Computational Tools for the Investigation of the Male Lower Urinary Tract Functionality in Health and Disease

Purpose This paper aims to show the potentialities of computational bioengineering in the field of lower urinary tract pathophysiology. Engineering methods allow the investigation of urine flow in healthy and pathologic conditions and the analysis of urethral occlusion by means of artificial urinary sphincters. Methods Computational models of bladder and urethra were developed and exploited to investigate the lower urinary tract physiology in health and in disease. Average male morphometric configurations were assumed, together with typical properties of both biological tissues and fluids. The reliability of the models was assessed by the mutual comparison of results and the investigation of data from experimental and clinical activities. Results The developed models allowed to analyze typical situations, such as the micturition in health and in disease, and the lumen occlusion by external devices. The models provided information that clinical and experimental tests barely provide, as the occurrence of turbulent phenomena within urine flow, the shear stresses at the lumen wall, the external pressure that is strictly required to occlude the lumen. Conclusions The methods of bioengineering allow broadening and deepening the knowledge of the lower urinary tract functionality. More in detail, modeling techniques provide information that contributes to explain the occurrence of pathological situations, and allows to design and to optimize clinical-surgical procedures and devices

Computational Biomechanics: In-Silico Tools for the Investigation of Surgical Procedures and Devices

Biomechanical investigations of surgical procedures and devices are usually developed by means of human or animal models. The exploitation of computational methods and tools can reduce, refine, and replace (3R) the animal experimentations for scientific purposes and for pre-clinical research. The computational model of a biological structure characterizes both its geometrical conformation and the mechanical behavior of its building tissues. Model development requires coupled experimental and computational activities. Medical images and anthropometric information provide the geometrical definition of the computational model. Histological investigations and mechanical tests on tissue samples allow for characterizing biological tissues\u2019 mechanical response by means of constitutive models. The assessment of computational model reliability requires comparing model results and data from further experimentations. Computational methods allow for the in-silico analysis of surgical procedures and devices\u2019 functionality considering many different influencing variables, the experimental investigation of which should be extremely expensive and time consuming. Furthermore, computational methods provide information that experimental methods barely supply, as the strain and the stress fields that regulate important mechano-biological phenomena. In this work, general notes about the development of biomechanical tools are proposed, together with specific applications to different fields, as dental implantology and bariatric surgery

Formulation of constitutive models for the analysis of biomechanical behaviour of soft biological tissues

PhD Thesi

Computational Biomechanics: In-Silico Tools for the Investigation of Surgical Procedures and Devices

Biomechanical investigations of surgical procedures and devices are usually developed by means of human or animal models. The exploitation of computational methods and tools can reduce, refine, and replace (3R) the animal experimentations for scientific purposes and for pre-clinical research. The computational model of a biological structure characterizes both its geometrical conformation and the mechanical behavior of its building tissues. Model development requires coupled experimental and computational activities. Medical images and anthropometric information provide the geometrical definition of the computational model. Histological investigations and mechanical tests on tissue samples allow for characterizing biological tissues’ mechanical response by means of constitutive models. The assessment of computational model reliability requires comparing model results and data from further experimentations. Computational methods allow for the in-silico analysis of surgical procedures and devices’ functionality considering many different influencing variables, the experimental investigation of which should be extremely expensive and time consuming. Furthermore, computational methods provide information that experimental methods barely supply, as the strain and the stress fields that regulate important mechano-biological phenomena. In this work, general notes about the development of biomechanical tools are proposed, together with specific applications to different fields, as dental implantology and bariatric surgery

A review of recent findings about stress relaxation in the respiratory system tissues

This article reviews the state of the art about an unclear physiological phenomenon interesting respiratory system tissues, i.e., stress-relaxation. Due to their viscoelastic properties, the tissues do not maintain constant stress under constant deformation. Rather, the stress slowly relaxes and falls to a lower value. The exact molecular basis of this complex visco-elastic behavior is not well defined, but it has been suggested that it may be generated because of the anisotropic mechanical properties of elastin and collagen fibers in the alveolar septa and their interaction phenomena, such as reciprocal sliding, also in relation to interstitial liquid movements. The effects on stressrelaxation of various biochemical and physical factors are reviewed, including the consequences of body temperature variations, respiratory system inflammations and hyperbaric oxygen exposure, endocrinal factors, circulating blood volume variations, changes in inflation volume and/ or flow, changes in intra-abdominal pressure because of pneumoperitoneum or Trendelenburg position. The effects of these factors on stress-relaxation have practical consequences because, depending on visco-elastic pressure amount which is requested to inflate the respiratory system in different conditions, respiratory muscles have to produce different values of inspiratory pressure during spontaneous breathing. High inspiratory pressure values might increase the risk of respiratory failure development on mechanical basis

The volume dependence of stress relaxation in the rat respiratory system

Aim: To investigate the volume dependence of respiratory system stress relaxation in anesthetized, positive-pressure ventilated rats. Materials and methods: The effects on respiratory system stress relaxation of changing the end inflation volume while keeping tidal volume constant, and of changing the tidal volume while maintaining constant end inflation volume, were separately studied by the end-inflation occlusion method. These changes were obtained by inflating the respiratory system starting from different volumes above functional residual capacity. Results: We found that: (1) a simple exponential equation well describe the visco-elastic pressure drop for different inflation modalities; (2) the stress relaxation-linked, visco-elastic pressure drop, increases with increasing the tidal volume and keeping the end-inflation volume constant, but is independent from the end-inflation lung volume at constant tidal volumes; (3) time constant values show a significant increment with end-inflation volume at constant tidal volume but result independent from tidal volume variation at constant end-inflation volume. Conclusions: Stress relaxation-linked pressure dissipation increases with increasing tidal volume independently from end-inspiratory volume

Biomechanics of Hollow Organs: Experimental Testing and Computational Modeling

Hollow organs are visceral organs that are hollow tubes or pouches (such as the intestine or the stomach, respectively) or that include a cavity (such as the heart) and which subserve a vital function [...