title: Recirculation during veno-venous extra-corporeal membrane oxygenation--a simulation study.
abstract: OBJECTIVE
  Veno-venous ECMO is indicated in reversible life-threatening respiratory failure without life-threatening circulatory failure. Recirculation of oxygenated blood in the ECMO circuit decreases efficiency of patient oxygen delivery but is difficult to measure. We seek to identify and quantify some of the factors responsible for recirculation in a simulation model and compare with clinical data.
  
  
  METHODS
  A closed-loop real-time simulation model of the cardiovascular system has been developed. ECMO is simulated with a fixed flow pump 0 to 5 l/min with various cannulation sites - 1) right atrium to inferior vena cava, 2) inferior vena cava to right atrium, and 3) superior+inferior vena cava to right atrium. Simulations are compared to data from a retrospective cohort of 11 consecutive adult veno-venous ECMO patients in our department.
  
  
  RESULTS
  Recirculation increases with increasing ECMO-flow, decreases with increasing cardiac output, and is highly dependent on choice of cannulation sites. A more peripheral drainage site decreases recirculation substantially.
  
  
  CONCLUSIONS
  Simulations suggest that recirculation is a significant clinical problem in veno-venous ECMO in agreement with clinical data. Due to the difficulties in measuring recirculation and interpretation of the venous oxygen saturation in the ECMO drainage blood, flow settings and cannula positioning should rather be optimized with help of arterial oxygenation parameters. Simulation may be useful in quantification and understanding of recirculation in VV-ECMO.
authors.affiliation: 2 Department of Medical Cellbiology/Section for Physiology, Biomedical Center, Uppsala University, Uppsala - Sweden.
authors.forename: Mikael
authors.initials: M
authors.lastname: Broman
authors.forename: Björn
authors.initials: B
authors.lastname: Frenckner
authors.forename: Anna
authors.initials: A
authors.lastname: Bjällmark
authors.forename: Michael
authors.initials: M
authors.lastname: Broomé
mesh_terms: D000328:Adult; D000368:Aged; D002404:Catheterization / Q000379:methods; D016208:Databases, Factual; D015199:Extracorporeal Membrane Oxygenation / Q000379:methods*; D005260:Female; D006801:Humans; D006976:Hypertension, Pulmonary / Q000628:therapy*; D008297:Male; D008875:Middle Aged; D008955:Models, Cardiovascular; D010100:Oxygen / Q000097:blood*; D011673:Pulsatile Flow; D012039:Regional Blood Flow / Q000502:physiology*; D012131:Respiratory Insufficiency / Q000628:therapy*; D012189:Retrospective Studies; D014682:Vena Cava, Inferior; D055815:Young Adult
chemical_list: D010100:Oxygen