Giorgio Cattaneo

Compact intra-and extracorporeal oxygenator developments:

For patients with acute lung failure, mechanical ventilation entails the risk of lung tissue damage due to high oxygen pressure and concentration. Membrane oxygenation for one to two weeks can rest the lungs due to decreased ventilation parameters, representing a potential bridge to recovery, but implies the substantial risks of blood damage, plasma leakage and infection, which often have fatal results for patients. At the Helmholtz Institute in Aachen, two types of membrane oxygenators, which aim to overcome previous limits, are under development. Both present compact designs, reduced surface and priming volumes and easier handling. HEXMO is a miniaturized extracorporeal membrane oxygenator. The integration of a small rotary blood pump into the centre of the oxygenator reduces the amount of tubing and connectors in the system. Blood is convectively warmed by the pump motor housing, thus, the use of a heat-exchanger can be avoided. This compact design reduces surface and priming volume and allows better handling, especially in critical situations. A second development is the intravascular oxygenator HIMOX, which is inserted directly into the vena cava. Priming volume and blood contact surface are reduced, as well as infection risk and control needs for the patient. A new cross-flow fibre configuration is used for improving gas transfer within the limited space inside the vena cava. A microaxial blood pump is integrated into the device for compensating the pressure drop across the fibres and allowing venous return and physiological pressure in the organs proximal to the oxygenator.

Intravascular blood oxygenation using hollow fibers in a disk-shaped configuration : Experimental evaluation of the relationship between porosity and performance

Implantation of hollow fibers for blood oxygenation within a human vessel has been investigated for the last 15 years. Unfortunately, the combination of limited space inside the venous system and disadvantageous blood flow conditions has resulted until now in limited gas exchange performance of the investigated oxygenators. We are developing a highly integrated intravascular membrane oxygenator (HIMOX) characterized by a homogeneous disk-shaped fiber configuration. The main advantages are a larger fiber surface as well as favorable cross flow through the fibers compared with earlier designs. Fiber porosity represents an important constructive parameter and leads to a trade-off when dimensioning the bundles with the aim of maximum gas exchange at small anatomical size. Low porosity results in higher fiber surface as well as blood velocity. Both effects potentially enhance the gas exchange, but the associated increase of the pressure drop leads to a deformation of the fiber bundle and to a blood shunt. This fluid-structure interaction influences the gas exchange in a complex way. We investigated the influence of porosity on the gas exchange in the proposed fiber configuration in vitro. Bundle deformation was proven by comparing experimental data with a theoretical model. Highest oxygen exchange supplied by a single bundle was achieved at an intermediate porosity of 0.575. Moreover, specific oxygen exchange per fiber surface, which is an indicator of favorable flow conditions, increased with increasing fiber porosity. We achieved up to 450 ml O2 min–1 m–2, which is a promising result for intravascular membrane oxygenation.

A Novel Plasma-Based Fluid for Particle Image Velocimetry (PIV): In-Vitro Feasibility Study of Flow Diverter Effects in Aneurysm Model

Particle image velocimetry (PIV) is a commonly used method for in vitro investigation of fluid dynamics in biomedical devices, such as flow diverters for intracranial aneurysm treatment. Since it is limited to transparent blood substituting fluids like water-glycerol mixture, the influence of coagulation and platelet aggregation is neglected. We aimed at the development and the application of a modified platelet rich plasma as a new PIV fluid with blood-like rheological and coagulation properties. In standardized intracranial aneurysm silicone models, the effect of this new PIV plasma on the fluid dynamics before and after flow diverter implantation was evaluated and compared with water-glycerol measurements. The flow diverting effect was strongly dependent on the used fluid, with considerably lower velocities achieved using PIV plasma, despite the same starting viscosity of both fluids. Moreover, triggering coagulation of PIV plasma allowed for intra-aneurysmal clot formation. We presented the first in vitro PIV investigation using a non-Newtonian, clottable PIV plasma, demonstrating a mismatch to a standard PIV fluid and allowing for thrombus formation.