The development of a system to measure the effects of plantar foot pressure on the microcirculation of the foot

Abstract

An investigation into the effects of plantar foot pressure on the microcirculation of healthy subjects and patients with Rheumatoid Arthritis was carried out. In the light of no equipment available to carry out this study a new system was developed. A shoe device was built with a combined pressure/skin blood flow transducer embedded in a three-tier piston mechanism in the heel so that plantar foot pressure could be applied/removed and quantified. The skin blood flow transducer made contact with the skin and was able to collect data about the microcirculatory state of the skin.

The first system developed consisted of the laser Doppler Fluxmeter (Moor Instruments Ltd., UK) used to collect skin blood flow information and incorporating a strain gauge (Kyowa Electronic Instruments Co. Ltd., Japan) to quantify plantar foot pressure applied to the centre of the heel. This system was visually/sound synchronised and due to the time delay error it was modified. For the final system developed, the strain gauge was replaced with a custom-made Novel capacitative transducer (Novel, Germany) to quantify pressure. This allowed for the pressure system to be electronically synchronised in real time with the laser Doppler fluxmeter using an electronic synchronisation box. A number of studies were carried out to validate the systems.

The developed systems were used to: (a) investigate the effects of the venoarteriolar response in healthy subjects with regards to the effects of plantar foot pressure on skin blood flow. The study concluded that subject positioning (that is, supine or semi-weight bearing) has an effect on how the microcirculation of the skin reacts to applied pressure. Thus, studies investigating the effects of external pressure on skin blood flow must have their subjects in a position that is related to what is being studies; (b) investigate the effects of plantar foot pressure on skin blood flow in patients with Rheumatoid Arthritis. A healthy control group was compared with a cohort of patients with Rheumatoid Arthritis with no evidence of vasculitis. The study concluded that there were no significant differences between both groups.

A number of articles have been published from this thesis (see Appendix 14).