Inferior epigastric artery false aneurysm following incisional hernia repair

AbstractIntroductionWe report a case of IEA false aneurysm following a mesh repair of a large incisional hernia. We emphasize the importance to consider the diagnosis to help avoid inappropriate interventions which could increase patient morbidity.Case reportA 68-year-old male patient, who 4 weeks previously had had a mesh repair of a large incisional hernia, presented with a painful left iliac fossa swelling. This was found to be an IEA false aneurysm. This was treated successfully with percutaneous thrombin injection.ConclusionsWe feel an inferior epigastric artery false aneurysm must be included in the differential diagnosis when investigating the cause of any lateral swelling following incisional hernia repair. This would help reduce the chance of a missed diagnosis and avoid any inappropriate interventions which may cause increased patient morbidity

Non-identifiability of the Rayleigh damping material model in magnetic resonance elastography

Magnetic Resonance Elastography (MRE) is an emerging imaging modality for quantifying soft tissue elasticity deduced from displacement measurements within the tissue obtained by phase sensitive Magnetic Resonance Imaging (MRI) techniques. MRE has potential to detect a range of pathologies, diseases and cancer formations, especially tumors. The mechanical model commonly used in MRE is linear viscoelasticity (VE). An alternative Rayleigh damping (RD) model for soft tissue attenuation is used with a subspace-based nonlinear inversion (SNLI) algorithm to reconstruct viscoelastic properties, energy attenuation mechanisms and concomitant damping behavior of the tissue-simulating phantoms. This research performs a thorough evaluation of the RD model in MRE focusing on unique identification of RD parameters, μIμI and ρIρI. Results show the non-identifiability of the RD model at a single input frequency based on a structural analysis with a series of supporting experimental phantom results. The estimated real shear modulus values (μRμR) were substantially correct in characterising various material types and correlated well with the expected stiffness contrast of the physical phantoms. However, estimated RD parameters displayed consistent poor reconstruction accuracy leading to unpredictable trends in parameter behaviour. To overcome this issue, two alternative approaches were developed: (1) simultaneous multi-frequency inversion; and (2) parametric-based reconstruction. Overall, the RD model estimates the real shear shear modulus (μRμR) well, but identifying damping parameters (μIμI and ρIρI) is not possible without an alternative approach

Integral-Based Identification of an Inhomogeneity Model in Respiratory Mechanics

4-pagesIndividualized models of respiratory mechanics may help to reduce potential harmful effects of ventilation therapy by predicting the outcome of certain ventilator settings. The underlying models are commonly identified by iterative error-mapping methods, such as the Levenberg-Marquardt Algorithm, requiring initial estimates for the patient specific parameters. The quality of the initial estimates has a significant influence on identification efficiency and results. An iterative integral-based parameter identification method was applied to a linear 2nd order respiratory mechanics model. The method was compared to the Levenberg-Marquardt Algorithm using clinical data from 13 Acute Respiratory Distress Syndrome (ARDS) patients. The Iterative Integral-Based Method converged to the Levenberg-Marquardt solution two times faster and was independent of initial estimates. These investigations reveal that the Iterative Integral-Based Method is beneficial with respect to computing time, operator independence and robustness

A Minimal C-Peptide Sampling Method to Capture Peak and Total Pre-Hepatic Insulin Secretion in Model-Based Experimental Insulin Sensitivity Studies

Aims and Background: Model-based insulin sensitivity testing via the intravenous glucose tolerance test (IVGTT) or similar is clinically very intensive due to the need for frequent sampling to accurately capture the dynamics of insulin secretion and clearance. The goal of this study was to significantly reduce the number of samples required in intravenous glucose tolerance test protocols to accurately identify C-peptide and insulin secretion characteristics. Methods: Frequently sampled IVGTT data from 12 subjects [5 normal glucose-tolerant (NGT) and 7 type 2 diabetes mellitus (T2DM)] were analyzed to calculate insulin and C-peptide secretion using a well-accepted C-peptide model. Samples were reduced in a series of steps based on the critical IVGTT profile points required for the accurate estimation of C-peptide secretion. The full data set of 23 measurements was reduced to sets with six or four measurements. The peak secretion rate and total secreted C-peptide during 10 and 20 minutes postglucose input and during the total test time were calculated. Results were compared to those from the full data set using the Wilcoxon rank sum to assess any differences. Results: In each case, the calculated secretion metrics were largely unchanged, within expected assay variation, and not significantly different from results obtained using the full 23 measurement data set (P < 0.05). Conclusions: Peak and total C-peptide and insulin secretory characteristics can be estimated accurately in an IVGTT from as few as four systematically chosen samples, providing an opportunity to minimize sampling, cost, and burden

Traversing the Fuzzy Valley: Problems caused by reliance on default simulation and parameter identification programs for discontinuous models

invited, 6-pagesThe Levenberg-Marquardt parameter identification method is often used in tandem with numerical Runge-Kutta model simulation to find optimal model parameter values to match measured data. However, these methods can potentially find erroneous parameter values. The problem is exacerbated when discontinuous models are analyzed. A highly parameterized respiratory mechanics model defines a pressure-volume response to a low flow experiment in an acute respiratory distress syndrome patient. Levenberg-Marquardt parameter identification is used with various starting values and either a typical numerical integration model simulation or a novel error-stepping method. Model parameter values from the error-stepping method were consistently located close to the error minima (median deviation: 0.4%). In contrast, model values from numerical integration were erratic and distinct from the error minima (median deviation: 1.4%). The comparative failure of Runge-Kutta model simulation was due to the method’s poor handling of model discontinuities and the resultant lack of smoothness in the error surface. As the Leven-berg-Marquardt identification system is an error gradient decent method, it depends on accurate measurement of the model-to-measured data error surface. Hence, the method failed to converge accurately due to poorly defined error surfaces. When the error surface is imprecisely identified, the parameter identification process can produce sub-optimal results. Particular care must be used when gradient decent methods are used in conjunction with numerical integration model simulation methods and discontinuous models

Respiratory airway resistance monitoring in mechanically ventilated patients

Physiological models of respiratory mechanics can be used to optimise mechanical ventilator settings to improve critically ill patient outcomes. Models are generally generated via either physical measurements or analogous behaviours that can model experimental outcomes. However, models derived solely from physical measurements are infrequently applied to clinical data. This investigation assesses the efficacy of a physically derived airway branching model (ABM) to capture clinical data. The ABM is derived via classical pressure-flow equations and branching based on known anatomy. It is compared to two well accepted lumped parameter models of the respiratory system: the linear lung model (LLM) and the Dynostatic Model (DSM). The ABM significantly underestimates the total pressure drop from the trachea to the alveoli. While the LLM and DSM both recorded peak pressure drops of 17.8 cmH2O and 10.2 cmH2O, respectively, the maximum ABM modelled pressure drop was 0.66 cmH2O. This result indicates that the anatomically accurate ABM model does not incorporate all of the airway resistances that are clinically observed in critically ill patients. In particular, it is hypothesised that the primary discrepancy is in the endotracheal tube. In contrast to the lumped parameter models, the ABM was capable of defining the pressure drop in the deep bronchial paths and thus may allow further investigation of alveoli recruitment and gas exchange at that level given realistic initial pressures at the upper airways

Validation and implementation of low-cost dynamic insulin sensitivity tests

DTM2011 handbook/programme is given in files and also available as a hard copyObjective: Insulin sensitivity (SI) tests can provide important information for type 2 diabetes risk assessment and investigations of metabolism or pre-diabetes. Our group previously presented the dynamic insulin sensitivity and secretion test (DISST) and the real-time quick DISST (DISTq) as low-cost, low-burden and accurate alternatives to established tests. The DISST provides concurrent SI and endogenous insulin secretion (UN) metrics, the DISTq does not require insulin or C-peptide assays for SI identification, but can return an immediate result. This study validates the DISST and DISTq in comparison to the euglycemic, hyperinsulinemic clamp (EIC) Method: Fifty participants (with 10 BMI>30; 10 BMI>25, <30; and 5 BMI<25 of each gender) underwent the EIC and DISST. The DISST protocol requires 5 samples from a 30 minute protocol similar to the IM-IVGTT. Data from the DISST protocol was sufficient to identify SI using both the DISST and DISTq parameter identification methods and UN from the DISST. Result: DISST and DISTq SI values correlated well to the EIC (R=0.81 and R=0.76, respectively) and each other (R=0.84). UN values obtained during the DISST showed clinically relevant distinctions between participants, and clearly differentiated the beta-cell function of impaired glucose tolerant participants who had the same EIC SI. Participant acceptance of the protocol was high with very minor reported adverse effects. Conclusion: The DISST and DISTq correlated well against the EIC compared to most established insulin sensitivity tests. The DISST can better differentiate patients as it provides UN metrics that the EIC does not. A computer program makes uptake and use of the model-based DISST and DISTq tests straightforward for clinicians and researchers

The Dynamic Insulin Sensitivity and Secretion Test (DISST) - a novel measure of insulin sensitivity

Objective: To validate the methodology for the Dynamic Insulin Sensitivity and Secretion Test (DISST) and to demonstrate its potential in clinical and research settings. Methods: 123 men and women had routine clinical and biochemical measurements, an oral glucose tolerance test and a DISST. For the DISST, participants were cannulated for blood sampling and bolus administration. Blood samples were drawn at t=0, 10, 15, 25 and 35 minutes for measurement of glucose, insulin and C-peptide. A 10g bolus of intravenous glucose at t=5 minutes and 1U of intravenous insulin immediately after the t=15 minute sample were given. Fifty participants also had a hyperinsulinaemic euglycaemic clamp. Relationships between DISST insulin sensitivity (SI) and the clamp, and both DISST SI and secretion and other metabolic variables were measured. Results: A Bland-Altman plot showed little bias in the comparison of DISST with the clamp; with DISST underestimating the glucose clamp by 0.1·10-2·mg·l·kg-1·min-1·pmol-1 (90%CI -0.2 to 0). The correlation between SI as measured by DISST and the clamp was 0.82, the c unit for the ROC analysis for the two tests was 0.96. Metabolic variables showed significant correlations with DISST IS, and the second phase of insulin release. DISST also appears able to distinguish different insulin secretion patterns in individuals with identical SI values. Conclusions: DISST is a simple, dynamic test that compares favourably with the clamp in assessing SI and allows simultaneous assessment of insulin secretion. DISST has the potential to provide even more information about the pathophysiology of diabetes than more complicated tests

Modeled Insulin Sensitivity and Interstitial Insulin Action from a Pilot Study of Dynamic Insulin Sensitivity Tests

An accurate test for insulin resistance can delay or prevent the development of Type 2 diabetes and its complications. The current gold standard test, CLAMP, is too labor intensive to be used in general practice. A recently developed dynamic insulin sensitivity test, DIST, uses a glucose-insulin-C-peptide model to calculate model-based insulin sensitivity, SI. Preliminary results show good correlation to CLAMP. However both CLAMP and DIST ignore saturation in insulin-mediated glucose removal. This study uses the data from 17 patients who underwent multiple DISTs to investigate interstitial insulin action and its influence on modeled insulin sensitivity. The critical parameters influencing interstitial insulin action are saturation in insulin receptor binding, αG, and plasma-interstitial difiusion rate, nI . Very low values of αG and very low values of nI produced the most intra-patient variability in SI. Repeatability in SI is enhanced with modeled insulin receptor saturation. Future parameter study on subjects with varying degree of insulin resistance may provide a better understanding of different contributing factors of insulin resistance

Maternal variants in NLRP and other maternal effect proteins are associated with multilocus imprinting disturbance in offspring

Background: Genomic imprinting results from the resistance of germline epigenetic marks to reprogramming in the early embryo for a small number of mammalian genes. Genetic, epigenetic or environmental insults that prevent imprints from evading reprogramming may result in imprinting disorders, which impact growth, development, behaviour and metabolism. We aimed to identify genetic defects causing imprinting disorders, by whole-exome sequencing in families with one or more members affected by multi-locus imprinting disturbance. Methods: Whole-exome sequencing was performed in 38 pedigrees where probands had multi-locus imprinting disturbance, in five of whom, maternal variants in NLRP5 have previously been found. Results: We now report 15 further pedigrees in which offspring had disturbance of imprinting, while their mothers had rare, predicted-deleterious variants in maternal-effect genes, including NLRP2, NLRP7 and PADI6. As well as clinical features of well-recognised imprinting disorders, some offspring had additional features including developmental delay, behavioural problems and discordant monozygotic twinning, while some mothers had reproductive problems including pregnancy loss. Conclusion: The identification of 20 putative maternal-effect variants in 38 families affected by multi-locus imprinting disorders adds to the evidence that maternal genetic factors affect oocyte fitness and thus offspring development. Testing for maternal-effect genetic variants should be considered in families affected by atypical imprinting disorders.<br/