Normal Compliance Research Articles

The mechanistic interaction between mechanical dyssynchrony and filling pressure in cardiac resynchronization therapy candidates.

Both left ventricular (LV) mechanical dyssynchrony and filling pressure have been shown to be associated with outcome in heart failure patient treated with cardiac resynchronization therapy (CRT). To investigate the mechanistic link between mechanical dyssynchrony and filling pressure and to assess their combined prognostic value in CRT candidates. Left atrial pressure (LAP) estimation and quantification of mechanical dyssynchrony were retrospectively performed in 219 CRT patients using echocardiography. LAP was elevated (eLAP) in 49% of the population, normal (nLAP) in 40%, and indeterminate (iLAP) in 11%. CRT response was defined as %-decrease in LV end-systolic volume after 12±6 months CRT. Clinical endpoint was all-cause mortality during 4.8 years (interquartile range: 2.7-6.0 years). To investigate the mechanistic link between mechanical dyssynchrony and filling pressure, the CircAdapt computer model was used to simulate cardiac mechanics and hemodynamics in virtual hearts with LBBB and various causes of increased filling pressure. Patients with nLAP had more significant mechanical dyssynchrony than those with eLAP. The combined assessment of both parameters before CRT was significantly associated with reverse LV remodeling and post-CRT survival. Simulations revealed that mechanical dyssynchrony is attenuated by increased LV operational chamber stiffness, regardless of whether it is caused by passive or active factors, explaining the link between mechanical dyssynchrony and filling pressure. Our combined clinical-computational data demonstrate that in patients with LBBB, the presence of mechanical dyssynchrony indicates relatively normal LV compliance and low filling pressure, which may explain their strong association with positive outcomes after CRT.

Accuracy of Real-Time Data Provided by Mechanical Insufflation-Exsufflation Devices.

Mechanical insufflation-exsufflation (MI-E) is crucial to assist patients with impaired cough, especially those with neuromuscular diseases. Despite recent advancements that enable real-time display of peak expiratory flow (PEF) and inspiratory volume, accurately monitoring these parameters with MI-E devices during treatment can still present challenges. A bench study that used a mechanical lung connected to 3 MI-E devices (EOVE-70; E-70 and Comfort Cough II) was conducted to evaluate PEF and inspiratory volume monitoring accuracy. Two clinical conditions were tested, low and normal compliance, with 6 different MI-E settings tested: +20/-20, +30/-30, +40/-40, +40/-50, +40/-60, and +40/-70 cm H2O. PEF (L/min) and inspiratory volume (mL) displayed on the screen were recorded cycle by cycle, while a pneumotachograph connected to the mechanical lung was used to measure the actual PEF and inspiratory volume for data comparison. Flow bias was assessed by calculating the difference (PEF - peak inspiratory flow) and ratio (PEF to peak inspiratory flow) between flows. All devices systematically underestimated PEF, with device A showing the smallest estimation error (-7.4 [-10.1; -6] %). Devices B and C exhibited larger errors (-26.5 [-29.2; -25.6] and (-29.9 [-30.7; -28.7] %, respectively). All the devices underestimated inspiratory volume, with device B showing the smallest estimation error (-15.1 [-21.2; -12.3] %). Device A exhibited a significantly larger error (-26.9 [-30.3; -24.8] %). The error from device C (-17.7 [-34.5; -13.8] %) was not statistically different from device B. Device type, high pressure settings (> +40/-40 cm H2O), and a lung model compliance of 60 mL/cm H2O were the main contributors to error in estimating PEF and inspiratory volume. Finally, we observed differences of PEF-to-peak inspiratory flow ratio and PEF minus peak inspiratory flow differences achieved. Our study highlighted consistent underestimation of PEF and inspiratory volume across MI-E devices. Improving device monitoring is essential for guiding MI-E therapy and ensuring patient safety.

An electro-elastic contact problem with an internal state variable

We consider a mathematical model which describes the quasistatic process of contact between a piezoelectric body and an electrically conductive foundation. General models for elastic materials with piezoelectirec effect, called electro-elastic materials. This paper is devoted to the study of the model involving a frictionless contact between an electro-elastic body characterized by long memory and a conductive adhesive foundation. The process is mechanically quasistatic and electrically static. We model the material with a general nonlinear electro-elastic constitutive law with internal state variable and the contact with normal compliance and unilateral constraint, where the adhesion is taken into account and a regularized electrical conductivity condition. The main feature of these models consists of the fact that their variational formulation is given by a history-dependent quasivariational inequality for the displacement field and a linear variational equation for the electric potential. A weak formulation for the model is given in the form of a coupled system for the displacement, the stress, the electric displacement, the electric potential, the bonding and the variable state internal fields. We derive a variational formulation for the problem and then, under a smallness assumption on the data, we prove the existence of a unique weak solution to the model. We also investigate the behavior of the solution with respect the electric data on the contact surface and prove its unique weak solution. The proof is based on nonlinear evolution equations with monotone operators, differential equations and Banach fixed point arguments.

The relationship between urodynamic bladder compliance and urinary fibrosis markers in children with neurogenic bladder dysfunction

BackgroundDecreased bladder compliance is an important risk factor for upper urinary tract in children with neurogenic bladder dysfunction (NBD). Urodynamics is the gold standard in determining bladder compliance. ObjectiveTo investigate the relationship between low bladder compliance and urinary fibrosis markers in NBD. Study designSpina bifida patients with NBD, who admitted between March 2021 and July 2021 were included. Patients with low compliant bladders, no renal scar, no recurrent urinary tract infections formed low compliance, LC group. Normal compliance, NC group, was comprised of patients with normocompliant bladders and the same characteristics. Control group (Group C) consisted of patients for outpatient surgery and had no known bladder dysfunction. Compliance was calculated with the formula ΔV/ΔP and a value of under 15 ml/cmH2O was accepted as low. Age, gender, urine density, serum urea, creatinine levels and urodynamic parameters were noted. Urinary type 1, type 3 collagen and its precursor procollagen type 3 and serum type 1 and 3 collagen were determined by ELISA. Results72 patients were included (LC group, n:31, NC group, n:24, C group n:17, mean age 7,39±1,24 years). No significant difference was observed in the comparison of age, gender, urine density and serum urea and creatinine values. No significant difference was observed between the LC and NC groups for urodynamic parameters, except for bladder compliance. Urinary collagen type 1 in LC group (11,71±3,02 ng/ml) was found to be significantly higher than that of the C group (9,45±1,97 ng/ml) (p=0,03). Urinary procollagen type 3 was significantly higher in LC group (103,15±24 ng/ml) when compared to C group (82,42±22,26 ng/ml) (p=0,016). Urinary collagen type 1 level above 9,20 ng/ml was 80,6% sensitive and 70,6% specific and urinary procollagen type 3 level above 78 ng/ml was 87% sensitive and 70,6% specific in predicting low compliance. DiscussionThis study seems to be the first study in the literature to evaluate bladder fibrosis and compliance, biochemically, by measuring urinary collagen levels in NBD. Urinary fibrosis markers are not currently an alternative to urodynamics for bladder compliance, but they may have potential to reduce the need for urodynamics with this indication. ConclusionDetermination of urinary collagen levels may be a marker of bladder wall fibrosis and may indirectly show decreased bladder compliance. It is plausible to say that invasive methods such as urodynamics may be less preferred for defining bladder compliance, instead, urinary biomarkers may have merit for this purpose in the future.

Botulinum Neurotoxin Type A in paediatric non-neurogenic therapy resistant overactive bladder: a cohort study.

Intradetrusor Botulinum Neurotoxin Type A (BoNT-A) is an increasingly applied treatment modality for overactive bladder (OAB) in children with refractory urinary incontinence. Despite that, evidence is sparse, and the potential not fully understood. The aim of this study was to evaluate the effectiveness and safety of intradetrusor injection in children with refractory functional OAB and urinary incontinence. Furthermore, we aimed to identify predictors of efficacy and side effects to BoNT-A treatment. We conducted a cohort study of children with OAB and urinary incontinence who received intradetrusor injection of BoNT-A in the period 01.01.2016 to 31.12.2020 at our centre. All patients were refractory to standard urotherapy, anticholinergics, mirabegron and the combination of these treatments. Patients with neurogenic bladder were excluded. Primary endpoint was the reduction on the frequency of urinary incontinence episodes from baseline. Secondary endpoints included urodynamic parameters and uroflowmetry characteristics as well as side effects. Forty-three children (mean age at first treatment 10.7 ± 1.8, 30 males) were included. After first treatment, a reduction of ≥ 50% in incontinence episodes was seen in 58% of patients with daytime urinary incontinence (DUI) and 47% of patients with nocturnal enuresis (NE). Adverse events, mainly urinary tract infections (UTI), were reported by 16% of patients after first treatment. Our analysis identified normal cystometric compliance as a significant predictor of treatment effect We estimated the mean duration of effect to be approximately 7months. Intradetrusor BoNT-A injection appears to be a safe and effective option in treating refractory urinary incontinent children with overactive bladder. We identified cystometric compliance as a predictor of response. Most children necessitate repeated treatments. Further prospective and controlled studies are necessary in order to fully identify predictors and potential of treatment.

A mixed variational approach for modeling frictional contact problems with normal compliance in electro-elasticity

A mixed variational approach for modeling frictional contact problems with normal compliance in electro-elasticity

P165 HEMODYNAMIC PROFILES OF ISOLATED DIASTOLIC HYPERTENSION IN AMBULATORY BLOOD PRESSURE MONITORING

Background and Objective: Isolated diastolic hypertension (IDH) is a prevalent form of high blood pressure (BP), especially among young individuals. Yet, its association with cardiovascular disease risk and the necessity of treatment remain subjects of ongoing debate. Our research endeavors to elucidate hemodynamic profiles using a non-invasive method applied to 24-hour ambulatory blood pressure monitoring (24-h ABPM). However, uncertainty persists regarding whether distinct hemodynamic profiles exist within IDH patients, considering they are characterized by normal total arterial compliance (Ct). This study aims to shed light on potential variations in hemodynamics within the IDH population, providing valuable insights for personalized treatment. Methods: A cross-sectional study was conducted, involving 7,202 patients referred to an outpatient cardiology center for suspected arterial hypertension. These patients underwent 24-h ABPM. The study included individuals over 18 years old without a prior diagnosis of hypertension and not taking antihypertensive medication. Two groups were included: those with IDH, defined as diastolic blood pressure >80 mmHg (24-h ABPM), and those with normotension. Hemodynamic parameters were estimated using a published method to estimate Ct. Silhouette analysis determined the number of underlying groups within the IDH cohort, while cluster analysis classified these subgroups. Results: Among the participants, 59.0% were female, with an average age of 49.0±14.0 years. Of the total patients included, 3,424 (47.5%) had isolated diastolic hypertension (IDH). Silhouette analysis effectively distinguished two groups. Group IDH-1 exhibited normal Ct and systemic vascular resistance (SVR), elevated heart rate (HR), and higher cardiac index (CI) (P value <0.001). Conversely, group IDH-2 demonstrated high Ct and SVR, lower HR, and CI (P value <0.001) (Table). Conclusions: The delineation of two distinct hemodynamic profiles within IDH is significant. The first group demonstrates a cardiogenic hypertension profile, indicated by elevated CI, whereas the second group presents a profile characterized by heightened SVR. These contrasting hemodynamic patterns offer valuable insights for tailoring treatment strategies to individual patient needs. Table. Comparison of hemodynamic variables between normotensives (NT) and two isolated diastolic hypertension (IDH) profile, utilizing ANOVA for statistical analysis.

Virtual element method for solving a viscoelastic contact problem with long memory

In this paper, we use the virtual element method to solve a history-dependent hemivariational inequality arising in contact problems. The contact problem concerns the deformation of a viscoelastic body with long memory, subjected to a contact condition with non-monotone normal compliance and unilateral constraints. A fully discrete scheme based on the trapezoidal rule for the discretization of the time integration and the virtual element method for the spatial discretization are analyzed. We provide a unified priori error analysis for both internal and external approximations. For the linear virtual element method, we obtain the optimal order error estimate. Finally, three numerical examples are reported, providing numerical evidence of the theoretically predicted optimal convergence orders.

Analysis of a dynamic contact problem with long memory

We examine a mathematical framework detailing a dynamic frictional contact involving thermo-viscoelastic materials characterized by long memory and damage. The contact is modeled by the normal compliance condition with Coulomb's friction law, while surface wear is also factored in. The model was in the form of a coupled system which includes an evolution equation written in inclusion form for the frictional contact, parabolic variational inequality for the damage field, nonlinear differential equation for the temperature field and an equation for the wear particles and an evolution. A variational formulation for the model was derived and the existence of the unique weak solution established, under smallness assumptions on a part of the problem data. The proof used various results from the theory of evolution inequalities and repeated fixed-point arguments.

THE DIFFICULTY OF USING IRREGULAR SENTENCE BY IRAQI EFL STUDENTS AT UNIVERSITY OF BABYLON

The objective of the study is to investigate the difficulty of using irregular verbs in the students writing an essay at the University of Babylon. The design of this study is descriptive qualitative research. The sample of the study comprised 25 students in their fourth year, and it was selected randomly. The findings of the study showed that 70% of the students were unable to use irregular cases such as verbs and adjectives incorrectly. Also, the findings show that the students use both regular and irregular verb (past) in their students' writing essays. The most dominant verb past written by the students in their students’ writing essay is an irregular verb. Regular verbs are verbs that can change according to tense and change it regularly. Regular verbs are verbs whose changes comply with normal rules, that is with add the letter -d or -ed to the verb first-form/verb-1 (infinitive) so that it becomes a verb form second/verb-2 (past tense). Several things must be considered in the way of forming regular verbs by adding the letter -ed suffix or -d in the basic verb/verb-1 (infinitive). Irregular verbs are verbs that change according to the tense and do not comply with normal compliance. The past tense Irregular verbs are not formed from basic verbs/verb-1 (infinitives) plus letters -d or -ed letters to form verb-2/past tense. Irregular verbs form their past tense differently (through) not always) through a vowel and consonant change. This study recommends students should be well-trained on how to use irregular verbs in the past tense case or changing the form of the regular adjective, and also must be memorized by the learners/students because of the difficulty to distinguish the irregular verbs among the sentences.

A doubly history‐dependent quasivariational inequality arising in viscoelastic frictional contact problems with wear

AbstractWe aim here to investigate a new mathematical model that describes the contact between a viscoelastic body, accounting for long memory and wear effects, and an obstacle referred to as the foundation. The contact model is governed by a normal compliance condition, coupled with Coulomb's law of dry friction for sliding, and wear effects. We derive the variational formulation of the model, which involves coupling of a quasi‐variational inequality with a nonlinear equation. By pursuing the abstract history‐dependent quasi‐variational inequalities and leveraging the fixed point theorem, we establish results concerning both existence and uniqueness.

Analysis and numerical simulation of frictionless contact problem with normal compliance in thermo-viscoelasticity

Analysis and numerical simulation of frictionless contact problem with normal compliance in thermo-viscoelasticity

Optimizing Control for a Piezo-Viscoelastic Contact Challenge Involving Normal Compliance and Coulomb’s Friction

Optimizing Control for a Piezo-Viscoelastic Contact Challenge Involving Normal Compliance and Coulomb’s Friction

On the dynamic Coulomb's frictional contact problem for thermo‐piezoelectric materials

AbstractIn this work, we study, from a variational point of view, a dynamic contact problem between a thermo‐piezoelectric body and a thermally conductive foundation. The normal compliance contact condition and Coulomb's friction law are employed to model the contact. We provide existence and uniqueness results of a weak solution to the model using adequate auxiliary problems, an abstract result on nonlinear first‐order evolution inequalities and Banach fixed point argument. Finally, the continuous dependence of the solution on the surface traction force and the surface electrical charge is studied.

Evaluation of vascular aging on measures of cardiac function and mechanical efficiency: insights from in-silico modeling.

This study evaluated the hypothesis that vascular aging (VA) reduces ventricular contractile function and mechanical efficiency (ME) using the left ventricular pressure-volume (PV) construct. A previously published in-silico computational model (CM) was modified to evaluate the hypothesis in two phases. In phase I, the CM included five settings of aortic compliance (CA) from normal to stiff, studied at a heart rate of 80 bpm, and phase II included the normal to stiff CA settings evaluated at 60, 100, and 140 bpm. The PV construct provided steady-state and transient data through a simulated vena caval occlusion (VCO). The steady-state data included left ventricular volumes (EDV and ESV), stroke work (SW), and VCO provided the PV area (PVA) data in addition to the three measures of contractile state (CS): end-systolic pressure-volume relationship (ESPVR), dP/dtmax-EDV and preload recruitable stroke work (PRSW). Finally, ME was calculated with the SW/PVA parameter. In phase I, EDV and ESV increased, as did SW and PVA. The impact on the CS parameters demonstrated a small decrease in ESPVR, no change in dP/dtmax-EDV, and a large increase in PRSW. ME decreased from 71.5 to 60.8%, respectively. In phase II, at the normal and stiff CA settings, across the heart rates studied, EDV and ESV decreased, ESPVR and dP/dtmax-EDV increased and PRSW decreased. ME decreased from 76.4 to 62.6% at the normal CA and 65.8 to 53.2% at the stiff CA. The CM generated new insights regarding how the VA process impacts the contractile state of the myocardium and ME.

On the dynamic frictionless contact problem with normal compliance in thermo-piezoelectricity

In this work, we study, from a variational and numerical point of view, a dynamic contact problem between a thermo-electro-viscoelastic body and an electrically and thermally conductive foundation. The normal compliance condition and a nonlinear regularized electrical and thermal conditions are employed to model the contact. We provide existence and uniqueness results of a weak solution to the model using adequate auxiliary problems, Gronwall’s lemma, and Banach fixed point theorem. Finally, we introduce a fully discrete approximation using the finite element method and an Euler scheme. Then we derive some error estimates, leading to the linear convergence result under suitable additional regularity conditions.

Damped Normal Compliance (DNC) and the restitution coefficient

This work introduces and studies a novel normal compliance contact condition with damping, the Damped Normal Compliance (DNC), which is more realistic than the usual normal compliance condition that is often used in modeling contact between solids. The condition is applied in a model for the contact of a rigid mass with a reactive obstacle and allows for energy dissipation during contact. We analyze the model and show that the condition is of mathematical, as well as applied, interest. Then, we establish its relationship with the so-called “coefficient of restitution,” e , and show that the concept is not well defined, since e depends on the system parameters, applied force, and initial data. The various theoretical results are depicted using computer simulations.

Well-posedness of evolutionary differential variational–hemivariational inequalities and applications to frictional contact mechanics

In this paper, we study the well-posedness of a class of evolutionary variational–hemivariational inequalities coupled with a nonlinear ordinary differential equation in Banach spaces. The proof is based on an iterative approximation scheme showing that the problem has a unique mild solution. In addition, we established the continuity of the flow map with respect to the initial data. Under the general framework, we consider two new applications for modeling of frictional contact for viscoelastic materials. In the first application, we consider Coulomb’s friction with normal compliance, and in the second, normal damped response. The structure of the friction coefficient μ is new with motivation from geophysical applications in earth sciences with dependence on an external state variable α and the slip rate | u · τ | .

Quasistatic Evolution of Damage in Thermo-electro-elastic-viscoplastic Materials With Normal Compliance

We have studied contact problem in a quasistatic process with boundary conditions, for which we couple a thermal effect and damage and electrical effect. We assume that the contact is with normal compliance in a form with a gap function and is associated to a slip rate-dependent version of Coulomb’s law of dry friction. We give the variational formulation, then the existence and the uniqueness of the weak solution. The proof is based on arguments of time-dependent variational inequalities, parabolic inequalities, and fixed points.

An improved normal compliance method for non-smooth contact dynamics

An improved normal compliance method for non-smooth contact dynamics