Cardiovascular responses to tilting in healthy and diabetic subjects.

Cardiovascular responses to tilting from supine to upright and back to supine were investigated by measuring heart rate (HR) and blood pressure (BP) continuously by non-invasive methods. Subjects were 20 healthy controls, 17 diabetic patients (DN) with normal test results for parasympathetic cardiac function and 21 diabetics (DA) with abnormal results. In control subjects, tilting up and tilting back maneuvers induced opposite changes in HR, systolic (SBP) and diastolic BP (DBP). The most obvious responses appeared during the first 30 sec after either maneuver. The best measurements to detect sympathetic vasoconstrictor abnormalities during tilting up were derived from the recovery curve that followed the immediate fall in SBP, abnormal in 6 DN and 14 DA patients, and from the increase in DBP after the maneuver, abnormal in 7 and 16, respectively. Tilting back induced comparatively larger cardiovascular responses. The SBP remained stable after 10 sec in the controls, but increased above normal limits in 7 DN and 20 DA patients. The DBP fell during the first 10 sec in controls, but not in 4 DN and 17 DA patients. Continuous monitoring of BP during tilting is a more sensitive test of autonomic function than classical BP measurements made at a few selected intervals. The results challenge the view that parasympathetic dysfunction precedes and occurs more frequently than sympathetic dysfunction.