| 1. |
- Fiusco, Francesco, 1994-, et al.
(författare)
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Numerical and experimental investigation of a lighthouse tip drainage cannula used in extracorporeal membrane oxygenation
- 2023
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Ingår i: Artificial Organs. - : Wiley. - 0160-564X .- 1525-1594. ; 47:2, s. 330-341
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Tidskriftsartikel (refereegranskat)abstract
- Extracorporeal membrane oxygenation is a life saving therapy used in case of acute respiratory/circulatory failure. Exposure of blood to non-physiological surfaces and high shear stresses is related to hemolytic damage and platelet activation. An investigation of the flow structures developing in a conventional single-staged drainage cannula was performed with cross-validated computational fluid dynamics and particle image velocimetry. The aim was to quantify the variation in drainage performance and stress levels induced by different fluid models, hematocrit and vessel-to-cannula flow rate ratios. The results indicated that the 90◦ bends of the flow through the side holes created a recirculation zone potentially increasing the residence time and flow structures developing inside the cannula resembling a jet in a crossflow. The use of different hematocrits did not induce a considerable effect on the drainage performance, with the most proximal set of holes from the tip draining the largest fraction of fluid. However, different flow rate ratios altered the flow rate drained through the tip. The use of 2D data led to a 50% underestimation of shear rate levels, and a Reynolds-number scaling was applied to capture the velocity profiles and flow rates through the side holes.
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| 2. |
- Parker, Louis P., et al.
(författare)
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Venovenous extracorporeal membrane oxygenation drainage cannula performance : From generalized to patient-averaged vessel model
- 2024
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Ingår i: Physics of fluids. - : AIP Publishing. - 1070-6631 .- 1089-7666. ; 36:6
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Tidskriftsartikel (refereegranskat)abstract
- Venovenous extracorporeal membrane oxygenation is used for respiratory support in the most severe cases of acute respiratory distress syndrome. Blood is drained from the large veins, oxygenated in an artificial lung, and returned to the right atrium (RA). In this study, we have used large eddy simulations to simulate a single-stage “lighthouse” drainage cannula in a patient-averaged model of the large veins and RA, including the return cannula. We compared the results with previous experimental and numerical studies of these cannulas in idealized tube geometries. According to the simulations, wall proximity at the drainage holes and the presence of the return cannula greatly increased drainage through the tip (33% at 5 L/min). We then simulated a multi-stage device in the same patient-averaged model, showing similar recirculation performance across the range of extracorporeal membrane oxygenation (ECMO) flow rates compared to the lighthouse cannula. Mean and maximum time-averaged wall shear stress were slightly higher for the lighthouse design. At high ECMO flow rates, the multi-stage device developed a negative caval pressure, which may be a cause of drainage obstruction in a clinical environment. Finally, through calculation of the energy spectra and vorticity field, we observed ring-like vortices inside the cannula originating from the side holes, most prominent in the proximal position. Our work highlights the important differences between a patient-derived and simplified venous model, with the latter tending to underestimate tip drainage. We also draw attention to the different dynamics of single-stage and multistage drainage cannulas, which may guide clinical use.
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| 3. |
- Rorro, Federico, 1993-, et al.
(författare)
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Backflow at the inlet of centrifugal blood pumps enhanced by geometrical features
- 2024
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Ingår i: Physics of fluids. - : AIP Publishing. - 1070-6631 .- 1089-7666. ; 36:3
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Tidskriftsartikel (refereegranskat)abstract
- Extracorporeal life support (ECLS) includes life-saving support in severe acute cardiac and/or pulmonary failure. In the past 20 years, centrifugal pumps have become the primary choice to deliver the required blood flow. Pumps of various designs, with different approved operating ranges, are today available to clinicians. The use of centrifugal pumps in the low flow condition has been shown to increase hemolytic and thrombogenic risks of the treatment. Further, low flow operation has been associated with retrograde flow at the pump inlet. In this study, experimental and numerical methods have been applied to investigate the operating conditions and fluid dynamical mechanisms leading to reverse flow (or backflow) at the inlet. Reverse flow was predominantly observed in pumps having a top shroud covering the impeller blades, showing a relation between pump geometry and backflow. The shroud divides the pump volume above the impeller into two regions, separating the swirling reverse flow migrating toward the upper pump volute from the main flow, reducing the dissipation of the vortical structures, and allowing the swirling reverse flow to reach further in the pump inlet. At the inlet, backflow was observed as stable recirculation areas at the side of the pump inlet.
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| 4. |
- Rorro, Federico, 1993-, et al.
(författare)
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Backflow at the inlet of centrifugal pumps forextracorporeal life support in low flowconditions
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Extracorporeal life support (ECLS) are life-saving therapies used to supportcardiac and pulmonary functions in severe failure. In recent years the use ofcentrifugal pumps to drive the flow has become increasingly common. Severaldesigns are available on the market with different certified operating ranges.The use of centrifugal pumps in low flow conditions has been shown to increasehaemolytic and thrombogenic risks and been linked to the appearance of aretrograde flow at the inlet pipe. In this study, an experimental investigation ofseveral pump designs has been performed to assess the occurrence of backflowacross different operating conditions. Numerical simulations have been carriedout for a geometry and flow case showing backflow to highlight flow structuresassociated to it. The results showed that covered pumps were more likely toexhibit backflow in low flow conditions. The appearance of backflow was linkedto the development of vortical structures rising from the impeller blade tip andrising, being trapped between the shroud and the pump housing.
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| 5. |
- Rorro, Federico, 1993-
(författare)
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Flow characterisation of drainage cannulae and centrifugal pumps used in extracorporeal membrane oxygenation: an experimental investigation
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Extracorporeal membrane oxygenation (ECMO) is a life-saving treatment for acute respiratory and/or circulatory failure. Typically driven by a centrifugal pump, blood is drained from the patient via one drainage cannula, oxygenated by a membrane lung and returned to the patient via the return cannula. Although lifesaving, ECMO is associated with thromboembolic and haemolytic complications in part related to the mechanical stresses experienced by blood in the ECMO circuit. This thesis focuses on the fluid dynamics of ECMO pumps and cannulae with the aim to improve the fundamental understanding of flow structures and overall performance of the respective components during different operating conditions. Experimental studies were conducted with particle image velocimetry (cannula flows) and high speed video recordings (pump characterisation, complex geometry). The dynamics of an isolated drainage cannula placed in a glasstube with dimensions similar to the inferior vena cava were studied considering two different cannula tip designs. Seven centrifugal pumps were investigated to evaluate pump mechanical performance and the development, for low flow rates, of backflow at the pump inlet. The dynamics leading to backflow was investigated together with numerical simulations. The results showed higher shear stress levels in a blunt cannula compared to a lighthouse tip cannula. The latter drained the highest volume fraction through the most proximal side-holes and not the tip. Cannula position relative to the wall did not alter these results. In pumps with a shroud over the impeller blades stable recirculation zones were observed on the sides of the pump inlet. These recirculating regions were formed by vortical structures detaching from the peripheral (suction) side of impeller blades and migrating over the shroud towards the pump inlet. This work increases the fluid dynamical understanding of centrifugal pumps and cannulae used for ECMO. In particular, data on detailed design features influencing inherent pump recirculation are revealed which may impact futurepump designs. Such changes have the potential to significantly reduce patient complications.
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| 6. |
- Rorro, Federico, 1993-, et al.
(författare)
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Performance comparison of centered and tilted blunt and lighthouse tip cannulae for drainagein extracorporeal life support
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Introduction: Extracorporeal membrane oxygenation is a lifesaving treatment for patients with refractory acute respiratory, circulatory, or combined cardiopulmonary failure. The patient is cannulated with one or two cannulae for drainage and reinfusion of blood. Blood is drained from the patient, pumped through a membrane lung for oxygenation and then returned back to the patient.Efficacy of the treatment depends on correct cannula positioning and interactions between drainage and reinfusion cannula.Methods: An experimental setup was built to study the isolated drainage performance of a 24 Fr rigid model of a blunt and lighthouse tip cannula both when centered and when tilted towards the vessel wall. Particle image velocimetry was used to investigate the flow field with water as the fluid medium.Results: The blunt tip cannula induced higher levels of shear stresses for similar flow configuration, when compared to the lighthouse design. Moreover, in the lighthouse design, side-holes furthest from the tip (proximal holes) drained the highest fraction of the total flow. Results did not change significantly when the cannula was tilted towards the vessel wall.
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