Is Noncontact Normothermic Wound Therapy Cost Effective for the Treatment of Stages 3 and 4 Pressure Ulcers?

Alex Macario, MD, MBA;1 Franklin Dexter, MD, PhD2

We included only controlled trials that were at least four weeks in duration and required that each trial include at least one of the outcome measures described by Price.35 These efficacy endpoints include percentage of patients healed, percentage change in wound area, absolute change in wound area, total area healed, or rate of complete wound healing. Data extraction was performed by the lead author. The following study characteristics were recorded: first author’s name, year of publication, and country of origin; mean age, age range, total number, and gender of patients; presence of coexisting disease; design details, including blinding (open, single, or double) and type of control treatment; and study duration.
     The incidences of progressing through the health states were estimated from these articles and converted to bimonthly transition probabilities (Table 1 for stage 3 pressure ulcer and Table 2 for stage 4 pressure ulcer). Given the small number of studies on NNWT, sources of progression data to describe the probability of transition were limited. When there were no empirical data to base transition probabilities, we made estimates based on the available data.

     Wound healing endpoint. In the Markov model, we used the probability of wounds healing after eight weeks of therapy as the efficacy measure. These probabilities were estimated based on results of studies summarized in Table 5. Since not all studies included this endpoint, we also analyzed absolute percentage change in wound area differences. For example, if the experimental group of patients receiving NNWT healed 50 percent of the wound after eight weeks while the control group healed 20 percent of the wound, we assumed that healing was 2.5 times (50%/20%) faster with NNWT.36 We averaged these healing rates across the three studies that did have this endpoint, weighting them for number of patients enrolled (see sensitivity analyses below for addressing variation in healing rates among studies).

     The model we developed reflects that lower-stage (superficial or partial-thickness pressure ulcers) have more rapid improvement than do higher-stage (deep or full-thickness pressure ulcers).37–39 Healing rates for older (greater than one year) wounds are unavailable in the literature. We did not include an operative cure (i.e., surgical reconstruction with muscle or cutaneous flaps) in the model as more consensus is needed to develop criteria for selecting those individuals most likely to benefit from surgical management.40

     Measurement of costs. We used a “bottom up” cost methodology to estimate direct medical costs for wound care treatment and complications using data gathered from the literature. Cost of treatment included all costs for treating patients as they progressed through the health states until the ulcer healed or the hypothetical patient died (Table 3). Costs related to nursing were computed by including time per dressing, total nursing time per day, and average cost per nursing hour.


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