Complexity analysis of beat-to-beat skin-surface laser-Doppler signals in diabetic subjects

• Complexity analysis applied to the beat-to-beat LDF waveform index
• Significant differences in ApEn among diabetic, prediabetic, and normoglycemic
• Partly attributed to the adaptability of the microcirculatory regulatory activities

MotivationsThis study performed skin-surface laser-Doppler flowmetry (LDF) measurements with the aim of verifying if complexity analysis applied to the beat-to-beat LDF waveform index can be used to discriminate diabetic, prediabetic, and normoglycemic subjects.MethodsSixty-six subjects were assigned to three age-matched groups according to the results of oral glucose tolerance tests. Beat-to-beat analysis was performed on the pulsatile LDF waveform to obtain the pulse-to-mean ratio (AD) and pulse width (PW), and then approximate-entropy (ApEn) values for their 20-minute index sequences were calculated to evaluate the signal complexity.ResultsAD and PW did not differ significantly among the three study groups. ApEn values of AD and PW were significantly larger and marginally larger, respectively, in the diabetic group than in the prediabetic and normoglycemic groups.ConclusionThese results indicate the presence of significant differences in ApEn indexes among diabetic, prediabetic, and normoglycemic subjects. The presence of increased complexity in the LDF index sequence may be partly attributed to the adaptability of the microcirculatory regulatory activities or the impairment of the homeostasis mechanism of microcirculatory-blood-flow perfusion. The present findings may be pertinent to the early detection of the diabetes-induced impairment of this perfusion.