An apparatus for promoting vascular circulation, including a garment configured to at least partially surround an anatomical structure of a patient. A compression element is coupled to the garment and configured to compress at least a portion of the anatomical structure when the compression element is actuated. A controller is configured to selectively actuate the compression element over a plurality of cycles. Each cycle has an actuated time during which the compression element is arranged to exert a first pressure and an unactuated time during which the compression element is arranged to exert a second pressure different than the first pressure, and the controller is configured to use a random value in determining the deflated time of one or more of the cycles.