Effects of Varying Levels of Subatmospheric Pressure on the Rate of Granulation Tissue Formation in Experimental Wounds in Swine

Abstract

The use of subatmospheric pressure to promote wound healing has increased in popularity during the last several years. The original studies on granulation tissue formation used a 125-mmHg vacuum. The use of alternative sources of subatmospheric pressure has led to many questions regarding efficacy or risk. In this report a swine model is used to quantify and compare the effects of low vacuum suction (25 mmHg) and high vacuum suction (500 mmHg) produced by various vacuum pumps and wall suction systems with the standard 125-mmHg vacuum. Additionally, the effects of an unregulated air leak in the sealing system were examined. All four wound treatments were examined on each of 4 pigs. Wounds were treated until one of the wounds had granulated to a level flush with the surrounding tissue. Wounds treated with the standard 125-mmHg vacuum had filled with granulation tissue by day 8. At this time wounds treated with 25 mmHg had filled 21.2% with new granulation tissue, and wounds treated with 500 mmHg had filled 5.9% with new tissue. Wounds treated with 125 mmHg with a hole in the sealing drape had increased in size 197% because of the debridement of necrotic tissue. In conclusion, wounds treated with a 125-mmHg vacuum exhibited a significant (p< 0.0001) increase in the rate of granulation tissue formation compared with treatment at 25 mmHg or 500 mmHg. The presence of an unregulated air leak in the sealing drape results in significant progression (p < 0.0001) of the wound secondary to dehydration and progressive necrosis.

Impact of negative pressure wound therapy on open diaphyseal tibial fractures: A prospective randomized trial

“…Several studies have shown intermittent pressure mode to be more efficacious compared to continuous negative pressure. 20 The wound was opened every fourth day for reapplication of dressing and swab was sent for aerobic and anaerobic culture every time the wound was opened. Once the wound had sufficient granulation tissue such that it could undergo skin grafting or the wound had contracted to such a size that it could surgically closed, it was either closed or covered with skin graft.…”

Negative pressure wound therapy (NPWT) for spinal wounds: a systematic review

“…The studies 3,26,29 reported in this review applied pressure of -125 mmHg to surgical spinal wounds. Morykwas et al 40 found -125 mmHg was associated with higher rate of granulation formation in an experimental pig model, but McCord et al 41 suggested wound healing could be achieved using lower negative pressure (-100 mmHg) in infants and children. The general consensus in the literature (mainly for non-spinal wounds) indicated a negative pressure of -50 to -75 mmHg to be used in children 2 years or younger; -75 to -125 mmHg for children above 2 and -100 to -125 mmHg is used in adult patients 42 .…”

Negative Pressure Wound Therapy in Grade IIIB Tibial Fractures: Fewer Infections and Fewer Flap Procedures?

“…Morykwas et al [41], in histologic studies regarding burns in a porcine model, described preservation of tissue with negative pressure wound therapy otherwise destined for necrosis (controls) [40]. Implied is the cascade of molecular events that occur after a thermal wound characterized by edema, impaired microcirculation, and heightened capillary afterload (reperfusion injury) with secondary necrosis and additional tissue loss [40,51,53].…”

“…In 1997, the FDA approved negative pressure wound therapy. Subsequently, animal studies [39,41] and additional clinical reports that favored negative pressure wound therapy to reduce edema, decrease bacterial loads, increase granulation tissue formation, and other pathways to promote wound healing [2,38] were published. The majority of studies however, regard chronic or diabetic wounds [5,8,18,42,43,52].…”