The validity and reliability of automated and manually measured toe blood pressure in ischemic legs of diabetic patients

Abstract

Objectives: Modern guidelines for evaluation of leg ischemia in patients with diabetes and foot ulcer recommend toe blood pressure (TBP) measurements rather than the often unreliable ankle blood pressure (ABP). A drawback with TBP is the complicated measurement procedure, unsuitable the outpatient clinic. The aim of this study was to evaluate the validity of a new automatic TBP device (PresTo, Moor Instruments Ltd) developed for use outside vascular laboratories.

Design: Cross-sectional comparative study.

Methods: Twenty-three legs in 16 consecutively included diabetic patients with PAD were examined. TBP was measured three times with 2 min in-between. Three examiners read the obtained graphs (n=69), which were analyzed for variability over time and between examiners. These results were compared with those obtained from an automated TBP device.

Results: The mean TBP was 50.9 mm Hg (SD 10.9) when read by examiners compared to 56.4 mm Hg (SD 12.6) when automatically assessed. The 2-min variability was 4.9 mm Hg (SD) for visual readings and 8.1 mm Hg for automatic measurements. The short, long term and examiner dependent variability of visually read TBP ranged from 3.9 to 9.6% of the values. In patients with TBP <45 mm Hg the difference between automatic and visual assessments was small.

Conclusion: The automatic TBP device is reliable for measuring low pressures and thus for exclusion of critical limb ischemia in patients with diabetes. After algorithm adjustment the device's reliability appears to be acceptable in the entire spectrum of TBP values. TBP appears to have less inter and intraobserver variability than what is reported for ABP.