Effect of a guide for clinical reasoning on Nursing students' diagnostic accuracy: A clinical trial. / Efeito de guia para raciocínio clínico na acurácia diagnóstica de estudantes de enfermagem: ensaio clínico.

OBJECTIVE: to evaluate the effect of the Self-Instructional Guide for Clinical Reasoning on the diagnostic accuracy of undergraduate Nursing students. METHOD: a randomized, parallel and double-blind (researchers and outcome evaluators) clinical trial, carried out with undergraduate Nursing students. Validated case studies were applied in two phases to identify the patient's Nursing diagnosis/problem, etiology and clues, using the Guide with the intervention group in the second phase. The outcomes - diagnostic and etiological accuracy and number of clues - were evaluated using validated rubrics. Descriptive statistics were used to analyze demographic data; Fisher's exact test for similarities in prior education and confidence; Mann-Whitney's test for age; and non-parametric ANOVA test in the evaluation of the hypothesis of differences in performance. RESULTS: final sample composed of 24 students in the control group and 27 in the intervention group; no difference as to gender, age and schooling. There was a difference in diagnostic (p=0.041) and etiological (p=0.0351) accuracy in the intervention group, showing a negative effect of using the Guide. CONCLUSION: the one-time self-instruction was not effective in impacting the diagnostic accuracy of students solving case studies. Repeated application of the Guide as a teaching tool can be effective in improving such outcome. REBEC: RBR-4bhr78.

Efeito de guia para raciocínio clínico na acurácia diagnóstica de estudantes de enfermagem: ensaio clínico / Effect of a guide for clinical reasoning on Nursing students' diagnostic accuracy: A clinical trial / Efecto de una guía de razonamiento clínico sobre la precisión diagnóstica de estudiantes de enfermería: ensayo clínico

Resumo Objetivo avaliar o efeito do Guia Autoinstrucional para Raciocínio Clínico na acurácia diagnóstica de estudantes de Bacharelado em Enfermagem. Método ensaio clínico randomizado, paralelo, duplo cego (pesquisadores e avaliadores dos desfechos), realizado com graduandos de Enfermagem. Aplicaram-se, em duas fases, estudos de caso validados para a identificação de diagnóstico de enfermagem/problema do paciente, etiologia e pistas, sendo utilizado o Guia com o grupo intervenção na segunda fase. Os desfechos - acurácia diagnóstica, etiológica e número de pistas - foram avaliados por meio de rubricas validadas. Para análise, utilizou-se estatística descritiva para dados demográficos; teste exato de Fisher para similaridades na educação prévia e confiança; teste de Mann-Whitney para idade; teste ANOVA não paramétrico na avaliação da hipótese de diferenças no desempenho. Resultados amostra final composta por 24 estudantes no grupo controle e 27 no intervenção; sem diferença quanto ao sexo, idade e educação. Houve diferença para acurácia diagnóstica (p=0,041) e etiológica (p=0,0351) no grupo intervenção, mostrando efeito negativo da utilização do Guia. Conclusão a autoinstrução implementada uma única vez não foi efetiva em impactar a acurácia diagnóstica de estudantes solucionando estudos de caso. A aplicação repetida do Guia como ferramenta didática pode ser efetiva para melhorar tal desfecho. REBEC: RBR-4bhr78.

Abstract Objective to evaluate the effect of the Self-Instructional Guide for Clinical Reasoning on the diagnostic accuracy of undergraduate Nursing students. Method a randomized, parallel and double-blind (researchers and outcome evaluators) clinical trial, carried out with undergraduate Nursing students. Validated case studies were applied in two phases to identify the patient's Nursing diagnosis/problem, etiology and clues, using the Guide with the intervention group in the second phase. The outcomes - diagnostic and etiological accuracy and number of clues - were evaluated using validated rubrics. Descriptive statistics were used to analyze demographic data; Fisher's exact test for similarities in prior education and confidence; Mann-Whitney's test for age; and non-parametric ANOVA test in the evaluation of the hypothesis of differences in performance. Results final sample composed of 24 students in the control group and 27 in the intervention group; no difference as to gender, age and schooling. There was a difference in diagnostic (p=0.041) and etiological (p=0.0351) accuracy in the intervention group, showing a negative effect of using the Guide. Conclusion the one-time self-instruction was not effective in impacting the diagnostic accuracy of students solving case studies. Repeated application of the Guide as a teaching tool can be effective in improving such outcome. REBEC: RBR-4bhr78.

Resumen Objetivo evaluar el efecto de la Guía Autoinstruccional de Razonamiento Clínico en la precisión diagnóstica de estudiantes de Licenciatura en Enfermería. Método ensayo clínico aleatorizado, paralelo, doble ciego (investigadores y evaluadores de resultados), realizado con estudiantes de la carrera de enfermería. Se aplicaron estudios de casos validados en dos fases para identificar el diagnóstico de enfermería/problema del paciente, etiología y pistas, utilizando la Guía con el grupo experimental en la segunda fase. Los resultados (precisión diagnóstica, etiológica y número de pistas) se evaluaron utilizando rúbricas validadas. Para el análisis se utilizó estadística descriptiva para datos demográficos; prueba exacta de Fisher para similitudes en educación previa y confianza; prueba de Mann-Whitney para la edad; prueba ANOVA no paramétrica en la evaluación de la hipótesis de diferencias en el desempeño. Resultados muestra final compuesta por 24 estudiantes en el grupo control y 27 en el grupo experimental; no había diferencias en cuanto al sexo, la edad y educación. Hubo diferencia en la precisión diagnóstica (p=0,041) y etiológica (p=0,0351) en el grupo experimental, que mostraron un efecto negativo del uso de la Guía. Conclusión la autoinstrucción implementada por única vez no fue efectiva para generar un impacto en la precisión diagnóstica de los estudiantes que resolvieron los estudios de casos. La aplicación repetida de la Guía como herramienta de enseñanza puede ser eficaz para mejorar dicho resultado. REBEC: RBR-4bhr78.

Effects of Clinical Reasoning Prompts on Nursing Students' Clinical Judgment for a Patient Experiencing Respiratory Distress.

PURPOSE: To test the effects of clinical reasoning prompts on students' clinical judgment of a written case study. METHODS: An experimental pre- and posttest study with second semester nursing students (N = 163). FINDINGS: The intervention was insufficient to significantly improve clinical judgment. Students identified that the prompts would help them "narrow… down the problem" and "slow… the decision-making process" to improve analysis. The most accurate patient problem was identified by 28% of students in pretest and 35% in posttest. CONCLUSIONS: This study provides evidence of variations in nursing students' clinical judgment and students' desire to use decision-making algorithms. NURSING IMPLICATIONS: Nurse educators should provide students with additional education and practice to identify and solve these types of problems.

Arteriovenous fistula maturation and the influence of fluid dynamics.

Arteriovenous fistula creation is the preferred vascular access for haemodialysis therapy, but has a large failure rate in the maturation period. This period generally lasts 6 to 8 weeks after surgical creation, in which the vein and artery undergo extensive vascular remodelling. In this review, we outline proposed mechanisms for both arteriovenous fistula maturation and arteriovenous fistula failure. Clinical, animal and computational studies have not yet shown a definitive link between any metric and disease development, although a number of theories based on wall shear stress metrics have been suggested. Recent work allowing patient-based longitudinal studies may hold the key to understanding arteriovenous fistula maturation processes.

Tracking geometric and hemodynamic alterations of an arteriovenous fistula through patient-specific modelling.

BACKGROUND AND OBJECTIVE: The use of patient-specific CFD modelling for arteriovenous fistulae (AVF) has shown great clinical potential for improving surveillance, yet the use of imaging modes such as MRI and CT for the 3D geometry acquisition presents high costs and exposure risks, preventing regular use. We have developed an ultrasound based procedure to bypass these limitations. METHODS: A scanning procedure and processing pipeline was developed specifically for CFD modelling of AVFs, using a freehand ultrasound setup combining B-mode scanning with 3D probe motion tracking. The scanning procedure involves sweeping along the vasculature to create a high density stack of B-mode frames containing the lumen geometry. This stack is converted into a continuous volume and transient flow waveforms are recorded at the boundaries, synchronised with ECG and automatically digitised, forming realistic boundary conditions for the CFD models. This is demonstrated on a diseased patient-specific AVF. RESULTS: The three scans obtained using this procedure varied in geometry and flow behaviour, with regions of disease located in the first two scans. The outcome of the second procedure seen in the third scan indicated successful restoration with no sites of disease and higher flow. The models gave insight into the lumenal changes in diameter for both the artery and vein segments, as well as characterising hemodynamic behaviours in both the diseased and restored states. Vascular segment resistances obtained from the CFD models indicate a significant reduction once disease was removed, resulting in much higher flows enabling the patient to resume dialysis. CONCLUSION: The methodology described in this study allowed for a multifaceted analysis and high level tracking in terms of both geometry and flow behaviours for a patient case, demonstrating significant clinical utility and practicality, as well as enabling further research into vascular disease progression in AVFs through longitudinal analysis.

Clinical utility of pressure feedback to socket design and fabrication.

BACKGROUND: The clinical utility of measuring pressure at the prosthetic socket-residual limb interface is currently unknown. OBJECTIVES: This study aimed to identify whether measuring interface pressure during prosthetic design and fabrication results in closer agreement in pressure measurements between sockets made by different clinicians, and a reduction in pressure over areas of concern. It also investigated whether clinicians value knowing the interface pressure during the fabrication process. STUDY DESIGN: Mixed methods. METHODS: Three prosthetists designed a complete prosthetic system for a transtibial residual limb surrogate. Standardised mechanical testing was performed on each prosthetic system to gain pressure measurements at four key anatomical locations. These measurements were provided to the clinicians, who subsequently modified their sockets as each saw fit. The pressure at each location was re-measured. Each prosthetist completed a survey that evaluated the usefulness of knowing interface pressures during the fabrication process. RESULTS: Feedback and subsequent socket modifications saw a reduction in the pressure measurements at three of the four anatomical locations. Furthermore, the pressure measurements between prosthetists converged. All three prosthetists found value in the pressure measurement system and felt they would use it clinically. CONCLUSIONS: Results suggest that sensors measuring pressure at the socket-limb interface has clinical utility in the context of informing prosthetic socket design and fabrication. If the technology is used at the check socket stage, iterative designs with repeated measurements can result in increased consistency between clinicians for the same residual limb, and reductions in the magnitudes of pressures over specific anatomical landmarks. CLINICAL RELEVANCE: This study provides new information on the value of pressure feedback to the prosthetic socket design process. It shows that with feedback, socket modifications can result in reduced limb pressures, and more consistent pressure distributions between prosthetists. It also justifies the use of pressure feedback in informing clinical decisions.

Reduction in anastomotic flow disturbance within a modified end-to-side arteriovenous fistula configuration: Results of a computational flow dynamic model.

AIM: We sought to determine if a modification to the peri-anastomotic vein configuration during end-to-side arteriovenous fistula (AVF) creation would achieve a favourable haemodynamic environment compared with the standard acute-angle AVF. METHODS: Computational fluid dynamics (CFD) modelling of two end-to-side AVF geometries (smooth-vein-loop vs. acute-angle) allowed for haemodynamic modelling. Haemodynamic fields at various stages of the pulse cycle were observed and compared across both models. RESULTS: We found a significant reduction in flow disturbance in the modified shape at the peri-anastomotic vein region, a common site for stenosis. The acute anastomotic angle characteristic of a standard-end-to-side AVF was found to cause significant flow disturbance throughout the pulse cycle. CONCLUSION: Computational modelling indicates that improvements in the haemodynamic environment of an AVF are achievable when a gentle change in direction is present in the vein segment. This may lead to improved maturation and AVF patency through reduction in disturbed flow patterns.

A Methodology for Non-Invasive 3-D Surveillance of Arteriovenous Fistulae Using Freehand Ultrasound.

OBJECTIVE: Surveillance techniques for arteriovenous fistulae are required to maintain functional vascular access, with two-dimensional duplex ultrasound the most widely used imaging modality. This paper presents a surveillance method for an arteriovenous fistula using a freehand three-dimensional (3-D) ultrasound system. A patient-case study highlights the applicability in a clinical environment. METHODS: The freehand ultrasound system uses optical tracking to determine the vascular probe location, and as the probe is swept down a patient's arm, each B-mode slice is spatially arranged to be post-processed as a volume. The volume is segmented to obtain the 3-D vasculature for high detail analysis. RESULTS: The results follow a patient with stenosis, undergoing surgery to have a stent placement. A surveillance scan was taken pre-surgery, postsurgery, and at a two-month follow-up. Vasculature changes are quantified using detailed analysis, and the benefits of using 3-D imaging are shown through 3-D printing and visualization. CONCLUSION AND SIGNIFICANCE: Non-invasive 3-D surveillance of arteriovenous fistulae is possible, and a patient-specific geometry was created using ultrasound and optical tracking. Access to this non-invasive 3-D surveillance technique will enable future studies to determine patient-specific remodeling behavior, in terms of geometry and hemodynamics over time.

Computational Fluid Dynamic Analysis of the Hemodialysis Plastic Cannula.

The jet of fluid returning to the patient through a hemodialysis venous needle has previously been reported as a potential source of endothelial damage which can lead to intimal hyperplasia (IH) in arteriovenous fistulae (AVF). Metal needles are the current standard practice for accessing the vascular system in hemodialysis. However, plastic cannulae have been used in Japan for 30 years. This study utilized computational fluid dynamics to analyze the hemodynamics of blood exiting a plastic cannula and determined the optimal placement and blood flow rate. Transient simulations were run using a 15G Argyle Safety Fistula Cannula with Anti-Reflux Valve inserted into an idealized cephalic vein. The cannula tip was fixed at three different locations within the vein (upper third, middle, and lower third) with blood flow rates of 200 mL/min, 300 mL/min, and 400 mL/min imposed. The high degree of jet break down immediately after exiting the cannula was attributed to the staggered side hole arrangement, position of the cannula in the vein, and the imposed blood flow rate. Elevated levels of wall shear stress which may lead to IH were identified at the site of jet impingement on the vein floor as well as regions of high residency time. The risk of IH may be minimized by enhancing the breakdown of the jet through the use of optimal blood flow rates between 300 and 400 mL/min and ensuring the cannula tip is placed away from the walls of the vein.

Analysis of Blood Flow Characteristics in a Model of a Mature Side-to-Side Arteriovenous Fistula.

The creation of an arteriovenous fistula (AVF) is a common surgical procedure in hemodialysis patients suffering from end-stage renal disease (ESRD). However, several complications may occur after surgery, including thrombosis, stenosis, and aneurysm. These complications are attributed to hemodynamics perturbations including pathophysiological wall shear stress (WSS) and flow recirculation zones. In this study, we present a computational hemodynamic analysis in a model of a mature side-to-side AVF, which is then validated by experimental measurements. Both computational and experimental results confirmed the presence of complex flow patterns within the AVF with vortices initially developing at the center of the venous region and gradually moving downstream, such that at four characteristic anastomosis lengths downstream, the flow disturbances became minimum. A complex pattern was also observed in WSS distribution with regions of low and high WSS identified in proximal vein and feeding artery, respectively. In addition, the temporal distribution of WSS varied significantly along the venous wall where a large portion of it remained above normal levels of WSS during systole while the area was largely normal during diastole. Our findings support the hypothesis that high WSS is not detrimental to immediate patency of AVF; however, other factors including low WSS and temporal and spatial gradients of WSS increase the risk of vascular access complications.

Mechanical characterization and comparison of energy storage and return prostheses.

The suitability of finite element analysis (FEA) for standardizing the mechanical characterization of energy storage and return (ESAR) prostheses was investigated. A methodology consisting of both experimental and numerical analysis was proposed and trialed for the Vari-flex® ModularTM, Flex-foot Cheetah and Cheetah Xtreme by Össur® and a 1E90 Sprinter by Ottobock®. Gait analysis was conducted to determine suitable orientation angles for non-destructive testing (NDT) of the ESAR prostheses followed by a quasi-static inverse FEA procedure within COMSOL Multiphysics®, where the NDT conditions were replicated to determine the homogenized material properties of the prostheses. The prostheses' loading response under bodyweight for an 80kg person was then simulated, using both Eigenfrequency and time-dependent analysis. The apparent stiffness under bodyweight was determined to be 94.7, 48.6, 57.4 and 65.0Nmm-1 for the Vari-flex® ModularTM, Flex-foot Cheetah, Cheetah Xtreme and 1E90 Sprinter, respectively. Both the energy stored and returned by the prostheses varied negatively with stiffness, yet the overall efficiency of the prostheses were similar, at 52.7, 52.0, 51.7 and 52.4% for the abovementioned prostheses. The proposed methodology allows the standardized assessment and comparison of ESAR prostheses without the confounding influences of subject-specific gait characteristics.

Computational Model of the Arterial and Venous Needle During Hemodialysis.

Arteriovenous fistulae (AVF) are the favored choice of vascular access but still have poor long-term success. Hemodynamic parameters play an important role in vascular health and have been linked to the development of intimal hyperplasia (IH), a pathological growth of the blood vessel initiated by injury. This study aimed to investigate the hemodynamics surrounding the arterial needle (AN) and venous needle (VN), using computational fluid dynamics. A range of blood flow rates, needle positions, and needle orientations were examined. Disturbed flows were found around AN tip in both antegrade and retrograde orientations, which result in regions of high residency time on the surface of the vein and may disrupt endothelial function. Conversely, a high speed jet exits the VN, which produced high wall shear stresses (WSSs) at the point of impingement which can damage the endothelium. The secondary flows produced by jet dissipation also resulted in regions of high residency time, which may influence endothelial structure, leading to IH. The use of shallow needle angles, a blood flow rate of approximately 300 ml/min, and placement of the needle tip away from the walls of the vein mitigates this risk.

Facial deformations during nasal continuous positive airway pressure therapy.

Obstructive Sleep Apnoea (OSA), characterised by repeated collapse of the pharyngeal airway during sleep, causes cessation of breathing followed by arousal, restoring normality. Continuous Positive Airway Pressure (CPAP) is a non-invasive, effective treatment for OSA where positive pressure is applied to the airway through a mask, maintaining patency. Nasal masks are commonly used, contacting the face across the upper lip, sides of the nose and the nasal bridge. Despite health benefits, therapy compliance is sub-optimal, often due to poor mask fit and discomfort. Masks have been designed to conform to the facial profile, but have not taken into account facial deformations. The nature of facial deformations while undergoing CPAP therapy is unknown. This study investigates the facial deformations experienced by a patient while undergoing nasal CPAP therapy. Magnetic Resonance Imaging (MRI) scans of the face were acquired of participants in the reference configuration and while undergoing CPAP therapy. The CPAP scan volume was registered onto the reference volume prior to surface generation for each state. Perpendicular deformation was measured from the reference facial profile to the deformed profile. Large facial deformations were measured at the sides of the nose (4.6±1.6mm) and the upper lip (4.9±1.8mm) with much smaller deformations at the nasal bridge (2.4±0.2mm). When normalised by applied load and tissue thickness, no difference was found. These findings and techniques can be used to consider facial deformation in the development of future nasal CPAP masks to improve comfort and compliance to therapy.

A prosthesis-specific multi-link segment model of lower-limb amputee sprinting.

Lower-limb amputees commonly utilize non-articulating energy storage and return (ESAR) prostheses for high impact activities such as sprinting. Despite these prostheses lacking an articulating ankle joint, amputee gait analysis conventionally features a two-link segment model of the prosthetic foot. This paper investigated the effects of the selected link segment model׳s marker-set and geometry on a unilateral amputee sprinter׳s calculated lower-limb kinematics, kinetics and energetics. A total of five lower-limb models of the Ottobock® 1E90 Sprinter were developed, including two conventional shank-foot models that each used a different version of the Plug-in-Gait (PiG) marker-set to test the effect of prosthesis ankle marker location. Two Hybrid prosthesis-specific models were then developed, also using the PiG marker-sets, with the anatomical shank and foot replaced by prosthesis-specific geometry separated into two segments. Finally, a Multi-link segment (MLS) model was developed, consisting of six segments for the prosthesis as defined by a custom marker-set. All full-body musculoskeletal models were tested using four trials of experimental marker trajectories within OpenSim 3.2 (Stanford, California, USA) to find the affected and unaffected hip, knee and ankle kinematics, kinetics and energetics. The geometry of the selected lower-limb prosthesis model was found to significantly affect all variables on the affected leg (p < 0.05), and the marker-set also significantly affected all variables on the affected leg, and none of the unaffected leg variables. The results indicate that the omission of prosthesis-specific spatial, inertial and elastic properties from full-body models significantly affects the calculated amputee gait characteristics, and we therefore recommend the implementation of a MLS model.

Quantifying prosthetic gait deviation using simple outcome measures.

AIM: To develop a subset of simple outcome measures to quantify prosthetic gait deviation without needing three-dimensional gait analysis (3DGA). METHODS: Eight unilateral, transfemoral amputees and 12 unilateral, transtibial amputees were recruited. Twenty-eight able-bodied controls were recruited. All participants underwent 3DGA, the timed-up-and-go test and the six-minute walk test (6MWT). The lower-limb amputees also completed the Prosthesis Evaluation Questionnaire. Results from 3DGA were summarised using the gait deviation index (GDI), which was subsequently regressed, using stepwise regression, against the other measures. RESULTS: Step-length (SL), self-selected walking speed (SSWS) and the distance walked during the 6MWT (6MWD) were significantly correlated with GDI. The 6MWD was the strongest, single predictor of the GDI, followed by SL and SSWS. The predictive ability of the regression equations were improved following inclusion of self-report data related to mobility and prosthetic utility. CONCLUSION: This study offers a practicable alternative to quantifying kinematic deviation without the need to conduct complete 3DGA.

Evaluation of Different Meshing Techniques for the Case of a Stented Artery.

The formation and progression of in-stent restenosis (ISR) in bifurcated vessels may vary depending on the technique used for stenting. This study evaluates the effect of a variety of mesh styles on the accuracy and reliability of computational fluid dynamics (CFD) models in predicting these regions, using an idealized stented nonbifurcated model. The wall shear stress (WSS) and the near-stent recirculating vortices are used as determinants. The meshes comprise unstructured tetrahedral and polyhedral elements. The effects of local refinement, as well as higher-order elements such as prismatic inflation layers and internal hexahedral core, have also been examined. The uncertainty associated with individual mesh style was assessed through verification of calculations using the grid convergence index (GCI) method. The results obtained show that the only condition which allows the reliable comparison of uncertainty estimation between different meshing styles is that the monotonic convergence of grid solutions is in the asymptotic range. Comparisons show the superiority of a flow-adaptive polyhedral mesh over the commonly used adaptive and nonadaptive tetrahedral meshes in terms of resolving the near-stent flow features, GCI value, and prediction of WSS. More accurate estimation of hemodynamic factors was obtained using higher-order elements, such as hexahedral or prismatic grids. Incorporating these higher-order elements, however, was shown to introduce some degrees of numerical diffusion at the transitional area between the two meshes, not necessarily translating into high GCI value. Our data also confirmed the key role of local refinement in improving the performance and accuracy of nonadaptive mesh in predicting flow parameters in models of stented artery. The results of this study can provide a guideline for modeling biofluid domain in complex bifurcated arteries stented in regards to various stenting techniques.

Spiral blood flow in aorta-renal bifurcation models.

The presence of a spiral arterial blood flow pattern in humans has been widely accepted. It is believed that this spiral component of the blood flow alters arterial haemodynamics in both positive and negative ways. The purpose of this study was to determine the effect of spiral flow on haemodynamic changes in aorta-renal bifurcations. In this regard, a computational fluid dynamics analysis of pulsatile blood flow was performed in two idealised models of aorta-renal bifurcations with and without flow diverter. The results show that the spirality effect causes a substantial variation in blood velocity distribution, while causing only slight changes in fluid shear stress patterns. The dominant observed effect of spiral flow is on turbulent kinetic energy and flow recirculation zones. As spiral flow intensity increases, the rate of turbulent kinetic energy production decreases, reducing the region of potential damage to red blood cells and endothelial cells. Furthermore, the recirculation zones which form on the cranial sides of the aorta and renal artery shrink in size in the presence of spirality effect; this may lower the rate of atherosclerosis development and progression in the aorta-renal bifurcation. These results indicate that the spiral nature of blood flow has atheroprotective effects in renal arteries and should be taken into consideration in analyses of the aorta and renal arteries.

Haemodynamic analysis of femoral artery bifurcation models under different physiological flow waveforms.

Thrombus in a femoral artery may form under stagnant flow conditions which vary depending on the local arterial waveform. Four different physiological flow waveforms - poor (blunt) monophasic, sharp monophasic, biphasic and triphasic - can exist in the femoral artery as a result of different levels of peripheral arterial disease progression. This study aims to examine the effect of different physiological waveforms on femoral artery haemodynamics. In this regard, a fluid-structure interaction analysis was carried out in idealised models of bifurcated common femoral artery. The results showed that recirculation zones occur in almost all flow waveforms; however, the sites at where these vortices are initiated, the size and structure of vortices are highly dependent on the type of flow waveform being used. It was shown that the reverse diastolic flow in biphasic and triphasic waveforms leads to the occurrence of a retrograde flow which aids in 'washout' of the disturbed flow regions. This may limit the likelihood of thrombus formation, indicating the antithrombotic role of retrograde flow in femoral arteries. Furthermore, our data revealed that the flow particles experience considerably higher residence time under blunt and sharp monophasic waveforms than under biphasic and triphasic waveforms. This confirms that the risk of atherothrombotic plaque initiation and development in femoral arteries is higher under blunt and sharp monophasic waveforms than under biphasic and triphasic flow waveforms.

The Hemodynamic Effects of Hemodialysis Needle Rotation and Orientation in an Idealized Computational Model.

Maintaining the patency of vascular access is essential for performing efficient hemodialysis. Appropriate cannulation technique is critical in maintaining the integrity of vascular access. This study focused on analyzing the hemodynamic effect of needle rotation, which is performed to alleviate the pressure if the needle becomes attached to the blood vessel wall. The hemodynamic benefits (normal wall shear stress [WSS] and smooth flow with no oscillatory motion) of this technique are investigated in an idealized model of the cephalic vein in order to determine a needle position that will reduce conditions known to contribute to vascular access failure. A computational fluid dynamics study was conducted, with antegrade and retrograde orientations simulated on the arterial needle, whereas the venous needle is placed in the antegrade orientation. In every case, needle rotation offered no hemodynamic benefit in minimizing the conditions known to cause endothelial damage, a precursor to vascular access failure. Venous needle rotation reduced the maximum WSS by 30%. However, the WSS was above the range, which may damage the endothelial layer. The arterial needle in the antegrade orientation produced a large region of oscillatory shear, whereas a retrograde orientation produced a region of smooth flow in the vicinity of the needle with only a small region of oscillatory shear. The flow through the venous needle back eye was negligible, whereas the arterial needle back eye was more efficient in the retrograde orientation. Therefore, the venous needle should not be rotated, whereas the arterial needle may be rotated to alleviate pressure with consideration given to the orientation of the needle.

Energy Storage and Return Prostheses: A Review of Mechanical Models.

Conventional lower-limb mechanical models were originally developed for gait analysis of ablebodied Conventional lower-limb mechanical models were originally developed for gait analysis of ablebodied subjects and therefore potentially misrepresent prosthetic foot behavior when applied to modern energy storage and return (ESAR) prostheses. This review investigates the limitations of current models of prosthetic foot dynamics and kinematics. The Scopus online database was used to identify 236 articles on prosthetic foot behavior during either experiments or simulations, categorized into three main types of models: 74% (n = 175) of studies featured a rigid-link model, 17% (n = 39) a lumped-parameter model and 10% (n = 23) finite element (FE) analysis. Notably, 64% (n = 152) of the studies used a conventional two-link segment model, yet only 8% (n = 20) featured the rigid, articulating prosthesis that satisfies this model's underlying rigid-body mechanics assumptions. Conversely, the available preliminary studies on multi-link segment, lumped-parameter and FE models present viable and more mechanically relevant alternatives to conventional techniques, particularly for ESAR prostheses. Expanding these alternative models to include inertial behavior, multiple-degrees of freedom and standardization of boundary conditions will lead towards both accurate and standardized prosthetic foot analysis.