Account for high flow rate-low detrusor pressure voids in female: Contribution of VBN model.

INTRODUCTION: Nomograms using the VBN model of women micturition allowed evaluating detrusor contractility (k) and urethral obstruction (U) from pressure-flow (PFs) recordings. While the model worked for most of the patients, an intriguing result, negative U value was observed for patients with high flow-low detrusor pressure (Qp voids). To explain that condition, our hypothesis was a weak urethral resistance to dilatation or increased expansibility (URD). METHODS: The area offered to the fluid at each point of the urethra (its dilatation) is a function of the time depending difference between inside and outside pressures. In the VBN model, this function is sigmoid-like, the same for all women. For Qp voids, Qrecorded was more higher than it would be with the recorded pressure (VBN analysis). So, modeling allowed computing abnormally increased urethral wall expansibility (URD) whose consequence would be an increased flow. RESULTS: Among 222 non-neurologic women referred for investigation of various lower urinary tract symptoms, 27 (mean age 66.3±11.4 y) had Qp void: Qmax=27±6mL/s; pdet.Qmax =7.5±4.7cm H2O. Mean URD value was .36±.67. Introduction of URD in a modeled analysis of urodynamic traces led to a good fitting between recorded and computed traces for the 27 Qp. CONCLUSION: Mathematical modeling of micturition allows proposing an explanation of the unexpected observations of Qp voids. They would be due to abnormal urethral wall elasticity. Despite major challenges measurement of this elasticity would be the next step. LEVEL OF EVIDENCE: 3.

Comparison of indices allowing an evaluation of detrusor contractility in women.

AIMS: To compare 3 detrusor contractility indices, projected isovolumetric pressure (PIP-BCI), PIP1, and k from the VBN mathematical model, for women referred for evaluation of various lower urinary tract symptoms (LUTS) in relationship to age, presenting complaint and urodynamic diagnosis. METHODS: Urodynamic tracings of non-neurologic women were analyzed. Three indices of detrusor contractility were measured from the pressure-flow study. Exclusion criteria were voided volume<100mL, stage>2 prolapse, interrupted flow, abdominal straining. Age sub-groups were pre-, peri- and post-menopause. Urodynamic diagnosis included incontinence findings and detrusor activity during voiding. RESULTS: Main complaint was incontinence (354 women); 95 women (Other) had non-incontinence LUTS. PIP-BCI, PIP1 and k decreased significantly with ageing in each sub-group. PIP-BCI was significantly different between MUI and Other (P=.0259) while PIP1 was significantly higher in UUI vs. Other (P=.0161) and k in UUI vs. SUI (P=.0107), MUI (P=.0010) and Other (P=.0224). Low value of PIP-BCI for bladder outlet obstruction vs. detrusor overactivity while PIP1 and k values were high and similar for these two diagnoses and a high value of PIP-BCI for detrusor overactivity with impaired contractility close to the value for bladder outlet obstruction while PIP1 and k were low. CONCLUSION: Evaluation of detrusor contractility in women is easily obtained using indices PIP-BCI and PIP1 or using the VBN nomogram giving indice-parameter k. PIP1 and parameter k produced comparable and consistent results with the urodynamic diagnosis while PIP-BCI leads to inconsistencies. LEVEL OF EVIDENCE: 4.

Is bladder voiding efficiency useful to evaluate voiding function in women older than 65 years?

AIMS: The aims of the study were to evaluate the reproducibility of bladder voiding efficiency (BVE) between free flow (FF) and intubated flow(IF) in old women, and to search for a relationship of this index with complaint and urodynamic diagnosis. METHODS: Urodynamic tracings of non-neurologic women referred for investigation of various lower urinary tract symptoms (LUTS) were analyzed. Urodynamic study included one FF followed by one cystometry and IF. Post void residual volume (PVR) was measured using a Bladder-scan. Exclusion criteria were voided volume<100ml and prolapse of grade>2. RESULTS: One hundred and ninety women met the study criteria. The mean age was 74±6 years [65-96years]. The main complaint was urinary incontinence: stress (26), urge (53) and mixed (56). Forty-four women had various complaints without incontinence. Overall BVE IF (77.6±25.8) was significantly lower than BVE FF (90.4±15.3) (P<.0001). Age sub-groups stratification led similar results. BVE IF was significantly lower than BVE FF in women with incontinence whatever the cause. Urodynamic diagnosis was posed according to the ICS/IUGA recommendations and 2 sub-groups defined according with involvement of detrusor. BVE IF was significantly lower than BVE FF for detrusor dysfunction, except for detrusor overactivity. CONCLUSION: In this large cohort of old non-neurologic women studied urodynamically for a variety of LUTS, BVE is higher when evaluated from a FF whatever age and for complaint of urinary incontinence. In addition, a low BVE value from an IF may suggest a detrusor dysfunction. LEVEL OF EVIDENCE: 4.

Do urodynamics provide a better understanding of voiding disorders in women over 80?

AIMS: Population ageing has as consequence an increasing number of women older than 80 years with lower urinary tract symptoms (LUTS). Despite old age, urodynamic study is often performed to diagnose the cause of LUTS. Our purpose is to discuss the contribution of urodynamics to manage that population. METHODS: Urodynamic studies of 169 consecutive women older than 80 years, respectively 124 non-neurological (non-N) and 45 neurological (N), were retrospectively analysed. RESULTS: Number of co-morbidities was lower in non-N (2.5 vs. 3.1) with predominance of cardiovascular and endocrinology while musculo-skeletal, cognitive and previous pelvic surgery predominated in N. Among main complaint, incomplete retention or dysuria was more frequent in N while incontinence and frequency were predominant in non-N. More frequent urodynamic diagnosis (UD) was "normal" i.e. non contributive (25.0%) and intrinsic sphincter deficiency (ISD=21.7%) in non-N, detrusor overactivity (DO=42.2%) and detrusor underactivity (DU=38.8%) in N. In non-N, there were 94 treatment proposals based on the complaint when UD was "normal" and on UD for DO, DU and ISD. In N, treatment proposals were mainly prompted voiding or self-catheterization based on DU diagnosis. CONCLUSION: Usefulness of urodynamics to manage LUT dysfunction in women older than 80 y is greatly dependent on their neurological status. In non-neurological women this is non debatable but proposed treatment needs to take into account existing co-morbidities. In neurological women the main usefulness is to unmask DU and to propose the best management in order to avoid complete retention. LEVEL OF EVIDENCE: 4.

Usefulness of an algebraic fitting of nomograms allowing evaluation detrusor contractility in women.

AIMS: Nomograms based on Valentini-Besson-Nelson (VBN) model implying only 3 measurements (filling bladder volume, maximum flow-rate [Qmax] and detrusor pressure at Qmax) were recently developed to evaluate detrusor contractility (k) and urethral obstruction (U) in women. As their algebraic fitting leads to fast evaluations (Excel® software), our aims were applications to populations of non-neurologic women without and with bladder outlet obstruction (BOO). METHODS: The software was applied to measurements obtained during pressure flow studies. Hidden hypothesis of nomograms were no significant contribution of abdominal pressure between onset of flow and Qmax and standard nervous excitations until Qmax. Studied populations were 202 women without symptom suggestive of obstruction and 125 women with proven anatomical urethral obstruction who underwent urodynamic study. RESULTS: For non-obstructed women, a good agreement was found between the values of k and U obtained using nomograms or a complete VBN analysis of the recorded curves. Whatever the obstructive status, there was a good correlation between the value of k and U. Evolution with ageing was similar with higher values of k and U in the BOO group. Curves k(age) and U(age) gave coefficients allowing an age adjustment. The high k value in the detrusor overactive (DO) group was consistent with a similar effect to that of BOO on the detrusor. CONCLUSION: Evaluation of detrusor contractility (k) and urethral obstruction (U) can be obtained from the point of Qmax during pressure-flow study. Evolution with ageing is similar with (higher values) or without BOO. DO also induces an increased detrusor contractility. LEVEL OF EVIDENCE: 4.

Detrusor contractility in women: Influence of ageing and clinical conditions.

AIMS: We assume that the voiding process in women is governed by the detrusor contractility and a "urethral resistance". The value of these 2 parameters, respectively named k and U in the VBN (Valentini-Besson-Nelson) mathematical model of micturition is deduced from the VBN analysis of pressure-flow recordings (PFs). Our objectives were to search for a correlation between these 2 parameters and clinically relevant variables such as chief complaint, urodynamic diagnosis (UD), and age by decades. METHODS: PFs from 125 non-neurogenic women (mean age 58.0±17.2years [range 20-90years]) were retrospectively analyzed using the VBN model. VBN criteria for inclusion were maximum flow rate>2mL/s, voided volume>100mL, and non-interrupted flow. Evaluated parameters were k (without unit) and U (unit: cm H2O). Standard values were k=1.0 and U=0. RESULTS: VBN parameter ranges were k [0.14-1.55] and U [0.0-73.0cm H2O]. There was a significant correlation between k and U for the whole population (P<0.0001) with k=(.259+0.015*U) (R(2)=0.723) and each chief complaint. For UD, significant difference comparing k and U in phasic detrusor overactivity with intrinsic sphincter deficiency and urodynamic stress incontinence was noted. In sub-groups defined according to decades of age, the values of k and U remained similar in sub-groups for those who are less than 50years old and decreased regularly with ageing. CONCLUSION: The detrusor contractility can be easily evaluated in women; lower than in men, its range is less spread out but also adjusted to compensate a "urethral resistance". Phasic detrusor overactivity and post-menopausal age significantly affect detrusor force value. LEVEL OF EVIDENCE: 3.

Repeatability and variability of baropodometric and spatio-temporal gait parameters--results in healthy subjects and in stroke patients.

AIMS OF THE STUDY: Our purpose was to determine the repeatability and variability of baropodometric and spatio-temporal gait parameters in both hemiparetic patients and healthy subjects. HYPOTHESIS: parameters with a good repeatability and a low variability could be used to follow gait evolution. POPULATION AND METHOD: Twelve stroke patients and 10 healthy subjects were included. Each participant performed trials (F-Scan® system and Bessou Locometer) at 48 h intervals under identical conditions. The following parameters were analyzed: displacement of the center of pressure (COP), peaks of pressure under forefoot and hindfoot, step length, single and double support time, and walking velocity. Comparisons were made within and between sessions, inter-trials and between sides. RESULTS: Neither visit effects in either population nor side effects in healthy subjects were observed. Repeatability assessed by the intraclass correlation coefficient ("ICC agreement" ICC) was excellent to adequate overtime for anterior-posterior (AP) displacement of the COP, step length, simple support time and walking velocity in both hemiparetic patients (ICC 0.92; 0.84; 0.91; 0.94) and healthy subjects (ICC 0.85; 0.44; 0.64; 0.56). The coefficient of variation (CV) was low in paretic side for AP and single support time, and at a less degree for the lateral deviation of the COP (ML) and the posterior margin (PM). CONCLUSION: In this study, baropodometric (AP and PM) and spatio-temporal gait (step length, single support time and walking velocity) parameters were found to show good repeatability overtime; these parameters are the ones most likely to be useful in assessing the effects of treatments that are proposed to improve gait in stroke patients.

[Non-invasive urodynamics in male patient]. / Méthodes d'urodynamique non invasive chez l'homme.

PURPOSE: Pressure-flow studies are currently recognized as the criterion standard to quantify urethral obstruction and its consequence on detrusor contractility. These tests have some disadvantages: they are invasive, time-consuming and expensive and entail risk of disease for the patient. Less invasive methods have been proposed to give the same results without the disadvantages. In this study, we conducted a critical analysis of the devices and techniques and their results. METHOD: After a brief reminder of the general behavior of the flow in an obstructed urethra, we describe the main non-invasive techniques: penile urethral compression-release (PCR), cuffs, and condoms. Using the VBN method, we tried to quantify data from these techniques to specify the relation with the usual parameters of bladder outlet obstruction. RESULTS: In the absence of brisk change of the flow rate, the voiding phases are easily analyzed. With minor corrections, recorded external or cuff pressures could be used in the ICS nomogram; unfortunately, these pressures are greatly modified by perturbations of the nervous control. The spike of flow (due to urine storage in the urethra) observed at resumption of flow after each interruption presents mathematical difficulties for quantitative and reliable modeling but could give a consistent empirical interpretation. CONCLUSION: Of the reported non-invasive tests, all except PCR have an important instrumental heaviness and induce strong perturbations of the nervous control. If they cannot allow an accurate quantification of urethral obstruction and detrusor contractility, they could allow for classification of benign prostatic hypertrophy (BPH) patients. Despite the mathematical problems set by the theory of spikes, the empirical use of the spikes amplitude could perhaps be clinically useful.

[Quantification of bladder-outlet obstruction in males: standard method vc VBN method]. / Quantification de l'obstruction chez l'homme: comparaison des méthodes usuelles avec la méthode VBN.

GOAL: To compare the merits of two methods, standard (Abrams-Griffiths number, Schafer's classification, etc.) and VBN, to study bladder-outlet obstruction in men with benign prostatic hyperplasia (BPH). MATERIAL AND METHODS: The parameters deduced from both methods and from repeated pressure-flow studies were computed for a population of patients with BPH. Correlation coefficients between standard and VBN parameters were systematically evaluated. Test-retest reliability and inter-rater reliability of the VBN parameters were investigated. RESULTS: The VBN obstruction parameter was linearly corelated to the A-G number (R = 0.992) and thus is related to the provisional ICS obstruction nomogram. A simple modification to the standard index projected isometric pressure (PIP) yields an mPIP parameter strongly correlated with the VBN detrusor contraction-strength parameter (R = 0.962). VBN analysis reveals minor phenomena such as premature fading of the detrusor contraction to be responsible for much of the void-to-void variability of pressure-flow studies. Consequently, the primary VBN obstruction and contraction-strength parameters exhibit better test-retest and inter-rater reliability than the standard parameters and are less sensitive to changes in testing circumstances (bladder volume, urethral catheter size and psychological factors). CONCLUSION: With the standard approach to test bladder obstruction, two values: A-G and mPIP, derived from pressure-flow studies, best qualify the patient's voiding status. These parameters are simple to calculate but are sensitive to testing variations and minor phenomena. The VBN approach is more complicated, but its parameters for obstruction and detrusor contraction strength are less dependent on testing variations.

[Urodynamics and uterine fibroid. Is there a specific parameter?]. / Urodynamique et fibrome utérin. Existe-t-il un paramètre spécifique?

AIM OF STUDY: To search for a urodymamical parameter and/or a VBN parameter (deduced from a modelized analysis of uroflows) which could characterize the voiding dysfunctions due to a uterine fibroid. POPULATION AND METHODS: Thirty women (31-69 years) with a uterine fibroid (exclusion criteria: neurological disease, diabetes mellitus, previous pelvic surgery, grade > I prolapse) underwent one urodynamic session which included the successive tests: free uroflow, urethral profilometry, cystometry and, if possible, a second free uroflow. Twenty-eight patients complained from stress urinary incontinence. Modelized analysis of the flow curves was performed in order to determine the value of two VBN parameters: urethral parameter g and recruitment ratio rr (which quantify the ratio of firing motor neurons during detrusor contraction). RESULTS: The fibroid (known for 23 subjects) was detected during gynaecological examination in seven cases. No significant change of the value of one urodynamical parameter which could be linked to the uterine fibroid rather than the urinary disorder has been found. Some urethral constrictive obstruction exists for 18 patients (g = 0.40 +/- 0.15) but is not meaningful. In the whole population, an effective abdominal pressure is found in 78% of the analyzed micturitions. CONCLUSION: Some urinary disorders result from the presence of a uterine fibroid; they are significantly improved by simple hysterectomy. If urodynamics does not have any specificity, concomitant physical examination allows to detect fibroids with only urinary symptomatology.

[Detrusor activity and motor neurons firing during micturition: analysis by means of modeling of urodynamic tracings]. / Comportement permictionnel du détrusor et activité des neurones moteurs : approche par analyse modélisée des enregistrements urodynamiques.

BACKGROUND: To use a computer assisted analysis of urodynamic tracings (VBN method) in order to propose a quantitative description of the relationship between detrusor activity and firing of efferent motor neurons. METHODS: Modeling of the nervous control implies three definitions of the detrusor excitation: (1) related to the contractile force (EF), (2) related to the calcium turnover (ECa) and (3) ratio of firing motor neurons (rr). The associate variables have been computed from each uroflow recording of healthy volunteers (male and female) and patients (107 men with lower urinary tract symptoms due to benign prostatic enlargement and 138 women with stress urinary incontinence). RESULTS: A "standard excitation" governs all the voidings of healthy volunteers. For 47% of male patients and 75% of female patients, a non-standard excitation is observed: beginning as the standard excitation, then sudden break at a time tc (9.7 +/- 2.5 s for male and 4.0 +/- 2.7 s for women). rr has an all-or-none value in case of standard excitation and exhibits a two steps behavior with after tc: = 0.53 +/- 0.21 for men and 0.41 +/- 0.18 for women (non-significant despite the difference in the origin of disease). CONCLUSION: VBN computer analysis of urodynamic tracings allows to propose a description of the detrusor nervous control: (1) an on-off nervous order rules the "standard" detrusor activity, and (2) a feedback, which probably starts at the urethral level, acts to switch an on-off reduction of the detrusor activity in the other cases.

[Are age and urodynamic data correlated in women with stress urinary incontinence (SUI)?]. / Existe-t-il une corrélation entre l'âge et les données du bilan urodynamique chez la femme présentant une incontinence urinaire d'effort (IUE)?

PURPOSE: Our aim was to evaluate the impact of age on lower urinary tract function in women by means of urodynamics and modelized analysis of the recorded free uroflow curves. MATERIAL AND METHODS: One hundred and fifty three women (age range: [30-93 years]; 6 decades A to F) with only SUI complaint underwent a urodynamic evaluation which included initial free uroflow, urethral pressure profile, cystometry and final free uroflow at bladder functional capacity. Modelized analysis was performed using the VBN mathematical micturition model; from comparison between recorded and computerized theoretical flow curves this model allows to determine two characteristic parameters: one of urethral obstruction and one of detrusor efficiency. RESULTS: No age-related changes were found in bladder capacity, peak flow rate in the first void and post residual volume. A significant increase of peak flow rate was noted in the second void for D and older. Bladder compliance decreased only from E. As usually described a decrease with age of the maximum urethral closure pressure occurred while the functional urethral length decreased only from E. A flat distribution of the VBN parameters was observed. DISCUSSION-CONCLUSION: This study shows the absence of age-associated changes in both urodynamic data and VBN parameters in a population of women with SUI and without any other disease. These findings reinforce the idea that chronological age does not strongly correlate with the physiological status.

A mathematical micturition model to restore simple flow recordings in healthy and symptomatic individuals and enhance uroflow interpretation.

We describe a model and report a new method to extract quantified data from the simple analysis of whole uroflow curves in healthy and symptomatic individuals. Recorded flow curves were compared with the curves theoretically predicted from a mathematical micturition model. This model was developed by relating each physiological event occurring during micturition to a set of mathematical equations. Due to improvements in speed of computer calculations, a very fast and adaptable mathematical micturition model became available. A total of 302 uroflow curves from 142 patients (61 men and 81 women) were studied. The control group consisted of seven men and 25 women; the symptomatic groups comprised 54 men and 56 women. The mathematical model was applied to analyze all the recorded curves. For patients with lower urinary tract symptoms, specific modelization parameters were introduced according to the clinical condition to be tested. Using two compulsory (patient sex and voided volume) and two optional parameters (clinical condition and urethral catheter size), our mathematical model was able to produce uroflow calculated curves similar to observed curves. In the control group, the calculated and recorded uroflow curves were found to superimpose with an impressive accuracy, i.e., a quadratic error <1%. Test-re-test studies gave the same determination of the specific parameters. In benign prostatic hyperplasia patients, the compressive effect on both prostatic urethra and bladder neck was separately identified. The same intra-individual values were found at 2-week intervals in the group with no treatment (P = no significance), whereas after 3 months of treatment with an alpha-blocker, a decrease in values was noted in responder patients (P < 0.001). In women with various degrees of cystocele, a constrictive effect was identified and found to be identical for successive flows during the same urodynamic testing. This large prospective study demonstrated the relevance of a sophisticated, heavily computerized micturition model, taking into account physiological voiding parameters, to the study of flow in healthy individuals and patients with benign prostatic hyperplasia or cystocele. Curve-fitting led to the determination of critical events during flow such as break point and plateau phase. Determination of these events may enhance uroflow interpretation by providing additional information on the detrusor function. Neurourol. Urodynam. 19:153-176, 2000.

Mathematical model of muscular fatigue. Part III. Classification of muscular fibres versus metabolism of exhaustion.

In order to modelize muscular fatigue, use and depletion of energizing stores are incorporated in the previously elaborated model. The role of muscle glycogen is crucial in sustained muscular contractions. Two patterns of muscular exhaustion are described: one is related to glycogen depletion (S and FR fibres) and the other to an unphysiological drop in ATP concentrations (FF fibres). Thus, the muscle fibre recruitment can be related to its theoretical metabolism of exhaustion. The importance of the muscle lactate level is connected to the glucose entry into the muscle cell and the rigor mortis. Computations have been carried out on a computer DPS 7.

Mathematical model of muscular fatigue. II. Changes of metabolites level and of force during exercise in relation to a fatigability parameter.

In order to study muscular fatigue, a mathematical model allowing the simulation of changes of metabolites level and of force during exercise in human muscle is built. It results from the association of two previous models and from the introduction of two parameters (pH and ATP concentration) influencing directly the muscular force and of the fatigability parameter (A) which characterizes the oxidative capacity of a given fibre. Simulations of physiological conditions of exercise and recovery allow one to bring out a classification of muscular fibres in terms of the fatigability parameter. In addition, the study of successive exercises underlines the lactate level role in force generation. Computations have been carried out on a computer DPS 7.

Human locomotion analysis: determination of muscular forces and nervous orders.

This study gives a modelization of gait which connects the kinematic and mechanical parameters of the motion with the characteristic ones of the muscular contraction (F, l, i, y). The problem, formulated from the equations of the motion related to a standard human being, is solved in terms of a minimization problem, taking into account the anatomical, physiological and energetic constraints of this motion by means of numerical calculations on a computer I.B.M. 360. This first approach allows us to determine the periods of activity of the different muscles, the exerted forces and the associated nervous orders during a stance phase. The model can be applied to the study of the effect of fatigue on motion.

Mathematical model of muscular fatigue. I. Metabolite level changes during exercises of different intensities.

To quantify muscular fatigue we study by a mathematical modelization the changes of the levels of ATP and various metabolites, and of the oxygen uptake with the intensity of a requested muscular exercise. The proposed model is consistent with the main phenomena experimentally observed during exercises; it allows also one to extrapolate these experimental results to any condition and to simulate exercise-complete and/or incomplete recovery cycles. The lactate kinetics allows one particularly to justify the empirical optimization of rest rhythms during exercises of long duration. Equations are solved using a 4th order Runge-Kutta method; computations are performed on an IRIS 80 CII computer.

Construction, mathematical study and numerical simulation of a calcium turnover model during skeletal muscle contraction.

Starting from recent physiological data we establish a first order non-linear differential system which models the calcium turnover during skeletal muscular contraction. We describe the methods allowing one to calculate with a computer the non-experimentally directly-measured initial conditions. In order to ensure the consistency of the system with physiology we prove the positivity, a priori inequalities and both the existence and the uniqueness of the solutions. To obtain a complete knowledge of the system during a twitch, the aim is to identify, using the experimental data the calcium, two re-uptake constants and the function describing its ejection rate. We demonstrate the uniqueness of the identification problem, we establish an original algorithm for the identification of the two constants, and we show that the function to be identified is the solution of an integral equation for the resolution of which we give an algorithm whose convergence is proved. According to this mathematical study the model is numerically simulated on a computer; this allows us thus to find again experimental data in a consistent frame, and to predict the values of some non-measured constants and functions.