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Nigel Robinson
5 years ago
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1 Evaluating How Laundering Effects the Coefficient of Friction Values of Reusable Friction Reducing Devices Made From Woven Nylon Fabric with a Silicone Coating MEDICAL DEVICE ANALYSIS WHITE PAPER

2 Background In hospitals and other care facilities it is often difficult to move or reposition a patient in a bed. The reason for this is the fact that there can be a significant amount of resistance due to friction when attempting to move or reposition a patient. The greater the friction, or resistance, the more force it takes to move the patient. To lower the friction, it is common practice to use a friction reducing device (FRD), placed under the patient during the maneuver. FRDs as the name implies, provide a low coefficient of friction (COF) and minimize the resistance typically experienced when transferring or repositioning patients. COF is a calculated constant defined as the force required to move two sliding surfaces over each other, divided by the force holding them together. Friction reducing devices are available in sheet or tube form and are either classified as reusable or disposable. Reusable FRDs are commonly made from woven nylon fabric that is coated with silicone to lower COF. Disposable FRDs are made from slick, flexible plastic film. Reusable FRDs are laundered between patients and disposable FRDs are used on a single patient multiple times and then discarded or recycled. When reusable FRDs are new and unwashed, their COF is very low which is favorable. However, after laundering, the COF increases and the force required to move the patient increases as a result of the silicone being depleted progressively with each washing and drying cycle. Information about the amount of increase in COF with each washing cycle is not known. This common characteristic of reusable FRD s is typically not disclosed or considered a concern by most manufacturers or users! Lloyd and Baptiste, (2003) evaluated the efficacy of multiple FRDs from different manufacturers. The test data and conclusions are misleading in this evaluation for the reusable FRDs because the test data was taken from new, unwashed samples only. Single patient use FRDs do not have this increase of COF issue because they are not washed between patients; they are used multiple times on a single patient and then discarded. Purpose / Objective The purpose of this study was to investigate how the washing of a reusable FRD affects its COF or slickness. To measure how much the COF increases in a reusable FRD between and after multiple laundry cycles. To determine how many, if any, laundry cycles a reusable FRD can withstand before becoming unsafe to use per safe patient handling lifting limits established by the National Institute for Occupational Safety and Health (NIOSH). To show the increase in forces that a caregiver must exert as COF rises. Apparatus Friction Testing Machine based on American Society for Testing and Materials (ASTM) standard test method D Digital Dynamometer (Chatillon DFE-200 Series) Washing machine and Dryer Laundry Detergent 2

Proposed Methods COF Test The reusable FRD will be tested in four different conditions using five different sled weights. Condition 1 is new, unwashed.

3 Proposed Methods COF Test The reusable FRD will be tested in four different conditions using five different sled weights. Condition 1 is new, unwashed. Condition 2 is used, washed one time per manufacturer s instructions Condition 3 is used, washed a total of two times per manufacturer s instructions. Condition 4 is used, washed a total of three times per manufacturer s instructions. Laundering processes per manufacturer s instructions: Warm wash with mild detergent at maximum temperature of 175 F (80 C). Dry using low temperature tumble dryer. COF Test Procedure 1. Load sled appropriate weight (see step 4) and place reusable FRD specimen under sled. (See Fig.1) 2. Attach sled to dynamometer and move plane away from dynamometer by activating linear actuator. This creates a pulling force between the sled and the dynamometer as shown. 3. Record dynamic forces in pounds with dynamometer. 4. Repeat this test for each test condition with the following weights applied to sled: 111.4, 211.4, 311.4, and pounds. Weight Sled Reusable FRD Plane movement direction Dynamometer Fig. 1 (Friction Testing Machine) Plane Note: There are two main types of COF, dynamic and static. Dynamic COF is applies to objects that are in motion. Static COF applies to objects that are motionless. For this report, only dynamic COF was measured. 3

4 Data collection-cof Test Test ID# Condition of Reusable FRD Sled Weight, Lbs FORCE, Lbs (measured dynamic force from Dynamometer) 1 New, unwashed New, unwashed New, unwashed New, unwashed New, unwashed Washed one time per instructions Washed one time per instructions Washed one time per instructions Washed one time per instructions Washed one time per instructions Washed two times per instructions Washed two times per instructions Washed two times per instructions Washed two times per instructions Washed two times per instructions Washed three times per instructions Washed three times per instructions Washed three times per instructions Washed three times per instructions Washed three times per instructions Table 1 COF, Calculated (FORCE/Sled WEIGHT) 4

5 Results-COF Test Data was collected (table 1) with the Friction Testing Machine (fig. 1) using a reusable FRD that was subjected to four different conditions. The first condition (test ID numbers 1 thru 5) was NEW, unwashed. The second condition (test ID numbers 6-10) was washed one time per instructions. The third condition (test ID numbers 11-15) was washed two times per instructions. Finally, the fourth condition (test ID numbers 16-20) was washed three times per instructions. The COF values were favorable in the new, unwashed condition and progressively less favorable after successive washings (table1). Favorable COF was determined to be any value that allows a 500 pound patient to be moved with a force that does not exceed the NIOSH 35 pound limit for safe patient handling tasks (Waters, 2007). The COF significantly increased, unfavorably by 98% after the first washing, 135% after the second washing and 138% after the third washing compared to the new, unwashed condition. Further conclusions from Table 2 show that the new, unwashed reusable FRD did not exceed the NIOSH recommended 35 pound lifting limit even with the largest weight applied, but when the reusable FRD was washed once, the maximum weight that would not exceed the NIOSH 35 pound limit was just 300 pounds and after two washings it was 250 pounds. It is important to clarify that when the term sled weight is used, it can also be understood to be the weight of a patient. Furthermore, it is important to clarify that the measured dynamic force can be understood as the force that a caregiver exerts when moving a patient. The difference between a new, unwashed reusable FRD and a reusable FRD that has been washed just once is significant. This means that a caregiver would have to exert almost double the effort required to move a patient in bed. For example, a caregiver moving a 200 lbs patient with a new, unwashed reusable FRD will exert 11.8 lbs of force. For the same patient, the exerted force increases to 22.6 lbs using a reusable FRD that was washed once Sled Weight (Lbs) NIOSH Safe Zone NIOSH Un Safe Zone Force (dynamic) to move sled weight (Lbs) New, unwashed reusable FRD Reusable FRD washed once Reusable FRD washed twice Reusable FRD washed three times NIOSH 35# lifting limit Table 2 5

6 Discussion Several important observations were discovered about the reusable FRDs that were not investigated, but should be in the future. The following is a list of these observations: It was noted that there is no effective way to keep track of the number of washings a reusable FRD is subjected to. This would be an issue for caregivers because they cannot gage when the reusable FRD becomes ineffective. It was also noted that there isn t a method to verify whether the reusable FRD is clean or not. The only time a caregiver knows that the reusable FRD is clean is when it is new, in a sealed, clear poly bag. This is an issue that the infection control department will be concerned about. The cost of a reusable FRD can be up to twenty times the cost of a disposable, single patient use FRD. The manufacturers of the reusable FRDs recommend that they be used multiple times and washed between patients. The initial cost of the reusable FRDs can then be amortized over the number of patients they are used on for costing justification. The test results in this report indicate that this would present an inequitable value proposition based on the fact that the COF increases over 138% after just three washings. Another consideration is the fact that reusable FRDs can be lost or damaged in the laundering process. This creates inventory control issues that can potentially lead to FRD shortages in departments where they are needed most. There should never be a FRD shortage; they should have the same stocking priority as sterile, surgical gloves in an operating room. Conclusion The research findings in this test report clearly identify that washing a reusable FRD made from woven nylon fabric with a silicone coating significantly increased the COF unfavorably by 98% after the first washing, 135% after the second washing and 138% after the third washing compared to the reusable FRD in the new, unwashed condition. Poor COF performance creates more work and stress for a caregiver which in turn increases the risk of developing workrelated musculoskeletal disorders. The sole purpose of the FRD is to minimize the friction between the patient and the bed. Using a reusable FRD that has been washed is not the most effective solution for this particular patient handling task. Disposable, single patient use FRDs do not require laundering and therefore do not exhibit loss of COF issues. For this reason, serious consideration should be given to the use of disposable FRDs over reusable FRDs. If you are responsible for selecting equipment for your facility s safe patient handling program and want to know how Wy East Medical can help provide innovative solutions, please contact us at our website. 6

7 ACKNOWLEDGEMENTS John Judge, ME Chuck Lewis, Design Engineer References Lloyd, J., Baptiste, A Biomechanical evaluation of friction-reducing devices for lateral patient transfers. Walters, T. R. (2007). When is it safe to manually lift a patient? American Journal of Nursing, 107(8), doi: /01. NAJ b Wy East Medical Corporation, all rights reserved. This document contains information that is proprietary to Wy East Medical Corporation and may be duplicated in whole or in part by the original recipient for internal business purposes only, provided that this entire notice appears in all copies. In accepting this document, the recipient agrees to make every reasonable effort to prevent unauthorized use of this information. Corporate Headquarters Wy East Medical Corporation SE 120 th Avenue Clackamas, OR Phone: Fax: Sales and Product Information Phone: contact@wyeastmed.com AN R01 7

Cleaning & Sterilization

Handpieces & Attachments Instruments Cleaning & Sterilization System 7 System 6 System 5 CD4 CD3 SABO 2 SABO RemB CORE TPS Processing Instructions User/Patient Safety all contribute to the efficacy of