# Reconstruction of the Physiological Behavior of Real and Synthetic Vessels in Controlled Conditions
## 1 Introduction  
Human organs are complex structures composed of specialized cells that collaboratively execute unique functions that are crucial for survival [1]. Ethical considerations necessitate the utilization of bio-tissue and mechanical systems that can replicate the physiological and pathophysiological aspects of organs [2]. Such systems hold the potential to provide enhanced predictive capabilities for human tissue responses compared to existing testing methodologies. Substantial progress has been made in microfluidic technologies, particularly in the context of organ-on-a-chip devices [3]. Each vascular product requires an individualized bioreactor [4]. Many important considerations should be included in the bioreactor's construction [5]. bioreactors for vascular products, as well as vascular grafts, commonly represent a pulsatile system [6]. Different parameters that are important for patients may be monitored in vitro, e.g., perfusion for different hemodynamic conditions, as well as the graft's mechanical properties [7]. Such an approach minimizes the risk of failure during surgery.  
In the realm of medical diagnostics, the integration of various techniques, such as ultrasonography [8], 3D ultrasound [9], 4D ultrasound strain (4D-US) [10], and echocardiography, is gaining popularity [11]. Combining these methods with engineering approaches, such as computational fluid dynamics (CFD), has the potential to enhance analyses and contribute to patient diagnosis [12; 13; 14]. These approaches are commonly employed for predicting therapeutic outcomes in cases of aortic-wall-associated injuries, such as aneurysms or wall ruptures [15]. However, limited efforts have been directed toward leveraging ex vivo systems to faithfully replicate blood flow parameters and investigate flow and pressure conditions in an artificial environment [16]. Moreover, most investigated models primarily reconstruct laminar flow or focus on graft preservation solutions [17; 18]. Conversely, the pulsatile nature of blood hemodynamics in the cardiac system indicates the significant stretching of vessel walls, potentially leading to wall damage, especially in the presence of pre-existing conditions like atherosclerosis [19]. Furthermore, existing systems in the literature often only reconstruct laminar flow through artificial vessels or grafts [20], meaning that the relationship between elastic storage and the viscous dissipation of energy transmitted to vessel walls during systole in the cardiac cycle is not fully understood [21].  
This study aims to verify its accuracy in simulating the movement of artificial vessels vs. real vessels under changing cardiovascular parameters such as heartbeat, ejection fraction, and total peripheral resistance. The experiments were conducted with blood-like fluid that flows through two types of vessels: iliac arteries and different types of ePTFE vascular prostheses.  
The remainder of the manuscript is organized as follows: Section 2, Materials and Methods, outlines the experimental setup, the initial and boundary conditions, and the description of statistical analyses. Section 3, Results, presents the obtained results; Section 4, Discussion, contextualizes the findings within the current state-of-the-art; and Section 5, Conclusions, summarizes the paper.