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Backflow at the inlet of centrifugal blood pumps enhanced by geometrical features
KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Fluid Mechanics and Engineering Acoustics.ORCID iD: 0000-0002-8061-4146
KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Fluid Mechanics and Engineering Acoustics.ORCID iD: 0000-0003-0716-465x
ECMO Centre Karolinska, Pediatric Perioperative Medicine and Intensive Care, Karolinska University Hospital, Stockholm, Sweden; Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden.
KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Fluid Mechanics and Engineering Acoustics, Tillämpad strömningsmekanik.ORCID iD: 0000-0001-9976-8316
2024 (English)In: Physics of fluids, ISSN 1070-6631, E-ISSN 1089-7666, Vol. 36, no 3, article id 037127Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
AIP Publishing , 2024. Vol. 36, no 3, article id 037127
National Category
Fluid Mechanics and Acoustics
Identifiers
URN: urn:nbn:se:kth:diva-344580DOI: 10.1063/5.0186806ISI: 001182145900029Scopus ID: 2-s2.0-85187554456OAI: oai:DiVA.org:kth-344580DiVA, id: diva2:1845968
Note

QC 20240326

Available from: 2024-03-20 Created: 2024-03-20 Last updated: 2024-04-05Bibliographically approved
In thesis
1. Flow characterisation of drainage cannulae and centrifugal pumps used in extracorporeal membrane oxygenation: an experimental investigation
Open this publication in new window or tab >>Flow characterisation of drainage cannulae and centrifugal pumps used in extracorporeal membrane oxygenation: an experimental investigation
2024 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

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.

Abstract [sv]

Extrakorporal membranoxygenering (ECMO) ar en livräddande behandling vid akut andnings- och/eller hjartsvikt. Kärlåtkomst fås via en dräneringskanyl och blodet drivs vidare genom en membranlunga för gasutbyte (syresattning och koldioxidreduktion) av en centrifugalpump. Därefter återförs blodet till patienten via en returkanyl. Även om ECMO är livräddande kan behandlingen leda till blodkroppssönderfall (hemolys) och blodproppsrelaterade komplikationer som följd av de mekaniska påfrestningar blodet utsätts för. Den här avhandlingen fokuserar på ECMO-pumpar och kanylers födesmekanik. Syftet med arbetet var att förbättra den grundläggande föorståelsen för  flödesstrukturerna som skapas i de olika komponenterna samtpump prestanda under olika driftförhällanden. Dessa i huvudsakligen experimentella studier anvandes particle image velocimetry (kanyl flöde) och  lmning med höghastighetskamera (pumpkarakterisering). Kanyl flöde studeras för två kanyldesigner. Kanylen var placera i ett glasror med motsvarande diameter som nedre hålven. Sju centrifugalpumpar undersoktesavseende prestandakaraktärisering (flöde - tryck) förekomst av "backflöde" vid pumpinloppet. Den senare delen utfördes i kombinationmed numeriska  födesberäkningar för att identifiera underliggande orsaker till backflödet. Resultaten visade att kanyl utan sidohål genererade högre skjuvspänningar. Kanyl med sidohål dränerade mest genom sidohålen närmast sugkällan, vilketinte påverkades av kanylposition relativt "kärlvägg". Pumpar med hölje över impellerbladen utvecklade stabila recirkulationszoner längs pumpinloppetssidovägg. Dessa recirkulationsområden bildades från virvelstrukturer som skapadesperifert (sugsidan) runt impellern vilka sedan migrerade ovanpå höljetmot pumpinloppet. Detta arbete ökar förståelsen för den flödesdynamik gällande pumpar och kanylersom används för ECMO. Framför allt beskrivs hur pumpdesignen påverkar uppkomst av specifika flödesstrukturer som påverkar pumparnas effektivitet varifrån resultaten kan komma att användas för förbättring av blodpumpar foratt minska patientkomplikationer.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2024
Series
TRITA-SCI-FOU ; 2024:16
National Category
Fluid Mechanics and Acoustics
Research subject
Engineering Mechanics
Identifiers
urn:nbn:se:kth:diva-344831 (URN)978-91-8040-876-9 (ISBN)
Public defence
2024-04-18, Kollegiesalen, Brinellvägen 8, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
EU, European Research Council, 101045453
Available from: 2024-03-28 Created: 2024-03-28 Last updated: 2024-04-08Bibliographically approved

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Rorro, FedericoFiusco, FrancescoPrahl Wittberg, Lisa

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