Predicting the different progressions of early pressure injury by ultraviolet photography in rat models

Abstract

Early pressure injury (PI) can result in either spontaneous healing (SH) or deterioration into ulcer (DU). However, determining whether PI will progress into SH or DU on the basis of non-blanchable erythema only is difficult. In this study, we constructed two animal PI models to mimic SH and DU injuries and observed haemorrhage by using ultraviolet (UV) photography to develop potential clinical indicators for predicting the progression of early PI. Macroscopy, UV photography, and skin temperature observations were obtained. In the SH group, macroscopic observation showed the erythema was obvious at 0.5 hours after decompression and faded gradually had almost disappeared at 72 hours. In the DU group, the erythema persisted, and an erosion appeared at 24 hours after decompression and expanded at 36 hours. The erythema developed into an obvious ulcer at 48 hours and enlarged at 72 hours. The obvious ulcer found at 48 hours through macroscopic observation was clearly visible at 36 hours with UV photography, and a significant difference in grey values between the two groups was found at as early as 18 hours (P < .05). This study provided evidence showing that UV photography can predict the different progression stages of early PI. Additionally, when combined with the transparent disc method, UV photography also can be used to identify the circulatory disorders of early PI, such as haemorrhage or hyperaemia and even congestion.

Keywords: circulatory disorders; early pressure injury; erythema; predicting progression; ultraviolet.

FIGURE 1

Two pressure injury (PI) models. The PI models were established by pressing the dorsal skin for 3.45 hours between two circular neodymium magnets (10 mm in diameter). The left side (SH group) was pressed by two magnets with a thickness of 2 mm while the right side (DU group) was pressed by two magnets with a thickness of 4 mm. SH, spontaneous healing; DU, deteriorate to ulcer

FIGURE 2

Ultraviolet photographs of the pressure injury (PI) wound and grey value of each area in the deteriorate to ulcer group. The left shows the PI wound at 18 hours after decompression, and the right shows the same area at 72 hours when the ulcer had developed and become macroscopic. The UA was marked at different times at the same site in accordance with location and shape at 72 hours. UA, ulcer area; IA, improvement area

FIGURE 3

Photos taken by the digital camera (visual image) and dermal camera (ultraviolet [UV] image). The a‐i and A‐I are visual images taken by digital camera, a′‐i′ and A′‐I′ are UV images taken by dermal camera for two groups, respectively. “⇓” shows the progression from bushy spots at 0.5 hours after decompression to fusion to ulcers at 72 hours

FIGURE 4

Grey value of each area within pressure injury wounds under ultraviolet photography. The dotted line presents the grey value of control skin before pressure was applied on the rats. SH, spontaneous healing; DU, deteriorate to ulcer; UA, ulcer area; IA, improvement area. *P < .05, **P < .01 vs whole area of SH group

FIGURE 5

ROC curve of ultraviolet photography vs true skin classification. A ROC curve that rises quickly, that is, when sensitivity and specificity are high, is a good cut‐off level for a diagnostic test. AUC = 0.901, 95%CI: 0.851–0.952. ROC, receiver operator characteristic; AUC, area under curve; CI, confidence interval

FIGURE 6

Photographs of erythema before and after the transparent disc method by ultraviolet dermal camera (Left) and those image diagrams (Right) at 0.5 and 72 hours after decompression. Blanchable erythema (^*), non‐blanchable erythema (#) that disappeared later were observed within the range of pressure injury wounds in two groups. The ulcer formation (×) within non‐blanchable erythema was observed at 72 hours after decompression in the DU group. SH, spontaneous healing; DU, deteriorate to ulcer

FIGURE 7

Pressure injury (PI) skin temperature of the SH and DU group at different time points. The skin temperature of the PI wounds in both groups fluctuated during 0.5 and 72 hours. ^* P < .01. SH, spontaneous healing; DU, deteriorate to ulcer