Abstracts Category : Other

Vascular risk profiling and exercise therapy for diabetic foot complications

by Sean Michael Lanting

Research Doctorate - Doctor of Philosophy (PhD) Diabetes is associated with a life-time risk of developing a foot ulcer of between 15-25% and is the leading cause of non-traumatic lower limb amputations. With prevalence of diabetes rising globally, the contribution of diabetes-related foot complications to morbidity and mortality associated with the disease is significant. This thesis considers the relationship between clinical measures of lower limb macro- and microvascular vascular function and likelihood of diabetic foot complications including foot ulcer and amputation. In addition, the role of exercise therapy for treatment of diabetes-related vascular pathology is investigated. Firstly, to explore the role of lower limb vascular assessment in establishing risk of diabetes related foot complications, two separate cohort investigations in community based populations with diabetes were conducted. The first study investigated the relationship between measurements of large (ankle-brachial index [ABI] and continuous wave Doppler [CWD]) and small arterial function (toe-brachial index [TBI]) in the lower limb and history of diabetes-related foot complications. This study revealed that a low TBI (0.6) was associated with an eight-fold increase in likelihood of previous foot complications. Large arterial screening measures did not demonstrate such clinical risk profiling. The aim of the second cohort study was to investigate possible relationships between the parameters of cutaneous microvascular reactivity (CMR) at the hallux, measured via post-occlusive reactive hyperaemia using laser-Doppler, and their relationship with current or previous foot complications in people with diabetes. The results of this investigation demonstrated that for every increase in unit of the parameter of time to peak flux following occlusion (TtPeak), the likelihood of current or previous foot complication was increased by 2%. This supports an independent role of microvascular disease in development and subsequent outcomes of foot ulceration. To investigate the impact of exercise therapy on microvascular function (with a view to it being a possible treatment for cutaneous microvascular disease) a systematic review with meta-analysis of pooled data of controlled trials investigating the effect of exercise therapy on CMR in older adults was undertaken. The review was limited by number and quality of controlled trials, though most revealed a tendency for improved CMR following the intervention. Subsequent meta-analysis of the pooled results showed a moderate significant improvement to CMR following moderate-intensity exercise training in older adults. This systematic review also revealed the lack of investigation into the effect of exercise training on CMR in diabetic populations with only two of the trials using a diabetes cohort. As a result of the promise demonstrated by exercise training in our systematic review as a mechanism for improving CMR, coupled with the paucity of evidence in diabetes cohorts we undertook an additionalAdvisors/Committee Members: University of Newcastle. Faculty of Health & Medicine, School of Health Sciences.