The Effect of Vacuum-assisted Closure on the Tissue Oxygenation of Venous Ulcers: A Pilot Study
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Abstract: Background. Vacuum-assisted closure (V.A.C.® Therapy, KCI, San Antonio, TX) has been widely used to increase the healing rate of a variety of wounds. It has been hypothesized that one of the actions of VAC is to increase perfusion and subsequent oxygenation of tissue. The aim of the present study was to investigate the effect of VAC therapy on transcutaneous oximetry measurements (TCOM) of skin surrounding chronic venous ulcers. Methods. This was a prospective, experimental pilot study. Patients undergoing compression therapy were recruited from a community wound clinic. All patients had ankle-brachial pressure indices (ABPI) > 0.8. Three TCOM values were taken from around the ulcer and a reference TCOM was taken from the chest. Negative pressure was applied on the ulcer at 125-mmHg continuous subatmospheric pressure and four-layer compression bandaging over the VAC drapes. The duration of the study was 6 days. On day 6, dressings were removed and TCOM was repeated at the same skin sites. Results. Fourteen of the 17 patients completed the trial. The median age was 73 years (range 49–85). No significant difference was found in oxygen partial pressure pre-and post-VAC therapy around the ulcer site (mean 41.5 mmHg versus 40 mmHg [P = 0.67]). There was a significant difference in TCOM between the reference point and the periwound area (mean 60.5 versus 40 [P < 0.0005]). Conclusion. This pilot study suggests that VAC therapy does not change oxygen partial pressure around venous ulcers. TCOM of the skin around ulcers were low despite normal ABPIs.
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The etiology of chronic venous ulceration is not fully understood. The pathway from venous insufficiency to ulceration remains a debatable issue. Both the fibrin cuff1 and the white blood trapping theory2 have tissue hypoxia in the microcirculation as a common denominator. Hypoxia impedes wound healing by decreasing fibroblast proliferation, collagen synthesis, and angiogenesis.3,4 Transcutaneous oximetry (TCOM) is a simple, noninvasive tool to measure tissue oxygenation.5 This technique avoids the risks of invasive measurement such as tissue disruption around the wound, infection, and exacerbation of nonhealing lesions. TCOM estimates tissue oxygenation by measuring the diffusion of extracellular oxygen flowing through a heated sensor on the skin. This measurement, which is expressed in millimeters of mercury (mmHg), corresponds to the number of oxygen molecules passing from the superficial skin capillaries through to the epidermis.6
Vacuum-assisted closure (VAC) in the form of topical negative pressure (TNP) has been used for more than a decade to manage open wounds in a variety of clinical settings. Early studies by Morykwas et al7 on swine models revealed that regional blood flow, bacterial clearance, and granulation tissue formation were increased by subatmospheric pressure therapy. Several other studies using animal models have been conducted and confirm those preliminary results.8–10
To date, there have been no reported studies that use TCOM to measure the tissue oxygenation response from topical negative therapy. The aim of this study was to investigate the effect of VAC on transcutaneous oxygen in patients with venous leg ulcers.
Materials and Methods
Participants. This was a prospective, noncomparative pilot study. Patients with chronic venous leg ulcers (CEAP, C6) of more than 6 weeks duration undergoing compression therapy for at least 2 weeks in a community specialist wound care clinic were invited to participate in the study.
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