Air is pumped into the cuff at high pressure. When the hand bulb is allowed to relax, the bulb re-expands. The outflow valve opens to allow refilling of the bulb. Each segment of the calf muscle pump works in the same way as the hand bulb of the sphygmomanometer. Inflow to a segment of deep vein is through intake valves from perforating veins as well as from the deep vein segment below.
Outflow is through an outflow valve to the deep vein segment above.
Squeezing of the vein segment occurs when muscle contraction increases the pressure within a fascial muscle compartment. Just like a sphygmomanometer, the calf muscle pump can achieve pumping pressures of several hundred mm Hg before valve failure occurs. Venous Pathology Venous pathology develops when venous return is impaired for any reason. Venous pathology can be deep, superficial, or mixed. Immediately after ambulation, the normal pressure within the veins of the lower extremity is extremely low because both the superficial and deep venous systems have been emptied by a normally functioning muscle pump.