To the Editor,
We read the article "An Ex Vivo Comparison of 2 Cyanoacrylate Skin Protectants" by Daniel J. Gibson in Journal on Wound, Ostomy and Continence Nurses Society (2018;45(1):31-36) that describes a comparison of 2 commercially available skin protectants: a cyanoacrylate-based and a mixed polymer/cyanoacrylate product with interest. There are several statements and conclusions of this work that are questionable and are respectfully challenged.
Although some description of the chemistries was provided, we assert that the author inaccurately characterized the polymer/cyanoacrylate product as a "nonreactive paint-like polymer." The author mentions that "(1) the cyanoacrylate formulation should take slightly longer to solidify, so that it could be more easily spread on the surface of the skin, and (2) the product should be more flexible preventing it from flaking off with normal movement." The author appears to be unaware of the relationship between flexural rigidity of a coating and its thickness. Without extensively diverging into the field of engineering mechanics, the flexural rigidity of a coating may be modeled as
, where D is flexural rigidity, E is Young's modulus, v is Poisson's ratio, and h is the thickness. The thicker a coating is applied (assuming substantially equivalent Young's moduli and Poisson's ratios), the less flexible and much more prone to fracture and flaking the coating would become. A simple doubling of the coating thickness would make the film 8 times less flexible.
The article does not provide additional detail as to how each of the products was applied to the porcine skin (eg, how much of the product was contained in the porous sponge, the angle of application, time to apply, and time to dry) or how their varied application substantiates and/or confirms comparative assessment for film thickness and uniformity.
It is evident and further confirmed by the author that "in both cases, histological processing and sectioning appeared to affect the amount of coverage, since many portions of the sections did not have a visible layer under DIC microscopy" and "the layers, which survived histological processing were sporadic." The author also stated that "overall, the SEM results are consistent with the hypothesis that the pure cyanoacrylate product cannot be washed away with organic solvents, while some portions of the mixed product can." The author infers that the polymer/cyanoacrylate product was impacted more by the histological process than the pure cyanoacrylate product and thus does not reflect the actual amount of product that was initially present on the section before processing. Hence, we assert that conclusions based on these data would/should be ill-advised.
The author claims that the "products differ so substantially in performance" yet provides insufficient evidence to support. The author goes on to state "while we have presented results indicating that one skin protectant remains in place and is thicker, the nature of the film [referring to the polymer/cyanoacrylate] has yet to be studied. Additional studies testing the efficacy of the barrier to irritants, detergents, and bodily fluids such as urine and feces remain to be performed, as do longevity studies, which test the duration of any protective effect seen." This is further confirmed by his last statement "additional research is needed to clarify implications of these differences and to probe the efficacy of these skin protectants." These are 2 of many instances where the author states that he is uncertain of the clinical performance or relevance, yet affirms a questionable position that the degree of thickness is an important indication as such. It should be noted that evidence supporting the polymer/cyanoacrylate's performance in clinical use was published in this journal in 2017.1
Respectfully,
Raymond Chiu
Technical Director-3M Company
Robert Asm
Division Scientist-3M Company
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