Altered total cavopulmonary connection (TCPC) hemodynamics can cause long-term complications. Patient-specific anatomy hinders generalized solutions. 4D Flow MRI allows in vivo assessment, but not predictions under varying conditions and surgical approaches. Computational fluid dynamics (CFD) improves understanding and explores varying physiological conditions. This study investigated a combination of 4D Flow MRI and CFD to assess TCPC hemodynamics, accompanied with in vitro measurements as CFD validation. 4D Flow MRI was performed in extracardiac and atriopulmonary TCPC subjects. Data was processed for visualization and quantification of velocity and flow. Three-dimensional (3D) geometries were generated from angiography scans and used for CFD and physical model construction through additive manufacturing. These models were connected to a perfusion system, circulating water through the vena cavae and exiting through the pulmonary arteries at two flow rates. Models underwent 4D Flow MRI and image processing. CFD simulated the in vitro system, applying two different inlet conditions from in vitro 4D Flow MRI measurements; no-slip was implemented at rigid walls. Velocity and flow were obtained and analyzed. The three approaches showed similar velocities, increasing proportionally with high inflow. Atriopulmonary TCPC presented higher vorticity compared to extracardiac at both inflow rates. Increased inflow balanced flow distribution in both TCPC cases. Atriopulmonary IVC flow participated in atrium recirculation, contributing to RPA outflow; at baseline, IVC flow preferentially travelled through the LPA. The combination of patient-specific in vitro and CFD allows hemodynamic parameter control, impossible in vivo. Physical models serve as CFD verification and fine-tuning tools.

To improve the damage resistance and tolerance of thin laminates manufactured with thin-ply non-crimp-fabrics, we interleaved non-woven veils (two different types of co-polyamide veil were studied) into the interlaminar regions. We devised an impact, compression after impact (CAI) and quasi-static indentation experimental campaign, where X-ray micro-computed tomography illustrated how: (a) matrix cracking, delamination and fibre failure interact during out-of-plane loading and (b) interleaving affects the thickness of the interface. One type of thermoplastic interlayer avoided resin accumulation, reduced the initiation of delamination and improved CAI strength by up to 28%.

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Trabecular bone tissue is a three-dimensional structure that is difficult to duplicate with in vitro cell cultures or animal models. In an attempt to better understand the underlying mechanisms of tissue response to load, a system to load isolated bone preparations was developed. This ex vivo bone culture and loading system, given the name of ZETOS, compressively loads trabecular bone (10mm diameter, 5.0mm height) to evaluate its morphological and physiological responses while keeping cells viable. Compliance of the system may change with time, thus requiring recalibration. The purpose of this research was to develop and validate a recalibration protocol for the ZETOS system. Ten reference bodies (RBs) were designed and machined out of aluminum 7075-T6, with a structural rigidity range representative of trabecular bone (0.628–28.3N∕μm, or apparent elastic modulus of 40MPa–1.80GPa). Finite element analysis (FEA) was used to calculate the rigidity of each RB and was validated with physical testing in a universal testing machine. Results from FEA were then used to calibrate the system and relate force, piezoelectric actuator expansion, and specimen compressive deformation through a surface generated by spline interpolation, thus creating a calibration table. Calibration of ZETOS was verified by testing the RBs as well as three custom-made, metal springs and comparing measured rigidity to that calculated by FEA. Mean percent difference of FEA results with respect to those from physical testing was 3.28%. The mean percent difference of RB rigidity found with ZETOS with respect to rigidity found with FEA was 1.12% and for the metal springs, the mean percent difference was 1.74%. The calibration procedure for the ZETOS bone loading system has been successfully applied and verified. The use of RBs and FEA allows users to easily and periodically evaluate and recalibrate the system. Accuracy in studies of human bone mechanotransduction in a controlled environment can therefore be achieved. The recalibration procedure is relevant for other ZETOS users and may serve as the basis for calibration of other testing systems for small specimens of compliant materials.

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Severe respiratory sequelae drive morbidity-associated with coronavirus 2019 (COVID-19) disease. We report a case of COVID-19 pneumonia complicated by cavitary lesions and pneumothorax in a young healthy male. Pneumothorax management with catheter thoracostomy and rapid resolution of the cavitary lesions are described. An extensive work-up for other causes a cavitation was negative and the temporal correlation of the cavities with COVID-19 infection plus their rapid resolution suggest a direct relationship. We propose a mechanism for cavitation secondary to microangiopathy, a cause of cavitation in the vasculitides and a known feature of COVID-19.

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