Plethysmography
Plethysmography is a noninvasive test that measures and records the variations in volume and pressure as blood flows through the tissues.[10] In the diagnosis of varicose veins and CVD, either strain gauge plethysmography or air plethysmography is used to evaluate the function of the calf muscle, global venous reflux, and obstructions to venous outflow. These 2 types of plethysmography (ie, strain gauge or air plethysmography) involve exercise venous plethysmography, a measurement of the passive refill and drainage of the veins, and outflow plethysmography.[3] Gloviczki et al[3] notes that although venous plethysmography is not used as often for patients suffering from simple varicose veins, the test is used for patients who have more advanced stages of varicose veins and CVD and is considered complementary to venous duplex scanning when venous reflux or outflow obstruction is suspected but is not visualized with the duplex scan.