Ambulatory venous pressure measurements: new parameters derived from a mathematic hemodynamic model.

Purpose: The mechanism of venous pressure decrease during exercise still remains unclear. To explore the components involved with the regulation of ambulatory venous pressure, we reinvestigated the pattern of pressure decrease during tiptoe exercise with a newly developed mathematic model.

Methods: Seventeen healthy limbs of 16 volunteers (normal group) and 35 limbs of 33 patients with signs and symptoms of chronic venous insufficiency were studied. Seventeen limbs had superficial venous incompetence (SVI), and 18 showed deep venous incompetence with or without concomitant superficial venous reflux. All subjects were examined with ambulatory venous pressure measurements. As parameters obtained from serial phasic changes in pressure during tiptoe movements, the pressure reduction fraction per step (decreasing component) and the pressure increase per step (increasing component) were calculated with application of the mathematic hemodynamic model and assessed comparatively in the three groups with different types of reflux (normal, SVI, and deep venous incompetence group).

Results: The pressure increase per step was significantly different in each of the three groups (P <.0001, with analysis of variance), whereas no apparent difference was seen in the mean pressure reduction fraction per step among the groups. With addition of the inflation of ankle cuff, the value of pressure increase in limbs with SVI was significantly reduced (P =.0004, with Wilcoxon signed rank test), although no changes were seen in the pressure reduction fraction in each group.

Conclusion: Our results indicate that the pressure reduction fraction, representing calf muscle pump function, is independent of the existence or site of valve incompetence. On the other hand, the pressure increase, corresponding to the degree of reflux during exercise, correlates strongly with the severity of venous insufficiency. The theoretic model can separate the two components responsible for ambulatory venous pressure changes, calf muscle pump function and venous reflux, and provide better understanding of venous hemodynamics.