The Effect of Vacuum-assisted Closure on the Tissue Oxygenation of Venous Ulcers: A Pilot Study
- 9/15/2009
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Patients were diagnosed as having superficial venous incompetence with clinical examination and a hand held Doppler (Level 1 investigation).11 The inclusion criterion was venous ulcer size > 1 cm2. Exclusion criteria were ankle-brachial pressure index (ABPI) < 0.8, previous VAC therapy, current smokers, lymphedema, severe lipodermatosclerosis (LPS), recurrent ulcers, previous deep vein thrombosis or known deep venous incompetence, body mass index > 35, and presence of infected, malignant, or vasculitic ulcers. Lipodermatosclerosis was defined as “mild” if the skin around the ulcer was involved, and “moderate” if the entire ankle was affected. All subjects were ambulatory and were treated as an outpatient. All participants were provided with trial information sheets and written consent was obtained. Ethical approval was granted by the regional ethics committee.
Materials. All VAC equipment was provided by Intermed-Kinetic Concepts, Inc (Auckland, New Zealand). VAC therapy consisted of polyurethane foam (black foam) dressing with a pore size of 400 µm–600 µm, adhesive draping, and an evacuation tube connected to the VAC® Freedom or MiniVAC® system. Once the black foam dressing had been applied, therapy was commenced at 125-mmHg subatmospheric pressure continuously. Four-layer compression bandaging using the Charing Cross method (orthopedic wool, support crepe bandage, class 3a bandage plus cohesive bandage) providing 40 mmHg at the ankle graduating to 17 mmHg below the knee, was applied over the sealing drapes.12,13 Negative pressure therapy was commenced for 6 days with a dressing change on day 3.
Measurements. All TCOM were performed while participants were in a relaxed supine position breathing room air. The skin site was prepped and light desquamation was achieved using a 70% isopropyl alcohol swab. Nurses trained in the technique placed three sensors heated to 44˚C around the ulcer in the recommended manner (ie, not over prominent bones or major vessels). The reference point measurement was taken from the second intercostal space. Resting transcutaneous oxygen pressure (TcPO2) was estimated using a transcutaneous oxygen monitor (Tina TCM 4, Radiometer, Copenhagen, Denmark) and data were recorded after the readings had been stabilized for 10 to 15 minutes. Recordings were taken on days 1 and 6 in the same environment and location for each patient. Tracings on picture diagrams and markings on the limbs were drawn to ensure accuracy in subsequently placing the sensors on the same location at the second visit.
Participants had a 24-hour phone line to call if assistance with the VAC device was needed. The VAC system was checked at each visit to ensure that the seal had been maintained at -125 mmHg throughout the study period.
Statistical Analysis
The mean of the three TCOM around the ulcer for each patient was calculated. The data were entered into a Microsoft Excel database and statistically analyzed using R software (R Foundation for Statistical Computing, Vienna, Austria.) Differences in means were compared with the paired Student’s t-test; significance was determined at P < 0.05.
Results
Seventeen participants (5 men and 9 women) were recruited, of whom three did not complete the trial and were excluded from the data analysis. Two of the patients did not cope with the VAC equipment (pump and the tubing) and the other participant withdrew on the second day due to significant pain from the ulcer. The median age was 73 years (range 49–85). Sixteen participants were nonsmokers and one was an ex-smoker. One patient had undergone previous hyperbaric oxygen therapy (HBOT) for their ulcer. Five patients had moderate LDS. There were no complications encountered with the TCOM. One patient developed contact dermatitis from the sealing drape on day 6.
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