Letter to the Editor: Pressure Ulcers: The Role of Thermography and the Need to Revisit Staging

  Regarding the article, Farid et al. Using temperature of pressure-related intact discolored areas of skin to detect deep tissue injury: an observational, retrospective, correlational study. Ostomy Wound Manage. 2012;58(8):20–31: The article was a single-institution retrospective review of pressure-related color changes in the setting of intact skin.

  With respect to the staging system, the National Pressure Ulcer Advisory Panel follows the scientific process. As such, change is warranted based on robust and confirmed research. Also, any definition meant for widespread use must walk the line between comprehension and comprehensiveness.   For future researchers in this area we recommend:

  Methodology. It is not clear that industrial grade thermography is the appropriate modality for this type of investigation. From the work of numerous people in infrared research, we understand that many factors can affect accuracy and precision, including microclimate, comorbidities, timing, ambient temperature, and inter/intraoperator reliability. These issues must be clearly outlined, rigorously applied in the protocol, and accurately reported.

  Also, the referral protocol for the institution was biased against Stage I ulcers. It is likely that some Stage I ulcers were not seen by the wound care service and therefore under-represented in this work. This type of selection bias adversely affects the statistics.

  Discussion. The discussion section allows the authors to extend their specific findings to larger scientific and clinical questions. This type of extrapolation must be in line with sound scientific method and professional norms. This type of extrapolation must be in line with sound scientific method and professional norms. The statement from this article that “The NPUAP definition of Stage I pressure ulcer is controversial because it was initiated as a consensus” is inaccurate and unfounded. There is no evidence in the literature that a controversy exists. We invite journal editorial boards and reviewers to pay attention to this because such articles may incite unintended confusion. For someone scanning the literature, this statement may be unnecessarily misleading.

  Conclusion. Although not an explicit goal of this project, the authors suggest their findings should be used to revise the NPUAP Stage I pressure ulcer definition. The article’s results section makes no mention of which lesions were Stage I ulcers. It is difficult to agree or disagree with the authors in the absence of data. If the manuscript does not explicitly state cohort members, it is impossible to know if or to what degree the present definition was inadequate.

  There is no doubt the science of pressure ulcer classification continues to evolve. We are open to new ideas based upon reliable accurate reproducible science that will allow us to improve definitions and classifications. We encourage this group and others to remain on this path.

    Aimee Garcia, MD, CWS, FACCWS
    President
    Aamir Siddiqui, MD
    Chair, Public Policy Mission Committee
    National Pressure Ulcer Advisory Panel

Reply

  In general, the concerns of Dr. Garcia and Dr. Siddiqui seem to arise from either a misunderstanding or misreading of our study. We make the following clarifications:

    1.The accuracy of infrared technology is well-referenced in our study. The thermography camera used in this study belongs to the same family of cameras used in past studies (Farid,¹ Fierheller,² Nagase,³ Nakagami,⁴ Oe⁵). The claims of camera inaccuracy are unreferenced, so it is difficult to comment further.

    2. Regarding the precision of the study measurements and how they may be affected by various factors, our findings were based on the temperature differential between the pressure-related intact discolored areas of skin (PRIDAS) and that of normal skin no more than 2 inches away. Comparing proximal skin surface temperature adequately addressed concerns about measurement precision. Both sites were exposed to the same microclimate conditions. Temperatures of the PRIDAS and the adjacent skin and the ambient temperature were all collected simultaneously. The camera is easy to use and adjusts for distance (accurate at ± 0.1˚ C up to 6 feet away from the target). All data were collected by the principal investigator, which minimizes variability.

    3. As to the claim the study was biased against Stage I ulcers, the PRIDAS we examined were found on patients who already had ulcers (atypical ulcers, deep tissue injuries, and Stage III and Stage IV ulcers). The referral process at the facility for a wound care nurse is not protocolized (ie, dependent on the judgment of various clinicians) and not all pressure ulcers receive a consult.

    4.Drs. Garcia and Siddiqui claim the study concludes, “Thermography is an excellent tool for diagnosing Stage I pressure ulcers.” This statement does not appear in the publication. The purpose of our study did not involve diagnosing Stage I pressure ulcers. However, based on physiological principles of perfusion, heat transfer, and tissue viability, the study does not support the NPUAP’s assertion that Stage I nonblanchable erythema is merely a lesion “of risk.” Findings also do not support the NPUAP’s assertion that all blanchable hyperemia is not a lesion of risk. One out of five lesions with positive capillary refill/blanching progressed to necrosis.

    5. Drs. Garcia and Siddiqui claim the article makes no mention of which lesions were Stage I, which makes it difficult to assess if the data support potential changes to the definition of Stage I ulcer. However, referring to Table 4 in our article, 30 (35.3%) of the 85 PRIDAS did not have capillary refill (ie, nonblanchable and consistent with the NPUAP definition of Stage I). Of the 30 nonblanchable PRIDAS, 18 (60%) progressed to necrosis despite standard pressure-relief measures. This suggests that many nonblanchable erythemas are more advanced (tissue that is already dead or dying) than what is considered Stage I in staging of diseases. Therefore, the NPUAP staging guidelines do not seem to reflect the expected progression seen with staging of disease — a progression that is part of the definition of “staging” as proposed by the Oxford Dictionary (“Medicine: diagnosis or classification of the particular stage reached by a progressive disease”).⁶ Thus, healthcare facilities are being financially penalized with decreased reimbursement and lawsuits for Stage II and Stage IV pressure ulcers — ulcers that may be the inevitable result of tissue death that occurred before admission or during a major unavoidable health crisis (eg, cardiac arrest) a week or more before the appearance of deep tissue injury (purple ulcer).

  In conclusion, we believe an exciting implication of our study is the solving of the skin color issue.⁷ After more than two decades, we can finally address the NPUAP’s “elephant in the room” regarding visual assessment of pressure ulcers — ie, “What if the patient doesn’t have white skin?” We now have a tool that reduces the assessment of patients of all colors to a physiologically based, scientifically valid measurement: skin temperature. The thermography camera is skin color-blind.
    Karen Farid, DNP, CWOCN
    Principal Investigator

This article was not subject to the Ostomy Wound Management peer-review process.

1. Farid K. Applying observations from forensic science to understanding the development of pressure ulcers. Ostomy Wound Manage. 2007;53(4):26–44.

2. Fierheller MS. A clinical investigation into the relationship between increased periwound skin temperature and local wound infection in patients with chronic leg ulcers. Adv Skin Wound Care. 2010;23(8):369–379.

3. Nagase TS. Variations of plantar thermographic patterns in normal controls and nonulcer diabetic patients: novel classification using angiosome concept. J Plast Reconstr Anesthet Surg. 2011;64(7):860–866.

4. Nakagami GS. Predicting delayed pressure ulcer healing using thermography: a prospective cohort study. J Wound Care. 2010;19(11):465–472.

5. Oe MY. Thermographic findings in a case of type 2 diabetes with foot ulcer and osteomyelitis. J Wound Care. 2012;21(6):274–278.

6. Sibbald RG. Pressure ulcer staging revisited: superficial skin changes and deep pressure ulcer framework. Adv Skin Wound Care. 2011;24(11):571–580.

7. Mossir D. The Diversity of Pressure Ulcers. Available at: http://community.nursingspectrum.com/MagazineArticles. Accessed November 26, 2012.