1. Black, Joyce PhD, RN, FAAN

Article Content

SKIN ASSESSMENT is aimed at discovering any abnormalities, including pressure injuries in early stages, in order to escalate prevention plans and slow evolution to more severe stages. The National Pressure Ulcer Advisory Panel has often noted that early signs of pressure injury, such as erythema or purple hues, aren't easily identified in darkly pigmented skin.1 A recent study by Bauer et al. highlights this statement by reporting that hospitalized Black patients had a higher rate of pressure injury compared with other races (2.4% compared with 1.2% to 1.8% in other groups).2 This article discusses the use of infrared thermography and other methods that can help clinicians identify Stage 1 pressure injury and deep tissue pressure injury (DTPI) in patients with darkly pigmented skin. (See Distinguishing pressure injuries.)


How pressure leads to changes in skin color

When pressure is applied to the skin and underlying soft tissue, two changes can occur.


* If the pressure is intense, as when the patient is lying on a hard surface such as the floor, a stretcher, or OR table, muscle cells become deformed and can lyse. High-intensity pressure creates deep tissue injury and the skin overlying the damaged internal soft tissue becomes maroon or purple.1,3 However, evidence of skin injury isn't immediately visible: Color changes become apparent about 48 hours after the pressure was applied.4


* If pressure is less intense and more prolonged, as when a patient is lying on a bed or sitting in a chair, the blood supply to the tissues is interrupted and the tissue becomes ischemic. When the pressure is removed, the area may become erythematous (due to the rapid reperfusion of the ischemic area) and sometimes nonblanchable.3 Nonblanchable erythema is attributed to microthrombi in the arterioles and lymphatic edema.3 Dark skin pigment blocks the visual cue to the nonblanchable redness.



Because of the difficulty visualizing erythema in dark skin, the 2014 Prevention and Treatment of Pressure Ulcers: Clinical Practice Guideline recommends including assessment of skin temperature, edema, and induration in every skin assessment, but especially for patients with darkly pigmented skin.1 When ischemic tissue is reperfused, the soft tissue becomes boggy or indurated. Compare how this tissue feels compared with tissues in adjacent or contralateral areas.5

Figure. Distinguishi... - Click to enlarge in new windowFigure. Distinguishing pressure injuries

Pain is another red flag

Pressure on skin and soft tissue leads to ischemia.1 Patients who can report pain will report pain in soft tissue that has been subjected to pressure. Early symptoms of both Stage 1 pressure injury and DTPI include pain.6 Pain in body areas subjected to pressure and pain in body areas that shouldn't be painful is a clue suggesting an underlying pressure injury.4 Patients who experience pain from a Stage 1 pressure injury are more likely to develop Stage 2 pressure injury: partial-thickness skin loss with exposed dermis.1,7


Enhancing assessment

Several strategies can help nurses assess skin injuries.


* Moisten the skin. This simple method can help nurses detect color changes in dark skin. Many patients with darkly pigmented skin have very dry skin; simply moistening it with tap water can highlight the color change.


* Assess perfusion with long-wave infrared thermography. Thermography is a noninvasive, noncontact method for measuring temperature differences between injured and adjacent skin. It does this by creating a two-dimensional image from infrared radiation emitted by the human body.8-10 Warm tissue is well perfused, cold tissue is not.



Gradations of the color scale on the two-dimensional images produced by thermography allow visualization of tissue perfusion. On thermographic images, ischemic tissue from pressure injury appears blue or purple.8


Besides letting the nurse visualize tissue perfusion, thermography can also quantify the extent of perfusion. Gradations in color will be seen and the differences in temperature of normal body areas and the area of interest will be computed (relative temperature differential).8

Figure. Scanning for... - Click to enlarge in new windowFigure. Scanning for trouble

The images above show a DTPI in a darkly pigmented patient (see Scanning for trouble). The purple coloration on the thermographic image and a negative 6.0[degrees] C relative temperature differential indicate ischemia that isn't yet visible in the skin. In patients who are darkly pigmented, the visible color of the skin has no impact on the infrared radiation captured by thermography.11


On alert for early clues

Improved methods are available to help nurses assess the skin in darkly pigmented patients for Stage 1 pressure injury and DTPI. Be alert to patient reports of pain in soft tissue that has been subjected to pressure and consider augmented methods to find early changes.




1. National Pressure Ulcer Advisory Panel, European Pressure Ulcer Advisory Panel, Pan Pacific Pressure Injury Alliance. In: Haesler E, ed. Prevention and Treatment of Pressure Ulcers: Clinical Practice Guideline. Perth, Australia: Cambridge Media; 2014. [Context Link]


2. Bauer K, Rock K, Nazzal M, Jones O, Qu W. Pressure ulcers in the United States' Inpatient Population from 2008 to 2012: results of a retrospective nationwide study. Ostomy Wound Manage. 2016;62(11):30-38. [Context Link]


3. Oomens CW, Bader DL, Loerakker S, Baaijens F. Pressure induced deep tissue injury explained. Ann Biomed Eng. 2015;43(2):297-305. [Context Link]


4. Black JM, Brindle CT, Honaker JS. Differential diagnosis of suspected deep tissue injury. Int Wound J. 2016;13(4):531-539. [Context Link]


5. Gillani S, Cao J, Suzuki T, Hak DJ. The effect of ischemia reperfusion injury on skeletal muscle. Injury. 2012;43(6):670-675. [Context Link]


6. Gorecki C, Closs SJ, Nixon J, Briggs M. Patient-reported pressure ulcer pain: a mixed-methods systematic review. J Pain Symptom Manage. 2011;42(3):443-459. [Context Link]


7. Smith IL, Brown S, McGinnis E, et al Exploring the role of pain as an early predictor of category 2 pressure ulcers: a prospective cohort study. BMJ Open. 2017;7(1):e013623. [Context Link]


8. Langemo DK, Spahn JG. A reliability study using a long-wave infrared thermography device to identify relative tissue temperature variations of the body surface and underlying tissue. Adv Skin Wound Care. 2017;30(3):109-119. [Context Link]


9. Tattersall GJ. Infrared thermography: a non-invasive window into thermal physiology. Comp Biochem Physiol A Mol Integr Physiol. 2016;202:78-98


10. Yang WJ, Yang PP. Literature survey on biomedical applications of thermography. Biomed Mater Eng. 1992;2(1):7-18. [Context Link]


11. House CM, Taylor RJ, Oakley EH. Repeatability of a cold stress test to assess cold sensitization. Occup Med (Lond). 2015;65(7):578-584. [Context Link]