Rubber components for the medical technology market

Irrespective of whether a molded rubber part functions as a stand-alone medical device or is a component in a medical device – the medical technology market is heavily dependent on molded rubber parts. The manufacture of rubber parts requires a range of considerations to be taken into account, both in terms of the production technology and organization, to ensure compliance in this safety-sensitive sector. What exactly suppliers to the medical technology sector need to pay particular attention to is explained in this blog entry.

In addition to production-specific challenges, we take a close look at aspects such as biocompatibility, quality management and cleanroom production.

The use of rubber in medical technology

Rubber parts are indispensable in medical technology and, in many products a rubber part is the key component without which a medical device would be unable to function.

Since rubber parts are found in countless medical applications, we would like to start by giving a few practical examples and explain their classification.

First of all, there are individual parts, or assemblies of parts, with which people do not come into direct contact, but nonetheless have an essential role to play in the well-being of humans. Diaphragms, rubber valves, gaskets and hoses are elements that are fundamental to the functioning of pumps used in medical technology in hospitals, for example. Diaphragm pumps are deployed in the analysis of gases and also in medical autoclaves to sterilize materials and objects. In other types of pumps, the rubber components contribute to ensuring that for ill patients the risk of pressure ulcers (bed sores) is reduced by the use of air beds. Rubber components are needed to pump fluids; to ensure ventilators supply sufficient oxygen, to power the tools dentists work with and to ensure fluids are removed by suctioning. The handles of surgical instruments are also frequently made of silicone due to its excellent medical grade properties.         

Then there are products that are incorporated into medical devices with which people have direct skin contact. Here again you can differentiate between devices that come into contact with people for a short time and those that are worn in the body or on the body.

For example, silicone patches are utilized in the treatment of wounds. Silicone wound contact layers help to stop wound dressings from sticking to the wound so that changing a dressing is painless. Rubber components in the form of seals, microphone suspensions or receiver mounts are used in hearing aids to improve the quality of life of people with hearing problems. Nowadays, diabetes patients carry insulin pumps that provide a continuous insulin infusion. An insulin pump mimics the function of the pancreas as it intermittently delivers insulin, and as such takes over the management of diabetes. The need for regular injections is eliminated and a patient's blood sugar is regulated and stabilized.

Rubber components in the form of implants are fitted at many sites in the human body. Artificial silicone joints have a role to play in orthopedics. In urology, there are bladder catheters made of silicone and fitted with a silicone balloon (balloon catheters). While the catheter drains urine from the urinary bladder, the balloon’s function is to stabilize the catheter in the urethra. A vagus nerve stimulator may be implanted to treat epilepsy; the outer shell and insulation of the stimulator are made of silicone. The same applies to deep brain stimulation. This is a therapy method carried out, for example, on Parkinson disease. The deep brain stimulation device is commonly known as a brain pacemaker. Silicone is also used as an insulation material in actual cardiac pacemakers. Silicone can be used as anchorage to connect the electrodes of a cardiac pacemaker to heart muscle. Silicone is also used in artificial hearts (ventricular assist devices).

Official classification of medical devices        

Official classification of medical devices, for example, by the European Union (EU) is a complex matter. Nevertheless, we ought to, and would like to, take a look at this issue since classification determines the specifications provided to suppliers and manufacturers of medical devices.

In the EU, medical devices used to be classified according to the Medical Devices Directive 93/42/EEC, but this was repealed by Regulation (EU) 2017/745. The Medical Device Regulation (MDR) replaces the Directive 93/42/EEC. It was adopted on May 25, 2017.

The European Union now makes a distinction between active medical devices, non-active medical devices and medical devices with a measuring function. 'Active' means that the product is powered by an external source.

In addition, medical devices in the EU are risk rated based on the vulnerability of the human body. There are four classes (I, IIa, IIb, and III); I is the lowest class of risk. Risk class III signifies the highest risk potential for humans.

Medical devices are classified according to a variety of criteria. For example, how the medical device is used (in the body, on the body, etc.), duration of use, or whether it is an active medical device.

Table 1: Risk classification and examples of medical devices in the European Union

Classification differs from country to country. For example, in the United States of America, the FDA (Food and Drug Administration) has established three risk classes. Classification is based on the amount of regulation required to ensure a medical device’s safety and efficacy.

Table 2: Risk classification and related examples of medical devices in the United States (USA)

In the two tables above, particularly in respect of the examples of medical devices, it should be noted that neither the EU directives nor national legislations determine the risk class. Classification is carried out by the manufacturer for each individual product according to its intended use.

Irrespective of the official classification into the various risk classes and the different national interpretations, the consequences and requirements for the manufacturers of medical devices and their suppliers are very similar. In general, it can be said that the more risky or vitally important the medical device is for humans, the greater the requirements.

Material and manufacturing process requirements for the production of rubber parts for the medical technology sector

When manufacturing rubber parts for the medical technology sector, manufacturers are faced with specific demands on the quality of the products and the conduct of their personnel.

Suppliers or manufacturers of OEM products designed to increase the quality of life and, in many cases help to save lives, bear extra responsibility. In production, this requires exact processing, high precision, tight tolerances and an exceptionally high level of reliability.

Personnel have to be trained regularly and familiarized with the manufacture of medical devices.

In the following, we discuss in detail three specific topics with which manufacturers or suppliers of medical products are regularly confronted:

Biocompatibility - USP Class VI und ISO 10993

Biocompatibility is a term for the properties of materials, assemblies or products that have no negative impact on humans or living tissue in general. Accordingly, materials in direct or indirect contact with the human body must not harm the user, must be free of hazardous substances and have no side effects.

Biocompatibility is not always required for rubber components or their materials. The crucial factor is the extent to which the molded parts come into contact with the human body. For example, if diaphragms or seals made of EPDM or FKM are used in medical pumps, biocompatibility will not necessarily be a requirement. However, the extent to which the pumped medium comes into contact with the human body is important.

Biocompatibility is compulsory in many medical applications. Silicone tends to be the elastomer of choice for such applications. Silicone fulfills the requirements of biocompatibility more often and more easily than other materials. When testing for biocompatibility, a distinction is made between silicones that have been tested for some levels of biocompatibility, medical grade silicones and long-term implant silicones depending on the type of application. Material manufacturers have to comply with various regulations regarding production and documentation. For example, in the case of medical grade silicones and long-term implantable silicones, datasets (device master files or master access files) are deposited with regulatory authorities, such as the FDA. They contain information about the composition of the material, its processing and testing. The guidelines can then be used by the manufacturers in the approval process for medical devices.

Verification of biocompatibility is carried out by test procedures according to the methods in the two guidelines: USP Class VI and ISO 10993. A low USP Class rating of I to V may be sufficient for components that do not have particularly stringent biocompatibility requirements.

The ISO 10993 is much more wide-ranging and was intended to supersede the testing guidelines of USP Class VI (United States Pharmacopeia Class VI). However, the USP Class VI test is still widely used and frequently applied in testing elastomers. Enforcement of USP guidelines is the responsibility of the American FDA.

Although the test procedures of the two guidelines are different, both require verification of compatibility of a particular product or material with the human body. For example, pyrogenicity, hemocompatibility, mutagenicity/genotoxicity or cytotoxicity is tested.

Classification according to ISO 10993 is more complex, more elaborate and more expensive. In most cases, however, verification and classification of biocompatibility according to USP Class VI is sufficient.

Incidentally, proof that a (raw) material is biocompatible is generally not enough for medical device manufacturers. Evidence must be provided to the regulatory authorities that the entire medical device is biocompatible and thus compatible with humans. This is to ensure that there are no negative effects resulting from the intermediate manufacturing processes.

Quality management - EN ISO 13485

Manufacturers of medical devices and suppliers to the medical technology sector are subject to particularly strict rules , since the quality of their products affects the quality of life of many people and in fact the sustainability of their lives. The quality of a product has a central influence on its effectiveness and thus the safety of patients.

It is for this reason that manufacturers in this area must fulfil specific requirements regarding the quality of products and processes. A company must therefore implement an appropriate quality management system in which processes specifically geared to the requirements of the medical sector are defined, described, implemented, documented and then applied and lived by personnel. 

EN ISO 13485 Medical devices: Quality management systems - Requirements for regulatory purposes is the standard representing the requirements for a comprehensive management system.

The standard EN ISO 13485 specifies the requirements for the manufacture and authorization of marketing of the market of medical devices, and components of medical devices. It details the requirements OEMs and medical device suppliers have to meet in developing, implementing and maintaining a quality management system, including requirements set by customers, government agencies and regulators. Depending on the risk classification of the medical device, implementation of a quality management system following the specifications of EN ISO 13485 is mandatory for manufacturers, and also includes compliance with EU directives such as 93/42 / EEC or its successor, the Ordinance on Medical Devices (EU) 2017/745

The standard touches on all areas of a company that are relevant to product quality. For instance, it looks at how individual processes should be prepared, verified and documented, how documents are designed, how they are stored, how process should be tracked, management responsibility, training requirements for personnel, how to deal with customer complaints, how to validate products and processes and how to improve processes based on the data collated. The entire company should be organized accordingly and personnel made aware that the products they manufacture must be of a quality standard to meet medical needs.

Many companies in the industrial sector are familiar with the EN ISO 9001 standard with regard to quality management systems. Basically, EN ISO 13485 is similar to this standard but contains additional, specific requirements for medical devices and is therefore worded differently. The major difference is that EN ISO 9001 focuses on the continuous improvement of companies, whereas EN ISO 13485 focuses on product safety. The requirements of EN ISO 13485 are designed to ensure that a company's processes are safe regarding the safety of a product for a patient.

A quality management system complying with the requirements of EN ISO 9001, in most cases, is therefore insufficient for the medical sector.

The manufacturer or supplier has to undergo regular independent audits and certification for its quality management system to comply with the requirements of EN ISO 13485 and to release the product to the public. Accredited companies such as the German TÜV Süd, TÜV Rheinland or Dekra carry out such certification. For the manufacturers and suppliers of medical devices this means increased expenditure and work, but at the same time offers the opportunity to improve product quality and optimize process flows.

EN ISO 13485 certification is also recognized in the United States by the Food and Drug Administration (FDA). In the USA, the FDA is responsible for approval of medical devices and it checks whether a company fulfills the quality system requirements (QSR) necessary for the medical sector.

Cleanroom - EN ISO 14644

If the molded parts made of silicone or other rubbers are made for use in a medical technology application and the medical device is classified as high-risk, the articles may have to be made and finished in a cleanroom to minimize contamination with foreign particles. It is important to ensure that the entire process takes place in the cleanroom under appropriate conditions, that is, from the preparation of the (raw) material to the packaging of a rubber component. Handling of the raw material poses the greatest risk of contamination.

Cleanroom requirements are defined in the standard EN ISO 14644. This standard classifies cleanrooms according to their air purity based on the particle concentration into different cleanroom classes. The classification according to EN ISO 14644-1 recently superseded the old US Federal standard 209E. Customers from the US still often use the classification according to the old US standard in their inquiries.

Table 3: Cleanroom classes according to ISO 14644-1

Medical devices intended for implantation (risk class III) generally require at least a class 7 cleanroom. In some cases even a class 5 cleanroom is needed.

The cleanroom must be appropriately designed and technologically equipped to comply with the standard and the requirements of a manufacturer of rubber parts used by the medical sector. The aim is to avoid contamination by foreign particles and comply with the EN ISO 14644-1 standard.

Basically, this is achieved by controlling the air movement (generating negative pressure) in cleanrooms and HEPA filtering of the supply air into the room.

A critical source of contamination is people. Personnel must therefore don appropriate clothing and develop an awareness of correct behavior in a cleanroom.

If you have any questions or comments on this blog, or in future would like us to focus on a specific aspect of elastomers, feel free to contact us by email at info@hepako.de

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