Three Approaches (& Consequences) of Affixing a Medical Device to Skin

 In Engineering, Medical Product Design

There are three popular methods to hold a medical device or treatment onto the human body: tie it on, stick it on or suction it on. The first method was developed by our prehistoric grandparents to hold remedies of flora and what-have-you by tying it in place with leather thongs or twine, and today we still do the same.  Does that surprise you?

The Tie-It-On Approach: Application & User Errors

The synthetic strap has mostly replaced the thong or twine. But the strap is still the most common method of holding medical products onto our person. Without getting into the various buckles and hook-and-loop fasteners, the strap’s ease of use does still cause problems with proper fitting. With the strap’s ease to fasten and adjust, it is assumed that the user will put the device on correctly. Wrong! Users often over- or under-tighten the device’s strap, which is a huge problem. Age, grip strength, reach, personal comfort and the user’s understanding of “proper fit” will all effect the correct application.

Imagine a user over-tightening the strap and thus restricting dermal blood flow. Even light pressure over time can cause the telling red marks on the skin; just ask a CPAP user. These worrying red marks could become a sore or pressure ulcer.

Then the user may loosen the strap for the comfort. Loose straps can cause chaffing and/or allow the device to move off target thereby lengthening or preventing the therapy. A loose binding on a medical device, like a walking brace (boot) for example, could aggravate the injury — or worse. The solution lays with the health practitioner’s ability to educate the user, the user’s understanding of a proper fit (albeit even a device’s best fit is sometimes uncomfortable) and the medical product designer’s creativity to create a self-adjusting, constant-force strap.

attaching a cpap mask

The Stick-It-On Method: Injury Prevention

Another seemingly easy approach to mounting a medical device onto skin is to stick it on, i.e., use adhesive tape. Easy this approach may appear to be, but MARSI has something to say about that. MARSI is short for Medical Adhesive-Related Skin Injury. This acronym exists because it’s a big problem. The most frequent cause of MARSI is the repeated application and removal of adhesive on the same location. So common that the 3M corporation, in conjunction with medical practitioners, has created a guide on the proper application and removal of medical adhesive tape on the skin.

For the medical product designer the concern is whether a single-sided tape, double-sided tape or an aqueous adhesive will allow for proper donning and doffing of device to the adhered region. Additionally, the designer will want to use the weakest strength adhesive over the largest surface area that does the job correctly. Over designing is not better; higher strength adhesives simply require more removal force. Ouch!


The Suction Approach: Advantages & Consequences

This last anchoring means is to use negative pressure to apply the device onto skin. As an example, there is a therapy that can literally suck out wound exudate and pull the wound, thereby vastly hastening recovery. This approach is also exemplified by one of our clients who uses negative pressure as the mechanism for their sleep APNEA device. The vacuum pulls the obstructing airway tissues clear and holds the device in place all night long. And yep you wake up with temporary red marks.

Negative pressure (a vacuum) has two primary consequences on the dermal layer. The first is the red mark due to the suction that can potentially rupture sub-dermal tissues and blood vessels, i.e., create a hickey. There are a variety of skin details to take into account like durability, thickness and sensitivities when designing medical products. The health practitioner must be vigilant of the patient’s sensitivity.

Secondly, if there is a vacuum pulling on tissues, then there must be a pressure (force) pushing on tissues. This compressing of tissues is usually the device’s footing. As with strapping on a medical device, with this suction method you must be concerned about restricting dermal blood flow as well as standing on nerve bundles and pathways.

Skin Contact & Dermatitis

Regardless of the attachment method, the concern with any medical device or foreign body contacting skin is dermatitis. Dermatitis is a general term for an inflammation of the skin. Dermatitis has many causes and comes in many forms. It usually manifests as a red, swollen, itchy rash.

To understand how the end user will react to topical placement of a remediation, the health practitioner will need to interview the end-user for their past history.

In some situations, the medical device itself will dictate the means of attachment. In others, medical device designers will test various attachment methods and verify their effectiveness. Whichever your company ends up using, be aware of the consequences.


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