Page 224 - Biomedical Engineering and Design Handbook Volume 2, Applications

STERILE MEDICAL DEVICE PACKAGE DEVELOPMENT 203

This test method may apply to very large or long packages, which do not fit into any other package
integrity test method apparatus.
This test method may be used as a means to evaluate package integrity. Package integrity is crucial
to consumer safety since heat-sealed packages are designed to provide a contamination free and sterile
environment to the product.

The advantages of using this method for determining package integrity are that it is very easy to per-
form the test, and it is inexpensive to test a large sample size and obtain statistical significance in the test
sample set. The equipment costs are low since all that is required is a pressure source and a water bath.
This method has been validated by round-robin testing, and a precision and bias statement has
been developed for its repeatability and reproducibility. Its sensitivity for detecting leak size has been
found to be 0.010 in (250 μm) with an 81 percent probability. Gross leaks such as 0.010-in pinholes
occur most often as a result of handling and distribution hazards that cause tears, gouges, and punc-
tures. Package validations most often fail as a result of the rigors of shipping and distribution. This
test is sufficiently sensitive to detect those types of defects caused by the hazards of distribution. Leaks
in seals and in material surfaces can be detected using this method. If the method is validated for each
package type, it may be possible to consistently detect holes as small as 0.005 in (125 μm).
The method can be used for both porous and nonporous packaging materials. For packages with
porous materials, the porous material substrate may be sealed using a label or coating to reduce the
porosity of the material. This facilitates the pressurization of the package and reduces the interpre-
tation of what constitutes a leak and where a leak is occurring in the package. The porous material
is not evaluated for leakage as the coating may mask or block leaks in that component of the sterile
barrier system. However, pinholes, tears, gouges, and channel leaks are readily apparent under a pre-
determined and validated internal pressure that does not begin to separate the seals.
Validation of the method for the package under investigation must be performed to determine the
proper internal pressure and the sensitivity of the method, and to evaluate the ability to detect chan-
nel and pinhole leaks over the permeation of any air through the porous substrate.
Vacuum Leak Test. The vacuum leak test is similar in concept to the internal pressure leak test
in that the result is a pass/fail for the detection of bubbles emanating from the package while sub-
mersed in a water bath. The method is described in ASTM D3078-02, “Standard Test Method for
Determination of Leaks in Flexible Packaging by Bubble Emission.” The pressure differential is
obtained by evacuating the chamber, causing the package to expand due to its internal pressure. This
test method covers the determination of gross leaks in flexible packaging containing a headspace gas.
3
–6
–5
3
Test sensitivity is limited to 1 × 10 atm cm /s (1 × 10 Pa m /s) or even less sensitive.
The difficulty in using this method for porous packages is that the pressure differential may not
reach a point at which air passes through a channel or material leak before air passes readily through
the porous material. Lowering the porosity of the material by coating it with a lacquer or other means
could reduce this problem. This test is more suitable for nonporous packages where internal pressure
will force air through leaks.
Dye Penetration Test. The ASTM F2 Committee first published a dye penetration test method
in 1998, which has become an important method for determining the integrity of sterile barrier sys-
tem seals. The standard, designated as F1929-98(2004), “Standard Test Method for Detecting Seal
Leaks in Porous Medical Packaging by Dye Penetration,” provides a standardized method for con-
ducting leak testing of package seals using a low surface tension solution and dye indicator. The
“Significance and Use” section of the standard describes the standard’s intent as follows:
Harmful biological or particulate contaminants may enter the device through leaks. These leaks are fre-
quently found at seals between package components of the same or dissimilar materials. Leaks may also
result from a pinhole in the packaging material.
This dye penetrant procedure is applicable only to individual leaks in a package seal. The presence
of a number of small leaks, as found in porous packaging material, which could be detected by other tech-
niques, will not be indicated.
There is no general agreement concerning the level of leakage that is likely to be deleterious to a par-
ticular package. However, since these tests are designed to detect leakage, components that exhibit any
indication of leakage are normally rejected.