Sub-epidural Moisture (SEM) and PIs: Seeing in the Dark

sub-epidural moisture and pressure ulcers

Preventing pressure injuries often feels like flailing in the dark, trying to stop something that we don't see coming. By the time it comes into the light, it's already grown big and strong and done a great deal of damage.

By that point, we're not talking about prevention. We're talking about treatment, which is more painful for the patient and expensive for the health provider.

If only there were a way to see into the darkness and confront the burgeoning PI before it reaches the skin. If only we could start the battle under the skin, when it has yet to cause the most serious harm.

New technology measuring sub-epidural moisture (SEM) may do just that.

According to Professor Zena Moore, Head of the School of Nursing & Midwifery at the Royal College of Surgeons in Ireland, the presence of SEM is one of the earliest indicators that the PI is on way.

"Changes in SEM as a physiological marker of early PI development is an exciting opportunity for prevention," she said. "For the first time, we may actually have something that allows us to 'see in the dark.'"

The collection of moisture under the skin is one of the earliest signs that a pressure injury is forming. "These sub-epidermal changes occur 3-10 days before anything is seen on the skin surface. Once the SEM is elevated, this predicts the presence of a PI in development," she explained.

'Like a Volcano'

Too often, pressure injuries garner no attention until they burst through the skin. By then, it's too late to do anything other than to treat it.

The mistake, Prof. Moore said, is assuming that all PIs start on the outside and work down through the skin. Many start on the inside and work their way out, she said.

"Classification of PIs has its origins in burn injuries, which start from the outside and go deeper the more serious they are, in a linear progression - first an injury will go through stage 1, then 2, then 3, etc.

"The problem is that pressure injuries don’t work that way," she continued. "Stage 4 IS deeper and more serious than stage 1, but a PI doesn’t always go through stages 1 and 2 before it gets to 4.

"It’s like a volcano – it emerges from the inside out," she continued. "Once we see the damage, it’s too late."

A reliable method for measuring SEM would allow medical staff to recognize an emerging PI before they see it on the surface.

"If we were able to do this, we wouldn’t have to wait for the volcano to erupt at the skin’s surface," Prof. Moore advised. "We could, instead, recognize the impending damage that was occurring underneath and alter our strategies to prevent the PI."

SEM Scanner as Cost Saving Device

SEM Scanners are already available, with clinical trials testing their benefits and limitations in the area of PI prevention. They may well become the most effective device yet for predicting PIs. And if the injuries can be predicted earlier with significant accuracy, then many more can be prevented as well.

Any device that can provide that type of advantage might well be the most effective cost-saving device on the market. The patient’s pain and suffering, coupled with the staff time and resources that go into treating a pressure injury, can't compare with what it might cost to stop them before they start. It would be a pittance, in comparison, to prevent rather than treat.

Prof. Moore said the current literature supports the idea that "SEM measurement might be a reliable method for early prediction of tissue damage and of PI presence.

"Yes, there are PIs occurring that you cannot see, but there is something happening under the skin that can be detected with the right method of assessment!"

Looking Further and Deeper

The recognition that the PIs follow a different trajectory than other types of wounds, which usually start from the outside and work their way in as they grow in severity, opened the door for new approaches to fighting the wounds.

Now, armed with new knowledge and new technology to support it, the medical field is better equipped to step up the fight against PIs. An all-out effort could turn out decisive, if the early indicators are proven correct.

The question is - will the method gain widespread adoption? Will medical facilities change the way they battle the wounds? Will they accept the scientific research documenting activity under the skin which indicates that something significant is about to happen on the skin surface?

If the method truly proves itself, it will surely be repeated in due time throughout the medical establishment. What may be more significant is the push to see in the darkness. Getting a better handle on what's happening deep down under the skin may be the start of all kinds of new methods and new ideas.