title: Intra-aortic balloon pumping: does posture matter?
abstract: BACKGROUND
  The effect of the posture of semirecumbent patients on the hemodynamics and performance of intra-aortic balloon (IAB) were studied in vivo and in vitro.
  
  
  METHODS
  An IAB was inserted into a glass tube filled with saline, fully inflated and deflated using an intra-aortic balloon pump (IABP). Three successive cycles were filmed at 125 frames/s with the tube positioned at various angles between 0 degrees (horizontal) and 90 degrees (vertical). Pressure and flow were measured distal to both ends of the balloon. In parallel, coronary left anterior descending (LAD) flow velocity and aortic pressure were recorded in 6 patients using IABP, postcardiac surgery in the intensive care unit. Recordings were made when the patient was lying horizontally (recumbent) and when the patient's torso was inclined at 30 degrees to the horizontal (semirecumbent).
  
  
  RESULTS
  With the tube horizontal, the inflation was effectively uniform along the length of the balloon. At all other angles, the higher end of the balloon inflated first, and mean pressure and flow measured distal to the higher end of the balloon were less than those measured at 0 degrees . Mean aortic pressure and LAD flow decreased by 10 +/- 2% (P = 0.001) and 15 +/- 3% (P = 0.001), respectively, when the patient was semirecumbent compared to when the patient was recumbent.
  
  
  CONCLUSIONS
  The decreased mean aortic pressure and LAD flow velocity suggests that unless patients using IABP are required to be semirecumbent, it may be best to position them horizontally to gain the full benefits of balloon counter pulsation to the coronary circulation.
authors.affiliation: Brunel Institute for Bioengineering, Brunel University, Uxbridge, Middlesex, UK. ashraf.khir@brunel.ac.uk
authors.forename: Ashraf W
authors.initials: AW
authors.lastname: Khir
authors.forename: Susana
authors.initials: S
authors.lastname: Price
authors.forename: Colin
authors.initials: C
authors.lastname: Hale
authors.forename: David A
authors.initials: DA
authors.lastname: Young
authors.forename: Kim H
authors.initials: KH
authors.lastname: Parker
authors.forename: John R
authors.initials: JR
authors.lastname: Pepper
mesh_terms: D000368:Aged; D001011:Aorta / Q000503:physiopathology; D001783:Blood Flow Velocity / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology; D003331:Coronary Vessels / Q000000981:diagnostic imaging / Q000503:physiopathology*; D017548:Echocardiography, Transesophageal; D005260:Female; D006801:Humans; D007423:Intra-Aortic Balloon Pumping; D008297:Male; D011187:Posture / Q000502:physiology*