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Force to restore the shape of an asymmetric extracorporeal tube as the basis for non-invasive pressure measurements
Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
2002 (English)In: International Journal of Artificial Organs, ISSN 0391-3988, E-ISSN 1724-6040, Vol. 25, no 4, 281-289 p.Article in journal (Refereed) Published
Abstract [en]

A zero-balance principle is described where intraluminal pressure is estimated from the counter force needed to restore the tube shape of an elastic extra corporeal tube. The aim was to optimise cross-sectional tube geometry for tube expansion due to pressure and to reduce the sensitivity to variation in mechanical tube characteristics using an experimental statistical and factorial design. The main application is pressure monitoring in blood and dialysate tubes during hemodialysis. Improving the monitoring of the dialysis process will reduce complications, such as sudden decreases in systemic blood pressure or occlusion at the artero-venous fistula. The factorial design indicated strong influence from the geometrical characteristics of the tube as well from the geometrical design parameters of the pressure transducer. We found a consistent relationship between the intraluminal pressure and the applied force needed to restore the tube shape. The modified cross-sectional tube geometry enhances measurement sensitivity and facilitates the desired behavior of tubes during pressure applications.

Place, publisher, year, edition, pages
2002. Vol. 25, no 4, 281-289 p.
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-24543Local ID: 6702OAI: oai:DiVA.org:liu-24543DiVA: diva2:244864
Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2012-12-21
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, RogerAsk, Per

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