WCUI Smith Chason Exit Assessment – Abdomen, Vascular, OB GYN Practice Test

An ABI compares the ankle’s systolic pressure to the arm’s systolic pressure to evaluate arterial blood flow to the legs. When the arteries are narrowed or blocked—as in peripheral arterial disease—the blood reaching the ankle is reduced, so the ankle pressure drops relative to the arm pressure. This lowers the ratio to below 0.9, which is why a value under 0.9 is taken as evidence of PAD. Normal ABI is around 1.0 (roughly equal pressures in ankle and arm). Very high values (above about 1.3–1.4) can indicate noncompressible, calcified arteries, which can mask disease rather than confirm it. Venous insufficiency affects the venous system and venous return, not the arterial inflow measured by the ABI, so it wouldn’t produce a low ABI. Thus, an ABI below 0.9 most directly points to peripheral arterial disease.