## 1 Introduction
It is essential that the commercial system used to carry out the treatment be followed; regarding the handling of the components, extreme caution must be taken, and rigorous hygiene practices must be used to achieve a correct connection between the elements and carry out the procedure satisfactorily. Substitute therapies for patients suffering from chronic kidney disease are currently widely accepted, and comply with treatment. There have been multiple attempts made by different authors to improve these rudimentary peritoneal dialysis systems; numerous types of tubes have been used, such as Foley catheters, catheters with particular geometries in the tip mushroom and whistle, pipe connectors polyethene rubber, glass, stainless steel, a double-lumen tube of Rosenak. Most of the connection systems showed leakage of the liquid and, consequently, infections in the peritoneal cavity. The first peritoneal dialysis technique performed by nurses was one named \"Y\" with a tube-shaped bottle that was no connected to the connector but was connected to the rudimentary dialysis catheter [13; 14]. In the 1970s, plastic bags in the form of a container began to be used to transport dialysis fluid. Peritoneal dialysis became popular thanks to continuous ambulatory peritoneal dialysis (CAPD) by [PERSON] and [PERSON]. In these years, the machines' operation was rudimentary, although several items were used to provide infusion and drainage to patients. Meanwhile, CAPD was the preferred dialysis technique since it did not require prominent investment or lengthy training to understand the process; it is still used as renal replacement therapy [15]. Nowadays, in Mexico, the Baxter(r) and PISA(r) companies are two different brands dedicated to providing support to connection elements for peritoneal dialysis. Connection systems for CAPD should ensure the safety of the patient by decreasing the incidence of infections due unclean handling. The methodology used in this work is based on nephrology, and we developed a device through preliminary sketches. Through numerical simulations, we achieved a detailed design for developing a prototype in order to verify its functionality. Finally, prototypes with specific treatment characteristics were developed under medical-grade alloy and subjected to experimental tests. The materials used to carry out the present work are classified into three phases. The first one involves using the 3D prototyping technique in acrylonitrile butadiene styrene (ABS) to obtain a visual studio to establish improvements in the connectors. The second stage consists of manufacturing the detailed design in titanium \"Ti-6 Al-4V ELI\", which has been used as a material in prostheses and stents and has received acceptance from the health sector [16]. Finally, in the third stage, an experimental testbed is built to evaluate the connection thread areas in equipment from the different brands already mentioned. Figure 1 shows a flowchart considering the methodology and stages for the design of each connector. Our aim is to establish a connection in the systems for CAPD in Mexico, mixing the resources to perform the treatment. In the materials and methods section, we show the design of the connectors for PD. Using the finite element method (FEM), we generated a virtual model simulation to analyze the fluid behavior through the designed connectors. Nowadays, the 3D printing technique allows one to obtain preliminary prototypes to improve the design in pieces in order to obtain detailed designs for production. In this work, 3D models using ABS material were used for preliminary connection tests with the commercial systems. Once the tests were correctly completed, two prototypes using titanium alloy were made to complement the research through an observational study.