Thermographic assessment of burns using a nonpermeable membrane as wound covering

doi:10.1016/0305-4179(91)90134-3

Burns

Volume 17, Issue 2, April 1991, Pages 117-122

https://doi.org/10.1016/0305-4179(91)90134-3 Get rights and content

Abstract

Infrared thermography is a useful technique for the investigation of disorders which affect skin blood flow. The damage to skin blood vessels caused by thermal injury is a major determinant of the capacity of the wound to heal. Thermographic assessment of this damage has been found to correlate with the healing time of burn wounds. However, the application of thermography to the assessement of burns for early surgery has been limited because of the difficulties involved in correcting for cooling artefacts resulting from the effect of evaporative water loss (EWL) at the wound surface. A water impermeable polyvinylchloride film (sold in the USA as Saran Wrap, in Australia as Glad Wrap and in the UK as Clingfilm (CF)) was investigated as a wound covering to avoid this cooling effect. It was found that the CF abolished the cooling effect of EWL and did not significantly interfere with the measurement of surface temperature. This material provides a solution to the problems of thermographic examination of wounds such as burns where damage to the skin surface allows exudation or EWL to occur.

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Cited by (42)

Prospective comparative evaluation study of Laser Doppler Imaging and thermal imaging in the assessment of burn depth
2018, Burns
Citation Excerpt :
Static thermographic images were recorded at a distance of 70 cm. For the purposes of standardization, skin cooling [14] and occlusive dressings [15] were not used. The base temperature was adjusted to 30 °C and the peak temperature adjusted to the patient’s core temperature, as measured by tympanic thermometer (Braun Thermoscan®, Braun GmbH, Germany).
The accurate assessment of burn depth is challenging but crucial for surgical excision and tissue preservation. Laser Doppler Imaging (LDI) has gained increasing acceptance as a tool to aid depth assessment but its adoption is hampered by high costs, long scan times and limited portability. Thermal imaging is touted as a suitable alternative however few comparison studies have been done.
Sixteen burn patients with 52 regions of interests were analysed. Burn depth was determined using four methods LDI, thermal imaging, photographic and real-time clinical evaluation at day 1 and day 3. LDI flux and Delta T values were used for the prediction of outcomes (wound closure in <21 days). Photographic clinical evaluation of burn depth was performed by 4 blinded burn surgeons.
Accuracy of assessment methods were greater on post burn day 3 compared to day 0. Accuracies of LDI on post burn day 0 and 3 were 80.8% and 92.3% compared to 55.8% and 71.2% for thermal imaging and 62.5% and 71.6% for photographic clinical assessment. Real-time clinical examination had an accuracy of 88.5%. Thermal imaging scan times were significantly faster compared to LDI.
LDI outperforms thermal imaging in terms of diagnostic accuracy of burn depth likely due to the susceptibility of thermal imaging to environmental factors.
The FLIR ONE thermal imager for the assessment of burn wounds: Reliability and validity study
2017, Burns
Citation Excerpt :
Furthermore, during the analyses of ΔT values, we noticed that some burn wounds showed a negative ΔT value, whereas a positive value was expected based on clinical evaluation and actual healing time. We hypothesize that these impaired results are a consequence of the confounding effect of evaporative heat loss, which causes burn wounds to be falsely interpreted as deep wounds [3,23]. Moreover, we found in both chemical burn wounds that the ΔT value was more positive than one would expect.
Objective measurement tools may be of great value to provide early and reliable burn wound assessment. Thermal imaging is an easy, accessible and objective technique, which measures skin temperature as an indicator of tissue perfusion. These thermal images might be helpful in the assessment of burn wounds. However, before implementation of a novel measurement tool into clinical practice is considered, it is appropriate to test its clinimetric properties (i.e. reliability and validity). The objective of this study was to assess the reliability and validity of the recently introduced FLIR ONE thermal imager.
Two observers obtained thermal images of burn wounds in adult patients at day 1–3, 4–7 and 8–10 after burn. Subsequently, temperature differences between the burn wound and healthy skin (ΔT) were calculated on an iPad mini containing the FLIR Tools app. To assess reliability, ΔT values of both observers were compared by calculating the intraclass correlation coefficient (ICC) and measurement error parameters. To assess validity, the ΔT values of the first observer were compared to the registered healing time of the burn wounds, which was specified into three categories: (I) ≤14 days, (II) 15–21 days and (III) >21 days. The ability of the FLIR ONE to discriminate between healing ≤21 days and >21 days was evaluated by means of a receiver operating characteristic curve and an optimal ΔT cut-off value.
Reliability: ICCs were 0.99 for each time point, indicating excellent reliability up to 10 days after burn. The standard error of measurement varied between 0.17–0.22 °C. Validity: the area under the curve was calculated at 0.69 (95% CI 0.54–0.84). A cut-off value of −1.15 °C shows a moderate discrimination between burn wound healing ≤21 days and >21 days (46% sensitivity; 82% specificity).
Our results show that the FLIR ONE thermal imager is highly reliable, but the moderate validity calls for additional research. However, the FLIR ONE is pre-eminently feasible, allowing easy and fast measurements in clinical burn practice.
Forward-looking infrared imaging predicts ultimate burn depth in a porcine vertical injury progression model
2016, Burns
Current methods of assessing burn depth are limited and are primarily based on visual assessments by burn surgeons. This technique has been shown to have only 60% accuracy and a more accurate, simple, noninvasive method is needed to determine burn wound depth. Forward-looking infrared (FLIR) thermography is both noninvasive and user-friendly with the potential to rapidly assess burn depth. The purpose of this paper is to determine if early changes in burn temperature (first 3 days) can be a predictor of burn depth as assessed by vertical scarring 28 days after injury.
While under general anesthesia, 20 burns were created on the backs of two female Yorkshire swine using a 2.5 cm × 2.5 cm × 7.5 cm, 150 g aluminum bar, for a total of 40 burns. FLIR imaging was performed at both early (1, 2 and 3 days) and late (7, 10, 14, 17, 21, 24 and 28 days) time points. Burns were imaged from a height of 12 inches from the skin surface. FLIR ExaminIR^© software was used to examine the infrared thermographs. One hundred temperature points from burn edge to edge across the center of the burn were collected for each burn at all time points and were exported as a comma-separated values (CSV) file. The CSV file was processed and analyzed using a MATLAB program. The temperature profiles through the center of the burns generated parabola-like curves. The lowest temperature (temperature minimum) and a line midway between the temperature minimum and ambient skin temperature at the burn edges was defined and the area of the curve calculated (the “temperature half-area”).
Half-area values 2 days after burn had higher correlations with scar depth than did the minimum temperatures. However, burns that became warmer from 1 day to 2 days after injury had a lower scar depth then burns that became cooler and this trend was best predicted by temperature minima. When data were analyzed as a diagnostic test for sensitivity and specificity using >3 mm scarring, i.e. a full-thickness burn, as a clinically relevant criterion standard, temperature minima at 2 days after burn was found to be the most sensitive and specific test.
FLIR imaging is a fast and simple tool that has been shown to predict burn wound outcome in a porcine vertical injury progression model. Data showed that more severe burn wounds get cooler between 1 and 2 days after burn. We found four analytic methods of FLIR images that were predictive of burn progression at 1 and 2 days after burn; however, temperature minima 2 days after burn appeared to be the best predictive test for injury progression to a full-thickness burn. Although these results must be validated in clinical studies, FLIR imaging has the potential to aid clinicians in assessing burn severity and thereby assisting in burn wound management.
A comparison of non-invasive imaging modalities: Infrared thermography, spectrophotometric intracutaneous analysis and laser Doppler imaging for the assessment of adult burns
2015, Burns
Citation Excerpt :
The same confounding effect from curvilinear surfaces does not appear to cause a problem for IRT, although thermography image reliability is subject to other well-established confounding variables, primarily evaporative water losses causing wounds interpreted as falsely deep [29]. Cole et al. abolished the cooling effect of evaporative water loss for static thermography using a non-permeable membrane as a wound covering, such as Clingfilm™, which he found to not significantly interfere with the measurement of surface temperature [18]. Further studies could now investigate a protocol for Clingfilm™ application over burns during IRT.
Currently, the only evidence-based adjunct to clinical evaluation of burn depth is laser Doppler imaging (LDI), although preliminary studies of alternative imaging modalities with instant image acquisition are promising. This is a study to investigate the accuracy of infrared thermography (IRT) and spectrophotometric intracutaneous analysis (SIA) for burn depth assessment, and compare this to the current gold standard: LDI. We include a comparison of the three modalities in terms of cost, reliability and usability.
We recruited 20 patients with burns presenting to the Chelsea and Westminster Adult Burns Service. Between 48 h and 5 days afterburn we recorded imaging using moorLDI2-BI-VR (LDI), FLIR E60 (IRT) and Scanoskin™ (SIA). Subsequent clinical management and outcome was as normal, and not affected by the extra images taken.
24 burn regions were grouped according to burn wound healing: group A healed within 14 days, group B within 14–21 days, and group C took more than 21 days or underwent grafting. Both LDI and IRT accurately determined healing potential in groups A and C, but failed to distinguish between groups B and C (p > 0.05). Scanoskin™ interpretation of SIA was 100% consistent with clinical outcome.
FLIR E60 and Scanoskin™ both present advantages to moorLDI2-BI-VR in terms of cost, ease-of-use and acceptability to patients. IRT is unlikely to challenge LDI as the gold standard as it is subject to the systematic bias of evaporative cooling. At present, the LDI colour-coded palette is the easiest method for image interpretation, whereas Scanoskin™ monochrome colour-palettes are more difficult to interpret. However the additional analyses of pigment available using SIA may help more accurately indicate the depth of burn compared with perfusion alone. We suggest development of Scanoskin™ software to include a simplified colour-palette similar to LDI and additional work to further investigate the potential of SIA as an alternative to the current gold standard.
Bioresources in the pharmacotherapy and healing of burns: A mini-review
2013, Burns
Citation Excerpt :
For that matter, radiology or medical imaging offers promising solutions in assessing and monitoring burn wound healing. Thermography or thermographic assessment of burns using infrared imaging is an example of an imaging technique with potential in estimating burns depth and damage to skin's blood vessels [13–17]. Thus, it may be of diagnostic and prognostic value, and could potentially help guide treatment.
A pilot evaluation study of high resolution digital thermal imaging in the assessment of burn depth
2013, Burns
Citation Excerpt :
They then retrospectively analyzed the predictive value of the initial clinical and thermographic assessments and thermography correctly predicted the outcome and was highly significant. The authors conclude that thermography can identify a subgroup of patients with deep dermal burns that might benefit from early surgery [10–12]. Other than a few animal studies [13,14] no further work as been published on the use of thermal imaging in burns.
Thermal imaging is a tool that can be used to determine burn depth. We have revisited the use of this technology in the assessment of burns and aim to establish if high resolution, real-time technology can be practically used in conjunction with clinical examination to determine burn depth. 11 patients with burns affecting upper and lower limbs and the anterior and posterior trunk were included in this study. Digital and thermal images were recorded at between 42 h and 5 days post burn. When compared to skin temperature, full thickness burns were significantly cooler (p < 0.001), as were deep partial thickness burns (p < 0.05). Superficial partial thickness burns were not significantly different in temperature than non-burnt skin (p > 0.05). Typically, full thickness burns were 2.3 °C cooler than non-burnt skin; deep partial thickness burns were 1.2 °C cooler than non-burnt skin; whilst superficial burns were only 0.1 °C cooler. Thermal imaging can correctly determine difference in burn depth. The thermal camera produces images of high resolution and is quick and easy to use.

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^∗: Present address: Medical Laser Unit, Heriot-Watt University, Riccarton, Edinburgh, UK.

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Scientific and clinical paperThermographic assessment of burns using a nonpermeable membrane as wound covering

Abstract

Burns

Br. J. Plast. Surg.

Br. J. Plast. Surg.

Burns

Burns

Scientific and clinical paper
Thermographic assessment of burns using a nonpermeable membrane as wound covering