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Existence of Tissue Blood Flow in Response to External Pressure in the Sacral Region of Elderly Individuals - Using an Optical Probe Prototype
Linköping University, Department of Medicine and Health Sciences, Nursing Science. Linköping University, Faculty of Health Sciences.ORCID iD: 0000-0002-9663-3720
Linköping University, Department of Medicine and Health Sciences, Physiology . Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart Centre, Department of Thoracic and Vascular Surgery.ORCID iD: 0000-0002-9095-403X
Mälardalen University.
Linköping University, Department of Medicine and Health Sciences, Nursing Science. Linköping University, Faculty of Health Sciences.
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. Vol. 17, no 4, 311-319 p.
Keyword [en]
pressure ulcer, photoplethysmography, laser Doppler flowmetry, non-invasive, tissue blood flow
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-56449DOI: 10.1111/j.1549-8719.2010.00027.xISI: 000277123800008OAI: oai:DiVA.org:liu-56449DiVA: diva2:319263
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
In thesis
1. Tissue Blood Flow Responses to External Pressure Using LDF and PPG: Testing a System Developed for Pressure Ulcer Research
Open this publication in new window or tab >>Tissue Blood Flow Responses to External Pressure Using LDF and PPG: Testing a System Developed for Pressure Ulcer Research
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:nbn:se:liu:diva-51886 (URN)978-91-7393-472-5 (ISBN)
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
2. Preventing pressure ulcers by assessment of the microcirculation in tissue exposed to pressure
Open this publication in new window or tab >>Preventing pressure ulcers by assessment of the microcirculation in tissue exposed to pressure
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The overall aim of this thesis was to combine optical methods into a system with the ability to simultaneously measure blood flow changes at different tissue depths. The goal of such a system was to reveal vascular mechanisms relevant to pressure ulcer etiology under clinically relevant conditions and in relation to the evaluation of pressure-redistribution support surfaces.

This thesis consists of four quantitative, cross-sectional studies measuring blood flow responses before, during, and after pressure exposure of the sacral tissue. Two optical methods – photoplethysmography and laser Doppler flowmetry – were combined in a newly developed system that has the ability to discriminate blood flows at different tissue depths. Studies I and II explored blood flow responses at different depths in 17 individuals. In Study I the blood flow was related to tissue thickness and tissue compression during pressure exposure of ≥ 220 mmHg. In Study II, the sacral tissue was loaded with 37.5 mmHg and 50.0 mmHg, and the variation in blood flow was measured. Studies III and IV included 42 healthy individuals < 65 years, 38 healthy individuals ≥ 65 years, and 35 patients ≥ 65 years. Study III included between-subject comparisons of blood flow and pressure between individuals in the three study groups lying in supine positions on a standard hospital mattress. Study IV added within-subject comparisons while the individual was lying on four different types of mattress. The studies explored the vascular phenomena pressure-induced vasodilation (PIV) and reactive hyperemia (RH).

The most common blood flow response to tissue exposure in this thesis was PIV, although a decrease in blood flow (a lack of PIV) was observed in some individuals. The patients tended to have higher interface pressure during pressure exposure than the healthy groups but no differences in blood flow responses were seen. Our results showed that pressure levels that are normally considered to be harmless could have a significant effect on the microcirculation in different tissue structures. Differences in individual blood flow responses in terms of PIV and RH were seen, and a larger proportion of individuals lacked these responses in the deeper tissue structures compared to more superficial tissue structures.

This thesis identified PIV and RH that are important vascular mechanisms for pressure ulcer development and revealed for the first time that PIV and RH are present at different depths under clinically relevant conditions. The thesis also identified a population of individuals not previously identified who lack both PIV and RH and seem to be particularly vulnerable to pressure exposure. Further, this thesis has added a new perspective to the microcirculation in pressure ulcer etiology in terms of blood flow regulation and endothelial function that are anchored in clinically relevant studies. Finally, the evaluation of pressureredistribution support surfaces in terms of mean blood flow during and after tissue exposure was shown to be unfeasible, but the assessment of PIV and RH could provide a new possibility for measuring individual physiological responses that are known to be related to pressure ulcer development.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2014. 80 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 1407
Keyword
Pressure ulcer, photoplethysmography, laser Doppler flowmetry, non-invasive, tissue blood flow, reactive hyperemia, pressure-induced vasodilation, interface pressure, risk assessment
National Category
Nursing Clinical Medicine
Identifiers
urn:nbn:se:liu:diva-109960 (URN)10.3384/diss.diva-109960 (DOI)978-91-7519-317-5 (ISBN)
Public defence
2014-09-12, Berzeliussalen, Campus US, Linköpings universitet, Linköping, 09:00 (Swedish)
Opponent
Supervisors
Available from: 2014-08-29 Created: 2014-08-29 Last updated: 2014-08-29Bibliographically approved

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