Sympathetic vascular function in patients with central dysautonomia.

This study used digital photoplethysmography (d-FPG) to investigate alterations in skin blood flow after exposure to cold as well as the post-prandial blood pressure pattern to assess how the sympathetic branch of autonomic nervous system (ANS) functioned in 31 patients with cerebral dysautonomia and in 27 healthy controls. d-FPG was carried out on all ten fingers in basal conditions and after exposure to ice-cold water (4-5 degrees C). Amplitude, crest time and inclination time were used to calculate the alterations induced by the cold pressor test. After a standard lunch blood pressure was monitored every 20 minutes using a fully automatic non-invasive sphygmanometer. Unlike the controls the amplitude of the photoplethysmographic wave increased in all patients except 2; crest time and inclination time decreased in all except 3; post-prandial diastolic and systolic blood pressure levels fell markedly in all but 3. Blood vessel smooth muscle tone is disturbed in patients with ANS failure because dysautonomia may permit the action of vasodilating substances to predominate. The post-prandial blood pressure pattern and the d-FPG used in conjunction with a cold pressor test are useful tools in the non-invasive investigation of ANS function.