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Background/Significance: The onset of deep pressure injury in critically ill adults may not be appreciable by visual skin assessment; however, studies have shown that using HFUS, both visual image assessment and quantitative measures may identify tissue injury. HFUS images with lower densities in the dermal layer have been found to indicate edema – the initial step of tissue injury. Identifying deep pressure injury onset would allow implementation of preventative measures to ameliorate or halt pressure injury progression.
Method: Three quantitative measures (LEP:TP, mean density and thickness measurements) were extracted from HFUS images and compared with visual image assessment by a trained, experienced image evaluator. Each measure was examined in univariate and stepwise models using logistic regression with repeated measures to determine the strongest predictor of injury (yes or no). Subject age, APACHE, and BMI were included in all models as covariates.
Results: Sacral HFUS images from 117 critical care patients for up to 7 days were obtained with 478 images available for comparison; 108 images showed tissue injury (19%). The univariate analysis indicated that increasing values of all three measures were significantly related to increased odds of injury. In the combined model, median intensity was the strongest predictor for tissue injury, with mean thickness and LEP:TP ratio becoming nonsignificant. Older subjects and lower APACHE scores were significantly associated with increased odds of injury, however, BMI was not.
Conclusions: We found that median intensity was the best predictor of sacral edema and possible tissue pressure injury. Median intensity was highly correlated with LEP:TP. A quantitative measure, median intensity, obtained from HFUS images may reliably indicate tissue pressure injury.