Kamm R, Butcher R, Froelich J, Johnson M, Salzman E, Shapiro A, Strauss HW.
Optimisation of indices of external pneumatic compression for prophylaxis against
deep vein thrombosis : radio nuclide gated imaging studies.
Cardiovasc Res 1986 Aug;20(8):588-96

The amount and rate of blood expelled with different modes of intermittent
external pneumatic compression applied to the lower leg were studied on a
regional basis in a series of experiments on healthy human volunteers.
Radionuclide imaging of the labelled blood pool, with acquisition of counts
synchronised to the pressurisation cycle, provided data on regional blood volumes
in the leg in relation to time. To determine the changes in blood volume of the
lower leg resulting from external pneumatic compression labelled red blood cell
counts were determined during 10 different types of compression cycle. Since
venous stasis is considered to be a major cause of venous thrombosis the red
blood cell counts were used to calculate regional values of the fraction of blood
ejected as well as comparative indices proportional to regional flow rate,
regional velocity, and regional wall shear stress. All these indices should be
maximised for optimal prophylaxis against deep vein thrombosis. The four
compartment cuff in each compression mode applied a mean pressure of 45 mm Hg,
but different combinations of values were used for intercompartmental pressure
gradation (delta p) and for intercompartmental time sequencing to the onset of
compression (delta t). Uniform compression (delta p = 0; delta t = 0) was
substantially inferior to cycles with gradation and sequencing. The optimal
values of delta p were in the range 5-10 mm Hg and of delta t in the range 0-0.5
seconds.