Biomedical Engineering Reference
In-Depth Information
their bulk form. Preliminary results indicate that there are no cellular toxicity effects and
the risk of clotting is only slightly increased with these conventional materials used in
medical devices [3]. One approach, in using noncompatible medical devices
in vivo
, relies
on isolating medical devices from the body by packaging them in biocompatible poly-
mers although this can add to the size of medical devices and reduce their accuracy. To
overcome these issues, nanoparticle coatings and biocompatible polymer micromachining
need to be investigated further.
Packaged medical devices must be able to survive the sterilization procedures used in
the surgical environment and preferably be able to withstand exposure to high temperatures
and moisture in autoclaves and steam sterilizers. Alternative sterilization methods include
ethylene oxide (ETO) and irradiation. ETO is a harsh organic solvent and packaging must
be made of a compatible material. Medical devices are inherently radiation hardened, but
their associated electronics are not, so they must be specially designed using radiation-
hardened IC processes and packaging.
Since it is important to ensure that medical devices and products remain sterile in the
packaging throughout distribution, in order to allow their immediate use by physicians,
medical device packaging is highly regulated. A series of special packaging tests is used
to measure its ability to maintain sterility. Some of the relevant standards include: ASTM
F1585-Guide for Integrity Testing of Porous Barrier Medical Packages [4], ASTM F2097-
Standard Guide for Design and Evaluation of Primary Flexible Packaging for Medical
Products [5], EN 868 Packaging materials and systems for medical devices which are to
be sterilized [6], General requirements and test methods, and ISO 11607 Packaging for
Terminally Sterilized Medical Devices [7].
Designing well-controlled prospective clinical trials of medical devices presents unique
challenges that differ from those faced in the study of pharmaceuticals. For example,
clinical effects observed in medical device studies are influenced not only by the product
under evaluation and the patients themselves, but also by the skill and discretion of
the user, who is typically a health care professional, but who may also be the patient.
The impact of this parameter (the medical device user) is a variable unique to medical
device studies and can be responsible for the greatest degree of variability in clinical
outcomes. One critical variable that requires attention in designing a clinical study is
being aware of the extent to which the user is able to influence and control the device
performance [8]. As indicated, hemocompatibility and biocompatibility, being resistant
to sterilization procedures and user parameters, currently are the most important clinical
issues for medical devices.
12.2 Regulatory Issues
The furtherance and control of quality is a major issue in health care. It is also one of
the aspects of health technology assessment which, in large part, consists of the quality,
safety, and effectiveness of medical devices that are employed in diagnosis and treatment.
Medical devices, of which surgical tools and telesurgical systems are subsets, are subject
to many regulatory controls. The FDA and European Community (EC) determine whether
a product is fit for sale in the United States and Europe, respectively. The regulation of
medical devices is a vast and rapidly evolving field that is often complicated by legal
