Non-invasive assessment of urethral resistance

Urine, produced in the kidneys, is temporarily stored in the urinary bladder. Under appropriate circumstances, the bladder muscle (detrusor) contracts and expels the urine through the bladder neck and urethra. The course of voiding mainly depends on the contractility of the detrusor and the urethral resistance. Upon stimulation initiated by the central nerve system, the detrusor shortens which increases the pressure in the bladder. At the same time, the muscle fibres in the bladder neck and in the urethral wall relax which reduces the urethral resistance. When the pressure in the bladder is higher than the pressure in the urethra, urine pushes the urethra open and voiding starts. When the bladder is empty, the detrusor contraction stops, the urethra closes and the kidneys refill the bladder. In men, the prostate enlarges with increasing age, mostly as a result of benign prostatic hyperplasia (BPH). As the prostate surrounds the urethra, and may thus obstruct it, a poor urinary flow (or flow rate) and frequent voiding are typical symptoms relating to BPH. In general, these symptoms are called Lower Urinary Tract Symptoms (LUTS). At present, 25% of the Dutch men aged 40 and above are known to have these symptoms. In men older than 65 years, this percentage is increased to 33%. In the Netherlands only, the population of interest approximates 1 million. This number will increase as the population is ageing. In some cases, a poor flow rate is caused by a weakly contracting bladder and not by an enlarged prostate. In these patients, the efficacy of a surgical procedure aimed at the relief of an obstruction is doubtful. To test if a low flow rate results from an increased urethral resistance, the pressure in the bladder during voiding needs to be measured. A high bladder pressure combined with a low flow rate indicates that a patient has an obstructed urethra. A low bladder pressure combined with a low flow rate indicates that a patient has a weakly contracting detrusor

A Biophysical Model of the Male Urethra: comparing viscoelastic properties of PolyVinyl Alcohol urethras to male pig urethras.

Aims: We aim at developing a non-invasive method for grading and diagnosing urinary bladder outlet obstruction, based on noise recording with a perineal contact microphone during voiding. We found that the noise production during voiding depends amongst others on the viscoelastic properties of the urethral wall. To further test our method, we need a realistic biophysical model of the male urethra. Methods: We made various model urethras with different viscoelastic properties from a 10% aqueous solution of PolyVinyl Alcohol cryogel. We measured the viscoelastic properties of each model and compared them to those of the male pig urethra. The male pig urethra was used, as it is physiologically comparable to the human male urethra. The viscoelastic properties of both model and pig urethras were measured by applying strain to the urethral wall in a stepwise manner and recording the pressure response. We fitted the step-response of a mechanical model to this pressure response and derived the viscoelastic properties from the coefficients of this response. Results: A uniform model urethra that was freeze-thawed three times, with a Y-shaped flow channel was found to best represent the male pig urethra. Conclusion: We consider the three times freeze-thawed model urethra with a Y-shaped flow channel the best model of the human male urethra. And we therefore use this model urethra for studying the relation between noise recording during urine flow and the degree of bladder outlet obstruction.RePub containts a preprint of the article. See http://www.interscience.Wiley.co

Development of salience-driven and visually-guided eye movement responses

Development of visuospatial attention can be quantified from infancy onward using visually-guided eye movement responses. We investigated the interaction between eye movement response times and salience in target areas of visual stimuli over age in a cohort of typically developing children. A preferential looking (PL) paradigm consisting of stimuli with six different visual modalities (cartoons, contrast, form, local motion, color, global motion) was combined with the automated measurement of reflexive eye movements. Effective salience was defined as visual salience of each target area relative to its background. Three classes of PL stimuli were used: with high- (cartoon, contrast), intermediate- (local motion, form), and low-effective salience (global motion, color). Eye movement response times to the target areas of the six PL stimuli were nonverbally assessed in 220 children aged 1-12 years. The development

A novel gaze-based visual search task for children with CVI:A twin study

Visual search is often impaired in children with cerebral visual impairment (CVI), but the current assessment of visual search performance is limited. This study aimed to investigate underlying visual search processes in detail by including gaze-based measurements. Twin brothers (age 11.8 years), one diagnosed with CVI and one with neurotypical development, underwent a newly developed conjunction visual search task while simultaneously their gaze was recorded. In addition to speed and accuracy, we analyzed additional timing and spatial parameters of the search process before and after their initial fixation in the target area. The twin with CVI had good visual sensory functions, but impaired search performance indicated by longer search time and larger search areas. Also, it was observed that in more difficult task conditions, he tended to miss the target, even when fixating on it. These results point towards higher-order visual deficits. This study gives insight into the visual search challenges of a child with CVI. Mapping the search process in detail provided new and distinctive information that can shape more tailored support. Coupling verbal and nonverbal gaze-based outcomes is a promising first step towards a more inclusive nonverbal and nonmotor assessment.</p

A novel gaze-based visual search task for children with CVI:A twin study

Visual search is often impaired in children with cerebral visual impairment (CVI), but the current assessment of visual search performance is limited. This study aimed to investigate underlying visual search processes in detail by including gaze-based measurements. Twin brothers (age 11.8 years), one diagnosed with CVI and one with neurotypical development, underwent a newly developed conjunction visual search task while simultaneously their gaze was recorded. In addition to speed and accuracy, we analyzed additional timing and spatial parameters of the search process before and after their initial fixation in the target area. The twin with CVI had good visual sensory functions, but impaired search performance indicated by longer search time and larger search areas. Also, it was observed that in more difficult task conditions, he tended to miss the target, even when fixating on it. These results point towards higher-order visual deficits. This study gives insight into the visual search challenges of a child with CVI. Mapping the search process in detail provided new and distinctive information that can shape more tailored support. Coupling verbal and nonverbal gaze-based outcomes is a promising first step towards a more inclusive nonverbal and nonmotor assessment.</p

Supporting braille readers in reading and comprehending mathematical expressions and equations

International audienceBraille readers create an overview of an expression by reading one braille character after another or listening to a voice saying the expression or equation aloud. The specific skills and knowledge that mathematics teachers need to assist this complicated process are often lacking. The purpose of this study was to investigate the effect of an intervention consisting of a course focused on braille display support in combination with Text-To-Speech synthesizer for mathematics teachers on the mathematical performances of braille readers. A quasi-experimental approach was taken to answer this question. Five teachers of an experimental group received the intervention whereas the teacher of the control group did not. Both the experimental group, consisting of 10 braille readers, and the control group, consisting of five braille readers, took a pre- and post-test. The results indicated that there was a very small positive effect of the intervention