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Samson DJ, Lefevre F, Aronson N. Wound-Healing Technologies: Low-Level Laser and Vacuum-Assisted Closure. Rockville (MD): Agency for Healthcare Research and Quality (US); 2004 Dec. (Evidence Reports/Technology Assessments, No. 111.)

  • This publication is provided for historical reference only and the information may be out of date.

This publication is provided for historical reference only and the information may be out of date.

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Wound-Healing Technologies: Low-Level Laser and Vacuum-Assisted Closure.

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2Methods

This report is the product of a systematic review of the evidence on the outcomes of two technologies for wound healing: low-level laser therapy and vacuum-assisted closure. The protocol for this review was designed prospectively as much as possible to define: study objectives; search strategy; patient populations of interest; study selection criteria; outcomes of interest; data elements to be abstracted and methods for abstraction; and methods for study quality assessment.

This chapter of the report describes the objectives, key questions, and search strategies used to find articles; the criteria and methods for selecting eligible articles; the methods for data abstraction; the methods for quality assessment; and finally, the peer review and technical assistance received during the project.

Objective and Key Questions

The objective of this evidence report is to systematically review and synthesize the available evidence on the effectiveness of low-level laser treatment and vacuum-assisted closure for wound healing. To achieve this objective, the following key questions will be addressed:

Low-Level Laser Treatment

In the treatment of chronic, nonhealing wounds, what are the outcomes of low-level laser therapy for specific indications and patient types:

  1. as a substitute for standard therapy; or
  2. as an adjunct to standard therapy, compared with standard therapy alone?

Vacuum-Assisted Closure

In the treatment of various wounds, what are the outcomes of vacuum-assisted closure for specific indications and patient types:

  1. as a substitute for standard dressings; and
  2. as an adjunct to standard therapy, compared with standard therapy alone?

Search Strategy

Electronic database searches were completed of MEDLINE® (via PubMed), EMBASE, and the Cochrane Controlled Trials Register. The MEDLINE® search covered references entered onto the database from January 1, 1966 through June 8, 2004. The Cochrane Controlled Trials Register search was completed in 2003, through issue number 4. The EMBASE search covered references entered through June 14, 2004. For detailed search terms, please refer to Appendix A.1

The search was limited to studies on human subjects with English-language abstracts. Papers published in foreign languages were reviewed if the English-language abstract appeared to meet inclusion criteria. Results of the search and study selection were reviewed by the Technical Expert Panel for this project, in order to identify additional studies.

In addition, two companies that produce lasers used in wound healing (Microlight Corporation of America and Photothera), as well as the major producer of vacuum-assisted closure devices (V.A.C.®, Kinetic Concepts Inc. [KCI]), were contacted and were invited to submit evidence-based information for the review. The specific request was for “lists of published, randomized, controlled trials (RCTs), published abstracts of RCTs within the past 2 years, and published articles on study design, or protocols of any RCTs (published or in progress).”

In some cases, device approval applications to the U.S. Food and Drug Administration (FDA) contain data from randomized, controlled efficacy trials. If available, such trials should be sought by the literature search. However, lasers used in wound healing and vacuum-assisted closure devices have been cleared for marketing by the FDA's 510(k) process, a regulatory mechanism that does not require submission of data from controlled efficacy trials.

Patients, Settings, Interventions, and Outcomes

Patient Populations

Low-level laser treatment. With respect to low-level laser treatment, chronic wounds may be classified in a variety of ways. The simplest way is to distinguish between cutaneous ulcers and burns. However, a more comprehensive classification system places chronic wounds into these categories:

  • pressure ulcers
  • metabolic disorders (e.g., diabetes mellitus)
  • vascular insufficiency
  • inflammatory disorders
  • malignancies
  • infections
  • miscellaneous (e.g., burns)

Vacuum-assisted closure. The review for vacuum-assisted closure addressed:

  • chronic wounds (as above)
  • acute wounds
  • traumatic wounds
  • subacute wounds
  • dehisced wounds
  • partial thickness burns
  • diabetic ulcers
  • pressure ulcers
  • flaps
  • grafts

Study populations with both acute and chronic wounds will be examined carefully with respect to the duration of the wound and the types of interventions that have been performed prior to treatment with low-level laser therapy or vacuum-assisted closure. Some wounds may be described as refractory; that term should be defined as specifically as possible in terms of the types and duration of previous treatments. Similarly, the term “chronic” should be defined in as much detail as possible.

Practice Settings

Low-level laser treatment and vacuum-assisted closure may be used in the following settings:

  • Surgical centers
  • Hospitals
  • Specialized wound care centers
  • Nursing or rehabilitation facilities
  • Physicians' offices
  • Physical therapy offices
  • Homes

Interventions/Technologies of Interest

Standard care. Standard wound care is multifactorial. Among its components are:

  • Debridement
  • Dressings
  • Topical or systemic medications
  • Compression
  • Skin grafting
  • Skin equivalents
  • Improved nutrition
  • Convalescence
  • Physical therapy
  • Treatment of underlying disorder

Low-level laser treatment. This review will focus on lasers that have been described as low-energy, low-power, low-level or “cold” lasers. The power of these lasers ranges from 0.001 watts (1 mW) to 0.05 watts (50 mW), producing minimal heating of tissue. Lasers used in wound healing applications include the gallium-aluminum (GaAl), gallium-arsenide (GaAs) and helium-neon (He-Ne) laser. Characteristics of laser treatment that would be of interest include laser type, intensity (measured in Joules per square centimeter of wound surface [Joules/cm2]), duration of each session, frequency of sessions, and overall duration of treatment. Other prior and concurrent treatments will be examined in detail.

Vacuum-assisted closure. The vacuum-assisted closure technique involves application of a sterile, open-pore foam dressing directly on the wound, which is then sealed with an adhesive drape, thus converting an open wound to a closed, controlled wound. An evacuation tube, embedded in the dressing, feeds into a collection canister. When subatmospheric pressure is applied, effluent from the wound is drawn out. Attention will be paid to the degree of negative pressure applied, frequency of dressing changes, and duration of use of the vacuum device. Other prior and concurrent treatments will be examined in detail.

Outcomes of Interest

In general, outcomes should be standard, valid, reliable and clinically meaningful. A 2000 draft guidance document produced by the FDA (U.S. Food and Drug Administration, 2000) stated that wound healing outcomes should focus on the probability or speed of achieving complete wound closure. Intermediate outcomes such as wound size are problematic because of uncertainty about the validity of measurement techniques and clinical meaningfulness.

  • Primary outcomes:
    • incidence of complete wound closure
    • time to complete closure
    • adverse events
  • Secondary outcomes
    • facilitating surgical closure
    • need for debridement
    • infections
    • pain
    • activities of daily living
    • quality of life
    • improved cosmesis

Other secondary outcomes abstracted were change in wound size and transcutaneous oxygen tension (tcpO2); however, these were considered to be of less clinical importance.

Study Selection Criteria

As noted in the Introduction chapter of this Report, randomized, controlled trials are necessary to adequately assess the effectiveness of wound-healing interventions. Wound care entails multiple treatment factors, and it can be very difficult to attribute an effect to a specific factor. In addition, confounding could occur due to differences in patient characteristics and the quality and type of treatment factors. Randomization is the best method to assemble treatment groups that are comparable on known and unknown patient confounders.

This systematic review will select only randomized, controlled trials meeting the following criteria:

  1. The trial must involve one of the following comparisons of interventions
    1. Either low-level laser treatment or vacuum-assisted closure, compared with other wound healing interventions (alternative intervention trials).
    2. Either low-level laser treatment or vacuum-assisted closure in addition to standard wound care, compared with standard wound care alone (incremental benefit trials).
    3. Either low-level laser treatment or vacuum-assisted closure, compared with a sham intervention (placebo trials).
  2. For low-level laser treatment, patient selection criteria must target those with chronic wounds. For vacuum-assisted closure, patient selection may address those with chronic wounds or other types of wounds (see “Patient Populations,” above).
  3. The trial must report on at least one of the outcomes listed above under “Outcomes of Interest.”
  4. The trial must be published as a full journal article and not merely as a conference abstract.

Any citation lacking an abstract was excluded if the article was published in a non-English-language journal. Otherwise, when abstracts were missing, the full-text article was retrieved for review if the title suggested it might possibly meet the study selection criteria.

For low-level laser, the searches found 482 references: 435 were excluded on the first screen, 47 were retrieved, 11 met selection criteria and were abstracted, and 36 were excluded on the second screen. For vacuum-assisted closure, the searches found 467 references: 416 were excluded on the first screen, 51 were retrieved, six met selection criteria and were abstracted, and 45 were excluded on the second screen.

Methods of the Review

Search results were stored in ProCite® databases. Titles and abstracts were screened by a single reviewer who marked each citation as either eligible for review as full-text articles or ineligible for full-text review. A second reviewer reviewed all citations marked as ineligible by the first reviewer. Agreement between raters was necessary to exclude a citation from full-text review. An “eligible” rating was necessary from only one reviewer to place a citation in the pool of those to be retrieved for full text review.

In reviewing full-text articles to determine eligibility for data abstraction, a single reviewer determined whether each paper should be either: (1) included in systematic review; (2) excluded from systematic review; or (3) discussed with additional reviewer.

Evidence tables were developed in Microsoft Excel® and Microsoft Word®. One reviewer performed primary data abstraction of all data elements into the evidence tables, and a second reviewer checked the evidence tables for accuracy.

A procedure was established in case of disagreements that could not be resolved between the two reviewers. In such cases, the EPC Program Director was consulted and then, if necessary, the relevant members of the Technical Expert Panel.

Assessment of Study Quality

This systematic review applies the general approach to grading evidence developed by the U.S. Preventive Services Task Force (Harris, Helfand, Woolf, et al., 2001). Two independent reviewers rated study quality and disagreements in ratings were resolved by consensus. Following are the study design criteria and rating definitions developed by Harris and colleagues.

Study Design Criteria

  • Initial assembly of comparable groups: adequate randomization, including concealment and whether potential confounders (e.g., other concomitant care, patient characteristics) were distributed equally among groups
  • Maintenance of comparable groups (includes attrition, crossovers, adherence, contamination)
  • Important differential loss to followup or overall high loss to followup
  • Measurements: equal, reliable, and valid (includes masking of outcome assessment)
  • Clear definition of interventions
  • All important outcomes considered
  • Analysis: adjustment for potential confounders, intention-to-treat analysis

Definition of Quality Ratings

In applying the Harris rating system to the studies selected for this systematic review, several rules were followed. To conclude that a study achieved initial assembly of comparable groups, it had to use an adequate randomization method and had to have equal distribution of confounders. Adequate randomization was defined as either central randomization or use of opaque envelopes (concealment). For the purposes of this review, equal distribution of confounders was defined as a minimal difference (less than 20%) in mean values between groups on age, wound duration and wound size. Low loss to followup and maintenance of comparable groups was defined as loss less than 20% of the initial sample and no differential loss to followup between groups.

To consider measurements reliable, valid and equal, the article had to provide a clear description of wound measurement methods that appeared reproducible. Examples include use of photographic or digital transfer of wound tracings and/or use of computer software to calculate wound size. Liquid or plaster used to measure wound volume was also acceptable. Use of a blinded outcome assessor was also necessary to fully satisfy this quality dimension. Clear, detailed descriptions of both control and treatment interventions were sought. Analysis of results was considered appropriate if the investigators adjusted for confounders and analyzed by intention-to-treat, which was defined as analyzing all randomized patients or no more than 5% loss of the initial sample. See Table 3 for the quality criteria and ratings system applied to the evidence tables in Chapter 3.

Table 3. Quality Rating Criteria and Ratings.

Table

Table 3. Quality Rating Criteria and Ratings.

Good. Meets all criteria: Comparable groups are assembled initially and maintained throughout the study (followup at least 80 percent); reliable and valid measurement instruments are used and applied equally to the groups; interventions are spelled out clearly; all important outcomes are considered; and appropriate attention to confounders in analysis. In addition, for RCTs, intention-to-treat analysis is used.

Fair. Studies will be graded “fair” if any or all of the following problems occur, without the fatal flaws noted in the “poor” category below: Generally comparable groups are assembled initially but some question remains whether some (although not major) differences occurred with followup; measurement instruments are acceptable (although not the best) and generally applied equally; some but not all important outcomes are considered; and some but not all potential confounders are accounted for. Intention-to-treat analysis is done for RCTs.

Poor. Studies will be graded “poor” if any of the following fatal flaws exists: Groups assembled initially are not close to being comparable or maintained throughout the study; unreliable or invalid measurement instruments are used or not applied at all equally among groups (including not masking outcome assessment); and key confounders are given little or no attention. For RCTs, intention-to-treat analysis is lacking.

Technical Expert Panel and Peer Review

The development of this evidence report was subject to extensive expert review, including ongoing guidance from a Technical Expert Panel (TEP) and document review by the TEP.

The draft report was also reviewed by a panel of external peer reviewers that included experts in anesthesiology, dermatology, nursing, otolaryngology and orthopedic surgery, physical therapy, plastic and reconstructive surgery, podiatry, therapeutic laser technology, and undersea and hyperbaric medicine. Reviews were also solicited from the American Academy of Wound Management, the Association for the Advancement of Wound Care, and Wound, Ostomy and Continence Nurses Society. Comments were elicited from external peer reviewers using a structured comment form, compiled, and submitted with a description of comment disposition to the Agency for Healthcare Research and Quality (AHRQ). Appendix B lists the members of the Technical Expert Panel and external peer reviewers.2

Footnotes

1

Appendixes will be provided electronically at http://www​.ahrq.gov/clinic/tp/woundtp​.htm

2

Appendixes will be provided electronically at http://www​.ahrq.gov/clinic/tp/woundtp​.htm

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