Reproducibility of cardiovascular autonomic tests in diabetics with and without autonomic dysfunction and in normal controls

The present study evaluates the reproducibility of five cardiovascular reflex tests, deep breathing (DB), Valsalva maneuver (VM), sustained hand-grip (SHG), postural hypotension (PH) and lying to standing (LS) in normal subjects and in insulin dependent (type I) diabetic patients. The study was carried out in 10 normal subjects, in 10 diabetics with autonomic neuropathy and in 10 diabetics without autonomic neuropathy. The five cardiovascular reflex tests were performed five times on five consecutive days by the same investigator and in identical basal conditions. The intraindividual variability of DB, LS and VM was significantly reduced in diabetics with autonomic neuropathy compared with normal controls, but there was no difference between diabetics without neuropathy and normal controls. The intraindividual variability of PH was significantly increased in diabetics with autonomic neuropathy compared with diabetics without autonomic neuropathy and with normal controls. There was no difference among the three groups in the reproducibility of SHG. In normal subjects the intraindividual variability only exceptionally produced a shift from normal to abnormal values or vice versa; in diabetics with autonomic neuropathy this shift was more frequent.