ABSTRACT
OBJECTIVE: The high melanin concentration in dark skin prevents the observation of a blanch response to light finger pressure. The objective of this study was to determine the ability of visible and near-infrared spectroscopy (the technique used in pulse oximetry) to monitor a blanch response from in vivo spectra in individuals with light and dark skin, based on changes in blood volume.
DESIGN: A quasi-experimental repeated measures design was employed. A stepper motor with an attached spectrophotometer probe was used to deliver controlled pressure to the participants' forearms, mimicking the finger-blanching test. Visible and near-infrared spectra were acquired throughout the blanching cycle.
SETTING: The In Vivo Tissue Optics Lab at the Institute for Biodiagnostics, Winnipeg, Manitoba, Canada.
PARTICIPANTS: A convenience sample of 10 healthy light-skinned individuals and 10 healthy dark-skinned individuals.
RESULTS: Determined by analysis of the spectra, the 2 groups differed in pigmentation in both the visible (P<.01) and near-infrared (P<.01) regions of the absorbance spectrum. There was a significant difference in total hemoglobin at high and low pressure in both the visible (P<.01) and near-infrared (P<.05) regions.
CONCLUSIONS: The observation of a significant difference in total hemoglobin at high and low pressure in both light- and dark-skinned groups in this study demonstrates the ability of visible and near-infrared spectroscopy to monitor blood volume changes associated with a blanch response. These findings support the potential use of this technology as the basis of a clinically useful blanch response tool that is insensitive to skin color.