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Monitoring principles for haemodialysis
Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
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: urn:nbn:se:liu:diva-24563Local ID: 6728ISBN: 91-7373-270-2 (print)OAI: oai:DiVA.org:liu-24563DiVA: diva2:244884
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
List of papers
1. Cross-sectional changes in an asymmetric tube with bearing on non-invasive pressure measurements
Open this publication in new window or tab >>Cross-sectional changes in an asymmetric tube with bearing on non-invasive pressure measurements
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.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-24496 (URN)6620 (Local ID)6620 (Archive number)6620 (OAI)
Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2017-12-13
2. Force to restore the shape of an asymmetric extracorporeal tube as the basis for non-invasive pressure measurements
Open this publication in new window or tab >>Force to restore the shape of an asymmetric extracorporeal tube as the basis for non-invasive pressure measurements
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.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-24543 (URN)6702 (Local ID)6702 (Archive number)6702 (OAI)
Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2017-12-13
3. An asymmetric dialysis tube as an integrated part of a pressure-monitoring sensor
Open this publication in new window or tab >>An asymmetric dialysis tube as an integrated part of a pressure-monitoring sensor
2001 (English)In: Technology and Health Care, ISSN 0928-7329, E-ISSN 1878-7401, Vol. 9, no 5, 417-425 p.Article in journal (Refereed) Published
Abstract [en]

A sensor has been designed consisting of a tube holder with a force transducer and a tube with a modified cross-section. The holder has a lid that encloses the tube. By having a stiff holder and a compliant tube, the idea is that the intraluminal pressure in the tube can be obtained from the measured force. The method is intended for non-invasive pressure measurements in blood or dialysate tubes.

We have used a tube cross-sectional geometry where the outer surface is elliptic and the inner surface is circular with a relation of 2:1 between the thinnest and thickest tube sides. The pressure transducer system shows a linear relationship between the applied pressure and the sensor output (r = 0.999). Within the temperature range, 32°–36°C, which corresponds to the blood and dialysate temperatures, the sensor accuracy is within ±0.8 kPa (±6 mm Hg). This indicates that the sensor should be clinically useful during dialysis and similar applications.

Keyword
Non-invasive pressure sensor, asymmetric tube, dialysis, extracorporeal tube, profile analysis
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-29584 (URN)14961 (Local ID)14961 (Archive number)14961 (OAI)
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2017-12-13
4. Analysis of the relationship between UV-absorbance of solute contents during a dialysis session
Open this publication in new window or tab >>Analysis of the relationship between UV-absorbance of solute contents during a dialysis session
Show others...
(English)Manuscript (preprint) (Other academic)
Abstract [en]

In this paper, the influence from patient anamnesis and haemodialysis session specifications onto the relationship between obtained ultra violet (UV) absorbance and urea concentration in the spent dialysate were discussed. A characterisation of the relationship was done by an intercept value and a slope. Recently, a new a dialysate monitoring device, using UV- absorbance, been developed by our group which has found a relationship between the UV- absorbance and waste products in the dialysate but this relationship vary between patients. In the present investigation, 13 patients performing totally 84 sessions were characterised using 31 possible affecting parameters. Using a multi-regression analysis 11 parameters were found significant as affecting parameters. In a novel mathematical model approach the obtained UV- absorbance and incorporating possible affecting parameters we could predict urea concentration from the UV-absorption in the spent dialysate in the total material of patients and dialysis sessions. For all the 84 sessions R2 between 0.938 and 0.996 were obtained. A performed analysis of variance rejects the assumption of equal conditions for the relationship between diabetics and non-diabetics patients in the material (F=5.2 for intercept and F=14.4 for slope). The urea concentration could be estimated with an accuracy of 11% (one standard deviation) which is normally clinically sufficient. The non-invasive UV -absorption method therefore seems to have great potential for monitoring and control haemodialysis sessions.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-86685 (URN)
Available from: 2012-12-21 Created: 2012-12-21 Last updated: 2012-12-21
5. Non-invasive monitoring of haemodynamic changes in haemodialysis patients using photoplethysmography (PPG)
Open this publication in new window or tab >>Non-invasive monitoring of haemodynamic changes in haemodialysis patients using photoplethysmography (PPG)
2002 (English)Manuscript (preprint) (Other academic)
Abstract [en]

Presently there is no simple non-invasive method to monitor haemodynamic changes during haemodialysis but such a method is highly needed. This study aims at investigating the possibility to monitor such changes during a single haemodialysis session using a photoplethysmography method (PPG). This non-invasive method illuminates a proportion of the patients skin and the received PPG-signal reflects local blood flow. The haemodialysis sessions were performed as in normal routine with more frequently performed blood pressure measurements by an oscillometric method or with continuous intra arterial blood pressure measurements. The obtained PPG-signals are linked to the blood pressure changes and are affected by the ultrafiltration rate and drugs administrated during the session. The relation between the blood pressure changes and the changes in the different PPG components seems however to be complex and need to be investigate further. The PPG-method shows promises, which is emphasised by the strong need of a non-invasive monitoring method.

Keyword
haemodialysis, photoplethysmography, blood flow, haemodynamics
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-54997 (URN)
Available from: 2010-04-27 Created: 2010-04-27 Last updated: 2012-12-21

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