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Urodynamic modelling and measurement techniques for assessment of urethral function during micturition
Linköping University, Department of Biomedical Engineering. Linköping University, Department of Biomedicine and Surgery, Urology. Linköping University, Faculty of Health Sciences.
1989 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

According to Griffiths' theory of flow through elastic tubes the urinary flow is controlled by an elastic constriction. The mechanical properties of this flow-controlling zone are described by the intrinsic urethral pressure as a function of cross-sectional area given by the pressure/area relation p(A)=pmo + KnAn, where pmo is the minimal urethral opening pressure, A the cross-sectional area and Kn and n are parameters describing the distensibility of this zone. Values of the three parameters were estimated from pressure/flow data measured during micturition. The detrusor pressure was measured with suprapubic catheters connected to external transducers and urinary flow was recorded with a balance-type flowmeter with a rotating disc. The detrusor pressure as a function of the volume flow was described by pdet(Q)= pmo + LmQm, where Q is the volume flow and Lm and m parameters, and this function was fitted to recorded data. Using this model it is possible to describe urethral flow properties in a standardized way and to identify different biomechanical changes that may cause obstruction.

21 randomly selected elderly men without voiding problems were examined urodynamically and the measured pressure/flow data was analysed according to the described model. 19 of these men had pressure/area relations with a low slope indicating high distensibility of the flow-controlling zone.

The method has also been used to investigate 28 men with benign prostatic hypertrophy, 23 of whom were also studied postoperatively. Preoperatively the minimal opening pressure was substantially elevated compared to normal, parameter Lm was moderately increased and m usually had a low value. The flow-controlling zone therefore had a somewhat reduced distensibility. Postoperatively, the minimal opening pressure was much reduced and the slope of the pressure/flow relation also was lower. The pressure/area relations had lower slopes and the flow-controlling zone could be distended to larger maximum cross-sectional areas. However, in many cases the curve shape suggested that the distension might have been restricted by fibrosis.

A new, non-invasive method based on detection of pressure variations from turbulent urethral flow was described. The method was studied in a urethral flow model for different degrees of obstruction and volume flows. The power spectrum for the detected signals showed increasing intensity and increased frequency content for increasing volume flow and degree of obstruction. The mean power frequency, which can be seen as a limit between the low and the high frequency parts of the spectrum, was used to characterize the spectrum. It was found to be related to the degree of obstruction and the volume flow.

Place, publisher, year, edition, pages
Vimmerby: VTT Grafiska , 1989. , 41 p.
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 223
National Category
Medical and Health Sciences
URN: urn:nbn:se:liu:diva-29456Local ID: 14804ISBN: 91-7870-550-9OAI: diva2:250271
Public defence
1989-12-05, Berzeliussalen, Regionsjukhuset, Linköping, 13:15 (Swedish)

Papers, included in the Ph.D. thesis, are not registered and included in the posts from 1999 and backwards.

Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2013-01-16

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