Neurogenic forearm vasodilatation during contralateral isometric exercise is attenuated in diabetes mellitus

The responses in heart rate, blood pressure and blood flow in the resting forearm during contralateral isometric handgrip were investigated together with the respiratory sinus arrhythmia (measured during standardized breathing frequency and depth), and the heart rate response to a Valsalva manoeuvre in 20 patients with insulin-dependent diabetes and clinical signs of a peripheral neuropathy. The respiratory sinus arrhythmia and the Valsalva ratio were attenuated in the patients compared to age-matched controls, indicating reduced vagal function. Also the responses to handgrip were reduced. The blood flow increase in the resting forearm upon handgrip was correlated with both the respiratory sinus arrhythmia and the Valsalva ratio, supporting neurogenic mediation of the flow response and indicating a reduction in sympathetic as well as vagal function in diabetes autonomic neuropathy.