Wound Dressings
SMTL is recognised as a centre of excellence for the research, development and testing of wound dressings.
SMTL were responsible for reintroducing maggot therapy into Europe and established the first NHS spin off company ZooBiotic (now trading as Biomonde) specifically to produce and sell sterile medical maggots for wound debridement.
The laboratory has been testing wound dressings for over 50 years and was involved in establishing the first functionality tests for dressings which were adopted as British Pharmacopoeia methodologies. These methodologies were latterly adopted as a series of parts of the European Standards BS EN 13726 Test Methods for Primary Wound Dressings. SMTL staff are actively involved in British and European standard committees to drive further innovation in this field.
We are UKAS accredited for the testing of wound dressings and currently offer testing to British Pharmacopoeia monographs, Europeans Standards and a number of in-house developed methodologies.
EN 13726 Test Methods
SMTL hold accreditation for testing to the European Standard EN 13726 which was published in 2023. EN 13726 contains test methods to assess important characteristics of wound dressings including absorption, moisture transmission, waterproofness, and extensibility. These methods are conducted in vitro and involve testing the dressing materials under different physical and chemical parameters.
- Annexes B and C - Free Swell Absorptive Capacity and Fluid Retention
- Annex D - Absorption Under Compression
- Annexes E, N and O - Fluid Handling Capacity | With gasket modification | With air expulsion
- Annex F - Fluid Donation of Amorphous Hydrogel Dressings
- Annex G - Dispersion Characteristics of Gelling Dressings
- Annex H and I - Moisture Vapor Transmission Rate | In Contact with Vapour | In Contact with Liquid
- Annex J - Waterproofness
- Annex K - Extensibility and Permanent set
In-House Developed and Other Methods
WRAP Dynamic Fluid Handling Capacity (FHC) Testing
Although standard BP and EN 13726 methods facilitate the comparison of FHC properties of similar products they do not permit comparisons between different groups of dressings.
Existing methods are also of limited value when assessing how a dressing is likely to perform in clinical practice.
To address these shortcoming SMTL have developed a Dynamic Fluid Handling Capacity test which was further refined with commercial partners during the Engineering and Physical Sciences Research Council (EPSRC) funded Woundcare Research for Appropriate Products (WRAP) project.
The apparatus was designed to mimic a clinical situation and therefore, basic predictions can be made about the likely wear time of dressings on different types of wounds. This quantitative method allows the measurements of absorbency and moisture vapour transmission with or without the application of pressure. It is the first method which can be used to compare the fluid handling properties of different families of wound dressings such as alginates, hydrocolloids, foams, sheet hydrogels and amorphous hydrogels.
SMTL have published extensively using this apparatus and continue to offer this testing for commercial clients.
If you have products you wish to have tested, or any questions related to this method please contact smtl.info@wales.nhs.uk
References
- Thomas S, Fram P. The development of a novel technique for predicting the exudate handling properties of modern wound dressings; J of Tissue Viability vol 11 number 4 Oct 2001; 1415-160
- Rajendran S. Advanced Textiles for Wound Care ; Second Edition; 2019
- Thomas S. Surgical Dressings and Wound Management; 2010
Odour Absorption
Deodourising wound dressings have been used for many years. Despite their widespread use, there is little objective data on their odour handling characteristics. The withdrawn European standard EN 13726-6:2003 detailed a test method designed to assess the resistance of primary wound dressings to penetration by odours. However, there are limitations with this method as few laboratories have the necessary apparatus to perform the testing. In addition, wound dressings are assessed in their dry state, which does not simulate clinical use, and therefore raises questions on its adequacy for providing a realistic clinical evaluation.
In 1998, Thomas and colleagues published an in vitro test method where both odour-adsorption and fluid-handling capacity are assessed together, which more realistically simulates the conditions of normal clinical usage. Over recent years the SMTL have developed this test to produce a validated method that determines the ability of wound dressings to absorb exudate and control odour in the wet state.
Please contact us if you require any further information or wish to discuss undertaking an odour control testing project smtl.info@wales.nhs.uk
References
- Thomas S, Fisher B, Fram P, Waring M. Odour Absorbing Dressings: A comparative laboratory study; J Wound Care 7(5); 1998; 246-250.
X-Ray Opacity of Wound Dressings
Numerous incidents have been reported of absorbent devices left within patients following surgical interventions. Retained devices may remain in the body for extended periods and can result in serious clinical complications for the patient, often resulting in further secondary surgery to remove the device and associated legal proceedings against the healthcare provider.
The ability to observe and locate the remnant device within the patient is of great importance. For this reason, radiopaque markers are often incorporated within absorbent swabs to aid in identification on postoperative radiographs. However, the degree of radiopacity can vary between devices and in some cases the radiopacity marker may not be present or not securely bonded within the swab which can detach during use.
In conjunction with NHS Wales Radiology colleagues, SMTL can facilitate testing of x-ray detectable dressings to British Pharmacopoeia standards using 30mm thick 99% aluminium plates, and to ASTM requirements using body phantoms. Testing will be performed using imaging technologies which are commonly used in NHS Wales. If you wish to commission testing of your x-ray detectable dressings, then please contact SMTL smtl.info@wales.nhs.uk
Standards
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- British Pharmacopoeia 1993 Volume II – X-Ray Detectable Gauze Swab, Appendix XX R
- ASTM F640 – 20 Standard Test Methods for Determining Radiopacity for Medical Use
Biological Test Methods
