Use of Polarized Light as a Method of Pressure Ulcer Prevention - Essay Example

Critique: Use of polarised light as a method of pressure ulcer prevention in an adult intensive care unit (Verbelen, 2007) A degenerative change of skin and underlying tissues leading to lesions of varying degrees caused by pressure and shear force is known as pressure ulcer. Patients in ICU are at high risk of such ulcers due to limitations in their body repositioning. Treatment of pressure ulcers, therefore, is of primary concern in ICU. In addition to the existing treatment of pressure ulcers, the study aims to do a pilot study of applicability of polarised light in treating pressure ulcers. Polarised light has been found to be successful in plastic surgery and treating burns and venous leg ulcers (Colic et al, 2004). It has also been found to heal wounds (Monstrey et al, 2001). Hence, polarised light may logically be expected to prevent damage to skin. The study aims to look at a possibly important applicability of polarised light. The study investigates applicability of polarised light to prevent pressure ulcers in adult ICU patients. Between March and May 2006 ICU patients in the university teaching hospital Academisch Ziekenhuis Vrije Universiteit Brussel, Brussels, were randomly allocated to either treatment or control group after judging by inclusion-exclusion criteria. The control group received standard prevention measures while treatment group received exposure to polarised light in their sacral and heel areas for 10 minutes duration once a day. Population for this study is all adult ICU patients who are expected to be in ICU for more than 7 days. Chance of developing pressure ulcers in ICU patients increases with longer duration of stay in ICU. Sample for this study is all eligible patients admitted to the university teaching hospital between March and May 2006 who completed the treatment regime. Sample size in the treatment group is 13 and sample size in control group is 10. In both groups sample size is too small. Informed consents from the patients or their representatives were taken before they were randomized in the treatment and control groups. However, within the duration of ICU stay the patients were not given a chance of switching over to the treatment regime. The end result of the study shows treatment with polarised light is significantly better in preventing pressure ulcers of grades II and beyond. While there may be arguments as to how believable this result is (we have discussed this issue later), ethical considerations may have directed the investigators to apply polarised light treatment to those patients who have shown significant deterioration in ulcerous conditioning in their sacral or heel areas. Preventive measures for pressure ulcers started from the day the patient was admitted in the ICU if he/she is eligible for the study. Treatment with polarised light started the next day. If a patient from either treatment or control group developed an ulcer, this was recorded using digital photography using Sony DCS-717. The surface area of the ulcer was also measured, if possible, using the Visitrak system. The study does not elaborate why in some cases the surface area measurement was not possible. All the confounding variables like gender, age, body length, weight, ulcer development status, reason for ICU admission and degree of complicacy etc were collected daily wherever needed. Pressure ulcer status was recorded as either complete absence of any damage or its presence, nature and description. Gradation of pressure ulcers was done using a system similar to EPUAP gradation. Since the result of the study depends on the gradation of pressure ulcers, a discussion on gradation here has some merits. There are numerous gradation systems with varying degree of user-friendliness and reliability (Dealey and Lindholm, 2006). However, inter-rater agreement in grading for any of the systems is quite low, especially for severe ulcerations. For this study it is not clear whether the gradation is done by specialized nurses or if more than one person was involved in grading ulcerations. It has also been empirically seen that EPUAP, though simple to use, has a better reliability than more complicated classifications (Dealey and Lindholm, 2006). One patient already had pressure ulcer before being admitted to the ICU. Other than that all patients in the study were treated for ulcer prevention at sacral as well as heel areas. The maximum duration of ICU stay for a test case was 24 days and maximum duration for a control case was 25 days. Day 1 pressure ulcer risk and preventive measures used for test case were compared to the corresponding measures for day 1 in the control group. Similar comparison was done for all days till day 24. Difficulty with such comparison is that, for the first 7 days observations for all 23 ICU patients were available (10 for test and 13 for control group). Note that minimum stay in ICU over 7 days was an inclusion criterion. However, duration of stay in ICU increased, number of cases available for comparison reduced. For day 24, or indeed for the last few days on the study, the comparison may have been done on one patient only in each of test and control group. Such a comparison is not at all valid in statistical sense. In fact, the discharge time distribution for the patients from ICU for both the test and control groups should have been provided. That would have given an idea about the tail of the distribution and the power of the statistical procedure. Mann-Whitney U test compares ranks in two groups. It is not clear how the ranking was done. To construct the U statistic, the number of times each observation from group 1 (say, test group) has higher rank than observations from group 2 (control group) is counted. Then this is totalled for all observations in group 1. However, there is no provision for including gradation in ordinary Mann-Whitney test. To construct Mann-Whitney statistic, when all grades of ulcers were considered, after how many days the first ulceration appeared in any of the locations in test sample and how many ulcerations appeared in the control group before that could have been counted. Similarly, when only grades 2 – 4 of ulcerations were compared, grade 1 ulcerations may have been ignored and comparison made as above. But it is not clear whether that procedure has been followed. Another drawback in applying Mann-Whitney procedure in this case is lack of independence of the observations. Recall that areas for development of ulcers were compared, not patients. Each patient was observed for 3 areas, which were not independent observations, though patients were. If each area has been considered to be contributing independently, then this analysis is wrong! A third objection is that of construction of confidence interval. Mann-Whitney test can be applied for small sample. In that case small sample approximations are required. Normal approximations are valid only if sample size is larger than 20 (Corder & Foreman, 2009). The 95% confidence interval is also suspect. Since the statistical procedure is not quite appropriate in this situation the result may not be valid at all. This implies that the statistical significance claimed may not be true, even after ignoring the grade 1 classification of pressure ulcerations. In fact Figure 5 shows that in the test group incidence of grade 1 ulceration is more than the control group. This observation questions the advantage of using polarised light in prevention. Further, this figure is not comparable to the rest of the study. In the main part of the study the locations are compared, whereas the figure shows only the number of patients. A more comparable figure would have been one showing in how many locations in the test and control groups ulcerations developed. The limitations of this study fail to establish beyond doubt the applicability of using polarised light. That does not indicate that treatment of polarised light will not help in prevention of pressure ulcers. However, a better planned study is necessary. Also, this study was done in only one location. Multi-centre study is necessary for establishing the applicability of polarised light. That will increase the sample size and will eliminate any bias that may have been present in this study. References Dealey, C & Lindholm, C. (2006) ‘Pressure ulcer classification’, Science and Practice of Pressure Ulcer Management, vol. 3, pp 37-41. Corder, G.W. and Foreman, D.I. (2009) Nonparametric Statistics for Non-Statisticians: A Step-by-Step Approach, New York: Wiley. Monstrey, S., Hoeksema, H., Depuydt2002), K., Van Maele, G., Van Landuyt, K. And Blondeel, P. (2002) ‘The effect of polarized light on wound healing’, European Journal of Plastic Surgery, vol. 24, pp 377-382. Colic, M. M., Vidojkovic, N., Jovanovic, M. And Lazovic, G. (2004) ‘The use of polarized light in aesthetic surgery’, Aesthetic Plastic Surgery, vol. 28, pp 324-327. Verbelen, J. (2007) ‘Use of polarised light as a method of pressure ulcer prevention in an adult intensive care unit’, Journal of Wound Care, vol. 16, pp 145-150. Read More