Bruin Biometrics LLC Logo
Bruin Biometrics LLC Logo

Introducing the Detection, Treatment and Prevention Effects of Sub-Epidermal Moisture Assessments

Clinical Background Summary

Circle Bullet

Biocapacitance; an electrical property of tissue; a biophysical measure of changes in localized oedema also known as sub-epidermal moisture. Sub-epidermal moisture is also described as localized edema or persistent focal edema (LO/PFO). The concept of sub-epidermal moisture is proven in the published literature.

Circle Bullet

Tissue biocapacitance increases when sub-epidermal moisture levels increase as a result of a localized inflammatory response triggered due to a developing Pressure Injury; this is non-visible tissue damage.1

Circle Bullet

SEM assessment technology is used to detect skin changes which precede and predict later-stage tissue death, including stage 1 and 2 (blisters) and deep tissue injuries during the whole episode of care from admission through to discharge.

Circle Bullet

Treating nonvisible tissue damage, as indicated by raised levels of sub-epidermal moisture, when the damage is subclinical, is timely and clinically more effective in keeping the skin intact and preventing pressure injuries and deep tissue injuries as opposed to waiting until visible damage occurs.

For more information, visit the introduction to pressure injuries and sub-epidermal moisture pages

Introducing the Detection, Treatment and Prevention Effects

Bruin Biometrics has invested in a sustained clinical research programme which has resulted in >150 overall publications, of which >70 are peer-reviewed, including four systematic reviews and a meta-analysis of the real-world data.

These studies now describe three distinct effects of sub-epidermal moisture assessment technology: the detection effect (early detection of localised edema or persistent focal edema via raised SEM deltas (∆), regardless of skin tone), the treatment effect (anatomy specific treatment of localised edema or persistent focal edema) and the prevention effect (reduction in pressure injury and deep tissue injury incidence in all population types).

The Detection Effect

Raised levels of sub-epidermal moisture indicate localised edema or persistent focal edema that is developing at the specific anatomy, a condition that requires treatment. This clinical insight allows for early detection of raised sub-epidermal moisture deltas (∆) 5 days* earlier than visual and tactile skin assessment2 regardless of skin tone.3 SEM assessment technology detects, measures and monitors levels of sub-epidermal moisture (localized edema or persistent focal edema).4

The onset of pressure-induced tissue injury occurs at a microscopic cellular level. Inflammatory pathways triggered due to this damage then contribute to the development of localized edema or persistent focal edema6,7. The North American ICD-10 coding for a stage 1 pressure injury (Code L89) describes this condition as ‘pre-ulcer skin changes limited to persistent focal oedema8. The contemporary understanding, therefore, is that localized edema or sub-epidermal moisture, is one of the earliest indicators of pressure-induced cell damage9,10,11.

Provizio® SEM Scanner detects and measures this localized edema or sub-epidermal moisture. Brunetti et al4 validated the ability of the device to measure and detect microscopic sub-epidermal moisture changes in a novel ex vivo porcine soft tissue model of localized oedema. When tissue fluid, representative of an oedematous condition in response to early subdermal pressure injury damage, was induced in an ex-vivo porcine skin model, sub-epidermal moisture delta (∆) values correlated with observed healthy tissue and induced localised oedematous tissue in an ex vivo model. Localised fluid volumes above 1 ml result in statistically significant differences in sub-epidermal moisture values between experimental (induced oedema) and control sites (healthy tissue).

These results in addition to bench studies and clinical studies describing the algorithms of sub-epidermal moisture assessment technology, align with the theoretical frameworks laid down in the aetiology chapter of the international clinical practice guidelines for pressure injury prevention in that the device is able to quantify localized edema/persistent focal edema or sub-epidermal moisture, a pathophysiological consequence of pressure-induced damage occurring at the cellular level.

Results from these studies demonstrate the ability of sub-epidermal moisture assessment technology in detecting and measuring localized edema/persistent focal edema or sub-epidermal moisture. These subdermal fluid volumes are not visible until greater fluid volumes are locally present. These data show that skin and tissues absent of visual or tactile symptoms of damage, but which have an SEM delta (Δ) above the clinical threshold (SEM delta (Δ) ≥0.6) are locally oedematous, indicating the development of early pressure-induced tissue damage, which, when left untreated may develop into more severe broken skin pressure injuries or deep tissue injuries.

Outcome: The Provizio® SEM Scanner can be used to detect, monitor, and measure sub-epidermal moisture

The Treatment Effect

The treatment effect is described as the impact of using the technology in daily pressure injury care practices enabling clinicians to detect more of the right patients who will go on to develop a pressure injury unless they are intervened on. Raised SEM deltas (∆) should indicate localized edema as a “condition” that requires treatment and are a prompt for clinical action12. Treat a raised SEM delta (∆) value as per a stage one pressure injury, this will achieve reduced SEM deltas (∆)13,14,15.

Byrne et al13 conducted a quasi-experimental controlled study to investigate the impact of sub-epidermal moisture measurement and targeted pressure injury prevention, versus visual skin assessment and usual care, on mean SEM delta (∆) values and early pressure injury development in acute hospital patients. Study results showed that following the introduction of SEM guided targeted treatments, participants in the treatment group yielded a statistically significant reduction in mean SEM delta (∆) values (P < .0001), and on the odds of developing a SEM pressure injury (P =.05). There was a greater reduction in mean SEM delta scores among those cared for using sub-epidermal moisture measurement and targeted pressure injury prevention, versus those cared for using visual skin assessment and usual care, and the mean SEM delta (∆) values was statistically significantly lower at the study end for those who received targeted treatments based on abnormal SEM delta (∆) values. This treatment effect is significantly evident in real world settings where the device was deployed alongside existing standards of care. In 69% of patients, nurses reported that the SEM delta (∆) value had changed their clinical decision making (22 sites; 1,591 patients scanned) and 72% of patients received additional interventions based on SEM delta (∆) readings (27 sites; 1,830 patients scanned).14

This data was further explored by Ousey et al12,15 in their meta-analyses. Results from this analysis demonstrated that an SEM delta (Δ) prompt was a more decisive call for action than skin reddening: in cases where a high SEM delta (Δ) reading (i.e., ≥0.6) but no skin reddening was recorded, 34.8% (2829/8141) of cases resulted in nurse action, compared with 29.7% of cases (114/384) in which skin reddening was observed but no SEM delta (Δ) prompt was reported.

When a raised SEM delta Δ (≥0.6), is detected by using the device, clinicians should be trained to treat the specific anatomy as if it were a visible stage I pressure injury (skin redness). The Interventions that subsequently follow this clinical action treat the detected increased level of localized edema (persistent focal edema or SEM) condition and subsequently prevent the incidence of broken skin pressure injuries. When the scanner was implemented alongside existing standard pressure injury care pathways a statistically significant 3-fold decrease in risk of pressure injury incidence post-implementation of SEM assessment technology was reported in 28 global facilities (RR=0.38; 95% CI: 0.26 – 0.56; p<0.001).

Outcome 1: Treat raised levels of sub-epidermal moisture as you would treat a stage 1 pressure injury based on your facility protocol.

Outcome 2: Anatomy specific data informs clinicians to treat raised SEM delta (Δ) values with known interventions before visible signs of tissue damage on the skin surface.

The Prevention Effect

Treating raised SEM deltas (∆) with known interventions results in reduced SEM delta (∆) values (reduced risk of developing pressure injuries)13. Monitor the impact of your treatment actions and review your care plan (figure 1). This will achieve consistent pressure injury incident reductions at scale in all care settings14.

A number of supporting papers are outlined here: this is not a complete list; refer to the Evidence page for more information

1. Raizman et al (2018)16 conducted a consecutive series study of 284 patients with the objective to evaluate the clinical utility of the SEM assessment technology. The authors concluded that use of the SEM assessment technology to influence clinical interventions resulted in a 93% decrease in HAPI and the Hawthorne effect did not influence the improvements in pressure injury incidence.

2. A real-world case series of 35 patients on a single medical-surgical unit over a two-month period was conducted to evaluate the impact of the SEM assessment technology use for early pressure injury detection on clinical outcomes. When compared to risk assessment tools, several patients were assessed to be “at-risk” by the tools, but their sub-epidermal moisture delta (∆) values indicated no damage was present. The authors concluded that daily scanned proved to be a more effective method of assessing damage objectively as opposed to using visual assessment alone.17

3. A formal, repeatable, pragmatic framework (a study framework designed to mimic routine clinical care and practices in the real-world care settings) was conducted at Chelsea and Westminster hospitals in the UK18 to evaluate the impact on reportable pressure injury incidence and the healthcare practitioner experience, changes in decision making and the interventions prompted by SEM results. Six hundred and ninety-seven (697) patients were enrolled during a 6-month period in 4 different wards. Zero pressure injuries were recorded in three wards resulting in an 81% incidence (p=0.011, 95%CI: 0.38-1.77) reduction across all four wards. Improved clinical decisions from clinical judgement based on SEM data were reported in 83% patients (n=578/697).

4. Roper R19 undertook a 6-week Improvement project comparing the impact on pressure injury incidence and use of Dynamic Therapy Systems. Two pathways were implemented in 7 wards – the first included SEM assessment technology into the standard of care and the second utilized a newly developed equipment pathway. The SEM assessment technology wards (n=2) achieved zero hospital acquired pressure injuries and a 100% reduction in pressure injuries relative to prior year with 75%/79% of patients changed the clinical decision making of the staff introducing additional interventions with 33%/11% reduction in dynamic therapy usage sustained for 6 weeks post project. Whilst the equipment pathway wards (n=5) achieved zero hospital acquired pressure injuries and an 86% reduction in pressure injuries relative to prior year with 64% reduction in dynamic therapy usage for 2 wards, however this was not sustained post project and a 40% increase in 3 wards sustained post project. Roper also estimated potential cost savings of £1,204,708 offset against device purchase related to reduction in spend for dynamic therapy systems, reduction in staff time, cost of dressings, medication, and occupied bed days.

5. Scafide et al20 published a full systematic review of bed side accessible technologies including: ultrasound (n=5), thermography (n=7), Sub-epidermal moisture (n=5), reflectance spectrometry and Laser Doppler (n=1). There is significant detail in the publication with regard to the outcomes of the 5 Sub-epidermal moisture publications included in this evaluation, these publications include 581 patients. The authors state that “evidence from our review supports the use of Sub-epidermal moisture measurement as a potential tool for the early identification of pressure injuries”, they go onto comment that “a body of research regarding SEM measures, which includes multiple, high-quality studies increases the reliability of our findings identified in our review”. They also point out the value in darker skin toned patients.

6. Chaboyer et al21 published an independent systematic review to analyze studies that reported the association between oedema measurement and pressure injuries. The rapid systematic review design, quality assessment methodology, GRADE assessment and reporting of meta-analyses uses globally peer reviewed and accepted frameworks. The systematic review showed a strong association between oedema, as a prognostic indicator, and pressure injuries incidence (sacrum and heels) using the SEM assessment technology. Evidence suggested that an abnormal SEM delta (∆) (≥0.6) results in a large increase in the risk of developing pressure injuries and that an abnormal SEM delta (∆) (≥0.6) is a strong indicator of a pressure injury occurring 4 to 5 days later.

7. Mersey Care Foundation Trust, UK22 successfully integrated the technology into every day clinical practice as part of patient’s individual holistic assessment. During their pilot study period, improved clinical decision-making, early implementation of standard of care interventions as a direct result of SEM delta (∆) readings, resulted in a reduction in community acquired pressure injury incidence of 26.7%. The impact of this pilot analysis enabled MCFT to directly correlate implementing SEM assessment technology to their pressure injury incidence reduction objectives.

8. Raine23 implemented the technology in palliative care (Marie Cure Hospices, UK). The 6-month study period resulted in a 47% reduction incidence rates. Post-study conclusion, patient safety incident reports indicated a consistently decreasing pressure injury incidence rate after fully implementing the device into routine clinical practice. Facility nurses reported a 69% pressure injury incidence reduction in year one of implementing SEM assessments in routine clinical care: 15 months post-study completion. During a period of 6 months in 2020 (year two, pre-COVID-19), a 100% pressure injury incidence reduction was demonstrated for several months.

9. Lustig et al24 developed a novel machine learning algorithm for early detection of heel deep tissue injuries, which was trained using a database comprising six consecutive daily sub-epidermal moisture measurements recorded from 173 patients in acute and post-acute care settings using the SEM assessment technology. On observational analysis of the database the “acceleration effect” was identified – In patients who eventually developed a heel deep tissue injury, SEM delta (∆) values generally increased over time before a deep tissue injury was confirmed through a skin and tissue assessment, the SEM delta (∆) value in the day preceding the discovery of the DTI on the skin surface was typically greater than the average of the SEM delta (∆) readings in the prior measurement days.

10. Oliveira et al25 evaluated the predictive ability of sub-epidermal moisture assessment as a means of detecting early pressure injury damage development among adults undergoing surgery and confirmed early pressure-induced tissue damage in surgical patients in the operating room. Regression analysis of SEM data from 231 patients indicated, a.) the odds of developing an abnormal SEM delta (∆) was likely to increase by 45% with an increase in surgery time (p<0.05), b.) patients undergoing orthopedic surgery were 53% more likely to have an abnormal SEM delta (∆) than non-orthopedic surgery patients (p<0.05), c.) patients having spinal anesthesia were twice as likely to develop abnormal SEM delta (∆) (p<0.05), and, d.) the Braden and Waterlow mobility scores were associated with high sub-epidermal moisture results (p<0.05).

11. Moore et al26 conducted a systematic review to analyze all quantitative animal and human studies that focused on early detection of pressure injuries and studies that reported the association between oedema measurement and pressure injuries. Early detection of pressure injuries using SEM measurement versus VSA was statistically significant; up to 8 days earlier with a median of 4.6 days (95% CI 3.94, 5.28, p<0.05)- this mirrors the results from the earlier study by Okonkwo et al. Sensitivity ranged from 48.3% to 100% while specificity ranged from 32.9% to 83%, the mean sensitivity across four reviewed studies was 72.07%. The mean specificity was 51.96%.

12. Osborne et al27 evaluated 140 adult patients admitted to a critical care unit (CCU) over a 24-week period with a majority of admitted patients being African American with varying skin tones. Pre implementation HAPI incidence was 8.9% (N= 8/90). A 100% reduction in hospital acquired pressure injury incidence was achieved in the implementation period which included 35 African American patients (p<0.05). The relative risk of pressure injury incidence was 1.6 times higher in the pre-implementation group period (95% confidence interval).

Outcome 1: Raised levels of SEM/LO/PFO when left untreated, results in more severe pressure injuries.

Outcome 2: Implementing SEM assessment technology results in up to 100% reduction in hospital acquired pressure injury incidence in multiple care settings.

1. Gefen, A., et al. (2020). Update to device-related pressure ulcers: SECURE prevention. COVID-19, face masks and skin damage. Journal of Wound Care Vol 29, No 5.
2. Okonkwo, H., et al. (2020). A blinded clinical study using a subepidermal moisture biocapacitance measurement device for early detection of pressure injuries. Wound Repair Regen.
3. Bates-Jensen, B. et al. (2009). Subepidermal Moisture Is Associated with Early Pressure Ulcer Damage in Nursing Home Residents With Dark Skin Tones. Journal of Wound, Ostomy and Continence Nursing, 36(3), pp.277-284.
4. Brunetti, G., et al. (2023). Validation of a sub-epidermal moisture scanner for early detection of pressure ulcers in an ex vivo porcine model of localized oedema. Journal of Tissue Viability.
5. Reddy, NP., et al. (1981). Interstitial fluid flow as a factor in decubitus ulcer formation. J Biomech. 14(12):879-81.30.
6. Oomens, CW, et al. (2015). Pressure induced deep tissue injury explained. Ann Biomed Eng. 43(2):297-305.
7. Oomens, CW, et al. (1987). A mixture approach to the mechanics of skin. Journal of Biomechanics. 20(9):877-85.
8. World Health Organization. (Accessed 14 April 2020). International statistical classification of diseases and related health problems (10th ed). 2016.
9. Gefen, A. (2018). The Sub-Epidermal Moisture Scanner: the principles of pressure injury prevention using novel early detection technology. Wounds International, Vol 9.
10. Gefen, A., et al. (2018). An Observational, Prospective Cohort Pilot Study to Compare the Use of Subepidermal Moisture Measurements Versus Ultrasound and Visual Skin Assessments for Early Detection of Pressure Injury. Ostomy Wound Manage, 64, 12-27.
11. EPUAP/NPIAP/PPPIA. (2019). European Pressure Ulcer Advisory Panel, National Pressure Injury Advisory Panel and Pan Pacific Pressure Injury Alliance. Prevention and Treatment of Pressure Ulcers/Injuries: Clinical Practice Guideline. The International Guideline. EPUAP/NPIAP/PPPIA.
12. Ousey, K., et al. (2022). Sub-epidermal moisture assessment as a prompt for clinical action in treatment of pressure ulcers in at-risk hospital patients. J Wound Care, 31, 294-303.
13. Byrne, S., et al. (2022). Sub epidermal moisture measurement and targeted SSKIN bundle interventions, a winning combination for the treatment of early pressure ulcer development. International Wound Journal.
14. Bryant, R. A., et al. (2021). Clinical Profile of the Sem Scanner – Modernizing Pressure Injury Care Pathways Using Sub-Epidermal Moisture (Sem) Scanning. Expert Rev Med Devices, vol. 18, no. 9, pp. 833-47.
15. Ousey, Karen et al. (2022). Sub-Epidermal Moisture Assessment as an Adjunct to Visual Assessment in the Reduction of Pressure Ulcer Incidence.” Journal of Wound Care, vol. 31, 208-16.
16. Raizman, R., et al. (2018). Utility of a sensor-based technology to assist in the prevention of pressure ulcers. A clinical comparison. International Wound Journal. 15 (6) 1033-1044.
17. Smith, G. (2019). Improved clinical outcomes in pressure ulcer prevention using SEM Scanner. Journal of Wound Care. 28;5.
18. Nightingale, P., et al. (2021). Evaluating the Impact on Hospital Acquired Pressure Injury/Ulcer Incidence in a United Kingdom NHS Acute Trust from Use of Sub-Epidermal Scanning Technology. J Clin Nurs 30.17-18:2708-17.
19. Roper, R. (2021). The benefits of a first-generation SEM scanner versus an equipment selection pathway in preventing HAPU’s. British Journal of Nursing, Tissue Viability Supplement. Vol 30, No 15; S12-S20.
20. Scafide, K. N., et al. (2020). Bedside Technologies to Enhance the Early Detection of Pressure Injuries: A Systematic Review.” J Wound Ostomy Continence Nurs, vol. 47, no. 2, 2020, pp. 128-36.
21. Chaboyer, W., et al. (2022). Oedema as a Predictor of the Incidence of New Pressure Injuries in Adults in Any Care Setting: A Systematic Review and Meta-Analysis.” Int J Nurs Stud, vol. 128.
22. Ore, N., et al. (2020). Implementing a New Approach to Pressure Ulcer Prevention. Journal of Community Nursing, vol. 34.
23. Raine, G. (2021). Is it time to re-evaluate the inevitability of SCALE ulcers? International Journal of Palliative Nursing, Vol 27, No 9.
24. Lustig, M., et al. (2022). A Machine Learning Algorithm for Early Detection of Heel Deep Tissue Injuries Based on a Daily History of Sub-Epidermal Moisture Measurements. Int Wound J.
25. Martins de Oliveira, A. L., et al. (2022). Sub-epidermal moisture versus traditional and visual skin assessments to assess pressure ulcer risk in surgery patients.” Journal of Wound Care vol. 31,3:254-264.
26. Moore, Z., et al. (2022). Measuring subepidermal moisture to detect early pressure ulcer development: a systematic review. Journal of Wound Care, 31, 634-647.
27. Osborne Chambers, C., et al. (2024). Shedding new light for nurses: Enhancing pressure injury prevention across skin tones with sub-epidermal moisture assessment technology. Journal of Advanced Nursing, 00, 1–12.

Modernize your care pathway

Contact Arjo, our exclusive Global Distributor

Alternatively, get in touch with Bruin Biometrics
[email protected]

Stay up to date with the latest pressure injury prevention developments

"*" indicates required fields