The effects of different accumulated pressure-time integral stimuli on plantar blood flow in people with diabetes mellitus

Abstract

Background: Exercise, especially weight-bearing exercise (e.g. walking), may affect plantar tissue viability due to prolonged repetitive high vertical and high shear pressure stimulus on the plantar tissue, and further induce development of diabetic foot ulcers (DFUs). This study aimed to investigate the effects of different accumulated pressure-time integral (APTI) stimuli induced by walking on plantar skin blood flow (SBF) responses in people with diabetes mellitus (DM).

Methods: A repeated measures design was used in this study. Two walking protocols (low APTI (73,000 kPa·s) and high APTI (73,000 × 1.5 kPa·s)) were randomly assigned to ten people with DM and twenty people without DM. The ratio of SBF measured by laser Doppler flowmetry after walking to that before (normalized SBF) was used to express the SBF responses.

Results: After low APTI, plantar SBF of people with DM showed a similar response to people without DM (P = 0.91). However, after high APTI, people with DM had a significantly lower plantar SBF compared to people without DM (P < 0.05). In people with DM, plantar SBF in the first 2 min after both APTI stimuli significantly decreased compared to plantar SBF before walking (P < 0.05).

Conclusions: People with DM had a normal SBF response after low APTI walking but had an impaired SBF response after high APTI walking, which suggests that they should avoid weight-bearing physical activity with intensity more than 73,000 kPa·s and should rest for more than 2 min after weight-bearing physical activity to allow a full vasodilatory response to reduce risk of DFUs.

Keywords: Accumulated pressure-time integral; Diabetic foot ulcers; Microcirculation; Plantar skin blood flow; Weight-bearing exercise.

Fig. 1

Illustration of plantar skin blood flow before and after different APTI stimuli in people with DM and healthy participants without DM (mean and standard deviation clouds, the black line is mean and the shaded area is standard deviation; Unit: Perfusion unit (Pu)). a People with DM after the low APTI stimulus; b People with DM after the high APTI stimulus; c Healthy participants after the low APTI stimulus; d Healthy participants after the high APTI stimulus

Fig. 2

Results of normalized skin blood flow between the high and low APTI stimuli in each group (mean with 95%CI). The symbol “*” indicates a significant difference between each group (P < 0.05). Normalized skin blood flow means the ratio of skin blood flow after walking to that before walking

Fig. 3

Results of skin blood flow during recovery and baseline in each group (mean with 95%CI). a Skin blood flow of DM group after the low APTI stimulus; b Skin blood flow of DM group after the high APTI stimulus; c Skin blood flow of healthy group after the low APTI stimulus; d Skin blood flow of healthy group after the high APTI stimulus. The symbol “*” indicates a significant difference between this period during recovery and baseline periods (P < 0.05)