Automated Oscillometric Determination of the Ankle–Brachial Index Provides Accuracy Necessary for Office Practice

Peripheral arterial disease (PAD) remains the least recognized and treated form of atherosclerosis. It is present in 5 to 12 million Americans^1,2 but is diagnosed in less than half of these patients.³ The diagnosis of PAD has important prognostic implications and requires institution of therapeutic lifestyle changes and medical therapy to reduce cardiovascular morbidity and mortality. One important reason that the diagnosis of PAD is made infrequently is the lack of an easy-to-perform diagnostic test.

The ankle–brachial index (ABI) is the ratio of the systolic pressure at the ankle compared with the brachial artery pressure. When the ABI is ≤0.9, a diagnosis of PAD is made with up to a 90% accuracy.⁴ Measurement of the systolic pressure in both brachial arteries and pedal pulses is performed with a continuous-wave Doppler ultrasound. The greatest barrier to office-based ABI measurement is the time required for testing.⁵ A test that is automated, easy to perform, and less reliant on specialized skills may facilitate measurement of the ABI, increasing the diagnosis of PAD in susceptible populations. Oscillometric (automated) determination of blood pressure is approved for blood pressure measurement and is commonly available, reliable, and simple to use.⁶ Oscillometers measure the magnitude of the pressure vacillation in the limb as the cuff is deflated from suprasystolic pressures. As the pressure in the cuff decreases and approaches systolic blood pressure, oscillation rapidly increases and eventually reaches a peak after which decrease of the cuff pressure causes the oscillation to decrease. Systolic blood pressure is calculated when the oscillation increases rapidly and the diastolic pressure when the oscillation decreases rapidly. Accordingly, we compared the automated, oscillometric measurement of the ABI to the Doppler ultrasound measurement of the ABI to determine whether there is a simple, fast, and accurate method suitable for common use in the office.