A novel approach to mechanical prophylaxis: calf impulse technology mimics natural ambulation more effectively than sequential calf compression.

Warwick, David J; Dewbury, Keith

BACKGROUND The risk of thrombosis can be reduced by mechanical compression, but the optimal device is unknown. OBJECTIVES To record the effect of natural ambulation on deep venous flow, providing a reference for evaluating the efficacy of mechanical compression systems, assuming that ambulation is the gold standard against which such systems should be compared; and to compare the hemodynamic effect of the A-V Impulse System CalfPad garment (A-VI) (Orthofix Vascular Novamedix, United Kingdom) with the SCD Express calf compression garment (SCD) (Covidien, USA). METHODS Twelve healthy volunteers were recruited and randomly assigned to either A-VI or SCD in a two-device, two-period crossover design. Peak femoral velocity (PFV) was calculated using custom ultrasound software and compared with baseline values. Ultrasound images were recorded. RESULTS A-VI augmented the mean (± SD) PFV to 59.79±29.07 cm/s compared with 22.86±5.73 cm/s for SCD. The actual percentage increase from baseline was approximately five times greater for A-VI (mean increase 385%±260%) than SCD (mean increase 81%±53%). Using an analysis of covariance model, with baseline fitted as a covariate, a highly statistically significant difference in favour of A-VI was detected (P=0.0002). Least square (adjusted) means (±95% CIs) were 37.24 cm/s (21.39 cm/s to 64.84 cm/s) for A-VI and 6.71 cm/s (3.86 cm/s to 11.69 cm/s) for SCD, representing more than fivefold greater improvement in PFV from rest with the A-VI device than with the SCD device. CONCLUSION Pulsatile impulse calf compression (A-VI) more closely mimics PFV of normal ambulation than slow-squeeze sequential compression (SCD). Pulsatile calf compression may provide superior protection against thrombosis in immobile patients.