The Top 7 Considerations in Reusable Device Design

Medical products can be defined based on their intended use either for use on a single person (single use) or with multiple people over time (reusable). For reusable items, it is important that they can be safely used on each patient for the designed life of the device. Such devices can range from high-risk surgical devices that contact “sterile” areas of the body, including the blood, to devices that only may touch the skin of healthcare workers or their patients. It is routine practice in healthcare facilities to ensure these devices are safe for every patient by routine processing, according to defined instructions provided by manufacturers. Processing (or reprocessing) can be defined as a single or series of steps to ensure that a device is rendered safe for handling, use on a patient or disposal.

Safety aspects include the reduction or removal of disease-causing microorganisms (due to the risk of infection), toxicity, electrical or mechanical failure, and other adverse patient or staff events that may occur during the use of a damaged or malfunctioning device. These incidents frequently are identified and in some cases are dramatic to patient health, healthcare facilities and manufacturers. This has been highlighted by many regulatory authorities worldwide, most recently by the U.S. Food and Drug Administration (FDA) in its 2011 joint summit with the Association for the Advancement of Medical Instrumentation (AAMI) on medical device reprocessing. Adverse patient events have reinforced the need for device manufacturers to consider any processing needs early in product design. Equally, designers need to ensure that practical and validated instructions for processing are provided in user instructions to ensure safe use of the device each time.

Figure 1. The various device life cycles in clinical use. Reusable devices can go through continuous reprocessing cycles and to various degrees depending on their risk to patient safety.

The various steps in clinical processing of reusable devices can be summarized as shown in Figure 1, depending on the risk of using the device with a patient. These steps can include cleaning, disinfection, packaging and sterilization. While these steps may appear straightforward, they often are overlooked during the various stages of device design. Manufacturers often provide inadequate processing instructions that do not meet local or international requirements, regulatory or customer demands. In the past this may have led to customer dissatisfaction, but simply often could mean the device may not be allowed to be used in regulated healthcare facilities. The risks to these facilities are many and include patient or staff adverse incidents, the extreme of which can include prolonged recovery, infections and in some cases death.

This article will review the top seven items to consider from a reprocessing point of view in the design and commercialization of reusable instrumentation.

1: Compliance to ISO 17664
ISO 17664 is an international standard that describes the information to be provided by the manufacturer for the processing of re-sterilizable medical devices. It defines recommendations to manufacturers on the development of processing instructions so the device can be processed safely in clinical practice and will continue to meet its performance specification. Although the current version of the standard is specific to devices that require sterilization, the standard is under revision to include a wider range of devices (such as those that may require routine disinfection).

This standard should be considered early in the design of a reusable device to understand the potential use and reuse of the device, as well as in the preparation of regulatory registrations and preparations for commercialization. The endpoint is consistent instructions for use (IFU) that allows the routine safe and effective use of the device.

Typically, design of a medical device centers on the physician’s use of the technology. However, more than the physician alone routinely handles a reusable medical device. Devices need to be designed with others in mind such as nursing staff and processing technicians that perform the required disassembly, cleaning, disinfection, inspection, assembly and, if applicable, packaging and sterilization of the device for next use. It also is important to understand the environments in which the users are working and any restraints including time, equipment and tools. In addition, it is important to remember that these practices can vary from country to country. By understanding the potential markets for the device, meaningful IFUs can be developed to meet these customer requirements.
With recent changes in regulatory environments around reusable medical products, device manufacturers should expect the healthcare facilities in which their devices are sold to be closely inspected (sometimes as part of the decision to buy the device) and following their written instructions. With this in mind, the instructions should be written in a manner that is clear and easy to follow. It also is recommended that IFUs be consistent and describe not only what to do, but what not to do to avoid damage to the devices through the reprocessing cycle. A typical format will include:

• Warnings and limitations;
• Point-of-use handling;
• Containment and transportation;
• Cleaning (manual and automated methods);
• Disinfection;
• Drying;
• Maintenance;
• Inspection and testing;
• Sterilization (if applicable); and
• Manufacturer contact.

2: Risk Analysis
Risk analysis is an essential practice during the design and development of devices and should include processing requirements when labeled as reusable. The risks to patients and clinical staff need to be considered under both normal and fault conditions. Such risks may include a variety of mechanical, electrical, chemical or biological considerations. In the current revision of ISO 14971, “Medical Devices: Application of Risk Management to Medical Devices,” reference to cleaning, disinfection and sterilization in healthcare settings is addressed in two questions in Annex C. This reference does not provide significant guidance to assess the risk to patient and staff during processing. Examples of risks will include the impact of the use of different types of cleaning and disinfection chemicals on the structural integrity of the device or toxicity impact on the patient, cross contamination with disease-causing microorganisms (pathogens) and ease of device handling (e.g., access to internal device components that may be contaminated during use). A close and thorough evaluation of the hazards associated with processing should be addressed.

The customer instructions generated should reflect the results of the risk analysis to include specific warnings and precautions applicable to processing. The IFU should give clear guidance on what to avoid during cleaning, disinfection and sterilization, but also provide instruction on what to do to avoid device damage or patient/staff hazards.

3: Material Compatibility
All devices should have an expected life based on their design. This can range from single use (used only once and discarded), single person use (used only for one person, but potentially many times), reposable devices (with a short, defined number of times the device can be reused) and reusable devices (that can last from weeks to years). Furthermore, certain parts of the device may be expected to have a reasonably short life (such as certain types of flexible endoscopic instruments) and be expected to be repaired within a reasonable number of patient uses/reprocessing cycles, while the remainder of the device parts are expected to have a longer shelf life.

When designing devices, the expected life cycle not only should consider the patient use of the device, but the variety of types of physical and chemical procedures that are expected to be used on the device during reprocessing. A variety of chemical products typically are used for cleaning, particularly various types of surfactants, enzymes and, in some countries, high alkalines. An important but often overlooked consideration is the ability to be able to immerse the device in water, a requirement for many types of reusable devices during reprocessing. Other limitations may include the safety in using ultrasonics for cleaning. For disinfection and sterilization, specific compatibility examples will include heat (in excess of 70 degrees Celsius), pressures (positive pressure for steam sterilization and negative pressures for gas-phase chemical sterilization processes), various chemicals (e.g., alcohols, aldehydes, oxidizing agents, etc.), light sources (ultraviolet [UV]) and moisture. Typical watch-outs include adhesives and sealants, anodized surfaces, soft metals and the quality of stainless steel, plastics or elastomers used. Where specific physical conditions or types of chemicals could damage the device materials or function of the device, these clearly should be indicated in the instructions for use. The instructions should give examples of the chemicals and processes that are compatible with the device, as well as types that are not. This will allow for the greatest flexibility in adopting the device instructions into the greatest range of facilities worldwide.

4: Cleaning Efficacy
There has been a growing emphasis on the efficiency of device cleaning, particularly in the United States since 2011 with the release of the FDA’s draft guidance on the processing of devices in healthcare settings. This document highlights the importance of processing instructions in device design and registrations, but also launched a new paradigm to evaluate cleaning efficacy through the use of chemical endpoints. Although existing ISO and AAMI documents describe limits and monitoring of chemical residues for cleaning, many medical device manufacturers selling into the U.S. market are demonstrating cleaning efficacy using a bioburden reduction method. There is an ongoing, international effort to define and harmonize the requirements for cleaning endpoints and cleaning validation methods.

Cleaning of a device in most cases starts immediately after the device has been used, removing gross contamination at a place convenient to the point of use. This first step in the cleaning process plays an important role in the subsequent cleaning steps. Cleaning steps must be considered carefully based on knowledge of how the device is clinically used, the probable soil the device will encounter, cleaning methods and the variety of cleaning chemistries used in healthcare settings. Cleaning chemicals include various types of acid, neutral and alkaline-based formulations, but consideration also should be given to the impact of water quality used (e.g., chlorine and water hardness are common problems) and any method (manual or automated) that is recommended during the cleaning process (e.g., use of ultrasonics, brushes, automated washer-disinfectors, etc.). Device safety and compatibility particularly is important to consider at this stage as cleaning is a common source of device damage (due to physical and chemical effects).

5: Antimicrobial Efficacy
Reusable medical devices are a common source of pathogenic microorganisms that can lead to patient infections. The true rates of infections caused by the inappropriate processing or use of devices is not known, but recent evidence would suggest that the occurrence is underestimated (e.g., Ofstead et al, 2013). In infection prevention, devices are classified as being critical, semi-critical and non-critical. This system is widely known as the Spaulding Classification, from the name of the person that popularized it in the 1950-1960s. A summary of the classification is shown in Figure 2 (below).

*Note: The specific effects of antimicrobial products and processes are validated according to regional and international regulatory requirements and can vary significantly.

Critical devices with the highest risk, including many types of surgical devices, contact sterile areas of the body. Such devices should be sterile (free from microbial contamination). Semi-critical devices often are considered a lower risk as they contact mucous membranes or non-intact skin (e.g., certain types of gastrointestinal endoscopes and other diagnostic devices). It is preferred that these devices also should be rendered sterile before use, but they often are subjected to a high-level disinfection process, which should, in theory, inactivate or remove most, but not all, disease-causing microorganisms.

The remaining devices are considered non-critical and low-risk because they only contact intact skin, which has natural barrier properties. Such devices routinely are subjected to gross cleaning (to remove visible soil) and/or some disinfection (generally using products with inactivation claims against some notable bacteria and viruses, but overall less effective than high level disinfection). Despite that, the overall risk will depend on many factors such as patient risk factors, staff contact (as the device can be a source of contaminating microorganisms to hands and gloves that can be transferred from person to person), where the device is used (e.g., in a general ward or an intensive care unit), and infection prevention best practices.

The most widely used method for device disinfection/sterilization in healthcare facilities is moist heat, ranging from approximately 70 to 138 (steam under pressure) degrees Celsius. The widespread use of these methods often is included in the design specification for a device, but can be restrictive due to the tolerances required for heat and even pressure requirements on the materials used. Radiation methods are not widely used, with the exception of UV-based disinfection systems. As alternatives, a wide variety of registered chemicals or chemical-based processes can be used, particularly for devices that are thermo-sensitive. There is a growing number of chemical processes, particularly those based on oxidizing agents, that are used in these cases both for disinfection and sterilization, and in many cases can add many advantages over steam sterilization (e.g., material compatibility, reprocessing cycle time, costs etc.).

Disinfection and sterilization processes usually are developed, tested and commercialized in accordance with international and/or national regulatory requirements. These processes can vary significantly, as do the practices in various countries regarding their use. An understanding of these processes will influence the design, risk analysis and development of the instructions for use to ensure the safe and effective use of the device worldwide.

6: Toxicity and Safety
The goal of device reprocessing is to render a device “safe” for reuse. Although the definition of safe often focuses on aspects such as mechanical or electrical safety, as well as ensuring that the risks of microbial contamination are reduced, in recent years particular emphasis also has been placed on other biological hazards such as toxicity, irritation, sensitization and even carcinogenicity. These requirements are an important consideration in the basic design of the device, such as those outlined in the ISO 10993 series of standards. This not only will include the choice and manufacturing of materials used in the device, but also risks associated with reuse of the device. The variety of chemical or physical methods used in device processing can play a role both in potentially modifying the construction materials over time or potentially remaining on the device that can lead to toxic effects on patient use.

Examples of toxicity reports due to inadequate processing have included:

• Residuals of glutaraldehyde and ortho-phthalaldehyde, chemicals widely used for high-level disinfection of semi-critical devices, leading to colitis or other toxic effects in patients due to inadequate rinsing of devices following disinfection (Ahishali et al, 2009; Sokol, 2004).
• Episodes of toxic anterior segment syndrome from residuals of water and/or cleaning chemistry residues on optamological devices following eye surgery (Johnson, 2006).
• Potential rejection of orthopedic implants due to residues from cleaning of surgery sets in clinical practice (Alfa, 2012).
• Biological impact of residuals from ethylene oxide sterilization methods (Buben et al, 1999).

Toxicity in patients can be due to various biological or chemical residues that can remain on the device following its use and subsequent processing, highlighting the need for adequate cleaning, rinsing and disinfection/sterilization in accordance with validated instructions provided by the manufacturer. These risks should be considered during the design of the device and will depend on its intended use. An unusual but potentially serious example that may briefly be considered are the risks associated with devices specifically designed for use with neural tissues, such as the brain, spinal cord or optic nerve.
There are a series of transmissible protein-precipitating diseases, commonly known as prion diseases such as Creutzfeldt–Jakob, that require special handling when presumptively identified in patients undergoing such procedures. Due to the risks associated with transmission of these diseases on medical device surfaces, specific instructions may be required on how to handle any potential contamination to ensure that the risks are safely reduced to subsequent patients (McDonnell, 2008).

7: Human Factors
In recent years, the focus on human factors has intensified. The intent of human factors engineering and usability engineering is to understand and optimize how people interact with technology. This understanding helps device manufacturers recognize use-related hazards by understanding how the device is used. Considerations will include those handling the device, use environment and device/interface. The focus of human factors traditionally has been around the actual use of the device during a procedure and the physician’s interaction with the device. Human factors also should be considered in the processing of reusable medical devices to include limitations of the use environment, education and training of the processing technicians, the volume and broad range of devices processed in a healthcare facility, tools and equipment available in the healthcare facility, and standardized instructions for processing that meet local requirements. The initial design and development of the device can impact this.

When developing a reusable device, it may be useful to consider the healthcare worker who has to disassemble the device in a busy, demanding environment, wearing personal protective equipment that may limit dexterity and/or vision. Further simple steps can include design features that allow the device to be assembled only in one way, or photographs that provide clear instruction on the disassembly or inspection of a device. Clarity in instructions is important. Instructions should be performable in a healthcare setting using commonly available chemical agents, equipment and methods. They also should be provided in a consistent structure using short, direct statements written in simple and familiar words to reduce the risk of user error when processing multiple devices from various manufacturers. Human factors are vital to consider in the development of sterilization processes.

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Overall, reusable device manufacturers are being encouraged to take a closer look at processing requirements earlier in the development process and providing clear, written and validated instructions for use (and reuse) to healthcare facilities. The greater regulatory focus on this aspect, in the United States and internationally, highlights the importance of this aspect in the safe and effective use of such devices on a daily basis in these facilities. Processing instructions not only are required to meet standard requirements but are an essential part of customers’ requirements, with reputation and commercial benefits to device manufacturers.

Sources Consulted

• AAMI TIR30:2003. A compendium of processes, materials, test methods, and acceptance criteria for cleaning reusable medical devices.
• AAMI (2011). Priority Issues from the AAMI/FDA Medical Device Reprocessing Summit (www.aami.org/publications/summits/2011_Reprocessing_Summit_publication.pdf).
• Ahishali et al (2009). Chemical colitis due to glutaraldehyde: case series and review of the literature. Dig Dis Sci. 54:2541-5.
• Alfa (2012). The ‘pandora’s box’ dilemma: reprocessing of implantable screws and plates in orthopedic tray sets. Biomed Instrum Technol. Spring Suppl:55-9.
• Buben et al (1999). Problems associated with sterilization using ethylene oxide. Residues in treated materials. Cent Eur J Public Health. 7:197-202.
• ISO 10993-1. Biological evaluation of medical devices—Part 1: Evaluation and testing.
• ISO 14971. Medical devices-Application of risk management to medical devices.
• ISO 15883-1. Washer–disinfectors, Part 1: General requirements, definitions and tests.
• ISO/TS 15883-5. Washer–disinfectors, Part 5: Test soils and methods for demonstrating cleaning efficacy of washer–disinfectors.
• ISO 17664. Sterilization of medical devices—Information to be provided by the manufacturer for the processing of resterilizable medical devices.
• U.S. Food and Drug Administration (2011). Draft Guidance for Industry and FDA Staff—Processing/Reprocessing Medical Devices in Healthcare Settings: Validation Methods and Labeling.
• U.S. Food and Drug Administration (2011). Draft Guidance for Industry and Food and Drug Administration Staff—Applying Human Factors and Usability Engineering to Optimize Medical Device Design.
• Johnston (2006). Toxic anterior segment syndrome—more than sterility meets the eye. AORN J. 84:969-84.
• McDonnell & Sheard (2012). A Practical Guide to Decontamination in Healthcare. Blackwell Publishing, a division of John Wiley & Sons.
• McDonnell (2008). Prion disease transmission: can we apply standard precautions to prevent or reduce risks? J Perioper Pract. 18:298-304.
• Ofstead et al (2013). Re-evaluating endoscopy-associated infection risk estimates and their implications. Am J Infect Control. 41(8):734-6.
• Sokol (2004). Nine episodes of anaphylaxis following cystoscopy caused by Cidex OPA (ortho-phthalaldehyde) high-level disinfectant in 4 patients after cytoscopy. J Allergy Clin Immunol. 114:392-7.

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Dr. Gerald McDonnell is vice president, Research and Clinical Services, for Mentor, Ohio-based STERIS Corporation, a provider of infection prevention, contamination control and surgical support products and services. He also is a consultant with Biotest Laboratories in the design, development and testing of reusable devices and their instructions for use. McDonnell holds a B.Sc. (Hons.) in medical laboratory sciences and a Ph.D. in microbiology. He is a frequent presenter on infection prevention with more than 160 publications and patents in the area, including a new book published in 2012 titled “A Practical Guide to Decontamination.” He is an assistant editor for the Journal of Hospital Infection and a reviewer for a number of other leading journals on infection prevention/control topics. McDonnell is a member of national and international working groups, including AAMI, ISO and EN committees, for standard and guideline development on areas including sterilization, disinfection, cleaning and aseptic processing. He is the current convener of CEN TC 102 WG8 (washer-disinfectors) and a visiting professor at Tokyo Healthcare University.

Beth Jacques is manager, Compliance for Biotest Laboratories in Brooklyn Park, Minn. She has a B.Sc. in biotechnology, chemistry and microbiology. Jacques has held various laboratory, quality and regulatory positions attributing to her more than 20 years of experience. Her expertise has lead to the launch of the reprocessing of reusable medical devices initiative at Biotest Laboratories, and she is involved in the AAMI standards organization in the areas of microbial management, human factors for device reprocessing, and steam sterilization in healthcare facilities.

To contact the authors with questions about this article, please email [email protected].