Background: Worldwide, wounds continue to pose immense challenges for patients, carers, researchers, practitioners and health services. A cutaneous wound is a disruption in the integrity of the skin caused by pathologic processes. Wound healing aims to restore the anatomic continuity and function of the skin (See Figure 1) and requires synchronised efforts from numerous different cell types. The ability to indicate wound healing potential is of great interest as it offers the possibility to detect healing complications earlier and, hence, facilitates the application of more efficient and appropriate interventions. As traditional methods of wound measurement are prone to subjective interpretation, this systematic review explored the potential of measures of pH, exudate composition and temperature in wounds to act as objective and valid indicators of wound healing outcomes.
Method: A systematic review was conducted to answer: 1. What is the potential of measures of pH, temperature and exudate composition to predict wound healing? 2. What are the methods used to measure pH, exudate composition and temperature in wounds that offer the most benefit in clinical practice?
Search Strategy: In December and January 2016, a pre-determined search strategy was conducted (See Figure 2). As part of this search, the reference lists of all the included studies and of other relevant publications, such as systematic reviews and guidelines, were examined to ensure completeness of the search outcome.
Studies Included: All quantitative primary research papers, published in the English language, involving all types of participants, of any age or in any setting, with an existing or an intentionally provoked wound were eligible for inclusion.
Quality Appraisal: Once the data were extracted, quality appraisal of the included studies was conducted by one reviewer and checked by a second, using the Evidence Based Literature (EBL) Critical Appraisal Checklist devised by Glynn (2006).
Results: A total of twenty-four studies, three for pH (mean quality score 54.48%), twelve for exudate composition (mean quality score 46.54%) and eight for temperature (mean quality score 36.66%), met the inclusion criteria (See Figure 2).
pH: The research findings suggest that reducing levels of pH in wounds from alkaline towards acidic are associated with improvements in wound condition (See Figure 3).
Temperature: Results suggest that temperature measurements are highest in non-healing, worsening or acute wounds and decrease as wounds progress into phases of healing (See Figure 3).
Exudate Composition: Matrix metalloproteinase-9 (MMP-9), matrix metalloproteinase-2 (MMP-2), tissue inhibitor of metalloproteinase (TIMP), neutrophil elastase (NE) and albumin, in descending order, were the most frequently measured analytes in wounds (See Figure 4). MMP-9 emerged as the analyte which offers the most potential as a biomarker of wound healing, with elevated levels observed in acute or non-healing wounds and decreasing levels in wounds progressing in healing. Combined measures of exudate composites, such as MMP/TIMP ratios, also appeared to offer substantial potential to indicate of wound healing.
Discussion: Methods used to measure pH, exudate composition and temperature varied greatly within each subject and, despite noting some similarities, the studies often yielded significantly contrasting results. A further limitation to the generalisability of the findings was the overall quality scores of the research studies which appeared suboptimal (See Figure 5). pH measurement emerged as the most promising method for use in clinical practice to indicate wound healing outcomes. Nonetheless, further research is required to determine the strength of evidence for these concepts as measures of wound healing and to develop a greater understanding of the dynamics of wound healing. With this advanced knowledge, the value of measuring pH, exudate composition and temperature in wounds should become more apparent and a valid indicator for wound healing outcomes may be revealed. In turn, these greater understandings should foster increased accuracy and efficiency in wound care practices, support developments in wound management devices and, ultimately, promote patient outcomes.
Clinical Relevance: Despite the emergence of promising findings for all three characteristics of measurement, most particularly pH, as potential predictors of wound healing outcomes, significant deficits and weaknesses in current research impede the possibility to confidently recommend the use of any of these measures for use in clinical practice. On the other hand, this systematic review has highlighted areas that would be of value for further research.
References: Power, G., Moore, Z. & O'Connor, T. (2016) pH, exudate composition and temperature measurement: A systematic review. MSc Research, Royal College of Surgeons in Ireland.
Acknowledgements: The School of Nursing and Midwifery, Royal College of Surgeons of Ireland, are graciously acknowledged for providing the research bursary for conducting the systematic review on which this poster is based.