| 1. |
- Ask, Per, et al.
(author)
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A SHORT-TIME-DELAY URINARY FLOWMETER
- 1985
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In: Neurourology and Urodynamics. - : Wiley. - 0733-2467 .- 1520-6777. ; 4:3, s. 247-256
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Journal article (peer-reviewed)abstract
- A urinary flowmeter has been designed, using a quickly rotating disc and a balance principle. The flowmeter has a fast and accurate response to changing flows. The time delay of the flowmeter is less than about 0.25 s. The improved accuracy in recording urinary flow using the presented flowmeter should make it possible to extract more information from the detrusor pressure and urinary flow relations, relevant for assessing lower urinary tract function.
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| 2. |
- Ask, Per, et al.
(author)
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PRESSURE MEASUREMENT TECHNIQUES IN URODYNAMIC INVESTIGATIONS
- 1990
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In: Neurourology and Urodynamics. - : Wiley. - 0733-2467 .- 1520-6777. ; 9:1, s. 1-15
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Journal article (peer-reviewed)abstract
- It is apparent that the use of accurate pressure measurement techniques is essential for the outcome of urodynamic investigations. The aim of this paper is to estimate the demands on urodynamic pressure measurements and to review the properties of various techniques used. For the infused catheter technique, the dynamic properties are very much dependent on the complicance of the infusion system. With optimal infusion, the bandwidth and the pressure rise rate seem to be sufficient for most applications. Intraluminal microtransducers have a high bandwidth, but a certain fiber optic transducer cannot accurately measure mechanical pressure in the collapsed urethra. The principal differences in measuring hydrostatic pressure between the infused catheter technique and microtransducers should be observed. Flexion artefacts are a problem when measuring urethral pressure profiles. Newly developed transducers may offer a solution to this problem.
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| 3. |
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| 4. |
- Språngberg, Anders, et al.
(author)
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PRESSURE-FLOW STUDIES PREOPERATIVELY AND POSTOPERATIVELY IN PATIENTS WITH BENIGN PROSTATIC HYPERTROPHY - ESTIMATION OF THE URETHRAL PRESSURE-FLOW RELATION AND URETHRAL ELASTICITY
- 1991
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In: Neurourology and Urodynamics. - : Wiley. - 0733-2467 .- 1520-6777. ; 10:2, s. 139-167
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Journal article (peer-reviewed)abstract
- Pressure/flow studies were performed in 28 men with benign prostatic hypertrophy. Twenty-three of the men were also studied postoperatively. Urethral function during micturition was quantified by the urethral pressure/flow relation, P(det) = P(mo) + L(m) Q(m), where P(det) is detrusor pressure, P(mo) is minimal opening pressure, Q is flow rate, and m and L(m) are parameters. Using this method to quantify urethral function, three urodynamically different types of obstruction can be defined. In the first of these, P(mo) is elevated corresponding to Schafer’s compressive obstruction. The second is a constrictive type of obstruction in which m greater-than-or-equal-to 4/3 and L(m) is elevated and the third is a low-compliant type of obstruction in which m less-than-or-equal-to 1 and L(m) is elevated. The two latter types of obstruction may be combined with a compressive obstruction. The preoperative pressure/flow relations were mostly characterized by a very high P(mo), a moderately elevated L(m), and a low m. Thus the majority of patients had a combination of compressive and low-compliant obstruction. Postoperatively, micturitions were much improved and the pressure/flow relations often had an even lower P(mo) than normal, a normal L(m), and a high m. From the pressure/flow relations, the elasticity of the flow-controlling zone can be estimated and described by the urethral pressure/area relation, p(A) = P(mo) + K(n) A(n), where p(A) is the intrinsic urethral pressure, A is the cross-sectional area of the flow-controlling zone and K(n) and n are parameters describing the distensibility of the flow-controlling zone. Preoperatively, the flow-controlling zone had a low distensibility. The shape of the curve suggested that the urethra could have been distended further by higher pressure. Postoperatively, the urethra was distended to larger cross-sectional areas, but in many cases the shape of the curve suggested that distension was restricted by fibrosis. Median and range values for the model parameters as well as discriminating limits between the preoperative micturitions and micturitions in elderly men without voiding problems are presented. The exponent m is not perfectly reproducible but tends to be the same if a person performs several micturitions. The residual sum of squares is often increased more than 100% if an exponent m value other than the optimal one is used for curve fitting. Results when the micturitions were analysed with Schafer’s model and classified using the maximum flow/pressure at maximum flow diagram recommended by the International Continence Society are also shown.
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| 5. |
- Spånberg, Anders, et al.
(author)
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PRESSURE-FLOW STUDIES IN ELDERLY MEN WITHOUT VOIDING PROBLEMS - ESTIMATION OF THE URETHRAL PRESSURE-FLOW RELATION AND URETHRAL ELASTICITY
- 1990
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In: Neurourology and Urodynamics. - : Wiley. - 0733-2467 .- 1520-6777. ; 9:2, s. 123-138
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Journal article (peer-reviewed)abstract
- The flow in the urethra is controlled by an elastic constriction, the flow-controlling zone. The distensibility of this zone is described by the pressure/area relation, which gives the static pressure as a function of the cross-sectional area at the flow-controlling zone. The pressure/area relation can be calculated from the pressure/flow relation, which is estimated from the pressure/flow plot obtained at a urodynamic examination. In this study the urethral pressure/flow and pressure/area relations were estimated for 21 randomly selected men (62–75 years old) without voiding problems.Nineteen of 21 persons in this group had pressure/flow relations with a low slope. This corresponds to a low slope in the pressure/area relation indicating high distensibility of the flow-controlling zone, which for 18 persons was estimated to be distended to areas larger than 10 mm2 during micturition. Twenty persons had a minimal urethral opening pressure below 55 cm H2O. The estimated pressure/area relation was linear in 59% of the micturitions, indicating that the flow-controlling zone could have been distended to a larger cross-sectional area, if the bladder had achieved a higher pressure. The 10th–90th percentiles for maximum flow and detrusor pressure at maximum flow were 7.2–24.3 ml/s and 24–76 cm H2O, respectively. Four persons had low flow and low pressure, indicating diminished detrusor contractility with age. Twenty-four percent of the persons had unstable bladder contractions with a pressure rise < 15cm H2O and 19% with a pressure rise < 15cm H2O.
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| 6. |
- Spånberg, Anders, et al.
(author)
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QUANTIFICATION OF URETHRAL FUNCTION BASED ON GRIFFITHS MODEL OF FLOW THROUGH ELASTIC TUBES
- 1989
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In: Neurourology and Urodynamics. - : Wiley. - 0733-2467 .- 1520-6777. ; 8:1, s. 29-52
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Journal article (peer-reviewed)abstract
- Griffiths' model of flow-through elastic tubes makes it possible to relate the elastic properties of the flow-controlling zone to the pressure/flow relation of the urethra. In this work the pressure function p(A) = Pmo + Kn An, where A is cross-sectional area, Pmo the minimal opening pressure, and Kn and n parameters describing urethral distensibility, describes the elastic properties of the flow-controlling zone. By curve-fitting in the pressure/flow plot, the three parameters pmo, Kn, and n can be estimated analytically. Using this model it is possible to identify three different biomechanical changes that may cause obstruction. First, pmo may be elevated. Second, the urethra can be distended to a certain area only, corresponding to high values of Kn and n. Third, the urethra can be distended but a higher-than-normal pressure increase above Pmo is needed, Kn is high, and n is low. With this model it is possible to quantify urethral function for both scientific and clinical purposes.
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