| Chronic wound is a very common clinical problem, and with other difficult-to-manage wounds continues to be a treatment challenge. Dressing change is the only option for compromised and debilitated patients who are unfit for surgery. As we know, chronic wounds usually result from local factors, such as ischemia and infection, that impaire wound healing. The only way to achieve successful closure of the wounds is by control of these local factors: correction of ischemia and hypoxia, control of infection. The basic foundation of treating wounds with occlusive dressing has been established by Winter's experimental study in 1962, and many new kinds of dressing have been applied to treat the chronic wounds. The choice among them is often bewildering because there is still no ideal dressing for all wound type. Currently, there is a great deal of intrest in potential role of growth factors, but some unanswered questions remain in clinical application, such as the optimal dosage, which growth factor is better for each wound, which vehicle is better and when is the best time to apply the growth factor. Exploring successful ways to expedite the healing of chronic wound has been the goal of wound healing researchers all over the world.Vacuum assisted closure(V.A.C.) has been a novel and efficacious therapy, developed in recent years, for the management of various wounds, including acute and chronic wounds. The V.A.C. technique entails placing a sterile, open-cell sponge or foam dressing into the wound defect, sealing the wound site with an adhesive drape, and appyling negative pressure that is transmited to the wound in a controlled manner. Two kinds of negative pressure dressing(NPD) are commericially aviailable. One is patented to doctor Fleischmann, and the other is to doctor Argenta. Clinical applicational studies have showed that V.A.C is effective for the management of acute and chronic wounds, particularly for these wounds that are highly exudative and serious infected, or have exposed tendon or bone, the healng rates of acute and chronic wounds were increased significantly by V.A.C. system. Further investigation about the exect mechanism should be performed because there is a lack of experimental study regarding the ability and mechanism of negative pressure to enhance wound healing, and also, there are many problems existed in clinical application and experimental studies. First, the most immportant factor in the V.A.C technique is obviously the pressure applied to the wound, but the pressure used by Fleischemann is quite different from the pressure recommended by Morykwas. Fleischmann uses 450 to 600mmHg negative pressure for treating acute and chronic wounds, but Morykwas has suggested in both animal and human studies that a negative pressure of between 75 to 125mmHg should be used to maximise tissue perfusion. Second, Morykwas and Genecov only use acute cutenuous defect and bacterial polluted wound as the animal model, but the majority of chronic wounds are granulation wound and often infected in clinical practice. No article has appeared in the literatureabout whether negative pressure could increase blood flow in the granulation wound and facilitate bacterial clearance in the infected wound. The third question is that there is a lack of direct evidence concerning the mechanism of negative pressure accelerating cell proliferation and wound healing. Morykwas and Genecov just study the effects of negative pressure on blood flow, bacterial clearance, granulation tissue formation and skin graft donor site re-epithelialization in their research papers.On account of these questions, the aim of this study was to design a new vacuum assisted closure system, determine the effects of Negative pressure on wound healing and investigate its mechanism at the cell level, and finally observe its therapeutic efficacy. The V.A.C. technique entails sealing the wound site with an negative pressure dressing(NPD) designed by our department, and applying a controlled negative pressure transmited...
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