Since the adoption of council directive 93/42/EEC (CD, 1993), the responsibility of classification of medical devices rests with the manufacturers, who must group their products into the previously mentioned four classes in accordance with rules stated in annex IX of the MDD. The Commission of the European Union has issued guidelines for the classification
of medical devices into one of the four risk classes using a decision tree. The rules are based on criteria related to duration of contact between the device and the patient, the degree of invasiveness, and the anatomy affected by the use of the device. The duration of use is divided into three periods: transient use (less than 1 hour), short term use (from 1 hour to 30 days), and long-term use (more than 30 days). A medical device is classified as invasive if it penetrates inside the body, either through the surface of the body or through a body orifice. For the noninvasive devices, contact with blood is an important classification criterion. Modification of the biological or chemical composition of blood increases the risk associated with a device. Active medical devices are defined as those that are driven by electrical energy and differentiated in terms of the amount of energy that they exchange with the body. According to the MDD and the guidelines, the classification rules apply accordance with the intended use of the device, not its technical characteristics. It is possible that two manufacturers would produce similar devices and assign them two different uses. Therefore, the intended, not accidental, use of a device factors into the classification of it. If a user uses a device in a manner not intended by the manufacturer, he or she does so under his or her own ‘responsibility and does not change the class assigned for the conformity-assessment procedure. Whenever there is a doubt as to classification based on the MDD, the manufacturer should ask an NB. If the manufacturer and the NB responsible for the conformityassessment dispute the classification, the manufacturer should refer the matter to the competent authority, which decides the classification according to Article 9 of the directive. In addition, the directive states that the medical device committee is the final decisionmaker in an extreme case. Conformity assessment procedures, as previously mentioned, are the procedures that
must be completed by a manufacturer before the CE mark can be placed on a product and a product placed on the market. It is not feasible to subject all medical devices to the most rigorous conformity-assessment procedures available. A graduated system of control is more appropriate, and a medical device classification system serves to channel medical
devices into the proper conformity-assessment route. For class I devices (simple dressings, corrective glasses, operating tables, and wheelchairs), the manufacturers are entirely responsible for conformity assessment. The manufacturers
must ensure that devices comply with ERs using risk analysis to establish whether any risks present are acceptable. For class I products, the manufacturers must maintain technical documentation and create a declaration of conformity—available to CAs upon request—before placing the device on the market. In the case of class IIa products (syringes, contact lenses, dental filling materials, and hearing aids), the manufacturer is responsible for the conformity assessment during the design of the devices, but an independent certification body must approve the products during the manufacturing stage. Class IIb products (e.g., implants, intraocular lenses, X-ray equipment, anesthesia machines, ventilators, and high-frequency surgical equipment) and class III (heart valves, resorbable implants, and medicated devices) are subjected to certification by an NB at the design and the manufacturing stages. For class IIa, IIb and III devices when a third party intervention is required, the manufacturer may choose between at least two applicable procedures: the certification of products or the certification of the manufacturing system. In the latter case, the
continuous maintenance of the manufacturer’s quality system is subject to a thirdparty certification by an NB. In this context, compliance with European standards (series EN/ISO 29000 in conjunction with EN 46000) facilitates the establishment of conformity.