Bottom line:  No evidence identified to support or refute use of sequential compression devices in hospitalized patients with active DVT.

Evidence summary resources (DynaMed, Joanna Briggs) do not mention these devices in relation to treating active deep vein thrombosis (DVT).

A PubMed search for these concepts:    “Venous Thrombosis/therapy”[Mesh] AND “intermittent pneumatic compression devices”[MeSH Terms] AND (“humans”[MeSH Terms] AND English[lang])

Only identified one small (n=24) pilot study in patients with venous thrombosis in the proximal leg who received catheter-directed thrombolytic medication (CDT).  Patients were randomized to either intermittent pneumatic compression device in addtition to CDT or CDT alone.
See:  Ogawa T, et al. J Vasc Surg. 2005 Nov;42(5):940-4. Intermittent pneumatic compression of the foot and calf improves the outcome of catheter-directed thrombolysis using low-dose urokinase in patients with acute proximal venous thrombosis of the leg.

More research would be needed to confirm findings, generalize findings to broader population, etc.