The correlation between sub-epidermal moisture measurement and other early indicators of pressure ulcer development—A prospective cohort observational study. Part 1. The correlation between sub-epidermal moisture measurement and ultrasound

The correlation between sub-epidermal moisture (SEM) and other early indicators of pressure ulcer (PU) development is yet to be determined. This three-part series aims to bridge this knowledge gap, through investigating SEM and its correlation with evidence-based technologies and assessments. This article focuses on the correlation between SEM and ultrasound. A prospective cohort observational study was undertaken between February and November 2021. Patients undergoing three surgery types were consecutively enrolled to the study following informed consent. Assessments were performed prior to and following surgery for 3 days at the sacrum, both heels and a control site, using a SEM scanner and high-frequency ultrasound scanner (5–15 MHz). Spearman's rank (rs) explored the correlation between SEM and ultrasound. A total of 60 participants were included; 50% were male with a mean age of 58 years (±13.46). A statistically significant low to moderately positive correlation was observed between SEM and ultrasound across all anatomical sites (rs range = 0.39–0.54, p < 0.05). The only exception was a correlation between SEM and ultrasound on day 0 at the right heel (rs = 0.23, p = 0.09). These results indicate that SEM and ultrasound agreed in the presence of injury; however, SEM was able to identify abnormalities before ultrasound.