This study will compare the NPWT using the NPD to the conventional wound dressing and specifically evaluating (i) reduction of wound surface area and depth, (ii) removal of slough and formation of granulation tissue

Initial debridement of slough and necrotic tissue was performed in all patients at the time of admission and before their being allocated in a group.

it's 3 groups:

Group (A): conventional dressing :

acting by:preventing pus, the findings from the review indicate that decreasing frictional forces transmitted to the patient's skin is achieved by use of a dressing with an outer surface made from a low friction material.

The surface of the PU will be cleaned with normal saline and packed with sterilised gauze to cover the wound. Dressing changes will be performed once or twice daily depending on the soakage of the dressing.

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Group (B), negative pressure wound therapy using the electronic-vac :

It is believed that the negative pressure assists in removal of interstitial fluid, decreasing oedema, increasing blood flow and reducing tissue bacterial levels, in addition, mechanical deformation of cells is thought to result in protein and matrix molecule synthesis, which increases the rate of cell proliferation and granulation tissue formation, this , in turn , may promote healing .

We will place a nonadherent contact layer, such as Xeroform between prepared wound bed and foam then applying a contact dressing with sealling using an adhesive drape. The dressing will be connected to the machine through tubing that was connected to the canister. Continuous pressure of 200 mm Hg will be applied. The dressing will be changed three times a week Group (C), negative pressure wound therapy using the Romo-vac: The NPD will be applied as a bedside procedure with a low-power continuous suction apparatus. We will Place nonadherent contact layer, such as Xeroform between prepared wound bed and contact dressing with sealling using an adhesive drape. The dressing will be connected to the Romo-vac which applying pressure of-60 to -125 mm Hg. The Romo-vac will be recharged every 5-6 hours and the dressing will be changed three times a week or earlier if there is a soakage/leakage

Inclusion Criteria:

Stages three and four PU as defined by the National Pressure Ulcer Advisory Panel (NPUAP).

Exclusion Criteria:

• wound with necrotic tissue unlikely to tolerate debridement. Exposed Vessels, Nerves and or organs. Active bleeding. Ischemic limb. Opening into body cavity

Based on determining the main outcome variable, the estimated minimum required sample size is 39 patients (13 patient in each group