Predicting oxygen tension along the ureter

2021 ◽  
Author(s):  
Chang-Joon Lee ◽  
Bruce S. Gardiner ◽  
Roger G. Evans ◽  
David W. Smith
Keyword(s):  
Oxygen Tension ◽  
Kidney Injury ◽  
Model Parameters ◽  
Bolus Volume ◽  
Surface Area Ratio ◽  
Average Percentage ◽  
Linear Relationships ◽  
Percentage Difference ◽  
Patients At Risk ◽  
Bladder Urine

Continuous measurement of bladder urine oxygen tension (PO2) is a new method to potentially detect renal medullary hypoxia in patients at risk of acute kidney injury (AKI). To assess its practicality, we developed a computational model of the peristaltic movement of a urine bolus along the ureter and the oxygen exchange between the bolus and ureter wall. This model quantifies the changes in urine PO2 as it transits from the renal pelvis to the bladder. The model parameters were calibrated using experimental data in rabbits, such that most of the model predictions are within ± 1 standard error (SEM) of the reported mean in the experiment, with the average percentage difference being 7.0%. Based on parametric studies performed using a model scaled to the geometric dimensions of a human ureter, we found that bladder-urine PO2 is strongly dependent on the bolus volume (i.e. bolus volume-to-surface area ratio), especially at a volume less than its physiological (baseline) volume (<0.2 ml). For the model assumptions, changes in peristaltic frequency resulted in a minimal change in bladder-urine PO2 (< 1 mmHg). The model also predicted there exists a family of linear relationships of the bladder-urine PO2 and the pelvic-urine PO2 for different input conditions. We conclude that it may technically be possible to predict renal medullary PO2 based on the measurement of bladder-urine PO2, provided there are accurate real-time measurements of model input parameters.

scholarly journals Bladder urine oxygen tension for assessing renal medullary oxygenation in rabbits: experimental and modeling studies

2016 ◽  
Vol 311 (3) ◽  
pp. R532-R544 ◽  
Author(s):  
Ioannis Sgouralis ◽  
Michelle M. Kett ◽  
Connie P. C. Ow ◽  
Amany Abdelkader ◽  
Anita T. Layton ◽  
...  
Keyword(s):  
Acute Kidney Injury ◽  
Computational Model ◽  
Oxygen Tension ◽  
Oxygen Diffusion ◽  
Kidney Injury ◽  
Urine Flow ◽  
Flow Changes ◽  
Single Kidney ◽  
Pelvic Urine ◽  
Bladder Urine

Oxygen tension (Po2) of urine in the bladder could be used to monitor risk of acute kidney injury if it varies with medullary Po2. Therefore, we examined this relationship and characterized oxygen diffusion across walls of the ureter and bladder in anesthetized rabbits. A computational model was then developed to predict medullary Po2 from bladder urine Po2. Both intravenous infusion of [Phe2,Ile3,Orn8]-vasopressin and infusion of NG-nitro-l-arginine reduced urinary Po2 and medullary Po2 (8–17%), yet had opposite effects on renal blood flow and urine flow. Changes in bladder urine Po2 during these stimuli correlated strongly with changes in medullary Po2 (within-rabbit r2 = 0.87–0.90). Differences in the Po2 of saline infused into the ureter close to the kidney could be detected in the bladder, although this was diminished at lesser ureteric flow. Diffusion of oxygen across the wall of the bladder was very slow, so it was not considered in the computational model. The model predicts Po2 in the pelvic ureter (presumed to reflect medullary Po2) from known values of bladder urine Po2, urine flow, and arterial Po2. Simulations suggest that, across a physiological range of urine flow in anesthetized rabbits (0.1–0.5 ml/min for a single kidney), a change in bladder urine Po2 explains 10–50% of the change in pelvic urine/medullary Po2. Thus, it is possible to infer changes in medullary Po2 from changes in urinary Po2, so urinary Po2 may have utility as a real-time biomarker of risk of acute kidney injury.

scholarly journals Factors that confound the prediction of renal medullary oxygenation and risk of acute kidney injury from measurement of bladder urine oxygen tension

2019 ◽  
pp. e13294 ◽  
Author(s):  
Jennifer P. Ngo ◽  
Yugeesh R. Lankadeva ◽  
Michael Z. L. Zhu ◽  
Andrew Martin ◽  
Monica Kanki ◽  
...  
Keyword(s):  
Acute Kidney Injury ◽  
Oxygen Tension ◽  
Kidney Injury ◽  
Bladder Urine

Urinary oxygen tension: a clinical window on the health of the renal medulla?

2014 ◽  
Vol 306 (1) ◽  
pp. R45-R50 ◽  
Author(s):  
Roger G. Evans ◽  
Julian A. Smith ◽  
Christopher Wright ◽  
Bruce S. Gardiner ◽  
David W. Smith ◽  
...  
Keyword(s):  
Oxygen Tension ◽  
Kidney Injury ◽  
Renal Medulla ◽  
Detailed Knowledge ◽  
Bedside Monitoring ◽  
Quantitative Understanding ◽  
The Impact ◽  
The Relationship ◽  
Pelvic Urine ◽  
Bladder Urine

We describe the determinants of urinary oxygen tension (Po2) and the potential for use of urinary Po2 as a “physiological biomarker” of the risk of acute kidney injury (AKI) in hospital settings. We also identify knowledge gaps required for clinical translation of bedside monitoring of urinary Po2. Hypoxia in the renal medulla is a hallmark of AKI of diverse etiology. Urine in the collecting ducts would be expected to equilibrate with the tissue Po2 of the inner medulla. Accordingly, the Po2 of urine in the renal pelvis changes in response to stimuli that would be expected to alter oxygenation of the renal medulla. Oxygen exchange across the walls of the ureter and bladder will confound measurement of the Po2 of bladder urine. Nevertheless, the Po2 of bladder urine also changes in response to stimuli that would be expected to alter renal medullary oxygenation. If confounding influences can be understood, urinary bladder Po2 may provide prognostically useful information, including for prediction of AKI after cardiopulmonary bypass surgery. To translate bedside monitoring of urinary Po2 into the clinical setting, we require 1) a more detailed knowledge of the relationship between renal medullary oxygenation and the Po2 of pelvic urine under physiological and pathophysiological conditions; 2) a quantitative understanding of the impact of oxygen transport across the ureteric epithelium on urinary Po2 measured from the bladder; and 3) a simple, robust medical device that can be introduced into the bladder via a standard catheter to provide reliable and continuous measurement of urinary Po2.

scholarly journals Accounting for oxygen in the renal cortex: a computational study of factors that predispose the cortex to hypoxia

2017 ◽  
Vol 313 (2) ◽  
pp. F218-F236 ◽  
Author(s):  
Chang-Joon Lee ◽  
Bruce S. Gardiner ◽  
Jennifer P. Ngo ◽  
Saptarshi Kar ◽  
Roger G. Evans ◽  
...  
Keyword(s):  
Oxygen Tension ◽  
Renal Cortex ◽  
Computational Study ◽  
Ischemia Reperfusion ◽  
Sodium Reabsorption ◽  
Model Parameters ◽  
Arterial Blood ◽  
Increased Risk ◽  
Renal Oxygen Consumption ◽  
Renal Oxygen

We develop a pseudo-three-dimensional model of oxygen transport for the renal cortex of the rat, incorporating both the axial and radial geometry of the preglomerular circulation and quantitative information regarding the surface areas and transport from the vasculature and renal corpuscles. The computational model was validated by simulating four sets of published experimental studies of renal oxygenation in rats. Under the control conditions, the predicted cortical tissue oxygen tension ([Formula: see text]) or microvascular oxygen tension (µPo2) were within ±1 SE of the mean value observed experimentally. The predicted [Formula: see text] or µPo2 in response to ischemia-reperfusion injury, acute hemodilution, blockade of nitric oxide synthase, or uncoupling mitochondrial respiration, were within ±2 SE observed experimentally. We performed a sensitivity analysis of the key model parameters to assess their individual or combined impact on the predicted [Formula: see text] and µPo2. The model parameters analyzed were as follows: 1) the major determinants of renal oxygen delivery ([Formula: see text]) (arterial blood Po2, hemoglobin concentration, and renal blood flow); 2) the major determinants of renal oxygen consumption (V̇o2) [glomerular filtration rate (GFR) and the efficiency of oxygen utilization for sodium reabsorption (β)]; and 3) peritubular capillary surface area (PCSA). Reductions in PCSA by 50% were found to profoundly increase the sensitivity of [Formula: see text] and µPo2 to the major the determinants of [Formula: see text] and V̇o2. The increasing likelihood of hypoxia with decreasing PCSA provides a potential explanation for the increased risk of acute kidney injury in some experimental animals and for patients with chronic kidney disease.

An Investigation on Bending Capacity of Support Stiffness Wall-Slab Structural System by Using Single Layer and Double Layer of Rebar for Residential Project

2012 ◽  
Vol 446-449 ◽  
pp. 3670-3673
Author(s):  
Hooi Min Yee ◽  
Siti Isma Hani Ismail
Keyword(s):  
Double Layer ◽  
Concrete Strength ◽  
Single Layer ◽  
Concrete Cover ◽  
Structural System ◽  
Average Percentage ◽  
High Rise ◽  
Percentage Difference ◽  
Average Percentage Difference ◽  
Bending Capacity

Wall-slab structural system is a system suitable for use in the field of high-rise building where the main load resisting system is in the form rigidly connected wall slab member. Concrete vertical walls may serve both architecturally partitions and structurally to carry gravity and lateral loading. Moment transfer of joint is an important aspect for proper structurally functioning of wall-slab system. Hence, the main aim of this study is to investigate experimentally the effect of reinforcement details in the wall on bending capacity for support stiffness in wall-slab system for residential project in Malaysia. A total of six wall specimens were tested based on the specification given by the project contractor. Three of this specimens consisted single layer of rebar while another three specimen consisted of double layer of rebar. The size of the wall-slab’s specimens is 1000mm in length (L), 1080mm in width (W), 1000mm in height (H) and 80mm in thickness (T). The average concrete strength was 23.49MPa with Grade 30N/mm2 and the average yield strength of R5 bar was 817MPa. The predicted bending capacity at failure is in the range from 5.36kNm to 7.12kNm, depending on actual concrete cover. The bending capacity at failure for single layered of rebar in wall for specimen 1, 2 and 3 were found to be 3.59kNm, 3.81kNm and 3.15kNm, respectively. The bending capacity at failure for double layered of rebar in wall for specimen 1, 2 and 3 were 5.50kNm, 6.31kNm and 7.00kNm, respectively. The average percentage difference in stiffness of double layered of rebar in wall based on load-deflection curve obtained is in the range from 116.17% to 289.88% higher than single layered of rebar in wall. Based on the experimental results, specimens consisted of double layered of rebar in wall is found to provide higher bending capacity to the joint of wall-slab structural system in the range from 56.25% to 98.86% compared with single layered of rebar in wall.

scholarly journals Preventing Contrast-induced Renal Failure: A Guide

2016 ◽  
Vol 11 (2) ◽  
pp. 98 ◽  
Author(s):  
Michela Faggioni ◽  
◽  
Roxana Mehran ◽  
Keyword(s):  
Risk Factors ◽  
Renal Damage ◽  
Preventive Measures ◽  
Kidney Injury ◽  
Coronary Intervention ◽  
Kidney Dysfunction ◽  
Percutaneous Coronary ◽  
Patients At Risk ◽  
Short And Long Term

Contrast-induced acute kidney injury (CI-AKI) is characterised by a rapid deterioration of renal function within a few days of parenteral administration of contrast media (CM) in the absence of alternative causes. CI-AKI is the most common form of iatrogenic kidney dysfunction with an estimated prevalence of 12 % in patients undergoing percutaneous coronary intervention. Although usually selfresolving, in patients with pre-existing chronic kidney disease (CKD) or concomitant risk factors for renal damage, CI-AKI is associated with increased short- and long-term morbidity and mortality. Therefore, risk stratification based on clinical and peri-procedural characteristics is crucial in selecting patients at risk of CI-AKI who would benefit the most from implementation of preventive measures.

scholarly journals Three-dimensional data-tracking simulations of sprinting using a direct collocation optimal control approach

PeerJ ◽  
2021 ◽  
Vol 9 ◽  
pp. e10975
Author(s):  
Nicos Haralabidis ◽  
Gil Serrancolí ◽  
Steffi Colyer ◽  
Ian Bezodis ◽  
Aki Salo ◽  
...  
Keyword(s):  
Experimental Data ◽  
Reaction Force ◽  
Three Dimensional ◽  
Contact Model ◽  
Model Parameters ◽  
Ground Contact ◽  
Control Approach ◽  
Average Percentage ◽  
Data Tracking ◽  
The Individual

Biomechanical simulation and modelling approaches have the possibility to make a meaningful impact within applied sports settings, such as sprinting. However, for this to be realised, such approaches must first undergo a thorough quantitative evaluation against experimental data. We developed a musculoskeletal modelling and simulation framework for sprinting, with the objective to evaluate its ability to reproduce experimental kinematics and kinetics data for different sprinting phases. This was achieved by performing a series of data-tracking calibration (individual and simultaneous) and validation simulations, that also featured the generation of dynamically consistent simulated outputs and the determination of foot-ground contact model parameters. The simulated values from the calibration simulations were found to be in close agreement with the corresponding experimental data, particularly for the kinematics (average root mean squared differences (RMSDs) less than 1.0° and 0.2 cm for the rotational and translational kinematics, respectively) and ground reaction force (highest average percentage RMSD of 8.1%). Minimal differences in tracking performance were observed when concurrently determining the foot-ground contact model parameters from each of the individual or simultaneous calibration simulations. The validation simulation yielded results that were comparable (RMSDs less than 1.0° and 0.3 cm for the rotational and translational kinematics, respectively) to those obtained from the calibration simulations. This study demonstrated the suitability of the proposed framework for performing future predictive simulations of sprinting, and gives confidence in its use to assess the cause-effect relationships of technique modification in relation to performance. Furthermore, this is the first study to provide dynamically consistent three-dimensional muscle-driven simulations of sprinting across different phases.

scholarly journals Atrial Fibrillation and Chronic Kidney Disease—A Risky Combination for Post-Contrast Acute Kidney Injury

2021 ◽  
Vol 10 (18) ◽  
pp. 4140
Author(s):  
Łukasz Kuźma ◽  
Anna Tomaszuk-Kazberuk ◽  
Anna Kurasz ◽  
Małgorzata Zalewska-Adamiec ◽  
Hanna Bachórzewska-Gajewska ◽  
...  
Keyword(s):  
Atrial Fibrillation ◽  
Chronic Kidney Disease ◽  
Acute Kidney Injury ◽  
Kidney Disease ◽  
Coronary Angiography ◽  
Kidney Injury ◽  
Post Contrast ◽  
Acute Kidney Disease ◽  
Patients At Risk ◽  
Kidney Impairment

Atrial fibrillation (AF) symptoms may mimic coronary artery disease (CAD) which reflects the difficulties in qualifying AF patients for invasive diagnostics. A substantial number of coronary angiographies may be unnecessary or even put patients at risk of post-contrast acute kidney injury (PC-AKI), especially patients with chronic kidney disease (CKD). We aimed to investigate the hypothesis indicating higher prevalence of PC-AKI in patients with AF scheduled for coronary angiography. The study population comprised of 8026 patients referred for elective coronarography including 1621 with AF. In the comparison of prevalence of PC-AKI in distinguished groups we can see that kidney impairment was twice more frequent in patients with AF in both groups with CKD (CKD (+)/AF (+) 6.24% vs. CKD (+)/AF (−) 3.04%) and without CKD (CKD (−)/AF (+) 2.32% vs. CKD (−)/AF (−) 1.22%). In our study, post-contrast acute kidney disease is twice more frequent in patients with AF, especially in subgroup with chronic kidney disease scheduled for coronary angiography. Additionally, having in mind results of previous studies stating that AF is associated with non-obstructive coronary lesions on angiography, patients with AF and CKD may be unnecessarily exposed to contrast agent and possible complications.

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