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The biomechanical response of a human rib cage to cardiopulmonary resuscitation maneuvers was investigated by means of finite element simulations. We analyzed the effect of the location where the force was applied on the achieved compression depths and stress levels experienced by the breastbone and ribs. For compression locations on the breastbone, a caudal shift of the application area toward the breastbone tip resulted in a 17% reduction of the force required to achieve a target 5 cm compression depth. We found that the use of compression regions located on the costal cartilages would involve higher risk of rib fractures.

Computational fluid dynamics was used to simulate the flow of blood within an inferior vena cava (IVC) geometry model that was reconstructed from computed tomography images obtained from a real patient. The main novelty of the present work is that we simulated the implantation of 4 different filter models in this realistic IVC geometry. We considered different blood flow rates in the range between V =20 and V =80 cm /s, and all simulations were performed with both the Newtonian and a non-Newtonian model for the blood viscosity. We compared the hemodynamics performance of the different filter models, and we paid a special attention to the total drag force, F , exerted by the blood flow on the filter surface. This force is the sum of 2 contributions: the viscous skin friction force, which was found to be roughly proportional to the filter surface area, and the pressure force, which depended on the particular filter geometry design. The F force is relevant because it must be balanced by the total force exerted by the filter hooks/struts on the IVC wall at the attachment locations. For the highest V value investigated, the variation in F among filters was from 116 to 308 dyne. We also showed how the present results can be extrapolated to obtain good estimates of the drag forces if the blood viscosity levels change, ie, if the patient with a filter implanted is treated with anticoagulant therapy.

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An ostomy is a surgical procedure by which an artificial opening in the abdominal wall, known as a stoma, is created. We assess the effects of stoma location on the abdominal wall mechanics. We perform three-dimensional finite element simulations on an anatomy model which was generated on the basis of medical images. Our simulation methodology is entirely based on open source software. We consider seventeen different locations for the stoma incision (trephine) and we simulate the mechanical response of the abdominal wall when an intraabdominal pressure as high as 20 kPa is applied. We focus on factors related to the risk of parastomal hernia development such as the deformation experienced by the abdominal wall, the stress levels supported by its tissues and the corresponding level of trephine enlargement. No significant dependence was found between stoma location and the levels of abdominal wall deformations or stress supported by tissues, except for the case with a stoma located on the linea alba. Trephine perimeter and area respectively increased by as much as $$44\%$$ 44 % and $$85\%$$ 85 % . The level of trephine deformation depends on stoma location with considerably higher trephine enlargements found in stomas laterally located with respect to the rectus abdominis muscle.

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The effect of the dimensions of the thoracic cage on the resuscitation outcome of cardiopulmonary resuscitation (CPR) maneuvers has long been debated. In this study, the effect of changes in the rib cage dimensions on the achieved compression depth was investigated using finite element simulations. A total of 216 different rib cage geometry models were considered and, in each case, the result of applying different levels of compression force up to 600 N were simulated. The Haller Index of the rib cage is defined as the ratio of the transverse diameter and the antero-posterior diameter. Our results suggest that, with a fixed level of compression force, performing CPR on rib cages having a low Haller Index and/or a larger height leads to compression depths below the average. Alternatively, if a target compression depth is set for CPR, in general a lower compression force would be required for individuals with higher Haller Index and/or lower chest height. In addition, present results indicate that wider chested individuals will experience lower stress levels on their ribs to achieve the required CPR target depth. Moreover, in the present study we propose predictive models, based on anthropometric parameters, for compression depth and rib stress during chest compressions. In particular, the model suggests that in future correlations of empirical CPR data the patients' Haller index and vertical (sagittal) cross-area are the best parameters to be used as independent variables in a fit.

The alteration of blood flow around an OPTEASE inferior vena cava filter with one or two blood clots attached was investigated by means of computational fluid dynamics. We used a patient‐specific vein wall geometry, and we generated different clot models with shapes adapted to the filter and vein wall geometries. A total of eight geometries, with one or two clots and a total clot volume of 0.5 or 1 cm3, were considered. A non‐Newtonian model for blood viscosity was adopted and the possible development of turbulence was accounted for by means of a three‐equation model. Two blood flow rates were considered for each case, representative for rest and exercise conditions. In exercise conditions, flow unsteadiness and even turbulence was detected in some cases. Pressure and wall shear stress (WSS) distributions were modified in all cases. Clots attached to the filter downstream basket considerably increased averaged WSS values by up to almost 50%. In all the cases a flow recirculation region appeared downstream of the clot. The degree of flow stagnation in these regions, an indicator of propensity to thrombogenesis, was estimated in terms of mean residence times and mean blood viscosity. High levels of flow stagnation were detected in rest conditions in the wake of those clots that were placed upstream from the filter. Our results suggest that one downstream placed big clot, showing a higher tendency to induce flow instabilities and turbulence, might be more harmful than two small clots placed in tandem.