Tube Collapse and Valve Closure in Ambulatory Venous Pressure Regulation: Studies with a Mechanical Model

Purpose:To determine the role of valve closure and column segmentation in ambulatory venous pressure regulation.Methods:Using a mechanical model consisting of a graduated adjustable valve and a collapsible tube, we studied the differential effects of valve closure and tube collapse on venous pressure regulation. By utilizing materials with differing wall properties for the infravalvular tube, the influence of wall property changes on tube function and pressure regulation was explored.Results:Valve closure, per se, does not cause venous pressure reduction. Collapse of the tube below the valve is the primary pressure regulatory mechanism. The nonlinear volume-pressure relationship that exists in infravalvular tubes confers significant buffering properties to the collapsible tube, which tends to retain a near-constant pressure for a wide range of ejection fractions, residual tube volumes, and valve leaks. Changes in tube wall property affect this buffering action, at both the low and high ends of the physiol...