NWT medical drapes and gowns: materials and standards

Dental and medical drapes and gowns are essential for providing proper protection. For this reason, understanding the differences between existing available products is useful, so that you are familiar with the materials used and aware of the relevant standards. This will help you to avoid purchasing and using ineffective, non-standard solutions.

The acronym NWT (non-woven tissue) refers to a group of products similar to standard fabric but made in a very different way to weaving. To make NWTs, fibres are bonded or interlocked mechanically (the fibres are entangled), chemically (the fibres are bonded together chemically with glue-like compounds) or thermally (low-melt fibres are melted with one another).

Nowadays, these fabrics are the standard in medical environments thanks to their effectiveness as a bacteriological barrier, their light weight and the fact that they have no shape memory, meaning that they do not crease or crumple.

In particular, NWTs used in medical environments must be impermeable to liquids and, for fabrics used to make protective clothing (gowns, caps, etc.), they must also be highly breathable, to avoid the “sauna” effect. There are two essential parameters that will tell you how effective a NWT garment is:

•     BFE, meaning Bacterial Filtration Efficiency;
•     Delta P (pressure differential), which measures breathability.

NWTs can be bonded with other materials to ensure certain technical characteristics. In the medical field, materials bonded together include:

• Absorbent NWT and polythene (NWT/PE): here, the resulting material is absorbent on one side and waterproof on the other. Double-sided drapes and clothing made from this material can be sterilized with ethylene oxide.
• Absorbent NWT and polypropylene (NWT/PP): this double-sided material has the same characteristics as the previous one but can be sterilized in an autoclave.

NWT can be made from different materials. In the medical field, the most common and prominent are made from polypropylene (PP) and polyester (PE). The two most common spinning processes are the “Spunbond” and “Meltblown” methods.

Spunbond fabrics have thicker fibres compared to Meltblown fabrics, and are stronger and more robust. Spunbond NWTs are cheap, light and robust, but less suitable for fine filtration.

Meltblown NWTs have long and very thin fibres, creating a fabric that, while not very strong, is more efficient in terms of filtration.

SMS is a tri-laminate NWT. It is made up of a top layer of spunbond polypropylene, a middle layer of meltblown polypropylene and a bottom layer of spunbond polypropylene. The main advantage of this type of NWT is that it is very resistant while providing a strong barrier against fluids and particles.

Among the barrier fabrics used to make drapes and gowns is Reusable Technical Fabric (RTF). This is a basic fabric made from polyester bonded with carbon fibre. Thanks to its particular structure, this material is breathable, water-repellent and waterproof.

These fabrics are made to withstand 60-80 WDA (Washing, Drying, Autoclave) cycles:

• Washing at 75°C (Washer extractor);
• Drying (Tumbler / 80°C);
• Sterilization (134°C / 4 min).

The EN 14683 European standard outlines specific requirements for surgical masks. Standard EN 149 details requirements for respiratory protective devices (face masks). This article goes into depth about both of these standards and how they correspond to American standards (ASTM F2100 and NIOSH).

Here, we will discuss EN 13795, a standard that outlines requirements for surgical clothing and drapes. With regard to surgical drapes and gowns, used as protective equipment for patients, clinical staff and appliances, standards EN 13795-1 (general requirements for manufacturers, operators and products), EN 13795-2 (test methods) and EN 13795-3 (performance requirements and performance levels) are currently in force in EU countries. Two additional technical standards have been approved to support and supplement EN 13795. These are EN ISO 22610 and EN ISO 22612, which specify how resistance to bacterial penetration—in both wet and dry states—is measured. This is a fundamental aspect because drapes and gowns must, among other things, act as a barrier to bacteria-ridden skin particles, both in wet and dry conditions.

Drapes and gowns must therefore comply with standard EN 13795, which ensures that a wide range of criteria have been evaluated, including:

•     cleanliness (microbial/bioburden);
•     particle release;
•     resistance to liquid penetration;
•     bursting strength in wet and dry states;
•     tensile strength in wet and dry states;
•     liquid barrier;
•     resistance to microbial penetration in a dry state;
•     resistance to microbial penetration in a wet state.

This standard applies to both NWTs and RTFs. EN 14126 tests are carried out again if a gown is disposable. If it is reusable (i.e. made from RTF), the tests need to be performed after the maximum number of washes detailed on the label (e.g. 5 cycles) have been carried out, and variations in fabric dimensions have to be factored in as well (in this case, any time needed to complete the washing cycles must be added).

In principle, a gown can be considered either a MD (Medical Device) or a type of PPE (Personal Protective Equipment) depending on its intended use (or function). If it is used to protect an operator, it is considered PPE. If, however, it is used to prevent cross-contamination, it is deemed an MD. Depending on the intended use defined by the manufacturer, the certification and testing of the product adhere to the specific requirements of the relevant standard (for MDs or PPE). One product can satisfy both sets of requirements but the manufacturer must ascertain what its primary purpose is. The answer will determine what type it is. This does not mean that a gown classed as an MD does not protect operators, it simply means that the manufacturer has designed it to be used as an MD and not PPE.

As we have seen, with many products available on the market, choosing the right ones is very important. Quality, comfort, effectiveness, and means of use are all important aspects that we need to consider in order to select the right products. With these in mind however, we must still ensure that products comply with existing regulations and any updates to them.

At Euronda, we believe that the first step in ensuring that everybody is kept safe is providing correct information and making you aware of any issues involved; we hope that this article has been of use to you.