A portable, hand-holdable
Blanching Response Tester apparatus (BRT) pressable against the
skin of a
human patient to provide an indication of a non-blanchable
erythema indicative of an incipient
pressure sore includes a housing having in a front end wall thereof an optically transmissive window and within the housing a broad-band
light source electrically energizable to emit light including energy in the near
infrared (0.8μ to 1.5μ) outwards through the window. A first, leading
photodetector spaced laterally apart from the
light source and a second, trailing
photodetector spaced
equidistant from the
light source in an opposite direction have fields of view which include regions of the
skin ahead of an behind a central area of the
skin illuminated by the light source. Electronic
signal processing circuitry within the BRT housing includes a pair of differential amplifiers having opposite pairs of inputs connected to the pair of photodetectors, one
amplifier driving a first, “NO-GO” red, light-emitting
diode mounted in an upper wall panel of the housing, and the other
amplifier driving a second, “GO”
green LED. When the BRT window is pressed against the skin and the light source energized, if light reflected from the skin by leading
photodetector over a questionable area of the skin exceeds light reflected from a known healthy
sample area of skin beneath the trailing photodetector the red, NO-GO LED is illuminated if the difference in light values exceeds a first threshold values signifying a
pressure sore, and if light received by the trailing photodetector exceeds that received by the leading photodetector by a second threshold value, the green, GO LED is illuminated.