By Karen Lou Kennedy-Evans, RN, FNP, APRN-BC, and Leslie Ritter, PhD, RN

Recently, WoundSource had the opportunity to talk with Karen Lou Kennedy-Evans, RN, FNP, APRN-BC, and Leslie Ritter, PhD, RN, via email about their presentation, “Thermographic Imaging of Terminal Skin Changes," for the NPIAP Spring 2023 Conference, which took place in San Diego, California, March 18, 2023.

In this presentation, the authors state that the appearance of the Kennedy Lesion (KL) and a deep tissue pressure injury (DTPI) are often similar, and, according to the speakers, it can cause a challenge for clinicians in their ability to make a visible determination of the wound. Thermographic imaging, they claim, can be used to measure and note temperature changes in a patient’s skin at the end of their life.

1. What is thermographic imaging? How can it be used to see/measure terminal skin changes?

   Contemporary long-wave infrared thermography (LWIT) systems include digital and long-wave infrared cameras and software for measuring wound size and thermal intensity. LWIT simultaneously captures a thermographic image set, both visual and infrared mirror images. The digital camera captures the visible light wavelengths from the electromagnetic spectrum, which are visible to the human eye. The infrared camera captures the long-wave infrared radiation emitted by the human body from the electromagnetic spectrum (7-14 μm), which is not visible to the human eye. The long-wave infrared image is often referred to as a thermographic image, representing a temperature pattern of the area imaged.¹ LWIT is based on the physiologic principle that body heat is produced by cellular metabolism and distributed by the blood to the rest of the body, particularly to the overlying skin, for loss by radiation and convection.²

   The human skin has a high emissivity rate of about 0.98 producing a reliable measurement that can be converted to a quantifiable temperature value.^3,4 The LWIT image supports the skin assessment, showing physiologic and pathophysiological changes below the intact or wounded skin as having inflammation (indicated as warmer temperatures) or hypoperfusion (indicated as cooler temperatures). The definition of a DTPI states that temperature changes often precede skin color changes.⁵ The temperature change over a bony prominence may indicate pre-visual signs and symptoms of DTPI or confirm the visual DTPI as having inflammatory or cool tissue changes. A visible discoloration without an abnormal temperature change can support the clinician to consider other etiologies for the skin discoloration beyond a pressure injury (PI) due to a lack of a warm or cool temperature.

2. What inspired you to create and present on this topic?

   The rationale for this presentation comes from the evidence-based recommendation in the 2019 EPUAP/NPIAP/PPPIA International Guideline on the Prevention and Treatment Pressure Ulcers/Injuries to “assess the temperature of the skin and soft tissue.”⁶ Using the LWIT gave the clinician an objective method for measuring the temperature of the skin discoloration. Certified Wound Care Clinicians from multiple hospitals confirming a KL according to standard hospital criteria which used LWIT identified and shared cases of early (first 24 hours) skin discolored tissue with no abnormal thermal temperature changes under the discoloration, which appeared suddenly; most of these patients were ill and in the Intensive Care Unit and passed away.

3. Why do you feel like it is a crucial topic for clinicians?

   Patient treatment plans and expected outcomes will vary based on the clinician's determination of a KL versus a DTPI. Determination of the assessment will assist in correct documentation, appropriate care decisions, and patient/family discussions. In addition, the clinician’s visual assessment and clinical judgment paired with the clinical history, can determine if the area in question meets the criteria for the Kennedy Lesion. Reporting the etiology findings is significant to facilities to avoid a negative impact on the quality reporting metrics and possible payment penalty, not to mention the possibility of legal proceedings if the KL is misidentified as a DTPI. Accurate documentation is crucial in defending your assessment. If you do not have access to LWIT for assessment and temperature readings, be diligent in charting the observable characteristics. KLs in the early hours of skin discoloration have specific characteristics which differentiate them from pressure injuries such as the following⁷:

   • Onset – KL appear suddenly and within hours.⁷ Determination of when the discoloration first appeared. If possible, note the last time the skin was observed non-discolored. (Discoloration was not there “X” hours ago.)
   • Measurement of discolored skin – Often, this appears as a larger area of discolored intact skin. In the study, the average measurement of the discolored skin in the first 24 hours was 11.3 cm. x 11.9 cm.
   • Depth – If there is no skin disruption of the discolored skin, then the skin is intact, making the depth measurement 0 cm. Do not leave the depth measurement blank.
   • Location – Usually appears on the sacrum and coccyx but can appear on the heels, posterior calf muscles, arms, and elbows.⁷
   • Shape – The majority are butterfly-shaped but can be pear or horseshoe-shaped.⁷
   • Borders – Edges are usually irregular⁷ or have jagged edges.
   • Progression – Once the skin opens, it may develop rapidly to what might be called a Stage 2, Stage 3, or Stage 4 injury.⁷

   Another finding of importance was the lab levels. In the study, 10 out of 10 patients had abnormally low hemoglobin and hematocrit. Nine out of 9 (level not available for one patient) patients had low serum albumin.

4. What are some common roadblocks regarding a clinician’s understanding when assessing changing skin? How might they overcome these roadblocks?

   Skin assessments are traditionally based on an anatomical assessment of what the clinician can see in the visible spectrum. Visible characteristics include wound size, edge definition, tissue type, exudate, and discoloration; these factors can be subjective and reflect what has already happened. A physiological assessment (from touch, smell, or hearing from the patient) is not possible in the visible spectrum. However, it could provide a view of what is to come and allow for early intervention and prevention of what is unseen. Temperature, texture, blanchable/non-blanchable erythema, moisture, odor, edema, and pain are valuable clinical indicators but are subjective and difficult to assess, becoming a guessing game.⁸

   LWIT is a newer technology to measure the size and temperature objectively; it requires training to obtain and analyze the image. The technology is non-contact, non-invasive, and easy to use at the bedside. Most clinicians have previously taken images or photos of wounds for documentation. The imaging is similar to other photography or imaging and is completed by trained clinicians.⁹

   The same LWIT imaging technique can be used for various skin assessments, including intact skin, incisions, open wounds, and dark skin tones, whether the evaluation supports inflammation, hypoperfusion, DTPI, KL, or other etiology findings. For clinicians dealing with bariatric patients, it is most helpful to assess and evaluate the many changes in the bariatric skin to help determine if this is cellulitis or a non-infection issue.

5. What is one thing clinicians can do tomorrow to improve their understanding of using this tool/process in their practice?

   Many articles support temperature and LWIT for skin and wound assessment. Guidelines from NPIAP⁶ and AORN¹⁰ recommend using temperature for skin, soft tissue, and dark skin. An FDA-cleared LWIT product is available in the US. A clinician does not need to prove the efficacy of temperature for assessment, and it can begin by using the technology for objective documentation and advanced assessment outcomes. Clinicians can request clinical information or demonstrations to support learning more or answer questions.

6. What do you hope clinicians will take away from your session?

   The LWIT is not new and can be used to support present on admission intact skin assessments for pre-visual DTPI, incision assessments, chronic wounds, dark skin tones, bariatric skin issues, assessment for superficial skin discoloration, and more. However, the research presented in the current study of KL is new. The study found that using LWIT to image the KL, there was no early (ie, within 24 hours of first observed skin discoloration) in temperature differences between KLs and surrounding skin. This finding contrasts with studies of DPTI which show an increase or decrease in discolored skin temperature compared to surrounding skin.

   For instance, a recent study found that KL has a unique early skin temperature signature.¹¹ Using LWIT to image the KL, there was no early (ie, within 24 hours of first observed discoloration) skin temperature differences between KLs and surrounding skin. The lack of abnormal early skin temperature findings in the KL contrasts with studies examining skin temperature changes of PIs, showing a significant decrease or increase in skin temperatures compared to control skin temperature.¹¹

   To advance our understanding of the pathophysiology of KL, it is important to understand the connection between the risk factors contributing to their development and the mechanisms that might account for the lack of early skin temperature change. One possibility is that the injury in the early stage of KL development may be restricted to the superficial cutaneous microcirculation and does not yet involve surrounding tissue. Therefore, abnormal skin temperature is not observed.¹¹ Understanding the best course of action for the wound care professional will, in turn, help them to give the best care to their patients.

Editor’s note: If you would like to read Karen Lou Kennedy-Evans and Dr. Leslie Ritter’s latest research, "Early Skin Temperature Characteristics of the Kennedy Lesion (Kennedy Terminal Ulcer)," visit Wound Management & Prevention.

References

1. 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. doi: 10.1097/01.ASW.0000511535.31486.bb
2. Lahiri BB, Bagavathiappan S, Jayakumar T, Philip J. Medical applications of infrared thermography: A review. Infrared Phys Technol. 2012;55(4):221-235. doi:10.1016/j.infrared.2012.03.0
3. Infrared Emissivity Table. Thermoworks. Accessed February 27, 2023. https://www.thermoworks.com/emissivity-table
4. Skin and core body temperature. Healthy Heating Educational Resource. 2012. Accessed January 20, 2023. https://www.healthyheating.com/
5. NPUAP Announces a change in terminology from pressure ulcer to pressure injury and updates the stages of pressure injury. National Pressure Ulcer Advisory Panel, European Pressure Ulcer Advisory Panel. Published April 13, 2016. Accessed February 27, 2023. https://cdn.ymaws.com/npiap.com/resource/resmgr/online_store/npiap_pres…
6. European Pressure Ulcer Advisory Panel, National Pressure Injury Advisory Panel, and Pan Pacific Pressure Injury Alliance. Prevention and Treatment of Pressure Ulcers/Injuries: The International Guideline 2019. Emily Haesler (Ed). EPUAP/NPIAP/PPPIA:2019.
7. State Operations Manual Appendix PP - Guidance to Surveyors for Long Term Care Facilities. Centers for Medicare and Medicaid Services. November 22, 2017. Accessed January 25, 2022. https//www.cms.gov/Regulations-and-Guidance/Guidance/Manuals/downloads/som107a…
8. Langemo D, Spahn J. A Multimodality Imaging and Software System for Combining an Anatomical and Physiological Assessment of Skin and Underlying Tissue Conditions. Adv Skin Wound Care.2016;29:155Y63.
9. Vargo D, McClure E, Spiller C, Tuten S. How Many Minutes Does it Take to Incorporate Long Wave Infrared Thermography (LWIT) into a Skin and Wound Assessment Workflow? Pending Poster Presentation at WOCN Annual Conference, June 2023, Las Vegas, NV.
10. The Guideline for Prevention of Perioperative Pressure Injury. Association of periOperative Registered Nurses. Published May 17, 2022. Accessed February 28, 2023. https://www.aornguidelines.org/guidelines/content?sectionid=245945765&v…
11. Kennedy-Evans K, et al. Early Skin Temperature Characteristics of the Kennedy Lesion (Kennedy Terminal Ulcer). Wound Manag Prev. 2023;69(1).

The views and opinions expressed in this blog are solely those of the author, and do not represent the views of WoundSource, HMP Global, its affiliates, or subsidiary companies.