Análise do escoamento pulsátil em fístula arteriovenosa com variação do ângulo de anastomose in vitro e in silico
Arteriovenous Fistula (AVF) is a direct connection between an arterial and a venous vessel used as a vascular access (AV) for patients undergoing Hemodialysis (HD). The preparation of AVF causes non-physiological conditions of blood flow, inducing disturbances in the flow such as recirculation zo...
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| Formato: | Dissertação |
| Idioma: | pt_BR |
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Universidade Federal do Rio Grande do Norte
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| Endereço do item: | https://repositorio.ufrn.br/handle/123456789/32369 |
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| Resumo: | Arteriovenous Fistula (AVF) is a direct connection between an arterial and a venous vessel used
as a vascular access (AV) for patients undergoing Hemodialysis (HD). The preparation of AVF
causes non-physiological conditions of blood flow, inducing disturbances in the flow such as
recirculation zones, stagnation points, high and low shear stress levels. These disorders are
associated with the development of pathologies that promote stenosis in the vessel, which can
compromise blood flow or even the loss of AVF. In order to analyze these disturbances with
the variation of the Anastomosis Angle (AA), an experimental bench was built to provide
pulsatile flow in AVF models. Pressure sensors MPU5050DP, digital flow sensors Type
Turbine, diaphragm pump S-60-12 and microprocessors Arduino UNO, Arduino Nano and
ESP32 were used. FAV were modeled with AA of 30 °, 45 °, 60 °, 75 °, 90 °, 105 °, 120 °, 135
° and 150 °. Piezometric Lines (LP) were drawn to indicate the energy dissipated in the
anastomosis. Using the Fused Deposition Modeling (FDM) technique, in vitro FAV models
were manufactured by 3D printing. Using block technique, in silico FAV models were
discretized into structured meshes. The pressure profile obtained on the bench proved to be
equivalent to the blood pressure pulse. No structural collapse and leakage of AVF in vitro was
observed for pressures between 0 to 45 kPa (337.53 mmHg). In in vitro AVF experiments, the
pressure differential decreased with increasing AA, varying from 12.0 kPa to 3.1 kPa. The
piezometric line indicates that the anastomosis is responsible for most of the dissipated energy.
Simulations in FAV in silico result in a velocity field with a stagnation point in the external
vein wall for FAV with AA of 30 °. Separation point and recirculation zone in the internal vein
wall for FAV with AA of 30 °, 45 °, 60 °, 75 °, 90 ° and 105 °, these disturbances are not
observed in FAV with AA of 120 °, 135 ° and 150 °. All AA have regions with high and low
levels of wall shear stress ( ). Regions with above 40 Pa are present at the anastomotic
junction and at the beginning of the venous segment. Shear stress below 0.4 Pa is present on
the internal wall of the vein and on the opposite side the anastomotic junction in the artery. It
is concluded that the FAV with AA of 120 ° and 135 ° provided lower values in the pressure
differential, lower values of energy dissipated in the anastomosis and smaller variations
between the pressure load and the piezometric line. FAVs with AA of 120 ° and 135 ° have
smaller areas with high and smaller areas with low . In this context, the AAs of 120 °,
135 ° and 150 ° appear to be the most favorable for the construction of the Arteriovenous
Fistula. |
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