A PLETHYSMOGRAPHIC STUDY OF THE HUMAN SKIN UNDER VARIOUS ENVIRONMENTAL CONDITIONS

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Abstract
By means of reflexion photoelectric plethysmograph (RPPG), vascular activities of various areas of the human body surface were observed in relation to various external and internal environmental conditions. Changes in various environmental conditions, namely, from high to low environmental temperature, from summer to winter, from a strained mental state to a relaxed one, etc., gave rise to parallel changes in RPPG patterns. Vascular activity could be classified into 4 types from view of changes in RPPG pattern of the thumb. Vascular activities of various areas of the human body surface were similar to each other in certain conditions but were not in other conditions. Vascular activity in an imbalanced state of the autonomic nervous system was studied by means of Mecholyl test and CO2 inhalation test, and relationship between pattern-changes of RPPG and the activity level of the central autonomic nervous system was discussed.