Digital pulse plethysmography--a tool for investigating vasoactive substances.

Plethysmographic investigations have been in use for at least a hundred years for the measurement of pharmacological actions in humans. Finger plethysmography was used particularly in the investigation of the vasodilating effect of organic nitrates. It has also proved valuable in determining the relative bioavailability of representatives of this class of drugs. This paper deals with personal experience in the use of this method for the investigation of older and newer organic nitrates. The apparatus that was developed to enable electronic data processing of the plethysmographic signals is described. The effects of other pharmacological interventions on finger volume pulse are also discussed, and the finger plethysmographic investigation of vasodilating substances that belong to classes of drugs other than organic nitrates is presented. The possibilities and limits of the method are discussed.