Content Validation of Algorithms to Guide Negative Pressure Wound Therapy in Adults with Acute or Chronic Wounds: A Cross-sectional Study

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Ostomy Wound Manage. 2012;58(9):32–40.
Janice M. Beitz, PhD, RN, CS, CNOR, CWOCN, CRNP; and Lia van Rijswijk, MSN, RN, CWCN


  Despite extensive use of negative pressure wound therapy (NPWT) and reported patient safety concerns, evidence-based algorithms to guide its safe and appropriate use in various wounds have only recently been developed. Preliminary content validity was established using literature review and expert-based face validity with a small sample of experts (N = 12).

To examine the content validity of this set of three NPWT algorithms and to enhance understanding about previously identified wound terminology issues, a cross-sectional, mixed-methods, quantitative study was conducted among wound experts. The paper/pencil survey instrument consisted of the algorithms, a demographic questionnaire, and request to provide definitions of five commonly used terms: acute wound, chronic wound, and primary, secondary, and tertiary intention healing. A Likert scale (range 1 to 4) was included to rate the relevance of each of the 34 unique steps/statements/decision points contained in the algorithms, and space was provided to comment on each component. Convenience-sampling methods were used in three different settings: an international professional wound care meeting; a regional wound, ostomy, continence (WOC) nurses meeting; and an urban university with a suburban satellite campus. Of the 190 wound care experts invited to participate, 114 accepted. Participants’ average age was 48 (range 23 – 68) years, and most were registered nurses (72%) practicing in the United States (94%).

  The content validity of the NPWT components was strong, with an overall mean rating of 3.76 (SD = 0.56, range 3.49 to 3.92; very relevant/appropriate, relevant/appropriate). The overall content validity index for the 5,696 responses received was 0.96 (range 0.88 – 1.0). Qualitative themes included comments about wound terminology and definitions, the presentation of the central algorithm, reading level, helpfulness/ease of use, the use of color, and information placement in the algorithm document.

  Some consensus on wound definitions was observed, but results also confirmed that important disparities in mutual understanding of what constitutes acute versus chronic wounding remain. Commonly used surgical closure definitions of primary, secondary, tertiary intention also were not clearly or correctly understood by a substantial number of participants. These NPWT algorithms are the first evidence-based, content-validated algorithms developed for a variety of acute and chronic wounds in adult patients. Future research is needed to test whether they facilitate safe patient care in clinical practice. 

 Potential Conflicts of Interest: This study was supported by a research grant from ConvaTec (Skillman, NJ). The study was conducted, the data analyzed, and the manuscript written by the authors who are responsible for the content of this publication. The authors do not have a financial interest in any of the products discussed in this publication.


  Negative pressure wound therapy (NPWT) is widely used to manage acute and chronic wounds. According to some estimates, the global NPWT market is expected to exceed $3 billion by the year 2016.1 For many years, only one NPWT system utilizing one negative pressure setting (-125 mm Hg) was widely available. An expansion of NPWT device variety in the healthcare marketplace has facilitated development of devices that are less costly, use different dressing materials, or utilize lower negative pressure settings2,3; studies comparing the outcomes of using these various devices remain limited.4,5

  With expanded usage, safety concerns also have emerged.6,7 In Pennsylvania, the Patient Safety Authority received 419 reports during 2008 and 2009 related to the application or management of NPWT, including bleeding, bowel evisceration, retained sponges, infection, maceration, and compromise of tissue surrounding the wound.8 To help prevent patient harm associated with the use of NPWT, the authority recommends clinicians employ risk reduction strategies such as appropriate patient selection, ensure proper device application, and utilize frequent monitoring techniques.8

  NPWT guidelines of care (evidence-based suggestions for care) and algorithms (graphic representations of concepts and decision points) have been available for some time, but most are wound-type specific, consensus-based, and do not include specific criteria for when to stop using negative pressure.9 Recently, evidence-based NPWT algorithms were developed to guide the safe and appropriate use of NPWT in adults.10 Specifically, they guide clinicians in the process of appropriate patient/wound selection and wound assessment and provide concrete criteria for discontinuation of NPWT.9 Preliminary content validity was established using systematic literature review and expert-based face validity. The content validity was high (0.96, 0.95, and 0.94 on a scale of one for algorithm 1, 2, and 3, respectively), but results are limited to a sample of 12 multidisciplinary wound experts. Concerns about some commonly used wound definitions also arose.

  The purpose of this cross-sectional, mixed-methods quantitative survey study was to examine the content validity of this set of three NPWT algorithms using a sample of at least 100 wound experts and to gain understanding about terminology issues in wound care. Specifically, the research questions were:
    1. How do wound care experts rate the appropriateness/content validity of the components and processes inherent in the NPWT algorithms?
    2. What themes of positive responses or concerns about appropriateness do wound care experts describe when assessing content validity?
    3. What insights into the wound care decision-making processes can be obtained from user comments about NPWT algorithm usage?
    4. How do wound care experts define acute wounds, chronic wounds, and the terms primary, secondary, and tertiary intention?


  Algorithms and validity. Because they graphically represent concept interrelationships and critical decision points, algorithms help healthcare clinicians with decision-making. By showing the big picture, algorithms, like concept maps, help structure more efficient thinking.11-14 When algorithms are valid and reliable, they also help clinicians implement evidence-based care. Validity is a crucial factor in the development and utilization of any instrument but especially for algorithms or care maps affecting patient safety. Content validity evaluation is a rigorous process that involves development and judgment quantification. The development stage involves the identification of the domain area (eg, NPWT), component generation, and the instrument or algorithm construction. The judgment quantification phase involves having experts rate the degree of item or component relevance using an empirical method.15 Using a process developed by Waltz and Bausell16 and modified by Lynn,17 experts rate the content relevance of critical components by using a 4-point scale, similar to a Likert scale. For the current study, option ratings were 1— not relevant/appropriate, 2 — unable to assess relevance without revision, 3 — relevant but needs minor attention, and 4 — very relevant and appropriate. In addition, a content validity index (CVI) is derived based on the proportion of ratings of 3 and 4 on a component versus 1 and 2 ratings. The higher the CVI on a scale of one, the higher (and perceived stronger) the content validation rating.18

  NPWT algorithms. The NPWT algorithms were developed to 1) provide stepwise evaluation and assessment strategies for optimal use of NPWT in adults with acute and chronic wounds, 2) provide evaluative strategies for transitioning between moist wound healing and NPWT protocols of care in adults, and 3) reduce risk factors for delayed healing and chronic wound development.9 Development of the NPWT algorithms was guided by the literature, starting with previously developed algorithms for specific wound etiologies, systematic reviews, and a framework for transitioning between NPWT and moisture-retentive dressing treatment4,19,20-40 and has been described in detail elsewhere.9 Briefly, evidence from these and subsequently obtained publications was abstracted, and evidence for the 39 discreet decision points/steps in the algorithms was rated using the patient-centered Strength of Recommendation Taxonomy (SORT).41 Only one NPWT-related and two general patient assessment steps/decision points had consistent and good quality patient-oriented evidence (“A” strength of recommendation).9

  To validate the content of the algorithms, an instrument containing 51 discreet statements related to algorithm construct was developed, and 12 multidisciplinary wound care experts completed the subsequently conducted face- and content validation study. Wound expert response to the algorithms was positive, and the CVI of all algorithms was very high (>0.95 on a scale of one). Furthermore, the qualitative results suggested a lack of agreement on the definitions of acute wound and chronic wound, as well as primary, secondary, and tertiary intention healing.9 Suggestions were incorporated into the algorithms, and it was decided to include questions about wound terminology in the second content validation study in order to gain further insight.


  Design and sampling. A mixed-methods, quantitative survey study design and convenience sampling method was used to answer the research questions. Sample inclusion criteria were relatively broad in order to encourage participation by the wide variety of professionals involved in wound care and wound care research; these criteria included 1) licensed healthcare professional or clinical researcher with wound care background, 2) able to read, write, and speak English, and 3) willing to abide by a confidentiality statement. Wound care background meant extensive wound care experience and/or formal education in wound care, preferably with board certification. Institutional Review Board (IRB) approval was obtained, and all volunteers were asked to sign an informed consent form. No participant received financial compensation. All responses were anonymous, and completed consent forms were collected before the start of data collection. Data collection occurred over a period of 4 months. Healthcare clinicians attending a national wound conference and expert wound nurses associated with a university School of Nursing and Health Sciences, as well as with a regional wound, ostomy, continence (WOC) nurses group, were invited to participate, for a total of 190 invitees.

  Setting and procedures. Data collection occurred in a variety of settings, but the collection process was the same. Data were collected in a special session at a major international meeting focused on wound care, at a meeting for regional WOC nurses, and at both campuses of a university located in an urban area but with a suburban satellite campus. Survey and testing processes were preceded by a 5- to 10-minute explanation and brief developmental history of the algorithms, after which prospective participants were asked to sign the informed consent documents. Participants kept a copy of the form. After collecting the consent forms, the algorithms and questionnaire were distributed. Participants were not given a time limit for completion. Most participants completed the questionnaire in approximately 60 minutes, and all materials were returned at the end of the session.

  Instrumentation. A professionally produced color copy of the algorithms (Draft 6)10 was given to each participant along with a paper-pencil data collection instrument. The survey consisted of four parts: 1) demographic data form, 2) a definitions section asking volunteers to describe in their own words the terms acute wound, chronic wound, and primary, secondary, tertiary intention healing, 3) the content validation questionnaire, and 4) open-ended questions asking for overall comments about the NPWT algorithms and the research process.

  The demographic data section comprised 18 questions regarding attributes (age, gender), highest level of education, years of clinical experience, practice setting, types of wounds commonly cared for, and types of wounds cared for using NPWT. The content validation questionnaire was basically the same as that used for the pilot content validation study.9 The only difference was that several general patient assessment questions were not included, reducing the total number of steps/statements from 51 to 34. Participants’ opinion about the components contained in the three algorithms was assessed by having participants rate each statement on a 4-point Likert-type rating scale as follows: 1 = not relevant/appropriate; 2 = unable to assess relevance without revision; 3 = relevant but needs minor alteration; and 4 = very relevant and appropriate. Each of the 34 statements also provided an opportunity for comments regarding omissions, suggestions for improvement, presenting an alternative, and/or citing literature references to support their comments. The final page allowed for written comments about the overall content and process of the study and asked for suggestions for improvement (with references if possible) for the NPWT algorithms.

Data collection/analysis. All variables were entered into an Excel version 2003 spreadsheet (Microsoft Corporation, Seattle, WA) and uploaded into SPSS version 16.0 (SPSS Inc, Chicago, IL) for analysis. Summary statistics were calculated for demographics. Write-in demographics (eg, wound type) were tabulated. Mean scores, modal scores, and CVI were derived. The CVI was calculated by grouping items rated relevant/very relevant (ratings of 3 and 4) and not relevant/unable to assess relevance (ratings of 1 and 2).18 The proportion of items rated 3 or 4 was calculated for each statement and all components as per Polit and Beck’s18 recommendation.

A professional transcriptionist who signed a confidentiality agreement transcribed all participant written responses and written comments. Using qualitative data reduction techniques, researchers analyzed the typed transcripts for themes, subthemes, and indicator statements. A doctoral colleague with qualitative expertise reviewed the qualitative comments and derived themes.


  Sample. One hundred, ninety (190) persons were invited; 114 participated, a response rate of 60%. The majority of the participants were women (107, 94%) with a mean age of 48 years (SD 10.46, range 23 to 68); 92 (81%) indicated they had 10 years or more of clinical experience, and 76 were certified in some wound specialty. Most participants had a bachelor’s degree (82, 72%) and received their basic health professional education in the US (107, 94%). The most commonly encountered wounds in their practice were surgical, trauma, and pressure ulcers. The most commonly encountered wounds for use of NPWT included surgical, pressure ulcer, and dehiscence/evisceration wounds.

 All participants were licensed health professionals or clinical researchers with experience in wound care. The group practiced mostly in the US (109, 96%); other countries of practice included Australia, Brazil, and Norway. Most respondents’ practices were located in the Northeast US (71), mostly in Pennsylvania and New Jersey. Acute care (hospital) was the most common practice setting (63, 47%). “Other” settings most commonly included wound care centers, industry, and outpatient. Most participants spoke English only (98, 86%). Most participants reported they had formal classes on wound care (101, 89%) and that they were certified in wound care (76, 67%). Formal education was reported most frequently as classes in the Wound Care Certified (WCC) program (2, 1%) and Wound, Ostomy, Continence Nursing Education Program (WOCNEP) (87, 86%) (see Table 1).

 Quantitative analysis. To answer research question 1 (How do wound care experts rate the appropriateness/content validity of the components and processes inherent in the NPWT algorithms?) for the set of three algorithms, a total of 5,696 responses were received and analyzed. The mean score for all three algorithms was 3.76 (+ 0.56). The mode was 4 and the CVI 0.96. The mean scores for all 34 components of the three algorithms ranged from 3.92 to 3.49 and the mode was 4 for all components (see Table 2, available with this article online at Mean ratings that were lower (<3.6) but still rated appropriate included the items: Classify a nonsurgical wound as acute or chronic, Consider separate goals of wound care for primary intention (sutured) healing or palliative care, and Consider goals of care and appropriateness of moist wound healing for sutured wounds and palliative care. CVI results <0.90 included the items: Classify a nonsurgical wound as acute or chronic, Consider separate goals of wound care for primary intention (sutured) healing or palliative care, and Consider goals of wound care and appropriateness of moist wound healing for sutured wounds and palliative care. From these results, the algorithms can be interpreted as being very relevant or in need of only minor revisions.

  Qualitative analysis. Qualitative analysis was used to answer research question 2 (What themes of positive responses or concerns about appropriateness do wound care experts describe when assessing content validity?). Qualitative results confirmed the high average rating scores and CVI and suggest the algorithms are valid and will likely help healthcare clinicians, but some suggestions were offered. Major themes of positive responses or concerns were generated along with indicator statements from the narrative analysis of comments about major decision points in the algorithms. Participant comment thematic analysis targets specific areas of needed improvement, but most relate to general categories across algorithms — ie, need for clarification of terms used, need for reference support, some minor additions (eg, nutritional aspect more emphasized [was already present]), appearance and presentation of algorithms, better use of color and visual symbols (eg, stop signs at discontinuation points), suggested wording changes, and issues with role clarification (prescriber versus nonprescriber) (see Table 3, available online with this article at Some themes did not pervade all three algorithms. These included frequency of change issues, questions regarding moisture level, wound depth issues, and debridement issues. Some participants disagreed with listed inappropriate use of NPWT, noting “some superficial wounds benefit from NPWT.” Positive comments about the helpfulness of clear goals and a clear instrument pervaded all three algorithms.

  Research question 3 asked, “What insights into the wound-care decision-making processes can be obtained from user comments about the NPWT algorithms usage?” Participant comments about the overall research process and overall impression of the algorithms were analyzed using qualitative data reduction techniques and organized along with indicator statements. They generated both positive and negative themes (see Table 4, available online with this article at Many participants noted a need for embedded or accessory definitions for terms used in the algorithms. This need was especially strong for future nonexpert users. Participants also commented on the “busy” nature of Algorithm 1 and included suggestions for re-arrangement and condensing.

 Some participants were concerned about reading level. Other comments related to use of colors, symbols, information positioning, and rewording of selected areas. Several questions were raised regarding more emphasis on pain management and exudate levels; specifically, several noted that NPWT can be used when minimal exudate is present, although no references or evidence were offered. Many participants thought the NPWT algorithms were easy to use and helpful. 

  Research question 4 asked, “How do wound care experts define acute wounds, chronic wounds, and the terms primary, secondary, and tertiary intention?” Qualitative analysis of the proposed definitions provided by participants was very informative (see Table 5, available online with this article at Participant comments were analyzed for critical wording or phrases (underlined in Table 5). A subsequent frequency count of common descriptions revealed some common understandings. Conversely, experts provided an array of definitions. For acute wound, the four most common (frequent) definitions included open <30 days (4 weeks), heals quickly (days to 2 weeks), heals in 3 to 6 weeks, and healing within a normal timeframe. For chronic wound, the four most common (frequent) definitions were open >30 days, wounds that don’t follow normal sequence of wound healing, takes time to heal/greater than normal time to heal, and stopped in usual healing (can be from 1 month to 3 months).

  For primary, secondary, and tertiary intention, definitions were less dispersed for primary intention. By far, the most frequent definition was surgical wound closed after surgery with sutures, staples, derma bond (glue)/edges approximated. For secondary intention, two definitions were most frequent: wound left open to heal via granulation tissue and healing from inside out/granulation to epithelialization/to heal from “bottom up.” For tertiary intention, two definitions were most common: healing by secondary intention then surgically closed and delayed primary – wound closed surgically. Notably, some terms had an array of definitions with some erroneous or unusual understandings: acute wound (wound that heals in less than or close to 6 months); primary intention (heals on its own accord; healing with complication; to heal from the main insult); secondary intention (unsure; open to treat, then surgically closed; sutures…); a wound treated by NPWT because it’s not healing from primary intention; tertiary intention (unsure; heals on its own; use of skin graft to close wound; wound healing dependent on special machine or skill such as graft or other biologic material; large wound dermis/heals from inside until granulation 100%/ longer time to heal; when grafting involved; surgically open with intent for natural closure by granulation; similar to secondary intention but longer time and larger amount of scar tissue).


  The NPWT algorithms are the first evidence-based and content-validated algorithms developed for a variety of acute and chronic wounds. The overall mean rating and CVI of the NPWT algorithms as rated by 114 wound experts suggest the algorithms are relevant/appropriate and have strong content validity. Even components with a lower score (CVI <0.90) are still considered valid (CVI of >0.80).18 The high scores are relatively unsurprising, given that the new algorithms were developed based on current available research via systematic review, expert guidance, and consensus and that they incorporate aspects of previously content- and construct-validated wound care algorithms.42-44  Qualitative analysis supported fuller understanding of the areas of weaker ratings, especially such needs as definitions of terminology available or built into the algorithms. Related comments also elucidated some areas where guidance on NPWT usage is murky, such as levels of anticoagulation and amount of wound exudate.

  User comments also generated interesting issues involving comments about past clinical situations where NPWT may have been used inappropriately and confirmed authors’ observations that not all previously published NPWT guidelines contain the same information and that questions about optimal use remain.45,46 Qualitative comments also guided visual redesign and the use of color of some algorithm components. Stop points were redesigned into stop sign red-colored notations, and decision point lines were more clearly distinguished from “next step” lines. Wound definitions. User descriptions of commonly used wound terminology were surprisingly disparate, given the fact that participants self-identified as having formal education and/or certification in wound care. Users suggested that basic terminology have linked definitions attached to the algorithms. When asked to provide definitions, the reasons were obvious: great disparities in mutual understanding of what constitutes acute versus chronic wounding; and aspects of surgical closure definitions (primary, secondary, tertiary intention) not clearly or correctly understood by a substantial component of participants, even though these definitions are clearly and commonly presented in the surgical and wound care literature and in basic print and online medical dictionaries.47-49 Perhaps clinical practice has altered understanding or perhaps participants received less rigorous formal education than reported or presumed. Concerns about the general quality and quantity of wound education have been expressed in the literature, and problems with wound terminology, definitions, and the language of wound care have been previously identified.42-44,50-52

Implications for Clinical Practice, Education, and Research

  The NPWT algorithms provide a major addition to contemporary clinical practice. To the authors’ knowledge, they are the only guidelines that contain clear usage endpoints and are face- and content-validated for the overall safe use of NPWT. Another strength of visual pathway guidance is that the level of evidence is available for each decision point and that indications and contraindications are easily identified, thus promoting appropriate patient and wound selection.8 Users do not have to search through pages of a user manual to locate wound-specific usage criteria.

  A potential limitation is that the NPWT algorithms are designed for use in adults only. No comments can be made related to their safe use in children. In addition, the NPWT algorithms do not contain specific instructions for some wound locations (eg, open abdomen, mediastinitis, and the like) but rather focus on acute versus chronic wounds.

 The NPWT algorithms have implications for education. Users of the NPWT algorithms will have to be educated about their optimal use, and inconsistent understanding of basic wound care terminology should be addressed. Users will need to have a common, correct understanding of terminology such as acute versus chronic wound, primary, secondary, and tertiary intention, and full- versus partial-thickness wound congruent with the literature.

  Education related to the optimal use of the NPWT algorithms may benefit from digital technology. Just as the Solutions® Algorithms have been placed into an interactive, multimedia digital program with great success,44 a similar type of program for the NPWT algorithms would allow 24-7 educational access.

  Research implications. Although face and content validity have been established, these factors need to be tested for construct validity — ie, tested for use with real world patients. Are the algorithms easy to use? Do they promote safe and appropriate use? Aid appropriate transition to moist wound care? Improve patient outcomes? Given the limited evidence-base for some NPWT indications and usage criteria, especially compared to nongauze dressings, and the potential publication bias,31 the use of these algorithms ideally should be compared to evidence-based moisture-retentive dressing protocols of care. Although randomization may be difficult to achieve in clinical practice, a controlled prospective cohort study comparing algorithm use to standard practice may help answer these research questions.


  Although the sample was composed of wound experts, predominantly nurses, no medical or surgical physicians were included except for a podiatrist and physician assistant. Conversely, the sample did include the wound care discipline most involved with use of NPWT — ie, advanced practice and registered nurses. The former can order start or discontinuation of NPWT. The latter can recommend (and often do) the same processes.

  Another limitation is the fact that content validation does not assess use of the algorithms with real patient wounds (construct validity). Full testing in the future should include the use of the algorithms with real patients to assess their impact on outcomes.

  An additional limitation is the focus of the algorithms. They were designed specifically for use in adults. Therefore, their use in pediatric patients requiring NPWT cannot be addressed. Examination of the algorithms demonstrates that many critical decision points are based on lowest level of evidence (eg, expert opinion). However, this constitutes the best evidence available.


  The provision of safe and effective wound care is a major concern for all clinicians. Given the challenges and reported poor outcomes with regard to NPWT use,7,8 evidence-based, content-validated algorithms targeting NPWT in acute and chronic wounds for adults may help improve outcomes of care. The results of this study and the previous development study9 indicate the newly developed NPWT algorithms have strong face and content validity, although previously identified gaps in evidence to support NPWT usage remain. The results of this study also suggest multiple factors may affect optimal use of these algorithms in the future, including clinician understanding of wound terminology, wound definitions, and wound healing physiology. Studies to evaluate the effect of implementing these algorithms in clinical practice on patient outcomes and costs of care are warranted.


  The authors thank all study participants for volunteering their time and sharing their extensive expertise. In addition, Valerie Bradley’s assistance with the data collection process is gratefully acknowledged.

Dr. Beitz is a Professor of Nursing, School of Nursing-Camden, Rutgers University, Camden, NJ. Ms. van Rijswijk is a lecturer, Holy Family University School of Nursing and Allied Health Professions, Philadelphia, PA; and Clinical Editor, Ostomy Wound Management. Please address correspondence to: Dr. Janice Beitz, School of Nursing-Camden, Rutgers University, 407 Armitage Hall, 311 North 5th Street, Camden, NJ 08102; email:


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