The efficacy of the new SCD Response Compression System in the prevention of venous stasis

Objective: The current commercially available sequential intermittent pneum atic compression device used for the prevention of deep venous thrombosis h as a constant cycle of 11 seconds' compression and 60 seconds' deflation. T his deflation period ensures that the veins are filled before the subsequen t cycle begins. It has been suggested that in some positions (eg, semirecum bent or sitting) and with different patients (eg, those with venous reflux) , refilling of the veins may occur much earlier than 60 seconds, and thus a more frequent cycle may be more effective in expelling blood proximally. T he aim of the study was to test the effectiveness of a new sequential compr ession system (the SCD Response Compression System), which has the ability to detect the change in the venous volume and to respond by initiating the subsequent cycle when the veins are substantially full. Methods: In an open controlled trial at an academic vascular laboratory the SCD Response Compression System was tested against the existing SCD Sequel Compression System in 12 healthy volunteers who were in supine, semirecumb ent, and sitting positions. The refilling time sensed by the device was com pared with that determined front recordings of femoral vein flow velocity b y the use of duplex ultrasound scan. The total volume of blood expelled per hour during compression was compared with that produced by the existing SC D system in the same volunteers and positions. Results: The refilling time determined automatically by the SCD Response Co mpression System varied from 24 to 60 seconds in the subjects tested, demon strating individual patient variation. The refilling time (mean +/- SD) in the sitting position was 40.6 +/- 10.0 seconds, which was significantly lon ger (P < .001) than that measured in the supine and semirecumbent positions , 33.8 +/- 4.1 and 35.6 +/- 4.9 seconds, respectively. There was a linear r elationship between the duplex scan-derived refill time (mean of 6 readings per leg) and the SCD Response device-derived refill time (r = 0.85, P < .0 01). The total volume of blood (mean +/- SD) expelled per hour by the exist ing SCD Sequel device in the supine, semirecumbent, and sitting positions w as 2.23 +/- 0.90 L/h, 2.47 +/- 0.86 L/h, and 3.28 +/- 1.24 L/h, respectivel y. The SCD Response device increased the volume expelled to 3.92 +/- 1.60 L /h or a 76% increase (P = .001) in the supine position, to 3.95 +/- 1.55 L/ h or a 59% increase (P = .001) in the semirecumbent position, and to 3.97 /- 1.42 L/h or a 21% increase (P = .026) in the sitting position. Conclusions: By achieving more appropriately timed compression cycles over time, the new SCD Response System is effective in preventing venous stasis by means of a new method that improves on the clinically documented effecti veness of the existing SCD system. Further studies testing its potential fo r improved efficacy in preventing deep venous thrombosis are justified.