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Designation F3276 − 19Standard Guide forUsing a Force Tester to Evaluate the Performance of aBrush Part Designed to Clean the External Surface of aMedical Device1This standard is issued under the fixed designation F3276; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon ´ indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide describes methods for characterizing theefficacy, under prescribed laboratory conditions, of a brush partdesigned to clean the external surface of a medical device. Themethod utilizes force testers to mechanically actuate a brushpart across a surface at a constant rate and constant pressure. Inthe first method, the force required to actuate across the surfaceis measured. In the next method, which utilizes the same forcetesters and protocol actuation motion, the brush part isactuated on a soiled surface and the amount of soil removed ismeasured, as another indicator of performance.1.2 Brushes designed to clean medical devices after clinicaluse play an important role in the effective reprocessing of thosemedical devices.1.3 Inclusions1.3.1 This guide describes objective, quantifiable, and re-producible methods for evaluating the cleaning characteristicsof a brush part, under prescribed laboratory conditions, with atest method that simulates the cleaning challenge of a definedtarget areas of a medical device. This also makes it possibleto compare one brush part design to another.1.3.2 By use of this guide, manufacturers of cleaningbrushes will be able to evaluate and characterize the cleaningperformance of their brushes for the target areas of medicaldevices and evaluate modifications to design and constructionthat might improve performance.1.3.3 By use of this guide, this information can also beshared with the users of the brushes medical device reproces-sors to help them evaluate the performance of commerciallyavailable brushes.1.4 Exclusions1.4.1 This guide does not assess potential damage that maybe inflicted by the brush, or degradation of the brush that mayoccur during repeated use. Brushes with rigid bristles e.g.,stainless steel or other metals are predicted to be more likelyto damage medical devices than brushes with flexible bristlese.g., nylon; damage from rigid-bristled brushes should beassessed. Assessing repeated use would require a greatlyincreased number of test repetitions than what is described inthis guide.1.4.2 This guide does not specify acceptance criteria, andthe results will be dependent on the specific parameters that aretested e.g., test soil, drying time, surface area, and materials,etc. that are tested.1.4.3 This guide is not intended to constitute all stepsrequired to conduct validation of cleaning instructions for amedical device, including use of brushes for this purpose, butprovides methods that may be part of a broader protocol toconduct a complete cleaning instructions validation. Separatemedical device cleaning instruction validation studies must beconducted.1.5 UnitsThe values stated in SI units are to be regardedas standard. No other units of measurement are included in thisstandard.1.6 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.7 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade TBT Committee.2. Referenced Documents2.1 ASTM Standards2F3208 Guide for Selecting Test Soils for Validation ofCleaning Methods for Reusable Medical Devices1This test method is under the jurisdiction of ASTM Committee F04 on Medicaland Surgical Materials and Devices and is the direct responsibility of SubcommitteeF04.15 on Material Test Methods.Current edition approved Feb. 15, 2019. Published March 2019. DOI 10.1520/F3276-19.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standard’s Document Summary page onthe ASTM website.Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade TBT Committee.12.2 ISO Standards3ISO/TS 15883-5 Washer-disinfectorsPart 5 Test soils andmethods for demonstrating cleaning efficacyISO 222542005 DentistryManual toothbrushesResistance of tufted portion to deflection2.3 AAMI Documents4AAMITIR12 Designing, testing and labeling reusablemedical devices for reprocessing in health care facilitiesA guide for medical device manufacturersAAMITIR30 A compendium of processes, materials, testmethods, and acceptance criteria for cleaning reusablemedical devices2.4 FDA Document5FDA Guidance for Industry and FDA Staff, Processing/Reprocessing Medical Devices in Health Care SettingsValidation Methods and Labeling, 20173. Terminology3.1 Definitions3.1.1 cleaningremoval of contamination from a medicaldevice to the extent necessary for further processing or for itsintended use.3.2 Definitions of Terms Specific to This Standard3.2.1 brush partworking end of the brush that comes incontact with the targeted surface of the substrate.3.2.2 surface roughnessthe shorter frequency of real sur-faces relative to the troughs.4. Summary of Practice4.1 This guide provides details for testing the resistance ofa brush part moved across a surface to simulate the resistanceof a brush used to clean the external surface of a medicaldevice.4.2 This guide also provides details for soiling a surface,actuating a brush part across that surface, and measuring thesoil removed from that surface to simulate the cleaning of theexternal surface of a medical device.4.3 Surface substrate selection is based upon the physicalcharacteristics i.e., smoothness, material, etc. of the medicaldevice being simulated.4.4 Composition and application of the test soil should bebased upon an evaluation of the clinical-use of the deviceGuide F3208, FDA 2017, AAMI TIR12, ISO/TS 15883-5.5. Significance and Use5.1 This guide provides two test methods for evaluating theperformance characteristics of a brush part designed to cleanexternal surfaces of a medical device by utilizing forcetesters.5.1.1 The first test method utilizes a force tester to measurethe force required to actuate a brush part across a surface. Thisis an indicator of the friction a brush exerts on a surface, aparameter of cleaning effectiveness.5.1.2 The second test method measures the removal of soilfrom a surface by a brush part actuated across the surface. Thisis a further indicator of the effectiveness of a brush part toloosen and remove soil from a surface.5.2 By providing objective, repeatable methods for evaluat-ing performance, under test conditions, this guide can improvethe ability to assess the effectiveness of various brush partdesigns6. Description of Test Apparatus6.1 A force testing machine with moving crosshead, forcegauge, and a suitable clamp for substrates see Fig. 2.6.1.1 The crosshead shall be programmable for the speedand the distance it travels.6.1.2 The force required to move the brush up and downshall be measured.6.1.3 The clamp attaches to the crosshead and holds the testsubstrates in place.6.2 Brush Fixture6.2.1 The brush fixture is secured underneath the crossheadof the force tester.6.2.2 The clamp to hold brushes shall be adjustable toaccommodate different size brushes.6.2.3 The brush clamp shall be on a sliding track that isadjustable horizontally so the brush can be moved closer to andfurther from the substrate.6.2.4 A force gauge is attached to the fixture to measure theforce of the brush pushing against the substrate. This forcegauge should be able to measurea5Nforce.6.2.5 The brush fixture also includes a support to prevent thesubstrate holder from being deflected. This support also doesnot cause resistance against the substrate holder from beingactuated up and down.6.3 Sensitive Analytical Scale6.3.1 To determine the weight differences in the soiledsubstrates, the scale shall be sensitive to at least 0.1 mg.6.3.2 The scale shall have a large enough stage to weigh theselected substrate size.7. Selection Criteria for Testing Parameters7.1 Selection of Surface Substrate for Testing7.1.1 The physical characteristics of the surface should besimilar to the physical characteristics of the surface of themedical devices the brush is intended to clean. This includesthe surface roughness and any geometric features like crevices,ridges, etc. AAMI TIR30. At a minimum, the followingshould be considered in selecting the surface substrate fortesting 1 material the substrate is made of e.g., stainlesssteel, polytetrafluoroethylene, silicone, etc.; 2 surface finishe.g. machined, ground, polished; and 3 device geometryi.e., crevices, ridges.7.1.2 Since the same brush design may be used on morethan one type of device, testing of multiple substrates with3Available from International Organization for Standardization ISO, ISOCentral Secretariat, BIBC II, Chemin de Blandonnet 8, CP 401, 1214 Vernier,Geneva, Switzerland, http//www.iso.org.4Available from Association for the Advancement of Medical InstrumentationAAMI, 4301 N. Fairfax Dr., Suite 301, Arlington, VA 22203-1633, http//www.aami.org.5https//www.fda.gov/downloads/medicaldevices/deviceregulationandguidance/guidancedocuments/ucm253010.pdfF3276 − 192different material composition may be necessary to fullycharacterize performance.7.1.3 The length of the surface substrate should be at leastlong enough to allow the complete travel of the brush partacross the surface. Complete travel may be defined as adisplacement equal to the length of the brush part, with contactmaintained between the full length of the brush part and thesubstrate during the entirety of travel.7.2 Selection of Test Soil and Application Method7.2.1 The test soil should be similar in composition andphysical qualities to the clinical soil the medical device comesin contact with during patient use Guide F3208, FDA 2017.7.2.2 The volume of test soil applied to a device shouldreflect worst-case clinical conditions.7.2.3 The application of the soil should simulate the worst-case soiling that a medical device is likely to experience duringclinical use see Guide F3208, FDA 2017.7.2.4 The time the soil is allowed to dry on the surface of thesubstrate should simulate worst-case drying during clinical use.7.2.5 A cleaning solution that is similar to the cleaningsolution likely to be used to clean the device after clinical useshould be selected.7.3 Selection of Force7.3.1 Selection of Force Applied to Brush Part duringResistance Testing7.3.1.1 Often, a brush intended to clean the surface of amedical device is similar in design and function to a brushintended to clean teeth, so the guidance in ISO 22254 is areasonable starting point to determine the force to use. Accord-ing to ISO 22254, the force applied to determine the resistanceof bristles to deflection is set to 5 N.7.3.2 Selection of Force Applied to Brush Part during SoilRemoval7.3.2.1 Applying a specific force to the brush against thesubstrate is suitable for testing the resistance of the bristles todeflection, but not for testing cleaning ability.7.3.2.2 A stiffer bristle brush deflects less at a given forcethan a softer bristle brush. Therefore, when comparing brusheswith different bristle firmness at a given force, a brush withsofter bristles will have greater contact with the surface than abrush with stiffer bristles.7.3.2.3 For purposes of this test method, the degree ofbristle deflection should be kept constant. This approach allowsa comparison at equivalent bristle deflection, since softerbristles will apply less force against a substrate than will stifferbristles.7.3.2.4 To begin testing, the brush head is brought intocontact with the substrate, such that there is minimum contactbetween the bristles and the substrate. The substrate holdershould be deflected by less than 1 mm by the brush pushingagainst it, so as not to affect the force measured duringresistance testing. This is achieved by a support behind thesubstrate holder that is part of the brush fixture see Fig. 2.8. Procedure for Testing Resistance on a Surface8.1 Mount the brush part in the grip of the brush fixture seeFig. 1.8.2 Select a substrate for testing see 6.1 and clamp thesubstrate into the substrate holder. Mount the substrate holderto the crosshead see Fig. 2. The substrate holder mounted tothe crosshead should have a deflection of ≤1 mm when a 5 Nforce is applied.8.3 Program the force tester for the following8.3.1 The distance the substrate will travel along the brushpart see 6.1.8.3.2 The speed at which the substrate will be moved downagainst the brush part.8.3.3 The speed at which the brush substrate will be movedup against the brush part.8.3.4 The number of times the substrate will be actuatedagainst the brush part.8.4 Align the brush part at the top of the substrate see Fig.3.8.4.1 Using the brush fixture, position the brush to exert 5 Nof force against the substrate measured by the secondary forcegauge see Fig. 4.8.4.2 Run the test program.8.4.3 Record the results. The peak and average force mea-surement for both the upward and downward movement of thesubstrate should be measured and recorded.FIG. 1 Brush Part Mounted in Brush FixtureF3276 − 1939. Procedure for Evaluating the Cleaning of a Surface9.1 Select the test soil 6.2 and prepare as needed.9.2 Select the substrate for testing 6.1. If this testingfollows the force testing described in Section 7, the samesubstrate should be used.9.3 Weigh the substrate see Fig. 5.9.4 The volume of soil used to soil the substrate should bedetermined 7.2.9.5 The length of time to allow soil to dry should bedetermined 7.2.4.9.6 Soil the substrate see Fig. 6 and allow to dry. In orderto compare one brush part to another, the soil coverage shouldbe uniform.9.7 Weigh the soiled substrate see Fig. 7.9.8 Prepare a cleaning solution see 7.2.5.9.9 Dip the brush part in the cleaning solution see Fig. 8for a specified period of time.9.10 Mount the brush i
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