/- 7.0 years. While loading, the mean compression was 60.3 +/- 11.9%. The number of participants with existing blood flow while loading increased with increased measurement depth. None had enclosed blood flow deep in the tissue and at the same time an existing more superficial blood flow. Correlation between tissue thickness and BMI in unloaded and loaded sacral tissue was shown: r = 0.68 (P = 0.003) and r = 0.68 (P = 0.003). Conclusions: Sacral tissue is highly compressed by external load. There seems to be a difference in responses to load in the different tissue layers, as occluded blood flow in deeper tissue layers do not occur unless the blood flow in the superficial tissue layers is occluded.

Place, publisher, year, edition, pages
Taylor and Francis, 2010
Keyword
pressure ulcer, photoplethysmography, laser Doppler flowmetry, non-invasive, tissue blood flow
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-56449 (URN)10.1111/j.1549-8719.2010.00027.x (DOI)000277123800008 ()
Note
This is an electronic version of an article published in: Sara Bergstrand, Toste Länne, Maria Linden and Margareta Lindgren, Existence of Tissue Blood Flow in Response to External Pressure in the Sacral Region of Elderly Individuals - Using an Optical Probe Prototype, 2010, MICROCIRCULATION, (17), 4, 311-319. MICROCIRCULATION is available online at informaworldTM: http://dx.doi.org/10.1111/j.1549-8719.2010.00027.x Copyright: Taylor and Francis http://www.tandf.co.uk/journals/default.asp Available from: 2010-05-17 Created: 2010-05-17 Last updated: 2017-03-27
2. Blood flow measurements at different depths using photoplethysmography and laser Doppler techniques
Open this publication in new window or tab >>Blood flow measurements at different depths using photoplethysmography and laser Doppler techniques
Show others...
2009 (English)In: Skin research and technology, ISSN 0909-752X, E-ISSN 1600-0846, Vol. 15, no 2, 139-147 p.Article in journal (Refereed) Published
Abstract [en]

Background/purpose: This study has evaluated a multi-parametric system combining laser Doppler flowmetry and photoplethysmography in a single probe for the simultaneous measurement of blood flow at different depths in the tissue. This system will be used to facilitate the understanding of pressure ulcer formation and in the evaluation of pressure ulcer mattresses.

Methods: The blood flow in the tissue over the sacrum was measured before, during and after loading with 37.5 mmHg, respectively, 50.0 mmHg. The evaluation of the system consisted of one clinical part, and the other part focusing on the technicalities of the probe prototype.

Results: An increase in blood flow while loading was the most common response, but when the blood flow decreased during loading it was most affected at the skin surface and the blood flow responses may be different due to depths of measurement. Reactive hyperaemia may occur more frequently in the superficial layers of the tissue.

Conclusion: The study showed that the new system is satisfactory for measuring tissue blood flow at different depths. The laser Doppler complements the photoplethysmography, and further development of the system into a thin flexible probe with the ability to measure a larger area is required.

Place, publisher, year, edition, pages
Wiley-Blackwell, 2009
Keyword
pressure ulcers, blood flow, photoplethysmography, laser Doppler flowmetry, non-invasive
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-18018 (URN)10.1111/j.1600-0846.2008.00337.x (DOI)
Note

This is the authors’ version of the following article: Sara Bergstrand, Lars-Göran Lindberg, Anna-Christina Ek and Margareta Lindgren, Blood flow measurements at different depths using photoplethysmography and laser Doppler techniques, 2009, SKIN RESEARCH AND TECHNOLOGY, (15), 2, 139-147. which has been published in final form at: http://dx.doi.org/10.1111/j.1600-0846.2008.00337.x Copyright: Blackwell Publishing Ltd http://www.blackwellpublishing.com/

Available from: 2009-05-26 Created: 2009-05-04 Last updated: 2017-12-13Bibliographically approved

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