Wound Healing
Quantitative Research Critique
Vogt, Uhiyarik, & Schroeder (2007) conducted a study that compared Aquacel dressing vs. standard wound care for primary closed vascular surgical wounds. The results of the study found that there was no difference in length of stay in the hospital, complications, patient comfort, or healing time between the two wound care methods. The only difference was that the Aquacel dressing required fewer changes than conventional dressings, but that it increased the cost of care significantly. The following will analyze the methodology of the study and its conclusions in terms of clinical validity.
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 frame with work, previous literature, and the proposed hypothesis. All patients that participated in the study underwent elective vascular surgery.
Patients were randomized to either of the study groups. They would either be placed in the Aquacel group for wound care after surgery, or they would be placed in the standard wound care group after surgery. Randomization was allocated by a nurse by drawing a number corresponding to the group the patient would be assigned. Neither the researcher, the patient, nor the nurse knew to which group the patients would be assigned. The study involved 160 patients, with 80 in each of the control groups. The 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. This eliminated the potential for researcher bias.
The randomization procedure used in this study was appropriate for the study, which compared to different groups of patients. Groups were of equal size which allowed direct comparison of the two methods being studied. The randomization procedure used for group assignment eliminated a potential source of researcher bias and the potential for sample bias within the groups. There were no predetermined differences between the two groups of patients.
” Further design measures included exclusion of patients who were known to be sensitive to either of the wound dressing conditions that would be used. Patients that had dementia, who could not speak the native language of the area in which the surgery would be conducted, or who were pregnant were also excluded. Only patients were included that had an expected post operative hospital stay of at least four days. These measures helped to control for conditions that would serve as sources of bias in the sample population. The requirement for at least a four day hospital stay helped to ensure that the severity of the vascular surgery would be similar.
For patients that would receive multiple surgery sites, the same dressing was used on all of the surgery sites. This eliminated the possibility that difficulty healing wounds with one type of dressing would not interfere with wounds dressed with the other wound dressing method. It eliminated the potential that one wound dressing type would cause an immune system reaction that would affect would healing at all sites under different dressing conditions.
Although the preliminary design of the study appeared to be feasible and the randomization methods was not expected to interfere significantly with the surgical procedure, some conditions still existed that affected the equality of the two groups. Of the original 160 patients, 24 were excluded from the study at a later time. The three of the patients received the wrong type dressing according to their assigned number. Twelve patients were lost in the follow-up portion of the study. Three died, one underwent amputation, and one was transferred to intensive care. One was transferred to another hospital, and the observation reports of seven patients were not filled out properly. Nine patients had to receive a second surgery before follow-up. This left a total sample size of 136 patients. Although the final study group was smaller than that which was intended, the group was still sufficient to draw conclusions about the two types of wound dressings.
Several threats to internal validity of the study and sources of bias are inherent in most clinical trial studies. Although the author took considerable measures to eliminate sources of bias and threats to internal validity, some sources of bias exist which may affect the ability of patients to heal under either study condition, but which cannot be eliminated by the researcher. These include the severity of diabetes in the patients and how it affects their ability to heal, patient factors such as diet, exercise, and general immune system condition. In addition, patient assessment of comfort differs among individuals. Some may be more tolerant of a higher level of pain than others. Factors such as wound healing, length of hospital stay, and other medical factors are easily documented for comparison. The author took sufficient care to eliminate as many potential confounding variables as possible, but did not address or discuss those that were potential confounding variables, but which could not be controlled as they are inherent in the individual nature of the patients.
External threats to the validity of the study include the geographic location of the study and cultural affects in terms of pain tolerance and comfort interpretation. A study conducted in another country may experience different results on this element of the study. However, length of stay, and other elements that are medically measurable would not be expected to change, as the researcher took sufficient steps to control these elements.
Although a considerable number of study participants dropped out before they could complete the study, the two groups remained relatively equal in numbers. The elimination of these participants did not harm the ability to draw conclusions based on direct comparison of the two groups. The study did find differences in infection rates among patients with different primary surgical wound areas. The study noted that patients groin incisions had higher rates of infection than those with abdominal incisions. It was not anticipated that this would be a factor in the design of this study, but in subsequent studies patients may need to be selected for the area of intended incision as well as the other criteria noted earlier.
The design of the study is similar to a comparison of types of dressings performed on patients suffering from infected skin ulcers on their back. The results of the previous study coincide with the results of the study end of your consideration. There is sufficient previous evidence to support the findings of the study, even though the type of wound in previous studies was different from that in the study under consideration.
The research design of the study provides conclusive evidence that little difference exists between healing times, infection rates, and overall healing time with either type dressing under study. The researcher took careful consideration of the potential sources of bias and threats to internal and external validity. It is recognized that not all variables can be controlled, as some of them are inherent in the patients themselves. However, the researchers of this study took sufficient measures to control all of the variables that could be eliminated in the study.
The ability to straw conclusions could be enhanced in future studies by conducting a similar study on a larger patient population. Internal validity could also be improved by dividing patients according to the incision site, weight, General Health, sufficient control of diabetes, and factors that could affect the immune system and their ability to heal. From this study one could conclude that the choice of dressing is a matter of cost rather than one of effectiveness and quality of care for patients.
References
Vogt, K., Uhlyarik, M, & Scroeder, T. (2007). Moist wound healing compared with standard care treatment of primary closed vascular surgical wounds: A prospective randomized controlled study. Wound Rep Reg 15: 624 — 627
