What type of error occurs when measuring ABI in an incompressible arterial vessel?

When measuring the Ankle-Brachial Index (ABI) in an incompressible arterial vessel, a false high reading occurs. This situation arises because the blood pressure measurement obtained at the ankle may reflect the high-pressure state of the arterial system due to calcification or stiffening of the vessels. In such cases, even if there is significant peripheral arterial disease present, the ankle pressure might appear artificially elevated compared to the brachial pressure.

In cases of incompressibility, the expected physiological relationship between ankle and brachial pressures is disrupted. The ABI relies on the assumption that the ankle pressure should be lower than or equal to the brachial pressure in healthy or pathological conditions involving significant occlusion. Therefore, when testing is performed on an incompressible vessel and a false high reading is obtained, it can lead to misinterpretation of the patient's vascular status, potentially underestimating the severity of vascular problems.

The other potential outcomes—false low readings, no readings, or accurate readings—do not apply in the context of incompressible vessels. False low readings typically occur with improperly placed cuffs or technical errors, no readings would suggest an inability to capture any blood pressure at all, and accurate readings assume a normal arterial condition without the complication