title: Comparison of two intermittent pneumatic compression systems. A hemodynamic study.
abstract: OBJECTIVE
  Sequential leg compression has been previously shown to be superior to uniform compression. The aim of our study was to compare the hemodynamic effectiveness of the portable sequential compression device (SCD Express Compression System, Tyco Healthcare Group LP, Mansfield, MA, USA) with a rapid inflation device (VenaFlow, Aircast, Inc, Summit, NJ, USA). The former, by sensing venous refill time, commences compression when the calf veins are refilled.
  
  
  METHODS
  The two devices were tested in 12 normal volunteers in the semirecumbent position using duplex ultrasound. Baseline and augmented flow velocity and volume flow were measured at the level of the common femoral vein, above the saphenofemoral junction. Refilling time was determined from velocity recordings of the common femoral vein. Total and peak volume of blood expelled per hour during compression were calculated using flow data and the individual cycling rate.
  
  
  RESULTS
  Both devices increased venous flow velocity, up to 3.8 times the baseline (all P<0.001). Refill time of the rapid inflation device was shorter in comparison with the sequential compression device (15+/-2.2 vs 25+/-4 s; P<0.001), suggesting incomplete vein evacuation. The sequential compression device, by augmenting flow throughout a significantly longer compression period per cycle (10.9 s vs 6.3 s), expelled significantly more venous blood (121+/-68 vs 81+/-63 mL; P<0.001). Similarly, the total volume of blood expelled per hour with the sequential compression device was 100% higher than the rapid inflation device (9685+/-5426 vs 4853+/-3658 mL; P<0.001). Although peak velocity enhancement was higher with the rapid inflation device, flow augmentation (a product of average blood flow velocity) was comparable (669+/-367 vs 771+/-574 cm/s; P=0.223) with the sequential compression device, mainly because the rapid inflation device failed to maintain flow enhancement beyond the initial flow surge.
  
  
  CONCLUSIONS
  Sequential compression showed hemodynamic superiority compared to a rapid inflation device. This was enhanced further by the sensing of refill time, which resulted in more compression cycles over time. The relative efficacy of the two devices in deep vein thrombosis prevention should be tested in future studies.
authors.affiliation: Department of Vascular Surgery, Faculty of Medicine, Imperial College, London, UK.
authors.forename: S K
authors.initials: SK
authors.lastname: Kakkos
authors.forename: A N
authors.initials: AN
authors.lastname: Nicolaides
authors.forename: M
authors.initials: M
authors.lastname: Griffin
authors.forename: G
authors.initials: G
authors.lastname: Geroulakos
mesh_terms: D001783:Blood Flow Velocity / Q000502:physiology*; D004867:Equipment Design; D005260:Female; D005268:Femoral Vein / Q000000981:diagnostic imaging / Q000502:physiology*; D006801:Humans; D048228:Intermittent Pneumatic Compression Devices; D008297:Male; D010991:Plethysmography; D012016:Reference Values; D018616:Ultrasonography, Doppler, Duplex; D014690:Venous Pressure / Q000502:physiology