Abnormal Digital Pressure Measurements in Diabetic Neuropathic Foot Ulceration

Abstract

The diabetic neuropathic ulcer is typically slow to heal and recurrent. Macrovascular insufficiency is usually excluded as foot pulses are present and ankle:brachial pressure ratios are not decreased. These assessments cannot however exclude more distal vascular disease. Digital pressure measurements enable a reliable assessment of the distal peripheral vascular status to be made. The aim of this study was therefore to use toe pressures to assess the contribution of distal ischaemia in the pathogenesis of the neuropathic ulcer. Sixteen diabetic patients with recurrent neuropathic foot ulceration had their toe pressures compared to 10 neuropathic patients without a history of foot ulceration, 10 diabetic control subjects, and 11 normal subjects. Four non-diabetic patients with neuropathy and foot ulceration were also assessed. All subjects had ankle:brachial pressure indices > or = 1. Toe pressure was assessed using laser Doppler flowmetry to record the return of skin blood flow. The toe:brachial pressure index (TBI) was then calculated. The diabetic patients with a history of recurrent neuropathic ulceration, had the lowest mean TBI, 0.63 +/- 0.14 (SD), compared to the non-ulcerated diabetic neuropathy patients, the diabetic control subjects, and the normal subjects. 0.84 +/- 0.11, 0.82 +/- 0.1, and 0.81 +/- 0.07, p < 0.01, respectively. Three of the four non-diabetic patients with neuropathic foot ulceration also had an abnormally low TBI. Reduced toe pressure measurements are thus found to be associated with neuropathic foot ulceration. The contribution of distal ischaemia in the pathogenesis of the diabetic neuropathic foot ulcer needs to be evaluated.

An in-shoe laser Doppler sensor for assessing plantar blood flow in the diabetic foot

“…However, these ideas are in contradiction to findings from other studies (Stevens et al 1993, Netten et al 1996) that have demonstrated normal or elevated perfusion in nutritional capillaries.…”

“…The patients perception of the applied stimuli provides an indication of the extent of sensory neuropathy (Brand 1990, Lavery et al 1998) and can be useful as part of the overall assessment of the risk of ulceration. The presence and extent of peripheral vascular disease can be assessed using Doppler ultrasound (Hill 1987, Williams et al 1993, plethysmography or laser Doppler flowmetry (Stevens et al 1993), to determine systolic pressure at the ankle or great toe respectively.…”

“…The response is not quantifiable and the technique is sensitive to movement artefact. Despite these limitations it has been widely used to study the microcirculation and has previously been used to demonstrate microcirculatory abnormalities on the dorsum of the neuropathic diabetic foot (Stevens et al 1993).…”

“…As the rate of progression of atherosclerosis varies, throughout the peripheral vascular tree, both macrovascular and microvascular disease can exist at different levels of development . Consequently, an adequate dorsalis pedis or posterior tibial pulse is a poor indicator of the adequacy of the vessels within the foot (Stevens et al 1993). The prevalence of microvascular disease differs between type I and type II diabetics and it has been suggested that the pathogenesis of microvascular disease in the two forms is different (Jaap and Tooke 1995).…”

“…Ulceration is, however, considerably more prevalent in the neuropathic foot (Grunfeld 1992), occurring on the plantar surface at sites where tissue is subject to loading by bones such as the calcaneous and heads of the metatarsals ). In the ischaernic foot, the risk of ulceration can be estimated by assessing blood flow at the ankle by Doppler ultrasound and blood flux at the great toe by laser Doppler (Stevens et al 1993). When these techniques are applied to the neuropathic foot, a normal or elevated blood flow is frequently observed suggesting that the vascular supply is adequate, both to and within the foot.…”