Is oscillometric ankle pressure reliable in leg vascular disease?

The objective of the study was to evaluate the validity of oscillometric sy stolic ankle pressure in symptomatic leg arterial occlusive disease. Ankle pressure measurements using oscillometric curves obtained using a standard 12-cm cuff with a specially designed device for signal processing were vali dated against the continuous wave (CW) Doppler technique. Thirty-four subje cts without signs or symptoms of peripheral vascular disease (68 legs) and 17 patients with leg ischaemia (85 legs) varying from moderate claudication to critical ischaemia were examined. The oscillometric curves were analyse d using several algorithms reported in the literature, based on the assumpt ion that maximum oscillations are recorded near mean arterial pressure. In normals, reasonable agreement between CW Doppler and oscillometric methods was seen. When an algorithm that determined the lowest cuff pressure at whi ch maximum oscillations occurred, and a characteristic ratio for systolic p ressure of 0.52 was used, the mean difference between CW Doppler and oscill ometry was 1.7 mmHg [range -19 to +27, limits of agreement (2 SD) 21.1 mmHg ]. In ischaemic legs, oscillometry overestimated systolic ankle pressure by a mean of 28.8 mmHg [range -126 to +65, limits of agreement 82.8 mmHg], Th e difference was more pronounced among patients with critical ischaemia com pared with claudicants, and also more evident among diabetics. The error of oscillometric pressure determination in subjects with leg arterial disease inversely increased with CW Doppler ankle pressure. In 39% of the recordin gs in legs with a CW Doppler systolic pressure below 100 mmHg, the oscillom etric mean arterial pressure was higher than the recorded CW Doppler systol ic pressure. In conclusion, the oscillometric method to determine systolic ankle pressure, based on the concept of maximum cuff oscillations occurring near mean arterial pressure, is not reliable in leg arterial disease, usua lly overestimating ankle pressure.