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All of us at SMTL are delighted to hear that Dr Steve Thomas,  Director of the Surgical Materials Testing Laboratory (SMTL) from 1989 until 2005, has been awarded an OBE (Officer of the Order of the British Empire) for services to the NHS in the 2018 Queen\'s Birthday Honours.

Steve studied pharmacy at Cardiff University followed by a PhD on gluteraldehyde.   His initial post in the NHS was as QC Pharmacist for Mid Glamorgan Health Authority, where he started in 1970. As the laboratory grew Steve developed an interest in wound dressings and medical devices, and his expertise was recognised by the Welsh Office who appointed him as the Surgical Dressings QA Pharmacist for Wales.  When the laboratory moved from East Glamorgan Hospital to Bridgend General Hospital in 1989, Steve became the first Director of SMTL.

Steve is recognised internationally as a world expert on woundcare products, establishing the first NHS medical device and dressings testing lab in the UK for the Wesh Office. He has written over 150 papers and articles on surgical dressings, bandages and maggots and set up the first European sterile production centre for maggots used for wound debridement, reintroducing maggot debridement therapy to Europe, and turned this into a commercial venture which was spun off by the NHS as Zoobiotics in 2005 when Steve left the NHS.

As Director of the Welsh NHS Surgical Materials Testing Laboratory (SMTL) he developed it into an internationally recognised leading centre for its work in on medical devices and surgical dressings. Steve was editorial advisor to the British National Formulary (BNF), founder member of the editorial board of the Journal of Wound Care, Senior editorial advisor to World Wide Wounds and editor of the Formulary of Wound Management Products. He developed the first performance-based test methods for modern wound- care products, which were adopted by the British Pharmacopoeia and the European Standards organisation CEN, as well as the test method used for over 30 years for bandages.

He was long term member of Committee L of the British Pharmacopoeia, editorial advisor to MIMs as well as a member of multiple BSI and CEN standards committees. He was a twice winner of the Nicholas Award (Guild of Hospital Pharmacists), and in 2001 gained the Queen’s Award for Innovation for the LarvE project. In 2002 he was joint winner of the William Hunting Award (British Veterinary Association), again for his work with maggot therapy.

After leaving Zoobiotics in 2007, he set up a medical device consultancy, Medetec, which continues to provide expert advice and consultancy to the dressings industry and the NHS in Wales. He published a number of recent papers on the effects of humidity on dressing performance and measurement of sub-garment pressure, which lead to the development of an apparatus used in the Welsh NHS as part of their evidence-based procurement programme, and which is under consideration for adoption as a UK standard.

Steve continues to be relied on for advice to European Working Groups on dressings test methods, for indusry as an expert witness in legal cases, and has recently been commissioned by NHS Wales to produce Health Technology Assessments. He is the author of several patents related to dressings and maggot production and distribution. His 2010 book on “Surgical Dressings & Wound Management” is considered internationally to be the standard reference on dressings.

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SMTL are able to test the following characteristics of skin barriers for ostomy aids to BS ISO 12505-1:2014 - Skin barrier for ostomy aids - Test Methods. Part 1: Size, surface pH and water absorbency.

 

Water Absorbency

In this test, the sample under test is sectioned and applied to the base of the test cylinder. Saline solution is introduced into the cylinder and parafilm applied to form a closed system. The cylinder is pre-weighed and then incubated at 37°C. Following 6 hours incubation, the parafilm is removed and remnant fluid drained from the cylinder. The cylinder is then re-weighed to calculate the mass of fluid absorbed by the sample.

 

Surface pH

In this test, the sample under test is sectioned and fixed to the bottom of the petri dish. Saline solution is introduced into the petri dish until 1cm above the height of the sample. The petri dish is then incubated at 37°C. Following 4 hours incubation, the surface pH at the centre of the sample is measured.

 

If you wish to commission testing of your skin barrier, then contact the SMTL:

Surgical Materials Testing Laboratory, Princess of Wales Hospital, Coity Road, Bridgend, UK, CF31 1RQ.

Tel: +44 (0) 1656 752820
Email: smtl.physical@wales.nhs.uk

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In July 2021, the NHS PPE Decision Making Committee approved the newly drafted specification for Thumb Loop Gowns  (PDF Download).

The specification states:

Introduction

This specification is intended to provide performance requirements for thumb loop aprons which exhibit sufficient mechanical properties, resistance to microbiological challenge, and resistance to chemical/liquid penetration for standard clinical use by healthcare staff. It is based on the “Essential technical requirements for new High-Volume Manufacture of Personal Protective Equipment (PPE) and Medical Devices (MD) during COVID-19” with additional microbiological and chemical penetration requirements taken from British Standards used for protective clothing. The terms thumb looped aprons and gowns are used interchangeably. In this document no distinction is made between these terms. 

Scope

This document specifies design and performance requirements for fluid-resistant single-use Thumb Looped Aprons, also known as Thumb Looped Gowns, intended to provide fluid and splash protection for healthcare workers when undertaking healthcare procedures. This specification specifically excludes surgical and medical gowns. Thumb loop aprons are single transient use items, worn by healthcare workers for single episodes of care or other tasks in a healthcare environment. They may be used in situations where exposure to splashes, droplets and fluids containing infectious agents or chemicals is likely, such as endoscopy. Thumb looped aprons may also be used to protect medical or surgical gowns in the clinical environment. Thumb looped aprons are not intended for use in environments where they will be exposed to heat, sharp objects or significant mechanical stress.

The specification is available as a PDF download.

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Certain types of chronic wounds such as leg ulcers, diabetic foot ulcers and fungating lesions are often associated with wound malodour, which can cause both socially and psychologically distress for the patient and their family [1]. The smell from these wounds is associated with excess exudate production, presence of necrotic tissue and the release of volatile agents from infecting microorganisms [2].

The most effective way of dealing with malodorous wounds is to prevent or eradicate the infection by cleansing and debriding the wound (surgical and biological larval therapy) and treating the underlying infection using antibiotics (systemic or topical) and antimicrobial agents (such as honey and silver)  [3].  These treatments are often supplemented by using specialist odour-adsorbing dressings that are designed to retain the volatile molecules released from the wound.

Deodourising wound dressings have been used for many years, however despite their widespread use, there is little objective data on their odour handling characteristics. The European standard EN 13726-6:2003 [4] details a test method designed to assess the resistance of primary wound dressings to penetration by odours.  The test method only applies to dressings of a design where the odour absorbing material is not penetrated by exudate. As the wound dressings are tested in a dry state, this does not simulate clinical use and is inadequate for ascertaining a realistic evaluation.

In 1998 Thomas et al. [2] devised an in vitro test method where both odour-adsorption and fluid-handling capacity are assessed together, and thus more realistically simulates the conditions of normal clinical usage. Over recent years the SMTL have refined and developed this method to produce a validated test method that determines the ability of wound dressings to absorb exudate and control odour in the wet state.

In this test, the wound dressing under test is placed over a stainless steel plate with a recess (16.6 cm² wound area) and covered with an airtight perspex chamber. A 50ml syringe attached to a syringe driver is filled with a volatile/malodorous test solution (2% diethylamine solution) which is infused onto the dressing at a rate of 30ml/hour. A calibrated photo-ionisation gas detector placed immediately above the wound dressings continually monitors the concentration of diethylamine in the chamber (1 second intervals), and the test continues until the concentration of 15 parts per million (ppm) is detected  (Figure 1).  The volume of test solution applied to the wound dressing when the concentration of diethylamine in the chamber reaches 15 ppm is then calculated.  The higher the volume of the test solution, the better wound dressing’s odour-adsorbing properties.

Figure 1 - Example Odour Adsorption Results

  

The studies listed in Table 1 show that exudate production rates vary depending on wound type. For example, if an average exudate rate of 0.5 ml/cm²/24 hours was used, then a wound with an area of 10 cm² could therefore be expected to produce approximately 5 ml of exudate in 24 hours (0.21 ml per hour).

Based on the results of the test, an estimate of the degree of odour control can be calculated. For example, if the mean volume of test fluid applied to the dressing was 15ml, the dressing could be expected to provide a degree of odour control for approximately 72 hours.

It is important to note however, that the rate at which the test solution is applied during the test is 30 ml per hour (43.4 ml/cm²/24 hours) and this value is considerably in excess of that encountered clinically.

 

Table 1 - Reported Exudate Rates per Wound Type
Wound Type Method of exudate production measurement Paper Reference Rate of exudate production (g/cm²/24 hours)
Leg ulcers Dressing weight 5 0.17 - 0.21
Leg ulcers Dressing weight 6 0.43 - 0.63
Various Negative pressure wound therapy canister collection 5 1.3*
Granulating wounds Vapour pressure gradient (evaporative water loss) 7 0.51
Skin donor sites Vapour pressure gradient (evaporative water loss) 7 0.42
Partial-thickness burns Evaporimeter 8 0.42 - 0.86
Partial-thickness burns Vapour pressure gradient (evaporative water loss) 7 0.43
Full-thickness burns Vapour pressure gradient (evaporative water loss) 7 0.34

Note:

*Units: ml/cm2/24 hours

 

1. Benbow, M (1999) Malodorous wounds: how to improve quality of life. Community Nurse 5(1): 43-46

2. Thomas S, Fisher B, Fram P, Waring M (1998) Odour Absorbing Dressings: A comparative laboratory study. J Wound Care  7(5): 246-250.

3. Lee G, Anand S C,Rajendran S, Walker I (2006) Overview of current practice and future trends in the evaluation of dressings for malodorous wounds. J Wound Care 15(8): 344-346

4. EN 13726-6 Non-active medical devices - Test methods for primary wound dressing - Part 6: Odour control

5. Dealey C, Cameron J, Arrowsmith M (2006) A study comparing two objective methods of quantifying the production of wound exudate. J Wound Care 15(4): 149–53

6. Thomas S, Fear M, Humphreys J et al (1996) The effect of dressings on the production of exudate from venous leg ulcers. Wounds: Compendium Clin Res Prac 8(5): 145–50

7. Lamke LO, Nilsson GE, Reithner HL (1977) The evaporative water loss from burns and water permeability of grafts and artificial membranes used in the treatment of burns. Burns 3: 15965

8. Ferguson GC, Martin CJ, Rayner C (1991) Burn wound evaporation measurement of body fluid loss by probe evaporimeter and weight change. Clin Phys Physiol Meas 12(2): 143–56

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The Neuraxial connectors FAQ has been updated after discussions within the WNCRG (Welsh Non-Luer Connectors Reference group). This version is bespoke to the Welsh NHS.

The document is based on an original FAQ coordinated by Rory Jaffe at CHPSO (California Hospital Patient Safety Organization) and GEDSA (Global Enteral Device Supplier Association) including contributions from a number of UK experts.

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