Pathophysiology
Clinical meaning
Wound healing is a complex, dynamic process that proceeds through four overlapping phases: hemostasis, inflammation, proliferation, and remodeling. During hemostasis, platelet aggregation and the coagulation cascade form a fibrin clot that stops bleeding and provides a temporary scaffold. The inflammatory phase begins within hours as neutrophils and macrophages migrate to the wound bed, removing bacteria and devitalized tissue through phagocytosis and releasing cytokines that recruit fibroblasts and endothelial cells. The proliferative phase involves granulation tissue formation, where fibroblasts synthesize collagen and extracellular matrix while new capillaries (angiogenesis) supply oxygen and nutrients. Epithelial cells migrate across the wound surface from the edges (epithelialization). The remodeling phase can last months to years as type III collagen is replaced by stronger type I collagen, though healed tissue only reaches approximately 80% of original tensile strength. Negative pressure wound therapy (NPWT) accelerates wound healing through several mechanisms. The VAC (Vacuum-Assisted Closure) system applies controlled subatmospheric pressure (typically 75 to 125 mmHg) to the wound bed through a sealed dressing connected to a suction device. This negative pressure removes excess exudate and infectious material, reduces...