The Use of Negative Pressure Wound Therapy with Bio-Dome™ Dressing Technology

Abstract
Over the past several years, the discussion on negative pressure has been about the debate regarding the gauze vs. the foam interface; however, there is now another interface that utilizes Bio-DomeTM technology. This wound dressing is comprised of non-woven polyester layers joined by a silicone elastomer with a non-adherent contact surface. This contact surface contains numerous Bio domesTM, which were designed to provide maximal tissue microstrain with the use of low, safe levels of suction at -75 mmHg. The non-adherent interface was designed to minimize pain, bleeding and tissue disruption upon dressing removal. The use of lower level of negative pressure has been well documented in the literature to be effective in the treatment of pediatric wounds, skin grafts and sternal wounds.

Introduction
Negative Pressure Wound Therapy, or NPWT, is a wound treatment that uses subatmospheric pressure to remove fluid from the wound bed and assist in wound healing. The benefits of NPWT have been widely documented in the clinical literature1. With proper wound assessment and technique, NPWT use is accepted for a wide variety of acute and chronic wounds1,2. Historically, there was an awareness that healing of all types of chronic, acute and post-surgical wounds is enhanced by negative pressure therapy. These principles led to the development of several types of NPWT systems3. For example, in 1985, Katherine Jeter, Ed.D, ET put together a system of products that was used to apply negative pressure to wounds. In 1989, Drs Jeter and Mark Chariker published a clinical study that supported the use of NPWT in wound care4. Further evaluation on the mechanism of action of NPWT by
Morykwas et al5. in 1997 summarized the results of a series of basic animal studies. More recently in 2007, Hunter, Teot, et al.6 published a review of the existing evidence for one particular NPWT system. They summarized that the mechanisms of action of NPWT include: creation of a moist wound environment6,7; physical stimulation of a biologic response2; potential to increase perfusion6; removal of exudate and potential reduction of edema6,7; possible alteration of wound fluid composition6 and assistance in granulation tissue formation6. In a 2006 consensus statement on NPWT, Andros et al.7 included possible control of bacterial burden in the wound in their list of mechanisms of action.

The Engenex® Advanced NPWT System provides for controlled application of sub-atmospheric pressure to a wound. It features the unique Bio-Dome™ family of wound dressings. There are several types of non-adherent EasyRelease™ dressings available, including Double-Sided Thin and Tunnel dressings. The Engenex® Advanced NPWT System is intended for the application of negative pressure between -30 and -75 mmHg to wounds to promote wound healing and for the removal of fluids, including wound exudate, irrigation fluids, body fluids, and infectious materials.

The dressing was also designed to optimize 5-20% microstrain8 at the surface of the wound, while providing unobstructed tissue growth with less dressing integration into the wound9. The Bio-Dome™ technology provides material that is anisotropic, meaning it has different collapse rates across its three principal directions. This differential collapse may aid in delaying closure along undesirable axes. For example, in a large midline abdominal dehiscence, the principal closure direction will be perpendicular to the incision and not along the incision.

Other benefits of this system include additional dressing offerings such as the Tunnel dressing and Double Sided Thin for undermining.

The therapy unit has additional benefits such as providing therapy in the presence of minor leaks, the tracking of patient compliant hours and the identical system for the hospital and home care. These are important features for the clinician to ensure the patient receives the therapy prescribed.

Clinical Outcome Case Study example:
The EasyRelease™ dressing was designed to optimize the tissue strain at the surface of the wound while providing unobstructed tissue growth with less dressing integration into the wound8. In this case the device was used to stabilize bioengineered tissue after burn scar excision10.

Patient:
Seven year old healthy male, 3 years status-post flame burn to right axilla with limited range of motion (ROM) of right arm due to scar contracture. See (Figures 1, 2).

Clinical Objective:
To improve the patient range of motion followed by releasing the scar contracture. This was followed by 12-18 weeks of physical therapy after healing.

Initial Wound Treatment:
The initial wound treatment included taking the patient to surgery to release the scar contracture, which resulted in an excision that needed a skin graft replacement to cover over the resultant defect. (Figure 4).

Engenex Initiation:
The scar release resulted in a large wound, which was treated with a dermal regeneration template and a skin graft to cover the defect.

The Engenex® System with the Opti-Flow™ Tube Attachment Device was applied to stabilize the graft site.

Wound Progress:
The Axilla can be a difficult site to immobilize and getting a good seal can be a problem. The Engenex® system was applied for 7 days along with a silver dressing to avoid infection as these types of wounds can be easily infected. (See Figure 8)

Patient Discharge and Follow-up:
The Engenex® system was discontinued with good skin graft take. The patient did not experience any pain and the system was well tolerated in a very painful wound type.

The graft is demonstrated at 4 months follow-up with good range of motion (Figure 9) and at 8 months follow-up post graft with no break down and maintenance of excellent range of motion. (Figure 10)

Conclusion:
In conclusion, the Engenex® Advanced NPWT System provides additional advantageous features over current systems on the market that utilize foam and gauze. The unique design of its dressing system with its non-adherent contact surface allowed for less pain and tissue disruption upon dressing application and removal. The dressing designed also allows for additional safety and quality of life benefits for the patient along with additional dressing to treat difficult wounds. This interface was designed to work at lower pressures with comparable levels of microstrain.

Areas that are difficult to immobilize and obtain a good seal, such as the Axilla, neck and groin can be a significant problem when utilizing NPWT. The Engenex® system performed well in this case report and some of the unique features of this system were very beneficial in this difficult to heal location. The system is designed to continue delivering the prescribed levels of NPWT in the face of small manageable leaks, which is imperative in these difficult to treat areas, helping to avoid premature discontinuation of therapy or unnecessary involvement of medical personnel.

This unique Engenex® system, utilizing neither gauze nor foam, provides an excellent alternative in providing NPWT with numerous clinical and logistical advantages over many of the current systems available on the market today.