The principle of operation of vacuum therapy

The dressing system for open wounds in sub-atmospheric pressure consists of the evolution of the traditional surgical procedure for the treatment of open wounds, ie the filling of the same with gauze, associated or not with a drainage. The vacuum system subjects the dressing, generally made with a polyurethane foam or gauze, to negative pressure in order to continuously remove secretions and necrotic debris that collect in the cavity, with the aim of improving cleansing and accelerating the healing process.

The key feature of this device is the application of a negative pressure, i.e. lower than atmospheric pressure, which is normally taken at sea level at room temperature, where the molecules exert a force that corresponds to a pressure of 760 mmHg. The therapeutic system usually consists of a hydrophobic, open cell polyurethane (PU) foam dressing that is introduced into the wound cavity and filled it. A semi-occlusive, transparent adhesive film is used to isolate the dressing which adheres to healthy skin around the wound allowing for visual inspection from the outside. A hole is made on the film to which a tube equipped with an adhesive disk (PAD) is connected. The tube allows communication between the wound and the suction system, which with various mechanisms can create negative pressure. A container for the collection of exudate (CANISTER) is interposed between the pipe and the system, which in turn is connected to the device.

The two types of existing systems are: portable battery-powered devices and fixed devices connected to the centralized vacuum system in the hospital. The first type is widespread on the market, there are different types and sizes. They all have in common the basic operation, characterized by the presence of an internal pump that creates the suction, a microprocessor that detects any pressure changes and signals problems and an interface and data control module (display) for use. and management by the user. They are battery-operated devices with autonomy that usually varies between 2 h and 12 h, depending on the tightness of the dressing, and which can be recharged via a cable. The second type, on the other hand, is the MINI VACUUM MV01: a precision vacuum regulator that has the functions of Topical Negative Pressure therapy for wounds. The technology behind this device is very simple as it exploits a vacuum source already existing in all hospital rooms and precisely adjusts its intensity, allowing it to be used in this application. Values ​​from -25 to -200 mmHg can be set, with different operating modes.

Even the polyurethane foam with which the lesion cavity is filled has an important mechanical function: once the negative pressure therapy is triggered, in fact, the foam contracts and, reducing its volume and still maintaining its characteristic structure honeycomb even under suction, evenly distributes the pressure on the wound bed. This allows to reduce the edema of the periwound tissues, to increase blood circulation and to stimulate angiogenesis. The contraction of the foam brings together and stabilizes the wound margins, thus providing an anchor point for the muscles and deeper structures. Furthermore, with the application of negative pressure therapy, exudate, inhibitory substances and small residues are removed from the wound, providing a suitable environment for healing.
Bibliography:

 

European Wound Management Association, documento di posizionamento: la pressione topica negativa nella gestione delle ferite, London: MEP Itd, 2007.

Henderson V, Timmons J, Hurd T, Deroo K, Maloney S, Sabo S. NPWT in
everyday practice Made Easy. Wounds International 2010; 1(5). Disponibile su: http://www.woundsinternational.com.

Morykwas MJ, Argenta LC, Shelton-Brown EI, et al. Vacuum-assisted closure: a new method for wound control and treatment: animal studies and basic foundation. Ann Plast Surg 1997; 38(6): 553-62.