Estimation of the lag time between detrusor pressure- and flow rate- signals

In a urodynamic measurement setup there is a considerable spatial separation between the uroflowmeter and the location where the detrusor pressure is measured. Therefore, a “time shift” (or lag time correction) has to be applied to one of these signals in order to align related samples in studies where pressure and flow rate are considered simultaneously (e.g., assessment of bladder contractility or bladder outlet resistance). Currently, a heuristic value for this time shift of 0.8 s is applied. In this article, we present a method to estimate the lag time directly from the measurements. Using this method we have found, amongst others, that the mean lag time in our clinic is 0.6 s for males, 0.4 s for females voiding in sitting position, and 1.1 s for females voiding in standing position using a special receptacle in video urodynamics. Furthermore, we found that sphincter/urethral activity during voiding (which causes a drop in flow rate and an accompanying increase in detrusor pressure) is associated (on average) with shorter lag times than straining (when a positive pressure rise accompanies an increase in flow rate). Additionally strong evidence is provided that lag time correction is not a major source of error in urodynamics

Transrectal ultrasound of the prostatic urethra related to urodynamically assessed urethral resistance. A pilot study

In this pilot study on 17 men who underwent urodynamic investigation for various dysuric complaints, real-time transrectal ultrasonography (TRUS) was performed. From the images anatomical parameters were identified that correlated with obstructive urodynamic findings and urethral resistance parameters based on pressure-flow analysis. This study gives support for further clinical investigations to determine the value of TRUS for male patients with dysuric disorders. It also illustrates the anatomical basis of prostatic obstruction as quantified by objective urodynamic parameters

Dependence of male voiding efficiency on age, bladder contractility and urethral resistance: development of a voiding efficiency nomogram

The influence of age, urethral resistance and bladder contractility on voiding efficiency was evaluated by pressure-flow studies in 138 men of a mean age of 60 years (range 18 to 86). From these studies the urethral resistance parameter was calculated and the maximum bladder contraction strength was determined. Premature fading of the bladder contraction was quantified by a bladder contraction strength decay factor. Voiding efficiency was expressed by the parameter of post-void residual urine volume as a percentage of the initial bladder volume. Multiple regression analysis showed that voiding efficiency depended significantly in descending order of importance on urethral resistance, maximum bladder contraction strength and bladder contraction strength decay factor. Patient age was not an independent factor. Maximum bladder contraction strength and bladder contraction strength decay factor were not correlated, suggesting that maximum bladder contraction strength and its decay constitute different properties of bladder contractile function. A voiding efficiency nomogram is proposed, making use of the values for maximum bladder contraction strength and urethral resistance in individual patients. Such a nomogram may have predictive value for the occurrence of acute retention but it must be tested prospectively

The value of screening tests in the detection of prostate cancer. Part II: Retrospective analysis of free/total prostate-specific analysis ratio, age-specific reference ranges, and PSA density

Objectives: The ratio between free and total prostate-specific antigen (PSA) in serum (F/T ratio) was shown to improve the specificity of total serum PSA for the detection of prostate carcinoma in selected populations. In this study, the value of the F/T ratio for screening of prostate cancer was compared with that of age-specific reference ranges for PSA and PSA density (PSAD) by a simulation experiment. Methods: In 1726 men between 55 and 76 years old, 67 prostate carcinomas were detected by application of digital rectal examination (DRE), transrectal ultrasonography (TRUS), and tota

The value of screening tests in the detection of prostate cancer. Part I: Results of a retrospective evaluation of 1726 men

Objectives: The ratio between free and total prostate-specific antigen (PSA) in serum (F/T ratio) was shown to improve the differentiation between prostate carcinoma and benign conditions in selected series of patients. In this study the F/T ratio was analyzed for its ability to improve the specificity of total serum PSA, digital rectal examination (DRE), and transrectal ultrasonography (TRUS) for the detection of prostate cancer in an unselected screening population of men identified in the Rotterdam popu

Reasons for the weak correlation between prostate volume and urethral resistance parameters in patients with prostatism

In an attempt to increase our understanding of the clinical syndrome of benign prostatic hyperplasia (BPH) an analysis was made of the association between prostate volume as measured by transrectal ultrasound and several reported urodynamically determined urethral resistance parameters. Two types of obstruction can be recognized on the basis of urodynamic data: a compressive type characterized by a high urethral opening pressure and a prolonged isovolumetric contraction phase before urine flow can start, and a constrictive type characterized by a normal opening pressure and an increased slope of the urethral resistance relation. A combination of both types is often seen in BPH. In our study, parameters that selectively quantify compression correlate weakly to moderately with prostate volume, whereas parameters that mainly quantify constriction do not correlate at all with prostate volume. Parameters that combine a measure for compression and constriction correlate less well with prostate volume than parameters that mainly quantify compression. The variation in prostate volume was found to determine the variation in urethral resistance by 15% or less depending on the parameter used, which implies that the different pathophysiological mechanisms that can increase urethral resistance in the complex process of clinical BPH are mainly determined by factors other than the volume of the prostate. Thus, despite the lack of correlation between prostate volume and urethral resistance, pressure-flow studies and the determination of urethral resistance parameters provide a valuable contribution to the understanding of the pathophysiology of voiding dysfunction in men with symptoms of prostatism

The additional value of TGFβ1 and IL-7 to predict the course of prostate cancer progression

Background: Given the fact that prostate cancer incidence will increase in the coming years, new prognostic biomarkers are needed with regard to the biological aggressiveness of the prostate cancer diagnosed. Since cytokines have been associated with the biology of cancer and its prognosis, we determined whether transforming growth factor beta 1 (TGFβ1), interleukin-7 (IL-7) receptor and IL-7 levels add additional prognostic information with regard to prostate cancer

Computer-controlled wheelchair ergometer

A new wheelchair ergometer has been designed in which a combination of realistic simulation of wheelchair propulsion-with adjustable parameters for rolling resistance, air drag, wind speed and slope-and force measurement has been realised. The static solution enables the measurement of physiological and kinesiological parameters. All data from force transducers in seat and backrest, torque transducers in the wheels and force transducers in the wheelframes as well as the acquired speed are sampled in a data-acquisition system. An offline curve processor allows the acquired data to be processed with standard or custom-programmed routines. Preliminary results have been added and are discussed

Balancing the harms and benefits of early detection of prostate cancer.

BACKGROUND: The benefits of prostate cancer screening on an individual level remain unevaluated. METHODS: Between 1993 and 1999, a total of 43,987 men, aged 55-74 years, were included in the intervention arm of the European Randomized Study of Screening for Prostate Cancer (ERSPC) section in the Netherlands, Sweden, and Finland. A total of 42,503 men, aged 55-74 years, were included in a clinical population in Northern Ireland. Serum prostate-specific antigen (PSA) <20.0 ng/mL was measured in all men at study entry. All men were followed for prostate cancer incidence and causes of death until December 31, 2006. RESULTS: The adjusted absolute difference in prostate cancer specific mortality between the intervention population and the clinical population increased with increasing PSA level at study entry, ie, 0.05 per 10,000 person-years for men who had a serum PSA level of 0.0-1.9 ng/mL and 8.8 per 10,000 person-years for men who had a serum PSA level of 10-19.9 ng/mL. To evaluate the risks of early detection, the number needed to investigate (NNI) and number needed to treat (NNT) to save 1 death from prostate cancer were calculated. Both NNI and NNT were higher for those who had lower PSA levels at study entry. The NNI was 24,642 men for patients who had a serum PSA level of 0.0-1.9 ng/mL and was 133 men for patients who had a serum PSA level of 10-19.9 ng/mL; the NNT was 724 men for patients who had a serum PSA level of 0.0-1.9 ng/mL and was 60 men for patients with a serum PSA level of 10-19.9 ng/mL. CONCLUSIONS: For men with a low serum