Noninvasive optical techniques of photopulse plethysmography (PPG) and laser Doppler velocimetry (LDV) have been used to identify regional variations in the basal skin blood flow of humans. The procedures assess either the volume (PPG) or the volume-velocity product (LDV) of cutaneous blood vessel perfusion. Fifty-two anatomic positions have been studied in 10 normal subjects resting horizontally. The mean perfusion levels were ranked to reveal the variations in cutaneous blood flow as a function of body site. Groups of data were collected into cohorts and average perfusion values for the subjects within each cohort were compared by the Newman-Keuls multiple comparison test. Most transparently, the results reveal a collection of regions (fingers, palms, face, ears) for which cutaneous perfusion is much higher than all other positions. More subtle differences and some unexpected similarities, however, are also apparent and, in some cases, agree or, in others, conflict, with previously published information. With some exceptions, good general agreement between the two techniques was observed.
The local pharmacodynamics of a topical vasodilator (methyl nicotinate) has been followed noninvasively using photopulse plethysmography. This technique is sensitive to changes in blood flow through the cutaneous microcirculation and responds to the pharmacologic stimulus of the vasoactive agent employed. Five different application sites for the drug were studied and the time course of the local effect (i.e., onset, duration, and decay) was recorded. The applied amount of drug elicited, within a short period, a response which was saturable such that the observed increase in blood flow reached a plateau level. The decay of the elevated perfusion required approximately 1 h, suggesting a half-life for elimination of the drug from the skin of about 10 min. This result agrees closely with other reported values and suggests that the pharmacodynamic measurements of this study may prove useful in elucidating aspects of dermal pharmacokinetics.
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