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Cross-sectional changes in an asymmetric tube with bearing on non-invasive pressure measurements
Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
Linköping University, Department of Mechanical Engineering. Linköping University, The Institute of Technology.
Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
2003 (English)In: Technology and Health Care, ISSN 0928-7329, E-ISSN 1878-7401, Vol. 11, no 1, 11-20 p.Article in journal (Refereed) Published
Abstract [en]

This study aims at investigating the radial dimensional changes, as a result of an applied intraluminal pressure for an elastic tube with non-uniform cross section. The study is related to a method for non-invasive pressure measurement using the extracorporeal tube as part of the sensor. The intended application is for monitoring of pressure in the blood and dialysate tubes during haemodialysis. The intention is to find a tube cross-section geometry that results in an expansion of the tube so that it is suitable to use as a component in a pressure sensor. The tube should have high radial compliance and expand in a well-defined manner to be able to transfer the intraluminal pressure to a transducer element sensing the radial force. Radial expansion was studied experimentally for tubes with different cross-section geometries. For small tube expansions the resolution in the experimental measurements was not sufficient to study the radial expansion. In this case, numerical simulation was performed. We conclude that a tube with essentially elliptic outer surface and circular inner surface, with a relation of 1:2 between the size of the thin and thick wall, results in a radial expansion upon application of pressure indicating that this tube is suitable for use as part of a sensor.

Place, publisher, year, edition, pages
2003. Vol. 11, no 1, 11-20 p.
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-24496Local ID: 6620OAI: oai:DiVA.org:liu-24496DiVA: diva2:244817
Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2017-12-13
In thesis
1. Monitoring principles for haemodialysis
Open this publication in new window or tab >>Monitoring principles for haemodialysis
2002 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis deals with non-invasive monitoring techniques for haemodialysis. Three applications in particular have been investigated: Blood pressure measurements in the extra corporal circuit, the relationship between UV measurements and dialysate urea concentration and photoplethysmography (PPG) in haemodialysis patients.

A non-invasive pressure sensor as an integrated part of the extracorporeal tube circuit was developed using modified cross-section tube geometry. The expansions of the modified tubes with different cross-sectional geometries were studied upon application of pressure, both experimentally and numerically, using the finite element method. Factorial design was used to study the relationship between pressure in the tube and force needed to restore the expanding tube to its original dimension. This investigation was performed for different tube cross-sectional geometries. A pressure sensor was designed, based on the previously obtained findings. The evaluation of the pressure sensor showed that the output corresponded well to applied pressure (R2=0.99).

An UV-method for studying waste products in the dialysate has recently been developed by our research group. In the present study, it was investigated how the relationship between UV-absorption and dialysate urea concentration was affected by the treatment settings, patient anamnesis and prescribed pharmaceuticals. A mathematical model was proposed which includes these effects. Multiregression analysis indicated the possibility of performing individual estimates of urea concentration from UV-absorption.

During haemodialysis, the patient's cardiovascular system is affected when excess fluid is extracted, which may result in blood pressure fluctuations. In the present study, a novel PPG method for monitoring haemodynamic changes during dialysis was investigated. The performed study indicates that PPG measurements relate to haemodynamic changes and may thus be useful in the patient monitoring. However, the relationship is complex and needs further studies.

Place, publisher, year, edition, pages
Linköping: Linköpings universitet, 2002. 45 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 737
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-24563 (URN)6728 (Local ID)91-7373-270-2 (ISBN)6728 (Archive number)6728 (OAI)
Public defence
2002-05-21, Aulan, Administrationshuset, Universitetssjukhuset, Linköping, 10:15 (Swedish)
Opponent
Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2012-12-21

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Andersson, RogerLoyd, DanAsk, Per

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