Estudo comparativo da vazão para novas seções transversais de um cateter duplo lúmen de aspiração de secreções pulmonares

Abstract

Endotracheal aspiration is a procedure for removing pulmonary secretions through a catheter under negative pressure through an aspirator. During the procedure, some signs/symptoms may occur, such as hypoxemia, risk of atelectasis, mucosal invagination, reduction of functional residual capacity (CRF), among others. Given the possibility of complications, a pulmonary secretion aspirator was developed at the Biomechanical Engineering Laboratory at the Federal University of Minas Gerais, requiring the development of a new breathing catheter, with two lumens. The objective of this work is to evaluate the efficiency of pulmonary respiration using two types of lumen with three different internal cross-sectional geometries: circular, semicircular and curve. The work was divided into stages: 1 - initial project for the study of new internal cross-sectional geometries of pulmonary secretion breathing catheters; 2- comparative analysis of leakage of new catheters and 12 Fr catheter (conventional catheter); 3- elaboration of models for numerical analysis for new geometries proposed in the ANSYS Fluent program; and 4- bench testing using the 12 Fr catheter and the circular double lumen catheter adopted for polyethylene glycol-based mucus mimicking aspiration sections. Polyethylene glycol solutions (viscoelastic fluid) in three different filters (semi-liquid, intermediate and semi-solid) were used for all analyzes, characterizing the mucosal respirator. As a result it was observed by flow tests that the relationship between shear stress and strain rate of mimicized mucus solutions is nonlinear, demonstrating similarity to non-Newtonian fluids. Suction pressures smaller than 400 mmHg using 12 Fr catheter over 10 seconds generates moderate removal of thick solutions and pressures below 350 mmHg over the same time interval do not generate removal of the same solution when using the circular double lumen catheter200 mm long in bench tests. Reducing the circular double lumen catheter length from 500 to 400 mm improved the effectiveness of secretion (flow) removal, while reducing the cross section of the circular double lumen catheter resulted in reduced flow. The semicircle double lumen catheter showed better flow results in numerical models compared to the circular and curved double lumen catheters using the thicker solution (SSS). Results obtained with the simulations in the Comsol program generated a better approximation of the flow results (mean velocity) as a function of pressure when compared to the numerical equation results for intermediate mimetic solutions using the 400 mm long 12 Fr catheter geometry. We concluded that it was not possible to validate by means of bench tests (experimental analysis), the numerical model used in numerical analysis in ANSYS Fluent for the 200 mm long circular catheter, requiring new models, studies and tests to obtain its validation. As a suggestion for future work, it is suggested that a semicircle catheter is designed, and to verify the flows obtained in bench tests, and that flow comparisons can be made in order to design a catheter with double lumens.