To test the hypothesis that vasomotion, the rhythmic contraction exhibited by small arteries and arterioles, is impaired in diabetic subjects compared with healthy control subjects.
We mathematically modeled the oscillations in laser Doppler microvascular measurements taken from the pulpar surface of the index finger in 20 healthy control subjects and 20 age-matched diabetic subjects (8 with type I and 12 with type II diabetes). The mean duration of diabetes was 17.1 ± 2.3 years, and mean HbA1c was 9.1 ± 0.4%. Blood flow was measured for 5 min as subjects rested quietly in a closed room. Fast Fourier transformation was performed to provide the frequency power spectrum of each recording. Amplitude of vasomotion was correlated with six quantitative measurements of neuropathy.
Diabetic subjects had impaired low-frequency oscillation vasomotion in 75% of age-matched patients (15 of 20 patients), with mean amplitudes of 24.9 ± 6.4 vs. 129.0 ± 33.2 (P < 0.0039). Of six somatic and autonomic neuropathy variables, only the warm thermal sensory threshold correlated significantly with the mean amplitude of vasomotion (r = −0.75, P < 0.0009).
Patterns of peripheral vasomotion are clearly disordered in diabetes. The loss of low-frequency oscillations observed here suggests a peripheral vascular abnormality that extends past the capillary network to arterial vessels. It is uncertain whether the accompanying small unmyelinated nerve C-fiber dysfunction is a cause or consequence of the impaired microvascular function. Measurement of vasomotion may prove useful as a novel test for peripheral neurovascular function.