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Preventing pressure ulcers by assessment of the microcirculation in tissue exposed to pressure
Linköping University, Department of Medical and Health Sciences, Division of Nursing Science. Linköping University, Faculty of Health Sciences.ORCID iD: 0000-0002-9663-3720
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 [en]
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: urn:nbn:se:liu:diva-109960DOI: 10.3384/diss.diva-109960ISBN: 978-91-7519-317-5 (print)OAI: oai:DiVA.org:liu-109960DiVA: diva2:741881
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
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
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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
3. Pressure-induced vasodilation and reactive hyperemia at different depths in sacral tissue under clinically relevant conditions
Open this publication in new window or tab >>Pressure-induced vasodilation and reactive hyperemia at different depths in sacral tissue under clinically relevant conditions
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2014 (English)In: Microcirculation, ISSN 1073-9688, E-ISSN 1549-8719, Vol. 21, no 8, 761-771 p.Article in journal (Refereed) Published
Abstract [en]

OBJECTIVE: To characterize pressure-induced vasodilatation and reactive hyperemia at different sacral tissue depths in different populations under clinically relevant pressure exposure.

METHODS: Forty-two subjects (< 65 years), 38 subjects (≥ 65 years), and 35 patients (≥ 65 years) participated. Interface pressure, skin temperature, and blood flow at tissue depths of 1 mm, 2 mm, and 10 mm (using laser Doppler flowmetry and photoplethysmography) were measured in the sacral tissue before, during, and after load in a supine position.

RESULTS: pressure-induced vasodilatation and reactive hyperemia were observed at three tissue depths. At 10 mm depth, the proportion of subjects with a lack of pressure-induced vasodilatation was higher compared to superficial depths. The patients had higher interface pressure during load than the healthy individuals, but there were no significant differences in blood flow. Twenty-nine subjects in all three study groups were identified with a lack of pressure-induced vasodilatation and reactive hyperemia.

CONCLUSIONS: pressure-induced vasodilatation and reactive hyperemia can be measured at different tissue depths. A lack of these responses was found in healthy individuals as well as in patients indicating an innate susceptibility in some individuals, and are potential important factors to evaluate in order to better understand the etiology of pressure ulcers.

Place, publisher, year, edition, pages
John Wiley & Sons, 2014
Keyword
Pressure ulcer, photoplethysmography, laser Doppler flowmetry, non-invasive, tissue blood flow
National Category
Nursing Clinical Medicine
Identifiers
urn:nbn:se:liu:diva-109950 (URN)10.1111/micc.12160 (DOI)000344789400010 ()25100630 (PubMedID)
Available from: 2014-08-29 Created: 2014-08-29 Last updated: 2017-12-05Bibliographically approved
4. Microcirculatory responses of sacral tissue in healthy individuals and inpatients on different pressure-redistribution mattresses
Open this publication in new window or tab >>Microcirculatory responses of sacral tissue in healthy individuals and inpatients on different pressure-redistribution mattresses
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2015 (English)In: Journal of Wound Care, ISSN 0969-0700, E-ISSN 2052-2916, Vol. 24, no 8, 346-358 p.Article in journal (Refereed) Published
Abstract [en]

Objective: The aim of this study was to explore the interaction between interface pressure and pressure-induced vasodilation and reactive hyperemia with different pressureredistribution mattresses.

Method: A cross-sectional study was performed with a convenience sample of 42 healthy individuals between 18 and 64 years of age, 38 healthy individuals 65 years or older, and 35 inpatients 65 years or older at a university hospital in Sweden. Blood flow was measured at depths of 1 mm, 2 mm, and 10 mm using a combined system of laser Doppler flowmetry and photoplethysmography. The blood flow, interface pressure and skin temperature were measured in the sacral tissue before, during, and after load while lying on one standard hospital mattress and three different pressure-redistribution mattresses.

Results: There were significant differences between the three foam mattresses with regard to average sacral pressure, peak sacral pressure, and local probe pressure with the lowest values at the visco-elastic foam/air mattress (23.5 ± 2.5 mmHg, 49.3 ± 11.1 mmHg, 29.2 ± 14.0 mmHg respectively). A greater proportion of subjects had affected blood flow in terms of lack of pressure-induced vasodilation on the visco-elastic foam/air mattress compared to the alternating pressure mattress at tissue depths of 2 mm (39.0% vs. 20.0%, respectively) and 10 mm (56.9 % vs. 35.1%, respectively). Eleven individuals, including subjects in all three subject groups were identified with no pressure-induced vasodilation or reactive hyperemia in any mattress, and this was considered a high-risk blood flow response.

Conclusion: Interface pressure magnitudes considered not harmful during pressure-exposure lying on different pressure-redistribution mattresses can affect the microcirculation in different tissue structures. Despite having the lowest pressure values compared to the other mattresses, the visco-elastic foam/air mattress had the highest proportion of subjects with decreased blood flow indicating a more affected blood flow. Three young healthy individuals were identified with the high-risk blood flow response, indicating an innate vulnerability to pressure exposure and may not benefit from pressure-redistribution mattresses. Finally it was shown that the evaluation of pressure-redistribution support surfaces in terms of mean blood flow during and after tissue exposure is not feasible but assessment of pressure-induced vasodilation and reactive hyperemia could be a new possibility to assess individualized physiological measurements of mechanisms known to be related to pressure ulcer development.

Keyword
interface pressure, pressure-induced vasodilation, pressure ulcer, reactive hyperemia, tissue blood flow
National Category
Nursing Clinical Medicine
Identifiers
urn:nbn:se:liu:diva-109951 (URN)10.12968/jowc.2015.24.8.346 (DOI)000359210200004 ()
Note

Vid tiden för disputationen var publikationen ett manuskript ("Exploring pressure-induced microcirculatory responses in sacral tissue in healthy individuals and inpatients on different pressure-redistribution mattresses")

Funding text: None declared. The study was funded by the Swedish Research Council, the Faculty of Health Sciences at Linkoping University, Region of Ostergotland., King GustafV and Queen Victoria's Freemason Foundation, NovaMedTech, and the European Union Regional Development Fund.

Available from: 2014-08-29 Created: 2014-08-29 Last updated: 2017-12-05Bibliographically approved

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