Results of a Retrospective Comparative Study: Material Cost for Managing a Series of Large Wounds in Subjects With Serious Morbidity With a Hydrokinetic Fiber Dressing or Negative Pressure Wound Therapy

This retrospective observational study analyzed lesions with regard to healing trends and cost of materials.   Materials and Methods. The observed lesions were mostly postsurgical or stage IV pressure ulcers in patients with serious morbidity. The wounds were treated with a hydrokinetic fiber dressing (sorbion Sachet S, sorbion Gmbh & Co, a BSN medical company, Senden, Germany) (n = 26) or negative pressure wound therapy (NPWT) (n = 16). Results. Primary healing trends (ie, reduction of wound size, change from necrosis to granulation tissue, and change from granulation tissue to epithelium) and secondary healing trends (ie, periwound conditions) were similar for wounds treated with the hydrokinetic dressing when compared to wounds treated with NPWT. Cost of materials was substantially lower for wounds treated with the hydrokinetic fiber dressing compared to the NPWT, with cost reductions of $1,640 (348%) to $2,242 (1794%) per wound, depending on the criteria used for the analysis. Conclusion. In this set of wounds, the hydrokinetic fiber dressing was shown to lead to similar healing results while providing substantial reductions of the cost of materials. For the types of wounds presented in this observational study, the hydrokinetic fiber dressing seems to be an effective substitution for negative pressure wound therapy.

  Many chronic lesions are characterized by elevated production of exudate. It is well established that excessive exudate may lead to excoriation and maceration^1-3 while the large number of bacteria in exudate⁴ may also contribute to healing problems. Other aspects of chronic wound exudate, such as an increased level of certain matrix metalloproteinases (MMPs),^5,6 are also thought to contribute to wound healing problems. Consequently, exudate management has been established as a crucial part of wound care and wound bed preparation.^7,8

  There are many options available for the management of exudate, and negative pressure wound therapy (NPWT) is a popular one. Although many variations are commercially available, at its core, an NPWT device comprises a drape to keep a vacuum over the wound, tubing to connect the wound to a collection device, and a pump for the generation of negative pressure. The vacuum promotes local perfusion⁹ and assists in the removal of exudate, thus decreasing the inhibitory factors in that exudate.¹⁰ While significant price differences have been shown using different NPWT techniques and devices,¹¹ it is not possible “to identify a significant therapeutic distinction of one NPWT system or component over another through the use of head-to-head comparisons,” according to a report prepared for the Agency for Healthcare Research and Quality.¹² Thus, it seems justified to use the term NPWT to cover all different vacuum-assisted wound closure devices.

  Hydrokinetic fiber dressing (sorbion Sachet S, sorbion Gmbh & Co, a BSN medical company, Senden, Germany), the test dressing, consists of a core of modified cellulose fibers and specific gel-forming polymers. The fibers and polymers form a matrix characterized by a specific combination of these materials, including their proportions, density, and mass. They are encased in a polypropylene enveloping layer which has an expansion border, allowing for wide contact with the wound area. The dressing has been shown to assist in debridement¹³ and in the removal and containment of significant amounts of exudate with all its detrimental components^14,15 while the polypropylene enveloping layer prevents mechanical disturbance of, or detrimental chemical effects to, the wound bed.

  Based on clinical observations and evaluations of the dressing, a substantial number of similarities to NPWT was found with regard to clinical performance and patient benefits^16,17 including exudate management, and reduction of compounds harmful to the wound, such as certain metalloproteinases. It was therefore decided to initiate an observational study to analyze the cost-performance ratio between the test dressing and a specific NPWT system (V.A.C. Therapy, KCI Inc, an Acelity company, San Antonio, TX). Whether or not such cost difference was related to a superiority of the clinical performance of one modality over the other was also included in the evaluation.

  Noncontact low frequency ultrasound (NLFU) (Mist Therapy, Celleration, Eden Prairie, MN) has been shown to aid in debridement^18-20 and to reduce bacterial quantities.²¹ Noncontact low frequency ultrasound was also shown to easily remove slough in burns²⁰ and to provide better outcomes than standard care alone in venous leg ulcers.²² In this study, NLFU was used as an adjunct treatment in subjects with a significant amount (ie, > 25% of the total surface of the wound) of slough and/or necrosis.

  All subjects in this study were in a long term acute care (LTAC) facility (Vibra Hospital of Sacramento, Folsom, CA). In this type of venue an average length of stay of 25 days is allowed by Medicare, depending on the primary diagnosis upon admission. With regard to wound management, one of the major challenges of care in an LTAC facility is cleaning a wound and initiating a positive healing trajectory in a timely fashion prior to discharging the patient to the next level of care. Negative pressure wound therapy has been established as one of the ways to meet these challenges but is relatively expensive, time consuming, and painful.¹⁷

  An alternative protocol, using the test dressing in combination with a fixation material and where indicated for debridement, NLFU, was established to ascertain cost of materials and healing results.

  A chart review was used for collecting the data. Since this was a retrospective study, Institutional Review Board approval was not requested. The study started when the test dressing became available to the facility in March 2012 and the cutoff time for admission of additional subjects was April 2013, with May 28, 2013 as the date of last data entry. All subjects who were admitted with orders for NPWT were entered into the study. However, if contraindications for the use of NPWT existed (eg, pain, bleeding, or expected difficulty of the placement of the NPWT device) it was decided at the physician’s discretion not to use NPWT but the test dressing instead.

  Treatment with the test dressing and NPWT were used in line with the manufacturers’ instructions and were combined with standard wound management, including cleansing with saline (0.9%) and surgical debridement, if and when indicated.

  General demographic data (ie, subject age, sex, race, and primary and secondary diagnoses) were recorded. With regard to the lesion, data such as location, type of wound, size, and depth were collected as well as information on the amount of granulation tissue, pain experienced by the patient, and periwound conditions.

  Measurements of wound surface were performed using a ruler, measuring the largest perpendicular areas in centimeters and multiplying the numbers. Volume was calculated by multiplying the surface area with the deepest area of the wound. Since the amount of undermining and/or tunneling was relatively small compared to the overall surface and volume of the lesions, and since the volumes of undermining and tunneling are difficult to measure, these were not calculated as part of the overall surface and volume measurements.

  The cost of materials was calculated using the real life cost for the facility. For NPWT this included the daily cost of renting the device in combination with the cost of dressing materials and the canister used for each dressing change. For the test dressing, the cost of an adhesive foam material (Biatain, Coloplast, Minneapolis, MN) used for coverage was added to the cost of the dressing itself. Depending on the subjects’ cohort (ie, all subjects, all subjects with NLFU, or all subjects without NLFU) the average cost of NLFU was added for each dressing change.

 The test dressing was used to treat 23 subjects with 26 lesions (average age: 61.3 years, range: 24.0-76.0 years) and NPWT was used to treat 15 subjects with 16 lesions (average age 68.3 years, range: 43.0-85.0 years). Of the subjects in the test dressing group 15 were male; in the NPWT group 8 were male.

  In the test dressing group, 15 subjects self-identified as white, 3 subjects as African American, and 3 subjects as Hispanic. One subject was American Indian and the race of 1 subject was unknown. In the NPWT group, 8 subjects self-identified as white, 1 as African American, 3 as Hispanic, and 1 was American Indian; the race of 2 subjects in this group was not known. The types of lesions and their locations are presented in Table 1. Most lesions were either pressure ulcers or postsurgical wounds.

  The postsurgical lesions in the test dressing group included abdominal dehiscence (n = 4), and rectal area dehiscence (n = 1); postsurgical debridement for an infected diabetic ulcer (n = 1), cellulitis (n = 1), and necrotizing fasciitis (n = 2); and postsurgical debridement for an infected pacemaker site (n = 1). In the NPWT group the postsurgical lesions included dehiscence (abdomen, n = 2; sternum n = 1; leg, n = 1), postexcision and debridement lesions (necrotizing fasciitis, n = 1; sacral ulcer, n = 1), and nonhealing lesions (foot amputation in patients with diabetes, n = 3; surgical lesion in the groin, n = 1). All subjects were diagnosed with 1 or more comorbidities (Table 2).

  Noncontact low frequency ultrasound was used as an adjunct in 21 (80%) of the lesions treated with the test dressing and in 2 wounds treated with NPWT (12.5%).

  On average, subjects’ lesions were part of the study for 29.2 days in the test dressing group, (range: 7-104 days) and 27.3 days in the NPWT group (range: 8-55 days). On average, dressing changes took place 3 times per week. For all types of lesions combined, the average number of dressing changes was 13 in the test dressing group and 12 in the NPWT group.

  Because of the large difference in the 2 study arms in number of subjects treated with NLFU, and since the use of NLFU contributes to the cost of treatment, 2 subsets of data—all subjects in both groups treated with NLFU as an adjunct and all subjects in both groups without NLFU as an adjunct—were analyzed separately for healing results and cost of materials.

  General trends with regard to aspects of healing were very similar amongst the complete data set and the subsets. Thus, for the amount of exudate, the percentage of granulation tissue and epithelium, the condition of the periwound skin, and the level of pain, only the results for the complete data set are reported.

  At the start of the study, 65% (n = 17) (all percentages are rounded to whole numbers) of the lesions treated with the test dressing and 56% (n = 9) of the lesions treated with NPWT showed undermining; in addition, 1 subject in the test dressing group and 2 in the NPWT group showed tunneling. The average level of undermining and tunneling decreased for both treatments (Table 3).

  The amounts of exudate produced by the wound were rated large, moderate, scant, and small. The ratings were relative and based on the investigator’s experience. At study start, 20 (77%) wounds in the test dressing group and 4 (25%) wounds in the NPWT group produced large to moderate amounts of exudate. At the end of the study, 1 (4%) test dressing wound and 2 (13%) NPWT wounds produced a large to moderate amount of exudate, while 25 (96%) of the test dressing wounds and 14 (88%) of NPWT wounds produced small or scant amounts of exudate.

  At the beginning of the study, 23 (88%) of the test dressing lesions and 8 (50%) of the NPWT group lesions had less than 25% granulation. At the end of the study, 20 (77%) of the test dressing wounds and 11 (69%) of the wounds in the NPWT group were covered with 75%-100% granulation tissue (Table 4). None of the lesions in either study arm had any epithelial coverage at the start of the study; by the study’s end, 19 (73%) of the lesions in the test dressing group and 8 (50%) of the lesions in the NPWT group had an average wound surface area of 25%-75% covered with epithelium (Table 4).

  In both study arms, the condition of the periwound skin showed improvement at the end of the study when compared with the beginning of the study, with 97% (n = 25) of test dressing lesions and 94% (n = 15) of wounds treated with NPWT showing periwound skin with a normal, healthy appearance (Table 5).

  The average pain level at the start of the study, determined using a Visual Analog Scale in which 0 = no pain and 10 = excruciating pain, was 3.7 in the test dressing group and 0.7 in the NPWT group. The average pain scores at the end of the study period were 0.6 for the test dressing and 0.2 for NPWT, indicating an 84% and 75% change, respectively.

  With regard to healing and cost of dressings and materials the full data set (ie, the entire study population) was analyzed. Because of the differences between the 2 study populations with regard to the number of lesions for which NLFU was used as an adjunct therapy, 2 subsets were analyzed: the first subset included all lesions in both study populations treated with NLFU (test dressing group, n = 21; NPWT group, n = 2); the second subset included all lesions in both study groups treated without NLFU (test dressing group, n = 5; NPWT group, n = 14).

  For both study groups, with all lesions with and without NLFU included, the test dressing wounds were substantially larger on average at the start of the study with regard to both surface (average surface area 227.2 cm², range 15.9 cm²-1683.0 cm²) and volume (average volume 534.0 cm³, range 32.0 cm³-2386.0 cm³) than the lesions treated with NPWT (average surface area 94.5 cm², range 4.0 cm²-399.0 cm²; average volume 283.0 cm³, range 8.4 cm³-1357.9 cm³).

  At the end of the study, the average surface area of wounds in the test dressing group was 131 cm² (range 7.9 cm²-708.8 cm²), representing an average reduction of 42%. The end result for the test dressing with regard to volume reduction on average was 52%, with an actual average wound volume of 254.5 cm³ (range 8.7 cm³-1394 cm³).

  In the NPWT group, average surface area was reduced by 33% by the end of the study (average surface area 65.1 cm², range 0.7 cm²-278.4 cm²) and these wounds achieved a 50% average volume reduction (average wound volume 140 cm³, range 1.0 cm³-602 cm³). Figures 1 and 2 show surface and volume changes for the full data sets, as well as for the subsets (ie, all wounds without NLFU in both groups; all wounds with NLFU in both groups) while Figure 3 shows the average reduction per treatment group per day, expressed as percentages and as absolute quantities (cm² and cm³).

  Major cost differences were observed in the all-subjects-combined data sets as well as in the 2 subsets with regard to the total average cost of materials per lesion, the cost per percentage of surface and volume reduction, as well as the cost per day. For example, when comparing these outcomes for the 2 datasets containing all wounds, the total cost of materials per wound was $661.46 for the test dressing and $2,301. For NPWT, a cost difference of $1,640 (348%) was noted. Details for the entire data set as well as for the subsets can be found in Table 6.

  Exudate management is a crucial part of overall wound management since it assists in minimizing the detrimental aspects of exudate. This is particularly important when dealing with lesions that heal by secondary intention.^23,24 Negative pressure wound therapy has been used quite successfully for this purpose,^9,10 but the therapy also has a number of side effects and risks.²⁵ The test dressing was shown to provide a proper alternative to NPWT, with no specific risks, in an expert panel and Delphi panel review.¹⁷

  In this retrospective observational evaluation, a number of subjects were treated with either NPWT or a hydrokinetic fiber dressing (the test dressing) for the primary purpose of evaluating cost and assessing whether the test dressing could serve as an alternative to NPWT with regard to healing outcomes. One of the reasons for doing this evaluation was that, in the experience of the authors, NPWT may have been prescribed for wounds that, in fact, have contraindications for the use of NPWT, according to the manufacturer (eg, the risk of major bleeding and the presence of large amounts of necrotic tissue). Negative pressure wound therapy does not seem to facilitate debridement very well.^12,26

  The type of lesions in this evaluation differ extensively, although postsurgical wounds and pressure ulcers make up the majority of wounds in both arms of the study. Since wounds were left to heal by secondary intention the size of the wound primarily determines the speed of healing. The 2 groups were quite similar in size: pressure ulcers averaged 96.4 cm² in surface area and 339.6 cm³ in volume while the postsurgical lesions measured 121.7 cm² on average with regard to surface and 441.4 cm3 on average in volume.

  All subjects were living with comorbidities, with an average of 3 in the test dressing group and an average of 2 in the NPWT group (Table 2).

  All subjects were residents of an LTAC facility where the length of stay is limited; thus, the duration of participation in this evaluation for most subjects was limited as well. Given the seriousness and size of the lesions it was not expected that any of the subjects would reach complete reepithelialization. Still, within the study period, 17 (54%) lesions in the test dressing group and 8 (50%) in the NPWT group showed a level of reepithelialization between 25% and 75% of the original wound surface.

  In this LTAC facility, NLFU is part of standard of care when indicated to facilitate and assist in debridement.^18-20 The number of wounds treated with NLFU was substantially larger in the test dressing group than in the NPWT group. This is to be expected since the presence of necrosis is a contraindication for the use of NPWT. Indeed, it was for that reason that a number of subjects for whom NPWT was prescribed were actually treated with the test dressing.

  In addition to analyzing the entire study population, because of the imbalance in NLFU usage, healing and cost-related data were calculated for 2 subgroups: all wounds for which NLFU was combined with the test dressing (n = 21) or NPWT (n = 2); and all wounds for which NLFU was not used (test dressing, n = 5; NPWT, n = 14).

  Statistical analysis was not performed on the data sets. Because of the variety of lesions and the differences in size and treatment (ie, with and without NLFU), stratification would have led to a series of subsets of cohorts and, in each of these, the number of patients and/or lesions would have been too small to validate statistical conclusions.

  Virtually all lesions showed progress over the treatment period with regard to healing (ie, the change of necrosis to granulation and to reepithelialization) and secondary aspects related to healing (ie, improvements of the conditions of the periwound skin), whether they were treated with NPWT or with the test dressing. Depending on the actual healing parameter, results of treatment with NPWT were equivalent to, or substantially superior, for the wounds treated with the test dressing (Figures 1, 2, and 3).

  The cost of materials showed consistent trends, with absolute cost, cost per day, and cost per percentage of surface and volume healing being substantially lower for the test dressing (Table 6). This was the case when the 2 complete groups of subjects were analyzed but also for the analysis of the 2 data subsets (all with and all without NLFU). Seemingly peculiar differences with regard to cost (ie, the average cost of materials for NPWT without NLFU being higher than the cost of NPWT and NLFU combined) can be explained by the differences in length of stay and the number of dressing changes, which were 12 and 6 respectively (Table 6).

  The cost of materials does not reflect the cost of total care; but calculating cost of care was not the purpose of this evaluation and, for example, nursing time during dressing changes was not measured. At the same time, given the complexity of NPWT removal and application, the authors’ opinion is that for the same number of dressing changes, the cost of nursing would have been much higher for NPWT than for the test dressing.

  This type of retrospective observational study has the following inherent limitations: no randomization was used, the types of lesions were different among the different test groups, and there were differences with regard to surface and volume in the 2 groups. Given the size of the lesions, the number of comorbidities and the short treatment period dictated by allowed length of stay in an LTAC facility, it could not be expected that any wound would reepithelialize completely. Indeed, this did not happen. Still, while no statistical analysis was performed since stratification would have led to a series of subsets of cohorts that would have been too small to validate statistical conclusions, the trends with regard to healing were consistent, positive, and in line with other publications.^27-29

  Optimally preparing a patient for discharge is among the most important goals of treatment in an LTAC facility. Given the documented time limitations and the general shortage of financial and personnel resources³⁰ that exist in such a facility, different treatment protocols need to be available to attain this goal. These include NPWT, as well as treatment with a hydrokinetic fiber dressing, with or without NLFU.

  Two observational groups of patients with lesions in subjects with serious comorbidities were treated with 1 of these 2 treatment protocols. When evaluating all subjects in the 2 groups, healing trends were more positive for the test dressing while the cost of materials was substantially lower for this modality. Similar results were observed in 2 subsets of data (all subjects treated with the primary test dressing or NPWT device and NLFU, and all subjects treated with the test dressing or NPWT device without NLFU).

  No statistical analysis was performed because of the low number of patients in each subcohort; however, clinical trends with regard to healing showed similar results with reduced costs for the protocol using the hydrokinetic fiber dressing protocol. Within the proper indications for and limitations of each technique, both NPWT and the hydrokinetic fiber dressing offer a strong modality for the treatment of complex lesions in patients with serious morbidity.

Michel H.E. Hermans, MD is from Hermans Consulting Inc, Newtown, PA. S. Kwon Lee, MD, FACS, FAPWH; Mitzie R. Ragan, RN, WCC; and Pam Laudi, RN, CWS are from Vibra Hospital of Sacramento, Folsom, CA.

Address correspondence to:
Michel H.E. Hermans, MD
mhermans@hermans-hci.com

Disclosure: This study was supported by sorbion Gmbh & Co, a BSN medical company (Selden, Germany), for which Michel H.E. Hermans, MD, and Kwon Lee, MD, FACS, FAPWH, are consultants.