Blanching response pressure sore detector apparatus and method

• US 20040054303A1
• Filed: 07/29/2002
• Published: 03/18/2004
• Est. Priority Date: 07/29/2002
• Status: Active Grant

• Current Assignee: Geoffrey L. Taylor
• Original Assignee: Geoffrey L. Taylor
• Inventors: Taylor, Geoffrey L.
• Granted Patent: US 7,155,273 B2
• Time in Patent Office: Days
• US Class Current: 600/587
• CPC Class Codes: A61B 5/0059 using light, e.g. diagnosis by transillumination, diascopy, fluorescence A61B5/0093, A61B5/1455, A61B5/02416 and A61B5/0261 take precedence
• CPC Class Codes: A61B 5/444 Evaluating skin marks, e.g. mole, nevi, tumour, scar
• CPC Class Codes: A61B 5/445 Evaluating skin irritation or skin trauma, e.g. rash, eczema, wound, bed sore
• CPC Class Codes: A61B 5/447 specially adapted for aiding the prevention of ulcer or pressure sore development, i.e. before the ulcer or sore has developed

Abstract

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.

Claims

1. An apparatus for detecting pressure sores on humans, said apparatus comprising;

a. a light source,

b. a first, leading photodetector spaced apart at a first radial distance from said light source,

c. a second, trailing photodetector spaced apart at a second radial distance from said light source,

d. difference signal amplifier means operatively connected to output terminals of said leading and t railing photodetectors, said amplifier means providing a first type indicator signal output if said leading photodetector outputs a signal greater by a first threshold value than an output signal from said trailing photodetector, and a second type indicator signal output if said trailing photodetector outputs a signal which exceeds by a second predetermined threshold value an output signal from said leading photodetector,

e. a transparent window transmissive to radiation from said light source located on a first, front side of said light source and said leading and trailing photodetectors, said window having a front surface pressable against the skin of a human and thereby cause said skin to blanch, said window being arranged to allow incident radiation from said light source to impinge on said skin, and to allow radiation reflected from said skin to impinge said photodetectors, and

f. indicator means connected to said amplifier means and providing a first type indicator response to said first type amplifier signal output, and a second type indicator response to said second type amplifier signal output.

2. The apparatus of claim 1 wherein at least a portion of energy emitted by said light source is in the approximate wavelength range of 0.8μ

to 1.5μ

.

3. The apparatus of claim 2 wherein said light source is further defined as including an incandescent lamp.

4. The apparatus of claim 1 wherein said difference signal amplifier means is further defined as including a first differential amplifier having a first terminal connected to an output terminal of one of said photodetectors, and a second input terminal connected to an output terminal of the other of said photodetectors.

5. The apparatus of claim 4 wherein said indicator means if further defined as including a first annunciator device having an input terminal connected to an output terminal of said first differential amplifier.

6. The apparatus of claim 5 wherein said first annunciator device is further defined as being of a type which produces an audible output signal if a signal level on said output terminal of said first differential amplifier exceeds a pre-determined threshold value.

7. The apparatus of claim 5 wherein said first annunciator device is further defined as being of a type which produces a visible output signal if a signal level on said output terminal of said first differential amplifier exceeds a pre-determined threshold value.

8. The apparatus of claim 7 wherein said annunciator device is further defined as being a light emitting diode.

9. The apparatus of claim 1 wherein said differential amplifier means is further defined as including a first differential amplifier having a first terminal connected to an output terminal of said leading photodetector, and a second input terminal connected to an output terminal of said trailing photodetector.

10. The apparatus of claim 9 wherein said indicator means is further defined as including a first annunciator which outputs a perceptible signal signifying presence of a non-blanchable erythema.

11. The apparatus of claim 10 wherein said differential amplifier means is further defined as including a second differential amplifier having a first input terminal connected to an output terminal of said trailing photodetector, and a second input terminal connected to an output terminal of said leading photodetector.

12. The apparatus of claim 11 wherein said indicator means is further defined as including a second annunciator which outputs a second perceptible signal signifying absence of a non-blanchable erythema.

13. An apparatus for detecting the presence of a non-blanchable erythema symptomatic of a pressure sore in human tissue, said apparatus comprising;

a. a housing,

b. an optically transmissive window located in a wall of said housing, said window having an outer surface pressable against human tissue and thereby cause said tissue to blanch,

c. a light source located within said housing inwardly of said window, said light source being energizable to emit light outwards through said window to the exterior of said housing,

d. a first, leading photodetector having a field of view through said window which includes a first region spaced from said light source in a first polar direction,

e. a second, trailing photodetector having a field of view through said window which includes a second region spaced apart in a second polar direction from said light source,

f. signal processing means having input terminals connected to said leading and trailing photodetectors and at least a first output terminal which outputs a signal indicative of which photodetector output signal is larger, and

g. indicator means connected to said signal processor means and providing a first type perceptible indicator response to a first type output signal from said signal processing means, and a second type perceptible indicator response to a second type output signal from said signal processing means.

14. The apparatus of claim 13 wherein said signal processing means is further defined as including a first differential amplifier having a first input terminal connected to an output terminal of said leading photodetector, and a second input terminal connected to an output terminal of said trailing photodetector.

15. The apparatus of claim 14 wherein said indicator means is further defined as including a first annunciator which provides a first type perceptible signal if said output signal from said leading photodetector exceeds by a first pre-determined threshold value an output signal from said trailing photodetector.

16. The apparatus of claim 15 wherein said signal processing means is further defined as including a second differential amplifier having a first input terminal connected to an output terminal of said trailing photodetector, and a second input terminal connected to an output terminal of said leading photodetector.

17. The apparatus of claim 16 wherein said first annunciator means is further defined as producing a second type perceptible signal if said output signal from said trailing photodetector exceeds by a second pre-determined threshold value an output signal from said leading photodetector.

18. The apparatus of claim 16 wherein said first annunciator means is further defined as being a first light emitting diode connected to an output terminal of said first differential amplifier.

19. The apparatus of claim 18 wherein said indicator means is further defined as including a second light emitting diode connected to an output terminal of said second differential amplifier.

20. The apparatus of claim 19 wherein said second light emitting diode emits light of a different wavelength than that emitted by said first light emitting diode.

21. The apparatus of claim 19 wherein said first and second light emitting diodes are both located behind a single lens viewable from the exterior of said housing.

22. The apparatus of claim 21 further including a first, NO-GO test/calibration template, said first template having printed thereon a first (e.g., left) colored test pattern positionable against said window underneath said leading photodetector, and a second (e.g., right) colored test pattern simultaneously positionable underneath said trailing photodetector, said first colored test pattern having hue and saturation levels corresponding to that of a non-blanchable, erythema, and said second colored test pattern having hue and saturation levels corresponding to that of healthy tissue, said first and second test patterns being sufficiently different in hue and saturation levels to cause said first LED to illuminate.

23. The apparatus of claim 21 further includes a second, GO test/calibration template, said second template having printed thereon a first (e.g., right) colored test pattern positionable against said window underneath said trailing photodetector, and a second (e.g., left) colored test pattern simultaneously positionable underneath said leading photodetector, said first colored test pattern having hue and saturation levels corresponding to that of a non-blanchable erythema, and said second test pattern having hue and saturation levels corresponding to that of healthy tissue, said first and second test patterns being sufficiently different in hue and saturation levels to cause said second LED to illuminate.

24. A method for detecting the presence of a non-blanchable erythema symptomatic of a pressure sore in human tissue, said method comprising;

a. pressing an optically transmissive body against an area of human tissue,

b. illuminating said area of tissue by means of light emitted from a light source and passing through said optically transmissive body,

c. receiving a first light sample emitted by said light source and reflected from a first, test region of said tissue area by first photodetector means providing a first photodetector output signal proportional to the intensity of said first light sample,

d. receiving a second light sample emitted by said light source and reflected from a second, standard region of said tissue area by second photodetector means providing a second photodetector output signal proportional to the intensity of said second light sample,

e. comparing the magnitudes of said first and second photodetector output signals and providing a first type of indicator signal if said first photodetector output signal exceeds said second photodetector output signal by a first pre-determined threshold value, and

f. providing a first type perceptible indicator in response to said first type indicator signal.

25. The method of claim 24 further including the step of comparing the magnitude of said second and first photodetector output signals and providing a second type of indicator signal if said second photodetector output signal exceeds said first photodetector output signal by a second pre-determined threshold value.

26. The method of claim 25 further including the step of providing a second type perceptible indication in response to said second type indicator signal.

27. The method of claim 24 wherein at least a portion of energy emitted by said light source is in the approximate wavelength range of 0.8μ

to 1.5μ

.

28. The method of claim 27 wherein said light source is further defined as including an incandescent lamp.