Quantitative Research Critique: Wound Healing Dressing Study

Introduction and Study Overview

Vogt, Uhlyarik, and Schroeder (2007) conducted a study that compared Aquacel dressing with standard wound care for primary closed vascular surgical wounds. The results found no difference in length of hospital stay, complications, patient comfort, or healing time between the two wound care methods. The only notable difference was that the Aquacel dressing required fewer changes than conventional dressings; however, it increased the cost of care significantly. The following analysis examines the methodology of the study and its conclusions in terms of clinical validity.

Research Design and Randomization

The design of the study was a randomized controlled trial comparing standard dressing to Aquacel dressing for vascular surgical wounds. The study design directly reflected the intended purpose of the research, the research questions, the theoretical framework, previous literature, and the proposed hypothesis. All patients who participated in the study underwent elective vascular surgery.

Patients were randomized to one of two study groups: either the Aquacel group for wound care after surgery, or the standard wound care group after surgery. Randomization was allocated by a nurse drawing a number corresponding to the group to which the patient would be assigned. Neither the researcher, the patient, nor the nurse knew in advance to which group the patients would be assigned. The study involved 160 patients, with 80 in each of the two groups. The sealed envelopes were not opened until the patients were in the surgical theater at the time of dressing application. This research design was appropriate, as it represented a double-blind assignment into groups, which eliminated the potential for researcher bias.

The randomization procedure used in this study was appropriate for a study comparing two distinct groups of patients. The groups were of equal size, which allowed for direct comparison of the two methods being studied. The randomization procedure for group assignment also eliminated a potential source of researcher bias and reduced the potential for sample bias within the groups. There were no predetermined differences between the two groups of patients.

Further design measures included the exclusion of patients known to be sensitive to either of the wound dressing conditions. Patients with dementia, those who could not speak the native language of the area in which surgery would be conducted, and pregnant patients were also excluded. Only patients with an expected postoperative hospital stay of at least four days were included. These measures helped control for conditions that could serve as sources of bias in the sample population. The requirement for at least a four-day hospital stay also helped ensure that the severity of vascular surgery would be comparable across participants.

For patients who required multiple surgery sites, the same dressing was used on all sites. This eliminated the possibility that difficulty healing one wound with a particular dressing type could interfere with the healing of wounds dressed with the other method. It also eliminated the potential that one type of wound dressing could trigger an immune reaction affecting healing at all sites simultaneously.

Sample Characteristics and Attrition

Although the preliminary design of the study appeared feasible and the randomization method was not expected to interfere significantly with the surgical procedure, some conditions arose that affected the equality of the two groups. Of the original 160 patients, 24 were excluded from the study at a later stage. Three patients received the wrong type of dressing according to their assigned number. Twelve patients were lost during the follow-up portion of the study. Three died, one underwent amputation, and one was transferred to intensive care. One patient was transferred to another hospital, and the observation reports of seven patients were not completed properly. Nine patients required a second surgery before follow-up. This left a total sample size of 136 patients. Although the final study group was smaller than originally intended, the group was still sufficient to draw conclusions about the two types of wound dressings.

Although a considerable number of participants dropped out before completing the study, the two groups remained relatively equal in numbers. The elimination of these participants did not substantially harm the ability to draw conclusions based on direct comparison of the two groups. The study did find differences in infection rates among patients according to primary surgical wound area. Patients with groin incisions had higher rates of infection than those with abdominal incisions. This factor was not anticipated in the original study design, but subsequent studies may need to stratify patients by incision site in addition to the other criteria noted above.

References

Vogt, K., Uhlyarik, M., & Schroeder, T. (2007). Moist wound healing compared with standard care treatment of primary closed vascular surgical wounds: A prospective randomized controlled study. Wound Repair and Regeneration, 15, 624–627.