Differences in skin blood flow oscillations between the plantar and dorsal foot in people with diabetes mellitus and peripheral neuropathy.

BACKGROUND: Understanding the differences in skin blood flow (SBF) on the plantar and dorsal foot in people with diabetes mellitus (DM) may help to assess the influence of diabetes and neuropathy on microvascular dysfunction and risks of diabetic foot ulcers in this population. However, there is no study comparing SBF oscillations between the plantar and dorsal foot in people with DM and peripheral neuropathy (PN).

OBJECTIVE: The objective of this study was to compare SBF oscillations between the plantar and dorsal foot in people with DM and PN and investigate the underlying mechanisms responsible for the differences.

METHODS: 18 people with Type 2 DM and PN and 8 healthy controls were recruited. Laser Doppler flowmetry (LDF) was used to measure SBF on the plantar and dorsal foot for 10 min when the subject was in the supine position. Wavelet analysis was used to quantify the relative amplitude of the characteristic frequency components of SBF oscillations. Sample entropy analysis was used to quantify the regularity degree of SBF oscillations.

RESULTS: People with DM and PN had a higher SBF on the plantar foot compared to the dorsal foot. The relative wavelet amplitudes of metabolic and myogenic frequency components on the plantar foot were respectively higher and lower compared to the dorsal foot. Sample entropy analysis showed that SBF on the plantar foot had a higher degree of regularity compared to the dorsal foot.

CONCLUSIONS: In people with DM and PN, higher SBF on the plantar foot is attributed to the metabolic and myogenic controls, and SBF on the plantar foot exhibits a higher degree of regularity compared to the dorsal foot. People with DM and PN also had higher plantar and dorsal SBF compared to the healthy controls. This study provides evidence to document differences in SBF of the plantar and dorsal foot in people with DM and PN.