SMTL Newsletter, Volume 1, Issue 4, November 1999.

Dressing for the millennium...

The Surgical Materials Testing Laboratory is proud to announce a wound-management conference in 2000 that everyone can afford to attend.

In June of the year 2000, a major wound management conference will take place in the prestigious Cardiff International Arena (CIA) to celebrate the Millennium. This important event will be organised jointly by the SMTL and leading manufacturers of healthcare supplies in the United Kingdom.

We hope that this unique event will attract around 1000 delegates, making it one of the largest events of its kind.

An affordable wound management conference ....

Most large wound management conferences are organised on a commercial basis with registration fees well into three figures. As a result they tend to attract specialist tissue viability nurses and other delegates who are regarded as `experts' in the field. It is often the case that nursing staff who spend a great deal of time dealing with wounds as part of their daily routine are unable to obtain sufficient funding to attend these important meetings.

The aim of the Cardiff conference, provisionally entitled ``Dressing for the Millennium'', is to provide these wound care practitioners with an opportunity to attend a major meeting at very low cost. The cost will be £56.40 (inclusive of VAT) for the two days, to include lunch, refreshments and conference dinner if booked before 31st December 1999, and £64.62 thereafter. Accommodation packages are available for £131.95 (before 31st Dec) for 2 nights with en-suite, including conference fees, lunch, dinner etc.

If you would like more information, see the SMTL web site

S. Thomas

Reusable gowns/drapes and Laundries/CSSD

Recently there has been much discussion over linen, disposable and reusable gowns and drapes. The article discusses some of the standards that are being developed in this field, and hope to clear up some of the myths being perpetuated by a number of manufacturers.

Recently there has been much discussion over linen, disposable and reusable gowns and drapes. The article discusses some of the standards that are being developed in this field, and hope to clear up some of the myths being perpetuated by a number of manufacturers.

Standard Developments

Presently, a European standard is being prepared by CEN/TC 205/WG 14, which is intended to provide standard methods of test for gowns and drapes, and will ultimately set limits for different classes of product. However, this standard will not be published until sometime in the year 2000.

In parallel with this standard, the EU have funded a project called BIOBAR, intended to develop Biological Barrier test methods for protective clothing. This project is set to report by December 1999,

Although compliance with standards is not mandatory, it is expected that most gown and drape manufacturers (disposable and non-disposable) will wish to adhere to it. Purchasers are also likely to request compliance with the standard in tender exercises.


There are presently rumours that linen is about to be outlawed due to the imminent publication of the above standard. It should be noted that there are no plans to produce legislation banning linen products. Purchasers will be able to continue buying linen if that is what Trusts and users want. If a manufacturer of linen gowns/drapes does not make any claims for the items in terms of barrier properties or reduction in cross infection, then they can continue to sell them without them being CE marked, as they will not be classed as medical devices.

It is possible, however, that clinical governance will play a significant part in this debate - if there is a consensus that the protection given by disposable/reusable gowns and drapes is clinically important, then Trusts may be forced to abandon linen and balloon cloth products.

The MDA are supposed to be putting a position paper together on this matter.

Performance Requirements

The proposed CEN standard will cover a range of tests, although the final tests and the test limits are still to be agreed. The table below outlines the main parameters which are being considered for the standard.

Direct Wet Contact BIOBAR/ASTM 1670 and 1671 Test using synthetic blood and bacteriophage. Probably not being included in the standard.
Direct Dry Contact Swedish moving finger method Rotate a teflon finger over a contaminated sheet, and see if the organisms penetrate through the material to the agar plate below.
Wet Aerosol BTTG developed method Probably not being included in the standard.
Dry Aerosol Spore contaminated talc  
Microbial Cleanliness EN 1174-2 - test for bioburden. Remove organisms by stomaching etc, grow in/on media.
Cleanliness from Foreign matter EN 1644-1 Test for water soluble extractives. Test still under discussion.
Particulate matter - Linting Gelbo flex test (> 3 microns) Measures dry linting, but question regarding the size range and reproducibility.
Burst Strength (wet & dry) ISO 13938-1 Measure the pressure required to burst a sample placed over a rubber diaphragm.
Tensile Strength (wet & dry) EN 29073-3 Measure the force required to pull apart a section of material.
Resistance to liquid penetration EN 20811 Hydrostatic pressure test. Increase the pressure in a chamber until visible drops are seen on the material.
Liquid Control prEN 1644-2 Possibly informative only, as not able to test fluid control pouches.
Fixation EN 1939 Peel adhesion test. Doesn't mimic adhesive/skin fixation.
Tear Strength EN ISO 29073-4 Trapeziod tear test - make a slit in a sample of material, and measure the force to tear the sample.


Trusts which are interested in moving to reusable or disposable gowns and drapes are finding it difficult to compare the various products in terms of the total cost to the Trust and in terms of their performance.

To help in their deliberations, SMTL, Welsh Health Supplies and the Gown and Drape sub-group are producing a document whose aim is to:

1. Highlight important parameters of gowns and drapes.
2. Discuss the various methods of testing these parameters, and the limits that should be applied.
3. Outline a methodology that a Trust could use to compare linen, disposable and reusable gowns and drapes.

It is hoped that the document will be complete by Spring/Summer 2000. In the meantime, if you are interested in this field and would like a draft copy to comment on, please contact me at the address on the back page.

P. Phillip

Papers and Circulars

Latex Sensitisation

Health Service Circular HSC 1999/186, published in September 1999, is meant to draw the attention of Chief Executives to the Health and Safety issues associated with latex sensitisation.

The circular states that the Heath and Safety Executive (HSE) intend to issue guidance on the care that needs to be taken with the use of latex products later on in the year, but in the interim they ask NHS managers to take all necessary precautions to protect patients and staff.

The three main points raised are:

1. Latex glove users should be reminded of the guidance issued by the medical Devices Agency (MDA DB 9601 and MDA SN 9825).
2. Local policies should be in place which address the purchase and use of medical gloves, including circumstances in which powdered gloves may be used, should be in place.
3. Individuals who are latex sensitive should stop using latex gloves, be provided with alternatives and avoid areas where latex glove powder may be airborne.

The full text is available on the Internet at (do a search for latex AND gloves).

SMTL has produced a draft policy in association with the Bridgend and District NHS Trust. If you would like a copy for your Trust to use as a starting document for your own policy, please contact SMTL to request one.

Decontamination of Medical Devices

Health Service Circular HSC 1999/179 (August 1999) deals with the importance of implementing existing guidance on the cleaning and sterilization of medical devices. It will be vital to anyone concerned with reprocessing medical devices (such as surgical instruments).

The key points are:

  • Use the guidance CDROM on ``Decontamination Guidance''.
  • Validate washer disinfectors using HTM 2030.
  • Validate and manage sterilization equipment using HTM 2010.
  • Never re-use medical devices designated for single use.

It appears that concerns regarding variant Creutzfeldt-Jakob Disease (vCJD) has stimulated this circular, especially the fact that experts have stated that effective cleaning of surgical instruments prior to sterilization is of utmost importance in reducing the risk of transmission of vCJD via surgical procedures.

The full text is available on the Internet at (do a search for decontamination AND medical AND devices).

Latex allergy and anaesthetics.

A useful paper was published in Anaesthesia last year (Anaesthesia, 1998, 53, 774-781) by Dakin and Yentis, which outlines the strategy they followed to identify and safely manage those at risk in the peri-operative period, and facilitate the process for other departments.

The authors noted that only a small number of anaesthetists had recognised the potential severity of latex allergy, and that many would not recognise it as a potential factor in anaphylactic shock.

The paper includes a very useful section on identifying high risk groups, including questioning, patient history and immunological testing, although they do acknowledge that the risk of false negatives means that immunological testing is not foolproof.

A protocol is included in the paper, which covers:

  • the importance of identifying ``at risk groups'',
  • perioperative care (including premedication with antihistamines and steroids),
  • use of a ``latex free box'',
  • the importance of latex free gloves
  • the issue of drugs and latex free syringes

Figure 2 in the paper lists the authors' database of latex free equipment (gloves, airways, IV, regional/nerve, monitoring), latex-containing items not to be used, and latex containing equipment which can be used with modification.

Training of staff, especially new doctors,was considered essential, and they have addressed this through the wide availability of the protocol, education of OR staff, ward staff, and raising the issue on induction days for trainee doctors. They also reinforce this as trainees rotate into the department.

A followup letter from Armstrong and Barr (Anaesthesia, 1998, 53, 1228-1237) supports the paper, but cautions against storing drugs in latex-containing syringes for an extended period of time.

Overall, this paper provides an excellent starting point for developing a latex allergy protocol for anaesthetic and surgical departments, and is recommended reading for anyone developing a latex allergy policy.

P. Phillips

The Clinical significance of DVT and the use of compression hosiery.

Deep venous thrombosis and pulmonary embolism are a significant cause of morbidity and mortality in hospitalised patients the long term effects and cost of which have yet to be fully determined. Treatment of both conditions is expensive and effective prophylaxis is to be preferred

The application of static compression to the leg by means of elasticated compression hosiery has been shown to be an effective form of prophylaxis, reducing, but not eliminating, the incidence of both DVT and PE. In common with all other forms of prophylaxis, stockings are not 100% effective and a significant proportion of patients who wear them still develop a thrombosis. Below knee stockings appear to be as effective as thigh length stockings but further studies are necessary to confirm this finding.

Pneumatic compression devices appear to offer few advantages over stockings for the prevention of DVT. Clinical research has demonstrated that the application of external compression to the leg of a supine subject will tend to increase blood flow velocity in the leg and thus reduce stasis. It may also help to prevent damage to blood vessels caused by excessive distension, a further possible contributory factor to DVT formation.

The principal benefits of anti-embolism stockings appear to be that they reduce the size of the soleal sinuses in the calf area, reducing stasis. The optimum compression profile required remains uncertain but the evidence suggests that calf pressures in the order of 14-15 mmHg at the calf with a slightly higher pressure at the ankle may be more effective than the 18-14-8-10-8 profile originally proposed. Higher values than this may increase blood flow in some patients but may have the reverse effect in others. The major benefits to be derived from the use of external compression will be experienced by patients confined to bed. The evidence strongly suggests that stockings used to prevent thromboembolisms have insufficient elasticity to function adequately when a patient is ambulant or sitting with legs dependent.

The pressure profiles produced by six leading brands of stocking were examined in a recent laboratory-based study. Overall, three brands produced by Medi UK, Credenhill and Seton performed reasonably well across the range of sizes tested. Pressure values at the ankle and calf were close to those recommended in the literature and good graduation was achieved in most cases.

Stockings produced by Kendall and Parema produced pressures which were sometimes substantially lower than those produced by the first three manufacturers. It was also noted that there was a significant degree of variability in the pressure produced by the different sizes in the case of the Kendall product. Some small reverse pressure gradients were also noted with this stocking.

The pressure produced by the BDF stocking were very variable across the range of sizes examined and some significant reversed pressure gradients were also detected.

The results of the laboratory study clearly indicate that stockings vary in performance and some produce levels of compressions, which are not consistent with the values originally shown to have an optimum effect upon blood flow. In some instance reverse pressure gradients are produced which may have important implications for the ability of the stocking to function effectively. These differences in performance can occur within the range of stockings provided by a single manufacturer and this may be one explanation why these items sometimes fail to prevent DVT formation.

Anti-embolism stockings may cause ulceration or skin damage in some vulnerable patients or if incorrectly applied and their use should be carefully monitored.

A report summarising this study will soon be available from SMTL.


American Maggots meet Welsh maggots !

On Monday the 11th October 1999, The Missoula All-Maggots Rugby Club visited SMTL at the Princess of Wales Hospital, Bridgend.

Earlier in the year, SMTL discovered the existence of the ``Missoula All-Maggots Rugby Club'' from their Internet site ( The ``Maggots'' (club motto: ``A Maggot squirms through it!'') were coming to Wales for the World Cup, and it seemed too good an opportunity to miss - an invitation was extended for them to visit their Welsh counterparts in Bridgend. As their Web site said:

``Wahoo! We've been invited to visit a Maggot breeding facility during the tour! Lookout for news nine months after the tour on results of our ongoing quest for improving the Maggot rugby breed!''

The touring party (35 maggots and maggettes) were welcomed to SMTL by Mr JPR Williams (Orthopaedic Consultant at Princess of Wales hospital, Team Manager for Bridgend RFC, and ex Wales and British Lion full back).

The ``Maggots'' (given their name by some Canadians, who referred to the new team as ``that bunch of maggots from Montana''), were presented with a specially commissioned cartoon as a memento of their visit to SMTL.

P. Phillips

The Medical
Disposables and
Dressings Newsletter
Vol. 1 No. 4
November 1999
Published by:
The Surgical Materials
Testing Laboratory
Edited by:
Dr Stephen Thomas
Email: This email address is being protected from spambots. You need JavaScript enabled to view it.
Peter Phillips
Email: This email address is being protected from spambots. You need JavaScript enabled to view it.


Contact Information
Tel: 01656-752820
Fax: 01656-752830
Princess of Wales Hospital
Coity Road
CF31 1RQ
©1999 by SMTL.
All rights reserved. No permission necessary to copy, reprint and distribute unaltered within the NHS as required.
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