1. Woo, Kevin Y. PhD, RN, ACNP, GNC(C), FAPWCA
  2. Huang, Lei MD, ET
  3. Liu, Li-Bao MD
  4. Wen, Rui-Juan BSN
  5. Hu, Ai-Ling MD, ET
  6. Shi, Cheng-Gang MD

Article Content

In response:


We thank Dr Kottner and Ms Haesler for their interest in our study that examined dressings for preventing pressure injuries (PIs) and their thoughtful comments. Their comments are thought provoking, and we are grateful to have the opportunity to respond.


* Meta-analysis is a rigorous, quantitative study design that is increasingly valuable to assess a more precise estimate of the treatment effect of a particular wound care intervention in keeping with an explosive growth rate of scientific publication in recent years. The benefits of meta-analysis include pooled analysis of previous studies to reduce bias, and failure to identify relevant studies can lead to erroneous conclusions. A recent assessment had highlighted publication, availability, and selection biases as potential concerns for published meta-analyses.1 Dr Kottner emphasized the fact that a large body of literature is not indexed in the major databases, and non-English publications are often excluded from meta-analyses, leading to potential bias toward one aspect of the subject.


* A 24-hour follow-up period was considered insufficient in some reviewed studies to determine whether dressings were effective in preventing PIs. Although a 24-hour period is relatively short, Gefen2 has demonstrated that sustained pressure to vulnerable tissue may lead to PIs in high-risk individuals. In a recent study, Yap et al3 identified observable erythema, warmth, altered sensation, and/or change in tissue consistency over bony prominences after lying in bed for 2.35 +/- 0.57 hours. It is essential to be reminded that PIs can develop quickly, taking into accounts of intrinsic and extrinsic factors that determine tissue tolerance for pressure and oxygen.


* All stages of PIs were included in the outcomes measures of the studies. Dr Kottner had drawn our attention to the need to differentiate Stage 1 from the rest of PIs in light of a different pathophysiological mechanism for Stage 1 PI development. Pressure Ulcer Staging Revisited: Superficial Skin Changes & Deep Pressure Ulcer Framework4 was one of the first efforts to promote the idea that deep ulcers evolve from inside out, starting at the deep tissue layer that is most vulnerable to PI. Readers are encouraged to review this article, which was published in this journal in 2011. The fact that the National Pressure Ulcer Advisory Panel5 had recently announced a change in terminology from pressure ulcer to PI, including both intact and ulcerated skin, makes Stage 1 PIs a relevant endpoint for prevention studies. The worsening of PIs continues to be considered one of the quality indicators by regulatory bodies in North America.


* We would like to clarify that the Cochrane appraisal tool was used to evaluate RCTs only.


* Dr Kottner proposed using a random-effects model instead of a fixed model to conduct the analyses. We had chosen a fixed-effects model purposely, so that we could assign heftier weights to large studies. In contrast, the weights assigned under random effects are more balanced. We appreciate his recommendation to use a random model for the assessment of effect size across diverse populations.





Kevin Y. Woo, PhD, RN, ACNP, GNC(C), FAPWCA


School of Nursing, Faculty of Health Sciences, Queen's University, Kingston, Ontario, Canada; Western University, London, Ontario; West Park Healthcare Centre, Toronto, Ontario


-Lei Huang, MD, ET; Li-Bao Liu, MD; Rui-Juan Wen, BSN Ai-Ling Hu, MD, ET; and Cheng-Gang Shi, MD


The Third Affiliated Hospital of Sun Yat-Sen University, Guangzhou, Guangdong, People's Republic of China




1. Ahmed I, Sutton AJ, Riley RD. Assessment of publication bias, selection bias, and unavailable data in meta-analyses using individual participant data: a database survey. BMJ 2012;344:d7762. [Context Link]


2. Gefen A. How much time does it take to get a pressure ulcer? Integrated evidence from human, animal, and in vitro studies. Ostomy Wound Manage 2008;54:26-8, 30-5. [Context Link]


3. Yap TL, Rapp MP, Kennerly S, Cron SG, Bergstrom N. Comparison study of Braden Scale and time-to-erythema measures in long-term care. J Wound Ostomy Continence Nurs 2015;42:461-7. [Context Link]


4. Sibbald RG, Krasner DL, Woo KY. Pressure ulcer staging revisited: superficial skin changes & Deep Pressure Ulcer Framework. Adv Skin Wound Care 2011;24:571-80. [Context Link]


5. National Pressure Ulcer Advisory Panel. National Pressure Ulcer Advisory Panel announces a change in terminology from pressure ulcer to pressure injury and updates the stages of pressure injury. Last accessed July 26, 2016. [Context Link]