Wound care clinicians and patients can identify surface skin temperature differences with noncontact infrared skin thermometers.1 These inflammatory changes can be important for the early identification of neuropathic complications (eg, repetitive trauma and Charcot foot) and deep/surrounding wound infection. This technology can replace the subjective and often inaccurate assessment of skin temperature differences using the back of the clinician’s hand.2
Role in Preventing Foot Ulcers
Persons with diabetes and a high-risk neuropathic foot can use infrared thermometry at six sites on the foot to monitor plantar temperature changes: the first, third, and fifth metatarsal head, as well as the two midsides of the foot and the heel. If a temperature differential of 4 °F or higher is detected at any site, patients should restrict ambulation to reduce repetitive trauma and in turn reduce the likelihood of new foot ulcers.3 Three randomized controlled studies4–6 demonstrated that infrared thermometry prevented most new neuropathic ulcers in this patient population compared with both standard care and an education session for daily foot examinations, rendering this technology one of the few with strong clinical evidence.1,4–6
A Charcot joint occurs from neuropathy and trauma, leading to microfractures of the bone (Charcot neuroarthropathy). It can occur in any joint, but this discussion is limited to the foot as the most common site. Acute swelling, often with deformity of a neuropathic foot, may be a sign of Charcot neuroarthropathy. The patient usually does not have a foot ulcer or loss of skin integrity, and there may be acute pain in an otherwise painless foot (Figure 1).
Clinicians and patients can use the infrared thermometer to assess the aforementioned six sites on each foot. The increased temperature is often 8 °F to 15 °F warmer than the mirror image on the opposite foot.7
With an acute Charcot joint, patients should not apply any direct weight on the foot and use a wheelchair, contact cast, or removable cast walker. Given a loss of proprioception, crutches may be associated with falls. With patient self-monitoring, and as the temperature normalizes, weight bearing can gradually be increased with custom orthopedic shoes, including the introduction of a CROW (Charcot Restraint Orthotic Walker).
Infrared thermometry was introduced into the Toronto Regional Dermatology and Wound Clinic in 1996 to detect early infection signs to prevent destruction of cellular and/or tissue-based products. This use of infrared thermometry contributed to the creation of the NERDS and STONEES mnemonics,8–10 which use clinical signs to differentiate superficial (NERDS) from deep and surrounding infection (STONEES; Figure 2). In reviewing the individual factor analysis of each of the STONEES criteria, an increase in skin temperature of 3 °F or higher versus a mirror-image measurement of noninfected comparator skin is more than 8 times more likely to be associated with deep and surrounding infection9 (although two or more other STONEES criteria are also required for definitive diagnosis).
POINTS TO CONSIDER
- Inexpensive, commercially available noncontact infrared thermometers are useful instruments for wound care practitioners.1
- The Fahrenheit scale is preferable to the Celsius scale because it allows detection of smaller intervals of temperature differences making it easier to interpret at the bedside.
- These thermometers (cost $25–100) are just as effective as scientific grade thermometers (eg, Exergen, at a cost of $615.07).11,12
- Smart et al13 have similarly validated mini-infrared thermometers that can be carried in a nurse’s pocket to be equivalent to the scientific standard.
- Infrared thermometers should have a continuous mode with a maximum temperature reading and convert to Fahrenheit from Centigrade.14
- Using the validated whole-wound zigzag method (Figure 3)14 when the thermometer is in activated continuous mode, practitioners can determine a maximum temperature more quickly than measuring four distinct areas to obtain the highest reading around the margin of an ulcer.
- Maliyar et al15 validated nontouch infrared thermometry had a 3 °F increased or higher temperature compared to the mirror image on the opposite leg but cautioned that temperatures on the front and back of the same extremity may be misleading because of transfer of heat from an active infection.
- The industrial nontouch infrared thermometers can be held 8 to 12 inches from the skin/wound and give an accurate measurement compared with the scientific standard thermometer (eg, Exergen) that must be held within 1 to 2 cm of the skin surface.2,12 The closer distance is more likely to result in accidental bacterial contamination from the wound surface or exudate.
- Interrater reliability has been validated with similar infrared thermometer results between two independent observers.11
- Although arterial disease with ischemic changes can lower skin temperature, there are no validated studies on the use of nontouch surface infrared thermometry for this indication.
1. Sibbald RG, Mufti A, Armstrong DG. Infrared skin thermometry: an underutilized cost-effective tool for routine wound care practice and patient high-risk diabetic foot self-monitoring. Adv Skin Wound Care 2015;28(1):37–44.
2. Murff RT, Armstrong DG, Lanctot D, Lavery LA, Athanasiou KA. How effective is manual palpation in detecting subtle temperature differences?Clin Podiatr Med Surg 1998;15(1):151–4.
3. Armstrong DG, Boulton AJM, Bus SA. Diabetic foot ulcers and their recurrence. N Engl J Med 2017;376(24):2367–75.
4. Lavery LA, Higgins KR, Lanctot DR, et al. Home monitoring of foot skin temperatures to prevent ulceration. Diabetes Care 2004;27(11):2642–7.
5. Lavery LA, Higgins KR, Lanctot DR, et al. Preventing diabetic foot ulcer recurrence in high-risk patients: use of temperature monitoring as a self-assessment tool. Diabetes Care 2007;30(1):14–20.
6. Armstrong DG, Holtz-Neiderer K, Wendel C, Mohler MJ, Kimbriel HR, Lavery LA. Skin temperature monitoring reduces the risk for diabetic foot ulceration in high-risk patients. Am J Med 2007;120(12):1042–6.
7. Armstrong DG, Peters EJ. Charcot’s arthropathy of the foot. J Am Podiatr Med Assoc 2002;92(7):390–4.
8. Sibbald RG, Woo K, Ayello EA. Increased bacterial burden and infection: the story of NERDS and STONEES. Adv Skin Wound Care 2006;19(8):447–61.
9. Woo KY, Sibbald RG. A cross-sectional validation study of using NERDS and STONEES to assess bacterial burden. Ostomy Wound Manage 2009;55(8):40.
10. Fierheller M, Sibbald RG. A clinical investigation into the relationship between increased periwound skin temperature & local wound infection in patients with chronic leg ulcer. Adv Skin Wound Care 2010;23(8):369–79.
11. Mufti A, Coutts P, Sibbald RG. Validation of commercially available infrared thermometers for measuring skin surface temperature associated with deep and surrounding wound infection. Adv Skin Wound Care 2015;28(1):11–6.
12. QuickMedical. Exergen DermaTemp DT-1001 Infrared Dermal Thermometers. www.quickmedical.com/exergen-dermatemp-dt-1001-infrared-dermal-thermometers.html
. Last accessed September 9, 2021.
13. Smart H, Al Jahmi E, Buhiji E, Smart SA. Validation and inter-rater reliability of inexpensive, mini, no-touch infrared surface thermometry devices as an assessment tool for prediction of wound-related deep and surrounding infection. WCET J 2019;39(1):18–22.
14. Mufti A, Somayaji R, Coutts P, Sibbald RG. Infrared skin thermometry: validating and comparing techniques to detect periwound skin infection. Adv Skin Wound Care 2018;31(1):607–11.
15. Maliyar K, Persaud-Jaimangal R, Sibbald RG. Associations among skin surface pH, temperature, and bacterial burden in wounds. Adv Skin Wound Care 2020;33(4):80–5.