Assessment of Severity in Diabetic Autonomic Neuropathy Using Cumulative Linear Index of Higher Order Crossings

Cerebral autoregulation (CA) is the ability of brain to maintain cerebral blood flow (CBF) at constant level despite blood pressure changes. Autonomic neuropathy (AN) is a common complication in diabetes and might affect CA. To evaluate the relation between AN and CA in diabetics, higher order crossings (HOC) analysis of mean arterial blood pressure (MABP) and mean cerebral blood flow velocity (MCBFV) signals have been performed in 43 diabetics (25 mild AN and 18 severe AN) and 11 age-matched healthy control subjects. HOC was used to count the number of zero-crossings to evaluate the degree of oscillating. HOC values of MABP and MCBFV converge to the same constant limit with increasing filter order in healthy subjects. In diabetics, the process and limit of converge of HOC values of MABP and MCBFV were significantly different during tilt (linear index CUMUDIFF HOC, Healthy: 8.31±3.23, diabetics (severe AN): 10.63±2.77, p < 0.05). HOC difference between MABP and MCBFV reveals disturbance in CA. The linear index derived from HOC can be useful to evaluate autonomic neuropathy.