Pulse wave analysis using tone-entropy algorithm in people with and without foot complaints in a rural diabetes screening clinic

Peripheral arterial disease (PAD) affects 10-25% of people over the age of 55. It contributes to foot amputation, morbidity and mortality. Accurate and early diagnosis can lessen this public health burden. A current clinical measure of PAD such as the ankle brachial pressure index (ABPI) has low sensitivity and specificity for asymptomatic disease and calcified arteries especially in the diabetic population. Therefore, a new non-invasive evaluation method for lower limb vascularization has been investigated. Four groups of patients: non-diabetics and diabetics with and without foot problems and attending a diabetes complication screening clinic had their posterior tibial pulse velocity recorded. The pulse wave was segmented and inter-peak distances from 16-minute recordings identified. The tone-entropy algorithm for assessing pulse beat interval variation was applied to the data. Tone differentiated between non-diabetic and diabetes group with good foot health as well as for poor foot health. Entropy similarly was related to the level of foot health. A significant difference (p<0.05) was found between good foot health and poor foot health in the non-diabetes group. ABPI identified no significant differences between the four groups. The results suggest that the tone-entropy is a useful adjunct for screening for neuropathic-related foot problems that may be a risk indicator for peripheral arterial disease.