Background: There has been a lack of methods to provide quantitative information of local tissue edema after burn injury. Noninvasive dielectric measurements provide this information. The measured value, the dielectric constant, is directly related to the amount of water in tissue. Using probes of different sizes, the measurements give information from different tissue depths. The aim of this study was to characterize edema formation at different tissue depths and to examine whether the dielectric measurements could be used to distinguish partial- and full-thickness burns in pigs.
Methods: An experimental animal study with pigs (n = 6) was performed in which dielectric measurements were taken of superficial, partial-thickness, and full-thickness burns for 72 hours.
Results: There was an increase in tissue water content in the superficial dermis in the partial-thickness burns at 48 hours. In whole dermis, the superficial burns resulted in increased tissue water content at 8 hours, and the partial-thickness burns resulted in increased tissue water content at 8, 24, and 72 hours. In deep burns, the water content was significantly decreased in the superficial dermis at 24 hours. All burns resulted in a considerable increase in fat water content. The dielectric probes could be used to differentiate partial- and full-thickness burns as early as 8 hours after burn. Receiver operating curve analysis of the measurements indicated 70 to 90 percent sensitivity and 80 to 100 percent specificity after 8 hours.
Conclusions: The dielectric measurements provide a sensitive and noninvasive method for examining tissue edema and differentiate partial- and full-thickness burns in experimental burns. Thus, they are of clinical interest for early burn depth determination.