**1.2 Peripheral vascular disease (PVD)**

Microvascular and macrovascular diseases are the two types of diabetic vascular complications. Endothelial cellular dysfunction and smooth muscle abnormalities develop in diabetics as a result of a decrease in endothelium-derived vasodilators, resulting in constriction of blood arteries in the foot [11]. In diabetic patients, glucose levels in cells and tissues rise, stimulating glycolytic and polyol pathways in the peripheral nerve. Furthermore, protein modification with Advanced Glycation End-products (AGEs) and AGE accumulation causes structural (nerve fibre loss or demyelination and thickening of the endothelium's basement membrane in microvessel) and functional damage in small fibre nerves and microvessel. This situation is more vulnerable to diabetic patients' distal lower limb microvessel, which typically affects small arteries below the knee and within the foot, resulting in ischaemia at this site. This microcirculatory complication appears much earlier in the stage of prediabetes and worsens over time [12].

*Insight of the Pathophysiology of Diabetic Foot Ulcer DOI: http://dx.doi.org/10.5772/intechopen.108190*

Furthermore, macrovascular disease such as atherosclerosis causes blockage in major arteries due to thickening of blood capillaries and hardening of arteriolar walls, and it's also ended up with ischaemia. In DFU, determining the degree of ischaemia is critical. The pedal pulses (dorsalis pedis and posterior tibial arteries) must be carefully palpated. The dorsalis pedis artery is absent or significantly reduced in size in approximately 12% of the population, so a pulse may not be palpable. A cool foot with no palpable pedal pulses should be investigated further with non-invasive arterial Doppler ultrasonography of the lower limb. Beside these, other risk factors can also contribute into PVD such as age, smoking, hypertension, hyperlipidaemia, inflammatory markers and renal dysfunction [13].
