Kakkos SK, Szendro G, Griffin M Daskalopoulou SS, Nicolaides AN.
The efficacy of the new SCD response compression system in the prevention of
venous stasis.
J Vasc Surg 2000 Nov;32(5):932-40

Irvine Laboratory for Cardiovascular Investigation and Research, Department of
Vascular Surgery, Imperial College School of Medicine, London. UK.
s.kakkos@ic.ac.uk

OBJECTIVE: The current commercially available sequential intermittent pneumatic
compression device used for the prevention of deep venous thrombosis has a
constant cycle of 11 seconds' compression and 60 seconds' deflation. This
deflation period ensures that the veins are filled before the subsequent cycle
begins. It has been suggested that in some positions (eg, semirecumbent 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. The aim of the study was to
test the effectiveness of a new sequential compression 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,
semirecumbent, and sitting positions. The refilling time sensed by the device was
compared with that determined from recordings of femoral vein flow velocity by
the use of duplex ultrasound scan. The total volume of blood expelled per hour
during compression was compared with that produced by the existing SCD system in
the same volunteers and positions. RESULTS: The refilling time determined
automatically by the SCD Response Compression System varied from 24 to 60 seconds
in the subjects tested, demonstrating individual patient variation. The refilling
time (mean +/- SD) in the sitting position was 40.6 +/- 10. 0 seconds, which was
significantly longer (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 relationship 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 <.
001). The total volume of blood (mean +/- SD) expelled per hour by the existing
SCD Sequel device in the supine, semirecumbent, and sitting positions was 2.23
+/- 0.90 L/h, 2.47 +/- 0.86 L/h, and 3.28 +/- 1.24 L/h, respectively. 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 3.93 +/- 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 effectiveness of the existing SCD system. Further
studies testing its potential for improved efficacy in preventing deep venous
thrombosis are justified.