title: The efficacy of a new portable sequential compression device (SCD Express) in preventing venous stasis.
abstract: OBJECTIVE
  It has been previously shown that the SCD Response Compression System, by sensing the postcompression refill time of the lower limbs, delivers more compression cycles over time, resulting in as much as a 76% increase in the total volume of blood expelled per hour. Extended indications for pneumatic compression have necessitated the introduction of portable devices. The aim of our study was to test the hemodynamic effectiveness of a new portable sequential compression system (the SCD Express), which has the ability to detect the individual refill time of the two lower limbs separately.
  
  
  METHODS
  This was an open, controlled trial with 30 normal volunteers. The new SCD Express was compared with the SCD Response Compression System in the supine and semirecumbent positions. The refilling time sensed by the device was compared with that determined from velocity recordings of the superficial femoral vein using duplex ultrasonography. Baseline and augmented flow velocity and volume flow, including the total volume of blood expelled per hour during compression with the SCD Express, were compared with those produced by the SCD Response compression system in the same volunteers and positions.
  
  
  RESULTS
  Both devices significantly increased venous flow velocity as much as 2.26 times baseline in supine position and 2.67 times baseline in semirecumbent position (all P < .001). There was a linear relationship between duplex ultrasonography-derived refill time and the SCD Express-derived refill time in both the supine (r = 0.39, P = .03) and semirecumbent (r = 0.71, P < .001) positions but not with the SCD Response. Refill time measured by the SCD Express device was significantly shorter and the cycle rate higher in comparison with the SCD Response in both positions. The single-cycle flow velocity and volume flow parameters generated by the two devices were similar in both positions. However, median (interquartile range) total volume of blood expelled per hour was slightly higher with the SCD Express device in the supine position (7206 mL/h [range, 5042-8437] vs 6712 mL/h [4941-10,676]; P = .85) and semirecumbent position (4588 mL/h [range, 3721-6252] vs 4262 mL/h [3520-5831]; P = .22). Peak volume of blood expelled per hour by the SCD Express device in the semirecumbent position was significantly increased by 10% in comparison with the SCD Response (P = .03).
  
  
  CONCLUSIONS
  Flow velocity and volume flow enhancement by the SCD Response and SCD Express were essentially similar. The latter, a portable device with optional battery power that detects the individual refill time of the lower limbs separately, is anticipated to be associated with improved overall compliance and therefore optimized thromboprophylaxis. Studies testing its potential for improved efficacy in preventing deep vein thrombosis are justified.
authors.affiliation: Department of Vascular Surgery, Faculty of Medicine, Imperial College, London, United Kingdom.
authors.forename: Stavros K
authors.initials: SK
authors.lastname: Kakkos
authors.forename: Maura
authors.initials: M
authors.lastname: Griffin
authors.forename: George
authors.initials: G
authors.lastname: Geroulakos
authors.forename: Andrew N
authors.initials: AN
authors.lastname: Nicolaides
mesh_terms: D000293:Adolescent; D000328:Adult; D001783:Blood Flow Velocity; D005260:Female; D005268:Femoral Vein / Q000000981:diagnostic imaging / Q000503:physiopathology*; D006801:Humans; D048228:Intermittent Pneumatic Compression Devices; D008297:Male; D008875:Middle Aged; D010991:Plethysmography; D019722:Sphygmomanometers; D018616:Ultrasonography, Doppler, Duplex; D014647:Varicose Ulcer / Q000517:prevention & control; D014689:Venous Insufficiency / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000517:prevention & control*; D014690:Venous Pressure