We currently live in unprecedented times; the global spread of coronavirus has led to a dramatic increase in hospitalizations and a renewed focus on protecting our healthcare workers. Personal protective equipment, more commonly known as PPE, is being consumed faster than it can be produced, with suppliers struggling to keep up with demand. To help meet the growing need, companies with manufacturing capabilities in other industries have been converting their existing facilities and equipment to begin producing PPE and other medical supplies. Regardless of the pace of production, quality control testing is still required to ensure that the products being sent to our front lines will perform as required.

The Current Situation

In the United States, manufacturers of PPE typically need to submit premarket notification to the Food and Drug Administration (FDA) that they will be producing medical-grade products. The FDA is the main regulatory body overseeing the production and distribution of PPE, and it sets quality requirements based on the product’s application. The level of FDA involvement depends on the class of the device, which can range from Class I to Class III based on the device’s potential risk of nonconformance. Most types of PPE are labeled as Class I devices with the fewest barriers to approval, but certain gowns and coverings used in surgery are labeled as Class II. This amount of regulation and quality control is vital to ensuring the products work as intended, but it can also make the amount of time and effort needed for a new manufacturer to achieve compliance feel insurmountable.

As hospitals scramble to secure PPE to meet their increasing needs, many companies inside and outside of the biomedical industry are shifting their production capabilities to help address the sudden demand. However, the amount of time required to gain FDA approval can be months or even years in some instances, negating these efforts. To minimize this hardship, the FDA issues something called an Emergency Use Authorization (EUA) in times of health crisis. The EUA essentially loosens the requirements for production and distribution of certain medical products, allowing production to ramp up quickly.

Acceptance ranges highlight tests that fall out of specification, and visual indicators allow for easy identification of failed specimens.

EUAs are currently being granted to manufacturers of COVID test kits, virus therapies, ventilators, respirators, and PPE. These EUAs are generally granted to specific companies that apply to expedite the approval process, but they are also being released as blanket statements covering certain types of PPE. Additional documentation outlines the enforcement policy for PPE manufacturing during the current public health emergency and provides criteria for quality control standards as well as the required labeling of products released under the EUA. Thanks to this protocol there have been many recent instances of smaller companies and even individuals producing face masks and guards for healthcare workers.

Quality Control for PPE

A myriad of testing standards exists across ASTM, ISO, and industry-specific testing organizations that address PPE. Mechanical testing accounts for only a small percentage of the quantitative analysis of these products. Examples of other measurements include permeability, durability, and aging properties. Especially now, when each new gown or set of gloves is absolutely critical, it is vital that manufacturers perform failure analysis in order to reduce the risk of compromised equipment being released into the field. Fortunately, most companies pivoting their factories to produce PPE are already in possession of universal testing systems, which can easily be adapted to perform PPE testing through the addition of different grips or fixtures. This article looks at some of the most commonly evaluated products and their testing requirements.

Standard disposable medical face mask (left) and N95 respirator style face mask (right).

Gloves

The category of medical gloves has many different subsets, with materials varying from latex to nitrile, natural rubber, PVC, or polychloroprene. Medical gloves can be also be classified depending on their application: gloves used solely for patient examination, for example, have less-stringent requirements than gloves used in surgical environments. To add to the confusion, each testing body organizes their classifications differently, with ASTM providing different specifications based on the material and ISO differentiating them based on their application. Regardless of the testing standard, the equipment and general procedure for testing is consistent across all glove types.

The key results for all glove testing standards are the tensile strength and ultimate elongation of the material. Rather than testing the entire glove, a dog bone specimen is cut from the finished glove and tested in accordance with the related ASTM or ISO elastomeric standard (ASTM D412 and ISO 37, respectively). Medical glove specimens are much thinner than typical elastomeric specimens and require a gripping solution sensitive enough to prevent premature failures. Pneumatic grips are ideal for achieving maximum repeatability while being adaptable enough for the user to experiment with different clamping forces. To prevent jaw breaks, the surface of the jaw faces should be smooth, flat, or rubber coated and be free of any abrasive texture.

Strain measurement devices are not required for medical glove tests but are often used anyway to improve the accuracy of the elongation measurements. The fragility of the specimens calls for an optical strain measurement solution, as the knife edges on contacting devices may cause damage. Glove specimens are tested both directly off the production line and after undergoing accelerated aging conditions, which differ depending on the standard.

EN 455-2 is one of the most commonly used standards, adopted by some of the largest glove manufacturers in the world. It differs from the ASTM and ISO standards in that EN 455-2 compensates for the potential variation in thickness at different points on the glove. In this standard, the dumbbell specimen is always punched from the palm section of the glove, which has a uniform thickness. Depending on manufacturing methods, the fingertips may have a reduced thickness, altering the tensile strength values. This difference, while seemingly small, can catch potential failures before they leave the factory. It is worth mentioning that in today’s climate there have been fewer companies adapting to glove manufacturing than to other forms of PPE, as it requires highly specialized and expensive equipment.

Textile tensile test performed in accordance with ASTM D5034. This test is used to evaluate the material for both face masks and hospital gowns.

Masks

While wearing cloth masks has become commonplace in daily life, within hospital settings medical-grade masks are still the front line of defense against COVID-19. Medical masks come in two primary types: single-use surgical/medical masks and respirator masks. Single-use masks are routinely used by medical workers not actively in a COVID ward, while the respirator masks are intended for front line workers in direct contact with the virus. Many textile manufacturers have shifted production to single-use masks in an attempt to supplement the demand, using their existing equipment with minor additional changes. In many instances, their existing textile testing equipment can be used to evaluate the properties of these masks.

When testing surgical masks, three main components are evaluated: the tensile strength and elongation of the fabric, the strength of the connection of the elastic band to the mask, and the strength of the elastic band. The fabric is generally tested in accordance with ASTM D5034, a common textile tensile standard. Fabric samples can be tricky to grip without causing failures at or near the jaw face: unlike other materials fabric samples have no reduced section, and the stress concentration will almost always occur at the clamping point. Pneumatic grips and smooth jaw faces provide sufficient clamping force to prevent slippage and allow the failure to occur within the gauge length. The connection point of the mask and the elastic band is evaluated by loading it to a minimum of 10 N and visually checking that there is no separation. The 10 N value represents the approximate maximum force that the elastic band will experience when the mask is being worn. Considering that masks are being worn for longer periods of time than in the past, a relaxation test can also provide valuable insight into the durability of the elastic band. By holding a constant displacement on the band and measuring the decrease in force, a qualitative assessment of its ability to maintain sufficient tension over time can be obtained.

Respirator masks require all of the same tests as single-use medical/surgical masks with one exception. An additional test is required to evaluate the minimum force needed to separate the respirator valve from the mask face. This step is important as a quality control check and can be accomplished by using a standard side-acting grip on the base of the system and a custom-made hook fixture attached to the load cell. The pin and clevis modular design of a universal test system makes swapping fixturing simple and quick to do.

Expanding Capacity

This global health emergency is likely to continue for some time, and the need for PPE will only continue growing as the industry increases its abilities to test for the virus. Along with facilities increasing production and working multiple shifts, increasing the throughput and efficiency of quality control testing machines will be critical for keeping us ahead of the curve. Fortunately there are many different ways to improve throughput in the short term, ranging from barcode scanner integration to automatic specimen measurement devices and sophisticated software workflows.

Manual data input is one of the main bottlenecks in the testing process, requiring intense focus from the test operator to correctly enter batch information, specimen tags, and test parameters. The use of barcode scanners streamlines the entire process, reducing the chance of errors. Automatic specimen measurement devices (ASMDs) allow the operator to integrate their caliper or micrometer with the system, automatically pushing the dimensions to the software and eliminating the need enter them manually. Finally and most importantly, the software uses visual indicators to help operators quickly identify batch quality issues before it can result in stop shipments, lost revenue, or inadequate PPE being released into the market.

As the global community comes together to fight COVID-19, corporations are setting business aside to produce PPE as a public service. As more and more industries begin shifting production, the need for accurate and efficient quality control testing will be paramount. Any company embarking on this endeavor should seek guidance from the FDA or recognized product experts to create an effective quality control program. As a major part of this program, properly optimized universal test machines will empower manufacturers to feel confident that their products will perform as intended when they reach the front lines.

This article was written by Landon Goldfarb, Senior Applications Engineer at Instron, Norwood, MA. He can be reached at This email address is being protected from spambots. You need JavaScript enabled to view it.. For more information, visit here .


Medical Design Briefs Magazine

This article first appeared in the September, 2020 issue of Medical Design Briefs Magazine.

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