Macrodeformation: Macrodeformation, or simply induced wound shrinkage, occurs when suction is applied to the foam causing pore collapse. Effect of negative pressure wound therapy on wound healing. Reproduced from, Huang C, Leavitt T, Bayer LR, Orgill DP. This lattice formation allows the vacuum to be evenly distributed throughout the foam and improves fluid drainage.įigure 2 The 4 primary mechanisms of microdeformational wound therapy: (1) macrodeformation (2) microdeformation (3) fluid removal and (4) alteration of the wound environment. The most commonly used material is a reticulated open-pore polyurethane (PU) foam that forms a structure resembling a three-dimensional net. The specific interface material that contacts the wound surface affects the biological response of the system. In the variable mode, the suction level changes but is never turned off, whereas in the intermittent mode the pressure is switched on and off throughout the course of treatment. The pressure can be applied in a continuous, intermittent, or variable mode, with the continuous type being the most frequently used. The drainage port is connected to a controlled vacuum pump which maintains negative pressure, usually ranging from -50 to -150 mmHg. A drainage port is then attached above the porous material and the wound is sealed with an adhesive film dressing. In NPWT the wound is first filled with a porous material such as foam or gauze, that facilitates pressure transmission within the wound. This paper will analyze the available literature in order to summarize the current understanding of NPWT in terms of its mechanism of action, its applications, complications, contraindications and its future. Research on the application of NPWT in treating chronic non-healing wounds has largely taken the form of case studies, single-center studies, non-randomized controlled trials, with few randomized controlled trials (RCTs). The Vacuum-assisted closure (VAC) therapy system is the most commonly used commercially available device. Microdeformational wound therapy (MDWT) refers specifically to the field as applied to the science of the foam wound interface that causes deformation. Negative pressure wound therapy (NPWT) defines the entire field of wound therapy that applies differential suction to the wound. “Negative pressure” is somewhat of a misnomer as technically all pressure values should be positive.įigure 1 Visual representation of the definitions used in this article. Much of the clinical and basic science literature is based on these early devices (Figure 1). VAC now commonly refers to a family of devices using a highly porous foam based on the first commercially available NPWT device. MDWT refers to devices (generally foam) that substantially deform the wound surface. The terms Vacuum Assisted Closure (VAC, KCI, San Antonio, TX) and microdeformational wound therapy (MDWT) are sometimes used interchangeably with NPWT. In simple terms, NPWT refers to any device that tightly seals the wound creating a near airtight environment to which a vacuum can be applied resulting in a series of biological reactions that enhance wound healing. Since its introduction 19 years ago by Argenta and Morykwas, negative pressure wound therapy (NPWT) has emerged as a common treatment for acute and chronic wounds, including diabetic wounds, pressure ulcers, and burns. Overall, despite the fact that questions remain to be answered about NPWT, this technology is a major breakthrough in wound healing with significant potential use both in the hospital but also in the community. Finally, future perspectives, such as the optimal cycling of the treatment and the most appropriate interface material, are touched upon in the final segment. This therapy has various considerations and contraindications which are summarized in this review. Modifications of the traditional NPWT have also been established and are described in detail. This therapy also has many uses whose efficacy has yet to be confirmed, for example the use in digestive surgery. In addition, the technique has many established uses, for example in wound healing of diabetic and pressure ulcers, as well as burn and blast wounds. NPWT is known to affect wound healing through four primary mechanisms (macrodeformation, microdeformation, fluid removal, and alteration of the wound environment) and various secondary mechanisms (including neurogenesis, angiogenesis, modulation of inflammation, and alterations in bioburden) which are described in this review. Vacuum-assisted closure, sometimes referred to as microdeformational wound therapy or most commonly negative pressure wound therapy (NPWT), has significantly improved wound care over the past two decades.
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