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Testing & Inspection
Patrick J. Nolan is Chief Operating Officer of DDL Inc., a full-service testing laboratory providing package, product, and material testing. Nolan has twenty years of experience in the package testing industry and is a frequent speaker at industry- related events.
MPMN: How does the accelerated aging process simulate real-life conditions? What is the margin of error?
Nolan: The accelerated aging theories are based on the "activation energy" of the materials, which are very difficult to determine without significant research and testing. The activation energy information is then used to determine the "aging factor" to eventually calculate the required time in a chamber at a certain test temperature. This activation energy varies from material to material. For research that has been done on homogeneous plastic materials, the activation energy has been found to produce a higher 'aging factor' (2.5-3.0) than what is typically used in the medical device package testing industry (1.8-2.0). However, since package systems are made up of several different materials, none of which have been studied to determine their activation energies, a conservative aging factor (1.8-2.0) is used. This aging factor results in a built-in safety factor; ensuring that enough time under test has been achieved to satisfy the estimate of shelf life...keeping in mind that real time aging studies must be conducted.
When conducting an accelerated aging program for establishing product and package shelf life or expiration dating claims, it must be recognized that the data obtained from the study is based on conditions that simulate the effects of aging on the materials. The resulting creation of an expiration date or shelf life, represents a conservative estimate of shelf life and is tentative until the results of real time aging studies are completed on the product or product/package combination.
Since the results of the study produce a conservative estimate of the actual shelf life of the materials, tolerances for the temperature and humidity are only provided to ensure that the chamber operates within a satisfactory range. Out of tolerance excursions for less than 6 hours in duration for either temperature or humidity are acceptable and do not adversely affect the estimate for shelf life.
Out of tolerance excursions may be caused by opening doors for sample transfer; inserting moist samples into a dry environment causing spikes in humidity; proximity of monitoring device to temperature and/or humidity source inlets.
MPMN: What is the most common defect found in products while undergoing testing?
Nolan: When performing medical device package validations the most common defect resulting from subjecting the packaged devices to the hazards of manufacturing, sterilization, handling and storage is the loss of sterile integrity due to pinholes, slits, cuts, and tears of pouch packages and fractured plastic in thermoforms. These defects occur from the impacts caused by dropping packages and general handling or mishandling, as well as from the vibration forces inherent in the distribution environment.
Some defects like tears are caused from the manufacturing/assembly process; for example during insertion of pouches in cartons, or insertion of IFUs with sharp edges (staples) that ‘snag' the plastic materials.
MPMN: How can companies avoid or prevent this defect from occurring in their products?
Nolan: Companies can reduce and avoid defects in packages due to handling and shipping by designing sterile barrier systems (primary packages) and package systems (final packages) that reduce the possibility of creating pinholes, tears and fracturing.
Pinhole defects in pouches can be reduced by inserting the pouch into a carton without folding, wrinkling, or creasing the ends. Pinholes occur at the junctures of the creases and folds when they are vibrated causing the intersection to be worked or fatigued at the juncture. This effect is exacerbated by making complex folds of the pouch causing a very concentrated point of stress at the juncture of the materials
Fracturing of thermoform trays is usually the result of using the wrong plastic material for the intended product (e.g. product mass is too great for impact resistance of plastic). For large, massive products, high impact resistant plastics such as polycarbonate should be used to reduce the possibility of fracturing during normal distribution and handling. The thermoform design is also critical to ensure that the product is held in place firmly so that a loose product does not jettison through the tray lid or cause fracturing of the plastic from the inside-out.
If fracturing cannot be avoided by material selection alone, then some provisions for cushioning the thermoforms must be considered. Cushioning is most effective at the sterile barrier system level where the cushioning is used around the thermoform tray and inside a carton. Alternatively or in addition, cushioning materials may be used at the package system (shipping unit level) to cushion cartons of products, rather than at the sterile barrier system.
MPMN: What is the biggest trend in product testing right now?
Nolan: Speaking in terms of package testing, the biggest trend within the medical device industry is the greater scrutiny they are receiving from the regulatory community on package validation testing and data. More and more inspections are including requests to review package process qualification and package design validation data. As a result, the importance of compliance to the ISO 11607 standard is growing.
Another trend is the development of new, and revision of current test standards to be more accurate and precise. This is prevalent in the scrutiny package validation test data is receiving from corporate quality assurance departments and this coincides with the increased scrutiny from FDA or other regulatory bodies. This increased precision results in higher validation costs and longer times to complete validations and go to market.
Finally, there is a trend for performing environmental challenge testing on package systems whereby the packages are subjected to extremes in temperature and humidity conditions. These tests are performed prior to dynamic testing such as distribution simulation testing. They are also being performed outside the objectives of accelerated aging protocols.
MPMN: What do you identify as the biggest obstacle existing in the testing and inspection industry today?
Nolan: The biggest obstacle existing within the testing and inspection industry is the lack of awareness by companies of the need to perform testing on package systems. Many companies are not even aware that the ISO 11607 standard exists and is used by FDA and the European Community within their regulations. In addition, many companies cut corners and try to complete package validations ‘on the cheap' without using good, sound scientific practices.
MPMN: What changes in the testing and inspection industry do you anticipate in the next five years?
Nolan: Most changes in the testing industry come about through either regulatory mandates or through development of new technologies. Package testing for medical devices will continue to be viewed as a precise science, much like analytical chemistry; but in reality, it is more art than science. In fact, the need for packaging to be as precise as analytical chemistry is unwarranted, as the main objective is to deliver the product to the end user in a condition that will meet its performance specifications and will also be acceptable for its intended use.
There will be changes in ASTM test standards such as F88 for “Seal Strength of Flexible Barrier Materials” in which there has recently been an updated precision and bias statement added.
There will be changes to the ASTM F1980 standard for “Accelerated Aging of Sterile Medical Device Packages,” as more precise and realistic parameters are applied for shelf life studies to determine expiration dates for terminally sterilized packages.
There will be an emphasis to use scientific methodologies and statistically meaningful levels of testing to truly validate the performance of package systems. There will be more inspection, not less.
Copyright ©2006 Medical Product Manufacturing News
